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Is constant air pressure maintained inside the fuselage? I just heard it somewhere but I'm not sure about it. If it is, then why don't they build airtight fuselages? <Q> For the purposes of air pressure inside aircraft, they are broken down into two broad categories: <S> Unpressurized - These aircraft are typically piston powered and can't go very high, so do not even attempt to regulate the air pressure inside the fuselage. <S> Pressurized - <S> These aircraft do maintain pressurization in the fuselage, but it isn't constant beyond a certain point. <S> The category determines the answer to your question: Unpressurized Aircraft <S> Unpressurized aircraft are not built air-tight for a couple of reasons: <S> It is very hard to make something as large as an airplane truly air-tight, and keep it that way. <S> Over time, seals will start to leak, fittings will loosen, etc. <S> The fuselage would have to be much stronger to withstand the pressure difference between the inside and the outside. <S> This would make them heavier and more expensive. <S> There isn't much need. <S> These airplanes don't fly high enough to really require a pressurized fuselage and a person can breathe more or less normally even though you aren't at sea level. <S> (Think of people that live on mountains.) <S> Pressurized Aircraft <S> Without going into the details of how an aircraft is pressurized (which isn't really relevant to your question), the air pressure inside the fuselage of a pressurized aircraft is usually maintained at sea level pressure up to a certain point. <S> However, the fuselage is designed to withstand a particular maximum differential air pressure, so in order to protect it (basically keep it from "popping" when the air pressure outside the airplane drops too low), the pressure is allowed to decrease when needed. <A> Many aircraft are not pressurized and therefore not airtight. <S> The occupants would suffocate, if nothing else, and most unpressurized aircraft do not regularly operate at altitudes requiring pressurization. <S> In the case of pressurized aircraft , it's actually necessary that the cabin is not airtight . <S> They are, instead, nearly airtight and can withstand significant pressure differentials. <S> Cabin pressurization works by bleeding high-pressure air from the engines, which is then run through packs (heat exchangers and air cycle machines ) to cool it. <S> After conditioning, the air is fed into the cabin. <S> This is what creates the lower cabin altitude relative to the outside atmosphere. <S> Because more air is constantly being added to the fuselage, a pressure outflow valve is required and it is constantly dumping air from inside the aircraft . <S> In normal operations, it's automatically controlled, but can be manually overridden in emergency situations. <A> Pressurized aircraft are not airtight, and neither are they constant pressure. <S> One key facet that would make being airtight impossible is the need to change pressure in the cabin. <S> To change pressure in the cabin, air is pumped in via the packs (covered in another answer), and air is let out via outflow valves. <S> The input is fairly constant flow and pressurization is modulated by how open/closed the outflow valve is. <S> Cabin pressure must change because the airframe has a maximum pressure differential between the cabin and outside (7.8 PSI in the EMB-145) <S> and as you climb the pressure in the cabin must be reduced. <S> The cabin is generally 8000 ft pressure altitude at during cruise. <S> Subsequently the cabin pressure is increased to the landing airport during descent. <S> Accompanying these changes in pressure are temperature changes naturally occurring as result of the pressure change (see: ideal gas law). <S> You may notice this during descents in regional jets as they tend to get very warm as the cabin is compressed. <S> To regulate the temperature, you need air conditioning, and so you have packs and air cycle machines to deliver air at the proper temperature to the cabin. <S> Now that you have to provide air into the cabin, its not worth even thinking about CO2 scrubbers and O2 tanks, because the packs take care of that with fresh air. <S> That should cover airplanes not being airtight, why they aren't airtight and that the also are not constant pressure. <A> The answers so far have talked about the differences between pressurized and unpressurized airplanes, however to answer your question why they're not airtight : <S> The answer is two-fold, first as egid pointed out, the pressure differential would probably be too great for the hull to withstand. <S> Second, and in my opinion, more importantly, humans consume oxygen and output carbon dioxide (and water). <S> Having your ship airtight, would cause everyone inside to slowly but surely suffocate from carbon dioxide poisoning and lack of oxygen as the little oxygen carried within the aircraft slowly gets breathed away. <S> So you need to keep replacing that air, and the easiest way to do that is to let the old air out, and put new air in. <S> Edit <S> As Dan Pichelman points out, people in Subs aren't dropping like flies. <S> True, they're not, but they are in fact also replacing the air. <S> Almost. <S> They're removing the CO2 (using Scrubbers) and adding Oxygen (from oxygen tanks). <S> It would probably be possible to solve it this way for aircraft as well. <S> The question remains whether it is feasible weight wise, and if it's easier to just pressurize the aircraft using bleed air and dump the old air overboard. <A> In many General Aviation aircraft (small planes that don't go above approximately 12,000 ft.), the air pressure in the fuselage is the same as the outside air. <S> Most people have no difficulties at altitudes up to 12,000 ft, so there is no need to maintain a pressurized environment. <S> Specific rules state that unpressurized airplanes have supplemental oxygen available, <S> depending on how high the plane is, for how long, and whether its flying during the day or night.
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In typical jet airplanes, the pressure inside portions of the airplane (typically the passenger compartment, some of the cargo holds, and maybe an avionics bay) at cruising altitude is maintained at a pressure which corresponds to an outside air pressure at an altitude of about 5,000 - 8,000 feet (referred to as " cab in alt itude "), depending on the cruising altitude and the design of the airplane.
