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Is there any part of a flight where the pilot would pitch down? Would the pilot ever pitch down (even slightly) during a flight, or would he/she simply reduce power to reduce altitude? This question is not similar to Why do airplanes lift up their nose to climb? (asked by Chris) for it the reasons aircraft pitch up. This question is looking for an answer that explains if and when a pilot pitches down during a flight to reduce altitude, the very opposite of the question of @Chris. <Q> The most common case to pitch down is to speed up, not to reduce altitude, for example when transitioning from a climb (at climb speed) to level flight (accelerating to cruise speed). <S> You can transition to level flight by reducing thrust, but that'll leave you level at climb speed, and is usually not what you want. <S> Changing configuration will usually require pitching changes to maintain stable flight. <S> If you don't, you'll bleed off airspeed and potentially eventually stall unless you overpower the drag with thrust. <S> There are of course unusual circumstances that will require a pitch-down as well, obstacle avoidance for example (e.g. airplanes). <S> As mentioned in the comments, to make a speedy descent you'll probably also want to pitch down (such as in case of pressurization problems or fire on board). <A> I'm going to interpret "normal" as cruise level of a commercial flight. <S> Normal for other types of flying might have different answers. <S> In level flight pitch is regularly adjusted both up and down to maintain the chosen altitude. <S> Generally these adjustments are small enough that they are not noticed by passengers or crew, especially with an autopilot engaged. <S> So is it very normal to pitch down in small increments without changing power settings. <S> With larger changes in pitch, for example when descending from cruise level, typically thrust is reduced or increased to maintain airspeed. <S> It would be unusual to pitch down before reducing power, or pitch up before increasing it. <A> To add a bit of historical background, the argument used to rage as to whether you should "control altitude with pitch and speed with power" or "control altitude with power and speed with pitch. <S> " I always felt (and still do, though I'm long retired) <S> that adhering to a hard line either way was a bit silly. <S> Obviously you can use either to change either, within limitations of course. <S> I don't know what current thinking is on the subject. <S> In the end it's a matter of energy management. <S> There used to be at least one special case where you would want to change both altitude and speed by using pitch alone for a bit. <S> On the 747-200 with certain engines, when starting a descent from high altitude (like the high 30s up to the max operating altitude), the recommendation was to start the descent by putting the nose down first and waiting until the airspeed started increasing before reducing power, thus avoiding the embarrassment of a possible high altitude flameout. <S> My guess is that with modern engines and FADEC, this kind of thing is no longer an issue. <A> Descending from Class A airspace on approach to an airport, a commercial airliner will, in my experience, often pitch down slightly. <S> It can be somewhat unnerving, especially as the engines will throttle down around the same time, but the nose-down is typically very shallow. <S> Whether a pilot continues to nose-down on final depends on the aircraft, the airport and the wind conditions. <S> It's often a practical requirement to nose down at the runway in a high crosswind landing, in order to minimize the sideways slip produced by the crosswind as well as to traverse the layer of air containing the crosswind as quickly as possible. <A> Whenever you track a reference in the vertical plane of your aircraft (nose to tail) it requires you to pitch up and down.
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In particular during the approach-to-landing, extending the flaps will substantially increase the drag, and in order to maintain airspeed, you'll need to pitch the nose down.
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Why is the aircraft boneyard in Tucson, Arizona still active? I understand that an aircraft boneyard is an amazing tourist attraction for aviation enthusiasts. However, the number of planes that the boneyard in Tucson has accumulated today is mind-boggling. I know that, initially, the purpose of the boneyard was to salvage materials from old and obsolete aircraft. However, the pace at which most aircraft are being scrapped is very low. Though it serves as a spectacular sight, why is the boneyard still active? <Q> If the number of planes waiting on getting gutted isn't decreasing even though scrapping activities are happening that means there is a steady influx of end-of-life planes arriving to get scrapped. <S> As long as there are planes and new planes being built (most have a lifespan of a few decades) there will be planes that need to get scrapped. <S> You can't just dump the plane on a landfill or you will get nature activists on your case about the hazardous materials (hydraulic fluid, remnant fuel, ...) and recycle potential. <S> Plus most components (instruments, engines, the espresso machine in the galley, etc) will still be usable and airliners will want to buy them as spares. <A> As ratchet freak noted , the boneyard is still active because planes are still being scrapped. <S> One reason specific to the AMARC in Tuscon is the B-52 aircraft still being scrapped for arms reduction treaties . <S> Planes may also be taken for use as targets, training aids, or even to be returned to service . <S> Typically controlling over 4,200 aircraft as well as many other types of military equipment, AMARG works very hard in promoting itself as not just a 'Boneyard' and takes every opportunity in explaining how it operates its cost effective, tax saving operations. <S> Many of the stored aircraft can be returned to an operational status in a short period of time and there is a continual process of anti-corrosion and re-preservation work which keeps the aircraft in a stable condition during their stay. <S> So the purpose is not just to scrap planes, but also for storage and reuse. <S> It's not even necessarily just for old planes; it's been used to store brand new planes until a use is found for them . <A> To tack on to @fooot's answer as far as aircraft reuse is concerned, AMARG also prepares aircraft for potential foreign military sales . <S> From an FAA circular : <S> The U.S. military normally retires aircraft to Davis-Monthan Air Force Base in Tucson, Arizona to be stored indefinitely, cannibalized, scrapped, or restored to service at a later date. <S> Surplus U.S. military aircraft are generally not sold directly to private U.S. operators without congressional approval. <S> However, U.S. military aircraft may be exported via foreign military sales programs or other agreements . <S> (emphasis mine) <S> This C-130 lived there for three years prior to being sold to Botswana. <S> Interestingly enough, many aircraft stored there are actually in better and more modern condition than the state in which the US Air Force flew them. <S> I knew a civilian assigned there who was the back seat test pilot for F-4 s after they received the necessary avionics upgrades in order to be attractive to foreign governments.
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Even if it just seems like the planes are sitting there idle, the boneyard also serves as a huge collection of available spare parts that is continuously being used to supply the aircraft that are still in service.
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How do pilots determine the takeoff distance of an aircraft? While making a flight plan, depending upon the weight of the aircraft, I'm assuming pilots determine the takeoff distance. How do they do so (is there a formula to calculate the takeoff distance)? <Q> Most airplanes have a POH (Pilot Operating Handbook) with a table on aircraft distances. <S> Here I have included one for the C172 . <A> Takeoff data is calculated using performance charts and/or software. <S> Data input into the algorithm include: runway condition runway slope, wind (headwind or tailwind component), takeoff weight, aircraft configuration (flaps, slats, etc) density altitude <S> We didn't actually calculate the takeoff roll distance, but rather that we were below the max weight that could accelerate to V1 and stop within the distance provided by the runway in the current wind, temperature and aircraft configuration. <A> The previous answers are indeed correct; I will take it one step farther up the stack, though, and make a point that may have been unclear and addresses an assumption. <S> The pilot doesn't calculate take-off distances; they are looked up. <S> The manufacturer of the aircraft, based upon their own math and the results of real-world-testing, is the authoritative source. <S> Once it's in the operating handbook, you can be confident of those numbers (and, in fact, shouldn't second-guess them without a bloody good reason). <S> As was also mentioned, some operators do their own testing; these results then go into the operating handbook, and the pilot is then expected to be able to count on those numbers as long as they follow the same procedure. <S> One of the most important aspects of flight is consistency; given the same external conditions, all aircraft of a particular model and particular takeoff weight should perform very similarly. <S> This is more than just minimums. <S> In the case of a broken instrument, whatever is being measured by the broken instrument can usually be inferred from other instruments. <S> An example would be airspeed; if your airspeed indicator is broken, but you know your engine RPM and know that you're not climbing or descending, then you should always be about the same airspeed given that engine speed. <S> A Cessna 172S would always be very near 120kts at 2400rpm at 2200 pounds weight. <S> This consistency is what allows those numbers to be recovered and depended upon. <S> (pulling numbers from head; the point is that you should be able to go into ANY Cessna 172S and expect the same performance as long as the plane has been properly maintained). <S> This is also true of many other critical aspects of an aircraft's performance. <S> Climb rates, fuel consumption, rate of change-of-direction in a turn... <S> these numbers all have to be accurate, as they can mean the difference between making the runway and becoming a news story. <A> Besides using tables, aircraft manufacturers also provide a takeoff chart, like this: <S> The chart goes from left to right: <S> Enter the air temperature, then go up until you met your pressurealtitude. <S> Then proceed horizontally to the right. <S> Follow the contour of the lines, until you meet your weight on thex-axis. <S> Proceed horizontally to the right. <S> Follow the contour of the lines, until you meet your headwind (ortailwind) component in the x-axis. <S> There, leave the contour and gohorizontally to the right. <S> The y-axis gives your takeoff roll distance. <S> If there is an obstacle50 feet at the end of the runway, follow the lines to get your"takeoff roll + clear obstacle" ground distance. <S> Some manufacturers provide tables. <S> Some provide charts. <S> Some do both. <A> The way we teach at our school is that, for example, if you are doing a normal takeoff and your POH only has short field effort, take the Vr and the Vlof, and find the difference. <S> For a C172sp that is roughly 9kts difference. <S> So now take your normal takeoff speed, and add that difference for your Vlof normal. <S> You'll find that it's almost a 10% increase in speed. <S> As a rule of thumb, a 10% increase in speed will equal about a 21% increase in distance.
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The air carrier I flew for had a performance chart for every runway we operated from (all scheduled and alternate destinations) that we could reference for the max allowable takeoff weight for that runway, flap configuration, wind condition and temperature. As mentioned, external data sources are used.
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Why is stall speed listed in a POH? In this comment on this question about stall warning systems, it was stated that: You can stall at any airspeed (see this question and this one) and in any attitude, only the AoA is important because that's what causes the airflow to separate from the wing. Why, then, does the Cessna 172's POH (Page ii or 2 of 422) list stall speed , not stall AoA ? I can understand how flying slower than the listed speeds would cause a stall, but the comment above seems to imply that one could stall the plane by flying at 60, 90 or even 120 KCAS but at a high AoA. <Q> Those stall speeds are derived for specific conditions. <S> In the case of that POH those speeds assume level unaccelerated flight, 2550 lbs gross weight, standard atmosphere and no wind. <S> A non-aerobatic airplane also spends most of its time in the part of the flight envelope where the assumptions needed to list a stall speed tend to be valid. <S> The stipulation of level flight means the relative wind is fixed, thus the AoA depends only on the pitch attitude above the horizon. <S> For an given weight there is a relation of pitch attitude required to maintain level flight for a given airspeed. <S> Given these specific stipulations, you can determine the airspeed that results in the critical AoA being exceeded. <S> If any of the criteria listed above are not true, then those published stall speeds are not meaningful to you. <S> You can stall at any attitude and at any airspeed. <S> To see the true relation between airspeed and stalling you need to consult a Vg diagram. <S> The curved lines starting at 0 MPH and 0 load factor represent the stall speed for a given load factor. <S> The stall speed listed in PoH <S> you quote is specifically the point noted "Normal stall speed" on this chart (this chart isn't for the same airplane, so the numbers will differ). <A> Most small planes do not come with an AoA sensor or display, so giving the stall AoA isn't useful to the pilot. <S> The bulk of flying is done in the vicinity of level flight, no roll. <S> When in that configuration, there is a simple relationship between airspeed and angle of attack. <S> So the airspeed provides useful information about how the wing is likely to be doing. <S> It must be understood by the pilot when that relationship is no longer valid. <A> Cessna 172s don't have an AoA indicator or gauge and even today most light aircraft still don't, although you can add them to some models and the FAA would like more aircraft to have them . <S> So in the absence of an AoA instrument, airspeed is used as a rough proxy, assuming 'normal' flight conditions. <S> Crudely put, if your C172 is flying at a more or less steady 110kts then the AoA is low and you have a lot of 'reserve' before you stall; if you're flying at 60kts then it's high and you have only a little reserve. <S> This is why watching your airspeed closely on final approach is essential. <S> But because airspeed is only a proxy for AoA, it isn't a completely accurate way to know how close you are to a stall. <S> Changing the load factor (roughly, the G force on the aircraft) changes the stall speed but not the critical AoA, which always remains the same (18° is commonly mentioned for light aircraft, but that's an approximation). <S> The diagram in @casey's very useful answer shows this clearly. <S> Finally, note that 14 CFR 23.49 says that light aircraft must stall at a calibrated airspeed of 61kts or less <S> , there's no mention of AoA.
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They are given as a speed rather than raw AoA because most non-aerobatic small airplanes lack AoA indications in the cockpit, while all have airspeed indicators.
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When to turn base at towered airport? When at a towered airport and instructed to make " left pattern for runway 3, " am I supposed to wait for the base leg turn until tower clears me for landing? This seems to be the norm, but I can't find anything in the FAR/AIM to indicate what is acceptable. Related: I often get confused when in the downwind pattern and I hear something like this: " 123X, tower, you are #2 for runway 3, following a Cessna on final. " Does this mean I should turn base and follow the Cessna? I know the correct answer is to ask ATC to clarify, but it would be ideal if this were spelled out in the AIM. <Q> You have a few questions here. <S> ... <S> downwind pattern <S> and I hear something like this: "123X, tower, you are #2 for runway 3, following a Cessna on final." <S> In this case what you will do is continue your down wind leg while scanning for the Cessna traffic, some towers may ask you to "report traffic in sight" in which case you will say "traffic in sight" when you can see the Cessna. <S> If he is on a long final you can begin turning your base (assuming you are in a similar small plane of a similar speed) when he is on your beam (right off your wing tip). <S> This should provide adequate spacing for you to come in properly. <S> Keep in mind that the tower may also instruct you to do things to keep separation like "123X Extend your down wind 1 mile" etc. ...instructed to make "left pattern for runway 3," am I supposed to wait for the base leg turn until tower clears me for landing? <S> This depends on where you are coming in from. <S> I have flown into towered airports on the runway heading and simply come into the pattern on final and was cleared to land about a mile from the runway. <S> Other wise I typically report my midfield downwind to the tower "Piper 12345 Reporting Left Midfield Downwind for RW24" then the tower will respond with my landing clearance or instructions to extend. <S> The other situation I have been in is a case where the controller deliberately does not clear you but has <S> you come into the pattern and approach. <S> This occurred while they were waiting for an IRF plan to come through for one of the regional jets waiting for departure. <S> Since they did not know when it would come in I was instructed to continue my pattern and would be cleared on final if they did not need to get the jet out. <S> However I was explicitly told I would be cleared on final <S> so I knew what to listen for. <A> I am Australian, but I can't see why these procedures would differ greatly between our countries. <S> The answer to your first question is no. <S> In the absence of airport-specific published procedures, you do not need to wait for tower clearance to turn base, however you must tell them that you are commencing the turn. <S> Usually once you tell them that you're turning base you are given a landing clearance. <S> The exception is when you are specifically asked to report before turning base - it is not uncommon for tower to ask you to report when ready for the base leg, in which case you must not turn until cleared. <S> Regarding your second point, if I take it exactly as you have presented it here that is a traffic information message only, with no clearance. <S> The same procedures as above apply. <S> However if you are told that you're following traffic in the pattern, you must not turn base unless you have identified the other aircraft. <S> Accidents have been caused by the trailing aircraft 'cutting in front of' the aircraft in front. <A> Typically in Cessnas or similar light GA aircraft, I teach to do so when the runway threshold is 45° off your shoulder, as the Airplane Flying Handbook suggests. <S> I will also teach students to reduce power, begin their descent at ~500 fpm and begin to add flaps abeam the threshold. <S> This will work out such that you have the threshold 45° Off your shoulder when you are about 200 ft below pattern altitude, so that can provide a good gauge as well. <S> In regards to the radio call out you mentioned, no, that’s not how that works. <S> The tower is telling you that you will be #2 to land following traffic and then is pointing out to you the position of that traffic relative to the airport pattern so you can easily locate and acquire it. <S> You will proceed on course as you are, but accord the landing traffic sufficient spacing <S> so he can land and taxi clear of the runway before you land.
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While it is the towers responsibility to clear you for landing and what not, controllers are not perfect, you can continue on towards the runway in your pattern but if you have not been cleared you should go-around or ask for clearance. There’s no official rule as to when.
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What would happen if a pilot were to use the parking brakes after touchdown in order to slow down? The situation that I came up with is merely hypothetical. Say a pilot was unable to land right after the runway threshold, for whatever reason it may be - a crosswind, etc - but was determined to land the aircraft. I understand that most pilots would abort the landing and go around but say this one decides to land. However, it is too close to the end of the runway to stop just by using brakes, spoilers, and the thrust reversers. Could this type of landing (in an emergency) be achieved and by using the parking brakes what would happen if a pilot actually used the parking brakes to slow down? <Q> This question appears to have an implicit assumption: that the parking brake would provide more deceleration than is available from normal braking. <S> This is not generally the case. <S> A much greater worry for pilots than insufficient braking is actually excessive braking - to the point that the wheel locks up and skids. <S> A skidding tire provides much less braking than a rolling one, and also quickly acquires a flat spot. <S> Even on dry pavement, maximum braking would require an anti-skid system to remain effective; consider a 757 and a Mig-29 , each of which blew out their tires when their anti-skid systems failed. <S> Note also that in small planes without complex braking systems, the parking brake merely maintains the pressure that is in the brake lines at the time it's applied. <A> There is some nice info on this thread and it seems that the parking brakes on large airliners actuate the hydraulic systems as would be expected (unlike in some cars where the parking brake is its own mechanism). <S> It also alludes to the fact that some emergency landing procedures would call for the use of the parking brake. <S> On a related note, it should be mentioned (and I don't know enough to know if this is actually possible in a large airliner) but I would think you would not want to lock the wheels to the point that they lost traction. <S> This would actually reduce your braking ability. <A> Not quite the scenario you set up, but there was a case where a regional airliner landed with too much speed and too little braking effort. <S> The pilot performed an unapproved and improvised action by applying the parking brake in an attempt to maximize braking. <S> What he did not know was that by applying the parking brake, he deactivated the aircraft's anti-skid protection resulting in reduced braking effectiveness and an overrun down a steep slope. <S> As a general rule, tires work better at stopping a vehicle when they are rolling than when they are skidding because they generally have greater static friction (gripping) than dynamic friction (skidding). <S> A parking brake is generally meant to keep a stationary vehicle from rolling away, not stopping one. <S> Parking brakes may not be capable of generating enough force to do the job of stopping a vehicle or if they can generate the required force may not provide adequate control to avoid locking up one or more wheels in a skid. <S> I think the bottom line here is that if it hasn't been written into an aircraft's approved procedures, it's potentially a bad thing.
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The parking brake would have no effect if the pilot were not already on the brakes, and would not be able to add any additional braking than the pilot could otherwise apply.
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What is currently the longest commercial flight in terms of distance? Flightradar24 has announced few hours ago , that Qantas QF7 is taking off for its 13,804 km long flight and named it the longest commercial flight (by distance) . Is that correct? I was more than sure, that I heard few years ago, that current record belongs to Singapore Airlines, that has at least one commercial route of a little bit more than 14k kilometers. <Q> According to Wikipedia , the flight you are referring to, SQ21, got discontinued in November 2013. <S> The runner up, still from Singapore Airlines, SQ37, got discontinued one month earlier. <S> The same page reports that QF8 is the current holder of the title of "longest non-stop flight" and has the same destinations as today's QF7 as of February 2017 Qatar Airways flights 920/921, covering 14,534 km (7,848nm / 9,031mi) from Doha, Qatar (DOH/OTBD) to Auckland, New Zealand (AKL/NZAA) , <S> beats QF8 by about 395 NM. <S> The title of absolute longest flight without refueling is instead held by a non-commercial flight done in an aircraft specifically built for the purpose. <A> According to this CNN article , the record has been broken because of the COVID-19 outbreak: <S> On March 14, French airline Air Tahiti Nui flew the longest ever scheduled passenger flight by distance -- transiting 9,765 miles across the world from Papeete, in Tahiti, French Polynesia, to Paris' Charles de Gaulle airport. <S> This one off milestone was a direct consequence of the coronavirus-induced US travel restrictions. <S> This route usually involves a scheduled stopover at Los Angeles International Airport (LAX). <S> But when an airplane stops over in the US, all passengers must alight the aircraft and proceed through US Customs and Border Protection before they're allowed to advance on with the next leg of their journey. <S> Current restrictions rendered this part of the journey untenable, so instead, flight TN064 just carried straight on, departing at 3 a.m. local time from Papeete airport and arriving in Paris at 6:30 a.m. local time on March 15. <S> This is a scheduled flight, but a one time deviation from the schedule (though the situation may continue to be like this in the near future). <A> Air India 173 flies over Pacific some times. <S> It often travells 9500 miles+ in 15 hours. <S> On 21st October 2016, it flew 10,204 miles (16,480 km). <S> Source
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If we instead include 1-time-only flight by a commercial airliner, the longest one has been flown in November 2005 between Hong Kong and London, as a demo by Boeing.
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How is it possible for manufacturers to constantly get data from their planes all over the world? I've heard that manufacturers (like Boeing and Airbus) constantly get data from their planes. So in the case of an emergency, ATC's or pilots can contact the manufacturers for assistance. How do manufacturers constantly get this data and how is it stored (cause considering the number of planes flying today, it must be a lot)? <Q> How do makers get data from aircraft in flight <S> The data is usually transmitted using something like ACARS which is a system used in aircraft to transmit data in flight using underlying radio and satellite communications systems. <S> The communications infrastructure is typically provided by large multinational companies who specialise in this job. <S> See ARINC, SITA, Inmarsat and so on. <S> Engine-makers and Aircraft makers often offer pro-active maintenance and support services to airlines, operators and lessors which involve their aircraft transmitting such data to the makers. <S> For example, Airbus has <S> AIRTHM Airbus Real Time Health Monitoring (AiRTHM) is an advanced service through which A380 and A350 XWB operators can receive guidance on optimised maintenance and real-time troubleshooting actions. <S> As part of this effort, a dedicated 24/7 team takes advantage of the uplink technology to further investigate and anticipate warnings/fault consequences. <S> The uplink technology allows real-time remote access to aircraft data parameters via the ACARS digital datalink system, enabling Airbus AiRTHM engineers to deliver maintenance and technical advice both in flight and on the ground. <S> Note that ACARS is a relatively low-volume data transmission system. <S> Makers have explored other underlying communication systems as a way to transmit more data at lower cost. <S> How is this data stored <S> It is true that there is a lot of data but Boeing and Airbus are big businesses and are able to partner with major IT businesses. <S> For example IBM work with Airbus <S> “Today’s aircraft can generate up to a half terabyte of data per flight, an unprecedented volume and variety of data seen in few other industries,” said Timothy Wholey, IBM global leader for the aerospace and defense industry in its global business services unit. <S> Note - not all data has to be transmitted in flight. <S> A lot of data is collected and stored in the plane and only transferred when the aircraft is on the ground. <S> Makers like Airbus and Boeing inevitably are already very heavy users of IT for aircraft design purposes. <S> For example, Airbus use HP Supercomputing hardware <A> They are installed with some sensors which keep sending important data to the manufacturer. <S> And, talking about their size, they are merely in just KBs, which is very small compared to storage the amount available even for all flights combined. <S> Also, all information collection is automatic i.e. handled by computers <S> so there is no problem in collecting information either. <S> Read: http://www.forbes.com/sites/johngoglia/2014/03/13/aircraft-engine-monitoring-how-it-works-and-how-it-could-help-malaysia-air-370-crash-investigtors/ <A> Boeing has a system installed in many airplanes which monitors engine health. <S> It is called Airplane Health Management. <S> A good presentation can be seen here (more info here and here ). <S> Airbus uses Airbus Real Time Health Monitoring (AiRTHM) which essentially does the same (more info here ). <S> Please note that these systems are not installed on every single airplane but are getting popular more and more.
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Boeing have AHM AHM sutomatically monitors, collects and transmits service levels using ACARS through the installed Aircraft Condition Monitoring System (ACMS)
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Why is the manufacturing process of an aircraft mostly manual? Why is the manufacturing process mostly done by humans, and not by robots as in case of most other industries? Video <Q> Although robots have taken over many jobs in the process of manufacturing things like cars, airliners are much larger and more complex. <S> In some ways it has more in common with constructing a building than assembling a vehicle. <S> There is a much larger variety of tasks to be performed over a much larger area. <S> That being said, many parts of the manufacturing process are completed by robots. <S> For example, Gemcor makes machines that automatically drill aircraft wings and fasten them with rivets and bolts. <S> Robots are also used in manufacturing large composites . <S> You'll notice how massive these machines are, and they are only completing one task on one component. <S> They are very good at tasks that require one or more of force, repetition, and accuracy. <S> However, so much of the process is not economical to be done with robots. <S> Many tasks involve working in tight spaces, which humans can do better than a large robot. <S> Tasks like installing wires require dexterity as well, which humans are better at. <A> Economy of scale is a factor. <S> Even the most produced airliners, the B737 and the A320, are delivered in a few hundred units every year. <S> Divide the investment cost over the production number, and when is the investment going to be recouped? <S> And the work that the robot must be programmed to do is highly skilled work, which for a large part takes place inside the aircraft: wiring through holes in the stiffeners, tubing for the air conditioning aystem etc. <S> Highly complex work in constrained spaces divided by not many units makes poor economics for automation. <A> Costs. <S> All that is new is very difficult to promote in Russian aviation. <S> And I'm talking not only about aircraft. <S> The main reason for this is red tape. <S> And "reliability"... <S> It is assumed here that if something works well for many years, then it is better to leave it that way and do not change anything. <S> As was mentioned above: Economy of scale is a factor. <S> It's really true! <A> With robotics, it's cost versus expected return. <S> The cost of the robot is directly related to the complexity of the task. <S> For example, a simple screw driving robot can cost upwards of $100k, plus line testing and adjustments that add at least another 10k-20k - despite high tech, there is still a substantial element of trial and error to assembly line robotics. <S> The expected return is replacing a human - what is the cost of the human, how many times does the human make a mistake, and can the robot operate faster than the human? <S> In the aforementioned screw driving robot, it replaces a human that costs the company $50k-60k per year (by the time one factors in benefits costs, etc...) and operates faster than the human which pushes up line throughput, so it pays for itself after about 1 year. <S> Robots can still make mistakes, as the components of the robot wear or fail. <S> Volume of production is also a major factor - a robot is cost efficient in high volume and simple tasks, as the benefit is directly tied to a per unit cost reduction. <S> The fewer units, the less the benefit. <S> Humans can think during the process, can analyze, suggest improvements and spot potential problems. <S> while the robot can only do what it is told to do. <S> The more complex the task, the more this ability becomes important. <S> With aircraft assembly, you have relatively low volume and very high complexity. <S> Building robots to take over the more complex assembly tasks would be extremely expensive, with not enough per unit cost reduction to justify the expense.
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A robot is an investment - a big one, since robot costs are proportional to size, task, precision etc. A robot specializes in one task or one type of task, while humans can do many different tasks. Here in Russia we have two main reasons: Conservatism in Aviation sphere.
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What prevents a passenger from opening the emergency door on his own will, mid-flight? I have never sat on the emergency seats near the wings, with the emergency exit. I have seen cabin crew instruct the passengers seated near the door on how to operate the door. My question, what prevents a 'rogue' passenger from opening them mid-flight? <Q> At cruising altitude there is between 4 and 8 tons of pressure acting on the inside of the door. <S> There aren't too many passengers capable of exerting that much force on the handle (and even fewer handles that won't just snap off). <S> It's theoretically possible to open the over-wing exits at approach altitudes when there is no pressure differential. <S> Other than being windy/noisy <S> it would not affect the flight in any way. <S> Cabin doors usually open forward, good luck pushing them open against the airflow. <S> If the person who pulled the window plug wants out, it's their (and only their) funeral. <S> I've sat in the open doors of light aircraft in flight hundreds of times, legs in the breeze, no seatbelt, while the plane makes fairly steep turns toward the open door side. <S> It's not a problem. <A> In addition to the pressure differential, some aircraft also have mechanical locks. <S> Here's the logic diagram for a 737 NG. <S> This will be similar to all of Boeing's exit doors that are hinged at the top. <S> These conditions cause the emergency exit doors to lock: <S> Three or more of the entry/service doors are closed, and Either left or right engine is running, and Air ground logic is in the AIR MODE, or The left and right thrust levers are advanced more than 53 degrees <A> At $10,680 m$ cruising altitude air pressure is $23.8 kPa$ / <S> $3.45psi$ / <S> $23,800 N/m²$; <S> compared to $101kPa$ / <S> $14.7psi$ / <S> $101,000 N/m^2$ at sea level. <S> Now a 747 for example has a pressurization altitude of $2,440m$ which equates to an internal pressure of $75kPa$ / $10.9psi$ and a force of $75,000 <S> N <S> /m^2$. <S> So the internal pressure of $75,000 N/m^2 - 23,800 N/m^2 = <S> 51,200 <S> N/m^2$ Door dimensions are $1.93m (H) <S> \times 1.07m (W) = 2.07m^2$ Or in feet & inches: $6'4" (H) <S> \times 3'6" (W) = <S> 22.17 sqft$ <S> So <S> $51,200 N/m^2 \times <S> 2.0651m^2 = <S> 105,733.12 <S> N$ Which equates to roughly 11.88 Metric Tonnes of force on the inside of the door! <S> The door being larger than outside portal of the door. <S> It is forced into the frame with considerable pressure. <S> It would be impossible for a human to operate the door under that force. <A> The pressure differential will stop you. <S> In flight the airplane is pressurized to keep you conscious at high altitude. <S> The doors plug doors with flanges and must be pulled inwards to open them; those flanges make them impossible to move even after you release the latches. <A> A young man jumped from a plane : The Globe and Mail "The Beechcraft King Air 200 turpoprop aircraft was flying at about 23,000 feet at the time of the incident."
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Latch type doors have interlocks or over-center latches that prevent operation with a pressurized cabin.
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“ , remain VFR” — may I enter Class C airspace? During a flight yesterday, the approach frequency for a local Class C was unusually busy. I was heading back to an underlying Class D and the frequency finally quieted down enough for me to poke in a call of Huntsville Approach, Cessna 123AB, VFR with request . ATC responded with <identifier>, remain VFR . I am not positive whether he gave the full callsign or just Tree Alpha Bravo — either way, definitely not Aircraft calling . He did not instruct me to remain clear . I understand that radar advisories are workload permitting for VFR traffic, and clearly ATC had all the workload they could handle. Does that reply establish two-way radio communication and thus permit entry into their Class C airspace, just without flight following? What if the reply had been Tree Alpha Bravo, remain VFR ? Assuming it does establish two-way communication, is it good Aeronautical Decision Making to fly into known busy airspace without advisories? Rather than requesting confirmation on a busy frequency, I descended below the shelf feeling like a scud runner. Approach and landing at the Class D were otherwise uneventful. <Q> The AIM 3-2-4 has the best explanation of this (see also the basic regulation in 14 CFR 91.130 ): <S> If the controller responds to a radio call with, “(air craft callsign) <S> standby,” radio communications have been established and the pilot can enter the Class C airspace. <S> If workload or traffic conditions prevent immediate provision of Class C services, the controller will inform the pilot to remain outside the Class C airspace until conditions permit the services to be provided. <S> It is important to understand that if the controller responds to the initial radio call without using the aircraft identification, radio communications have not been established and the pilot may not enter the Class C airspace. <S> So if the controller used your callsign then you've established radio communications and you can enter. <S> This also applies to class D but not to class B, where you need an actual clearance to enter. <S> (This is a classic exam question/scenario, by the way.) <S> As @rbp suggested, the instruction to "maintain VFR" was probably the controller's way of letting you know up front that he was too busy to give you a pop-up IFR clearance or whatever else you might have wanted. <S> ( Maintain is an official ATC term , <S> remain <S> is not, although the controller may still have used it accidentally.) <S> As for flying into busy airspace, it's up to you as PIC to determine what's safe and what isn't. <S> If you had the HSV ATIS (so you can anticipate traffic patterns), were squawking 1200, were in communication with ATC and were keeping your eyes outside the cockpit <S> then there's not too much more you can do (you could turn on all your lights if you think you need to make yourself more visible). <S> But, if you ever feel unsafe or uncomfortable in any flight situation then you shouldn't hesitate to take action - like staying clear of the class C for a few minutes - if you do feel it's necessary, that's simply part of gaining ADM experience. <A> You have to differentiate between a clearance which has a specific regulatory definition that is covered by numerous FARs, and the regulation which requires you to establish 2-way communication before operating in Class C or Class D. <S> If you hear your numbers, you have established 2-way communication, and that's it. <S> Its not a clearance , as defined by the FARs. <S> "Remain VFR" is completely different instruction not related to permission to operate inside the Class C. <S> It is usually given when the controller thinks you might be calling him up to request an IFR or SVFR clearance and he is telling you, in advance, that he can't do it right now. <S> It is also unfortunate that "remain clear" and "clearance/cleared" both use the same word. <S> But they mean completely different things. " <S> remain clear" has nothing to do with a clearance, but tells you to remain outside the controller's airspace. <A> No clearance is required for VFR Flight in Class C airspace. <S> It is however required to establish two way radio communications ( FAR 91.130 ). <S> The most common interpretation I've come across is that as long as ATC have responded with your callsign, you have established two way radio communications, and are therefore free to enter, unless instructed to remain clear. <S> I'll leave the discussion about ADM to others, but being unsure of what the ATC response meant, you took the conservative route, based on the information in your post. <S> However, even if ATC is busy, it is very seldom too much to ask for clarification.
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Yes, you were allowed to enter the class C in that case, but you weren't cleared to do it because no clearance is needed to operate in class C, just communication with ATC.
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What is the maximum age limit for getting a pilot licence? Can I do pilot training courses even after age 26 ? <Q> As far as I know there are no maximum age restrictions on getting a pilots license anywhere in the world. <S> Many countries have a minimum age restriction for getting a license, that usually does not prevent pilot training from taking place. <A> To expand a bit on @GdD's answer, <S> That said, your individual circumstances may be different. <S> There are some exceptions to this even in the civilian world, such as maximum age limits when flying for certain airlines (such as the age 65 rule for Part 121 operations in the US). <S> If you're in a part of the world where airlines offer cadet programs and such, they may also impose maximum age limits for applicants. <S> If you're interested in military flying, the armed services may also have additional restrictions on maximum age for flight training; the USAF for example, had the age of 26 as the upper bound for anyone applying for a pilot slot about 5-6 years ago, and armed forces the world over have similar restrictions in place. <S> Edit: <S> Thanks to @SSumner for providing a link with the current age limits for US military pilot training. <A> It would help if you specify if you are getting the license to fly private or commercially. <S> For private there is no age restriction if you pass your medical, as is the same for commercial. <S> However as mentioned some airlines may prevent you from flying after a certain time. <S> That all being said this video brings up some good points about starting training later in life (in your 30's). <S> It takes a lot of hours to become a commercial pilot and <S> the later you start training the later <S> you enter the workforce (as with any job). <S> I would think 26 is perfectly fine. <S> Im getting my Private Pilot and started at 23. <S> There are plenty of people at the flight school well over 50 starting their training as well.
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a number of aeronautical regulatory bodies, including the FAA, do not specify a maximum age for flight training or executing the privileges of Pilot-In-Command under most circumstances ; as long as you hold a valid medical, you're in the clear. 26 is fine, in fact 76 is fine as long as you pass whatever medical is required.
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How much power is needed by aircraft IFE systems during flight? How much power is needed by aircraft In Flight Entertainment systems during flight if they operate all the devices connected in the cabin? <Q> I don't have specifics but lets extrapolate for a minute (using the Boeing 777-300 for size filled with lets <S> say 500 seats). <S> Assuming you are talking about IFE systems where there is a screen in every seat then you will most likely have screens similar to this . <S> While not exactly what the airplane uses I would think they are similar. <S> The specs for that screen claim it takes <= <S> 8W. Lets round it out and say it takes 8w. <S> Looking at our 500 seats thats 4000W of power. <S> I can only assume there is a computer or two of sorts running those displays <S> , lets say they have 500W (typical desktop supply on the more powerful side) and there are 2 of them. <S> Thats another 1000W <S> so you are at 5000W there. <S> Assuming you have 120V power P <S> = <S> IV <S> thats about 41 Amps of current you will draw from the system. <S> I am running this assumption that all the screens are on at all times as I assume the system is built for that. <S> Cabin lighting is tough as I have no idea how many bulbs they have in there. <S> I know that each seat has its own little lamp so you are looking at 500 little lamps running in the 1W-10W range. <S> So maybe another 2000W for the individual lights. <S> Overhead is tough since you cant really see the individual bulbs. <S> It should also be noted that LED's are becoming more wide spread and draw way less power than traditional incandescent bulbs which will greatly reduce the amount of power drawn by the interior lights. <A> Cabin Lighting <S> New aircraft exclusively use LED lights 1 for cabin lights. <S> Compared to incandescent or fluorescent bulbs, LED bulbs much less power. <S> If I'm not mistaken, LED bulbs are being used on aircraft lighting (at different levels) for 20 years or so. <S> In-flight Entertainment Power consumption of IFE systems is mentioned here : <S> Most IFE system PSUs fall into the power range of less than 100W, although some newer IFE products require higher power solutions of 300 watts, or more. <S> Please note that an IFE system is not just the monitor a passenger sees, but it has other hidden components too, which require power as well. <S> 1 <S> Biggest example is A380 : <S> The A380’s interior illumination system uses bulbless LEDs in the cabin, cockpit, and cargo decks. <S> The LEDs in the cabin can be altered to create an ambience simulating daylight, night, or intermediate levels. <A> I had a look around but couldn't find too much. <S> This is a competitive industry so they would be inclined not share too much information (a bit like fuel and jet aircraft). <S> The power consumption is probably the top of the iceberg of important things to consider and I imagine manufactures don't want to make their products look unattractive without showing the customer the full scope of what they are buying, such as software capabilities. <S> After much searching, Rockwell Collins were kind enough to publish (dated 2013) <S> some information for overhead monitors systems. <S> The media server uses about 80 watts (so a bit more than an average laptop) and the interactive screen to control the content about 20 watts. <S> There is no figures on how much each actual screen uses. <S> Be aware this is for a system that shows the same content on all screens. <S> Be aware however that it was written in 2008, the year after the first iPad was released and tablet computers (and corresponding expectations) took hold in the public. <S> A lot has happened since then and as stated in the paper newer systems can draw a lot more. <S> Furthermore, power supplies can be shared among multiple seats (the one shown in the paper has "multiple outputs"). <S> This quite extensive paper also discusses IFE design. <S> The competition also means that they would like to make the devices as light and efficient as possible. <S> Looking at the X-Series from Panasonic ("The world's most popular in-flight entertainment system" quoting themselves) <S> the screen does video decoding and also includes Android compatibility. <S> Aside from the substantially higher price tag, I think it would be a fair estimate to compare the power in the high range for a tablet computer. <S> It's always good to contrast these figures: If you're going to go providing AC and USB plugs, laptop chargers use in the range of 80 watts and half the passengers on a A320 use a USB plug for their charging their empty gadgets, you're looking at 350 watts.
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It depends on how many lights are on, and how much the in-flight entertainment system is in use. I found to this document that suggests that the power supply draws around 100 watts (that would fit with the suggestion above).
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How much power is used by cabin lighting systems during flight? How much power is used by cabin lighting systems during flight when all the lights are ON? <Q> Almost all lighting systems installed today use Light Emitting Diodes for weight savings, reduced power use and less maintenance. <S> Compared to other aircraft systems, their power use is pretty insignificant. <S> For the reading lights, I found the following quote: Passenger reading lights in halogen technology use 11 watts, while the latest LED products use only one watt. <S> Source <S> The actual ceiling ceiling lighting power consumption seems more difficult to find. <S> SAAB <S> in a brochure for converting fluorescent to LED lights for their SAAB 340 & 2000 <S> models states: <S> Power consumption is reduced from 8 watts per 12 inch tube to just 5,1 watts. <S> Emteq suggests savings of around 15% for LED compared to fluorescent lights, so SAAB's suggestion would be a bit more. <S> This manufacturer quotes 10W for a 16-inch (40cm) <S> LED strip running off the 28V aircraft DC system. <S> Needless to say, power consumption depends on the wattage of light installed. <A> I cannot find Mike Foxtrot's answer so this might be duplication. <S> Every type of aircraft is likely to have its own type of lamp & its own number of lamps. <S> Also, cabin lamps can be dimmed & reading lamps are a variable load. <S> LEDs are getting more powerful (light output/energy consumed) so fewer lamps are needed, but this comes at the price of more heat generated; this requires heatsinks. <S> So the designer will select lamps on the basis of light output, area to be illuminated, power consumption, heat output & heatsink size. <S> So a definitive answer to your question could only apply to one type of aircraft. <A> According to this link , an Airbus A-321 has around 100 LED units for cabin lighting which have 45 individual diodes each. <S> Do you have 4500 diodes in the cabin in a single aisle plane, which means at 0.05W per LED estimation, the cabin lighting would require 225 W of power. <S> p.s. <S> This does not include reading lamps (most probably) and only the aisle lighting.