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Can resistive fuel senders/transducers be repaired/reconditioned? I need to replace two fuel senders in each wing of a Socata TB20, and a replacement is almost $500. I wanted to know whether a shop exists in the US that reconditions these? After some research, I'm still not sure if reconditioning resistive fuel senders is common practice at all. I only heard anecdotically about it <Q> What's basically involved is cleaning the resistor element and wiper contacts, making sure everything is making good contact through its full range of travel, and verifying that the sender is still within a reasonable calibration range when you're done with the cleaning (you can use your other, working sender to determine what's "reasonable", or verify using your fuel gauge). <S> The Comanche folks have a nice article on reconditioning a (really beat up) fuel sender , and technologically they're similar to automotive fuel senders, so this article about reconditioning Corvette fuel senders may also be useful to get an idea of what you're in for. <A> While I have no personal experience with refurbished or reconditioned fuel senders, I did some research, and there do appear to be shops that will work on aviation units. <S> An alternate search has some different results. <S> These results imply that that it is both legal to recondition fuel senders, and that there are a few options within the US. <S> For the record, I wasn't able to track down a manufacturer or part number for the units used by SOCATA, which makes it a bit more difficult to research. <S> I do know that Cessna senders can be found for under $300 at McFarlane, if that gives you a price comparison, or in case one of those is the right unit. <S> Aircraft Spruce has even cheaper units (Rochester and Westach) <S> but I'm not sure why they are so cheap ; often the parts Spruce carries are not for certified aircraft, but that doesn't seem to be the case. <S> Either option is certainly cheaper than the price SOCATA seems to have quoted. <S> Good luck with your search, and if you find a shop or a part number, make sure to update (or comment on) your question! <A> It depends on the year and model and mod of your TB. <S> Earlier TB's had resistive sensors while the later ones have capacitive sensors. <S> There are also two sensors in each wing. <S> The gauge averages the reading because of the wing dihedral. <S> But what is the failure mode you are experiencing? <S> If it's inaccurate fuel readings <S> the original senders had hollow floats that happened to fill with fuel over time, riding lower and lower. <S> They issued an SB that replaced the senders with solid floats. <S> But it could also not be your senders. <S> The latest revision of the engine fluid, temp vertical cluster is Revision D. <S> Anything before Revision D was notorious for falling out of calibration. <S> Bad news, is that the 600 dollar cluster, when the plane were in production. <S> now costs 6 thousand <S> so it's better to try to trouble shoot the senders first. <S> So, before we go further, exactly what are you seeing?
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There are shops that do this and egid gave you a couple of hints on how to find one , but your local mechanic can probably recondition your fuel sender about as well as any of the specialty shops, as long as they're not squeamish about opening up the unit (and as long as the unit can be opened up - I'm not sure about the TB20 senders).
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How does an aircraft taxi? Does an aircraft use its engines to taxi or is it always pulled by some other vehicle? I have seen a small lorry pulling it sometimes; is it really pulling the huge thing, or does the aircraft use its own power somehow? <Q> Aircraft are not always moved with tugs <S> (the small vehicle you refer to). <S> Much of the time, they operate under their own power. <S> Airliners are generally pushed back from the gate using a tug, as that's the simplest and most efficient method. <S> They then taxi to the runway (and all the way up to the gate, after landing) using their own engines to provide thrust. <S> This is true of both jets and propeller aircraft. <S> Some work is being done on self-contained electric-powered ground propulsion; one major player in this area is a company called WheelTug . <A> Aircraft have no powered wheels, so the forward thrust comes from the engines. <S> Only pushback from the gate is mostly done by a tractor, although some aircraft can use reverse thrust for that. <S> When the aircraft is being moved for maintenance purposes or simply relocation at the airfield, the aircraft is usually pulled. <S> Research is going on into fitting electro motors into aircraft wheels so that they can taxi without having to start the engines. <S> Lufthansa has done some experiments . <S> The concept would save taxi fuel and is more friendly to the airport environment (noise, polution), however the additional weight of the motor drive system would offset these benefits because it causes additional fuel burn during flight. <A> Most aircraft taxi using their own engine power. <S> Tugs are usually only used to get an aircraft to a safe distance away from all structures, people, and other aircraft before engine start, or if the engine(s) are inoperable (maintenance, mothballing, etc.). <S> However, there is a system (called the ElectricGreen Taxiing System, introduced at the 2013 Paris Air Show) that attaches to the wheel and uses an electric motor to move instead of the main engine(s). <S> It is currently only available on the Airbus A320 family and the Boeing 737 family.
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They use high-torque motors and the aircraft APU to allow the aircraft to move itself without starting its engines or requiring a tug to be connected and disconnected. Usually an aircraft taxies under its own power.
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What makes the ailerons on an aerobatic airplane different than the ailerons on a non-aerobatic airplane? I often hear a spec of the "roll-rate" when talking about aerobatic airplanes and the term "fast ailerons." What exactly does that mean, and what makes the ailerons on an aerobatic airplane different than the ailerons on a non-aerobatic airplane? How does the design of the ailerons affect the roll-rate of the airplane? <Q> The faster the plane responds, the faster the ailerons (or other controls). <S> The roll rate is the speed at which a plane can complete a roll. <S> This depends on a number of factors, including aileron size, maximum aileron deflection, wing length, and speed. <S> Ailerons that can deflect a lot of air without disrupting the airflow over the wing too much are desirable in an aerobatic plane, so the roll rate can be increased and so the plane will have better roll control at lower speeds. <S> While larger ailerons are desirable on an aerobatic plane, they are also more susceptible to flutter at high speeds, which is not desirable because it tends to rip them off the wing. <S> There are several design techniques that can be used to mitigate this, such as gap seals, counterweights, countersurfaces, etc. <A> One of the distinctive feature often found on aerobatics aircraft ailerons are spades . <S> They are an efficient form of aerodynamic counterbalance that serve to reduce the effort needed on the stick to actuate the aileron. <S> They also serve to bring the centre of mass of the aileron forward of the hinge line in order to help prevent control surface flutter. <S> Pros Being more efficient than "normal" ailerons (i.e. achieving higher roll rate), aeroboatics ailerons would require much more torque to actuate (without counterbalance). <S> The stick should be as "light" as possible to increase flight precision and reduce pilot fatigue . <S> Cons <S> Having a lighter control force can make it more difficult to find the centrepoint of the control quickly. <A> I asked Patty Wagstaff at Oshkosh one summer how she was a able to get the airplane to flip tail over nose - I couldn't envision a set of control movements that would make that happen. <S> She told me the plane was balanced on knife edge and <S> that's what allowed it to be moved the way it was. <S> The spades mentioned above help provide the light control forces to allow the control surfaces to make the large movements.
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The term "fast ailerons" is an informal term that generally refers to the response of the plane relative to the pilot's input to the aileron controls on the stick or yolk.