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The power consumed is the power used by each lamp multiplied by the number of lamps.
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For an electric airplane are propellers the only option for propulsion? This is for an electric airplane (so no fuels for combustion): Are propellers the only option? Is there a turbine-jet possible with only air intake, electrically compress, and a turbine and nozzle and get equal or more thrust than a propeller like a water-jet but then with air? <Q> It is currently the only efficient way to generate thrust with air as a medium. <S> Even jet engines are in some sense just a very elaborate system of propellers. <S> The reason for the turbine is to create an environment to efficiently burn fuel ( suck, squeeze, bang, blow ) to generate as much thrust as possible. <S> Hence, in an electric aircraft this is irrelevant. <S> You might be interested in the Airbus E-Fan , which uses ducted propellers increase efficiency. <S> However, it is still 'just' a propeller with an electric motor in the middle. <A> You may choose whatever propulsion you prefer, but need to accept the consequences. <S> An electrical turbine is easy to build, but will need a lot of power for heating the core flow. <S> Instead of burners you will need to install heater elements, which will necessitate a longer flow path and more volume between compressor and turbine, but by and large <S> the electric turbine engine will look much like a fuel-burning one. <S> You can also remove all the turbo machinery and only drive the fan with a big electric motor. <S> But that would have lower efficiency than turning a propeller instead, so only when your flight speed will cause supersonic propeller tips might an electrically powered fan be a better alternative. <S> Therefore, at speeds below Mach 0.7 propellers will give you more thrust per kW of power, and their efficiency is best at low speeds . <S> The much lower energy density of electric storage will demand flight at low speed, or your flight time will be very short. <S> Therefore, propellers are the best, but by no means the only solution. <S> A potentially even more efficient method might be ionic thrusters where a high voltage is used to ionize and accelerate air in order to produce thrust. <S> Designs using ionic thrusters would use the whole airframe for thrust creation and would need to be run at tens of thousands of Volts, but their potential efficiency surpasses even that of low-speed propellers - in theory. <S> The linked article, however, is an embarrassment to MIT. <S> A 1 kW jet engine that produces only 2 N thrust has to fly very fast (500 m/s, to be precise) while the 110 N cited for the ionic thruster at the same power <S> mean that it could not had moved faster than 9 m/s. <A> You do not have hot combustion gases in an electrically powered engine. <S> The only gas available to you is the air around you, and some form of propeller is the most logical way to accelerate that air. <S> The nozzle you're imagining can be used to turn a large, slow stream of air into a faster but smaller air stream. <S> This can't provide thrust by itself as it isn't a powered engine part. <A> Ducted fans rather than external propellers increase the performance at high speeds, so gets round most of the problems. <S> While they do look somewhat like Jet engines, they are basically just prop engines in a tube, so they can better control the air-flow, which at high velocities, can cause issues for exposed props. <A> For your requirement to use a battery for silent takeoff and landing, electrically driven propellors (or ducted fans) would certainly be good enough. <S> The requirement you mentioned for 350 mph to 550 mph is really only for cruise, which presumably would use a turbofan (or possibly turboprop) - and recharge the battery at the same time. <S> So I would guess what you want is a fairly high performance ducted fan which can be driven by either electric motor for silence or by a conventional turbine at cruise - a bit like a turboprop. <S> The question is then how do you arrange for an exchange between the two power sources. <S> (I assume two sets of engines wouldn't be possible, though perhaps they could be?) <S> (Edited to add... <S> your electric motors still need full power to takeoff. <S> So why not run the motor all of the time, and use an auxiliary turbine engine to provide the electrical power at cruise? <S> Not unlike a hybrid car.) <A> The main difference between air and water is that the second cannot be compressed, while the first can and when you do, you heat it up loosing a cospicuous amount of energy. <S> The more you compress it and the more time you wait before releasing it, the more energy you loose. <S> A propeller also compresses the air: this is necessary to accelerate it, but it allows to achieve high air velocities with the minimum amount of compression. <S> It is also a very simple and light design, moreover one of the motivation to have an internal water compressor is the possibility to filter it, which is not required with air.
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You aren't really going to want to carry fuel AND batteries, so some sort of ducted fan is the best solution for a high speed aircraft. Propellers in some form are really the only option.
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Do planes use autopilot when flying in formation? I've attempted to fly formation over a multiplayer flight simulator, and it was incredibly hard. It felt really hard to have the two planes go exactly the same heading, so it was always necessary to sway the yoke back and forth, constantly overshooting and undershooting. When real planes fly formation, do they use some sort of short-range radar system and an autopilot to maintain the formation shape? I could imagine that manually flying formation would cause extreme fatigue due to the need to constantly fiddle with trim and yoke, and would be very dangerous. Or is this simply a case of actual pilots having actual training, instead of my amateur "training" of fiddling around in the simulator overusing instruments? <Q> Nope, pilots do not use autopilot to fly in formation. <S> An autopilot cannot achieve the precision required for flying formation (e.g. keep the wingtip aligned to that door). <S> Usage of autopilot would also hinder responses when an immediate correction is necessary. <S> You may refer to the TV episode Jet Stream and Blue Angle training videos on the internet. <S> From the pilot's perspective, the planes are always moving around, though in a confined space. <S> Continuous small adjustment is necessary. <S> From the ground, the small floating cannot be noticed visually because the observer is too far away. <S> P.S. <S> Based on my 17 years of experience with PC flight simulator, flying in formation in multiplayer is definitely doable, and can become second nature with practice. <A> Based on your question, it sounds like you are referring to fingertip. <S> In fingertip, yes you are correct, it is exhausting to stay in position for any extended length of time. <S> This is why it is not flown much (really only time is transiting through the weather, and even then you have radar trail and instrument trail). <S> Besides TAC (see below), the other position you'll find yourself in at times is route, which is a much more relaxed position but allows the formation to maneuver easier. <S> Tactical formations like offset (container), spread, wall, wedge, etc. are flown instead. <S> This relieves the wingmen of constantly having to focus on 1 and can handle other tasks such as clearing, sensor management, backing up lead, etc. <S> Having said that, I've always noticed flying formation in actual AF sims to be harder than the real jet. <A> Computers can be programmed to fly formation, but there are no autopilots in production yet that can handle it. <S> The industry is trying to develop it so that airliners can fly in a V-formation in the cruise, like birds, in order to save about 5% in fuel. <S> It would also alleviate congested skies if airliners could pair up. <S> This would need very accurate positioning sensors that also work at night and in 0 visibility. <S> The secret is to make small control adjustments. <S> One will be oscillating with large amplitude, but low frequency. <S> Learn to control it <S> (straight-and-level first of course) and slowly bring it closer to the lead a/c. <S> Your brain will recognize patterns of how to react to disturbances over time. <A> As far as fighter aircraft or small light aircraft flying as the wingman in formation, I agree with <S> that's been said in the other answers. <S> However, larger aircraft than these can fly formation, and in some cases autopilot use is a little more common than these answers might lead you to believe. <S> (Not so much if Lead needs to do lots of maneuvering, but if you're going a long distance straight & level, the autopilot can do that very precisely, leaving the pilot(s) free to devote attention to whatever other tasks may be required: communicating with AWACS/wingmen/Command Post/ground party/other flights, assessing the situation with regards to threats/weather/mission/whatever, eating lunch, etc.) <S> In the case of Aerial Refueling, it's fairly common for the tanker to be on autopilot, since this gives the most stable platform for receivers. <S> When the receivers are more nimble than the tanker, this isn't such a big deal; when the receiver is another heavy, it helps. <S> When the receiver is really heavy and performance limited, having a stable lead (i.e. the tanker) helps a LOT. <S> Beyond this, wingmen can also be on autopilot if the type of formation allows it. <S> If you're stacked 500' above and a mile behind Lead, crossing the ocean for the next several hours, there's no reason at all not to use the autopilot! <S> If you have the waypoints that Lead is using, you could even couple the autopilot to the FMC, and just adjust the throttles to maintain the desired spacing. <S> If not, then you manipulate the heading bug to keep the position you want left <S> /right. <S> At the point when you get ready to do something like airdrop or a formation landing, the autopilot will come off, but for a long, straight cruise portion, it's entirely usable.
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First, the lead aircraft has an entirely different task than the wingmen: his objective is to be a stable platform for them to maintain formation off of, and so for Lead to have the autopilot engaged is entirely possible in many scenarios.
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Why isn't the V flight formation being used for commercial purposes? The V Flight Formation has been found to be helpful in achieving greater fuel efficiency and range. Though it is currently used mostly for military purposes, what restricts it from being used for commercial purposes? <Q> This possibility has actually been studied and discussed (e.g. here , here , here ) as a way to save fuel costs, but there are several issues with implementing it today: <S> You need to schedule a number of aircraft all flying the same route at the same time for a significant amount of time <S> If different, competing airlines should participate in one formation <S> then they have to cooperate and be satisfied that no one is at a commercial (dis)advantage <S> A lot of work would need to be done on procedures and training (how does the formation form up, who takes the lead, how/when does the formation leader change, how are emergencies handled, what flight levels are used, what separation is required between formation and non-formation flights etc.) <S> Autopilots, software and other equipment would need major updates, which in turn requires re-certification <S> Having said all that, you'll notice that most of those issues are procedural, not technical. <S> In theory it's a viable approach, but turning that theory into reality would require a lot of work. <A> Formation flight is not allowed by the FAA when carrying paying passengers: from 14 CFR 91 : §91.111 <S> Operating near other aircraft. <S> (a) <S> No person may operate an aircraft so close to another aircraft as to create a collision hazard. <S> (b) <S> No person may operate an aircraft in formation flight except by arrangement with the pilot in command of each aircraft in the formation. <S> (c) <S> The core reason would be safety. <S> If any craft has a problem it needs to be able to get out of formation safely and pilots need to be trained for it. <S> Also flying at cruise requires the autopilot; however no current civilian autopilot can make adjustments to account for maintaining separation in formation flight. <A> As a passenger I wish: To have a good choice of flight times Not to have to wait a long time while other aircraft are unloading Not to have long queues Not to have my flight be delayed due to issues with another flight <S> The above does not sit well with 'You need to schedule a number of aircraft all flying the same route at the same time for a significant amount of time'.
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No person may operate an aircraft, carrying passengers for hire , in formation flight. All relevant regulations on separation, formation flying and so on would need to be reviewed and changed which in most countries means changing the aviation laws, and changing any law is usually a long, slow process
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Is the Mach number shown by an Air Data Computer considered a "true" Mach number? I am trying to find more information on "true" vs. "indicated" Mach number (not airspeed). I've found older fighter aircraft manuals online that have a conversion chart from one to the other, but the modern jets I've flown don't have such charts. During a recent flight at 41000 feet, at a Mach number of 0.81, a true airspeed of 476 knots was displayed on the EFIS. In the standard atmosphere, 81% of the speed of sound is 464 knots at that altitude. Sure enough, the actual temperature was some 13 degrees C warmer than the "standard" -56.5 C, hence the true airspeed of 476 knots instead of 464. But that leads me to believe that the Mach number I am flying is not really "true". The relevant flight manuals do not use the words "indicated" or "true" to qualify the Mach number. <Q> For subsonic aircraft the Mach number is normally measured from dynamic pressure and static pressure, very similar to the way calibrated airspeed is measured. <S> $$M_a=\sqrt{\frac{2}{\gamma-1}\left[\left(\frac{q_c}{p}+1\right)^\frac{\gamma-1}{\gamma}-1\right]} $$ with: $M_a$, the Mach number $q_c$, the dynamic pressure $p$, the static pressure $\gamma$, the ratio of specific heats (1.4) <S> If there is an error in the measurement of either the dynamic or the static pressure <S> both the indicated airspeed and Mach number will be affected. <S> Note that the Mach number has no direct dependency on temperature. <S> $$V_{TAS} = M_a <S> \cdot \sqrt{\gamma <S> R T_S}$$ with <S> $R$, the specific gas constant (287.05 for dry air) $T_S$, the static air temperature <S> The indicated true airspeed has a direct dependency on the static air temperature ($T_S$,SAT) also known as the outside air temperature (OAT). <S> The static temperature cannot be measured directly since the air will heat up on impact with the temperature sensor due to adiabatic compression. <S> Instead the total air temperature ($T_\mathrm{total}$, TAT) will be measured. <S> The relation between the measured total air temperature and the static temperature is given by: $$\frac{T_\mathrm{total}}{T_{s}}={1+\frac{\gamma -1}{2}M_a^2}$$ Since the measurement probe may not recover all the energy from the adiabatic heating a correction factor is introduced: $$\frac{T_\mathrm{total}}{T_{s}}={1+\frac{\gamma -1}{2}eM_a^2}$$ <S> This 'recovery factor' $e$ is determined empirically for the temperature sensor used. <S> The display on the EFIS will show the OAT, which may be slightly off if $e$ is not entirely correct. <S> This will also affect the "true" airspeed indication. <S> To conclude; anything indicated in the cockpit can contain measurement errors, regardless whether it is called 'indicated' or 'true'. <S> With the introduction of digital flight data systems the error correction tables have been moved from the manuals to the computer, which automatically corrects for them. <A> Mach is a number in relation to the speed of sound. <S> The speed of sound is solely dependent on the outside air temperature . <S> Hence unlike airspeed there is no such thing as 'indicated' mach. <S> $$ M=\frac{TAS}{a}$$ <S> $$ a= <S> \sqrt{1.4*288.15*T}$$ <S> Where $a$ is the speed in m/s of sound and $T$ is the temperature in Kelvin. <S> The old jets needed conversion charts since the true airspeed was not computed by computer and machmeters used a best estimate value limited by the error in pressure. <S> The following is from a USAF handbook on how the Machmeter works: <S> This document by Airbus also suggests you are looking the ratio of True Airspeed. <A> Indicated Mach is what your Mach indicator reads during flight. <S> True Mach is basically indicated Mach that has been corrected for pitot-static system position error and instrument error. <S> (Same as the difference between indicated airspeed and calibrated airspeed). <S> Position error is caused by the location of the pitot tubes and static ports on the aircraft. <S> This is due to the shape of the aircraft and the way the air flows around it. <S> Engineers try to locate them in areas where the error is at a minimum, but there's always some error. <S> The amount of this error is determined during flight testing and charted in the flight manuals. <S> Some more modern aircraft have software that will automatically compute their calibrated airspeed and true Mach number. <S> Most aircraft, however, still use indicated airspeed and Mach number. <S> Instrument error is the difference between a calibrated input to the Mach indicator and the actual reading it gives. <S> The Mach indicators I've worked with usually have a tolerance of +/- <S> 0.03 Mach. <S> So, for example, if a technician inputs a calibrated value of 0.70 Mach and the indicator reads 0.72, it's within limits. <S> Temperature has nothing to do with the way Mach number is calculated in aircraft flight instruments; however, temperature does affect true airspeed. <S> In your example, 41,000 feet, Mach 0.81 and temperature 13 degrees above standard (that means -43.5 degrees <S> C static air temperature) <S> , I calculate the true airspeed to 478 knots. <S> Your total air temperature was probably reading about -13 degrees C, right? <A> Equivalent airspeed is not speed at all. <S> It is dynamic pressure, indicated as speed at which that dynamic pressure would occur at sea-level standard conditions. <S> And indicated airspeed is equivalent airspeed plus measurement errors (calibrated airspeed is cleared of those errors, that can be effectively estimated). <S> So there is an indicated/equivalent airspeed and there is true airspeed <S> and they are different physical quantities. <S> There is no quantity that would be expressed as Mach number, but would actually have different physical significance. <S> So “Mach number” only has one meaning. <S> How it is measured and what are the errors is already well covered by the other answers. <A> It is not correct that on most aircraft including the newest Boeing, Dassault, bombardier products only display indicated Mach. <S> You do need to check your manuals. <S> Only the Gulfsteam aircraft display true Mach.
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The true airspeed is calculated by the ADC from the Mach number and the outside air temperature.
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How is the actual ground speed of an airliner measured? Do pilots have the "ground speed" information available? If so, how is the ground speed measured? Or do they rely on GPS info to calculate it? <Q> There are generally two ways of determining the ground speed from within the aircraft. <S> The first is by using an inertial navigation system. <S> This consists of a number of accelerometers and gyroscopes that measure all accelerations and rotations of the aircraft throughout a flight. <S> By mathematically integrating all measurements this navigation system is able to compute the speed and position of the aircraft at any time. <S> The accuracy will degrade over time but ground speed is usually not far off, otherwise position would be far off very soon. <S> The second method uses external radio signals. <S> These navigation beacons are widely available over most continents. <S> A navigation computer would select the right set of beacons and by analysing the rate of change of the beacon bearings / distances the aircraft's speed can be determined. <S> Modern navigation systems combine all these methods into a one solution. <S> GPS, inertial navigation and DME measurements are then fused mathematically together to obtain a highly accurate and robust position and ground speed. <A> Ground speed and ground track are available and are determined by GPS. <S> Comparing two GPS derived locations will yield a velocity vector and ground speed is its magnitude. <S> This is also how winds are derived -- the difference between airspeed and heading compared to groundspeed and ground track. <S> Note that availability varies by airplane and installed equipment. <S> Any modern airliner will have this info on a primary or secondary display. <S> Smaller general aviation aircraft with an technologically advanced cockpit will have this info as well. <S> Smaller general aviation planes with just a GPS unit will have access to the information but it may not be convenient to reference. <S> Those without even GPS will only be able to derive groundspeed from airspeed and reported winds with a flight computer manually. <A> A simple definition is: Ground speed can be determined by the vector sum of the aircraft's true airspeed and the current wind speed and direction; a headwind subtracts from the ground speed, while a tailwind adds to it. <S> Winds at other angles to the heading will have components of either headwind or tailwind as well as a crosswind component. <S> The issue with using GPS to determine airspeed is that a GPS does not know what the winds are. <S> Although, weather forecast data can provide approximate wind velocity (direction and speed), it is not precise enough for situations where a few knots makes the difference between life and death.
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Nowadays this is mostly GPS, but ground speed is also determined by using a number of VOR (VHF Omnidirection Range) and/or DME (Distance Measuring Equipment) stations.
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Why are contrails not visible from the cabin? If you observe a plane flying whilst on the ground, plenty of times you will see contrails: Why are they not visible from the plane itself when sitting in the most rear part of the cabin even by trying to look towards the rear of the plane fuselage? They seem to be quite close to the engines. Knowing that they form due to the heat, they should be seen quite close to the engine. <Q> The distance between the engine and the start of the contrail depends on: the engine type the temperature of the outside air the moisture content of the outside air. <S> Usually the contrails don't form before the tail of the aircraft, but in extreme cold or humid air contrails can be seen forming just behind the wing. <S> On larger aircraft you have a better change of seeing the contrail from inside the aircraft. <S> On the 747 you can often spot them for the window of the rear passenger door. <A> Contrails do not form due to heat, but in fact the opposite: cold. <S> They occurs when water from fuel combustion exceeds the saturation point of the ambient air. <S> As it is unable to hold more water it turns into water vapor instead. <S> This freezes at sub-zero temperatures into ice crystals and you end up essentially making a cloud. <S> Since the saturation point is connected to temperature (think mixing sugar in cold vs. hot water) <S> this happens a bit back from the fuselage when the exhaust cools down. <S> The point where this happens is dependent on the outside temperature and the existing humidity. <S> Under the correct conditions you can see contrails from the cabin , but usually they crystallize too far back to be seen. <S> See <S> this and this video for it occurring. <A> This is more a comment than an answer, but since I have a picture, I write it as answer. <S> But also note that the blast stream can be much lower than what you would expect. <S> In a two-engine aircraft, you have to look down from the upper edge of the window, and even then, the stream will be on the lower border of your field of view. <S> Of course, the stream of the outer engines of four-engine aircrafts will be more centered in your field of view. <S> If you are flying over a scenery with high optical contrast, you can recognize the blast as a sharply defined region where the view is very blurry, as in the lower right region on this picture: <S> This was taken from the last seat row of a A340 after takeoff at Chicago O'Hare, and you can see the blast of the outer engine. <S> (And yes, the outer stabilizer is in a little weird condition...) <S> So, look out for these blurry regions <S> , that's where contrails may form. <S> EDIT: (just for fun) <S> Coming home from vacation yesterday, I noticed another sign for contrails from your aircraft: The contrail's shadow: Unfortunately, the clouds became less dense when I made the photo, before I could also see a good shadow of the aircraft itself.
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It has alredy been written that contrails may form aside or behind an aircraft, so you may or may not be able to see them from the rearmost seats.
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Electric Airplane - Hybrid / dual type engines how would that work? If you have an airplane with electric propellers for take off and landing and you have a turbofan/jet to reach higher speeds for cruise.For example, electric propellers can go to 250mph and turbofan to 550mph Do you switch off the electric propellers or leave them on ? Do they work in conjunction ? What is the effect on the propellers when the turbofan reaches 550mph ? Is the thrust added if both engines are working ? <Q> The B-36 Peacemaker had 6 radial engines, driving 6 propellers, AND 4 jet engines in 2 nacelles . <S> The jet engines were used for takeoff and for "dash" over a target. <S> The jets were turned off during cruise because they used considerably more fuel than the piston engines. <S> As such, they HAVE made propeller/jet hybrid aircraft in the past, though not electric. <S> To answer your questions: You probably want to feather the propellers and kill the electric motors. <S> If the props can only drive you to 250 MPH, leaving them windmilling in the slipstream when the jets are running will add drag, which will only serve to hurt your cruise speed and/or increase your fuel consumption. <S> They only work in conjunction as speed BELOW what your props can drive <S> (eg 250 MPH, in your example). <S> Beyond that, if it's speed you're after, you're better off without the props. <S> At speeds above what the props can deliver, they're essentially small windmills. <S> And not very efficient ones at that. <S> See 2. <S> Now, what WOULD be helpful as a "hybrid" aircraft would be a gasoline engine, turning a prop, with an electric motor added between the engine and the prop. <S> In the event the gasoline engine failed, the prop/electric motor assembly could be declutched from the gasoline engine, providing you with temporary power to maneuver around and land safely. <S> Gasoline engines in aircraft tend to be very reliable, but when they DO fail during take-off or landing, the most vulnerable parts of the flight, the results tend to be catastrophic. <S> As such, the gasoline/electric hybrid would be of no use during cruise but it MIGHT improve the safety factor during the most vulnerable parts of the flight. <A> A hybrid just does not make sense on a plane for the same reason that a turboprops make sense on a plane and turboshafts do not for a car. <S> Cars have rapidly varying load, planes do not. <S> Also planes do not brake in the air (often), so regenerative brakes would be worthless. <S> Overall the electric motor in a hybrid car is in effect used to smooth out the load on the internal combustion engine, and allow it to run at its most efficient rpm. <S> In a turboprop, the variable pitch does the same thing, but much better. <A> I guess there's no current experimental evidence to answer the question about an airplane with an hybrid engine and an added jet engine, but there are some publications about hybrid airplanes, such as: 'A simplified method to calculate the fuel burn of a hybrid electric airplane', R Jagannath et al, in 50th AIAA/ <S> ASME/SAE meeting, Propulsion and Energy forum, 2014
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The electric motor could supply extra power during takeoff and function as a generator/dive brake on the prop during descent.
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What's the relation between cabin pressure and altitude? Usually, cabin pressure of an airliner is kept at a value corresponding to an altitude of not more than about 2000m. Now, I heard that before takeoff, the pressure is already increased a little for higher stability of the fuselage. Maybe, this is wrong, but I had another experience: I was in a 737-800 flying at 11500m. While the aircraft sank on approach for landing, I felt that typical pressure on my ears several times though we still were above 7000m. So, the cabin pressure already changed at that high altitude. So, how is cabin pressure related to outside pressure during the entire flight? <Q> Here is a plot of cabin pressure on one flight. <S> The decrease and increase in pressure is fairly constant during climb and descent. <S> The pressure will change based on the aircraft's altitude, and will not reach a minimum limit until closer to the aircraft's service ceiling. <S> This keeps pressure changes as slow as possible while giving a lower cabin altitude when below the service ceiling. <S> Source <A> On a number of aircraft types the cabin pressure is increased during the take-off roll, ensuring there is a slight over pressure when the aircraft rotates. <S> This prevents some sudden changes in cabin pressure during rotation when the cabin exhaust valve is exposed to changing airflows. <S> The chart in @fooot's post clearly shows the initial increase in pressure during take-off. <S> During the climb the cabin pressure is slowly decreased. <S> While a typical passenger jet may climb at speeds in excess of 2000 feet per minute, the cabin pressure will decrease at an equivalent rate of climb rarely exceeding 500 feet per minute. <S> When the cabin pressure has dropped to an equivalent of about 7000 ft altitude (the aircraft will be much higher by that time) <S> the cabin pressure is kept constant. <S> When the aircraft starts to descent on approach to the airport, the cabin pressure is slowly increased at about a rate of 300 feet per minute. <S> By the time the aircraft has reached the airport level, the cabin pressure should have reached ambient pressure. <S> To achieve this, pilots have to set the cabin altitude for landing, otherwise the pressure will not equalize. <A> To the best of my knowledge, cabins are never pressurized before takeoff. <S> This is a safety issue as it would inhibit door opening. <S> The pressure would make them impossible to open. <S> Depending on aircraft, the aircraft might be kept at either: <S> At a constant pressure difference, i.e. the cabin altitude increases evenly up to cruise altitude. <S> This would indeed mean that the moment it takes off it starts to build up a pressure in relation to takeoff. <S> This means that the pressure difference is perceived as gradual. <S> At a fixed minimum pressure, i.e. the valve just closes at (for instance) <S> 2000m <S> and then maintains 2000m altitude all the way up, just building an increasing pressure differential. <S> Both methods have to take into account the landing altitude, since you don't want to land the aircraft pressurized. <S> The former is more common since it's nicer. <S> This would also explain why you perceived a change even at high altitude.
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You can see a small increase in pressure right before takeoff.
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When a large commercial jet touches down, is it committed to stopping? I was reading about flight RWAF9268 earlier today when a questions popped into mind. When a large commercial jet touches down, is it required to try and come to a complete stop? Or is it allowed to take off again if part of the craft fails (like the braking system, for example)? And what factors would make a pilot decide to stay one the ground, or just abort the landing? <Q> When a large commercial aircraft touches down, it is not committed to stopping. <S> However, it is committed to stopping when the thrust reversers are selected . <S> This is because they take different time to stow and adding power while stowing would likely cause significant asymmetric thrust. <S> And even if they don't, they take their time to stow and you are unlikely to have enough speed and runway when they finally do. <S> When thrust reverses are not selected, the pilots of course have to consider whether it is more likely that they can stop or lift-off again on the remaining runway. <S> And they sometimes do choose to lift off. <S> There are many incidents where planes went around after tail or even wing strikes or bounces as it's often easier to get the plane under control by adding power. <S> But once thrust reversers are selected, stowing them again means loosing a lot of time and is risky, so go-around is considered out of question afterwards. <A> Boldface emergency procedures are procedures that the aircrew should have committed to memory and are written in bold text. <S> Generally speaking, the boldface for all emergencies involving brake failures, gear failures, control failures, literally anything that involves control of the aircraft after touchdown, starts with: <S> If fly-away airspeed available: 1. <S> Go-around <S> If fly-away airspeed unavailable: 2. <S> Do specific airframe related items. <S> Emergency procedures like these will be committed to memory, and then the only problem for the aircrew to solve will be if they have enough runway remaining to get airborne again. <S> If they don't have enough runway remaining then usually the fix to is apply emergency brakes (if the pedals hit the floor) or use backup nose wheel steering (for a steering failure) and ride it out. <S> Note: use of these emergency procedures doesn't necessarily indicate a failure of an aircraft system. <S> If a sudden gust of wind at touchdown weathervanes the aircraft 45 degree off centerline, you can be sure the crew is checking for fly-away airspeed. <A> However, a go around after touchdown is not an easy task and sometimes can be very dangerous. <S> A hypothetical situation is discussed here which is similar to Flight 9268 which you mentioned. <S> Compared to a landing, more runway is required for a takeoff. <S> After the touchdown, pilots have very little time to decide to take off again if they cannot stop. <S> Fortunately 1 , most of the time, this decision is made very quickly. <S> However, if an airplane is slowed down below the minimum safe go-around speed, there will (or may 2 ) not be enough runway remaining to take off again. <S> Therefore, pilots should accept a runway overrun, as it is probably a lesser evil. <S> To take off after a touchdown, there are several very important factors to consider. <S> They include: Remaining runway <S> Probably the most important factor. <S> If airplane is at or above minimum safe go-around speed, or can achieve with enough runway remaining Actual touchdown point Density altitude Wind Pilot reaction time (decision time) <S> Inertia of the airplane Time required to configuration change 1 : <S> In cases when the pilots decide to abort the landing, they decide it within the first few seconds of touchdown. <S> I found a video of this (and this one ) showing the airplane took off very quickly when aborting the landing (after the wheels touched down). <S> Most of the time, they abort the landing before touchdown, when the gears are just a few feet off the ground (as seen here and here ). <S> 2 : This depends on runway length.
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No, when an airliner touches down, it is not committed to stop.
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Will driving experience benefit flight training? I think my question/situation is a little bit of rare so I start this question and want to hear from you experience pilots. I'm a 30+ migrant from China working as a software engineer for 10 years. Now I use my weekends taking flight training for Private Pilot Licence in Sydney. Currently I don't see any big problem with my training and probably in next couple of weeks I will have my first Solo. What concerns me is my past experience. I can say I'm rather a good programmer and writing code for computer(iPhone) is really different from driving or flying. My flight instructor tend to say (and I agree) I always fly with the exact numbers rather than make necessary adjustment according to situation outside. So I guess with the past 10 years indoor in-front-of-keyboard office life/experience. The more you get your life/experience aligned with computer/coding, the harder you could get out of it. What's worse is I don't have any driving experience until two months ago I started to practice for my Australian driver's licence. Now I have my licence issued for one month and I still only drove four or five times with rented car. Though I love public transportation and I'm not that declined to own a car, now I start to thinking about the benefit of driving experience for my flight training. At least driving skills are accumulated with "hours" (which is the same as flying) and it will get me out of computer world. Do you have any suggestion or advice on this? Thanks for reading and replying. Cheers~ P.S. if possible, my target is CPL one day. <Q> I don't think driver training is beneficial to flight training, the physical acts of driving and flying are too dissimilar. <S> Driving is a handy skill to have for sure <S> , it's usually much easier to get to the airfield for one thing, it's not going to translate to flying though. <S> As for flying the numbers you are falling back on what you are good at: attention to technical detail. <S> Attention to technical detail is a very good thing in flying - having a plan and rehearsing for emergencies can save you neck. <S> What your instructor may be telling you is that you need to focus your attention to other details. <S> You may be spending too much time looking at your instruments and not enough looking outside. <S> I did this at first because I had spent a lot of time playing flight simulators <S> and I'm also in IT and spend a lot of time looking at displays in front of my face. <S> The cure is simple: force yourself to get in the good habits of looking outside the aircraft and developing situational awareness. <S> You can only get that through flying practice. <S> It sounds like you are concerned that you don't have a sort of instinctual "feel" for flying. <S> Everyone has a different set of aptitudes, some people are better at certain aspects of flying than others. <S> If there's an area you are weak in then focus your training and practice on developing it into a strength. <A> From my subjective experience, training pilots without driving experience is not a big deal, as long as it not an indicator of being uninterested in things technical. <S> (Remember, tons of people start flying gliders in their teens, before ever having driven a car). <S> What you are describing is the typical path of the flight student, and from the fact that you are concerned with making good progress: a motivated flight student. <S> Without training and experience, you can not expect yourself to intuitively <S> know what to do when you are "too low on base". <S> In fact, you can not even expect yourself to even know that you are "too low on base". <S> The only way to compensate for this, in the beginning of your training is by doing things "by the numbers" (ie, knowing what height you should be over the blue house etc) <S> (sort of like following an algorithm). <S> That being said, the most common (once again my subjective perspective) hurdle seen in new pilots with plenty of flight simulator experience is underestimating the importance of outside visual references (in practical terms: they don't trust their own ability to judge their attitude looking at the outside horizon. <S> For an educating experiment: Ask your flight instructor to oscillate the aircraft in pitch +/- <S> 1 degrees while you look only at the artificial horizon, then have the instructor repeat it, while you look outside, at the natural horizon, and make your own conclusions as to which is "the better" instrument. :) <A> My experience is the other way around: Learning to fly improved my driving skills. <S> This mainly in the field of trip planning and discipline of execution. <S> Remember, with a car you can always pull to the right (in Australia to the left) and stop. <S> With an airplane you do not have this luxury, so you learn to think ahead. <S> If you are comfortable with public transport, forget to get a car. <S> Driving is expensive. <S> But try to get behind the wheel every now and then to build up experience. <A> Driving experience helps in flying only by "curing" your reflexes. <S> Nothing else. <S> Some people are good at it, some people are not. <S> This does not come from how experienced a driver you are, but comes intrinsically from the fact "How good you are". <S> Many air-forces across the world have this test, and it is often claimed that one cannot gain this aptitude just by flying more. <S> You need to have this aptitude, and after that you can improve your flying skills by having more experience and practice. <S> Indian Air Force conduccts PABT
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You can have no driving experience and still be a good pilot, but there is a thing called "Pilot Aptitude".
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How is the D8 Double Bubble aircraft by NASA so efficient? How does the 'double bubble' fuselage cross-section of the " Double Bubble D8 " aircraft (developed by MIT for NASA) help improve overall efficiency by around 70%? Image credit: NASA/MIT/Aurora Flight Sciences <Q> The main advantage is its lower flight Mach number of 0.74. <S> This allows it to use minimum sweep, which in turn reduces wing area, structural masses and thrust requirements. <S> Now pick the right definition for efficiency (one that neglects speed), add the engine fuel consumption expected in 20 years, and the concept looks like a winner. <S> If fuel prices go to \$200 or \$300 a barrel, this type of aircraft will lower the cost of flying substantially. <S> The double-bubble fuselage will contribute only a little to the overall savings, though. <S> Most will come from the (hypothetical!) engines and the high aspect ratio wings with little sweep. <S> Note that the lower flight speed is compensated by the claim of much shorter boarding times <S> , so the double bubble comes out ahead in block times. <S> The only reasoning is that passengers will board more quickly because they can choose between two aisles to get to their seats. <S> Very questionable! <S> Below is page 105 from this report which shows the fuel consumption improvement of the separate steps from a Boeing 737 reference design to the D8.1 concept. <S> As it looks now, the marginal cost of fracking will keep oil prices below $70 for the next years, and airlines will keep ordering planes which look like those they operate today. <S> Looking through the proposals in the PDF linked in your comment, most of them make me cringe. <S> Since the Seventies we see the same concepts for supersonic travel, and here they are again, only presented in different colors. <S> Some subsonic designs are sound, but again we see hopeless concepts like the boxed wing which is kept alive by a stream of NASA grants, only because it looks so different. <S> I am equally skeptical of those blended wing concepts which pop up with every new generation of aircraft designers. <A> Looking at MIT's presentation , more specifically pages 13 - 15, they're counting on the fuselage being a lifting body , among other things. <S> For most aircraft, the fuselage encompasses the passenger cabin, cargo cabin, fuel tanks <S> etc. <S> and is designed to impose as little drag as possible in the process. <S> With a lifting body, the fuselage actually provides lift, instead of just adding minimal drag. <S> The concept is also counting on cleaner aerodynamics advanced, lightweight materials <S> higher-efficiency engines less wing area with the fuselage providing some lift, the lighter weight and less fuel needed for the projected mission, less wing area is needed All of these, in combination, provide the estimated 70% greater efficiency. <A> ( http://www.nasa.gov/topics/aeronautics/features/future_airplanes.html ) <S> The engines require less power, it requires less runway to take offon (about 5000 ft) flying shorter and more direct routes, for cost-efficiency. <S> Reliance on promised advancements in air traffic management such asthe use of automated decision-making tools for merging and spacingenroute and during departure climbs and arrival descents. <S> overall it essentially improves most aspects of the aircraft, (I have oinly listed a few things, their are loads more on the NASA website) <A> Their presentation on page 87 specifically covers reasons for the fuselage design. <S> Additional lift and more cabin room in a smaller fuselage seem to be the main reasons they give. <S> But there are a lot of other details in the presentation too. <S> But note: the fuselage shape is only part of the overall claimed efficiency improvements. <S> There are many other features such as a lower cruise speed, reduced sweepback of the wings leading to weight saving, etc.
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The biggest contribution is from lowering cruise Mach (and increasing cruise lift coefficient, which allows to reduce wing area) and from engine optimization.
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How similar/different are the roles performed by Military and Civil pilots? Broadly, Military and Civil are the only two categories in which the Pilots can be classified on the basis of the roles performed by them. What are the similarities and differences in tasks performed by them? <Q> The biggest difference is that most everything in commercial aviation is considered administrative in the military. <S> The tactical employment of our aircraft, the non-administrative portions of flight, is what separates military sorties from commercial flights. <S> This emphasis on tactical flying has also led to significantly different cultures between commercial and military aviation. <S> There isn't a commercial pilot I would stand a chance against in a game of FAR/AIM trivia, but I also doubt they'd fare much better if the tables were turned and the questions were related to carrier operations. <S> We are two separate organizations with two unique mindsets to flying. <A> As mentioned Commercial should really be "Civilian" which includes Private and Commercial. <S> Lets assume that military includes the various branches that employ pilots (Navy, Air Force, Marines etc). <S> In the end of the day everyone flies a plane... <S> A chunk of military aviation is devoted to combat related missions, this is something a civilian will never see (at least as far as I know). <S> This includes but is not limited to surveillance, escorts, combat and other military related missions. <S> I would think the tasks are very similar since moving people and cargo is moving people and cargo whether for the military or a civilian organization. <S> The military obviously had access to flying some planes that would be tough to get into as a civilian (fighter jets mainly). <S> One operation that Civilian pilots will never see is take off and landing on a carrier. <S> That is unique to Navy operations and as far as I know there is no way to do it as a civilian or even train for it (unless you can buy a carrier). <S> As far as regulations go the military aircraft and pilots are subject to military regulations (in terms of up keep and things like that) and must adhere to those rules which I believe are different in some cases than the FARs that govern US commercial and Private operations. <S> That being said, if flying in US airspace the same rules apply to military planes that apply to civilian planes. <A> Within commercial civilian flying the mission objective is to land safely at a destination. <S> In operational flying in a 'deployment zone' the mission is to do many other things before you land somewhere safely. <S> There are so many more factors to consider than just flying from A to B. Areas of recent combat, rising threats, low-level flight, areas where fighting is imminent, mountain flying, attempting to minimise the impact on local population when you fly over their houses/vilages/cities, proximity to other air-assets that fly in the same mission. <S> Just to name a few. <S> Even seemingly 'airline' types of transport in the military do have to consider many more factors during take-off and landing in a war-zone. <S> They don't come with missile self-protection systems for fun.
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The military operates troop transport and cargo planes much like commercial operations do and they have pilots who fly them.
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How is an aircraft aligned at a jet bridge? I see these jet bridges (or aerobridges) at nearly every new airport I go to. How are aircraft aligned with these bridges, particularly the A380 which has doors on both decks? <Q> How are aircraft aligned with these bridges <S> They are not (but read on) <S> Aircraft are aligned to a point on the concrete, not to the jetbridge(s). <S> It is the jetbridge itself that carries out the final alignment to the aircraft door. <S> Jetbridges are actually motor vehicles with wheels, tyres, motors and (often) steering. <S> It just happens that their rear end is tethered and their bodies articulate and/or telescope to accomodate the motion at the "front" end.. <S> You drive one using a set of controls at the end furthest from the terminal building <S> -jet bridge controls - driving a jet bridge <S> I believe some also have what is effectively variable height suspension like old Citroens <S> (except I imagine it is hydraulic or jack-screw). <S> The aircraft is driven to the terminal so the nose wheel follows a guide line and stops at a marking appropriate for the aircraft type. <S> Then the jet bridge is driven up to the aircraft door. <S> As the aircraft is gradually burdened with self-loading freight and sinks on it's suspension, the jetbridge metaphorically bends its knees so that the SLF don't trip up or fall into the aircraft. <S> That is, the jetbridge maintains alignment, the aircraft is pretty passive in the job of alignment. <S> I have to admit I didn't notice these jetbridge controls for many years as I was usually either busy rushing to my seat or busy rushing to the baggage reclaim. <S> One time there was a delay at the aircraft door that was long enough for my bored gaze to alight on the controls and for the thought to briefly wander across my mind - "I wonder what would happen if I pressed that ..." <A> The Aircraft aligns with the gate through ground markings, radar sensors and eventually ground operators signals. <S> Image <S> source <A> The bridge can move to an extent but the aircraft is driven up to a designated spot that is marked on the ground. <S> Here is a video of it all happening. <S> This can be also accomplished with someone on the ground directing <A> They align themselves with the stand guidance system Azimuth Guidance for Nose-In Stand (AGNIS) is a passive system which uses a system similar to PAPI lights to display red and green lights to indicate whether the plane is too far left or right. <S> An active system is for example the Honeywell Advanced Visual Docking Guidance. <S> A camera detect the airplane and changes the sign to guide the pilot to the correct place. <S> (image source wikipedia) <S> After the plane is aligned to the gate the jet bridge is maneuvered up to the plane's door.
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After the aircraft stops the jet bridge is aligned with the aircraft's door by an operator that commands the various bridge actuators (wheels, extension, rotation).
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Flare: low, slow, and uncoordinated? I'd like to rephrase the question: Often I forward-slip on final right right rudder. During this time, I use the ailerons to keep the aircraft headed down the center-line; the aircraft's bank varies slightly from left wing down, to right wing down. At some point during this procedure, I have right rudder in and a slight right bank. I believe this is a skid; Is this something I should worry about? I would very much like to avoid skidding at all times, especially on final! Previous question, for reference: Assuming there is a crosswind and the pilot executes a crabbed approach, during the flare the pilot is going to have to use the rudders to avoid a side-load. My understanding is that this will result in an uncoordinated flying condition and is prone to stall-spin. However, this (the flare) does not seem to be much of an issue among pilots. What am I missing? How is this any different than a skid? <Q> Crosswind landings are always uncoordinated. <S> I'm not familiar with big jets, but I believe they simply kick the rudder to align the nose with the runway and let the momentum carry it in the right direction until it touches down, but I might be mistaken here. <S> In a smaller aircraft (like a piston single) you're taught to drop a wing into the wind and effectively land in a side slip. <S> This is all perfectly safe, the dangerous situation you're talking about is a skidding turn, where you apply too much bottom rudder, letting the 'inner' wing slow down to the point of stalling. <S> This only applies to an actual turn however, if you're flying straight, coordinated or not, there's still more or less the same airflow over the wings. <S> You could however experience other aerodynamic effects where fuselage and airfoils effectively perturb the air for other airfoils and might cause a wing drop or pitch change, but it depends on the properties of the aircraft. <A> Basically it's not an issue because we don't get down to a speed where we need to worry too much about a spin. <S> It takes more than uncoordinated flight to induce a spin. <S> You have to have a stall first. <S> You don't stall as long as there's adequate airflow over the wings. <S> As long as you don't get below ${V_S}_0 <S> $ (with flaps extended) on both wings, even if you're cross controlled, you're okay. <A> Slipping during a descent is not particularly likely to cause a stall because both wings are are sufficiently unloaded that they're not likely to exceed their critical angle of attack. <S> Forward slips to a landing are, in fact, a very useful skill to have, especially for pilots flying very light singles (possibly without constant speed props or even flaps) and one that can allow pilots much more flexibility during landings and engine-out emergencies. <S> It's probably worth noting that this is a concern for normal landings as well. <S> In addition to that, even if you were to stall the aircraft while in a slip, the aircraft will snap towards the outer, raised wing, reducing the angle of bank (most modern light trainers will generally just return to a more or less wings-level attitude) and making for a much easier (and less harrowing) recovery. <S> A stall during a skid, by comparison, will snap the aircraft towards the inside, lowered wing, and put it into the incipient phases of a spin (and will usually do so in a far more violent and surprising manner than you might be expecting, even if you've spun that aircraft before). <S> This is a much more unpleasant experience (even in normally benign aircraft) and requires prompt and correct action in order to successfully recover.
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You do need to be careful not to flare too soon, as that might cause your airspeed to bleed off to the point were you will either begin to sink too rapidly and touch down hard or, in a really bad outcome, actually induce a stall and run the risk of losing control of the aircraft.
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How does take off mass impact induced drag? In this answer to another question, it was stated that: Take-off mass: If you take no payload, the aircraft will produce less induced drag and reach a slightly higher range How does a change of weight inside the same shaped container increase induced drag, since the air doesn't come in contact with the cargo? <Q> Induced drag is caused by lift. <S> (historically, Induced Drag was named "lift induced drag"). <S> And the drag associated to that lift also decreases. <S> The quoted statement is true, but "slightly" can be discussed. <S> Because the increase in range depends a lot on how much payload the aircraft could carry. <S> (If it's %50 of the max takeoff weight, the range could increase a lot). <A> For the same aircraft speed and an horizontal trajectory: When the aircraft is lighter, less lift is required. <S> To decrease the lift, the angle of attack needs to be reduced (said otherwise: the aircraft flies more horizontal). <S> A smaller AoA creates less induced drag. <S> Lift and drag coefficients as a function of the angle of attack are represented in the following diagram. <S> ( Source ) <S> The ratio <S> L/D <S> is also represented, with its maximum L/D max . <S> L <S> /D max is an economical angle of attack. <S> After L/D max , a gain in lift is at the expense of a larger increase in induced drag. <S> Side-effect of reduced drag: <S> The thrust can be reduced to achieve the previous speed. <S> The range is increased thanks to the thrust reduction. <S> For a more accurate representation of lift and drag coefficients against the angle of attack, and additional information: Lift and drag curves for the wing . <A> Two ways of generating more lift, which is needed to carry more weight: 1. <S> increase angle of attack. <S> 2. <S> Increase speed with same angle of attack. <S> Both create more drag, there for both require more gallons per hour to fly. <S> Because of higher AOA requirement for a given amount of lift at a given speed, a more heavily loaded aircraft will stall at a higher airspeed. <S> This is why, when taking off and landing, it is a good idea to know the stall speed for your weight, and add in your safety margin accordingly.
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If weight(mass) of the aircraft decreases, the lift required to fly the aircraft decreases.
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Can a plane with 2 sets of shorter wings fly? I am proposing a plane that has 2 short wings of the same size on either side of the fuselage (two in the front and two in the back). Rather than using the horizontal stabilizer to destroy lift, the wings in the back help create lift and adjust the pitch of the plane. One problem that I thought of is the wingtip vortex created by the front wing hitting the back wings. I'm guessing this can be resolved by placing the back wings higher than the front wings (from a front view of the fuselage). Could this work? <Q> What you are proposing is called a "tandem wing", and it's been done before. <S> A brief search should produce more than enough research papers about the advantages and disadvantages of this particular design. <S> The near-complete absence of multiple-wing designs in modern aviation should be a hint that the design has issues. <S> Unless you particularly need the advantages of the design more than the drawbacks, there's no particular reason to use it. <A> It would be able to "work". <S> The question is how well it will work. <S> A significant issue is that the most of the problems with wings occur where they join to the fuse, and where they end. <S> It's the middle part of the wing that works optimally. <S> So if you half the length of your wings and double the number of them you are giving yourself massively increased end effects... <S> As mentioned in comments, the dynamics of stability are also more challenging when you have two main wings producing lift. <A> First the answer to your question: Yes, it can. <S> The probably most popular tandem wing was the French "Sky louse" ( Pou du Ciel ), a design from the 1930's that was built in countless variations. <S> Mignet HM 14 Pou du Ciel <S> (picture source ). <S> The initial type flew with a motorcycle engine of 17 HP. <S> OK, the wings are not of equal size, but nearly. <S> Close enough to count. <S> But the type had issues due to the small distance between both wings. <S> Please read this answer for details. <S> And now please do me (and, hopefully, yourself) <S> a favor and see the "lift destroying" elevator with different eyes. <S> This lower lift (or even downforce) is only the consequence of static longitudinal stability , and both can easily be eliminated by shifting the center of gravity back to the neutral point of a configuration. <S> But if you desire to have some natural stability, you will need to accept "lift destruction" regardless of the configuration. <S> To paraphrase a popular song : Birds do it, bees do it … <S> … even educated flying wings do it, I might continue. <S> Canards, tandem wings, they all will use the rear part of their lifting surfaces less if they want to achieve static stability. <S> And the most efficient way of achieving it is by using the smallest surface of two for this lower lift. <S> This has the additional benefit that the "rear wing" will be entirely within the downwash field of the forward wing, so it will see less angle of attack variation than the wing and be in a uniform flow field. <A> There are many good reasons for a tandem wing, and a few bad ones. <S> A few responses mentioned influence factors from the forwards wing, that is not bad if it is designed in. <S> With any design, including flying wings, the "tail" is built into the rear (or rear portion) of the wing. <S> So a flying wing or canard will have more wing area than a 'conventional' plane of the same performance. <S> For efficiency, you want long slender wings. <S> If you made two long slender wings in tandem, you wind up making the chord (wing width) shorter, which put you into a lower Reynolds number which means higher drag, and your airfoil thickness is less, which means your spar height is less, which could mean a heavier wing. <S> On the bright side, your fuselage becomes lighter (weight being distributed more evenly) and you can build in stall resistance. <S> For some aircraft, like the Ligeti Stratos, you can join the wings to add strength (like a biplane). <S> Shorter wings means a higher roll rate, smaller wings could means better control in turbulance. <S> Tandem wings also offer control coupling to make things like translation without rotation possible. <S> Most of all, I just think it goods good. <A> Another point that was not brought up yet is the rotational center of the airframe - specifically pitch and yaw would require much more effort to rotate. <S> When you have single set of wings in the center of gravity, rotating the airframe takes less effort compared to when you have 2 sets of wings and center of gravity in the middle.
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Anything with a strong enough engine pointed in the right direction can fly :)
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What will the impact to GA be if DTC DUAT goes away? Data Transformation Corporation issued the press release below. FOR IMMEDIATE RELEASE DTC DUAT Contract Extension May 21, 2015 — Data Transformation Corporation, DTC DUAT which supplies the DUAT Service for the FAA for the past 25 years, has announced that it has been granted a 60 day extension by the FAA to continue to provide the FAA DUAT service. DTC DUAT has always been committed to making the DUAT Service better for General Aviation pilots by adding new features and services making it easier to get weather briefings and file flight plans. DTC would like to inform all of its users and third party vendors that we are fully operational and plan to continue operations during and after the 60 day period. DTC DUAT is pursuing alternative avenues to provide the DUAT Service capabilities to its users following the 60 day extension period. For more information on this topic or anything about DUAT, please contact our marketing manager, Doug Priestley, at (800) FAA-DUAT (322-3828) or by email at marketing@dtcduat.com. If the alternative avenues do not produce the desired results and DTC DUAT operations cease, what will be the real-world, day-to-day effects on general aviation? <Q> I think that there would be little practical impact, except for those people who are heavily invested in DTC DUATS specifically and have to switch to another system. <S> First, there are two DUATS providers: DTC and CSC . <S> Even if DTC goes away, CSC is still available, at least for now, and it provides exactly the same service as DTC (see this question ). <S> Second, Lockheed Martin Flight Service (LMFS) provides all of the information and flight plan filings that DUATS does, and also provides briefings with a human briefer. <S> So there is a completely separate alternative to DUATS available, although admittedly switching tools always has some cost in terms of time and learning at least. <S> For example, I use Garmin Pilot with CSC DUATS <S> but I could switch to DTC simply by changing the data provider option. <S> Some flight planning tools also support LMFS flight plan filing <S> and I guess that more and more will in future, if only for competitive reasons. <S> But if you use the DTC DUATS website directly and are very experienced and comfortable with it then switching to LMFS or anything else would have a learning curve. <S> But in the end, people won't quit flying or even cancel flights just because DTC goes away. <S> They'll just complain a bit, choose a new platform (probably LMFS) and get on with it. <A> There are many downstream companies that provide briefing services and flight plan filing using DTC or CSC DUATS, and the ones using DTC may have some trouble transitioning to another provider of data. <S> My impression is that more of these downstream vendors are with CSC and will not be interrupted. <S> For example my company, ENFLIGHT.COM (which provides the time-saving value added service of personal minimums briefing on top of a DUATS briefing) relies on CSC as the back end. <S> Lockheed Martin is also heavily promoting interfaces to allow downstream companies to provide value added services on top of flight service data and connectivity. <S> I know a number of companies are developing interfaces to Lockheed, at the very least to avoid having all their eggs in one basket. <A> I believe those of us that found DTC to be the best of the three will be disappointed in the other two. <S> I miss DTC already. <S> Lockheed Martin, to me, is as primitive as the Flight Service tools I used for 13 years as a briefer for the FAA. <S> CSC is not much better. <S> Recently CSC e-mailed me and said they were not interested in any of my negative comments about their system. <S> (They were suggestions). <S> If there is a commercial briefing system I can afford I would consider it over these two! <S> If we could follow the money trails from lobbist and not allow non-aviation oriented quota hires to make decisions in the FAA DTC would have easily won over the other two! <S> I fly only VFR these years, Bonanza, and rarely at night. <S> I rarely fly to new places and have routes I have flown for years. <S> DTC made briefings to and from these easy to obtain, read and understand. <S> I was very happy with DTC.
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I assume the main impact would be on people who use DTC DUATS as their primary flight planning and filing tool and use it directly, rather than via another tool.
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Why are Low Cost Carriers ordering several hundred aircraft? Indigo is a low cost carrier, which already has 99 A-320s in its fleet has ordered 431 more. This airline currently covers 35 routes, while the full service carrier Emirates has 221 planes, and covers a fancy 164 routes. In its home country as well, the biggest player Air India has 102 planes and covers 95 routes. So, what are these LCCs planning to do with so many aircraft? Renting could be an idea, but you just do not go for renting as much as 4 times of your crew size. Similarly, AirAsia has ordered 304 A320s, EasyJet has ordered 100 A320s, RyanAir has ordered 100 B-737. Norwegian has ordered 100 A320s, 100 B737, <Q> Volume Orders Discounts <S> These result in significant discounts to the airline. <S> While discounts are commonplace in the industry, Ryanair ordered 737-800 for an estimated 40-50 million dollars as compared to the list price of around 90 million dollars. <S> With an order of that size Boeing could not risk losing it to another manufacturer, and will be satisfied with less profit per aircraft. <S> Source Fleet strategy: <S> Some airlines sell their old aircraft after only a few years while their value is still high but the maintenance costs start to increase. <S> Increased maintenance is bad when you try to squeeze out as many flights as possible <S> and you have small profit margins on every flight. <S> You can find some of Ryanair's old aircraft by the company code (AS) with other operators by searching 737-8AS. <S> Another suggestion is that the customers perception of Low-Cost airlines is generally negatively biased and having new aircraft counters this effectively. <S> Old Aircraft <S> Some operators (such as charter operators) will not have the same sensitivity to a slightly higher fuel consumption on their aircraft. <S> They may not use their aircraft the same number of hours, so having an increasingly expensive jet sitting on the ground is not cost-efficient. <S> The aircraft ordered by IndiGo are all new fuel efficient A320NEO. <S> Some of these ideas are emphasized in your link. <S> Of its 530 orders from IndiGo, Airbus has so far delivered 99 aircraft. <S> The airline currently has a fleet of 83 planes and has phased out 16 planes that were over six year old or among the first in its fleet. <S> A bit of Ryanair strategy is outlined in this document . <A> It might be that Times of India are over-reporting the actual orders. <S> The aircraft industry has various types of orders and options. <S> Other sources ( pdxlight ) say that Indigo has firm orders for 180 A320neos. <S> If Indigo replaced their existing A320s this would represent a doubling of their fleet size - still surprising but less so than the five-fold increase from 99 to 530 suggested. <S> Indigo have also signed a memorandum of understanding for 250 aircraft . <S> This isn't a firm order. <S> Indigo claim " The additional aircraft will enable us to continue to bring our low fares and courteous, hassle free service to more customers and markets and will create more job opportunities and growth." <S> - presumably if their ambitious expansion plans do not work out as expected, this MoU will not be converted into firm orders. <S> There have been reports of an IPO for Indigo and other sources of funding. <A> Outfitting an airline with a single, modern type will yield the lowest operating cost once financing of the acquisition is secured and crew compensation stays low. <S> Now the investor needs only some patience, and after a few years of losses he will be able to reap monopoly profits. <S> This, at least, is the strategy behind such big orders of a single type. <S> By ordering large volumes, the airline can secure the highest possible rebates (up to 50%). <S> This strategy is very similar to that of car rental firms which also buy cars in large volumes and with substantial rebates in order to sell them after some months <S> (years in case of airlines) for more than they paid for them. <A> In addition to these wonderful points about getting a lower price for a mass-order, there are lots of unforeseen upsides to having a fleet of only a SINGLE type of (modern) airplane: <S> New planes live very long New planes are more fuel-efficient than older ones <S> If there is only 1 type of plane it is very straightforward swapping out a plane if one requires repair <S> Aircrews only need to be trained & Certified for a single type of plane Ground Crews Pilots only need to be trained & certified for a single type of plane <S> - This is a Big One. <S> Afaik if an airline also has e.g. a Very Large Plane, the pilots need to be especially trained for that one, which does less routes than the smaller ones, which makes it a less cost-effective endeavour <S> Source:
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This, together with the rebates connected to a big order, enables the airline to win any price war with its local competition, because its aircraft will consume less fuel and will be profitable at lower seat-mile prices than those of a competitor which operates a mixed fleet of different types and older aircraft.
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Why do some fighters have two engines and other have only one but still give the same performance? The F-16 , F-35 , and Gripen have single engines. On the other hand, the Ching-kuo (Taiwan) and F/A-18 have double engines, but the combined thrust of two engines is almost equal to the single engine thrust. Why do some aircraft use double engines? <Q> Some countries don't get the most powerful engines and have to use what is available in the market. <S> To avoid upsetting China too much, the US would not sell the F404 or the F100 to Taiwan, and a derivative of a civilian engine had to be developed. <S> A second reason is redundancy: When the US Navy had to decide between the F-16 and what was to become the F-18 , they preferred the design with two engines, because losing your only engine over water is a much more life-threatening experience than losing it over land. <S> Similarly, the Eurofighter was designed more for peace than for war - having two engines will reduce training losses. <S> Single engines need to have more system redundancy than one of a pair of engines, so some of that advantage cannot be transferred into the finished design. <S> Nevertheless, from a performance standpoint the single engine fighter will look better. <A> Very early jet engines weren't particularly powerful; it took two in most cases to equal (or slightly exceed) <S> the performance of a single big V-12 or large radial. <S> The next generation was more capable; most fighters in Korea and many in Vietnam were single-engined. <S> Some exceptions were quite large – the F-4 Phantom and <S> (R)A-5 <S> Vigilante come to mind. <S> The more combat load required, the more thrust, and a single engine able to power an F-4 Phantom would've likely been quite large . <S> Modern engines are much more capable; it mostly comes down to the desires of the operators. <S> A single engine requires less maintenance (although probably not half) than a twin-engine aircraft. <S> It is also more susceptible to mechanical failures or combat damage. <S> The need for larger combat loads, redundancy, and —in some cases— excess performance are probably the primary reasons that not all modern fighters are single-engined. <A> Number and placement of engines is one of the initial trade-offs that a scratch-built aircraft design deals with. <S> There are several criteria for the trade-off of the basic configuration. <S> Here are a few: <S> Thrust-to-AircraftWeight Weight penalty Aircraft Performance Stability/Control (agility) <S> Survivability Reliability <S> Maintenance intervals <S> Time-to-replace Safety Inlet configuration (if it's down the aircraft, then FOD problems show up) <S> Stealth (a single engine is bigger than two smaller engines (more exhaust area)) <S> Cost of engines Cost of aircraft <S> Provisions of the platform (to add future capabilities, and robustness to design changes) <S> These and several other criteria (esthetics, marketing, etc) are used to judge the different configurations, and then one of them wins. <A> This question is pretty complex and has to do with several factors Design performance criteria - what are the specifications for the airplane's mission, flight envelope, onboard mission systems, payload, etc. <S> Available engine technology - performance criteria are largely limited by this factor. <S> Power plants are developed in parallel with aircraft programs, often beginning 1-2 years before development on the plane begins. <S> Military fighters tend to favor a single engine arrangement for power to weight and specific fuel ratios which favor energy maneuvering. <S> But performance requirement such as large combat radii or mission systems and stores carry combined with engine limitations often make a multi engine design attractive. <S> System redundancy is a tertiary benefit of multi engine aircraft, since losing an engine results in only a 50% loss in total available thrust plus redundant generators and hydraulic pumps to allow the aircraft to continue to fly. <S> This is alleviated somewhat with APUs or EPUs Un single engine fighters which do provide electrical power and hydraulics but no additional emergency thrust. <A> In war time, one engine or two engines is immaterial. <S> In peace time, the number of engines is quite important. <S> I had two engine failures during my military career: <S> one of the aircraft I brought home. <S> Following engine failure on the other, the aircraft and I returned to earth separated in time and distance. <S> So, if you envision your airforce operating during peace time for the majority of the life of the aircraft, you'll want to protect your assets from unnecessary losses, especially if you have finite resources.
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Generally, a single, bigger engine will be more powerful and more efficient per unit of mass, because manufacturing tolerances will be relatively smaller in the bigger engine, if the same technology is used for both.
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What types of air traffic controllers are there? I've heard of many different types of controllers, but I'm not sure exactly what their responsibilities and interactions are. Here are some examples: En route controllers Approach controllers Ground controllers What types of controllers exist and what aspects of a flight is each one responsible for? <Q> In Canada (and I believe similarly in the United States), there are four ratings which can be applied to an Air Traffic Controller license: Airport Control Terminal Control <S> Area Control Oceanic Control <S> Within each of those ratings, the responsibilities are sub-divided a bit based on operational needs. <S> For example, controllers at a tower (with an ' Airport Control ' rating) would tend to be qualified in all aspects of tower operations including: Clearance Delivery (issuing IFR clearances or assigning transponder codes) Ground Control (issuing clearances for aircraft to move to/from the apron and runway areas via a taxiway system Air Control (issueing clearances to aircraft in the runway environment and in the vicinity of the airport) <S> Terminal Controllers <S> (if a terminal control area exists around the airport in question) would be responsible for flights in the immediate vicinity of the airport to approximately 20-50 nautical miles. <S> Their responsibilities may include multiple small airports, just a single large airport, or even just one specific operation at an airport (such as arrival control or departure control). <S> These controllers are usually allowed to apply a smaller amount of lateral separation between aircraft due to the dense nature of the terminal environment and the specific nature of their role. <S> Once the aircraft leave the terminal (if one exists), the Area Controller -sometimes called <S> enroute control-takes over. <S> They are responsible for anywhere between several hundred square miles of airspace to over several thousand square miles in the case of sectors in northern Canada. <S> In the case of an aircraft transiting the ocean, a specific type of area controller called an Oceanic Controller takes over. <S> They possess slightly different training in order to safely separate aircraft over the ocean in non-radar airspace. <A> You can find a nice summary here on the FAA website or here on Wikipedia But generally speaking, <S> At an Airport (and this very much varies by airport size!) <S> Note: if there is no tower at an airport <S> (the case for many small airports) aircraft must self announce on the UNICOM Frequency . <S> It should also be mentioned that some airports have towers that are only in operation some hours of the day, they are considered (if open) un-towered at other times. <S> There could be a designated ground controller who deals with traffic form the ramp to the runway (at KPNE where I fly the tower handles the ground operations during low load times). <S> They will also handle the movements of other things like plows and service vehicles that may be active on or near the runway. <S> There may be Flight Data/Clearance Delivery who will give the planes their routes before departure (or any taxiing) <S> Terminal Controllers handle traffic in the radar terminal area (30-50 miles) from an airport. <S> Enroute Controllers provide information to airplanes in the air such as IFR instructions or VFR Flight Following (Load Permitting) <S> You can find the frequencies for the various ATC bodies in the Airport Facilities Directory. <S> You can even listen in live to see whats going on at lots of major airports. <A> In Europe, an ATCO license contains the following: <S> One or more ratings <S> One or more rating endorsements <S> One or more unit endorsements <S> One or more language proficiency endorsements <S> A medical certificate <S> An ATCO certificate shall contain one or more of the following ratings : <S> ADV - Aerodrome visual (tower control without use of radar) <S> ADI - Aerodrome instrument <S> (tower control with use of radar) <S> APP - Approach procedural (approach control without use of radar) <S> APS - Approach surveillance (approach control with use of radar) <S> ACP - Area control procedural (area control without use of radar) <S> ACS - Area control surveillance (area control with use of radar) For each rating, <S> the following rating endorsements are available: ADV: <S> None ADI (at least one rating endorsement required): AIR (Air Control) <S> GMC (Ground Movement Control) (without ground radar) <S> TWR (Tower Control) <S> GMS (Ground Movement Surveillance) (using ground radar) <S> RAD (Aerodrome Radar Control) <S> APP: None APS (may have one or more rating endorsements, but not required): PAR (Precision Approach Radar) <S> SRA (Surveillance Radar Approach) <S> TCL (Terminal Control) <S> ACP (no rating endorsements required): OCN (Oceanic Control) ACS (can have one, but not two, rating endorsements): OCN (Oceanic Control) TCL (Terminal Control) <S> In addition, an ATCO will need a unit endorsement , which is the authorisation to provide air traffic control service for a specific sector, group of sectors and/or working positions under the responsibility of an air traffic service unit. <S> Basically, a certification that you know the local regulations at the unit you are working at. <S> A language proficiency endorsement is also required in English and, if applicable, in the local language if required. <S> Furthermore, there are instructor ratings available, but I think that it beyond the scope of your question. <S> Then of course all controllers need to hold a class 3 medical certificate for their ATCO license to be valid. <S> As you can see, with the number of ratings and rating endorsements available, there are a lot of different possible combinations. <S> So the answer to "what types of air traffic controllers are there?" is not a simple one. <S> Regardless, I hope the above gives you a general overview of how ATC licensing is structured in Europe. <A> The previous answers detail the air traffic controller types and their roles very well. <S> However, I find this diagram quite helpful to visually recall the airspace divisions. <S> ACC: <S> Area Control Center <S> APP: Approach/Departure Control <S> TWR: Tower UTA: Upper Control Area CTA: Control Area TMA: Terminal Control Area <S> CTR: <S> Control Zone
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There may be a Tower controller (if there is a tower): who deals with airplanes on, to and from the active runways.
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What is meant by a "congested area of a city/town/settlement" in FAR 103? FAR 103 .15 states: No person may operate an ultralight vehicle over any congested area of a city, town, or settlement, or over any open air assembly of persons. I'm wondering what is meant by "congested area". It sounds like you can fly over a city, town or settlement so long as it's not congested but...how is that defined? <Q> I could not find a definite definition of congested area . <S> As mentioned here : <S> [...] neither the FAA nor the NTSB has ever provided [...] <S> a precise definition of [...] a "congested area. <S> " <S> Rather, a "congested area" is determined on a case-by-case basis. <S> According to the Board, "the determination must take into consideration all circumstances, not only the size of an area and the number of homes or structures, but, for example, whether the buildings are occupied or people are otherwise present, such as on roads." <S> The same is echoed here : <S> [For the definition of congested area,] FAA and the NTSB have opted for taking a "case-by-case" approach in determining how to apply certain terms. <S> AOPA states that : Congested areas . <S> " <S> Over any congested area of a city, town, or settlement, or over any open air assembly of persons, an altitude of 1,000 feet above the highest obstacle within a horizontal radius of 2,000 feet of the aircraft." The FAA does not define congested area in the FARs or in the Aeronautical Information Manual. <S> Interpretations in low-flight enforcement cases are not consistent for purposes of drafting a precise definition. <S> Such a determination is usually decided on a case-by-case basis, and in the cases that we've seen, congested has been interpreted rather broadly. <S> For example, a highway with moderate traffic was found to be "congested," as was a seaside area where 200 to 300 persons were sitting on the beach or bathing in the water. <S> The same can be seen here , and here , and here . <A> It is not explicitly defined in the FAR Definitions and it seems the explicitly do not define it. <S> I would interpret ( please keep in mind <S> this is my interpretation and not law ) <S> a congested area/assembly of people, as anywhere you could not safely land the aircraft in the event of an emergency without endangering others and or yourself. <S> This may better by explained with an example. <S> Lets say you are flying low over main street at rush hour, your engine goes and you are forced to make an emergency landing. <S> You have limited distance and direction to go and can not safely land the aircraft with out hitting either a building, people or vehicles on the road thus endangering them. <S> With that being said, you are correct that class B generally lies around the big cities in this country, and other cities may reside in class C, you can still have a congested area or open assembly of people (concert, state fare etc) in class G airspace. <A> If a regulatory authority does not define the word, then by default it is the common definition of the word. <S> Un-congested vs congested. <S> Think of the phrase Open space and occupied space. <S> If you are flying over open land it is un-congested. <S> In reality, the FAA uses many words and phrases with out providing what their definition is and leaves it to the common understanding rather than a unique definition. <S> Simple English...but not to those who push the limits. <A> While getting my Aerospace Engineering degree a "Regulations and Legal Interpretations" class was mandatory. <S> As part of that we studied cases against pilots such as flying low over farm houses. <S> The judges have been persuaded to accept 2 or more people as "Congested" or an "assembly" based on existing automobile traffic laws that fines people for violating speed limits for crowds or people (plural). <S> For example, "when children (pl 2 or more) are present" . <S> Take this at face value. <S> I don't agree with it <S> but it seems to be a case where the Government feels more successful by being vague then being reasonable. <S> To me something like "more than 25 people in a 1 mile radius" would be more quantifiable. <A> You can fly over a city which is congested, by following railroad tracks, etc, those areas are uncontested. <S> But, you must be in class E or G airspace, unless you have clearance from the controlling agency. <S> The FAR 103.11(b) is only for flying with strobes, during civil twilight. <S> You must be in uncontrolled airspace, which is class G, generally, but not always, starting at 700 or 1200 feet AGL. <S> Where I live ..0-500 feet is class G and <S> class B starts at 500' ago. <S> So I could fly my ultralight at 400', 20 minutes after sunset, along railroad tracks thru a major city. <S> A bad decision is called pilot error, your job is to keep others safe from your stupidity. :)
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If flying over occupied homes or businesses it is by definition congested.
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Do modern aircrafts like 747/787/A320/A380 have some Plug and Play subsystems/sensors? Do modern passenger aircafts like 747/787/A320/A380 have some sub-system or sensors which are plug and play that might include some kind of sensors or radars which comes as optional and can be used plug-play as and when needed as per the requirement? <Q> It wouldn't make much sense. <S> This would mean that if the device is physically fitted, but not in contact with the main avionics -- say, a wire might have broken or shaken loose recently -- then the cockpit instrumentation would look exactly as if it had never been there. <S> This is not desirable: when something the pilot thinks will be available for the flight isn't actually available you want to tell him explicitly so he can decide whether the problem needs to be planned around or reacted to. <S> Of course there are limits to how much the plane can itself verify that it is whole and in working order <S> -- that's why there are preflight checklists. <S> But to spend engineering effort specifically on allowing it to fail silently when communication with one of the sensors is lost, that would be counterproductive. <A> I will answer this from a US FAA regulations stand point, but you really have 2 questions here <S> Do modern passenger aircrafts like 747/787/ <S> A320/A380 have some sub-system <S> The answer to this in certain ways of looking at it is yes. <S> Modern glass cockpit style aircraft use ARINC Data Busses to transfer the data from the sensors to the main flight computers. <S> Depending on how you define subsystem one could argue that this data bus is in a way a sub system. <S> I am not positive on how to actually set one up and if the devices simply plug into it and self registers or need to be manually installed and programed some how <S> but there are sub systems on large planes that share resources. <S> ...plug and play that might include some kind of sensors or radars which comes as optional <S> There are lots of requirements around aircraft instruments and the way I understand them there <S> really is not a lot of "optional" stuff. <S> There are with out a doubt redundant things and backup systems. <S> With this in mind there are some systems like auto pilot that if it was not working the plane is still more than capable of flying. <S> But as for critical flight instruments even if they are plug and play you don't really have the choice of not having them. <S> On a bit of a side not Aspen Avionics has recently released an all software AOA indicator that runs in their glass cockpit system. <S> This was traditionally done with a mechanical device like this one that Garmin makes . <S> Im not sure I would call the aspen unit plug and play as there is no physical device to plug in <S> but it is a software plug in situation for their units and worth the mention. <A> Plug and play is a standard developed by IBM and Microsoft around the time windows 95 was released. <S> The old Plug N Play standard is an attempt to make device discovery and configuration a zero touch process for end users. <S> The PNP standard has moved on since that time, however I could imagine some computer devices in the avionics bay utilizing USB, ISA busses to communicate and may very well comply with PnP standards of some type. <S> The only key component really missing is the User and the Windows operating system. <S> So while discovery and auto-config, conflict resolution Plug N play protocols maybe present in the electronics onboard an aircraft, but likely not in support of the windows operating system. <S> In comparison to the PC based hardware bus systems, ARINC version 573 is the base level of functionality required from onboard data busses. <S> Compliant equipment can communicate while allowing the FDR to capture the data. <S> More modern standards in the 600 <S> + families of standards/products are designed for more modular treatment of the aviation equipment. <S> Very similar to telecommunications rack equipment has developed since moving to digital. <S> With modular systems based on a chassis providing comms services and power to add in cards of different capabilities and purposes. <S> Also integrating with other separate devices that integrate via ethernet or other standard protocols to deliver the necessary services. <S> Telecoms and ARINC is a reasonable comparison both in form factor, technical requirements and practices. <S> ARINC for example utilizes Harvard biphase encoding of data, pioneered in telecoms to avoid signal state corruption. <S> So in short, plug n play doesn't exist at least in standards on aircraft as a consumer would expect PnP to be. <S> Device, Windows OS, hardware interface and zero touch attempt at config the device.
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By definition "plug and play" would means that the avionics automatically and silently adapts to whether whether the optional device is present or not.
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What is the standard procedure in case of inconsistent sensor readings? After reading the answers I now know there are three independent sensors. I will leave the question as-is, to not take the answers out of context: I do remember reading that airliners have two independent sensors and channels to deliver readings like airspeed and altitude to the cockpit (pitot-static system). If this is not the case my question will not make sense. If the two systems show conflicting information, what is the standard procedure? If one of them is 'overspeed' or close to stall speed should the pilots assume this is the one to focus on? Or do the pilots reason based on each situation independently and all the other factors at play? <Q> The procedure used would depend on which information is conflicting/unreliable (and of course the aircraft type). <S> With one or more unreliable airspeed indications (which is one of the more critical ones), the initial action is NOT to start troubleshooting/figuring out which indicator is "the correct one", but to ensure safe speed/flight path by other means. <S> The initial actions on Boeing aircraft is to disconnect automatics (auto throttle, autopilot, flight director) and control the aircraft given memorized combinations of pitch and thrust. <S> If a reliable source can not be determined, the aircraft continues to be flown by pitch/thrust settings given in the manual (based on altitude, if known, weight, flaps/gear, desired vertical profile etc). <S> A big caveat is that if the transponder is set to use an unreliable static pressure source, the altitude that ATC sees on secondary radar will also be unreliable. <S> An example of this was seen in the Aeroperú 603 accident, where the aircraft took off, with the static ports taped over, and ATC was asked to assist with altitude and speed information: CVR transcript - Wikipedia Erroneous airspeed/altitude indications often imply each other, as an unreliable static pressure source will affect both. <A> There are at least three systems. <S> You compare indicators with the standby system and know which one of the main systems failed. <S> Sometimes all systems can fail due to icing or bird strikes. <S> In this case there is an unreliable air speed procedure or checklist. <S> Basically aircraft is flown by pitch and power settings. <A> Avionics computers are generally (if not always) <S> triple redundant to avoid the very situation you bring up. <S> Form a pure logic standpoint you cant know which reading is correct if you only have 2 readings in a blind situation. <S> However if you have 3 readings, 2 in agreement and 1 that differs you can statistically assume that the 2 agreed readings are correct. <S> There is a nice summary here on Wikipedia . <S> This Question <S> on why there are multiple autopilots also addresses it nicely.
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With the aircraft under control, and when directed by the checklist, you start analyzing the situation, to see if you can rectify/isolate the faulty source. In the case of unreliable altitude, in case you can't determine a reliable source, you can typically use radio altitude below 2'500 ft.
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Do fighter jets experience a reaction or recoil force upon firing a missile? When fighter jets fire a missile, do they observe any kind of reaction force due to firing the missile? If yes, how is this observed by the pilot? If no, why not? <Q> No, rocket missiles are recoil-less weapons. <S> When firing a gun, the charge burns inside the chamber and the generated gasses do not escape before the shell leaves the barrel, so the reaction force is transferred to the body of the gun. <S> This is true for missiles launched from tube (like Bazooka , TOW or Hydra 70 ), off a rail like the wing-tip sidewinders or from free fall like most of the heavier air-launched rockets. <S> The lack of recoil is an important advantage of rockets. <S> Bazooka can be fired from shoulder while anti-tank gun with comparable explosive charge is heavy device and needs good support to handle the recoil. <S> On the other hand rockets need more propellant than comparable gun shells, because the generated gasses leaving at high speed carry away a lot of kinetic energy most of which would be available for the shell in a gun. <A> http://youtu.be/9DYsYKFNSHo Ignore <S> the actual purpose of the video and why the pilot is firing in the first place. <S> You can clearly see that the missile separates from the aircraft before igniting the thrusters. <S> Since the missile starts its thrusters without contact to the aircraft, no recoil is experienced. <A> In some early jet fighters such as the F94 Starfire, air to air unguided rockets were carried in launch tubes that were built into the aircraft structure and closed at the rear end. <S> Launching the rockets could produce enough recoil to cause serious control problems, and this type of armament fell out of favor as a result.
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When firing a rocket missile however there is open space behind he missile and the reaction force only accelerates the generated gasses that are ejected off the back and does not affect the launching platform significantly.
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What callsign would a medical emergency flight use? I see medical emergency helicopters taking off and landing several times a day from the hospital near my office. As I understand from an earlier question, they are probably flying VFR, below controlled airspace and likely without ADS-B . I would assume, however, that these flights are in touch with the local ATC, and they are certainly announcing their presence on the locally monitored channel(s). Is there a particular set of call signs or other indicators that are used by these flights to indicate to other traffic that, while this flight itself is not in any sort of mayday situation, it needs priority handling and that everyone else needs to get out of the way as lives depend on the speed of this particular flight? I am asking particularly for the USA/FAA, but would be interested to know if there are differences in other countries around the world. <Q> The variety of callsigns used for medical flights are covered in the AIM 4-2-4 : b. Air Ambulance Flights. <S> Because of the priority afforded air ambulance flights in the ATC system, extreme discretion is necessary when using the term “MEDEVAC.” <S> It is only intended for those missions of an urgent medical nature and to be utilized only for that portion of the flight requiring expeditious handling. <S> When requested by the pilot, necessary notification to expedite ground handling of patients, etc., is provided by ATC; however, when possible, this information should be passed in advance through non−ATC communications systems. <S> Civilian air ambulance flights responding to medical emergencies (first call to an accident scene, carrying patients, organ donors, organs, or other urgently needed lifesaving medical material) will be expedited by ATC when necessary. <S> When expeditious handling is necessary, include the word “MEDEVAC” in the flight plan per paragraphs 5−1−8 and 5−1−9. <S> EXAMPLE− MEDEVAC Two Six Four Six. <S> Similar provisions have been made for the use of “AIR EVAC” and “HOSP” by air ambulance flights, except that these flights will receive priority handling only when specifically requested. <S> Air carrier and air taxi flights responding to medical emergencies will also be expedited by ATC when necessary. <S> The nature of these medical emergency flights usually concerns the transportation of urgently needed lifesaving medical materials or vital organs. <S> IT IS IMPERATIVE THAT <S> THE COMPANY/PILOT DETERMINE, BY THE NATURE/URGENCY OF THE SPECIFIC MEDICAL CARGO, IF PRIORITY ATC ASSISTANCE IS REQUIRED. <S> Pilots must include the word “MEDEVAC” in the flight plan per paragraphs 5−1−8 and 5−1−9, and use the call sign “MEDEVAC,” followed by the company name and flight number for all transmissions when expeditious handling is required. <S> It is important for ATC to be aware of “MEDEVAC” status, and it is the pilot’s responsibility to ensure that this information is provided to ATC. <S> EXAMPLE− <S> MEDEVAC Delta Thirty−Seven . <A> The US call sign is "MEDEVAC. <S> " It used to be "LIFEGUARD," but was changed in 2012 as part of the transition to ICAO flight plans, which suggests that "MEDEVAC" could be a standard (though I'm not sure if it is). <A> In Boston, where I live, medivacs use custom call signs that they pick for themselves. <S> Medflight uses the generic "Med One", "Med Two", "Med Three". <S> "Lifeflight" that is run by the University of Massachusetts uses "Lifeflight" as their callsign. <S> Northern Massachusetts is covered by the Dartmouth Hitchcock Advanced Response Team. <S> They use "DHART". <A> I little off base, but when I flew air ambulances in Southern Louisiana, where helicopter traffic is extremely heavy because of oil field and offshore use, I used the personal call sign "Savior 6" as a personal moniker. <S> I was an RN and Paramedic. <S> Helicopter call signs were known to be Aircare and Acadian Ambulance's AIRMED. <A> "Helimed" is the most common callsign for U.K. air ambulances, e.g. Helimed 42. <S> When not on an emergency call or when returning to base, they would use an abbreviated callsign, e.g. Hotel Mike 42. <S> They also usually operate as Special VFR flights, meaning they can fly using instruments and ATC vectors if required and they will be in touch with ATC at all times, mainly for traffic avoidance (other aircraft are moved to allow the ambulance clear passage).