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How is GPS RAIM availability calculated? I recently had someone ask me if there was a GPS RAIM availability calculator available for the iPad. There isn't, but it got me thinking that I could write one. After doing some searching, I can't find a good explanation of how to calculate RAIM availability, so am looking for the formulas used to calculate it for a specific route. I want this to be an offline tool, so the calculations need to be complete, rather than relying on a website for the information. <Q> The website that Ralgha points out is indeed the one to look at for the US. <S> They also provide a SOAP interface <S> should you want to create your own app for the IPAD. <S> For RAIM to be available, you need to check firstly that at least 5 satellites (Space Vehicles in GPS language) are visible from you position, or 4 if your RAIM algorithm uses Baro-aiding. <S> They have to be well above the horizon. <S> How much depends on your satellite receiver, the FAA uses 5 degrees on their website. <S> There are some receivers that use a masking angle of only 3 degrees. <S> Orbital equations can be taken from the GPS interface control document , section 30.3.3.1.3. <S> They take almanac data as input. <S> Apart from the Space Vehicle orbits, you also need to take into account their health from the NANU's . <S> With the satellites available, you need to calculate the RAIM containment bound. <S> This is the maximum size that a position error can grow due to a faulty satellite signal without the RAIM algorithm noticing it within 10 seconds (with a 99.9% probability). <S> If that containment bound is more than 1 nautical mile, RAIM is said to be unavailable for terminal procedures. <S> For NPA a 0.3 nautical mile radius is used. <S> The containment bound depends very much on the geometry of the satellites, more that on the number of satellites available. <S> The problem with the RAIM algorithms is that they aren't standardized. <S> There are several ways to perform RAIM and because GPS manufacturers use proprietary solutions there is little information available to the public. <S> So calculating the containment bound is where you will get stuck. <S> So there is no easy way to implement RAIM prediction on an IPad, apart from using the FAA website. <S> Europe has also a RAIM prediction website; AUGUR . <A> You'll need the orbital equations to calculate that though. <S> It would probably be easier to pull data from one of the websites that provide RAIM information. <S> http://www.raimprediction.net <S> is the FAA's site. <A> Details of RAIM calculation is explained in the paper : <S> GPS EASY Suite II: <S> easy13 - RAIM by Kai Borre http://www.insidegnss.com/auto/julyaug09-borre.pdf <S> Also the author gives a Matlab implementation. <S> Hope it helps.
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RAIM availability calculations are simply checking to see if at least 5 satellites will be visible, that's all it is.
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What is the minimum possible number of hours required to carry passengers? Not factoring learning curve, personal safety minimums, and pilot proficiency, what is the absolute minimum flight time that must be logged in order to carry a passenger in a piston engine aircraft in the United States? I'm am looking for an answer for the airplane category. Not gliders or ultralights. <Q> A sport pilot can carry a single passenger and the minimum requirements are outlined in 14 CFR §61.313 : <S> If you are applying for a sport pilot certificate with [...] <S> Airplane category and single-engine land or sea class privileges, <S> Then you must log at least [...] <S> If a sport pilot applicant logged exactly 20 hours, got signed off, and then passed their checkride on the first attempt... <S> they would be able to fly passengers as soon as they completed the checkride. <S> That means, realistically, probably 21 to 21.5 hours. <A> Zero, if you bring along a flight instructor :-) <S> You fly the plane, the flight instructor keeps you safe and legal, and your passenger sits in the back seat. <A> Max 1 passenger and <S> 750kg total weight <S> 46.5 hours will get you a PPL. <S> You can carry up to 19 passengers, beyond that you need a type-rating on the airplane, so you add a few more hours (depends on airplane) <S> 202 hours will get you a CPL. <S> Same as above, but now you are allowed to charge them for the flight.
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I believe the answer, at least in the US is 20 hours of flight time, plus however long a checkride takes. 20 hours of flight time, including at least 15 hours of flight training from an authorized instructor in a single-engine airplane and at least 5 hours of solo flight training in the areas of operation listed in §61.311, Top of my head: 11.5 hours can get you an Ultralight license.
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What process do I follow to land a civilian aircraft on a military base? Let's say I have business on a US military base (e.g. JBLM), and I'd like to fly a privately owned aircraft there. What is the process I follow before the flight to get approval to land, and once I'm enroute to ensure everything goes smoothly? <Q> Landing at a US military base isn't all that hard (I've landed at Ft. <S> Drum before), you just have to get prior permission (PPR) (submitted at least 30 days in advance and confirmed within 24 hours according to 32 CFR 855.8), and need to have a "good reason" (as determined by them). <S> 32 CFR 855, Table 1 (which is quite long) includes the purposes that are normally allowed. <S> You will be required to submit the following forms to the base commander <S> (See the A/FD): <S> DD Form 2400 - Civil Aircraft Certificate of Insurance <S> DD Form 2401 - Civil Aircraft Landing Permit DD Form 2402 <S> - Civil Aircraft Hold Harmless Agreement <S> 32 CFR 855 contains the regulations pertaining to US Air Force airfields (and the rules are similar for each branch). <S> 855.1 - Policy includes: (1) <S> Normally, landing permits will be issued only for civil aircraft operating in support of official Government business. <S> Other types of use may be authorized if justified by exceptional circumstances. <S> Access will be granted on an equitable basis. <S> ... <S> (3) <S> Any aircraft operator with an inflight emergency may land at any Air Force airfield without prior authorization. <S> An inflight emergency is defined as a situation that makes continued flight hazardous. <S> 855.5 - Responsibilities and authorities. <S> includes: (6) Will not authorize use of Air Force airfields: (i) <S> In competition with civil airports by providing services or facilities that are already available in the private sector. <S> Note: <S> Use to conduct business with or for the US Government <S> is not considered as competition with civil airports. <S> (ii) <S> Solely for the convenience of passengers or aircraft operator. <S> (iii) <S> Solely for transient aircraft servicing. <S> (iv) <S> By civil aircraft that do not meet US Department of Transportation operating and airworthiness standards. <S> (v) That selectively promotes, benefits, or favors a specific commercial venture unless equitable consideration is available to all potential users in like circumstances. <S> (vi) <S> For unsolicited proposals in procuring Government business or contracts. <S> (vii) <S> Solely for customs-handling purposes. <S> (viii) <S> When the air traffic control tower and base operations are closed or when a runway is restricted from use by all