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In radio communications, use the call sign“MEDEVAC,” followed by the aircraft registration letters/numbers.
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Why do the missiles on an F-16 point slightly down? I've been wondering this for quite a while: Why do the missiles on the F-16 point down a little bit? I went and did a little searching and found out that the F-16 isn't the only plane that has this feature, so I'm going assume it's not the F-16s frame specifically. I also doubt it's tactical because all the weapons are pointing down, regardless of the weapons role in combat. In fact I saw a few photos where the bombs closest to the fuselage were pretty level with the ground (and bombs pretty much always go down, so...) Does it have to do with aerodynamics, or perhaps ease of loading? Why is the load-out on the F-16 mostly pointed slightly downwards? <Q> If you take a look at the picture again, you'll see that the missiles are in fact lined up quite nicely with the nose of the plane. <S> The missiles are not pointed down, they are pointed forward. <S> The wings and engine (and the entire back two-thirds of the plane) are pointed up , which provides the lift to keep the plane in the air during normal flight. <S> You can see pretty well the alignment in reference to the horizon in this picture (found by @jay-carr): Just to cut off the potential comments about how planes generate lift, reference is here . <A> The AUX release is used if the CAD misfires and the stores cannot be physically ejected downward away from the aircraft. <S> Although this wouldn't really apply to the wingtip loaded aim 9's, so I can't really account for those. <S> In the super hornet the pylons are canted outwards for just this reason. <S> In fact, the emergency jettison doesn't even release the wingtip aim 9's because, in the case of the Rhino, the wing is more efficient with them in place. <S> The wingtip 9's act as a winglet of sorts. <A> It's not just the wingtip launchers that are canted downwards. <S> All pylons are canted downwards a couple degrees (~2 I believe). <S> This is to reduce the AOA to 0, thus reducing induced drag at pickle. <A> A related reason is ensuring safe store separation. <S> A lot of testing is done to ensure your munitions and fuel tanks don't come back to greet you. <S> So this doesn't happen: <S> YouTube video of ' Aircraft Store Separation Incidents '. <S> The B-1 bomber had a similar issue initially where weapons would not exit the bomb bays and just skip along on the laminar flow underneath the aircraft. <S> They had to add these spoilers to the fronts of the bays to break up the airflow. <S> The spoiler is the waffle iron looking plate in the front. <S> It drops down when the bay is opened for weapon release. <S> http://miramar.airshowjournal.com/2005/IMG_0327_2.jpg - philosoguido - https://www.reddit.com/user/philosoguido <S> The B-2 has similar waffles. <A> Not sure about the AIM-9, but the AIM-120 is mounted 6 degrees down from F-16 bore axis. <S> That means that from the pilots point of view its seeker view is centered in the middle of the HUD (below the bore-sight cross which is in upper part of the HUD). <A> I believe it's a bit of washout in the wing. <S> Washout is a slight twist to the wing, reducing the angle of incidence at the tip and reducing the probability of tip stall.
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There might be more to it in terms of aerodynamics, but I didn't engineer the jet. Usually stores are hung off an aircraft in such a manner to facilitate a safe auxiliary free-fall release. That might also be part of the reason for that alignment; to make it more convenient for the pilot to aim when shooting in BORE mode.
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Can a commercial airliner be used for military purposes? Is it possible that in case of some very serious emergency, a commercial airliner such as the B777F could be used for dropping bombs or to serve some other fighting purpose? I am simply asking about this from a technical standpoint. <Q> Retrofitting is (as the comments to your post have already stated) rather difficult and unusual. <S> In addition, the quality of service from such an aircraft you could expect to get would most probably not be great. <S> Analogy: <S> Try changing your minibus for 9 people into minivan for freight and industrial work. <S> It is also worth mentioning that the difference in operation is substantial between bombers and commercial jets. <S> You would be better off using something that is not that complicated, like a Cessna Caravan for instance. <S> I think that energy, time and money would be better spent on building more dedicated aircraft. <S> Changing the commercial ones is also not trivial and will require engineered changes. <S> It is however fully possible to design a military derivative of a commercial jet. <S> The Boeing <S> P-8 Poseidon is an example of this, being based off the Boeing 737 with the necessary modifications. <S> The armament is also fairly extensive: 5 internal and 6 external stations for AGM-84H/K SLAM-ER, AGM-84 Harpoon, Mark 54 torpedo, missiles, mines, torpedoes, bombs, and a High Altitude Anti-Submarine Warfare Weapon system[ <A> It should be noted that some civilian aircraft do have military systems fitted (and not just radars like AWACS). <S> The Israeli airline has a laser-based missile defense system fitted to its airliners. <S> (They wanted to use flares but apparently you can't drop flares at a commerical airport due to fire risk, so they got a laser-based system instead). <S> The package is slightly different from the one sold to the miltiary as it has to be completely self-contained: it can't use the interfaces - for example to the missile warning systems - on a warplane as the airliners don't have them. <S> If you were going to use bombs <S> I suspect you might roll them out of the back of a cargo plane. <S> During the Falklands War (1980s) there was some talk about Argentina possibly attempting it, but I don't think they ever did. <A> Converting pretty much any passenger hauler into a bomber would be quite an exercise. <S> You would have to add pressure bulkheads aft of the flight deck, rebuild the bottom of the fuselage to allow for doors, add considerable structure to hold the (very heavy) bomb racks, and probably remove the floor - rather tricky if the floor is also holding the fuselage together. <S> Missiles on the wings would be comparatively easy - they are not as heavy and don't require major mods to the pressure hull. <S> A "serious emergency" indicates urgency, and that gets met with existing aircraft. <S> The time taken to modify a 777 into a bomber would be fairly close to building a new bomber. <S> Although if it's a protracted war of attrition* I would expect Boeing would quickly design a new one based around the 777's tooling so they can get them out the door quickly. <S> It is very easy (and common) to use passenger haulers as troop transport. <S> Conversion to AWACS is nowhere near as complex, I suspect someone already has plans in a file somewhere to do just that. <S> And the USAF already uses DC-10 freighters as tankers - the boom is a not-overly-complex conversion and probe-drogue systems are almost bolt-ons. <S> Before anyone comments about it, the DC-10 used as a water bomber is very different from dropping explosives. <S> Water is a distributed load, and releasing it doesn't require half of the bottom of the plane to open up - it flows out through ports that can easily have structural members running across them. <S> * World War II would be a good example. <S> Evenly-matched belligerents, whoever has more resources usually wins. <S> If WWIII goes nuclear it will be over in an hour or two. <A> While commercial aircraft can obviously be used for transport missions (transporting troops or military cargo) <S> unchanged, I believe the question is really about using commercial airliners for combat missions. <S> I am not entirely sure if light business jets like the Learjet 35 meet the definition of a 'commercial airliner' in the question, but these civilian aircraft have been pressed into service for military missions during the Falklands war. <S> Learjet also make military versions of 35 series; the primary change being the addition of hard points under the wings allowing the carrying of military payloads including weapons. <S> Similar conversions include the older turboprop <S> Fokker F27 conversion: <S> http://www.combataircraft.com/en/Military-Aircraft/Fokker/F-27-Enforcer/ <S> So aircraft can be lightly modified to perform combat missions if they have the ability to carry external loads and some avionics to support the loads. <S> However such aircraft would lack features found in military aircraft such as ejection seats. <A> For what its worth Air Force One is operated by the United States Air Force and is built on the common 747 airframe. <S> Although the plane is highly customized and lets be honest only servers a single military purpose it is, for what its worth a civilian plane (in a sense) that has been converted to a military function. <A> Aircraft development seems to go the other way more often. <S> Example: the Boeing 377 Stratocruiser was developed (indirectly) from the WWII B-29 bomber. <S> It's expensive to develop a new platform; military budgets seem to be large enough for such undertakings on a frequent basis. <S> Not so in the commercial world. <S> Revolutionary designs like <S> the B-707 and B-747 come along, but even they were started with military contracts in mind as much as civilian markets. <A> This was actively considered by the USAF but rejected in favour of continuing development of the Rockwell B1 bomber.
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In the 1980s there was a proposal for a Cruise Missile Carrier Aircraft (CMCA) version of the Boeing 747, which could have carried and launched around 70-100 AGM-86 ALCM cruise missiles with nuclear warheads.
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How many people can stand on airliner's wings? This photo of Allegiant Air flight 331 got me wondering: how much weight would a typical airliner's wings be able to hold? Aside: Apparently these folks didn't realise that if they smell gas in the cabin, they probably shouldn't decide to go out of the emergency exits and stand ON TOP OF ITS TANKS! God forbid one of them gets nervous and lights a smoke! My question is basically: how much weight are airliner wings required to hold $\div$ the average passenger weight? Theoretically how many people? :) <Q> Disregarding the fact that the wing load vector on a passenger jet usually points up , not down , the wings will usually bear most of the load for the entire aircraft . <S> The MTOW for an MD-80 is 63,500 kg . <S> If an "average" passenger is 80 kg, then that is 800 passengers. <S> Obviously that is going to be greater than the number of passengers on the flight, because those wings had already lifted those passengers (and the rest of the plane) into the air in the first place. <A> The specific numbers will vary by aircraft type and model, but from an empty dry wing, you can add thousands of pounds of fuel to each wing. <S> Then on a winter night, add several pounds of ice/snow to every square foot of the wing's surface, which can easily remain there for hours or days. <S> Granted, this is all weight that is on the wing rather than on the fuselage, but as was pointed out, these wings support over 50 tons of aircraft weight at cruise and can handle over double that at a sustained G load, so these are pretty stout structures. <S> A couple dozen people just isn't that big a load for a structure that can handle loads WELL over an order of magnitude greater on a fairly routine basis. <A> This is incorporated when an airliner goes through certification (I believe it needs to carry 3 times <S> it's design load for 5 seconds, but I may be wrong in that). <S> Some airplanes are required to hold lots of weight on the wings, not only from the forces of flight, but also by the possibility of evacuations. <S> According to Wikipedia , aircraft such as the Boeing 747 can hold 740 kg/m2. <S> With a wing area of 525 m2, this means that the wings can hold 388 500 kg. <S> Assuming each passenger is about 100 kilograms, that means you can hold 3885 people on the wing at once. <S> That is, of course, if you can manage to fit them all in that gaggle without slipping off. <S> It'd be pretty tough getting 5 people in a square metre, would it not? <A> Everyone pointed out that the total weight won't be a practical limitation. <S> But what may be the limit is the local pressure on the wing skin. <S> Aerodynamic forces are nicely distributed over the wing area. <S> Not so with shoes. <S> A small lady on high heels may do enough damage to ground the aircraft :) <S> Not to mention that some people may start wandering on flaps and other "no step" areas, which may also cause structural damage.
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Each aircraft has its own design for how much it weight it has to hold on the wing.
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Is it possible for an airliner to safely fly with doors open? From another question asks about the possibility of dropping bombs from converted airliners. My question: is it possible to safely fly aircraft with a door open for the whole flight envelope? Would the aerodynamics be affected if we did not close the door? I am not asking about the need of oxygen for the crew, just about the aerodynamics involved. I know the plane would not be pressurized. <Q> The Stratospheric Observatory for Infrared Astronomy (SOFIA) is a modified 747 that has an 5.5 m x 4.1 m door that is opened during flight for the installed in infrared telescope. <S> But the door is usually closed during takeoff and landing. <S> But according to this story there are emergency procedures to land with an open door and it had to do so once, when it became stuck half open. <S> Images courtesy Wikipedia <A> Aloha Airlines Flight 243 proved that it's possible for a plane to fly with about 25% of its roof missing. <S> The door, however, appears to have remained closed until landing. <S> Image courtesy Wikipedia <A> Check out my answer here to a similar question (about what would happen if you open a door in flight). <S> You could do it up until you would need to pressurize the plane (or you would have wear O2 masks or something to be able to breathe). <S> Planes like the DC-3 used in WWII for paratrooping regularly ran with their doors open. <S> If you consider rear cargo ramps doors, <S> the C-130 can open its rear ramp for HALO jumping at high altitudes . <S> In typical HALO/HAHO insertions the troops jump from altitudes between 15,000 feet (4,600 m) and 35,000 feet (11,000 m) <S> There is at least one other powered glider I can think of that can open its doors mid flight... <A> Since comments mentioned that not all of the outcomes from Aloha 243 were exactly safe, here's another example that actually was quite safe: <S> Southwest 812 had a large hole open in the roof during flight at cruise altitude, resulting in rapid depressurization at 34,000 ft. 2 of the 123 people on board (a flight attendant and a passenger) suffered minor injuries. <S> The plane diverted to Yuma, Arizona and landed safely about 26 minutes after the depressurization. <S> As with the other cases, the doors were technically shut, but I'm not so sure that that made much difference. <S> Furthermore, this was not the first time this had happened. <S> Less than 2 years before this incident, Southwest 2294 had a similar incident (though with a smaller hole) and safely diverted to Charleston, WV with <S> no injuries at all. <S> What's more: according to the FAA's registry and airfleets.net , it looks like both of these aircraft were returned to service and are still actively flying for Southwest! <S> So, it looks like both the "you can walk away from it" requirement and the <S> "the aircraft is reusable" preference were met in both instances. <S> The Boeing 727 <S> Another case that actually doesn't involve any structural damage at all is the 727 and its airstair. <S> In the famous case of D.B. Cooper's hijacking , this occurred while the aircraft was pressurized. <S> According to the wiki on the incident, the result was the following: <S> The crew soon noticed a subjective change of air pressure, indicating that the aft door was open. <S> At approximately 8:13 pm the aircraft's tail section sustained a sudden upward movement, significant enough to require trimming to bring the plane back to level flight.[33] <S> At approximately 10:15 pm Scott and Rataczak landed the 727, with the aft airstair still deployed, at Reno Airport. <S> Additionally, some skydiving clubs even offered dives from the 727 for many years, though these presumably didn't pressurize the cabin. <S> I'm not sure whether this is still offered. <A> Yes they can, here's a Convair 880 with cargo door open. <S> DC-8 <S> with cargo door open. <A> For the whole flight envelope, maybe not. <S> Depends on the door design. <S> Gear doors frequently have speed limits before they fly off on their own. <S> Large openings create substantial drag, so we may find that the envelope is self-limiting: the aircraft can no longer reach speeds and/or altitudes where the opening is a big problem. <S> There are too many variables for a simple answer. <A> Biplanes and ultra-lights don't have any doors at all. <S> In general, for any plane the wing, the empennage and, to a lesser extent, the surface area on the lower part of the fuselage is all that is important. <S> If you installed structure-reinforcing crossbars you could remove the entire fuselage wall of a commercial jet and it would still fly.
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UA Flight 811 was able to make a safe decent and return to airport after its door blew out so large planes are maneuverable with out door. In short it depends largely on the plane but in the most general way of looking at it.
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Could the US Air Force ever replace the Thunderbird pilots with drones? Would it be possible or practical for the US Air Force to replace the Thunderbird pilots with drones? The drones could perform more difficult maneuvers and do them more precisely. The University of Pennsylvania is successfully working on small-scale formation flying. <Q> Tight formation flying can be done with stock aircraft and skilled pilots, but drones would need additional sensors and new code in their FCS . <S> Also, you can fly aerobatics even with gliders, but only when a decent power-to-weight ratio is reached, aerobatics becomes a spectator sport. <S> I think it is frivolous for the US Air Force to pay for the development and additional equipment to make drones fly aerobatic displays, but few Air Forces are known for an enlightened budget discipline. <S> I expect, however, that this will be added first by a company producing drones, and for demonstration and marketing purposes, and then the taxpayer will fund this indirectly. <S> Formation flying was a needed skill for bomber pilots, back then when their bundled defensive weapons provided the best protection against fighter attacks, and aerobatic flying was and still is valuable for fighter pilots. <S> In the days of missiles and UAVs, neither formation flying nor aerobatics are necessary skills anymore, so in a way aerobatic formations are a quaint relic from the last millennium. <S> To answer the "could" aspect of your question: No, not directly. <S> This would need modifications to existing drones. <A> UAVs and UCAVs can be programmed to fly in formation as has already been demonstrated. <S> There may be military applications for this capability. <S> A tactic used by Luftwaffe "sturmgruppe" units against US bomber formations in World War Two was the "company front" assault in which the heavily armoured FW190 fighters, flying in a close line abreast formation, would approach a bomber formation from the rear, dividing the defensive firepower, and then break up at the last moment to attack individual bombers. <S> UCAVs could potentially use similar tactics effectively against enemy ground, naval or air forces in some situations. <A> Like others have said, the Thunderbirds mission is recruitment. <S> A drone formation is absolutely possible and would be quite the show, but it would not do much for recruiting civilians if the drones were the only part of the show. <S> Some might suggest using RPAs to bring a human aspect back into it, but that would not be a great idea either, at least with current technology. <S> Formation flying relies heavily on recognizing small discrepancies and making small corrections to achieve that "locked" appearance. <S> RPAs, like the MQ-9 , have low latency if the operator and aircraft are in the same area, but there still is some latency with the signal being transmitted, translated, read, and displayed. <S> In addition, unless the operator is wearing some sort of augmented/virtual reality headset and the aircraft has some 180+ degree camera, the spatial awareness will be severely degraded. <S> Finally, our current RPAs are loiter aircraft, so they are really not fit for being in formation. <S> What I mean is that the wide wings and light-weight design make the aircraft prone to the effects of turbulence, convection, probably even the propwash of the other aircraft in formation. <S> All that being said, I think once we get the jet-propelled drones more developed and trusted, we might be seeing them in airshows. <S> The MQ-25 , a refueling, carrier-based drone, would be a prime candidate for a refueling demo (the ones where the fuel recipient isn't actually connected ).
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To answer the "ever" aspect: Once the services field UCAVs (unmanned combat drones) with a good power-to-weight ratio , having them fly aerobatic displays looks almost unavoidable, but I expect it will not be the Air Force, but the marketing department of a big contractor driving this.
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Why are the call signs of some airlines completely different than their name? The call sign of U.S. Airways is "Cactus", and that of British Airways is "Speedbird"; while for Malaysia Airlines is "Malaysia", Qantas is just simple "Qantas". Why is it that the call signs of some airlines are so different from their names? <Q> I found this on Wikipedia : <S> Some call signs are less obviously associated with a particular airline than others. <S> This might be for historic reasons (South African Airways uses the callsign "Springbok", hearkening back to the airline's old livery which featured a springbok), or possibly to avoid confusion with a call sign used by an established airline. <S> Country names can also change over time and new call signs may be agreed in substitution for traditional ones. <S> Before America West bought US Airways, their callsigns were Cactus (associated with the deserts of the American West) and USAir. <S> After the merger, the combined airline kept the better-known (airline) name, and the other airline's callsign. <S> Now, after the acquisition/merger of American Airlines, they're using that airline's name and callsign. <S> Leading to more than a few radio calls recently (late spring / early summer 2015) along the lines of "Center, Cactuuu <S> ...merican 123, FL 350" <A> More reasons call signs might not be the name of the airline would include: <S> You need to have a call sign that contains few syllables rather than many, and that comes across relatively distinctly when communications are bad. <S> The radio traffic can be fast, furious, and filled with static. <S> You need to have a call sign that doesn't expose you to ridicule. <S> For example, when UPS first started flying with their own aircraft (as opposed to using contract aircraft and crews, which they first did), they used the call sign "brown tail. <S> " That didn't last long. <S> You need to have a call sign that does not give you political problems. <S> For example, I worked for an airline that was known to be owned by Jewish interests and whose major route was New York to Tel Aviv. <S> We also did a lot of charters. <S> There was no way we could get overfly permits from either Iran or Saudi Arabia using our usual call sign, so we had an alternate, little used call sign for those flights. <S> You may be operating a contract flight. <S> I flew many such flights, and the call signs I can offhand remember using included: <S> Speedbird, Air India, Garuda, United, Japan Air, and Delta. <S> Also on military charters we often used a military call sign, but I can't remember what it was. <S> It was set up especially for the military airlift for Operation Desert Shield, the buildup for the first Gulf war. <A> The callsign is the combination of the ICAO Radio Telephony (R/T) designator and a flight specific identifier consisting of numbers and letters. <S> In addition to the R/T designator there is also a three letter designator used on flight plans and air traffic control display systems. <S> The R/T designator (callsign) must not cause confusion with other operators flying in the same area, preferably at most three syllables long and it must be pronounceable in at least one of the following languages; English, French, Spanish or Russian. <S> Since there are many operators that have "airline" or "airways" in their name, that word is usually avoided in the R/T designator as it easily causes confusion. <S> Usually an alternative is found that is in some way related to the airline. <S> For pilots it is not too difficult, they are typically paying attention specifically to their own R/T callsign. <S> For controllers it is more difficult since they have to associate the three letter code on their screen with R/T designators that are not related in an obvious way.
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Companies' assigned names may change as a result of mergers, acquisitions, or change in company name or status; British Airways uses BOAC's old callsign ("Speedbird"), as British Airways was formed by a merger of BOAC and British European Airways.
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How can I see all commercial destinations to a country from a particular airport? I live in Las Vegas, which obviously has a large airport with a broad array of international flights. Is there a quick way for me to see all the non-stop commercial flights that are available to Mexico? I don't need to necessarily know the airline, just which cities are available for non-stops from Las Vegas. <Q> There can be a number of websites which can provide this information. <S> Wikipedia and the specific airline's website can be a great resource too. <S> OpenFlights gives you a graphical representation of direct flights from a particular airport. <S> It appears that this service is for all major airports across the globe. <S> SkyScanner can provide the information you are looking for. <S> As for your example, you'll enter Las Vegas in the From text area, and then leave the To area blank. <S> It will search all destinations (grouped by countries) where there are direct flights (or with one stop) available. <A> Wikipedia entries for airports almost always have the list of destinations served from the airport, and I think the plane-spotter community keeps them very up to date. <S> But it is indexed by airline, not country. <S> Given the likelihood of there being only 2-3 destination airports in a single country, you could search on those city names - or else just browse the list. <S> The entry for McCarran International in Las Vegas is https://en.wikipedia.org/wiki/McCarran_International_Airport#Airlines_and_destinations <A> For seeing all non-stop flights, you may use any travel website. <S> See this example using Cleartrip for non-stop flights between LA and Mexico. <S> Have the knowledge of airlines and airliner as well! <S> Here are all the departures from KLAX by Flightaware . <S> Alternately, you may check for the airport's website to see all the destinations served by an airport (available at websites of only few airports). <S> For ex. <S> here are all the destinations served by Edinburgh airport. <S> And, if these don't work out, go with timbo's idea!
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And, you can use any flight tracker for all the cities served by an airport.
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Do all B777 family aircraft have the same engines? I think there are multiple variants of engines for the different variants in B777 family but I am not sure but is it GE90-115B in one while Trent and PW in others? <Q> TL;DR: <S> No. <S> For the true answer refer to the FAA Type Certificate Data Sheet 777-200 2 Pratt and Whitney Turbofan Model:PW4074, PW4074D, PW4077, PW4077D,PW4090,PW4084D, and PW4090-3(Engine <S> Type Certificate <S> No. <S> E46NE) <S> 2 General Electric Turbofan Model: GE90-76B, GE90-85B, <S> GE90-90B, GE90-94B(Engine Type Certificate <S> No. E00049EN) <S> 2 Rolls-Royce Turbofan Model: RB211-Trent 875-17, RB211-Trent, 877-17,RB211-Trent 884-17, RB211-Trent 892-17, or RB211 <S> Trent 892B-17, RB211 Trent 895-17(Engine Type Certificate E00050EN) <S> 777-300 <S> 2 Rolls-Royce Turbofan Model: RB211-Trent 884-17, RB211-Trent 884B-17,or RB211-Trent <S> 892-17(Engine Type Certificate E00050EN) <S> 2 Pratt & Whitney Turbofan Model: PW4090, PW4098(Engine Type Certificate E46N) <S> 777-300ER 2 General Electric Turbofan Model: GE90-115B(Engine <S> Type Certificate <S> No. E00049EN) <S> 777-200LR 2 General Electric Turbofan Model: GE90-110B1 <S> 2 General Electric Turbofan Model: <S> GE90-115B <S> (Engine Type Certificate <S> No. E00049EN) <S> 777F <S> 2 General Electric Turbofan Model: <S> GE90-110B1 <S> 2 General Electric Turbofan Model: GE90-115B(Engine <S> Type Certificate <S> No. E00049EN) <A> From a related answer : <S> The Emirates Boeing 777-300 aircraft have the Rolls Royce RR Trent 892 engines installed. <S> They deliver 415 kN of thrust, almost 100 kN less than the GE90-115BL1 engines. <S> When a customer orders a Boeing 777-300 they can pick their choice of the four engines available for that model. <S> When they order a Boeing 777-300ER they will get the GE engine. <A> Though @DeltaLima has already answered your question, I'd like to source my information from Wikipedia : <S> The following engine options are available for various 777 variants: 777-200 : <S> PW4077 , RR877 , GE90-77B <S> 777-200ER : PW 4090 , RR 895, GE90-94B <S> 777-200LR : GE90-110B1 , <S> GE90-115B1 <S> 777 Freighter: <S> GE90-110B1 , GE90-115B1 <S> 777-300 : PW 4098 , RR 892 , GE90-92B/-94B <S> 777-300ER : GE90 <S> -115B1 <S> 777-8X : GE9X 777-9X : GE9X
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The Boeing 777-300ER is always equipped with General Electric GE90-115BL1 engines, while the baseline -300 can be ordered with four different engine models from General Electric, Pratt& Whitney or Rolls Royce.
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Exactly what kind of radios are prohibited for passengers inside an aircraft? I know that passengers are asked to put their cell phones on flight mode. But some carriers allow use of WLAN on-board. So, what radios should passengers refrain from using?Also, if a person uses a GPS receiver on his/her mobile phone (on flight mode), would it interfere with the aircraft communication system? <Q> There is actually a simple answer, but it probably isn't exactly what you are looking for: <S> Refer all questions about what is allowed to your specific airline. <S> Each airline has to come up with their own list of allowable electronic devices, and submit that list to the FAA with appropriate documentation in order to gain approval to allow passengers to use them during flight. <S> Some airlines allow almost everything as long as it can be put into a non transmitting mode (airplane mode), while some still require ALL electronic devices to be completely powered down at all points during the flight. <S> Because of this, every airline is a little different and you are required to follow their rules while on their flights. <A> The simplest answer to your question is, none that have not been specifically approved for use by the FAA. <S> The FAA, in U.S.-controlled airspace, has pretty much all the power and responsibility for ensuring civilian air travel is safe, and they operate with an abundance of caution in all things, because that draconian code of rules and regulations is what keeps the agency itself from taking blame for a plane crash; if everyone followed all the rules and the plane still went down, it's the government's butt on the line. <S> So, the FAA has, for decades, maintained more or less a blanket ban on operation of devices with a transmit feature, even as modern airframes (and by "modern" I mean practically anything in the sky today) are well-shielded against radio interference, and consumer devices available for purchase and casual use do not transmit on frequencies anywhere near those used by aircraft for communication or navigation. <S> The reason is simply that it is possible for a device to cause interference with aircraft systems, whether directly by pirating the frequency or indirectly through intermodulation or other artifacts of radio carrier wave dynamics, and it was simpler, easier and cheaper at the time for the FAA to ban them all than to evaluate every device or device type against every airframe in commercial aviation, verify empirically that it does not cause interference, and educate flight crews and the general public about which device types, makes and models specifically are or are not allowed. <S> The FAA has since changed tack; it has worked with the FCC beginning in the 90s to develop a set of joint rules for both device and aircraft systems design that, if complied with by the manufacturers, will guarantee the device will not cause interference. <S> Devices meeting these criteria, including practically any smartphone or tablet on the market today, can be used during "non-critical" stages of flight (all usage of potentially-interfering devices is still restricted during takeoff, landing or at any time by instruction of the flight crew) while onboard an aircraft certified for use of such devices while airborne (meaning the airframe complies with rules for shielding/isolation of sensitive electronics; this certification, including any needed retrofits, can be done during scheduled maintenance on each airframe). <A> @PriyankGupta was heading in the right direction. <S> Back when more people carried portable FM/AM receivers to listen to music, there was a problem with the receiver local oscillators causing interference. <S> For example, If I wanted to listen to an FM station at 105.1 MHz, the local oscillator was 10.7 MHz above that frequencies <S> so it was operating at 115.8 MHz. <S> Leakage from the local oscillator could and did interfere with the aircraft receivers operating in that band. <S> Of course, now days, almost no one uses portable FM broadcast receivers. <S> However, the concept is the same for the various types of receivers and transmitters. <S> The radios themselves may not interfere directly but one of the signals that gets mixed with another signal might. <S> In modern commercial aircraft, they have multiple different systems so the likelihood of an airplane being severely compromised by a cell phone in the passenger section is very small but not zero. <S> I always turn mine to airplane mode. <S> I don't my family reading in the newspaper that the cause of a plane crash I was killed on <S> was my cellphone being on.
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In general, no electronic device that has a transmit function may be used because of possible interference though, unless specifically approved. The GPS receiver would not cause problems, but this doesn't mean that you are necessarily allowed to use it, and there are other things in your phone that could cause a problem though.
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Is there a downside to trying multiple flight instructors? My local airport has a Part 61 flight school and gives students the option of selecting among three Certified Flight Instructors. Farhan and others have posted excellent explanations of characteristics to look for in instructors. Other than wasted time and money, is there any downside to doing an "Introduction to Flying" lesson with each of the three instructors and seeing which one I like best? Similarly, am I likely to offend CFI's that I'm "looking around" other options? <Q> No . <S> Definitely try more than one CFI and ideally, more than one school . <S> This is the smart choice and one I recommended regularly when I was an active flight school CFI. <A> My first flight instructor was kind of a jerk. <S> You know the kind: <S> First flight, "Let's take the plane for a SPIN", "How about a BREAKFAST ROLL? <S> " <S> After a few hours into my training, there was a scheduling conflict and I got a different instructor - a military pilot with many thousands of hours of flying time and a very different attitude. <S> Professional. <S> He worked me harder than the other instructor ever had. <S> The flight school eventually canned my first instructor. <S> He moved across the field and took on new students at a different school. <S> Then there was the day one of his students almost ran over me in the pattern. <S> They were flying a Cessna and I was flying a Grumman. <S> The tower had cleared them AFTER me, but they apparently never even saw me and pulled into the pattern on the downwind right underneath me. <S> Fortunately, both I and the tower realized what was happening, so I just maintained altitude and extended the downwind leg and the tower cleared the Cessna ahead of me. <S> When I called up the flight instructor to tell him about the near mishap, his attitude was quite cavalier. <S> He seemed to think it was funny. <S> Shop around. <S> If you can find a military instructor with thousands of hours of flight time, odds are you'll find a very serious teacher. <A> As mentioned it's a good idea. <S> You will be spending a lot of time with this person in a very confined space, not only should you trust their abilities but should at least get along with them. <S> FWIW <S> I would not consider this a waste of time as the hours will count towards your total and you will be learning new things while trying new instructors. <A> I think many instructors is a good idea, since you see their differentcharacteristics and each has their own sweet spot. <S> I had at least10 different instructors for my PPL, and learned a lot from the differences aswell as their similarities. <A> There is no harm trying out different instructors. <S> Note that instructors have different strengths. <S> Some may be better at teaching tailwheel and others at instruments. <S> One problem is that you will not really be able to tell the difference between a good instructor and a better one in one flight, unless it is a personality issue. <S> From a technical point of view it will be hard to tell. <S> Better instructors tend to get booked up and are hard to schedule. <S> If your instructor's schedule looks really full, that is a good sign <S> he is a good one. <S> Also, look at their flying experience. <S> I notice that the better instructors tend to have more flight hours. <S> Once you start flying be sure to get "check rides" from other instructors once in a while. <S> A new instructor will usually teach you new stuff. <S> In this sense, even a bad instructor can be good sometimes because they can teach things maybe your usual instructor does not know. <S> Beware of "easy" instructors that just soft shoe everything. <S> They are the nicest instructors, but they are slow teachers and they can be derelict and just "go with the flow" when they should be correcting you. <S> If one or two instructors tell you that you should not fly and are not cut out to be a pilot, the dumbest thing you can do is to find an easy instructor who will just collect your money, even though he knows you are not pilot material.
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Different instructors have completely different styles and areas of emphasis, so it can be very useful to get "alternative points of view" from time to time. You're about to spend a ton of money - do the due diligence and spend more up front to make sure you don't waste time and money with someone whose teaching style or personality clashes with you as a student.
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How do aircraft land on snow? It is very common today for planes to land on snow (for example, in Antarctica). How are planes kept in control with so little friction against the ground? What is the procedure to perform this kind of landing? How much extra distance, on average, does an aircraft cover by landing on snow, compared to landing on dry pavement? ( Video ) 4 US Air Force Hercules aircraft at Willies field, Antarctica Source <Q> It is very common for planes to land on snow (i.e. packed snow) or even ice runways. <S> How are planes kept in control with so less friction on ground? <S> Snow/ice friction is a function of the outside air temperature, so it depends. <S> Another factor is whether the runway was packed, fresh snow - and the temperature the previous day. <S> The colder it is, the more friction the snow will have (i.e. adequate braking). <S> In warmer temperatures the snow will be slick (scarily slick at times - as in nil braking). <S> While flying a multi-engine airplane, one can use differential power. <S> If you're flying a single-engine airplane - one is better off with small taps on the brake during slick conditions. <S> If the OAT is relatively cold (well below freezing), braking can be pretty good. <S> What is the procedure to perform such kind of landing? <S> The procedure is the same as a standard landing. <S> However, it is awfully nice to have good contrast on the snow to see the runway. <S> Often runways that are pure snow/ice will be more visible than the surrounding terrain. <S> At the very least - the runway will be outlined with some sort of runway markers. <S> And, on an average how much extra distance does an aircraft covers by landing on snow, as compared to landing on ground? <S> As I said before, it is really dependent upon the outside air temperature and the condition of the runway (i.e. packed snow or fresh snow). <S> For example, suppose there were fresh snow on a relatively warm day (30 degrees farenheight) and the snow is compacted (i.e. by humans) that day. <S> Say, night-time temperatues drop to 0F, and the next day you land with an OAT of 30 to 35+F... <S> that runway is going to be SLICK. <S> However, if the temperatures were to stay at 0F - you would actually have decent braking. <S> Even further, if the OAT dropped to -40 below...you will have excellent braking. <S> TLDR : <S> Snow conditions are always changing and braking/control of the airplane are dependent on those conditions. <S> Snow-conditions are highly dependent on the outside air temperature and to some degree human-maintenance (for better or worse). <S> *source: Personal experience from flying in the Arctic. <A> I'd quote from this source <S> Landing on snow itself is not a problem. <S> The rudder is used for steering upon landing so control is no different than landing on a dry runway. <S> Getting stopped is where it can get alittle tricky. <S> A wise Capt once told me not to make any turns offs from a snowy/slippery runway until your slow enough that you have to actually add power to get off. <S> Wise advice indeed. <S> and Landing on wet or contaminated runways requires moreclose control over approach speeds. <S> With a B747 you should accomplish touchdown on therunway at 1.000 ft from the approach end of the runway. <S> The airplane should be flown firmly onto therunway at the aiming point. <S> It's very important not to land long! <S> The speedbrakes should be used immediatelyafter the main gear contacts the runway, because theydestroy lift, increase drag and, most important, increasemain gear loading. <S> It's necessary to use thrust reversers at high power as soon as possible becausethey are most effective at high speed. <S> Hope <S> this answers your questions. <S> TY <A> I only fly single engine aircraft. <S> I have landed a number of time on snow and on ice. <S> The two things I do differently is to 1) feather the touch-down with a slight power increase just before hand, and 2) "fly" the aircraft all the way to a near stop. <S> That is to say that instead of steering the plane once on the ground, you treat it more like you are still in the air.
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Careful use of reverse thrust and braking along with not making any turnoffs from the runway until sufficiently slowed are the name of the game.
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How do modern helicopters tackle Vortex Ring State? According to the wikipedia page : Air vortices can form around the main rotor of a helicopter, causing a dangerous condition known as vortex ring state (VRS) or "settling with power". In this condition, air that moves down through the rotor turns outward, then up, inward, and then down through the rotor again. This re-circulation of flow can negate much of the lifting force and cause a catastrophic loss of altitude. Applying more power (increasing collective pitch) serves to further accelerate the down wash through which the main-rotor is descending, exacerbating the condition. The vortex ring state has also been listed as a potential hazard in the Wikipedia page for helicopters. What are the various preventive measures used to prevent such a condition? <Q> Helicopter driver here. <S> I am not aware of any technical features which can prevent it. <S> Quite simply, the disc must accelerate air downwards to generate lift. <S> If the helicopter descends into that downward accelerating air, it is recycled through the disc resulting in a catastrophic loss of lift. <S> Do not fly into these conditions. <S> Be able to recongise the symptoms of vortex ring state. <S> Understand, and be practised in, the correct recovery technique, which is most often fly in any direction away from the vortex. <S> I am not an aerodynamics engineer <S> but I doubt that there is a physical solution to this - and if there was, it would likely have been implemented by now. <A> There's an interesting article on the hazards at wikipedia . <S> The avoidance tactic mentioned in that article is to avoid rapid descents at low forward airspeed - this would seem sensible as that's where the rotors will be exposed to their own downwash. <S> And the preferred reaction also described there is to use the cyclic to fly forwards, to move into less disturbed air. <S> (I have heard that another cause of the condition is flying into narrow spaces among tall buildings, but unfortunately I haven't been able to find a reference.) <A> Late reply, but I wanted to bring attention to this very excellent video that shows vortex ring state, using a helicopter with a sprayer, spraying a mist of water to visualize the airflow around the rotors. <S> At about 2:28 into the video, that helicopter enters vortex ring state, and you can see exactly what happens to the airflow over the rotors. <S> When the helicopter descends too quickly with little or no forward airspeed, the downwash curls around and breaks up the airflow on the top of the rotors. <S> The end result is much the same as breaking up the airflow over an aircraft wing, like an aircraft with insufficient forward speed and a high angle of attack... <S> it kills most of the lift. <S> Essentially, the blades stall, and the helicopter drops even faster. <S> Pulling up on the collective would do the same as pulling back on the stick a stalled aircraft... <S> it would just make a bad situation worse. <S> The solution is to get out of the turbulent airflow, by either tilting the helicopter forward, or in the video that demonstrates the Vulchard technique, tilting to one side. <S> As you can see in the video, the helicopter recovers fairly quickly, and the mist illustrates how tilting to one side restores smooth airflow on the tops of the rotors, enough to arrest the too fast descent. <S> Or, as Simon notes... the better solution is to know your aircraft and not allow it to get into VRS in the first place... <S> just as with fixed wing aircraft, you're well advised not to let it get into a stalled condition. <A> The left picture above from J. Gordon Leishman, Principles of Helicopter Aerodynamics, depicts the Vortex Ring State where the wake below the rotor is re-ingested on top of it. <S> A dangerous situation indeed, since adding power may result in higher vortex velocities only. <S> In section 5.3 of the Leishman book a further detailed discussion of the VRS can be found. <S> A quantification is given as induced power loss in VRS: measured data shows a power loss factor of almost 2 in some circumstances, and here lies one of the issues in trying to recover with adding power. <S> The engine is simply not dimensioned to deal with such effective power loss. <S> Another problem is flow fluctuation, leading to fluctuations in thrust of up to 40% depending on disk loading: <S> The VRS is accompanied by an extremely unsteady (aperiodic) flow field surrounding the rotor. <S> All in all a dangerous situation to be in, since the flow fluctuations associate with a loss of predictability. <S> Best avoided, although one of the methods to recover is to reduce rotor Angle of Attack: <S> Notice that the fluctuations drop off quickly as the disk AoA decreases below 50° and is consistent with piloting experience on helicopters, which shows that a forward speed component causes the rotor to quickly exit the VRS. <S> After tuning the flight controls of a CH-53 helicopter simulator and going for a test ride, I inadvertently got the sim in a VRS in the thin mountain air surrounding the modelled airbase. <S> The instructor told me to give full left lateral, wait for the helicopter to reach a considerable roll angle, then full right lateral, then mid again; then regain horizontal attitude while pressing cyclic forward. <S> The initial lateral movement indeed changed the disk AoA enough to exit the VRS quite rapidly. <S> I don't know if this is taught as a recovery practice in the real helicopter though, or if it only works in the (high fidelity military) simulator. <A> There are four factors: low airspeed less than 20 knots, partial power, high rate of descent greater than 300-500 feet/minute, and steep angle of descent greater than 30 degrees. <S> Somehow, the aircraft has to descend, either by settling or other means at great than 30 degrees. <S> Remove any of these four items and VRS is not possible.
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The preventative measures are: Be aware of the flight conditions under which vortex ring state may occur.
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Why are turbofan inlets leaned/angled forward? (Image Source: Wikipedia ) Seeing that everything is radially symmetric (apart from the nacelle mount, naturally), I wonder why the inlet (the front part of the nacelle) is usually skewed? <Q> The inlet angle is a compromise between cruise, when the aircraft has a low angle of attack, and the take-off and climb phase, when the engine runs at maximum thrust, and the angle of attack is several degrees higher than during cruise. <S> Especially right after rotation, when the aircraft is heavy and slow, the angle of attack might reach into the lower two-digit territory, and flow disturbances must be avoided especially in this phase. <S> Note that the fuselage should be horizontal during cruise to avoid making the work of the cabin personnel harder than it already is. <S> A few degrees of intake misalignment can be tolerated, and the misalignment is usually split between cruise and post-rotation climb. <S> With supersonic intakes, things are different: They are much more sensitive to misalignments, and the intakes of planes like the SR-71 have been carefully optimized for their cruise condition. <A> Adding to Peter's answer , one of the flow disturbances that has to be avoided is flow separation in the inlet cowl. <S> More specifically, the flow separation at the beginning of the lower inlet lip. <A> To align the inlet with this local flow direction, it is slightly angled down. <S> For the same reason the engines on Bombardier CRJ series aircraft are slightly angled upwards! <S> The other answers are correct as well though, this is just an additional element.
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I'm quite suprised that this wasn't mentioned in any of the previous comments or answers, but since the inlet is quite far in front of the wing, it sees some significant upwash from the wing.
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What kinds of planes can tow banners? Planes can sometimes be seen towing banners around large cities or events. What kind of plane is good for this type of flight? With banners they appear to be flying slower than usual. Is this just an illusion? What are the practical or regulatory requirements that the plane must meet to be capable? I am tagging with FAA but information about other jurisdictions is welcome. <Q> What kind of plane is good for this type of flight? <S> The cheap kind. <S> I'm not entirely kidding about the cheap part though; banner towing is hard on the airplanes and carries a higher-than-average degree of risk, so you do want to stay away from airplanes that will be expensive to fix, if you can help it. <S> bolted to it, so you'll see a ton of different things, but tailwheels seem to be the norm, at least in the US, and many outfits will make additional modifications such as removing engine cowlings to help with cooling. <S> With banners they appear to be flying slower than usual. <S> Is this just an illusion? <S> No, they are indeed flying slower. <S> First of all, the added drag from the banner slows the airplane down all by itself. <S> Secondly, you're being paid to advertise, so you want to make sure that people can read whatever sign you're towing. <S> You're not flying the ragged edge of the stall <S> (it's dangerous, uneconomical, and unnecessarily hard on the engine), but you're probably going to be flying on the backside of the power curve. <S> What are the practical or regulatory requirements that the plane must meet to be capable? <S> In addition to the practical considerations we've talked about above, banner towing operations require a waiver from the FAA. <S> The company has to apply for it and every pilot must be trained in banner tow operations, pass a review from an approved FAA inspector (who will be watching you perform picks and drops from the ground), and be added to the waiver. <S> The aircraft and tow hitch mechanisms also have to be inspected and approved for banner tow operations, and added to the waiver. <S> Here is the current FAA Banner Tow Information handbook, covering equipment, operations, waiver information, and other assorted miscellaneous if you're curious to learn more. <A> In general, towing requires an aircraft capable of safe operation at low speeds, e.g. a low stall speed, since the drag of the banner makes it difficult to reach higher speeds. <S> Good low speed handling also makes banner pick-up and drop-off operations safer and easier. <S> You can see the FAA's manual on towing operations here (PDF). <S> It's not just airplanes that tow banners. <S> I worked with a helicopter pilot who used to fly "helibanners." <S> The advantage is that a very large banner can be towed since the helicopter can handle gusts "dragging" the helicopter down to very low flight speeds and the rotor can provide considerable thrust at low speeds. <S> The new hazard is that the banner and its rigging can get caught in the tail rotor, which would be catastrophic. <S> This is usually dealt with by using a special weighted banner design that keeps everything away from the empennage. <S> Image Source <A> Generally speaking (I spend a lot of time on the shores of NJ) <S> I see Piper Pawnees , Super Cub's , and a variety of Citabrias . <S> Here is a good thread discussing it. <S> Keep in mind that a banner creates a lot of drag and will greatly effect a plane that is flying cross wind so power is a concern. <S> Just this past weekend there was a super cub towing a banner over the shore that i was watching pretty closely. <S> They were flying up the shore with almost a 45 degree headwind at about 25Kts (I didn't have the winds aloft on hand that was ground speed). <S> At some points it almost seemed as if he was not moving and at others it seemed as if he was being blown out to sea. <S> It was an interesting real world visualization on the effect of crosswind for sure.
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Joking aside, the exact airplane to use depends on the size of the banners or billboards you're going to be towing, but generally speaking you want something reasonably rugged, with good slow flight characteristics, sufficient engine power to be able to overcome the added drag from the banner, and, hopefully, some decent fuel consumption. As for specific types, I've seen banners towed with everything from -152s to Grumman Agcats; a large banner tow operation apparently had a Super Cub with an O-540
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How are cruise missiles different from ballistic missiles? Cruise missiles and ballistic missiles are used by many nations as offensive and defensive technology. How do cruise missiles and ballistic missiles maneuver, and what are the differences between the basic principles of these maneuvers? <Q> Most have wings, although a few may use lifting body designs. <S> They maneuver using control surfaces on the wings and tail like an airplane. <S> Mission profiles can include big course changes, to evade air defenses, or to hug terrain to stay hidden. <S> They can be launched from fixed ground positions but most are launched from mobile platforms. <S> They tend to have shorter ranges than ballistic missiles. <S> A ballistic missile is a rocket that powers its way out of the atmosphere and coasts in an arc, re-entering the atmosphere before hitting its target. <S> They have little maneuvering capability, once the boost phase is done it's all down to physics. <S> Some warheads are able to maneuver a bit in re-entry in order to hit a pinpoint target, others are just rocks at that point. <S> The largest ones are launched from fixed positions like missile silos but smaller ones are mobile. <A> Cruise Missile : <S> Uses thrust for the whole trajectory <S> Uses aerodynamic forces by moving control surfaces to move. <S> May use thrust vectoring <S> Ballistic Missile: <S> Uses thrust to reach very high altitude. <S> After that, no thrust, only potential energy is used and converted to speed. <S> Uses aerodynamic forces (for a limited extent) to move by deflecting control surfaces. <A> Cruise missiles have rocket or jet engines that are powered during the entire flight. <S> It allows the missile to cruise low through the atmosphere, sometimes just above ground level. <S> Lift and guidance of the missile are achieved by aerodynamic forces. <S> Ballistic missiles on the other hand are not powered during most of their flight. <S> During the launch they are given a high initial velocity and then coast throughout most of their flight. <S> Their flight path is by approximation parabolic. <S> Ballistic missiles are guided during brief periods of their flight, aerodynamically and/or by thrust vectoring. <S> Intercontinental Ballistic missiles go into a suborbital paths and spend a considerable part of their trajectory outside the atmosphere. <A> A ballistic missile is one which flies in a ballistic trajectory. <S> They usually are composed of a solid rocket booster stage lifting a warhead and guidance section aloft as a payload . <S> After the booster burns out, the payload section continues on a ballistic trajectory to the target. <S> Sometimes the booster motor is jettisoned after burnout. <S> Ballistic missiles vary in size and capability from battlefield types such as the ATACMS missile fired from the M270 MRLS, to regional range types such as the MGM-31 Pershing missile to intercontinental range types such as the Minuteman III. <S> Warhead types can range from conventional aerial explosives like Tritonol 80/20 to chemical, nuclear or thermonuclear types. <S> Some ballistic missile contain multiple and independently targeted warheads on a warhead bus. <S> Cruise missiles are essentially guided flying bombs - unmanned heavier than air aircraft capable of sustained, powered flight from launch until it reaches the target. <S> They range in speed from subsonic to supersonic. <S> Propulsion is generally provided by small gas turbine jet engines, though some of the newer, supersonic types are powered by solid fuel ramjet engines. <S> Warheads carried are conventional, chemical or nuclear. <S> Some of the best known cruise missiles are the AM39 Exocet anti-ship missile or the BGM-109 Tomahawk missile.
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A cruise missile is rocket or jet powered and flies to its target within the atmosphere, using lift to stay up.
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Can small airplanes be towed (or carried) as cargo to be dropped at some other location by air? Is there any present technology where a large plane can carry a small plane (or multiple small planes) and drop it midair where the small plane deploys itself? This would be very good from defense point of view, where small fighter jets with limited range could be dropped off by large airplanes with very long range. <Q> I'm not too sure about having an aircraft drop out of a cargo bay such as the C-130. <S> On a side note military gliders were used extensively during WW2 and some were capable of carrying light tanks. <S> The gliders were usually towed behind larger bombers to give them the required altitude and speed. <S> They were used because of their wooden construction allowing a stealthy approach due to the reduced radar signature. <A> Parasite aircraft is a concept that has been considered. <S> However none of these projects where realized before the end of WWI. <S> During WWII soviet used Tupolev TB-3's to carry I-16 dive bombers, a culmination of experiments started during the 1930's. <S> Some of Japan's kamikaze crafts where also launched as parasite aircraft. <S> In an escort role Germany experimented with parasite craft solutions as a way to bypass the very short operational range of rocket powered fighters, but these experiments where ultimately judged unsuitable. <S> The extreme range of US strategic bombers in late WWII and early cold war lead US to consider parasite fighters as an escort solution. <S> However these attempts where eventually scrapped in favour of aerial refueling, as this was considered a safer option. <S> Source: https://en.wikipedia.org/wiki/Parasite_aircraft <A> small fighter jets with limited range could be dropped off by large airplanes with very long range <S> That sounds like a one-way mission. <S> Some Zeppelins and some US Navy airships did carry small aircraft that could be both launched and, importantly from the pilot's perspective, recovered in mid-air. <S> However in the modern world, the approach you describe is not used. <S> If fighters are needed beyond normal operational range of their bases, air forces will either use in-flight refuelling or create a forward operating base nearer the mission target. <S> Aircraft carriers are a popular solution to this requirement, if adequate time is available. <A> Since your question is about the tech, it very much does exist in a few forms at least for aircraft of varying size. <S> The Bell <S> X-1 <S> (the plane that broke the sound barrier) was a mid flight deploy from a B-29. <S> This was a result of its low fuel load it could not really get its self off the ground and then have enough fuel to break the sound barrier. <S> This became common for a lot of the high speed test crafts developed over the years. <S> Up through the X-15 <S> (the fastest thing out there) <S> The first space shuttle tests were done by flying the shuttle to altitude on a modified 747 and deploying it for an unpowered decent so the tech is there even for large craft. <S> The more modern Space Ship One also uses this configuration to get it to altitude easier. <S> The tech is there and has been used over the years. <S> Now to the more realistic question "would you do it" most likely no. <S> As you mentioned there is a case for small limited range planes being deployed at distance but the simpler solution to that is a mid-air refuel . <S> This accomplishes the range extension and allows the plane to get back home. <S> The other option is a drop tank which also extends the range of a plane. <S> Note: <S> Another kinda of cool solution to the problem was to weld 2 planes into one like the North American F-82 Twin Mustang . <A> This would be very good from defense point of view, where small fighter jets with limited range could be dropped off by large airplanes with very long range. <S> Parasite aircraft as a way of increasing the range of fighters has been tried repeatedly, with everything from airships to heavy bombers as the mothership. <S> It turns out to be much harder than it sounds, and has generally been abandoned in favor of dedicated tankers and mid-air refueling. <A> The most common combination was a Fw-190 figher/bomber carrying a Ju-88 drone. <A> where a large plane can carry a small plane (or multiple small planes) and drop it midair where the small plane deploys itself <S> In addition to those concepts, let us not forget the Goodyear Inflatoplane , which was designed specifically to be dropped from aircraft, inflated, and flown away. <S> Designed for pilot rescue, the idea of dropping an aircraft in and flying it out was revealed to be ultimately impossible when one considers pilots in a Vietnam jungle.
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During the era of the zeppelins several countries experimented with launching fighter aircraft from airships, mainly as a way to get the fighter crafts to a relevant altitude while conserving fuel. If you are talking about externally carrying/deploying other aircraft, this has already been done with the B-52 (albeit for testing purposes) carrying the X-15 . Germany had some (very) limited success in WWII with the Mistel concept, which is basically the opposite of what you mentioned: The smaller of two craft was the piloted one, the bigger craft being an explosive-carrying drone -- like a really big glide bomb.
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Does 3D Thrust vectoring (TVC) provide improved maneuverability over 2D TVC? What are the additional capabilities that 3D thrust vectoring (TVC) provides over 2D thrust vectoring? <Q> Thrust vectoring allows to control an aircraft when the airflow over its control surfaces has separated. <S> Before thrust vectoring, the range of angles of attack in which an aircraft could be controlled was rather restricted. <S> With the X-31 , it was for the first time possible to control a completely stalled aircraft, which enabled much quicker maneuvering in order to get the nose pointed at an adversary. <S> This was powerfully demonstrated by mock air combats with an F-18 . <S> The X-31 used a rather simple arrangement with three paddles at the engine exhaust, and this allowed to create both pitch and yaw moments. <S> This makes it what you call a 3D thrust vectoring aircraft. <S> Modern thrust vectoring nozzles are round and allow to deflect the thrust by up to 20° in both pitch and yaw, making them also what you call 3D. <S> However, this geometry will scatter radar waves in all directions, which makes it unsuitable for stealth aircraft. <S> Therefore, stealthy designs can use only two straight vanes above and below the jet exhaust, which will create only pitch moments. <S> This is what you call 2D thrust vectoring. <S> When two engines are installed, differential deflection will allow to create limited roll moments, but the powerful side forces which allowed the X-31 to rotate its nose (and radar) quickly into the path of its adversary will no longer be possible. <S> Stealthy thrust vectoring will still allow to control the aircraft at all angles of attack, but the yaw rates possible with a regular thrust vectoring nozzle are no longer achievable. <S> This, and the structural mass of a rectangular exhaust, are the distinct disadvantages of stealthy nozzle designs. <A> Consider the Su-30 "SM" and "MK" variants, which have 3D thrust vectoring. <S> Here's a Su-30 at an airshow <S> (I'm unsure of the exact variant) performing a range of post-stall aerobatics: <S> https://www.youtube.com/watch?v=ujenrmoeALE <S> Many of these maneuvers require the pilot to be able to kick his rear end to one side or the other without the aid of aerodynamic control surfaces (such as the post-stall Immelmann, the J-turn, the Super Cobra which basically stands the jet on its tail in mid-air, etc) and thus could not be performed, at least not to the same degree, by an aircraft like the F-22. <S> The utility of such maneuvers in aerial combat is unknown and probably low (standing still in mid-air is more likely to get you shot down than to provide any tactical advantage), which is one reason why full 3D vectoring hasn't been added to U.S. fighters <S> (there was some talk about applying the systems seen on the F-15 ACTIVE and F-16 VISTA to combat planes, but nothing serious ever came of it, and most of those airframes are now slated for retirement). <A> An aircraft always needs "3D manoeuverability" (pitch, yaw, roll). <S> Whether you use TVC to perform one, two or all three functions, exclusively, or in combination with aerodynamic control surfaces is a matter of design choices and optimization. <S> The choice truly depends on what are the requirements of the aircraft in question. <S> Note that TVC in itself is not necessarily "better" than conventional control surfaces on the wing and/or tailplanes. <S> Aerodynamic control surfaces are very efficient (with enough speed), but take some space and induce loads in the airframe. <S> Ailerons on a wing take space that could be used for flaps. <S> Tailplanes are a pure cost of weight and drag that you pay for maneuverability (and stability). <S> TVC costs a lot of weight and complexity, but in turn has little to no direct penalty on drag. <S> However, note that it has a rather limited efficiency (which is directly tied to the thrust of the aircraft -- which is not so good <S> : ideally you want thrust and attitude control to be independent). <S> Maneuverability always has a cost. <S> So the question really is: For a particular aircraft configuration , and for a particular requirement of maneuverability (in pitch, yaw, roll), and for a particular combination of optimization criteria (minimize weight, drag, costs, complexity,...): What is the combination of aerodynamic surfaces and TVC (and other means) that meets the requirement while minimizing the criteria?
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In short, yes; the ability to vector thrust to the sides of the aircraft, inducing yaw, does provide an advantage in maneuvering over pitch-only vectoring.
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Can a commercial airliner be too heavy to take off? According to this question's answers, MTOW (or MTOM) is the Maximum Take Off Weight, which is everything up to and including trip fuel. Then there is one step above that, MRW , or Maximum Ramp Weight, which is MTOW plus fuel used to taxi out to take-off. Can a plane be given too much roll-out fuel, so as the plane is actually too heavy to take off, without having to do perhaps another lap around the airport? My thoughts are that there are simply no scheduled flights which require a total amount of trip fuel that would make roll-out fuel cause the plane to be too heavy for take off. EDIT: Although (in a comment) I am asked to possibly change the title of the question to fit more closely (include fuel), after considering it, I've decided to leave it alone. It is unlikely that a plane would be loaded to the point that it is too heavy to take off, before fuel is added. I believe it would be a 100% certainty that it was the addition of fuel that will make (all)(commercial) aircraft go beyond MTOW. There might be some edge cases of contents (payload) being too heavy, but if that were the case the plane would not even be considered for take off (without fuel). <Q> It is possible to arrive at the runway with too much weight to takeoff, but this result is generally a mismanagement of fuel. <S> The most likely scenario this happens is when you are going to be at MGTOW for takeoff but need fuel to get to the runway (putting you over MGTOW at the gate) and are anticipating a long taxi or long lines at a de-ice pad. <S> If the long taxi doesn't materialize this can result in getting to the runway with too much fuel. <S> Recognizing this, fixing it is often as simple as taxiing with both engines instead of just one. <S> If you are really overweight <S> you just ask to get put somewhere <S> you can wait while running both engines and wait for the weight to come down. <S> There is really no benefit to taxiing around the airport versus just waiting in one spot to burn fuel. <A> The amount of extra fuel needed would be marginal; a couple hundred pounds at most, just a few minutes' worth at anything more than idle power. <S> You're also correct that the operator of the plane wouldn't be too eager to test these maximums with any fleet aircraft, and will have their own more conservative guidelines for loading an aircraft. <S> These guidelines are typically only approached by cargo jets; people are relatively low-density given the amount of cabin volume required for each passenger. <S> But, such limits are the reason, for instance, behind airline policies on number of checked bags (and the cost of each one) and the maximum weight of each one; more bags, and/or heavier ones, increase fuel requirements. <A> The MATOW (max allowable takeoff weight) isn't only limited <S> it's structural weight limit (MTOW) but is absolutely limited by other factors. <S> For transport category aircraft these other factors can limit max allowable takeoff weight. <S> Max structural weight Brake energy for takeoff <S> Wheel brake cooling limits <S> Maximum tire speed Required gradients for first, second and final segment climb to 1500' AGL. <S> Required runway distance to verify the takeoff weight will produce a runway distance below all runway declared distances. <S> Obstacles in the takeoff flight path <S> The pilot in command is required to verify they do not takeoff above any of those limits. <S> The airlines have dispatchers that will calculate this information. <S> If a mistake is made, it is possible to be loaded above the max allowable takeoff weight and not realize it. <S> Most of the list above is accounting for an engine failure below or above the decision speed.
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Correct on virtually all points; it is possible for an aircraft with high payload or long range expectations to require more fuel be loaded at the gate than it could make it off the runway carrying; however, it wouldn't have to lift off with any fuel it needs to burn just to get to (or even down) the runway.
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How did SR-71 spy, flying at 80,000 ft and 3500 km/h? The SR-71 Blackbird is a famous supersonic reconnaissance/spy aircraft, undoubtedly one of the most amazing flying machines ever. Now, with the capabilities it had: Maximum speed: Mach 3.3 (2,200+ mph, 3,540+ km/h, 1,910+ knots) at 80,000 ft (24,000 m) How was it used for spying? It must have been difficult to focus on any object on the ground, from such a great height and then many problems are encountered with high speed photography. How were these and many other problems overcome? <Q> The SR-71 Blackbird was equipped with specialized cameras. <S> It would overfly the area of interest and take high-resolution pictures of the ground. <S> Of particular interest is the Technical Objective Camera (TEOC). <S> It could shoot pictures with a 6'' resolution from the operational altitude of the SR-71. <S> This task was not simple as the aircraft would have moved several hundred feet forwards during the exposure time of the picture which was (depending on the settings) around one or two tenths of a second. <S> Without some kind of correction, this would have resulted in a picture that was blurry in the direction of motion of the aircraft. <S> To solve this, the velocity over height ratio number was fed to the camera, either manually as computed by the pilot or automatically as computed by the sensors and computer of <S> the SR-71 (and it turns out that the machine did a better job at this than the pilot) and while the picture was taken, the high-precision mirror that directed the camera FOV downwards would rotate in the opposite direction towards which the airplane was moving, thus cancelling it out. <A> This is the section of the original SR-71 operation manual that describes in detail how the camera works. <S> It provides continuous ------- or --------- coverage along the flight track through an angle of 70 degrees on each side of the aircraft. <S> Note: <S> the ----- are blacked out sections in the manual. <S> The manual goes on to talk about the operations of the camera and also notes that it takes 5 inch film with is way bigger (and subsequently higher "resolution") than the 35mm you would use in a home camera. <S> Here are the actual cameras. <S> The left is the Technical Objective Camera and the right is the Optical Bar Camera. <S> source <S> The resolution of the TEOC was pretty great Programmable system with a 48 inch focal length. <S> The TEOC resolution was 110 lines per millimeter, which equates to about 6" ground resolution from an operational altitude. <S> The TEOC's were mounted both sides of Chine controlled by a computer <S> The OBC seems like it may have been more size than resolution <S> The OBC could photograph 100,000 square miles of the Earth's surface per hour. <S> Film image 72 miles wide, & film length <S> 10,500ft. <S> And of course you cant have a fancy plane with out lots of buttons and knobs. <S> The control systems for the cameras looked like this <S> For what its worth it seems that both of these cameras were really high tech <S> panning control systems for cameras. <S> They are very similar to Equatorial Mount cameras which are used to photograph stars (since the earth is moving), it's also called a barn door tracker . <S> ( image source, all images ) <A> Yes, the OBC (by Itek) did have 10,500 feet of 5" wide very fine grain Kodak film. <S> As I recall, in non-overlapping mode it could cover over 2900 miles of terrain, and in stereo (overlapping mode) 1300 or so miles. <S> So, each negative was 4.5" x 72". <S> It also had v/r sensors and servos to tilt the view fore & aft during each exposure for image motion compensation as in the Hycon TEOC. <S> The OBC principle was utilized in other reconnaissance aircraft at lower altitudes as well.
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The plane was equipped with an Optical Bar Camera "The Optical Bar Camera (OBC) is a high resolution panoramic camera with a "folded" ----------- lens system.
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Would it be possible to use 3D printed node based structures to make cheaper GA planes? A car boasting 700HP and under the U.S LSA weight limit was just announced by Divergent Technologies . I was curious on peoples thoughts on using this technique in planes. Obviously there are some issues with the surface of the structure bearing load, but I imagine these could be overcome. <Q> 3D printing is unlikely to make anything cheaper in the near future. <S> With current printing technologies it's an order or magnitude or two more expensive per unit than volume manufacturing techniques such as extrusion or injection moulding. <S> It's notable that the company you link to chose to make a supercar rather than a low-cost small car. <S> There's little price competition in that market, as brand loyalty dominates. <S> Most supercars are bought as status symbols or for fun rather than for their actual road performance. <S> Most of the incumbents manufacture very small runs with a lot of hand assembly: exactly the kind of manufacturing that 3D printing is competitive for. <S> On top of that, because of the status symbol marketing, there's huge room for new players to differentiate based on a green image. <S> Tesla has done this in the last few years, which is why some of DMF's marketing material focuses on dissing electric cars. <S> Runs are small in GA too, so there's potentially a wider niche for these techniques to fit into. <S> The market that would most closely fit IMO is kit aircraft. <S> A kit that's primarily 3D printed parts joined by standard spars, with a flexible outer shell, could have shorter lead times and less tooling cost. <S> After discussing this with some mechanical engineer colleagues today, they pointed out how 3D printing of metals is now being used as a complement to CNC machining in the rocket industry. <S> For a part that has to be machined from a single piece of metal, they 3D print a shell that's slightly larger than the required shape, and then machine it to the correct shape. <S> It allows you to achieve the tolerances you get from machining (which 3D printing can't yet deliver), but without the waste you get from cutting down a solid block. <S> It's an aside to the main question, but it's a way that 3D printing could be used to reduce the cost of some components and allow designs that would have been economically infeasible. <A> 3D printing is still an emerging technology. <S> It's far from practical as a primary manufacturing method, but it is certainly possible as parts production - it is vastly cheaper to maintain a database of instructions than a warehouse of parts. <S> Printers capable of making 1000cm$^3$ parts out of structural plastics like ABS are readily available on Amazon for $600. <S> If you need bigger, the price goes up. <S> A lot. <S> Airbus at one point was experimenting with 3D printing of sintered metals. <S> If that ever works out it will revolutionise the spare parts industry, probably not in a good way. <S> As Dan said, kit and model aircraft will be early adopters. <S> Obligatory xkcd <A> As the other posters have said, these parts are not cheaper than parts produced using other technologies. <S> However, our 3D printers have vastly increased the efficiency (and decreased cost) at which we can design new products. <S> Although 3D modeling of new parts in software goes a long way, being able to actually use the part in a prototype is a complete game changer. <S> And by printing out modified designs we can dramatically shorten the feedback loop to arrive at the "right" design. <S> I would suspect that use of this technology by aircraft manufactuers could therefore decrease the cost of design which might result in decreased costs overall. <A> The comments here are on point however I would like to mention that its very actively being looked into. <S> GE successfully 3D printed a full working mini jet engine . <S> That in and of its self is a pretty cool accomplishment. <S> However it should be noted that the cost may not have been fully considered for that particular project. <S> GE also has at least one FAA cleared part that is 3D printed . <S> It is a part for the GE90-94B jet engine . <A> The only kind of 3D printing process which produces structures fit for the load/weight ratios usual in aviation is electron beam printing. <S> It uses titanium, stainless steel or aluminium grains (feels and looks much like sand) and heats that up locally to the melting point in an inert atmosphere, layer by layer. <S> The advantages are: Very fine structure, better than what is achievable by casting. <S> No molds. <S> Geometries which would be impossible to mold by casting or milling. <S> But there are disadvantages: <S> Rough surface; minimum roughness is given by grain size. <S> The surface imperfections translate into a notching effect, so the actually usable cross section is smaller than what is produced, which reduces material efficiency. <S> Manufacturing cost hardly goes down with the number of parts. <S> The only areas where this has been used gainfully so far are special cases: <S> Titanium implants, where replacements for bone structures can be custom-made within less than 24 hours. <S> The rough surface is an advantage here, because it allows better integration into the body. <S> Replacement parts in case a JIT assembly line is compromised by one part missing. <S> Impossible geometries like hollow core pins for injection molding. <S> The channels for the cooling water inside can have a corkscrew shape, one for the inflow, and one interleaved for the outflow. <S> The gains in process efficiency can be immense. <S> In general, a 3D printed airplane is possible. <S> Cost savings can be realized for a few special parts, but the general structure would certainly be more expensive. <S> Consider that the surface roughness means that at least aerodynamic surfaces and contact areas with other parts need to be planed (e.g. by milling) after 3D printing. <S> While a single-issue sports car might be cheaper to produce this way, I very much doubt that GA manufacturing will benefit from 3D printing soon, even with the reduced production volume of today, except for some special parts.
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I work at a company that routinely uses 3D printers for design of new components - although not for the aviation industry.
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What is the highest possible thrust generated by 15cm ducted fan? I recently developed a sudden interest in flying. I'm wondering whether a pair of small ducted fans could lift a person off the ground. Lets say the ducted fan is 15cm in diameter. What would be the most thrust a fan like that could produce? <Q> A 15cm diameter fan could maybe lift 4 KG of mass with a tip speed of 0.6M. <S> By increasing the power and the blade chord length (in other words, increasing the solidity of the rotor), this may be increased to maybe 6KG or more, but a single fan would probably never lift more than 10KG mass. <S> The thrust of a rotor is $CT <S> \cdot <S> \rho \cdot <S> Area <S> \cdot <S> tipSpeed^2$. $\rho$ = air density (1.225kg/m^3 at sea level). <S> $Area$ = area of rotor disc (m^2) <S> $tipSpeed$ = <S> the linear speed at the tip of the rotor = radial speed <S> * radius. <S> $CT$ = coefficient of thrust. <S> (is usually in the order of 0.02 to 0.05 for small rotors) <S> Assuming $CT$ of 0.03, the calculation shows 40N (=4 KG) thrust. <S> Disc area is one of the most important parameters, even a 30cm disc would generate 4 times the thrust. <S> 60cm would make almost 65 KG. <S> So two of them could carry and maybe even lift-off a person equipped with this backpack (the person + the system must be less than 90 KG). <A> Calculating Thrust <S> One design required sixteen 20-inch (~50 cm) propellers to lift a person. <S> These were unducted <S> but I doubt that any 15cm ducted fan produces more thrust than eight 50cm propellers can. <S> See Autonomous human transport for details of how the designer calculated thrust. <S> He used Thrust (pounds) = <S> R 2 D 4 <S> T c where T c is an empirically measured constant for which he had a value of 2.7734 x 10 -12 . <S> R is RPM, <S> D is diameter (inches). <S> I imagine max RPM might be limited by the need to keep the fan tips subsonic (e.g. < M0.5). <S> Note <S> that thrust is shown as depending on the fourth power of diameter, sixteen 50cm propellers will therfore produce <S> about 1000 x the thrust of two 15 cm propellers of the same design at the same RPM. <S> Ducted vs Free <S> It seems you need to be careful when comparing ducted fans with propellers. <S> Using higher RPM to compensate for smaller diameters results in lower efficiencies (you need bigger motors). <S> Small diameter, high disk loading ducted fans are often conceived to allow the use of a high rpm engine running a direct drive propeller. <S> While these highly loaded fans (if properly designed) will be more efficient than a free propeller of the same diameter, they typically won’t match the efficiency of a larger free propeller (of much lower disk loading) From Duct Myths, Duct Physics Twin ducted-fan backpack <S> The $150000 <S> Martin Jetpack uses two ducted fans powered by a 2-litre two-stroke engine of 200hp (~150000 watts?). <S> The fan diameter looks much larger than your 15cm. <S> The width of the machine is given as over 2 meters <S> so I'd estimate the fan diameter is close to 80 cm. <S> The company website doesn't say how they calculated thrust. <S> From their use of larger diameter fans I'd guess there are reasons that 15cm fans are unsuitable. <S> Related <S> What are the advantages and disadvantages of ducted fans in designs such as the Airbus E-Fan? <A> An Apache AH-64 has a rotor that's <S> about 100x times the diameter, so the swept area is 10000x larger. <S> It can lift around 10000 kg, which means your ducted fan would lift about 1 kg. <S> You'd need 2 fans with approximately one meter diameter. <A> Here are technical data for existing 15 cm EDF from Schübeler Technologies GmbH https://www.schuebeler-jets.de/en/products/hst-en <S> Technical Data <S> DS-130-DIA <S> HST® with DSM 7857-470: <S> Inner shroud diameter: 152 mmFan swept area: 130 cm²Weight incl. <S> motor, wires, connectors and Secure Fan Fix: 1750 gStatic Thrust Range: 135 – <S> 175 N Thrust range: 92 – 105 m <S> /sExhaust speed range: 17.500 – 20.000 rpmInput <S> Power: 8,0 – <S> 12,0 kWAllowed battery: 12 – 14S 14000 mAhOverall efficiency:76 – 74% Regardsblue
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Apparently, a 50cm diameter disc can possibly generate 45kg thrust on its own.
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Are drones used in firefighting, agriculture and pest control? Well, as the question says I am interested in the use of drones in agriculture. Are there any drones designed to carry a tank of some chemical or water? How large are those tanks? I have seen that airplanes are used in agriculture and in extinguishing forest fires. They can carry tanks containing 500-2000 kg (or more) of chemicals/water. <Q> I once worked in the UAV company, which was contracted to supply a system to identify trees. <S> To achieve this, all you need is a good camera and an image recognition software (now to be easily written using .NET). <S> I have not heard about drones carrying such large amounts of chemicals, so sorry about that. <S> In this part of the world (eastern Europe) we have enough of our own, conventional planes which do the job just fine (like PZL-106 Kruk). <S> I guess buying drones to do that would not be economical (again I'm just speaking for my country) <A> These guys seem to offer some products in that space however it seems many of them are of the remote control variant (not fully automated). <S> Crop dusting is a pretty routine task and you could easily program a drone to cover a specific field at a given time and let it do its thing. <S> The main issue you will face in the current market is simply useful load. <S> It does seem that the FAA has approved <S> some drones for this use <S> but that was recently <S> so Im sure it will be a little while before we see them. <S> Although it seems Japan has been using them for this purpose for some time. <S> So yes tank carrying drones do exist ( <S> but I cant find the volume of the tanks, they do however appear pretty small). <S> FWIW any small drone could be modified to carry a tank and spraying device <S> provided <S> it could lift it. <S> All things considered people have built some pretty big RC planes <A> I am not an expert, but i have seen a few times Octocopter being used in agriculture industry. <S> To carry a thanks of chemical or maybe for watering down purposes, it need 8 rotors to make it more stable. <S> But it is depend on how large the farm or the area <S> you want the drones to be utilized. <S> I have seen some farmers will custom or attached something like arm to drones. <S> It depend on the load that specific need to carry or how you want to use it . <S> Hexacopter or maybe quadcopter if only for simple task or experiment. <S> But to see Octocopter do the job is normal for me. <S> Seen dozen of times.
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Ignoring the military drones out there most of the commercially available unmanned vehicles are on the smaller side and simply don't have the useful load of something like a Piper Pawnee that is used for current crop dusting.
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Why do fighter jets land faster than Jumbo commercial aircraft? From my own understanding, the bigger (and heavier) aircraft, the higher approach speed it needs to keep itself from stalling. According to this site , the approach speed of an A380 is 140 knots, and 160 knots for a 747. In contrast, the F-16's landing speed is 141 knots, and 135 knots for the F-35C. Doing mass-to-speed ratio, it doesn't make any sense to me. Could you explain why do fighter jets land faster while they are lighter than large commercial aircraft? <Q> It is not only the mass that affects the landing speed. <S> Wing area plays an important role as well. <S> A larger wing can lift more weight at the same speed than a smaller wing. <S> If you compare the wing loading of these aircraft the differences are smaller: A388: <S> Maximum landing weight: 391000 kg Wing area: 845 m 2 Wing loading: 463 kg/m 2 <S> B744: <S> Maximum landing weight: 295000 kg Wing area: <S> 525 m 2 Wing loading: 468 kg/m 2 F-16A: <S> Estimated landing weight: 13000 kg Wing area: 28 m 2 Wing loading: 464 kg/m 2 <A> For airliners you have to take into account that the wing airfoil is radically different than the wing airfoil from a fighter jet <S> : airliners have flaps that modifies the airfoil and doing so the lift and trail (not sure of this word in English) modifying the speed range of the wing (reducing the stall speed) and so allowing slower speed for landing. <S> In the case of a fighter jet the wing is in general a delta wing without flaps, so in order to reduce the speed for landing they have to increase the angle of attack to augment the trail without loosing too much lift. <S> That why in this phase they cannot lower too much the engines and the speed, because their wings are not suited for low speeds. <S> If you look at the Concorde (a good example of delta wing) they had to put down the nose during landing phase to be able to see the runway because of the high attack angle requested to be at the right speed (about 180-190 kt). <A> Because they are lighter, they have less kinetic energy <S> so there is less to dissipate. <S> This is easier on the brakes. <S> Remember kinetic energy is $E_k=\frac{m <S> \cdot <S> v^2}{2}$. <S> Also fighter jets aren't as good gliders as jumbo jets. <S> This sacrifices lift for maneuverability, so they have better acrobatic performance. <S> While airliners will spend most of their airtime going straight ahead at high altitude so they benefit the most from being good gliders. <A> To simplify, the differences are similar to comparing a dart to a glider -- it all gets back to the wings. <S> The delta wing provides the best overall flight characteristics in terms of lift and control surface efficiency. <S> A delta wing will allow you to come in low and slow and in control, but is that always what you need if you are flying a fighter jet? <S> The aerodynamics of fighter jets are designed to provide lift, stability, and control at a much wider angle of attack. <S> Comparing the wing characteristics between the two planes in a wind tunnel, notice how the wing thickness (airfoil) of the fighter plane is much less (relatively flat) at the leading edge. <S> Shut down a fighter plane engine, and it will drop like a yard dart. <S> The intake on a fighter plane is designed to receive as much air as possible, and will cause turbulence at the inlet if the blades are not turning fast enough. <S> There simply is a minimum speed range to keep the plane in flight and under control as it is coming in for a landing. <S> The power to weight issue has a downside -- the fighter plane is less efficient in fuel consumption -- it is even less efficient if the inlet has nacelles or ducting to mask a thermal signature. <S> The power to weight ratio of the fighter plane is much higher than a commercial aircraft, and the answers above from the other posters regarding thrust cover the topic well. <S> The best fighter jets provide the most maneuverability over the widest range of speeds. <S> Both types of aircraft would technically benefit from a lower landing (and stalling) speed, but in both cases, other flight characteristics are a higher priority. <A> Here's another factor in approach speeds - the military fighter/trainer aircraft I flew used 1.2 Vso (20% above landing configuration stall speed) for approach. <S> Airliners are required to use 1.23 Vso and each model uses a different multiplier which often changes with different flap settings. <S> The previous generation 727/757/767 mostly used 1.3 Vso while the newer airliners use 1.25-1.28 Vso. <S> That difference reduces a fighter's approach speed by 4-8% vs what an airliner would use. <S> Light airplanes use 1.3 Vso, or 30% above stall speed, for their approach speed.
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Although the fighter plane provides less lift at the same angle of attack and requires a faster airspeed to stay aloft without stalling, the control over a wider range of airspeeds is worth the tradeoff for the fighter jet performance and maneuverability. Landing speed varies depending on several factors.