aircraft. <A> A "Joint Base" does not refer to joint military and civilian, it refers to Joint as in co-use by multiple branches of the services. <S> If you show up unannounced as an emergency aircraft, they will not point guns at you or detain you, they will simply handle your situation, provide the help and resources you need to get the aircraft back in the air and send you in your way. <S> There are only a couple bases that have "security at the ready" and will meet you with armed individuals. <S> The military is not some war-crazed institution waiting to shoot people, the bases are staffed with civilian controllers as well as a military and they are there to help when and where they can in aviation. <S> My experience flying both military and civilian aircraft for over 30 years has only produced professional accolades for the folks on the bases around the world. <S> If you have official business, it should be easy to land there with prior permission, if not- don't go or ask. <S> If you have an emergency, do not hesitate to use the installation, it is funded by your tax dollars and they will be happy to share. <A> I'd never heard of JBLM <S> but I guess you're referring to Joint Base Lewis-McChord which has the identifier KTCM? <S> Airnav says it's joint civilian and military use, AOPA says <S> it's private military, but <S> the AF/D <S> says it's joint, which should be the definitive answer. <S> If so, as a joint field then civilian flights should be OK <S> but I would carefully read the entire AF/D entry as well as any other information it references <S> and if you have any doubts or concerns at all then you should contact them in advance. <S> Even if you don't, I would still contact them anyway and in this case the AF/D tells you to do exactly that: <S> tran acft parking extremely ltd. 24 <S> hr prior coordination rqr <S> Landing at a private military field on the other hand would require special permission from the military which I assume is very unlikely to be granted unless you have good connections on base. <S> Update from an anonymous user: <S> The reason that AirNav says 'joint military/civillian use' is that at one time KGRF (the airfield on the Army side of JBLM, then a separate installation - Fort Lewis) had an 'Aero Club' that operated a flight school & rented Cessnas for use by the base population. <S> They also allowed troops who owned personal aircraft to base them on field at the Aero Club. <S> That Aero Club facility closed due to insufficient use during the height of Iraq/AFG deployments, and with it civil use of the JBLM runways ended. <S> The ramp space is now used by military aviation units (an Army Combat Aviation Brigade) that moved to JBLM after the Aero Club closed. <A> The comments are all over the place on how to land a civilian aircraft onto a military airfield. <S> Here's how you really do it:1. <S> Get signed copy of a DD 2400 from you insurance company.2. <S> Fill out DD Form 2401 and 2402.3. <S> Submit all forms to the military service HQ in Washington DC for the airfield you want to land on. <S> Address is on the forms. <S> (JBLM belongs to Army and Air Force. <S> Army airfield, Army permission.4. <S> Once permission is granted, you have to contact the airfield manager and submit documents required by the airfield manager. <S> Bottom line: You have to have an association with the military to land your aircraft onto a military field; i.e. active duty, retired, contracted. <S> I've been landing at military airfields for over 20 years.
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If you want to land on the McChord airfield, you have to have Air Force permission.
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What is the difference between LNAV/VNAV and LPV minimums on an RNAV approach? This approach shows two sets of minimums that both have vertical guidance with a Decision Altitude (DA). What is the difference between LNAV/VNAV and LPV, and why does LPV have lower minimums? <Q> There's an FAA paper on RNAV approaches that explains the differences between LP, LPV, LNAV and LNAV/RNAV approaches. <S> I made a table for my own reference but since StackExchange doesn't allow tables (AFAIK) here's a summary: <S> LP: no vertical guidance; <S> WAAS required; MDA for minimums LPV: vertical guidance; WAAS required; DA for minimums LNAV: no vertical guidance; WAAS not required; MDA for minimums; requires RAIM integrity if WAAS is not available LNAV/VNAV: vertical guidance; WAAS or baro-VNAV required; DA for minimums; requires RAIM integrity if WAAS is not available (i.e. if using baro-VNAV); possible temperature restrictions if using baro-VNAV <S> Other answers have additional comments about LNAV/VNAV having been designed earlier and for different equipment which would certainly make sense. <A> LNAV/VNAV approaches were originally designed for larger, more sophisticated turbine aircraft utilizing onboard Flight Management Systems (FMS). <S> These types of approaches uses barometric altimeters and ground radio equipment to compute a descent path and add vertical guidance to an existing non-precision approach. <S> An LPV approach still provides vertical guidance but is not a precision approach. <S> In this type of approach WAAS GPS satellite and ground-based data are used to provide the aircraft with the vertical descent information. <S> Usually a WAAS approved GPS navigator, like the Garmin 430w, is capable of flying both LPV and LNAV/VNAV approaches. <A> LPV is a higher precision approach requiring equipment beyond what is needed for LNAV/VNAV. <S> In particular you need dual WAAS recievers in a certified installation. <S> The improved guidance is what allows the lower DH. <S> See this link for more information. <A> . <S> A LPV approach can provide WAAS vertical guidance as low as 200 feet AGL. <S> LNAV/VNAV approaches also provide approved vertical guidance and existed before the WAAS system was certified. <S> At that time, only aircraft equipped with a flight management system (FMS) and certified baro-VNAV systems could use the LNAV/VNAV minimums. <S> Also the design of an LPV approach incorporates angular guidance with increasing sensitivity as an aircraft gets closer to the runway. <S> (This is intentional to aid pilots in transferring their ILS flying skills to LPV approaches). http://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/techops/navservices/gnss/library/factsheets/media/RNAV_QFacts_final_06122012.pdf <A> LPV - Localizer Performance with Vertical Guidance is some kind of enhanced satellite navigation with an required accuracy of 16 meters in the horizontal and 20 meters in the vertical plane during 95 percent of the time, achieved by multiple special GPS (WAAS) receivers. <S> Obviously this accuracy allows to reduce the minima on the approaches. <A> In order to get the LPV minima you need: 1 <S> - An approach certified SBAS/WAAS capable receiver 2 - That the GPS+SBAS signals are good enough for LPV approach (horizontal and vertical protection levels low enough) <S> If you have an approach certified GPS receiver without WAAS, then no LPV/LP for you, but there are still the possibility of getting a VNAV or a pure LNAV approach depending on your installation and GPS signal quality. <S> In essence you will always automatically get the best minima possible. <S> The receiver will tell you which one automatically. <S> Look up the documentation for your GPS receiver. <S> Dual receveivers are NOT required ! <S> There is also the possibility of getting an LPV, but with a higher DH/same visibility if the signal quality is within LPV250 but outside LPV requirements.
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The difference between LPV and LNAV/VNAV is that although they both have vertical guidance, LPV was intentionally designed to be very similar to an ILS approach with an increasingly sensitive glideslope whereas LNAV/VNAV was not.
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Are there any aircraft with a nose wheel braking system? I'm pretty sure that there are no aircraft equipped with a brake on its nose wheel, however two of my colleagues think there might have been. Are there? Aircraft with retractable gear of course have devices to stop the wheels from spinning when retracted, but I'm asking about brakes used to stop or slow down the aircraft. Please don't consider aircraft with a tail wheel, gliders, experimental aircraft, or aircraft used for flight testing (certified aircraft only). <Q> (Also they were proven to be ineffective and unreliable, so a service bulletin was written to remove the system). <S> Saab Gripens use nose wheel brakes to stop as well, the main gear sits farther aft than most planes, so there is quite a bit of weight on the nose gear, which makes it effective for stopping. <A> The Messerschmitt Me-262 had nose wheel braking as well. <S> Back then, with the high landing speed of jets and no thrust reversers, the engineers wanted to give pilots as much stopping power as possible. <S> Here is a picture which shows the brake line running down to the wheel: <S> Abandoned Me-262 after the war ( <S> picture source ) <A> Good question. <S> With regards to mainstream commercial jets it might not do much and quite possibly be counter-productive. <S> Most (all?) <S> Boeing and Airbus have about 95% of weight on the main landing gear (MLG), and thus the nose brake wouldn't be very heavily weighted, so not very effective. <S> And for reasons of rotation, you don't want to load the nose very much, but rather have it pivot around the wings: where your lift is coming from. <S> You can then design the nose landing gear (NLG) to be quite light because it doesn't see a lot of load, nor take large braking reaction forces. <S> And doesn't have any brakes/hydraulics etc. <S> And the same with the fuselage strength: it's okay if the MLG take all the load: they are already in the "beefy" section of the plane, and there is no moment arm (torque) due to a big displacement from the centre-of-gravity (CG). <S> However if you started to have large forces on the NLG, you have it a long way from the CG, and thus a big moment: you'd need to take that into account when you designed the fuselage, making it stronger, and thus heavier. <S> At the moment with no lift on the front fuselage section, nor any forces from braking, you can make it pretty light. <S> Having the MLG at the CG and also centre-of-lift from the wings (drag from spoilers) makes for a very stable system. <S> Inherently stable too: the faster you go, the more drag from the wings, and thus more weight on the MLG, which they need. <S> I think this will be the case for all planes with propulsion from the wings: regardless if props or jets. <S> If you have a prop on the nose it's a bit different because you need to beef that up anyways, so you don't mind the braking loads from a nose-wheel. <S> But I don't see a lot of advantages for it. <S> You add all the extra weight of the hydraulics and brakes, plus the weight from making a much stranger assembly. <S> More complexity, more to service and go wrong. <A> Ahaha!! <S> There IS in fact a non-ultralight aircraft out there that has its ONLY brake on the retractable nosewheel. <S> That aircraft is the Verhees Delta. <S> Uniquely, that aicraft has only two wheels (tandem, or bicycle undercarriage) and they are in line, one wheel at the front, retractable, and another, same size, <S> 9 feet further aft, at the rear of the aircraft. <S> There is a small bumper wheel at the tip of each wing. <S> The aircraft lands on the rear wheel - (the nose is very high, during landing as this is a delta wing aircraft). <S> When it has slowed down enough the nosewheel leg makes contact with the runway and it can begin braking. <A> 50+ B727-200 were equipped with nose brake systems. <S> I have a B727 nose wheel cap with anti-skid. <S> I have no idea what it is worth <S> but it's a great conversation piece.
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There are quite a few 727 that actually had nose wheel braking, however they utilized it only for maximum braking power.