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Could the non-smoking sign still be turned off in modern airplanes? Yesterday, I flew on Germanwings 4U2379 with an Airbus A319. The plane's interior looked pretty modern, and while I can't find a construction year online, I'm pretty sure it was built way after the total smoking ban. This plane still had illuminated non-smoking signs though and I was wondering if the crew would actually be able to turn these off during flight if they wanted to. Is there any information about that? This question shows that some planes do not even have a non-smoking sign anymore, but it does not elaborate on the mechanics of existing signs. <Q> It would appear that the aircraft you flew was D-AGWR, a A319 with MSN (Manufacturer Serial Number) <S> 4285 delivered in April 2010 (hence fairly new). <S> There is a switch at the bottom of the overhead panel, next to the seat belt sign, slightly right of the middle. <S> Flip it and they will extinguish. <S> The functionality is a bit more complicated than it would appear, since it feeds into the central aircraft electronics. <S> Olivier Cleynen at Wikicommons <S> Out of interest, this button no longer exists on the Boeing B787, suggesting that it is on the way out. <S> Only the seat belt option remains. <S> The slots for no smoking are being increasingly 'redeveloped' into a sign for electronic devices instead on some types. <S> They just put a no smoking sticker on the seat in front of you to fulfil the same function. <S> I do not know if they cockpit text has been modified on the aircraft that undergo this modification. <S> Source <A> In extremis , every electrical item on a plane can be switched off, to protect the plane if the item malfunctions. <S> For example, a short-circuit in the no smoking signs could, in principle, cause a fire. <S> At the very least, there will be a circuit breaker that can be removed to remove power from the signs. <S> However, I don't know if there would be an individual breaker for that system: there might be a single breaker that isolates several related systems. <A> Since this chime is audibly distinct from the usual high-low F/A Call chime, it could be used as a method of notifying the cabin crew (although I don't know if or how often it's actually employed that way).
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One option, used by at least some airlines, is that while the lighted "no smoking" signs have been replaced by placards (no lightbulbs to ever need replacing), the cockpit switch itself still works in that it produces a single tone chime when turned on or off.
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Why are Russian cockpit panels painted in turquoise? Almost all cockpit panels of Russian aircraft types are painted in turquoise, whereas elsewhere the cockpit panels usually exhibit a dark grey color.As this "rule" seems to be quite prevalent, I am curious as to the reason/origin. This can be seen in the cockpit of Mikoyan MiG-31 : Image Source <Q> ... <S> the scientists found out that this color keeps pilots awake and not getting tired by the black or grey of a cockpit panel, especially under terms and condition of long range flights or under heavy work load. <S> This URL contains a color guide for cockpits. <A> Soviet defector and MiG-25 Pilot Viktor Belenko claimed that this was done because it was found to be more soothing and relaxing for the flight crew to operate in a blue-green painted cockpit. <S> This color was very common in both Russian military and civilian aircraft during the Cold War era. <S> I’m not sure <S> but I suspect Boeing did the same thing when choosing the light earth color for their jetliner cockpits. <A> the real reason is tactical lighting.not <S> all russian aircraft have the turquoise/jade colors cockpits.use red lights for tactical night operation, and very little light can be seen out from the cockpits.russian helicopters and cargo that are design to operate in tactical night ops <S> have also this feature. <A> Years ago I have found explanation on one Russian aviation site. <S> The main reasons why Russian use this shade of green is that it does not create residual picture in your eyes. <S> The same reason why surgeons have green protective robes. <S> You can look inside the cockpit, and swiftly look outside <S> and you will not see residual instrument panel picture.
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According to Cold War Air Museum : ...the color chosen by Soviet designers helps to reduce stress and maintain a pilot's effectiveness on long missions.
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Why do airplanes have to retract landing gear? Why do all the airplanes have to retract their landing gear, once they reach some specific height? Why can't they simply leave their landing gear deployed all through the flight? <Q> In the early days of aviation it was simply easier to have the gear fixed. <S> The landing gear adds drag, but so does a second wing and wire braces . <S> Airplanes generally did not fly very fast or far, so the drag from the landing gear (and that other stuff) was not a big issue. <S> The first design with retractable gear dates to 1911 . <S> Since then, retractable gear has been a design decision each airplane must make. <S> However, this is at the expense of added weight. <S> The retract system, which is usually hydraulic, must be added, and the plane must be designed to make room for the gear somewhere at least mostly inside the aircraft. <S> The plane must also be designed to handle situations where some or all of the gear does not extend properly. <S> For planes that need to be fast and/or efficient, retractable gear is worth the reduction in drag. <S> The additional drag has to be supported by the structure as well. <S> Aircraft with retractable gear will have a maximum speed at which the gear can be extended. <S> Even gear with proper fairings would add significant drag at the speeds airliners fly at. <S> This would be much more critical at supersonic speeds. <S> In these cases the weight of reinforcing the gear could be even higher than the weight of the retracting system. <S> Particularly smaller general aviation planes tend to not have retractable gear. <S> The retract system adds extra weight and complexity (and therefore cost), which will be fairly significant in a small plane. <S> Fixed gear is simple and can be designed to minimize drag as much as possible. <S> These planes do not typically need to fly fast or have large range, so the added drag is less of an issue. <S> Other small planes do have retractable gear, which will allow for greater speed and range. <S> The PA-32 type shown in Dave's answer was later produced in a retractable gear version as well. <A> Short answer: <S> It allows them to fly faster and further. <S> Long answer: <S> Hapag-Lloyd Flight 3378 demonstrated this impressively on July 12, 2000. <S> Destined for Hannover, they did not retract the gear after take-off in Chania, Crete. <S> The fuel was sufficient for the planned distance plus reserves, but the extended gear increased fuel consumption so much that they ran out of fuel while approaching their diversion airfield near Vienna. <S> Fuel consumption enroute was twice as high as it would had been with the gear retracted. <S> Drag is composed of a lift-related component (induced drag, blue line below) and a constant component (zero-lift drag, red line below), and both depend on the dynamic pressure, which is the product of air density and the square of airspeed. <S> While the lift-related component goes up with reduced dynamic pressure, the constant component will go up with increased dynamic pressure. <S> Thus, extending the gear will increase the constant drag component, and while flying slower helps to reduce its contribution, it will drive up the lift-related drag component . <S> In the end, the drag will be higher at all speeds. <S> Typical drag contributions over speed for a glider. <S> The physics for airliners is the same, only the numbers are bigger. <S> In cruise, all airliners try to fly as close to the minimum drag as possible. <S> The only reason for a fixed gear are cost, weight and simplicity. <S> Performance will always suffer from it. <A> Because its a drag to leave it down(pun intended). <S> Some smaller GA planes (and big planes too) can extend the landing gear through a wide range of their operating speeds and use them as a pretty effective speed break. <S> The DA42 comes to mind in this regard. <S> For what its worth there are many general aviation planes that have fixed gear. <S> Retracting gear in a small plane has always been an interesting topic. <S> Some older piston singles have manual retracting gear like the early Mooney M20's which used a Johnson bar to retract the gear. <S> This some what dated system is, by some very sought after for its simplicity. <S> (the big silver bar in the middle is the gear lever) <S> Folding gear also has little to do with aircraft size. <S> The Mooney M-18 "Mite" which is a tiny plane by anyones standards had retractable gear (also Johnson bar operated). <S> One way to reduce drag on a fixed gear plane is through the use of gear fairings. <S> while they do help with speed they can also cause an issue if the plane touches down hard. <S> In some cases (if the wheel is improperly inflated) a hard touchdown or bounce will cause the wheel to balloon out while also spinning which could chafe or seriously damage the fairing. <A> Why do all the airplanes have to retract their landing gear, once they reach some specific height? <S> Why can't they simply leave their landing gear deployed all through the flight? <S> Both questions are false on their premise: <S> All airplanes do not have to retract their gear; many planes are fixed-gear, and cannot retract gear. <S> Some planes retract their gear. <S> Planes can leave their gear deployed all through flight, provided they remain slow enough that the extra airflow drag doesn't damage the airplane and landing gear. <S> Planes that have retractable gear generally retract their gear for improved performance. <S> Not having wheels and struts hanging down streamlines the plane, improves fuel efficiency, enables them to fly faster and higher, and makes for a quieter, more comfortable ride inside the cabin. <S> So, retracting gear is generally desirable. <S> But, as your question suggested, it is not required, and it is not based on a specific height. <S> (if anything, it is based on an airspeed) <A> Simply retractable landing gear is made so as to reduce extra drag which created by the fixed landing gear and hence heavier than air aircraft(airplane) can improve in speed and travel at high speed at higher altitude
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Retracting the gear into the airplane allows for a cleaner form, which reduces drag.
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How are aircraft filmed in sky? We have several spectacular and amazing videos of aircraft, flying high in the sky. How are these videos filmed, at great altitudes? <Q> Two words: chase planes. <S> Here's one article on how that's done , including images captured from both sides; the chase plane (a Learjet 25B) getting the shots of the 787 Dreamliner, and crew aboard the Dreamliner getting a few snapshots of the chase plane. <S> Early shots taken from chase planes often used simple handheld cameras; a two-seater would normally be used with the pilot in front and the photographer in back. <S> This is still a totally viable way to do it, but more modern professional shoots utilize aircraft specifically modified for the task by adding internal or external camera mounts, optical-quality viewports, etc. <S> Here's a modified T-33 used by Boeing specifically for air-to-air photography, including some of the initial publicity shots of the 787 in flight; notice the camera mount between the seats that can be used by the GIB (he's using a handheld in this photo: <S> For lower-speed shots, you can also use a helicopter. <S> Many of these such as news choppers have remote-control cameras on gyro-stabilized mounts, so the vibration of the airframe is minimized in the shot even at high zoom: <S> These same camera systems can be used for air-to-air shots as well, however the maximum airspeed of the helicopter becomes a limiting factor. <S> Still great for publicity shots of small prop planes, or takeoffs/landings. <A> I film all my stuff (from inside the plane) with a GoPro . <S> This seems to be the common way the smaller guys are doing it. <S> There are companies that make mounts that will even hold the camera on outside a plane . <S> You can check out this post from Sporty's on the matter. <S> Some of the stuff shot by the pros may be taken from another plane or a helicopter. <S> The news choppers I see leaving from KPNE have the newer nose style cameras that I assume they operate from the inside of the chopper. <A> You are not specific in your question, so there are many ways that aerial footage can be captured. <S> As Dave mentions , GoPro cameras have gained popularity especially with private pilots. <S> They are relatively cheap, small, easy to use, and capture good quality video. <S> Many videos from inside the cockpit or outside use cameras like these. <S> Air to air footage is taken from other aircraft. <S> For the most flexibility, a fighter jet is a good choice . <S> You could also shoot through the door of a smaller aircraft . <S> Helicopters are best at lower altitudes and speeds but are good for filming takeoffs and landings .
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A few more words: The easiest way to film an airplane in flight is with another airplane in flight.
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How can I take off in a straight line if the runway isn't visible ahead? In a C152, flying VFR, if you point your nose up you wouldn't be able to see the runway, thus it would be difficult to keep yourself aligned to it. So once you take off with a C152, do you climb in a fixed climb rate or do you level off at a certain altitude whilst over the runway, and start your climb again once you've reached the threshold of the runway? <Q> Thats what the compass is for. <S> Continue to fly runway heading according to the compass & heading indicator. <S> While you may not be able to see the runway, you may have other markers. <S> Even a good cloud in front of the airplane can serve as a VFR reference point. <S> Or look out the side to the left-and-right of the plane. <S> You should be able to tell if you're going straight or turning by what you see going past the sides of your plane. <A> Generally speaking you continue your climb after rotation although this will depend on the runway, runway conditions and airport procedures. <S> Soft Field Take Off : <S> In some cases if you are leaving from a grass strip (still technically a runway) you will go for your soft field take off maneuver. <S> In this case you will actually pop the plane off the ground into ground effect as soon as you can(you will be flying at this point). <S> Then build up speed in ground effect (at a level attitude so you can see the runway fine) then begin your climb out when you have sufficient speed at a climb attitude. <S> Short Field Take Off : If the runway is short (or there is an obstacle to clear) you will execute your short field maneuvers. <S> In this case you will take off with 1 notches of flaps. <S> Gun the engine but hold the breaks and let the prop spin up. <S> Then as soon as you hit rotation speed pull back to your best angle of climb. <S> Then when you have cleared your obstacle you can level it out to a normal climb t (best rate or what ever you planed for). <S> In this case clearing the obstacle may be more important than strictly maintaining the runway heading (depending on where the obstacle is). <S> In this maneuver you will focus on your airspeed (to keep from stalling) as well as your attitude indicator and your heading indicator to keep as on course as possible. <S> Air Port Procedures: <S> Some airports have special procedures for departing because of obstacles, air spaces, noise abatements etc. <S> For example I fly out of DYL and they have a procedure on runway 23 that calls for a turn to 250 and climb out to 1200 ft before executing any other turns or maneuvers. <S> Once I have cleared the trees I will usually begin my turn. <S> NOT the compass . <S> Since you are in accelerated climbing flight your compass is inaccurate. <A> When flying a tailwheel airplane or a tandem (two seats, front and rear) with a passenger in the front seat, you can't see much of the runway at all either landing or taking off. <S> I use my peripheral vision to keep the plane centered between the edges of the runway and on track.
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Generally speaking you fly the runway heading after you have rotated and you do this using the heading indicator
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Why couldn't my aircraft depart fully fueled on a 44C day? My flight from Abudhabi to SFO was postponed. Official reason given to us was outside temperatures were too high - around 44+ degree Celsius and aircraft can not take off with full fuel loads at such high temperatures. While sitting at terminal I saw other flights taking off. When I asked staff about those flights, answer was they are short haul - around 4-5 hours distance. How does out side temperature affect these flights? Does it have anything to do with fuel volume changing with higher temperatures and hence wrong fuel consumption calculations? <Q> There are two problems: First, at higher temperatures, the air is less dense; therefore there is less oxygen (by mass) in every cubic metre of it; therefore more air must be ingested by the engine (by volume) for the same quantity of fuel to be completely burnt. <S> If the intake flow rate of air is fixed, then less fuel can be burnt and less power developed compared to a colder air temperature. <S> The second problem is that the lower density of air reduces the lift generated by the aircraft's wings at any speed. <S> To make up for this the aircraft can travel faster. <S> In practise this means that aircraft operating in "hot and high" conditions—altitude also affects air density—will require longer runways to take off. <S> For safety reasons the runway must be long enough for the aircraft to come to a stop if the commander decides to reject the take off at the last moment. <S> But fast, heavy aircraft take a long time to stop; so this means the runway must be even longer. <S> If the aircraft is lightly loaded then it is not such a problem; there is less mass to accelerate and <S> a lower speed must be obtained for take off. <S> Thus a short flight simply takes a bit longer but still gets off the ground. <S> But for AUH-SFO, this is a very long flight and will require a great deal of fuel to be taken onboard (at a guess I would imagine something on the very rough order of 80 tons). <S> The specifics will vary by aircraft, and by how much is on them. <S> https://en.wikipedia.org/wiki/Hot_and_high <A> Does it have anything to do with fuel volume changing with higher temperatures and hence wrong fuel consumption calculations? <S> I doubt wrong fuel consumption calculations are involved, but fuel density is a limiting factor for some aircraft, both insofar as limiting takeoff weight and possibly prohibiting takeoff. <S> For example, for a 747-400BCF, a minimum fuel density of 6.0 lbs/gal is required up to 820,000 lb. <S> From 820,000 lbs to 870,000 lbs the minimum changes linearly from 6.0 to 6.43. <S> From 820,000 to 870,000 there are also takeoff centre of gravity (CG) restrictions. <S> The CG must be forward of 19.1% MAC 1 at 820,000 changing linearly to 19.5% MAC at 850,000, then linearly to 20.0% MAC at 870,000. <S> If you wish to see this graphically displayed, go to section 1-05-001 of the manual at http://terryliittschwager.com/WB/manuals/Boeing_747-400BCF_GPR1_WBM.pdf , pdf page 69 for lbs, 70 for kgs. <S> Also some aircraft have a prohibition against operation in ambient temperatures above a certain point. <S> I seem to remember to remember 54 Celsius for 747-100 and -200 aircraft, but don't hold me to that. <S> 1 <S> MAC = <S> Mean Aerodynamic Chord of the wing. <S> The position of the CG is usually expressed as a percentage of the MAC where 0% is the leading edge and 100% is the trailing edge. <A> There are a lot of complex answers to a rather simple question. <S> As others have mentioned, the pressure of air decreases as temperature increases. <S> This means the fuel in the tanks is being less compressed by the air pressure, thus the fuel makes up for this by taking up a larger volume for a specific mass. <S> Jet airliners measure fuel consumption in mass, opposed to volume. <S> So whilst the volume remains constant, environmental conditions can alter the amount of mass it takes to fill that volume. <S> Simply put, a "full" tank (considered by volume) would weigh more on a cold day than on a hot one.
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If it gets too hot then the aircraft might not have enough runway to get airborne.
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Why fewer operations on weekends? Why are there fewer air carrier operations on weekends? Looking at PHX data, we have the following annual trend that clearly shows a weekly drop of about 8% on weekends: and when I average the data a strong weekly pattern is evident: Is this simply telling us that most traffic is business related? Or is it, in part, that major cargo haulers don't work as much on weekends? As the charts show, we're talking about a 1200 vs 1000 daily operations difference. <Q> Your data TELLS us that the airlines schedule fewer flights on the weekends, from which we can INFER that there is less demand for travel on those days. <S> (The numbers of cargo flights at PHX are dwarfed by the numbers of passenger flights there. <S> The data at a major cargo hub like MEM or SDF might be different in that regard.) <S> To what extent that is driven by business travelers or leisure travel patterns, is beyond your data, and might even get into some fairly complex data and calculations that USAir and Southwest and others use to build their schedules. <A> Businesses work 5 days a week. <S> Non-business travel happens 7 days a week. <S> Other factors kind of even out: Business travel can still happen on the weekend, but ticket prices are normally cheaper mid-week which attracts non-business travelers. <A> After further study, I believe the answer is that the weekday vs weekend effect is caused by business travel. <S> The effect is present at major hubs and weakly present at locations that are either strongly recreational, or are not obviously major business destinations. <S> For example, Aspen shows a fairly uniform day of week distribution: <S> while the annual data shows obvious trends associated with winter and summer recreational activities.
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Also, at smaller airports, it might be difficult for airlines to modify the number of flights that support business travelers.
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Could turbine or compressor stages of a jet engine be switched off to improve fuel efficiency? Active fuel management is a technology developed by General Motors, which is used to improve engine efficiency in the times when the engine is operating under loads which are considerably less than the rated load, as shown in this link . This technology exploits the property of piston engines where some of the cylinders are turned OFF while only few of them work, and hence improving the overall efficiency of the engine. Can a similar technique be employed on an aircraft's engines, where some of the turbine stages (Compressor or Turbine) are switched off in order to improve the performance efficiency of the engine? <Q> As seen elsewhere jet engines are a single block mechanically locked together: <S> all the stages (compressor AND turbine) connected to the same shaft. <S> If the shaft turns, all connected stages turn with it. <S> You can have designs with multiple shafts, but this increases the complexity (design and maintenance) heavily. <S> Even if we assume for a moment that you could have 1 shaft per stage, stopping one of these would be generally a bad idea. <S> For acoustic reasons the number of blades on the stationary part of the stage and those on the rotary part must be prime to each other <S> (example: 37 blades on the stationary side and 39 on the rotary one); this means that when the rotary part stops you cannot align all the blades with the stationary ones, creating drag and losses within the engine, thus reducing the efficiency. <S> How would efficiency of a Jet Engine change, if we assume for a second that <S> its a possibility, to stop a few stages(turn them into free instead of locked)? <S> You would still decrease the efficiency: compressor stages are the ones actually pulling the aircraft forward (you would then produce less thrust <S> *) <S> and the turbine stages are the ones extracting energy from the exahust. <S> *: you could even risk having the flame going upstream if you stop too many compressor stages and not having enough pressure at the combustion chamber inlet. <A> Can it be done? <S> Yes <S> Has it been done? <S> Yes Wait, <S> what?! <S> Where what how? <S> The Pratt and Whitney J58 was designed to allow partial shutdown of the compressor. <S> It does this by placing a distinctive spike in front of the compressor assembly. <S> However the purpose of the transition to ramjet that is distinctive of the J58 was to allow it to avoid overheating the turbine during supersonic flight, where the increased inlet velocity translated to additional heating of the air. <S> However this does not increase the efficiency of the jet engine at all. <S> Overall you actually want as many stages as possible for subsonic flight. <S> This is because multiple stages allow the gas to compress/expand more adiabatically, leading to better Carnot efficiency. <A> Short answer: <S> No. <S> Longer answer: <S> Jet engines are designed with multiple compressor and turbine discs mechanically attached to a single shaft, called a spool. <S> Usually, there are 2 (or sometimes 3) of these spools within the engine, due to the need of the high pressure compressor and the main intake fan to spin at different speeds. <S> Each spool spins freely and is driven by the compressed air in the engine core being pushed through the turbine stages attached to that spool. <S> Diagram of a Turbofan Jet Engine Source: <S> Wikipedia <S> There is no way to "shut down" a particular spool. <S> As long as the pressure in the engine core is higher than the pressure behind the nozzle, the turbines will spin and drive the spool. <S> If you detach either one of the turbine stages or one of the compressor stages from a spool such that it 'freewheels,' the turbine discs will likely overspeed due to decreased load. <S> Additionally, an undriven compressor stage would experience compressor stall , which is essentially an aerodynamic stall of the blades of the compressor stage. <S> Finally, this is entirely unneeded for a couple of reasons: <S> First, aside from the problems it would cause, there would be nothing to gain from shutting down a compressor stage. <S> As Andy correctly mentioned in a comment, jet engines do not have a constant fuel burn per revolution, unlike piston engines. <S> As the pressure in the combustion chamber drops, the spools will spin down accordingly on their own (due to less pressure driving the turbine stages.) <S> Second, the power output profiles of jet aircraft operation are nothing like those of a car. <S> For a car, high engine power is usually used only in brief spurts for acceleration and cruise uses a small fraction of that amount of power. <S> In a jet airplane, on the other hand, the engines will be operated at a rather high percentage of their maximum RPMs for most of the flight. <S> This is because additional power allows them to fly higher, which actually increases efficiency. <S> See the answers to the previous question How far can a 777 fly with just one engine at altitude? <S> Unlike a car, significantly reducing the power during cruise flight actually reduces the fuel efficiency of an airliner. <A> If you extend the idea of "switch off" a bit, this is already done in several different ways. <S> Surveillance aircraft may be designed to loiter over their target area with some engines shut down completely. <S> That is not just a matter of shutting down the engines - for example if you are going to loiter at high altitude for several hours at temperatures below -50C, you are likely to need special systems to heat the oil in the shut-down engines, to avoid damage when you restart them. <S> Many jet engines contain variable stator vanes in the compressors, which are automatically adjusted to improve the efficiency under different working conditions. <S> In multi-shaft engines, the relative speeds of the different shafts changes depending on the working conditions. <S> That is more efficient that forcing all the compressor and turbine stages to run at the same speed on a single shaft. <S> In a multi-shaft turbofan, the bypass ratio (i.e. the fraction of the air being compressed in the core engine and used for combustion, rather than just being blown by the fan to generate thrust) will also change. <A> Fuel efficiency is not improved by shutting off stages of a compressor or turbine. <S> Fuel efficiency is a function of overall pressure ratio, reduce this and efficiency is reduced.
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If a jet engine doesn't need to produce as much power, it can simply inject less fuel in the combustion chamber. You cannot "switch off" a stage of a turbine engine.
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Why have different pattern altitudes for different aircraft? In the FAA AFD for Santa Rosa airport (KSTS), the pattern altitude is given as 1,000’ AGL for small aircraft, and 1,500’ AGL for large aircraft. Why do these altitudes differ? Doesn’t it compromise having a uniform pattern altitude so aircraft can see each other? <Q> Several possible reasons. <S> Speed differences between aircraft classes. <S> Larger jets cruise and land at much faster speeds than single-engine props. <S> Keeping their pattern separate from slower traffic minimizes problems posed by a faster plane entering the pattern behind a slower one. <S> Noise abatement. <S> A jet, even a smaller private one at near-idle in approach, is loud. <S> Keeping them higher increases the distance and number of thermal strata to shield nearby residents from traffic noise. <S> Prevailing instrument conditions and relative pilot experience levels. <S> A ceiling below 1000 feet, the small craft pattern altitude, would ground VFR flights and thus drastically reduce the number of small craft in the first place. <S> Jets, turboprops and other larger planes are much more likely to be IFR-capable (plane and pilot) and so they're placed higher because they can deal with clouds in the pattern (the airport, if towered, would likely alter pattern height to clear cloud layers but traffic <S> holding above the clouds would still require an IFR approach). <A> Larger aircraft generally are faster and fly wider patterns than small planes. <S> It would be much more difficult to sequence different types of aircraft at the same altitude while maintaining separation. <A> Additionally to KeithS' answer, you also have some airfields in e.g. Germany, where a different pattern exists for glider aircraft, ultra-lights and regular single or multi engine pistons. <S> The consideration here is not only speed, but also the ability to maintain level flight. <S> Glider patterns in almost all cases will be very close to the airfields with little impact on surrounding housing areas, as gliders generally create less noise than powered aircraft. <S> They also need to remain closer to the airfield in the pattern, as they can only trade speed vs altitude, but not gain altitude or maintain it as power aircraft. <S> Powered aircraft can follow a pattern that will be suitable for noise abatement and other requirements, such as obstacle clearance or avoiding certain areas for other reasons. <S> The same consideration that apply above between gliders and powered aircraft do apply between slow powered aircraft and fast powered aircraft, as already explained in the other answer. <A> At many of the airports I've flown in (as a helicopter pilot), they will also have rotorcraft fly in the opposite direction from fixed wing. <S> Our descent profile and cruising speeds are different than aircraft, and given that we may do confusing things like slow down into a hover, its for the best. <S> Generally they'll place us at a different altitude as well. <S> The planes can be spaced a bit closer together if large planes aren't comingled with the smaller aircraft. <S> Similar setups will also happen in commonly used airways. <S> For example, where I live in Chicago, and when flying westward through Midway/O-Hare airspace (they overlap), they'll generally have us fly along the highway. <S> They tend to put the rotorcraft at a much lower altitude than the fixed wing, which I suspect is not only for the same reasons as above, but also because the altitude minimums for rotorcraft are lower than for fixed wing, and it gets more traffic out of the way.
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As other people mentioned, the fact that larger planes travel at different speeds is one reason they may place them in a different pattern, and I suspect it helps with wake turbulence as well.
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How is rudder used in a aileron roll? Rudder is usually used to maintain coordinated flight. When banking to one side to begin a turn, the rudder is usually pushed towards that side. I guess this is still valid in inverted flight: in normal flight, if the pilot bank the plane to the right, it also push the right pedal (to conteract adverse yaw); in inverted flight, if the pilot bank to the right, the plane will turn to the right seen from the ground, i.e. the left seen from the pilot. The pilot should apply left rudder to keep coordinated flight. If the pilot want to make a aileron roll, what will be the general action on rudder given the flight goes quickly from normal to inverted and back to normal, and the pilot don't want to initiate a turn? <Q> The key in flying a good roll is to keep the aircraft's nose up in anticipation of the lift requirement when flying in knife-edge or inverted flight. <S> Since in knife-edge the elevator and rudder will assume each others function, you will need rudder as well as elevator for directional and pitch control. <S> Also, depending on adverse yaw, some rudder is required to hold yaw to zero when applying ailerons. <S> The procedure is as follows: <S> Speed up, so you are fast enough for roll maneuvering and inverted flight. <S> Pitch up a few degrees. <S> How much depends on wing incidence and zero-lift angle of attack. <S> Look out for some feature on the horizon: This will help you to keep your direction constant. <S> Stop the pitching motion, then apply full ailerons. <S> Correct the aileron-induced yawing motion by applying gentle rudder (trailing edge in the direction of the up-going aileron). <S> Your goal is to keep the fuselage pointing at the chosen feature throughout the maneuver. <S> With increasing roll angle, apply rudder to keep the nose up. <S> At the same time, push the stick gently to avoid course deviation. <S> At 90° roll angle, both elevator and rudder have changed their function: The elevator will now control direction, and the rudder will control pitch. <S> Keep the rotation rate and push the stick more when changing from 90° to 180° roll angle. <S> In inverted flight you need to keep the aircraft trimmed, and depending on the static stability and speed this can require considerable negative elevator deflections. <S> At the same time reduce rudder deflection such that the fuselage will still point into the initial direction. <S> At 180° roll angle both elevator and rudder have returned to their old function, but pulling will now start a dive. <S> On the way to 270° you will again need to add some rudder, now in the opposite direction, to keep the nose up. <S> Again, elevator and rudder will exchange their functions. <S> Once you return back to normal flight attitude, stop the rolling motion and reduce rudder deflection back to zero. <A> Well first, by barrel roll do you mean a true barrel roll which is a combination loop and roll, or do you mean a tighter maneuver like an aileron roll or slow roll accomplished mainly with ailerons <S> but which can still result in a rotation around a point above the plane? <S> The answer in all three cases is that rudder is used to help maintain stability in the roll. <S> Counter-rudder (applying rudder opposite to a bank) can also help to start a "wide" roll by kicking the plane into an initial yaw that counters the tendency of the plane to turn into the initial bank. <S> Finally, first a hard left yaw and then a hard right yaw is used to execute a "true" barrel roll where the plane rolls in a circle roughly perpendicular to its original path. <A> As an aerobatic pilot, it's pretty simple. <S> The aircraft will lose lift as you roll through 90 and 270 degrees - knife edge flight. <S> Obviously this will cause loss of normal level flight pitch. <S> So, you have to compensate for that pitch loss you start by adding the pitch you will lose (depending on speed and roll rate of the aircraft) as you start the roll. <S> How much? <S> Start by fairly quickly pitching up about 40 degrees and adjust from there each time you do a roll until you start and end at the same altitude. <S> Rudder? <S> If you roll left, slowly add right rudder topping out at 90 degrees. <S> Reduce rudder to zero at 180 degrees and push the stick gently forward to zero g's. <S> If you go negative, reduce pressure so you float gently through 180 degrees. <S> Reduce that forward pressure to neutral as you come through 270 degrees and simultaneously add left rudder. <S> At 270 degrees continue reducing left rudder to neutral as you come to level flight. <S> Once you master a left roll, just reverse rudder procedure for a right roll. <S> Be gentle with the plane as this should be done with very little stress on the airframe... <S> if it does, you are doing it wrong. <S> Learn how on a plane certified for aerobatics before you try it on the company A380. <A> There are 2 types of rolling maneuvers used in aerobatic competition, a slow roll and an aileron roll. <S> First the easy one, an aileron roll. <S> Simply raise the nose above the horizon, apply slight rudder in direction of roll initially to counter adverse yaw, stick in direction of roll. <S> You can do multiple rolls, the limitation being that you must stop once the nose has fallen about 30 degrees below the horizon. <S> A beginner can accomplish this maneuver with minimal instruction. <S> The slow roll has nothing to do with the rate of roll, a high level aerobatic plane can slow roll or aileron roll at 420 degrees per second. <S> The slow roll requires a bit of coordination in that the plane rolls about it's longitudinal axis, pitch not changing during the maneuver, as stated previously, rudder is used at 90 and 270 degrees, and forward elevator at inverted, to keep the plane at constant pitch and the nose not yawing left or right. <S> Of course no one should ever try to teach themselves aerobatics. <S> Get a good instructor and a good aerobatic plane.
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A little rudder at just the right time can help keep the nose up in a slow roll or even an aileron roll, as the plane rotates through the sideways portions of the roll when gravity is otherwise not countered.
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How does turbojet thrust change with altitude? I am studying the rate of climb of turbojets, I don't know how the thrust varies with altitude and in particular which are the differences between necessary thrust and effective thrust. Hope being clear, I can't translate properly maybe so ask and edit ! <Q> The thrust variation with altitude would be highly engine specific, but the general trend is nicely depicted in the image below: <S> Read this for further details. <A> Thrust is produced by accelerating air. <S> The exhaust air leaves the engine nozzle at a fairly fixed velocity, so the acceleration is mainly controlled by the difference between the exhaust and incoming airspeeds. <S> The faster the aircraft speed, the less acceleration is being created on the intake air. <S> Therefore thrust decreases with increasing airspeed. <S> In level flight, an aircraft could not be accelerated above the engine exhaust gas speeds because then the incoming air would be faster than the exhaust air - resulting in a decelaration. <S> Most jets are operated as max speeds much less than their exhaust gas velocity - about half of V-exhaust I think. <S> But increasing altitudes can erode thrust because the mass of air being consumed is also decreasing as the air gets increasingly more rarified. <S> To summarize: At a constant airspeed (ignoring airspeed measurement nuances) thrust decreases as air density decreases with increasing altitude; at a constant altitude, thrust decreases with increasing airspeed. <S> Note that max thrust is found when stationary, just before take-off, since that's when incoming air is at its slowest. <S> Also, at max thrust, (when airspeed is zero) there is no work being done and hence the power produced is zero right before takeoff. <A> As an aircraft increases in altitude, the density of air also decreases. <S> Thrust available = <S> Q(V1 - V2). <S> The important part of this equation is Q. Q = (rho)AV which means that the smaller rho (density ratio) becomes, the less mass airflow there is which results in lesser thrust at high altitudes.
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Since higher air-speeds are normally used at higher altitudes, thrust generally decreases with an aircraft's altitude.
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What kind of aircraft may land on iced areas, like Antarctica? I know some aircraft may land on iced surfaces. what are the difficulties associated and is this limited to specially designed aircraft. Is there some conditions necessary for the landing and the next takeoff.Where are the main iced airfields currently active? <Q> I've spent 6 summers in Antarctica (Mt. Erebus), travelling through McMurdo, where the busiest airstrips on the continent are. <S> Some of the Hercules are LC-130 -- <S> the L indicates that they have skis. <S> The skis enable them to land and take off on some including ungroomed or poorly groomed snow / ice surfaces. <S> Sometimes they need JATO for takeoff, though, if the conditions aren't great. <S> McMurdo has three runways which open and close operations during the year: Willy Field, Pegasus, and the Ice Runway. <S> The Ice Runway is on sea ice and the other two are on the Ross Ice Shelf with Pegasus built on blue ice and Willy Field on snow. <S> The Ice Runway breaks up each year during the height of the summer <S> so it is carefully monitored. <S> It bends downwards each time a C-17 lands. <S> That deformation is measured and is one of the parameters that's used to decide when to stop using the Ice Runway each year. <S> Sometimes, planes designed for non-military use are flown to McMurdo; the New Zealand Antarctic program often flies an Airbus A319 there. <S> A Boeing 757 flight to McMurdo from Christchurch had a scary incident recently where it was forced to land in low visibility because it didn't have enough fuel to "boomerang" back to New Zealand. <S> The C-17s often boomerang due to bad weather. <S> The Hercules, like the 757, don't carry enough fuel to boomerang, but they are better at landing in inclement conditions so it doesn't seem to be an issue. <S> For flights within-continent, Twin Otters and Baslers are in common use. <S> No, there's no military presence with offensive capability. <S> I don't really understand this (recently added) part of the question -- did you think they'd hit you with antiaircraft??? <S> There's a bunch of air force guys who operate the flights, and a single US Marshall in McMurdo. <A> Yes it could, same way it would preform an emergency landing any where else. <S> There are ice runways out there and its not all that uncommon to see small GA planes landing on frozen lakes in the winter. <S> There are considerations when it comes to breaking and what not <S> but in the end of the day you have the ability to always land into the wind (since you are picking your touch down heading provided there are limited obstacles). <S> Landing into the wind is also key as a result of some of the potentially high winds in the arctic and antarctic shelves. <S> The largest issue is not knowing how thick the ice is. <S> While I don't know an enormous amount about north or south pole geology the ice thickness <S> varies and in some places could not support an aircraft landing. <S> For the most part the south pole ice is very thick (9000ft) by all estimates , but the outer edges and the ice that does not reside above the landmass could be thinner. <S> Keep in mind that parts of the arctic/antarctic are in total dark for a part of the year so you may be looking at nigh procedures when landing. <S> Interestingly enough, Antarctica actually has 20 airports <S> so you may even be able to put down on a strip depending on where you are. <A> Any plane with tires. <S> When the ice is plowed it scratches it up and that provides enough of a friction that landings are fairly normal, like landing on concrete. <S> There are ice runways in Greenland that are used regularly. <A> And even, a Hercules can land on ice: Source . <S> They where built for landing on ice may sound crazy but they are built for land on all kinds of surfaces
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As far as I know, a well-groomed snow / ice runway can accommodate any plane in good weather. Most flights to McMurdo are on C-17s or C-130 Hercules.
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Why does aviation use Zulu time instead of the local time? When reading aviation literature, it's common to find references to Zulu Time . What is Zulu Time ? Why does aviation use Zulu Time instead of the local time? <Q> Zulu means the letter Z in radio communication. <S> The letter Z designates UTC time. <S> There is actually a list of time zones for each letter of the alphabet (except J ): <S> Alpha time zone: <S> UTC + 1 Bravo time zone: <S> UTC + 2 ... <S> India time zone: <S> UTC + 9 Kilo time zone: <S> UTC + 10 Lima time zone: <S> UTC + 11 Mike time zone: <S> UTC + 12 November time zone: UTC - 1 ... <S> X-ray time zone: UTC - 11 Yankee time zone: UTC - 12 Zulu time zone: <S> UTC + 0 <S> However, the other time zones are seldom referenced in aviation. <S> Why do we use UTC time instead of local time? <S> Because flights often cross time zones. <S> Imagine this: the time now is 11:59. <S> We will takeoff at 12:30 and fly west. <S> Afterwards, at around 11:48, we will be 15 nautical miles away from the airport..................... <S> Huh? <S> Even more confusing <S> : We takeoff at 12:30 and land at 13:00 == <S> > <S> we only need 30 minutes of fuel. <S> Wrong! <S> We actually cross a time zone and the actual flight time is 90 minutes. <S> But we've taken off with 60 minutes less fuel than we need. <S> What do we do? <A> Zulu time, as others have pointed out, refers to UTC. <S> We use this time in aviation (and meteorology and surely others) because it is easier and it is standard. <S> It's the same time everywhere on earth. <S> If you are flying along the border between Arizona and New Mexico in the summer and given a hold: <S> Cessna 1234 hold at FIX, right turns, 10 mile legs, expect further clearance at 1630, time now 1602 <S> If that were local time, you'd have to now determine if that fix is over AZ or NM, because NM observes daylight saving time and is in MDT/-0600 and AZ does not observe daylight saving time and is in MST/-0700. <S> This is a needless check that is distracting and can cause confusion all due to using a local time. <S> Instead, we know the times given are Z/UTC time and "1630" has an unambiguous meaning no matter where on earth our plane is located. <S> It is a similar situation when checking pre-flight weather. <S> Weather is reported in Z time and this makes it easy to calculate when you will get to your destination and what forecast is valid for that time. <S> If it were in local time you'd have to know additional information about time zones, which again could be a source of error and is needless. <S> Adding to potential confusion are regions of earth that keep odd adjustments. <S> For example, St. Johns, NL, Canada is GMT-0330 in the winter and GMT-0230 in the summer. <S> There are even a few that are off by 15 minute adjustments (e.g. Nepal). <S> Combine this with knowing where DST is observed and where it isn't, and more importantly when it is (USA DST has different start/end dates than other places) then it becomes very complicated to work in local time. <S> Working in universal time solves these problems. <A> The reason for the name zulu is because there is a hour shift of Zero sometimes denoted with a Z and <S> in the nato alphabet Z is Zulu. <S> Many times a route will cross timezone so to avoid confusion about which timezone a time is in controllers and pilots will use zulu time by default. <S> It also avoids daylight savings issues. <A> Zulu time, used in aviation quite often, is another name for UTC (Coordinated Universal Time (French: <S> temps universel coordonné)). <S> It is the primary time standard by which the world regulates clocks and time. <S> It is, within about 1 second, mean solar time at 0° longitude; it does not observe daylight saving time. <S> It is one of several closely related successors to Greenwich Mean Time (GMT). <S> For most purposes, UTC is considered interchangeable with GMT, but GMT is no longer precisely defined by the scientific community. <S> Edit <S> To answer the second part of your question : Its called Zulu time as UTC does not have daylight savings, hence Zero hour shift. <S> Now Zero starts with Z and NATO call-sign for Z is Zulu. <S> Hence the name. <S> Source <A> Zulu time, sometimes called Greenwich Time or UTC time, is the local time at the Prime Meridian, that is on the 0° Line of Longitude, which also happens to run through Greenwich, England. <S> This local time has been adopted as International Standard Time and used as the official time on Earth. <S> Other local times are utilized by local principalities or nations as a relative standard time for that area of the Earth. <S> It is offset a certain number of hours from Zulu time.
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As aircraft may be operating over several time zones during a cross country or international flight, it makes sense to file flight plans with departure and arrival times listed in Zulu time for easy reference. Zulu time is UTC time .
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Why are pilots asked to provide a reason for a go-around? Why does the tower ask pilots what the reason is for a go-around? This seems to be standard for commercial flights. <Q> The reason 1 pilot goes around may also be the reason the next pilot goes around, The second pilot would like to know before hand whether the runway is safe to land on. <S> For example if it is wind related he can delay landing until it dies down. <S> If it is debris related then the tower can dispatch a cleaning crew. <A> Pilots are not required to give a reason for a go-around, just to say that they are going around. <S> A go-around is a busy time for the pilot(s) of the aircraft - power, flaps, trim, must be set, gear raised in some cases. <S> The pilot needs to aviate first. <S> The tower wants to know why the go-around was initiated by the pilot as it may be relevant for safety and/or operations. <S> If the pilot is going around because of a botched approach then that won't impact other flights, however if there is a problem with the aircraft the tower can organize emergency resources. <S> If the go-around is due to a situation on the ground then the tower can look to clear that up. <A> When the pilot does that, they follow the 5 Ups memory aid ( Power Up, Nose Up, Gear Up, Flaps Up, Speak Up ). <S> You can see that by the time a pilot is ready to inform ATC about go-around, he is already going around. <S> Commonly, when ATC requests a go-around, it is if there is an unsafe condition such as an aircraft, vehicle, or object on the runway. <S> When the pilot decides to go-around, it can be one of the following reasons : <S> the aircraft is not lined up it is not configured properly for a safe landing an aircraft, vehicle or other object has not cleared the runway <S> no landing clearance was received (at a towered field) <S> the landing gear is not properly extended a dangerous meteorological condition is experienced on final approach (e.g., poor visibility, excessive cross-winds, windshear, etc.) <S> excessive energy (too high or too fast) or any other unsafe condition is detected <A> Short answer: because first you're disrupting the traffic pattern (especially at larger airports that don't use a circular pattern and coordinate direct approaches instead) and the tower will want an explanation, and second because if there is a problem outside the cockpit causing you to execute the missed approach, other craft might have the same problem, and if the tower knows about it they can take steps to resolve it, or at least advise other incoming craft. <A> I've only got about 300 hours logged <S> but I have not once been asked WHY I am going around. <S> However if you "intend" to do a touch-and-go or an abort/go around you must inform them, because it's their job to know where every aircraft is going. <S> I usually tell the tower before takeoff I'll be flying a "closed pattern" if just practicing TnGs. <S> Makes it much easier for ATC. <S> When I intend to stop, I will say landing "Full Stop" when turning final. <S> But, as Farhan said, if anything is off on approach or you bounce on touchdown, miss the touchdown zone <S> , wind starts kicking your ass or if ANYTHING isn't perfect, it's full throttle, flaps up once <S> +ROC, and figure out what u did wrong. <S> The tower can wait, they are all in there watching, laughing at your pathetic attempt anyway. <S> If something is wrong, do insist on priority access! <S> POC is in charge after all. <S> My alternator 172SP died on climbout once <S> and I didn't say a thing, just rushed to mid field and dove vertical out of downwind pattern, slipping the hell out of it to slow her down. <S> Per protocol, I didn't say a word to ATC until I was clear of the runway. <S> But always be nice to the ATC. <S> Fantastic guys that would do ANYTHING to keep their pilots safe. <S> The FAA/NTSB tho.... they are the best reason to keep your mouth shut unless you are out of options!
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The only reason for a go-around is that the pilot or ATC thinks that landing is not safe or possible for this approach.
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How do I locate a list of restrictions that would prevent a pilot from flying in the US? I have a privacy preserving technology that could conceivably help prevent the Germanwings crash of 2014 . The idea would be there is a long list of issues that would prohibit a pilot from flying encoded on a ID card that anonymizes a pilot's information: I'm guessing that a list might look like this: Overwork (no sleep) Simulator experience, test results Medical issues (temporary) Drug tests Psychological issues A list of medical providers would link the results together, anonymously, and during the pre-flight check, the ID card would be scanned and rather than a specific issue being highlighted, (depression), the pilot would be asked to rest for a while. No system would know why the rejection occurred, except for the pilot himself. This might for a balance of privacy, safety, and accountability without compromising need to know. That being said, I would appreciate any official, or carrier specific list of reasons a pilot would be rejected from flying. The closest I've gotten to learning about this is MSFT Flight Simulator and a few hours in a Cessna Supplemental information would be helpful as well (your thoughts about this solution) Scope Per the comments below this question, the scope is limited to US <Q> The list is exactly one item long: Any condition which would impair your ability to conduct the flight safely, and in accordance with FAA Regulations. <S> Any more specific list will miss things and be riddled with loopholes - at some point we have to trust that pilots are sane and responsible individuals, just like we do when we let people get in a car. <S> From a medical perspective the general medical certification information page at faa.gov is a good starting point, and the FAA's guidance for Aviation Medical Examiners has lots of details. <S> There are also some disqualifying conditions which are explicitly listed in the regulations , and a list of (some of the) medications which will prevent the FAA from issuing a medical certificate . <S> The things I noted above will prevent you from getting a medical certificate. <S> Once you HAVE that certificate the "I'M SAFE" checklist or something equivalent expands upon that and tries to help pilots determine whether they're fit to fly right at this moment . <S> There are various ways of interpreting the acronym, but a common one is: I for Illness <S> Do <S> I have an illness or any symptoms of an illness? <S> M for Medication <S> Have I been taking prescription or over-the-counter drugs? <S> If so, do they have a negative affect on my ability to perform this flight? <S> Are any of them disallowed by the FAA? <S> S for Stress Am I under psychological pressure from the job or personal issues? <S> A for Alcohol <S> Have I been drinking within eight hours? <S> Within 24 hours? <S> F for <S> Fatigue Am <S> I tired and not adequately rested? <S> E for Eating Am <S> I adequately nourished, or at least "not hungry"? <A> There are four very general reasons - really, categories of reasons - that I can think of to ground a pilot (or for a pilot to ground himself): <S> It would be illegal to fly for obvious procedural reasons, e.g. your license has expired, you've exceeded legal limits on flying hours <S> You shouldn't fly for non-obvious reasons that are known only to yourself, e.g. you're suffering from stress or grief, or have an undisclosed medical condition <S> But the thing is, airlines already track as much of this information as possible anyway. <S> If they didn't track them, they couldn't schedule pilots on flights efficiently and they have to make sure that every pilot is up to date with medicals, licenses etc. <S> to avoid scheduling problems and lost revenue. <S> So the only real issue is when a pilot knows he should ground himself but chooses not to. <S> There's no solution to that except to encourage pilots to identify those situations properly, and to have laws and policies that don't penalize pilots who self-ground for good reasons. <S> Even if Germany - or any other country - starts allowing doctors to share private medical data with aviation regulators and airlines, it won't prevent cases where pilots deliberately conceal medical issues. <S> And you also have to consider that airlines would quickly become very unhappy with any system that says "this pilot can't fly today <S> but we can't tell you why <S> and we can't tell you when he will be able to fly again". <S> So - at least in my opinion - your proposal mostly reproduces what airlines are already doing, and creates an additional problem of unpredictable staffing. <S> Considering how rare accidents are, it's doubtful if any 'solution' is actually necessary, although I do think it's great that someone is thinking about how to balance privacy with safety. <A> The linked resource for each broad category explains the particulars. <S> Health Conditions That May Affect Certification <S> In this section, find answers to questions about how a medicalcondition might impact your flying privileges. <S> Information iscategorized by physiology and includes the relevant medical standards,as well as the procedures to follow for recertification, or to obtaina special issuance medical certificate. <S> Bone and Joint —Includes information on arthritis and musculoskeletalconditions. <S> Cancer —Many pilots recover from cancer and regain flying privileges. <S> Find out more here. <S> Ear, Nose, Throat, and Equilibrium —Read the medical standards forhearing, as well as information on cochlear implants, Eustachianbypass, and motion sickness. <S> Endocrine System —Includes information on diabetes and thyroidconditions. <S> Gastrointestinal —GERD, hepatitis, colitis, Crohn’s disease and moreare covered here. <S> Heart and Circulatory System <S> —Read how to get recertified after havingheart-related problems. <S> Mental Health <S> —This section covers ADD/ADHD, depression, psychologicalevaluation, and substance abuse. <S> Neurological (Nervous System) <S> —Read about migraine headaches,cerebrovascular disease, and strokes. <S> Pulmonary <S> —Read how you can keep your medical certification if you haveasthma, allergies, or another lung-related condition. <S> Sleep Disorders —Find out what you’ll need to do to get your medicalrenewed if you have sleep apnea. <S> Substance Abuse —Here are the guidelines for certification if you havea history of alcohol or drug-related problems. <S> Urology (includes kidney <S> ) —Read how to be recertified after havingkidney stones removed, or after a successful kidney transplant. <S> Vision —Color vision, glaucoma, and LASIK surgery are all covered here.
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It would be illegal to fly for obvious medical reasons, e.g. you're taking a medication that the FAA doesn't allow You're legal to fly, but your employer's policies don't allow you to fly, e.g. you haven't had some specific internal sign-off required for a certain aircraft, route or crew combination Immune System —HIV and related conditions are included in this section. AOPA has a comprehensive list that answers your question from the medical perspective.
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Why aren't airliner windows aligned with their seats? On a recent airline flight, I noticed that the spacing of the plane's windows was different from that of the passenger seats: some of the rows had a window directly in line with them but for others, the windows were partially obscured by the seatbacks in front or behind. Is there a reason that the windows aren't manufactured with a regular spacing to align with the seat rows? Does it have to do with the fact that different airlines may be using different seating configurations for the same model of aircraft? <Q> Because the pitch of the frames is not related to the pitch of the seats. <S> The windows placement have to cut through as few frames as possible. <S> You can see it in the following picture, noting that frames are "highlighted" by the vertical riveting Image source <S> It is even more evident in the picture contained in this answer on <S> UX.SE: <S> Because the aircraft is designed once, but "decorated" by several airlines in several different manners. <S> For example, an A320 or a B757 will have the windows always in the same locations, but depending on the airline that is using it, it will most probably have the seats in slightly different locations. <A> Because airliners skimp on spacing and steal your leg room to squeeze in another row of seats. <S> So why not design the plane with the eventual seat spacing in mind? <S> Airliners can decide their own spacing so there would always be planes where they won't match up. <S> Also there has to be a certain amount of hull to keep the strength needed for the fuselage to work as it needs to. <S> So the designers need to make a compromise on number of seats and strength of the hull. <A> An aircraft is delivered in a very basic configuration; no seats, and windows running the entire length of the aircraft. <S> The airline is then tasked with choosing and installing their specific makes of not only seats, but also galleys and sometimes lavatories. <S> All of these must fit into that initial basic aircraft, meaning that this layout may not perfectly fit into the "mold" of the original aircraft. <S> This means that there could be some misalignments because the seats could be of different spacing or size than the windows were originally designed for. <A> When an aircraft is designed, the hull is designed in terms of 'frames' which actually support the main hull of the fuselage. <S> Some air-crafts have provision to include more frames (upto some limit) to increase the length of the plane if later modifications are required. <S> Now, the windows are placed in a regular spacing depending upon the length of each frame on the hull (so basically windows are spaced to remain in between the frames), and this pattern is determined after loads simulation on the aircraft's hull. <S> Once designed, the insides of the airplane can be modified at will (as this does not determine the 'safety' of the aircraft much), and this is when airliners try to persuade the manufacturer to put seats in a fashion that they can get the desired revenue. <S> This independence in the hull frame spacing and the seat spacing is why the windows are not aligned with the seats. <A> The seats are attached to rails underneath the floor which run along the aircraft fuselage. <S> They can be spaced any way the airline prefers, and this position does not have anything common with the window positioning. <S> You can buy the aircraft seat rails here , and also see how they look like.
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This system of configuration is better for both the aircraft manufacturer (because it is cheaper to build one basic airframe as opposed to hundreds of slightly tweaked ones) and the airline (because they are able to customize the interior to their liking).
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What are the factors behind increasing aircraft window sizes? Modern airliners like the Airbus A380 and Boeing 787 have bigger windows than older designs, like the Boeing 737 and Airbus A320. What factors have led to this change of window size, opposite to the trend of almost every other thing in the interior of the plane becoming smaller in size (like the seats). <Q> In the early years of the jet age, which followed closely on the introduction of pressurized hulls , there was much fear of stresses specifically in the area of the window openings due to the loss of two DeHavilland Comets . <S> Subsequent Comet hulls had different shaped, rounded, smaller windows and <S> that trend continued in other pressurized, typically jet-powered, aircraft. <S> Only with modern CAD systems and new materials knowledge could windows be made larger again. <S> The newest aircraft designs reflect that progress. <A> I think engineering knowledge is an important factor, going from the time of the first 737 to the A380, there was a huge development in engineering techniques. <S> Better material knowledge, more advanced modeling methods (such as Finite Elements) and better knowledge of structural optimization have improved the situation. <S> Especially with windows, where a lot is happening due to stress concentrations, this improved knowledge makes a difference. <S> This means that bigger windows might still lead to an increase in weight, but there will be a less severe weight penalty than the same windows using B737 age techniques. <A> Metals are a crystalline structure that over time tend to fracture along crystal structure defects. <S> Some key areas (e.g. turbine blades in the engine) are actually created by growing a single crystal to obtain higher failure points. <S> This is not possible over a structure the size of the aircraft frame. <S> When an aircraft is at altitude, it is like a pressurised balloon. <S> its skin is under tension, and when it on the ground, that tension is removed. <S> This is like constantly flexing a metal paper clip. <S> The cross sectional area of the aircraft skin that carries this tension is reduced by windows - bigger windows put bigger strain on the airframe structure which tends to concentrate at corners. <S> making corners rounded helps to spread this stress. <S> The composite materials used in new planes are fibrous in structure. <S> This greatly reduces the risks from the repeated flexing, allowing larger windows (and as the rust risk is reduced, cabin air is allowed to be more moist with also aids in flight comfort of passengers) <A> Let me answer with a car analogy: In most cases, the next car model is larger than the one before. <S> Similarly, the aircraft manufacturers make the windows a little bigger with every new model, just to have another argument why the new model is better than all the competition. <S> This costs a little weight, but seems to be worth it for the airlines. <A> One of the important things I'd like to add to the previous answers is that the old air-crafts used to have smaller windows to accommodate for the rate of cabin depressurization in case of an emergency. <S> The old airplanes had much smaller windows to control the cabin depressurization rate in case of some emergency (some window actually breaking to cause hull breach). <S> But with advancement in the design methods and manufacturing process and with the introduction of the newer materials for airplane manufacturing, it has become possible to increase the size of the windows without increasing the risk factor. <S> In addition to this, creating an ambient atmosphere for the passengers inside the airplane without increasing the cost of the flight has always been a priority. <S> So, while decreasing the seat spacing to accommodate more passengers is being done to reduce flight cost, the increase in the size of the windows does not have determinal effect on the travel cost, and hence is favored to create a less claustrophobic atmosphere inside the plane. <A> As well as the advances in engineering, it is worth considering the comfort of the passengers. <S> It is often thought that the more natural light in the cabin the better the experience for the passengers. <S> More light increases the feeling of space, and can even reduce the fatigue experienced as a result of air travel. <S> Whether or not there is much science in this I do not know. <S> Some Aircraft manufacturers use the window sizes as a big selling point. <S> Gulfstream aircraft, for example, allow in more light than any comparable aircraft due to their oval shaped windows. <S> In an attempt to compete Dassault are putting more windows on their newer Falcon 8x and Falcon 5x models. <S> Both companies have also introduced windows in the galleys in some models (Dassault famously with the 'sky light') <S> as this is typically the darkest and narrowest part of the cabin. <S> In the cabin configurations most typical in Europe, the galley is at the very front of the cabin and is the first thing you see when you enter the aircraft. <S> I think it is safe to say that it is much nicer to walk into a bright, airy space than a dark, narrow corridor. <S> Gulfstream 650 window details: <S> Sixteen large Gulfstream panoramic windows, each 28 by 20.5 inches/71by 52 centimeters, allow abundant sunlight into the cabin, even in thegalley. <S> Every window has been repositioned higher on the fuselage tomaximize viewing comfort* http://www.gulfstream.com/aircraft/gulfstream-g650 Falcon 5X window & 'skylight' details: <S> Increased natural light does more than improve the view. <S> It elevatesyour mood and enlarges your perspective. <S> The 28 large, expansivewindows of the 5X provide unbeatable luminosity. <S> The Falcon 5X offers an unprecedented direct view of the sky overheadthrough its skylight ceiling window. <S> This unique window on the skytransforms your perception of space while providing natural light fromabove. <S> http://www.dassaultfalcon.com/en/Aircraft/Models/5X/Pages/overview.aspx
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It is the use of composite materials in the aircraft body structure that has enabled larger windows.
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What is the effect of opening airplane bay doors on the radar cross section of the airplane? How does opening airplane bay doors (especially in the case of bombers), increase the radar cross section of the airplane and make it more visible to the radar? These are usually combined with active measures such as carefully planning all mission maneuvers in order to minimize the aircraft's radar cross section, since common actions such as hard turns or opening bomb bay doors can more than double an otherwise stealthy aircraft's radar return Source <Q> Radar waves are sent back to the radar by two mechanisms, reflection and diffraction. <S> Opening a bay door may present a surface that is angled such that waves will be reflected to the radar. <S> As for diffraction, low observable (stealth) aircraft are designed so that a radar wave encountering the aircraft's skin will travel along the skin and be gradually absorbed. <S> Opening the bay doors creates a break in the skin, causing waves on the skin to diffract. <S> Some of the radar energy is returned to the sender. <S> For an amateur looking at "stealth" diffraction is often not accounted for. <A> In addition to creating a surface that could better reflect radar and breaks that can diffract the radar, the interior of the bomb bay is exposed. <S> The exterior skin of stealth aircraft is specially treated to reduce radar returns, so the untreated interior of the weapons bay and bay doors will also create a much larger radar return than even the exterior surfaces of the open doors. <A> The radar cross section (RCS) of an object does not depend on its size, but on the number and orientation of its edges. <S> Depending on the direction at which the radar is looking at the aircraft and the RCS of the plane with closed doors, the difference is between zero in the direction of the main reflection lobes and several orders of magnitude in the new edge direction, namely sideways.
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Opening weapon bays will break up what was a single surface before into several, and the need to align the doors with airflow will create a new edge orientation which will result in a new reflection spike where none was before.
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Is there some functionality of an airliner which is not controlled by the cockpit? We have had a blockbuster question , asking about the complexity of the cockpit, which was answered very well. With so many controls, are there any flight- or safety-critical functions which cannot be controlled by the cockpit? <Q> You cannot (as far as I know), Flush the toilets Control the IFE system (aside from possibly pulling the breaker to shut it off)(there seems to be some debate on this one and it could vary by plane/system) <S> Open the doors (of a passenger plane, cargo planes this may be possible) <S> Update the software for glass cockpit planes (if the computers are not located in the cockpit). <S> I'm still looking for the link but FMS units are updated via USB on a unit usually housed with the other flight computers which is often below the cockpit. <S> In some smaller planes these units are in the cockpit as are the USB ports so this may only hold for some aircraft. <S> General passenger tasks (reading lights etc). <S> Although it should be noted that generally speaking the master breakers are in the cockpit so while they may not have control over individual system components (e.g. single reading lights) they can often shut them down completely if need be. <S> Ovens (for heating meals) and coffee machines. <S> Only circuit breakers are in cockpit again (and they are needed; faults in these things cause relatively high fraction of diversions). <A> There may be signals indicating the state of the doors (and their locks), but the doors themselves are opened or open-able manually. <A> I am certain pilots cannot control galley carts position especially in turbulence. <S> These units are manually controlled by flight attedants and maybe out of control in rough weather if not properly secured. <A> And excluded from "tools" category, but still uncontrollable are babies. :)
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The doors (through which the passengers board or disembark) are not in control of the cockpit, in an airliner. In addition to many other things listed in answers, the biggest thing that pilots can't control from cockpit are "tools" like drunk passengers, cell-phone during flight users, loud passenger groups.
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Could you ever legally authorize yourself to fly an aircraft that would require an LOA, based on your other certs? The question about being certified to fly aircraft that don't fall under a type rating got me thinking. For all knowledge possessed by humans there must be a source. If you want to get certified on a Bombardier CRJ narrow-body, you have to be trained by someone who has not only also been rated to fly it, but certified to train on it. This process is inherently iterative; someone trained your trainer, and someone else trained your trainer's trainer, and so on until at least a time when there were no aircraft of that specific model. At some point, someone got their approval to fly and teach that model without a single hour of stick time in that specific model of aircraft, because it simply didn't exist. For aircraft like a Bombardier, the alternate training avenues are obvious; the manufacturer, located in a staunch U.S.-allied nation, will produce training materials and at least fixed cockpit sims, which when coupled with flight time in some other narrow-body T-tail jet, will serve as the basis for certification to fly and ultimately train others on any new Bombardier model. However, this gets tricky when you consider models of aircraft not falling into FAA-defined types, especially single-seaters, and definitely the first one or two of these aircraft to enter civilian hands. Vintage ex-mil planes, especially from non-Allied countries, are the primary example; how did the first civilian Zero owner get certified to fly it? One possibility I thought of for how this could come about is based on the fact that there are a number of pilots/instructors with an extraordinary number of ratings. The current record, IIRC, is over 100 type ratings and/or specific aircraft model certifications. At some point, more training for a pilot like this on any specific airframe becomes redundant; there's nothing the pilot can learn from a CFI that a combination of the pilot's own experience on comparable models and whatever training materials exist for the airframe could provide. A pilot like this would be an obvious choice to take the first flight in some new plane, unique in the U.S. civvie world, but technically he'd still need authorization to do so. So the question is, is there ever a "tipping point" where a pilot can legally use some combination of his existing qualifications to assert by himself that he has the required knowledge and skill to fly a first-of-its-model plane, for which he does not have an LOA and could not get one through normal channels? One possible example. Say it's 1992. The Soviet Union has just broken up and the Red Army's military hardware is being auctioned off to the highest bidder. A collector and flight enthusiast in the U.S., who already owns and flies some ex-mil jets like the F-86 Sabre, heads overseas and buys himself an old MiG-17 from the USSR reserve forces in flyable condition; the first one ever to be in private American hands. Now, how does he get certified to fly it within FAA-controlled airspace? Does he have to find a former Soviet pilot who can train him, and somehow transfer that Soviet pilot's voucher into an FAA LOA? Is there some high level of instructor certification that allows a CFI to train on airframes the CFI himself is seeing for the first time? Or, can the collector himself, given his existing LOAs for closely comparable aircraft including his own Sabre, assert that he is capable of flying the MiG-17 and do so without anyone else having to vouch for that ability? The only thing I can think of besides the pilot just saying "someone's gotta be the first to learn to fly this thing, and it might as well be me", is for the FAA to say exactly the same thing, and directly issue some sort of special provisional authorization for the collector to learn the aircraft for himself, hands-on, no CFI. This authorization would naturally contain all sorts of restrictions on when/where he could fly it (if I were the FAA watching someone learn to fly a military jet, I'd point him to the nearest MOA), until he could somehow demonstrate to someone that he'd attained mastery of the airframe and have most or all of the restrictions lifted with an LOA. The specifics of how all this would happen, though, escape me. <Q> The original question which you linked to contains a link to the FAA Inspectors Handbook, which covers this scenario as well: 5-1590 TEMPORARY LETTERS OF AUTHORIZATION. <S> A. <S> Temporary LOAs may only be issued for a specific purpose and should be for a specified, limited duration. <S> ASIs who receive requests for temporary LOAs for operating experimental aircraft must coordinate with the NPO before issuing them. <S> These LOAs may be required to ensure compliance with the aircraft operating limitations. <S> B. Temporary LOAs for the operation of experimental aircraft should not be confused with temporary LOAs for the operation of TC’d aircraft. <S> Section 61.31(b) permits operating TC’d aircraft under limited circumstances. <S> These LOAs are issued in accordance with the guidance in Volume 5, Chapter 9, Section 3. <A> The answer to this, at least for planes that sport big, whirly props, lies next door to the FSIMS, in FAA Order 8900.2 , the "General Aviation Airman Designee Handbook". <S> Specifically, you'd contact your local CAF wing or the EAA Warbirds division, who'd then put you in touch with an appropriately qualified National Designated Pilot Examiner (NDPE) via the National Designated Pilot Examiner Registry, or NDPER -- between them, you can get checked out on any reciprocating aircraft, even a Zero, a Bf-109, an Il-2, or a Mosquito. <S> Non-type-certificated turbojet aircraft follow the 8900.1 checkout procedures -- a temporary LOA would be issued as Lnafziger pointed out, usually with an EPE (Experimental Pilot Examiner) or NDPE (yes, some of the NDPEs can check you out in jets too) giving you the final "checkride", based on their qualification in similar types of aircraft (for instance, if you hauled a Su-30MK home from the Sukhoi factory, you'd probably have an ex-F-15 pilot or the likes checking you out on the type). <S> Of course, if it's a UFO (aka something that is not of any extant category or class), then AFS-800 would probably have to step in and send or designate someone. <A> Mark Clark, the owner of Courtesy Aircraft , has the following pilot certificate, which allows him to fly anything.
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For one‑of‑a kind aircraft, first‑of‑a‑type aircraft, amateur‑built aircraft, practice in a single‑place aircraft, or other special cases, a temporary LOA may be issued.
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What are the hurdles to overcome before purely electric commercial aircraft can fly? What are currently the largest issues with purely electric commercial aircraft (large scale ones like the size of a Boeing 737)? Are there any organizations right now that are trying to solve those issues? <Q> The biggest problem with an all-electric-powered aircraft is the same as those plaguing all-electric cars; our current battery technology has nothing on the energy density of fossil fuels: <S> There's just no contest in being able to pack the energy needed to push a plane through the air into a volume and weight compatible with an airliner. <S> Jet fuel is kerosene, which is pretty much right in between gasoline and diesel, while any battery technology we've developed can't even be accurately plotted on the scale of this graph. <A> In addition to the energy density issue as mentioned there is a turn around time issue. <S> The fact is that batteries just don't charge up that fast and any system that allows them to do so is often dangerous to be around. <S> So if you are talking about an airliner (lets say we overcame the weight of the battery issues) it takes about 15-30 minutes to fuel up a 747 <S> , there is no way you are going to charge any kind of batter that we currently have today to the same energy potential capacity that fast. <A> First, the term all-electric aircraft is already occupied for an aircraft in which all power sources except the engines are electric. <S> No hydraulics, no pneumatics, but still hydrocarbon fuel to store the energy. <S> Steps towards the all-electric aircraft, taken from this source . <S> Countless programs try and tried to electrify aircraft systems , the first from as early as WW II . <S> In most cases, the result is called "more electric" aircraft, because some systems like the landing gears in large aircraft still use hydraulics. <S> Full electric propulsion is discussed in the answers to this question . <S> Just because electric cars have become feasible with lithium batteries does not mean that electric aircraft are even remotely feasible. <S> Electric propulsion using highly efficient electricity generators burning either hydrocarbons or hydrogen are an interesting object of study but need many more years of development until they become feasible for commercial use.
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The gist of the answers is: Energy storage using batteries is out of the question, because the energy needs of aircraft are an order of magnitude greater than those of cars.
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What is the difference between ICAO Annexes and Documents? I have gone through many ICAO and aviation related sites, but I still can not understand the basic difference between annexes and docs. What is it? <Q> An Annex to the Chicago Convention on International Civil Aviation (which established the ICAO) is adopted by the ICAO Council according to particular voting procedures laid out in Article 90 of the Convention, and is binding upon the signatory States. <S> An ICAO document is just something the ICAO organization has chosen to publish in its Doc Series with an identifying number for ease of reference. <S> Being an "ICAO Document" doesn't in itself say anything about who wrote it or its legal force. <S> For example, Doc 7300 is the Chicago Convention itself, which has a lot of force (but not because it has a Doc number), whereas Doc 9562, Airport Economics Manual is more informative in nature and tries to be persuasive rather than authoritative. <A> There is no general consensus on the legal bindingness of the Annexes for the member states among jurists (Abeyratne, R., Air Navigation Law, 2012, Springer). <S> It is therefore difficult to establish a difference between ICAO Annexes and Documents. <S> Deviations from ICAO standards are listed in a country's AIP (Aeronautical Information Publication) in section GEN 1. <S> There is a different post on stackexchange suggesting that ICAO's documents (both SARPs and Docs) do not have the force of law: Do ICAO specifications have the force of regulation? . <S> What this legally boils down to in the different member states, I don't know. <A> An annex is quite literary what it says. <S> An "annex" states the Standards and Recommend practices (SARPs) expected from State signatories to the ICAO convention. <S> The documents expand on the SARPS explaining and/or nominating how and what a State has to do to achieve the SARPs. <S> In essence in simplistic terms an annex is the chapter heading of a book and the documents are the content of the chapter. <A> Actually an Annex contains SARPs (Standards And Recommended Practices) that are to be adopted (Standards) or that member states should try to adopt (Recommended Practices). <S> However documents contain further explanation and methods to implement SARPs.
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It is a document that is annexed (or "appended' or "attached") to the ICAO convention (where "convention" means a document).
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When crossing a mountain ridge at low height above terrain what consideration is given to turbulence? Some background: I am not a pilot, but a researcher studying air-flow across mountain terrain using Computational Fluid Dynamics (CFD). During my studies, I have been particularly interested by high-altitude ridges (2 to 3000m a.s.l., say 10000 ft) that are exposed to regional winds that are generally across the ridge. I have been seeing very interesting turbulence patterns above, and in the lee of the ridges (rotors). Here is the question: what instructions are given to pilots needing to cross such a ridge at low heights above the terrain, in either direction relative to the wind? What does common sense dictate? I am naturally thinking mostly of helicopter pilots doing mountain work, but any other aircraft are very welcome (fire-fighters, ULMs ...). <Q> From an older FAA Publication on mountain flying: <S> Mountain Wave <S> When the wind speed is above about 25 knots and flowing perpendicular to the ridge lines, the air flow can form waves, much like water flowing over rocks in a stream bed. <S> The waves form down wind from the ridge line and will be composed of very strong up and down drafts, plus dangerous rotor action under the crests of the waves. <S> If enough moisture is present, lenticular clouds can form to give a visual indication of the wave action. <S> These clouds are reported in the remarks section of hourly sequence reports as ACSL (altocumulus standing lenticular) or CCSL (cirrocumulus standing lenticular) <S> Pretty much sums up what you're seeing I guess. <S> As for action: Ridge and Pass Crossing On most mountain flights, you will need to cross at least one ridge or pass. <S> Experienced pilots recommend crossing a ridge or pass at the ridge elevation plus at least 1,000 feet. <S> If the winds at mountain top level are above 20 knots, increase that to 2,000 feet. <S> Plan to be at that altitude at least three miles before reaching the ridge and stay at that altitude until at least three miles past it. <S> This clearance zone will give you a reasonable safety zone to avoid the most severe turbulence and down drafts in windy conditions. <S> If conditions or airplane performance dictate, you may need to fly along the windward side of a ridge to find updrafts for gaining altitude before crossing a ridge. <S> You may also need to circle before reaching the ridge if climbing out of a valley airport. <S> When you actually cross a ridge, you should do so at a 45• angle to the ridge. <S> This allows you to turn away from the ridge quicker if you encounter a severe downdraft or turbulence. <S> Once you have crossed the ridge, turn directly away from it at a go• angle to get away from the most likely area of turbulence quickly. <S> Plan your crossing to give yourself the ability to turn toward lower terrainquickly if necessary. <S> As for helicopter mountain flying specifically, I'm afraid you are unlikely to find somebody on here with that experience. <S> You might have better chance on searching for it online and phoning up flight schools that offer such courses (I found a few in the states) for information. <A> Power pilots (which I am also) are the wrong pilots to ask about this topic. <S> We are trained to stay away from this kind of topography for all the reasons listed Glider pilots fly ridges and mountain wave all the time, very close to the ridge line. <S> My recommendation is to read the first part of Helmut Reichmann's Cross-country <S> Soaring called "Flight in Lift" which details the answers to the questions you're asking. <S> As far as helis are concerned, which I also fly, the the big considerations for mountain flying is how much excess power you have. <S> When you encounter a downdraft in a heli, you have to add power to arrest a decent, so it's important to know your power, weight, and density altitude limits. <S> There are a few helis that are known as good mountain machines, like the AS350. <S> In any aircraft, if you're going to fly in the mountains, you have to be able to read the signs: surface winds and winds aloft, cloud patterns, areas of airmass convergence, etc <A> I regularly watch a couple of YouTube pilot video channels and this particular one had a recent series on mountain flying. <S> There too much there to re-state here <S> but I think this particular video would be very interesting to you. <S> There are additional videos from this series that you might also find helpful.
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Ridges and mountains provide all sorts of lift, which is the key to great soaring, and we are taught to fly IN it, not away from it.
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Which wheel or wheels get the chocks? As a quick follow-up question to my earlier one about the retail cost of chocks , which wheel(s) typically get the chocks on a GA tricycle-gear plane? Do you buy one roped pair for the nose wheel (make sure your chocks are away before starting up), or two pair for the main gear, or all three (I doubt this, especially on a small plane)? <Q> To be most effective chocks should be placed on both of the main gear of light aircraft. <S> This prevents the aircraft from rotating or pivoting about the chocked wheel. <S> There's a nice article from the Flight Safety Foundation which talks about this. <S> The FAA, in an overabundance of caution, advises you to chock ALL the wheels (see AC 20-35C ). <S> Practically speaking, on a flat ramp and a calm day chocking any single wheel is usually enough to keep the airplane where you put it for a short while (say long enough refuel the aircraft, or to get lunch). <S> When using a single chock my preference in these cases is to chock the nose wheel as it's the most visible (I fly a low-wing airplane, and an inattentive line person who needs to tow the plane could miss a chock on the main gear). <S> For anything longer than that a brief food and fuel stop, or when high winds are anticipated, aircraft should be properly secured (by tying them down and chocking at least one wheel). <S> In these cases the tiedowns serve as the primary securing mechanism, and the chocks as a secondary mechanism (keeping the plane from rocking fore and aft in high winds and breaking the tiedown ropes). <S> Note that there is an exception to the "high winds" bit here: <S> If winds strong enough to blow chocks around on the ramp are anticipated, such as a hurricane, the chocks should be removed unless they can be adequately secured to ensure they don't get blown into an aircraft. <S> Of course if winds that strong are anticipated you should really have flown away before they got to you, or you should be looking for a hangar to weather the storm in. <A> Normally, the chocks are put on the main wheels (the wheels under the wings). <S> If you just chock the nose wheel and there is no tie down <S> then the aircraft could pivot/rotate. <S> Just to clarify the situation... <S> At airports there are two main parking areas, the "ramp" and the parking area. <S> Usually there are tiedowns only in the parking area. <S> Also, the parking area is allocated, so you have to get permission to take up a slot there. <S> When you visit an airport short term most crews therefore park on the ramp and chock the wheels. <S> The problem arises that "short term" might turn into hours or overnight. <S> If strong winds develop, then a poorly chocked aircraft can pivot, come loose and roll away. <A> For tailwheel aircraft, I chock the main on the side with the door (usually right), and the tail to keep it from pivoting. <S> If there's a tail tie down, I will always tie down the tailwheel, and I will attempt to park into the wind. <S> As my instructor used to say "the flight's not over till the tailwheel is tied down"
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With two chocks the main gear should be secured on each side of the aircraft to keep it from pivoting.
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What exactly is VMO and how does it affect a plane when it is exceeded? I read an article that mentioned "V MO " speeds of a 747 and that the plane, when it exceeds its V MO , shakes uncontrollably and destroys itself. I've never heard of planes doing this and the article explained V MO in a way that is beyond my understanding. For someone that doesn't know much about aviation: What does V MO stand for and how does it affect planes when exceeded? If it does cause the plane to shake to the point that it destroys itself, why is that? <Q> $V_{MO}$ is a “maximum operating speed”. <S> It is one of many “ V-speeds ” defined for an aircraft that limit operation at various flight phases. <S> All V-speeds are indicated airspeeds ¹. <S> The $V_{MO}$ is the maximum permitted speed for the aircraft. <S> This includes a safety margin, so pilots can reasonably fly near that speed. <S> Exceeding it is not immediately dangerous, but as it reduces safety margins, is an incident that should be investigated. <S> There is another speed, $V_{NE}$, the “never exceed speed”, which is somewhat higher and which marks the point where things start to get dangerous. <S> Also these speeds have their Mach number counterparts², $M_{MO}$ and <S> $M_{NE}$. At high altitude, the same indicated airspeed (IAS) corresponds to much higher true air-speed, since indicated airspeed decreases with pressure, while the same Mach number corresponds to slightly lower true air-speed, since speed of sound only depends on temperature. <S> So at high altitudes, the Mach limits are reached first while at low altitudes the IAS limits are. <S> Exceeding the $M_{NE}$ has different effect, though also dangerous. <S> Above that speed flow separation occurs above the wing due to supersonic speed of the flow. <S> This leads to loss of lift and significant down-pitching moment (a.k.a mach tuck ), which aircraft not designed for supersonic flight may not have enough elevator authority to compensate. <S> ¹ <S> The airspeeds are given as IAS , the speed measured by pitot probes, so they can be directly compared to the indication in cockpit (aircraft with EFIS (“glass cockpit”) usually correct those measurement errors that can be estimated, showing so called calibrated airspeed (CAS) ). <S> However it may not be just a simple number but may be tabulated depending on other parameters. <S> In particular $V_{NE}$ and $V_{MO}$ may depend on altitude, because flutter depends on true airspeed (TAS) and at lower density (due to lower pressure at altitude) <S> the same TAS corresponds to lower EAS / CAS / IAS . <S> ² Mach number is true airspeed as fraction of speed of sound. <S> In this case the limiting factor is formation of shockwaves due to the flow speed locally exceeding speed of sound around some parts of the aircraft. <A> Vne is defined in terms of True Airspeed (TAS), while all other V speeds are Indicated airspeed (IAS). <S> Gliders are particularly susceptible to the aerodynamic issues that define Vne because they fly at high altitudes and have long wings. <S> Since determining true airspeed in the cockpit would require a calculation, gliders have tables in their flight manuals and placards in the cockpit that show Vne in indicated airspeed at various altitudes. <A> There have been several incidents where a Boeing 747-SP, B747-100, B747-200, and B747-400 have exceeded not only Vmo, Mmo, and the Vne speeds and still survived, not “shaking itself to pieces.” <S> These aircraft were damaged, of course, but there hasn’t been a case of the B747 aircraft ever being lost due to a catastrophic in-flight breakup due to the excursion of exceeding the Vmo, Mmo, and/or Vne speed/Mach numbers.
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When the aircraft exceeds $V_{NE}$, aeroelastic flutter may develop that will destroy the aircraft and/or important parts may break off as the dynamic pressure becomes higher than what they are designed for.
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Does an increase in air temperature actually improve aircraft performance? Mainly because of what pilots learn about density altitude and aircraft performance, any idea that an increase in temperature could improve performance seems counterintuitive. And indeed it is. Here's what got me thinking about it. In studying for a written test I ran across a question phrased something like this: An aircraft flying at a constant power setting flies from a colder temperature to a warmer temperature. What happens to true airspeed and true altitude? The correct answer turned out to be that true airspeed and true altitude both increased. I knew immediately on the altitude because I remembered reading how very cold temperatures can cause dangerous errors in altimeters, but the airspeed didn't make sense. I still don't understand why the increased temperature lead to an increase in true airspeed. Obviously a reciprocating engine doesn't perform better in warmer air. We don't install "interwarmers." Does it really mean that warmer air can actually improve performance? Or does this need a deeper explanation? <Q> Drag (and lift) increases with density. <S> Density decreased and so did drag. <S> So at the same power , you can fly faster. <S> Now I don't know whether reduction of power of a normally aspirated spark-ignition reciprocating engine at constant throttle setting would be higher or lower than the reduction of drag. <S> But the question says power setting. <A> True airspeed is equivalent airspeed corrected for non-standard pressure and temperature. <S> With a increase in temperature, TAS has no choice but to increase. <S> Notice that IAS did not increase. <S> It has nothing to do with engine performance. <A> A higher temperature means the molecules are moving faster. <S> Assuming a constant atmospheric pressure, that would translate to less number of air molecules in the same amount of space. <S> Now, drag is caused by the airframe hitting the air molecules. <S> There is less drag, but the power setting stays the same - i.e. the force of forward thrust is constant, but the force of drag is smaller. <S> Airspeed increases. <S> So the question assumes that the loss of power is compensated by an advancing the throttle.
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Of course, with most engines, if the throttle setting stays constant, engine power is less in warm air.