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What is the procedure when being vectored for an approach and ATC allows you to pass through the final approach course? If you are on a heading, being vectored to intercept final on an instrument approach, and it appears that you will fly through the final approach without being cleared to intercept it, what should you do? <Q> Usually when ATC has a need to vector you across the final approach course, they will tell you about it before they do. <S> Something along the lines of "N1234 fly heading 230, vectors across final for spacing. <S> ". <S> If they don't <S> and you see that you are getting close <S> , you should ask them if they want you to intercept the course. <S> The AIM addresses this in paragraph <S> 5-4-3 Approach Control : (b) <S> After release to approach control, aircraft are vectored to the final approach course (ILS, MLS, VOR, ADF, etc.). <S> Radar vectors and altitude or flight levels will be issued as required for spacing and separating aircraft. <S> Therefore, pilots must not deviate from the headings issued by approach control. <S> Aircraft will normally be informed when it is necessary to vector across the final approach course for spacing or other reasons. <S> (c) <S> The pilot is not expected to turn inbound on the final approach course unless an approach clearance has been issued. <S> This clearance will normally be issued with the final vector for interception of the final approach course, and the vector will be such as to enable the pilot to establish the aircraft on the final approach course prior to reaching the final approach fix. <S> The FAA Air Traffic Control Order Section 9 - Radar Arrivals also has the following directive for approach controllers: 5-9-3. <S> VECTORS ACROSS FINAL APPROACH COURSE <S> Inform the aircraft whenever a vector will take it across the final approach course and state the reason for such action. <S> NOTE- <S> In the event you are unable to so inform the aircraft, the pilot is not expected to turn inbound on the final approach course unless approach clearance has been issued. <S> PHRASEOLOGY- EXPECT VECTORS ACROSS FINAL FOR (purpose). <S> EXAMPLE- “EXPECT VECTORS ACROSS FINAL FOR SPACING.” <A> This is one of the most confusing areas of IFR flight. <S> Controllers will use many different phrases like "turn to heading XYZ... intercept the localizer" or "... join the localizer" or "... <S> report established" etc. <S> Oftentimes before they will issue the clearance, which they hold back as long as possible. <S> They want you to turn to XYZ and then turn again onto the final approach course. <S> This would appear to be against their guidance but it happens quite often. <S> Note, you are not "cleared" for the approach yet, even though you are maneuvering onto the final approach course. <S> You must maintain your last assigned altitude and speeds until cleared. <S> To answer your question, if you are "turned to heading XYZ" but not cleared for the approach nor told to "join" the final approach course/localizer/etc. <S> , I would confirm if the controller wants you to fly through the final course (or he just forgot about you). <A> One more thing to consider - lost comms. <S> This scenario here is a classic for thinking about what your actions will need to be in the event of Lost Comms. <S> Keep track of WHY those vectors are being given to you - where are they taking you, when should you expect headings that would make sense in regards to shooting the approach, etc. <S> Always be questioning what ATC tells you to do (and of course call them if it does not make sense) <S> Always try to think "what comes next", this will help you prevent problems when "what comes next" is an error on either their behalf, or yours!
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If approach course crossing is imminent and the pilot has not been informed that the aircraft will be vectored across the final approach course, the pilot should query the controller.
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What should I do with fuel drained from the sumps during preflighting? What should one do when done sumping a small amount of fuel during a pre-flight? Should it be dumped on the ramp? Or is it considered necessary to find the container far away from the airplane? Is it considered safe to dump it right back into the plane if it is uncontaminated? <Q> The FAA issued an Aviation Safety Program publication called All About Fuel which talks about fuel preflight, including sumping fuel. <S> It contains the following: <S> Preflight Action <S> As pilot in command, you have the responsibility to determine that your aircraft is properly serviced. <S> Check your aircraft before each flight and be sure you have the correct type of fuel. <S> This practice may save your life! <S> Take the time to inspect your aircraft thoroughly. <S> Good preflight procedures: <S> Be sure all of the fuel and oil tank caps and covers are installed and secured properly after you visually check the fluid level. <S> Observe the color and odor of the fuel as you check the tank. <S> Draw a generous sample of fuel from each sump and screen drain into a transparent container. <S> Check for the presence of water, dirt, rust or other contaminants. <S> Note: If you are not equipped to safely pour the drained fuel back into the tank, please be sure to dispose of it in accordance with EPA regulation. <S> Check that each fuel tank vent is clear of restrictions; i.e., dirt, ice, snow, bent or pinched tubes, etc. <S> Any FBO that sells fuel should have a way to dispose of it. <S> Some of them make it more obvious than others by putting sump barrels out on the ramp, but ask them what to do with it before you go out to the airplane <S> and they should be able to help you out. <S> For environmental reasons, you definitely shouldn't dump it on the ground, because even if it does evaporate, it will come down somewhere. <S> At some airports you can even get in a lot of trouble (and have to pay a big fine) by dumping fuel on the ramp. <S> Don't take a chance! <A> Personally, I have a gas powered tug to pull/push my plane with. <S> My tug is only certified for mogas, but I pour all of my avgas samples into it... <S> I've <S> never had to fuel it any other way. <A> Barring that, the best option is a type of fuel strainer called a GATS jar that has a built-in filter to catch any particulates. <S> If you pull a sample in a GATS jar that comes back <S> "dry" you just unscrew the filter and put it back in the tank. <S> If you pull water, you should dispose of it in a way that doesn't involve dumping it on the ground. <S> Either put it in a disposal container (lobby your airport or FBO to install them if they don't exist) or your own labeled gas can and use it for your lawnmower or something. <S> If you have no other option, try to avoid pouring it in a puddle on the ground. <S> Toss it in an arc <S> so it covers a large area and can evaporate as quickly as possible <A> I always put it back in the tank if it's not contaminated. <S> Even if it is I'll put as much as I can back in. <S> A few millimeters of water is not going to do anything when it would take almost a gallon of it just to reach the fuel pickup. <S> As for dumping, I've heard the EPA has been known to watch airports with heavy flight activity. <S> They'll write your tail number down and send you a fine. <S> Some states don't have any laws about it, though. <S> I would save all the fuel I could, honestly. <S> You can filter out uncontaminated fuel and reuse it. <S> I know that's not really plausible if you're not in a hangar, though.
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You should dispose of it in a fuel disposal container, if your airport has them (and many states require it). Unless you have the proper kind of fuel tester (e.g., GATS jar with intact fuel strainer), do not attempt to save the fuel drained from the sumps by pouring it back into the tank.
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Could the CVR and FDR record to the cloud? Another enthusiast question. I watch a lot of the National Geographic Channel's "Air Crash Investigation", for better or worse, and it seems accident investigators make tremendous use of the Cockpit Voice Recorder "CVR" and Flight Data Recorder "FDR" to determine the chain of events leading up to- or the root cause of an accident. One of the more recent episodes of ACI (Season 12 Ep. 13) was about Air France 447 , the worst disaster in French aviation history. That investigation spent two years and $50 million just locating the CVR and FDR which were ultimately found resting 4 kilometers beneath the mid-Atlantic. Even after the recovery, there were concerns one of the drives had failed. That ACI episode also mentioned that the Airbus A330-203 in that accident came equipped with a system which periodically transmitted maintenance data to a remote Airbus location in Paris to alert ground crews of possible maintenance issues with inbound aircraft. Given that Airbus already uses similar technology for maintenance data (and I think I recall hearing Boeing does too), I was wondering if either Airbus, Boeing, or the FAA, plan to facilitate or mandate that the CVR and FDR record to the cloud or a remote location either in lieu of or in addition to the physical devices installed in commercial aircraft. I would think this would be an accident investigator's dream come true, with almost instant access to vital investigative information, while drastically reducing instances of going without these crucial tools when the physical devices are unrecoverable. So, does anyone in the know have any idea if there are plans for CVR and FDR data to be transmitted and recorded to the cloud or a remote location? <Q> There are hundreds of parameters being recorded many times per second plus the voice channels. <S> Today's airliners record 500 GB of data on each flight . <S> Take this and multiply it by the thousands of airplanes that are in flight at any given moment, and you can see that there would need to be a lot of bandwidth available for all of it to be transmitted wirelessly. <S> There would also need to be a world-wide standard developed and hardware deployed so that an airplane can transmit the data no matter where they are. <S> Airplanes operating in remote locations would have to use satellites, which are relatively low speed and expensive to deploy/maintain/operate. <A> Could we record everything to the cloud? <S> No. <S> For one thing, we just don't have the storage capability and communication bandwidth. <S> Transmitting data from a plane travelling at mach 0.85 over the atlantic is no mean feat: we've managed it, but it isn't like a home fibre connection running at a steady 100Mbit/s or more. <S> Add in the fact that currently we aren't saturating the satellites right now... <S> but if suddenly every plane was transmitting at full speed constantly, both the frequencies used, and the satellites themselves, would quickly be saturated. <S> We would need a LOT of satellites and a much larger frequency band allocated to that transmission type. <S> Then there's storage: there are thousands of planes in the sky, recording several gigabytes of data per hour. <S> Perhaps if we used a similar "keep 24 hours of data" strategy, this could be manageable. <S> On the other hand, we could, and probably should, transmit and record some data, or at least more data than we do now. <S> At the very least, we should be able to transmit basic telemetry and control input positions, along with perhaps a little information regarding engine power settings etc. <S> They wouldn't necessarily be up to the level of the Flight Data Recorder of Cockpit Voice Record information, but it would at least give us something to work with. <S> Since MH370, there's talk of ensuring we, at the very minimum, know the location of every aircraft in close to real time, so if nothing else we should be able to localise the search area faster in future. <A> Commercial aircraft do transmit a limited amount of data via ACARS . <S> This information can only be received line of sight, so if the aircraft is over the ocean the information will not be received (except by a ship that might be randomly listening). <S> The information on a flight data recorder is stored to a tape or other high-density storage and contains gigabytes of information. <S> It would be impossible to transmit this much data via a normal radio due to insufficient bandwidth. <S> You could potentially transmit this much data with a microwave link, but this would require a complicated satellite-based system. <S> Military drones, like the Global Hawk , do make such transmissions (the big dome on top is the microwave antenna). <S> Even if you equipped commercial aircraft with such bulky transmitters, you would need to launch thousands of new satellites to listen to and receive all the transmissions from the thousands of planes. <S> So, while it may be technically possible, the cost and complexity of such a system is way beyond what is currently viable.
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In short, it just isn't practical with today's technology. The basic problem with transmitting CVR & FDR data to the ground from flight is the sheer amount of data that is generated by today's sophisticated airplanes.
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Why are updraft carburetors standard in aviation? My only detailed experience with carburetors is in aircraft. I'm pretty familiar with the principles behind float-type carbs, but I recently saw a schematic for a "downdraft carburetor" with a choke valve. This got me curious, so I did a little research and found that what I'm used to is an "updraft carburetor", and that (according to wikipedia) they fell out of fashion in the automotive industry in the 1930s . Why is the updraft carburetor design so prevalent in aviation? Does an updraft carb actually have a choke valve? Images below to provide a little context for those of us who are not engine experts! Typical aviation carb: Typical downdraft automotive carb: <Q> I can think of three reasons to use an updraft carburetor in a single-engine GA airplane: <S> Anti-flooding: <S> The float-bowl regulator in your carburetor is cheap and simple, but it is far from perfect under all conditions. <S> Short periods of zero-G or negative-G operation, caused by a quick dive, turbulence, or even bumping over uneven ground, can jiggle the float and spill liquid fuel into the venturi. <S> In a downdraft or sidedraft carburetor, this liquid falls into the intake manifold and wets the interior walls and may get into the cylinders, causing an over-rich mixture condition. <S> The engine is said to be "flooded" and will not run until the liquid is cleared out. <S> Gravity feed: <S> If your aircraft has fuel tanks higher than the carburetor when in cruise attitude, you may be able to remain under power if your fuel pump fails. <S> An updraft carburetor can be mounted lower in the engine compartment than sidedraft or downdraft types; in fact, it is usually under the engine. <S> Early automobiles did this to avoid the need for a fuel pump; fuel was fed by gravity from a fuel tank higher than the carburetor, e.g. just below the windshield. <S> The lower the position of the carburetor, the deeper the fuel tank could be. <S> Convenience: If you look inside the cowling of most GA planes, you will see much more space under the engine block than above it. <S> That seems to be the best place for lots of auxiliary equipment and attachments, including the carburetor and air filter. <A> You get a lot of answers about shorter intake manifolds, less probability of flooding the cylinders if your carb floods, and many other things. <S> But to me, it comes down to one big issue: visibility. <S> You need to mount your engine high enough that you have adequate prop clearance without having to have long, heavy landing gear struts. <S> So you mount your engine fairly high on the airframe. <S> Now do you want to have a carburetor sitting on top of that engine directly in the pilot's field of view? <S> Why would you do that when you have all that space down below the engine? <A> I dont know but when reading about the Northrop P-61 <S> Black Widow WWII US night fighter <S> I found this in Wikipedia : <S> XP-61 development <S> In March 1941, the Army/Navy Standardization Committee decided to standardize use of updraft carburetors across all U.S. military branches. <S> The XP-61, designed with downdraft carburetors, faced an estimated minimum two-month redesign of the engine nacelle to bring the design into compliance. <S> The committee later reversed the updraft carburetor standardization decision (the XP-61 program's predicament likely having little influence), preventing a potential setback in the XP-61's development <S> The fact that they made the decision to only use updraft carburettors, even though they later reversed the decision, indicates that there must be a good reason - maybe you can find the committee's notes on the subject.