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What would prevent the installation of windows on the roof of an airliner? What prevents airline manufacturers from putting a strip of glass along the roof of the aircraft? It would be a good addition in terms of cabin view, light inside the cabin, etc. Would it compromise the structural integrity too much? Edit: The image is for representational purposes only. My question does not pertain to a installation similar to this image <Q> There are a few factors involved in this and you should check out this answer that touches on window size (same issue really). <S> For what its worth the ceiling is prime real estate on an aircraft. <S> Modern airliners have the over head baggage compartments there (which provide a remarkable amount of space) <S> The area is also used to run cabling (electronics mostly these days) fore and aft as well as power to the reading lights etc. <S> However it should be noted that these things could most likely be routed along the floor just as well. <S> The real issue comes back to windows being a weak point and <S> glass being heavy. <S> When it comes to planes you want them to be as light as can be so excess windows will only reduce useful load and increase potential failure points. <S> On top of all that you will have more ambient light in the plane which may bother those trying to sleep on late night flights. <S> If you want a better view fly an unpressurized plane! <S> While on the topic of small bubble canopy planes, anyone that flies GA planes (especially like the ones shown above) with out air conditioning will tell you how hot it gets on the ground (and even at lower altitudes flying) in the summer. <S> The canopies make the inside of plane behave like a green house and really heat up. <S> This would make the inside of a jumbo jet really bake in the summer while taxiing (which can be a long process at big airports). <A> The same thing that prevents them from just having glass down the entire length of the fuselage, rather than discrete windows: the ribs of the frame. <S> This picture from cpast's answer on UX.SE shows how the windows are placed relative to the frame: <S> I'm assuming the cost/benefit ratio <S> there was just deemed not worthwhile. <S> Having them directly above the passengers wouldn't work because that's where the overhead storage bins are. <S> In the case of wide-body aircraft (like the one picture above,) note that the actual top of the fuselage is quite high. <S> In addition to the overhead storage bins above the passengers, there is often other stuff between the ceiling of the passenger cabin and the actual top of the fuselage, such as crew rest quarters, pipes, cables, or, in the cases of the 747 and the A380, another entire passenger cabin. <S> An additional problem with this is that it would make it harder to control cabin lighting, unless the windows were electrically dimmable, like the new ones on the 787. <S> Longer flights will usually want the passenger cabin to be dark-ish in order to accommodate the passengers who want to sleep. <S> With the windows beside them, passengers can open or close their window depending on how much light they want. <S> That wouldn't work for windows in the ceiling (since they would affect multiple rows of passengers.) <S> Further Reading Window size limitations are also discussed in <S> Why aren't airliner windows aligned with their seats? <S> and the previously-linked question on UX.SE . <A> One other consideration is that the crown of the fuselage is under significant tension*, and glass does not have appreciable tensile strength. <S> *Think of the fuselage as a tube being held up midway along its length (i.e., by the wing). <S> The weight of the fuselage and its contents will cause bending about the center wing box, putting the crown in tension, the keel in compression, and the sides under shear. <S> The shear can be channeled around the window frames but normal loads would require far more structure for the same. <A> The structural arguments have already been discussed, but a further thing to consider is that there really is no point. <S> For the small windows on airliners (necessarily small for the structural reasons outlined) the only person who gets a decent view is the person in the window seat, who has a wide angle view by virtue of being right next to the window. <S> The person in the aisle seat (or the centre block of a widebody) is lucky if they catch a glimpse of land out of the window. <S> A window on the ceiling of an airliner, besides being to far from anyone to give anyone a decent view, would be be pointing straight up at the sky. <S> All you would see would be blue sky, cloud (under certain weather conditions while below cruise height) and blazing hot sun. <S> I recently flew from London to Guanzhou, China, on a 787, on which the designers made the appalling high-tech decision of using dimming windows instead of traditional shutters. <S> The windows don't dim all the way to black, and the sun shining through the window is a real distraction when you're trying to sleep. <S> Who would control the shutters on roof windows in an airliner?
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On smaller aircraft, they probably could install small windows like the ones beside the passengers in the roof of the aisle, but it would add design complexity and also heat up the cabin (especially when sitting around on the ramp.)
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Can planes flap their wings like birds? Birds use their strong breast muscles to flap their wings and give them the thrust to move throught the air and fly. In a way, birds use a swimming motion to get the lift needed to fly. Plane wings have a similar shape as bird wings, but instead of flapping their wings, we use engines to thrust them into the air and create the lift needed to fly. ( Source ) Can we design an aircraft which could also "flap" its wings to fly?Yes, we would need fuel to anyways do that. But, from a design point of view, is it possible to do that? <Q> However, this presents some problems when scaled up for human flight. <S> One issue is the square-cube law : as the wings are scaled up, the area scales as a square (relating to lift), but the volume scales as a cube (relating to weight). <S> This means the wings increase in weight faster than they increase in lift, resulting in less effective wings. <S> The higher weight presents issues in making them flap. <S> ratchet freak pointed out that we do have such machines, and they are called ornithopters. <S> Although there is some potential at smaller sizes ( for small UAV's ), the weight and force issue prevents them from being very useful at larger scales. <S> Ornithopters were some of the first unsuccessful designs for heavier than air flight . <S> The best solution we have found is propellers. <S> This doesn't work as well as biological propulsion, but it's much easier to spin a prop than flap the whole wing, and works much better for the larger scales we need to move humans. <S> Flapping is also not effective for reaching higher speeds. <S> You can also see from the biological side that there is a size limitation. <S> The largest birds are much smaller than our airplanes. <A> There can be several reasons: Airplanes' wings are huge and heavy. <S> Birds' wings are light. <S> A bird's wings are flexible but an airplane's are not. <S> A mechanism to flap an airplane's wings will be a very complex process. <S> A lot more power will be required to flap airplanes' wings (even if flapping wings are designed successfully) than the current jet engines. <S> The flight will not be as smooth as it is now in airplanes, as a bird constantly moves up and down when it is flapping its wings. <S> This can be seen in this picture of an ornithopte : <S> Did you spot this airplane flying in the evening sky? <S> An interesting article about this: <S> Why don't airplanes have flapping wings? <A> It seems the answer is yes , but only for a very short period of time (as seen in this video ). <A> Yeah! <S> It is possible to build an aircraft that flaps its wings to fly, but the fuel efficiency, complexity of design and cost required for that flight would be a burden to implement. <S> This has been attempted in the past, but virtually all designs have failed, mostly for mechanical reasons. <S> The commercial aircraft and their working principles are a far more satisfactory design to carry payload in a cost-effective manner. <S> An ornithopter design, were it successful, would require more energy and mechanical complexity to carry even a small payload.
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From a biological point of view, flapping wings is a viable means of flight.
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Why is it more difficult for ATC to manage a larger airliner? After playing a few ATC simulation games, and reading at a few places (don't remember where), I am certain that it is more difficult to manage a larger airliner for the ATC. Suppose that one A320 and one A380 is trying to land at a certain airport. In another case, if two A320s are queuing up for landing, what extra precautions would the ATC have to take in first case, mainly in separating the aircraft and ensuring that they are on time? <Q> There were historically 3 classes of aircraft for the purpose of wake turbulance classification <S> H (Heavy) aircraft types of 136 000 kg (300 000 lb) or more; M (Medium) <S> aircraft types <S> less than 136 000 kg (300 000 lb) and more than 7 000 kg (15 500 lb); and L (Light) aircraft types of 7 000 kg (15 500 lb) or less. <S> With the introduction of the A380-800, where it is near MTOW, a fourth category has been added Super Heavy for Airbus A380-800 with a maximum take-off mass in the order of 560 000 kg <S> How much time must be left? <S> Well that depends, for an A380: <S> Arriving Aircraft MEDIUM aircraft behind an A380-800 aircraft — 3 minutes; LIGHT aircraft behind an A380-800 aircraft — 4 minutes. <S> Departing Aircraft <S> 3 minutes should be applied for a LIGHT or MEDIUM aircraft and 2 minutes for a non-A380-800 HEAVY aircraft taking off behind an A380-800 aircraft when the aircraft are using: the same runway; parallel runways separated by less than 760 m (2 500 ft); crossing runways if the projected flight path of the second aircraft will cross the projected flight path of the first aircraft at the same altitude or less than 300 m (1000 ft) below; parallel runways separated by 760 m (2 500 ft) or more, if the projected flight path of the second aircraft will cross the projected flight path of the first aircraft at the same altitude or less than 300 m (1 000 ft) below. <S> Source for timings: http://www.skybrary.aero/index.php/Airbus_A380_Wake_Vortex_Guidance <A> Multiple reasons I can think of <S> (but I'm no pilot <S> so I may be wrong!) <S> : Bigger aircraft are more constrained in terms of which runways they can accept clearances to land on & take off from Bigger aircraft typically need more room to maneuver into holding patterns, change Flight Levels, make turns etc. <S> Larger aircraft cause more wake turbulence and need to be provided larger separation behind them especially if the following aircraft is much smaller in size Bigger aircraft need longer to slow down and are constrained in which taxiways they can exit via. <S> or whether they will accept LAHSO clearances Bigger aircraft (especially the really big ones) typically have fewer options in terms of parking bays, ramps, tugs etc. <S> that can service them which imposes further restrictions for ramp controllers and ground movements. <S> Bigger aircraft have higher stall speeds in general and higher landing speeds too. <S> So a controller is limited in how much (s)he can ask a Heavy to slow down while executing his plan. <A> I wouldn't say more difficult. <S> But it definitely needs extra care. <S> That's mostly for 2 reasons: Inertia. <S> Bigger aircraft have more mass, more inertia and thus cannot change their kinetic status easily. <S> So ATCOs should have that in mind when vectoring aircraft and should issue commands earlier. <S> Wingtip vortices . <S> Wingtip vortices are a function of lift. <S> More lift is needed to keep a heavier aircraft flying, so this aircraft will cause more powerful wingtip vortices. <S> Those can be dangerous and pose a threat for planes landing right behind heavier ones.
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They must leave a greater amount of time in between landings/take-offs as the size of the aircraft increases due to wake turbulance
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How could an airliner as big as B777 make a U Turn on ground? I just heard about this 4 month old incident, where a United Airlines B777 made a U-turn, while it was on way to runway. What is the turning radius required to make such a U-Turn? Also, is so much space available near the taxi area at the IGI Airport? At last, is this a common practice for airliners to do? <Q> Turning Radius, as found in a planning document: 28.7m for a Boeing 777-200 34.7m for a Boeing 777-300 Rotating around one a point a bit off the wing to allow both wheels to roll throughout. <S> Minimum Pavement Width 47.5m for a Boeing 777-200 56.0m for a Boeing 777-300 Source Be aware that this is not exactly ideal- <S> visibility from the flightdeck is not great and you do not want the gear running into the grass or edge lights. <S> An Emirates A380 screwed up in Warsaw not too long ago when trying to pull this stunt. <S> Since this width is not normally provided by the runway (even Heathrow only has 45m and 50m runway width), you will add turning pads at the end unless there are taxiways you can use instead. <S> Source <A> The longest 777 s have steerable wheels on the mains and also a GMCS (ground cam showing the wheels) to assist pilot. <S> If you want to make the smallest turn with an aircraft you have to use differential braking and asymmetrical thrust: Press hard on the toe brake on the side you want to turn, tiller full deflection and increase thrust on the opposite side. <S> However this is some stress on the tyres and landing gear. <S> Data are available on that link, section 4.2 http://www.boeing.com/assets/pdf/commercial/airports/acaps/777_2lr3er.pdf <A> Such a turn is started after lining up with the edge of the runway, stopping the aircraft completely,locking the brakes on the inner side of the turn and applying thrust to the outer engine on the turn. <S> The wheels on the inner side of the turn will be really locked and subject to a high stress, and there is potential for tyre and runway surface damage. <S> Such a turn on a B777-300 would require a minimum runway width of 43.6 meters. <S> It is a procedure that involves ground crew coordination and supervision and quite a risk both for the personnel involved, the landing gear and tyres and the runway surface, so it is not a normal manoeuvre, probably used only in an emergency situation where no other option is available. <S> Having a tug to manoeuvre the aircraft around could be a much better option.
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Theoretically it is possible to make a pivot turn on a B777, according to the Flight Crew Training Manual (FCTM) from Boeing.
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Why do trijets (3 rear engines) usually have a T-tail instead of a normal tail? I'm thinking of trijets like the Tu-154 , which has three jet engines in the rear. Not something like L-1011 Tristar which has only one engine at the rear. Tu-154: Source: Wikipedia L-1011 TriStar: Source: Wikipedia Why do these kinds of jets have T-tails? Maybe the side jets get in the way of a conventional tail, but it looks to me like you could just raise those engines a little bit and enough room would appear. My understanding is that T-tails add complexity. The vertical part of the tail has to be strengthened (more weight) since it undergoes more forces. So a conventional tail seems preferable. <Q> A T-tail is not so bad. <S> Its main advantages are: A smaller vertical tail is required, because the horizontal tail acts like an endplate and enhances the efficiency of the vertical tail. <S> By designing the junction with the vertical well, the T-tail has less interference drag. <S> It also helps to reduce wave drag, especially when using a well designed Küchemann body (the round, long, spiky thing on the tail junction of a Tu-154) by stretching the structure lengthwise. <S> As soon as the cruise Mach number demanded tail sweep, the T-tail became the preferred solution. <S> In the days before CFD , it was much easier to get the wing right when no pylons with barrels at their ends were sticking from it. <S> If an engine is mounted near the place where normally the horizontal tail would be, it is much easier to relocate the horizontal to the top of the vertical than trying to join both together. <S> The mass of the engines will require a relatively rearward wing position, so the lever arm of a conventional tail would be rather small. <S> By shifting it up to the top of the swept vertical tail, its lever arm is much larger, making the T-tail especially attractive for configurations with rear-mounted jet engines. <S> A second reason is better failure tolerance. <S> Note that the T-tail designs are from the early jet age. <S> Their first flight years were: Caravelle 1955, Jet Star 1957 (both not real T-tails, I know, and having little tail sweep), <S> Trident 1962, VC-10 1962, Ilyushin 62 1963, <S> Boeing 727 1963, Tu-134 1963, <S> C-141 <S> 1963, <S> Hansa Jet 1964, <S> Tu-154 1968. <A> You want clean, undisturbed air flowing over the control surfaces. <S> You could probably squeeze it in someplace above or below the engines, but it would not be easy without negatively influencing the aerodynamics over the elevators. <S> As you can see from the diagram, you would need to get them pretty far out of the way of the engine cowlings. <S> If you place either engines or elevators low down along the fuselage they suffer from the disturbed air coming of the wing; this is not desirable. <S> As it stands, the side engines (#1, #3) are already angled for the downwash . <S> As for the more need for a sturdier rudder, this is partially weighed against that you have a longer moment arm. <S> (source: state.gov ) <A> Complexity. <S> The worst possible design would be like this: Horizontal and vertical stabilizers are mounted to an engine each... <S> So you triple the maintenance difficulties you have with <S> a MD-11 or DC-10. <S> And you want an easy access to the engines as possible - which requires enough space. <A> You can't have a horizontal stabilizer where the engines are mounted. <S> It's either one or the other at this location. <A> A horizontal tail that is actually mounted to the fuselage wouldn't work well in a design with jet engines mounted to the fuselage, because it would be directly in the jet exhaust, so it comes down to chosing between a cruciform tail (Caravelle style), or a modified version with the horizontal tail closer to the fuselage, but still above the jet exhaust stream, or a T-tail. <S> Clearly the T-tail has won out, in the airliner world. <S> Other answers give some hints as to why. <S> You might say that if you are going to have the complexity of a horizontal tail mounted to the vertical tail at all, you might as well get the additional benefits of the T-tail. <S> Yet the T-tail does have some disdvantages over a horizontal tail mounted lower on the vertical tail. <S> The Falcon family of business jets shows that 3 engines in the rear and a horizontal stabilizer mounted fairly low on the vertical tail can work well- see https://www.dassaultfalcon.com/en/Aircraft/Models/7X/Pages/overview.aspx . <S> Every aircraft design is influenced by many competing factors and it's hard to set hard-and-fast rules as to what will work best.
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When the vertical tail is swept, a T-tail will allow to make the horizontal tail smaller as well, because it gains additional lever arm in this configuration. Placing the engines at the rear fuselage put them higher, so FOD became less of a worry, and the wing could be kept clean for maximum lift resulting in shorter runway requirements. The designers were afraid an engine failure would also damage the horizontal tail and would turn a survivable accident into a lethal disaster.
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What is the relation between airspeed and altitude at fixed throttle setting in a private jet? In the world of private jets, say a G-450, at a fixed throttle setting, does it simply go faster the higher it climbs/flies? <Q> The basic principles needed for an answer are: Thrust varies linearly with air density. <S> Lift at constant angle of attack (AoA) equally varies linearly with air density. <S> Increasing the angle of attack from a low value will improve the lift to drag ratio (L/D), while increasing it from a higher value than the AoA at optimum L/D will decrease it. <S> The aircraft will settle at the point where speed equals drag and lift equals weight. <S> If the altitude change improves L/D, the aircraft has excess thrust to fly faster. <S> Due to the atmospheric lapse rate , the speed of sound decreases with altitude. <S> Above a certain Mach number ($M_{dd}$ = drag divergence Mach number ), drag increases nonlinearly over dynamic pressure. <S> Now the answer depends on where you start: <S> Low altitude, moderate throttle setting <S> : The aircraft will speed up, because it was flying at a low AoA in dense air. <S> Climbing brings it closer to the polar point of optimum L/D. Low altitude, high throttle setting: If the aircraft flew at close to its $M_{dd}$, climbing will put it in colder air where it needs to fly slower to maintain the same Mach number. <S> Depending on the starting speed, the aircraft might slow down. <S> High altitude, moderate throttle setting: <S> Now the thrust decrease with altitude will dominate the equation, because the aircraft will fly close to its optimum polar point. <S> Once it flies above the AoA of minimum drag, climbing will slow it down. <S> High altitude, high throttle setting: If it flies above the tropopause and close to the polar point of minimum drag, the air temperature does not change with altitude, and climbing will not change flight speed. <S> It will stay close to its $M_{dd}$. <S> Once it flies above the polar point of minimum drag, however, climbing will again slow it down. <A> There are a lot of aspects that complicate it, but assuming you're basically asking 'at full throttle, does an aircraft travel faster at higher altitude?' <S> the simple answer is yes, up to a point. <S> Obviously that doesn't apply above the service ceiling, and the optimal altitude may be lower than this. <S> The optimal altitude will be a function of the engine performance and airframe. <A> As altitude increases, the primary effect on aircraft is the reduced density of the air it flies through. <S> A reduction in air density has three key effects on flight: <S> Power at a constant setting decreases, because the air-breathing engines we use have less air to use for combustion and to push against. <S> Lift also decreases for the same reason; the aerodynamic lift surfaces (wings) are pushing less air and therefore the forces pushing the wings (and the rest of the aircraft) upward are reduced at a given angle of attack. <S> Drag is decreased, because less air means less friction drag and weaker wake vortices. <S> This is usually offset somewhat by the need to increase angle of attack, which increases induced drag. <S> So, as the air thins, your engines produce less power, but you need less power because your drag is reduced, but that's offset by the need to pitch up to regain lost lift. <S> The net results are an overall decrease in aircraft performance (ability to climb/turn and max speed), but (to a point) increased fuel efficiency. <S> One last effect is a reduction in temperature. <S> By the ideal gas laws, cooler air is denser than warm air at a constant pressure, however the equation is dominated by the reduction in pressure.
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Simple answer: within normal operating altitudes, mostly yes, due to the thinner air causing less drag while the engines are producing approximately the same amount of thrust Other simple answer: it depends, and there will be an optimal altitude above which the aircraft travels slower due to the engines losing thrust.
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How are squawk codes assigned? How are the 4-digit squawk codes assigned to individual flights? This answer indicates that there should be a "correct" one. How does ATC know what is "correct" and what is "incorrect"? <Q> To start out with, I'll be referring to how the US does it, and it's generally laid out in the National Beacon Code Allocation Plan . <S> Every facility has various blocks of codes that they can use to assign to flight plans, as described in the linked document. <S> For example, a smaller tower/approach control, could use the codes 0101-0177 for IFR flights that are only in their airspace, and 0201-0277 for the VFR flights that stay in their airspace, and a Center would have a similar bank of codes for flights just in their airspace, and then a different bank for codes that go to different centers. <S> The whole purpose to these allocations, is to minimize the need to change the squawk code while in the air, and to avoid overlap with adjacent facilities. <S> As flight plans are submitted to the various computers, about 30 min before an Instrument flight plan's proposed time, it's officially assigned a code from the available blocks, and it's printed at the departure airport or facility that'll first work it. <S> Flight plans stay in the system, depending on however long the center sets. <S> Often it's 2 hours, sometimes 3, but during bad whether when lots of flights are being delayed, it could be extended to 4+ hours. <S> The drop interval helps to keep enough codes available for aircraft intending to depart, while allowing flight plans to go away if something happens and the flight won't be departing. <S> If the aircraft just randomly calls ATC, the controller types it in to either the radar or flight plan system, depending on what extent the pilot wants services, and then the system prints out an appropriate beacon code. <A> A squawk code (aka Mode A code) is used in Flight Data Processing systems to correlate a radar track (or other surveillance system track) to a flight plan. <S> Basically the radar downlinks the squawk code from the aircraft and the FDPS looks up the associated flight plan. <S> Usually there are a number of codes which do not link to a flight plan but are reserved for local purposes and VFR flights without a flight plan. <S> In Europe there are 3 Mode A code allocation systems in use: <S> Originating Region Code Assignment Method (ORCAM) <S> Under ORCAM aircraft are assigned a code on departure and will maintain this code until they fly into a region where their code conflicts with another flight. <S> Then it is reassigned. <S> Centralised Code Assignment & Management System (CCAMS) <S> Elementary Surveillance (ELS) <S> When using ELS, if a flight needs to be (re-)assigned a mode A code and it is in Mode S radar coverage and the downlinked aircraft ID correlates with the filed flight ID on the flight plan, Mode A 1000 is assigned. <S> Squawk 1000 serves as a signal to the Flight Data Processing System to correlate the radar track to the flight plan based on the downlinked Mode S aircraft ID instead of the Mode A code. <S> This method is usually used in combination with ORCAM, sometimes with CCAMS. <S> By using ELS, multiple aircraft fly with squawk 1000 which frees up other Mode A codes. <S> This Eurocontrol document (PDF) gives some more detail about the code allocation schemes in use. <S> South America and the Caribean use the ORCAM (PDF) system. <A> In the US, the codes follow section 5 of the 7110.65. <S> Non-discrete codes end in 00 and can cover multiple aircraft. <S> Discrete codes never end in 0 and are specific to one aircraft. <S> "How does ATC know what is "correct" and what is "incorrect"?" <S> The computer system generates them. <S> There are certain "slot ranges" for every facility. <S> It's not that the controller punches in something he came up with on his own. <S> He requests a squawk from the system, and then the computer spits out one, and that's the one <S> he/ <S> she tells the pilot over the radio. <S> To answer your question on how it knows correct vs incorrect, I'd have to say that this is implemented correctly in the software that runs the backend.
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In CCAMS a computer system allocates codes to flights based on the planned trajectory through the CCAMS area and ensures there will never be a code conflict. For every region there are 'local' codes which are only used for regional / domestic flights, and there are 'transition' codes for region boundary crossing flights.
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I hold both a Sport Pilot License and a Student Pilot certificate. Can I do my BFR in a C-172? FAR § 61.56.(c).(1) states that every two years I must have Accomplished a flight review given in an aircraft for which that pilot is rated by an authorized instructor. The answer to my question hinges on the exact meaning of the word "rated". If I've been signed off to solo in a C-172, am I "rated" for that aircraft as far as this regulation is concerned? <Q> Nope, sorry! <S> If you need a flight review, use an LSA you have been endorsed for. <S> §61.56(c)(1) <S> states that a flight review must be: <S> Accomplished <S> [...] <S> in an aircraft for which that pilot is rated According to the AOPA (note: this article is specifically targeted at non-Sport pilots): <S> Rated is interpreted as category and class <S> [emphasis mine] <S> And in another article , the AOPA continues: <S> Sport pilot certificates will be issued without category/class designation ... <S> and just for the final nail in the coffin, here's the FAA itself (thanks, @Pondlife!), in AC 61-98B : <S> For example, a sport pilot who holds airplane privileges could not take the flight review in a Cessna 172 since that airplane is not a light sport airplane and he or she does not hold operating privileges for that airplane. <S> Long story short, this all means that no , a Sport Pilot cannot perform a flight review in a non-LSA type. <S> Because you require specific logbook endorsements in make/model for category/class/speed (an LSA like a Sting S3 vs Airplane Single-Engine Land ), you are not rated to fly a Cessna 172, for example. <S> Your solo endorsement isn't a rating, as it isn't part of a certificate - it's an endorsement. <S> Once you become a Private Pilot, you'll be able to do a flight review in almost any ASEL type , including <S> all LSAs because you're suddenly rated for the Airplane category and Single Engine Land class, with no light-sport-only limitation. <S> As far as I can tell, your student pilot certificate is actually invalid. <S> It's been superseded by your Sport Pilot certificate and you are now adding privileges to that certificate. <S> As such, it doesn't really matter that you've been endorsed for solo in a 172; you aren't rated to fly one in the same way you are for an LSA. <A> As mentioned above, but hard to see - once you pass any check ride and you are a pilot (sport, recreation, private, commercial or airline transport) so no longer a Student Pilot. <S> You are a Pilot; different rules apply for adding a new category/class to your Pilot Certificate. <S> A Flight Review (Hasn't been a "BFR" since 1997. <S> The FAA's preferred term is "Flight Review," read the Advisory Circular!) must take place in an aircraft for which the pilot is rated. <S> 61.56 provides useful alternatives. <S> One of these is training via the FAA's Wings program. <S> In the OP's case, three dual flights in the 172, combined with some online training, could provide credit for the flight review. <S> Just a little planning/coordination with the instructor is required. <A> According to Flying Magazine January 2010, it sounds like, yes you can: <S> Q: I'm a private pilot flying at the Sport Pilot level. <S> Can I take my flight review in the Cessna 172 <S> that's available at my local FBO? <S> A: <S> The requirements for a flight review are called out in 14 CFR 61.56. <S> The regulation requires the flight review to be accomplished in an aircraft for which the pilot is rated. <S> Since you are a private pilot you are rated to fly the Cessna 172 (assuming you have an Airplane Single Engine Land rating on your pilot certificate), so this would meet the requirement of the regulation. <S> Since you don't hold an FAA medical certificate, you would not be authorized to act as pilot in command (PIC) during the flight portion of the review, but Sec. <S> 61.56 does not contain a requirement for the pilot taking the flight review to hold a medical certificate or to act as PIC, so this is not a problem. <S> The flight instructor performing the flight review will act as PIC during the flight. <A> If you currently hold a Sport Pilot Certificate or other grade of Pilot Certificate, your Student Pilot Certificate is no longer valid in the eyes of the FAA and the law. <S> Therefore <S> §61.56(c)(1) governs this and the flight review must be conducted aboard an aircraft which the pilot is appropriately rated to serve as PIC aboard.
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A pilot who holds only a sport pilot certificate may only take a flight review in a light sport aircraft for which he or she holds an operational privilege.
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Are pilots generally trained for crosswind landings? A YouTube footage of a KLM Boeing 777 landing at Schiphol airport in the Netherlands is certainly scary as the plane bumps and weaves and rolls from side to side. Are pilots generally trained to handle such eventualities (or are such landings common in certain regions of the world?) or was everyone involved including the pilot taking a risk in this case without diverting the aircraft to a nearby safe location? <Q> Of course yes . <S> Crosswind landings , like the one in the video you linked, are very common. <S> In fact, landings with no wind or only headwind are rare. <S> There are <S> several techniques pilots are taught during their extensive training to land aircraft when there is crosswind. <S> The Wikipedia article I referenced above lists them. <S> Since your question isn't about them, we won't discuss them. <S> Certainly, extreme weather situation are not very common. <S> Some parts of the world experience extreme weather more than other areas. <S> Diverting to other airports is not always an option and in some cases, once an airplane is on the approach, going around becomes impossible . <A> In the US it is required by law to be trained in cross wind landings. <S> For large aircraft that require a type rating... <S> §61.31 Type rating requirements, additional training, and authorization requirements... ... <S> (2) Received a logbook endorsement from an authorized instructor who has found the person proficient in the operation of the aircraft and its systems. <S> (i <S> ) Normal and crosswind takeoffs and landings ; (ii) <S> Wheel landings (unless the manufacturer has recommended against such landings); and (iii) <S> Go-around procedures. <S> On a side note cross wind landings are very important since not all airports have 2 runway options. <S> Some large commercial airports will have 2 crossing runways which will allow you to pick the best one for the days winds (they are usually built to the general prevailing winds in the area). <S> This does not mean there will be no cross wind <S> but it does allow you to mitigate it. <S> Smaller airports may only have a single runway (or 2 parallel runways) which means you have no method of mitigation for the crosswind. <S> There are even some big airports that are only single runway due to space or geographic restrictions. <S> It should also be noted that airplanes them selves have a demonstrated cross wind component to which they are tested to be safe to land in a cross wind of said velocity. <S> This is not necessary a maximum (although it can be) but it is often used as such. <S> As for how often this happens that is largely a factor of the airport and the local weather. <S> For example I used to fly out of KPNE <S> they have 2 runway options (6-24 and 15-33) <S> they would use what ever was the best runway for the wind that day unless you needed the precision approach on 24. <S> This made landing there easy <S> (150 x 5000 or 7000 helped as well) as there was never really more than a 15 degree crosswind. <S> I now fly out of KDYL <S> which is a single runway airstrip that almost always has a crosswind <S> , really keeps you on your toes. <S> Cross wind approaches <S> are perfectly safe and are not out of the ordinary. <S> I have seen some people mistake the phrase <S> Uncoordinated Flight as meaning <S> a sideslipped crosswind landing is unsafe which is incorrect. <S> The plane can be uncoordinated because it is side slipping to the landing which is done deliberately by the pilot. <A> The answers so far deal with commercial flying, from a recreational perspective pilots are only as well trained as the amount they practice. <S> Commercial organizations generally train their pilots for crosswind landings in simulators, and they usually fly enough to get real crosswinds often enough to keep in practice. <S> Private pilots are trained in crosswind techniques in initial training, keeping good crosswind abilities is up to the pilot once they pass their test. <S> I personally practice crosswind take-offs and landings as often as I can, however I know many pilots who won't fly if there's more than 5 knots across the runway. <A> I trained on a Cessna 172 as Paso Robles. <S> The video was completely normal. <S> A roll of < 10 degrees is not serious at all, well within a competent pilot's operational abilities. <S> The news story was written by someone who doesn't fly, thought it looked 'scary' and filled 90 seconds with nonsense, IMO. <A> I'm a little late to the party, but here is my take. <S> In that landing I see turbulence <S> but I don't see an obvious crosswind component. <S> In any case, dealing with crosswinds is something that happens more often than not when landing (at least at many airports and airfields). <S> So every single pilot has dealt with this since the very first days of basic training. <S> As for the wing rocking, correcting an off-level wing is probably the very first thing a student learns when getting acquainted with the aircraft's controls. <S> It is completely intuitive for every single pilot.
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Yes, pilots are trained for crosswind landings.
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How do pilot and copilot operate and coordinate the radio? How do the pilot and copilot of a large commercial jet operate the radio when talking to ATC? Is there a push-to-talk button, or some voice-triggered mechanism? Also, how do they coordinate it? How do they decide which pilot should be talking to ATC? <Q> Both yokes have PTT buttons. <S> Generally one person is in charge of the communications. <S> In military aircraft that is often the task of the navigator in twin crew airplanes. <S> I would think it generally falls on the pilot not flying the aircraft although both should be listening to the instructions. <S> The switch is on the front of the yoke (reverse side from what the pilot sees) and is generally triggered with the left index finger. <S> Here is a pic from a yoke for reference. <S> Note the button on the left upper part labeled "mic". <S> source <S> I have never seen it (but then again there are many radios I have not seen) but some radios may have a VOX (voice-operated transmit) option which would bypass the PTT. <S> This however would be very irritating on the channels since there are lots of planes on a single frequency talking to the tower. <A> The headsets worn by each flight crew member typically feed into an integrated comms/cockpit voice recorder system, where whoever is wearing a headset (and the CVR) will always hear: anyone else wearing a headset, <S> the frequency(cies) being monitored on the comm stack, and the flight attendant handsets (if active and patched to the flight deck). <S> There is then a PTT button for each headset (usually on the yoke for pilots, back when there was a flight engineer his was a button on his desk or clipped to his uniform) allowing transmission on the selected COM frequency. <S> In simpler systems the entire "cockpit loop" is transmitted, while more complex radio systems provide degrees of isolation so other members of the flight crew can talk while the radio is open. <S> As far as who talks to ATC, that's usually worked out between the members of the flight crew, so it can vary between flight crews and also depends on the phase of flight, which one is the pilot flying etc. <A> On Boeing airplanes, flight duties are divided in PF (Pilot Flying) and PM (Pilot Monitoring). <S> This duties are defined at the beginning of the flight because it determine the "area of responsibility" for each pilot during all the flight or for phases of flight (for example: Captain can be PF during taxi and PM during the rest of the phases of flight). <S> In general, the area of responsibility for the PM, include the duty of COMMUNICATIONS, so this pilot is the one responsible for talking on the radio. <S> During the cockpit preparation the Captain determine which pilot will be the PF and the PM for the flight (or for the each phase of flight), so in that way every crewmember knows what are their duties, and who is going to be in charge of the radio. <S> I don't know the exact terms for PF and PM for other type of aircraft (I think that for AIRBUS is Pilot Flying and Pilot Not Flying) <S> but I think this flight duty division works for all types... <S> Hope this helps... <A> Many airplanes, large & small, have 2 (or more) radios that can be used individually via intercom settings. <S> Thus the pilot may be talking to or monitoring Center/Approach/Tower, while the Copilot monitors ATIS/ <S> AWOS/ASOS and gathering the weather, altimeter, runway in use, or talking to the FBO for parking arrangements after landing, or talking to Company for parking gate assignment/changes, etc. <S> So it's not strictly one pilot on one radio only.
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In some crews the pilot flying is also the pilot talking, while in other crews the pilot not flying (if not on "in-seat rest") will handle secondary tasks including navigation and radio.
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Why do full service airlines prefer to run a separate low-cost carrier? There are various full service carriers (FSCs) who have a separate low-cost carrier (LCC) subsidiary. For example: Germanwings by Lufthansa Air India Express by Air India JetKonnect by Jet Airways Why do the FSCs prefer to launch a separate LCC, rather than providing seats at a cheaper rate with reduced comforts within their existing structure? <Q> They still want to get into the low cost segment but want to market themselves differently for better penetration. <S> You can only present so many images of a brand to customers: You can't show both the super-cheap prices with happy youth on them and posh first class at the same time. <S> They do not want to tarnish a nice brand by mixing it with a low cost carrier and what that is perceived to entail. <S> For instance, Germanwings got a somewhat infamous reputation recently, and Lufthansa is probably happy their name was not more frequently used in media. <S> Low cost is also associated with less good customer service and hidden fees. <S> Crew are often less well paid, and they are sometimes put under a separate working agreement and company to try to prevent conflicts. <S> Some legacy carriers have very good pay which is difficult to reduce. <S> Management does not want to be bound by these when expanding or adjusting their business. <S> Each case is pretty specific depending on exactly they are trying to do and achieve. <S> For many American Carriers and Lufthansa, the last one is probably the principle reason. <A> As mentioned there are lots of branding issues around this <S> but there are also lots of corporate and legal reasons to do so. <S> Business Isolation : If you want to start out a bunch of new routes and you are not sure how well they are going to do a large airline <S> my not want to book that kind of loss or risk having to cover it. <S> Thus they can incorporate a "new" airline and protect their existing and profitable business interests should the "new" airline go under. <S> Likewise it also makes it easier, should it be very profitable, to potentially sell it off (or absorb it as well). <S> Taxes/Fees : <S> Tax law changes from place to place so this may differ depending on where they are based <S> but if there are different taxes as a result of company size or specific aviation taxes they may be able to take advantage of them by splitting up. <S> Legal Isolation <S> : I am no lawyer <S> but I am sure that how ever they set these up it isolates the parent airline should anything happen to the other carrier. <S> Image <S> /Branding : this has been touched on already but as mentioned you may not want the image that comes with running a low cost brand associated with your luxury brand. <A> Kind of like how some car companies have both "regular" and "premium" brands. <S> Eg., Chevy v. Cadillac or VW v. Audi, etc etc. <S> It allows for companies to have a more exclusive version of their product for people who are just the premium, exclusive sorts... <S> Granted there are other cost considerations, and other branding considerations, and I could probably sit here and go on for hours with that <S> but I think it would be a little bit outside of scope. <S> So, to just give a basic explanation: Different brands have different associations with them. <S> Some are seen as premium, exclusive, indulgent. <S> Others are seen as just hitting the basics. <S> And some companies will avoid mixing the two just for the sake of brand identity in marketing. <A> As mentioned in earlier answers, branding and management (pay, collective bargaining agreements, etc.) are certainly two major factors. <S> Interestingly, the two strategies are not exclusive. <S> Air France/KLM has several low-cost subsidiaries (Transavia, Transavia-France and HOP!) <S> but also introduced many low-costs tactics (no meal, surcharge for hold luggage…) on short-haul European routes on both legacy airlines. <S> The thing is that some elements of the low-cost model (paid refreshments, quick turnaround, routes to cheap airports or use low-cost terminals at major airports, single-class cabin with as many seats as possible, identical aircrafts…) can only be introduced for the whole airplane or even the whole fleet. <S> And for a highly price-sensitive market segment, merely using some elements of the model to offer lower prices is not enough, you need to go all in to ensure your fares are as low as those of your direct competitors (say Easyjet, not necessarily Ryanair). <A> A business reason no-one has mentioned yet is the original reason the big names started: Because low cost airlines began flying routes cheaply and created a market <S> If the big names hadn't joined in, all that revenue would have gone to the low cost airlines, who would have grown to the point they could potentially compete in the existing markets, so it was essential that the big players joined in. <S> It is not possible to run a low cost airline in the structures of a major airline (the cost model is entirely different - passenger demographics, services on board, pre-flight hospitality, additional benefits etc.) <S> so the only way to do it that makes financial sense is to run it as a separate logical entity. <S> It has proven to be a difficult change for some of those big airlines, with various attempts at creating budget versions failing, but some have managed to compete successfully.
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And legacy airlines are mindful of the risk to see their profit cannibalised by the new cheap fares so they need to maintain as much segmentation/price discrimination as possible. I would imagine this has to do with branding.
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Should landing light be off during line up and wait position? What is the proper position for the landing lights when on the runway in a line up and wait position? <Q> Counter-intuitively, the FAA answer (see chart on page 1-9 and text on page 1-10) is actually, they should be off during the line-up-and-wait phase. <S> When cleared to ... <S> “Line up and wait”—when entering the departure runway without takeoff clearance, turn on all exterior lights (except landing lights) to make your aircraft more conspicuous. <S> Then when takeoff clearance is received, the expectation is that landing lights will be turned on. <S> The best rationale I've seen for this is so that Tower controllers (and other aircraft) have an immediate visual cue that an aircraft "on the numbers" understands that it has been cleared for takeoff, or not. <S> Another FAA document, SAFO 11004 <S> (these are "best practice" recommendations, not requirements): <S> Exterior Lighting: o Taxi with taxi light on when moving, off when stopped. <S> o Turn on all exterior lights when crossing any runway. <S> o <S> If cleared to “Line Up and Wait”, turn on all exterior lights except landing lights. <S> o <S> When “Cleared for take-off”, turn on all exterior lights, including landing lights <S> o <S> If you see an aircraft in take-off position on a runway with landing lights ON, that aircraft has most likely received its take-off clearance and will be departing immediately. <A> I’d have it on for visibility. <S> Since you’re on the runway and pointed forwards, no landing airplane will see it, and no airplane in the pattern will be really close. <S> No airplane taking off will see it because they don’t have a rear view mirror. <S> It means one less thing to do before taking off, and lets you focus on the remaining checklist items before departing. <A> At a minimum it will serve to increase your visibility to other aircraft and service vehicles. <S> Taxi/ landing light courtesy does not apply to aircraft that are on an active runway.
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If you intend to use your landing lights, there's no reason they should be off as your aircraft crosses the hold short position. I’d turn it on once in position.
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