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With an updraft carburetor, the spilled fuel tends to fall out before it can foul anything.
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Rotax engines have no mixture control, how do they handle less dense air? Rotax engines have no mixture control, yet they don't seem to have any more problems than other engines at altitude. How do they handle the lower air density in order to not get a too rich a mixture? <Q> According to this owners manual 4.5 High altitude compensator (H.A.C. kit) <S> H.A.C. is a high altitude compensator developed by ROTAX which adjusts the air/ fuelmixture automatically from sea level to 6500 m altitude using aspecial BING carburetor. <S> This page has information on how the Bing carburetor works (with pictures!) <S> : <S> Here's how it works <S> Did you ever wonder what makes fuel flow up the jets, from thecarburetor float bowl, enroute to the engine? <S> Is it vacuum at theventuri? <S> That's not quite descriptive enough. <S> It is better defined asa differential pressure between the float bowl and the venturi. <S> What'sthe pressure in the float bowl? <S> Here is an important hint, the bowl isvented to outside atmosphere. <S> So, it should be the same atmosphere, orambient pressure, that's feeding the airfilter. <S> If it is not, thedifferential between the venturi and float bowl is going to change andso will the mixture... <S> Maybe richer, maybe leaner. <S> Just think of thatfor a second. <S> If fuel air mixture can be thrown off, accidentally byimproperly venting the the float bowls, why not control the venting toeffectively control mixture? <S> That's exactly what your Bing 54 can do,automatically, when a High Altitude Compensator is added. <S> Ifpressure in the float bowl is reduced, relative to the venturi, lessfuel makes its way up the jets, and consequently, mixture is leaner. <S> The HAC unit has two chambers separated by a diaphragm. <S> One chamber iscompletely sealed (except during calibration) and air density withinremains constant. <S> The other has airfilter, float bowl, and venturiconnections, so air density on this side is variable. <S> It is in thischamber, that ambient pressure can be reduced by feeding it to theventuri via a connection on late model carburetors. <S> The amount ofambient reduction is controlled by a tapered needle which changesposition with deflection of the diaphragm. <S> Think of the diaphragm as aflexible wall between two chambers that allows the sealed side toexpand or contract as changes in ambient pressure occur on the otherside. <S> The reduced (from ambient) pressure gets routed to the floatbowl(s) via their vent lines with a resulting leaning affect.. <S> Ifthat supply of low pressure is shut off, float bowl pressure returnsto ambient, and the mixture goes as rich as the jets will allow. <S> WithHAC installations, standard jetting starts out several steps richer. <S> This is why we say the default, or failure mode is typically towardthe rich side. <A> The simple answer to this, is that Rotax employs Constant Depression carburetors, which is a type of Variable-Venturi carburetor . <S> In essence the fuel/air ratio is adjusted automatically based on air pressure. <S> The fuel jet opening is varied by a tapered needles that slides inside the fuel jet and is controlled by a vacuum operated piston. <A> The inputs are received by the EEC and analyzed up to 70 times per second. <S> Engine operating parameters such as fuel flow, stator vane position, bleed valve position, and others are computed from this data and applied as appropriate.
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Some new Rotax engines, such as the 912 iS , are fuel-injected and include a Full Authority Digital Engine Control (FADEC) : FADEC works by receiving multiple input variables of the current flight condition including air density, throttle lever position, engine temperatures, engine pressures, and many other parameters.
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Why are student pilots' shirt tails cut after they complete their first solo? There's a standing tradition, at least in the USA, that a student pilot has their shirt cut, signed and dated by their instructor. What is the origin of this practice and what is its significance? <Q> Supposedly , this is because in the early days of flight before intercoms were common instructors used to sit behind their students in a tandem aircraft and pull on their shirt tails to give directions. <S> After successfully soloing, the student has shown that he doesn't need that direction any more and therefore doesn't need his shirt in one piece either. <S> This isn't a universal tradition: I had the end of my tie cut off to mark my first solo (in South Africa). <S> I had to go out and buy a tie first! <A> As a young pup hanging around the city's airport, this seemed quite the oddity. <S> Seeking council from a very senior pilot, he acknowledged the following details concerning the habit of cutting off a solo student pilot's shirt tail. <S> "Back in the days of the barnstormers, the aircraft of the time (Jennys, mostly), did not have all the modern electronics that we have today. <S> Most importantly, the radio was not yet available in aviation. <S> So when a flight instructor felt that a student's airmanship was solid enough (would not reasonably crash the aircraft), it became incumbent upon the instructor to tie a rag on the aircraft, sometimes the tail wheel or wing struts of the aircraft, as a visual method to WARN other pilots that THIS aircraft was being flown by a student pilot... someone who was VERY inexperienced in the art of flying by himself, and to give him wide berth. <S> As such, finding a rag on the open airfield to be used for such purposes was a rarity. <S> So? <S> The instructing pilot would whip out his pocketknife and cut of the tail of his flying pupil's shirt which would then be attached to the aircraft." <S> His explanation made perfect sense... thought I'd pass it along. <A> Several traditions have developed in the USA around "soloing", including drenching the student with water and cutting off and permanently displaying the back of his or her shirt. <S> In the days of tandem trainers, the student sat in the front seat, with the instructor behind. <S> As there were often no radios in these early days of aviation, the instructor would tug on the student pilot's shirttail to get his attention, and then yell in his ear. <S> A successful first solo flight is an indication that the student can fly without the instructor ("instructor-less" flight). <S> Hence, there is no longer a need for the shirt tail, and it is cut off by the (often) proud instructor, and sometimes displayed as a trophy.
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In American aviation lore, the traditional removal of a new pilot's shirt tail is a sign of the instructor's new confidence in his student after successful completion of the first solo flight.
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Where can Boeing wind data be found? There are various services that use world-wide Boeing Winds for forecast wind data which can be used to calculate an approximate flight time between two locations. They usually have best case, worst case, and average case for each location, altitude, and date in the future. I have searched and searched Google to no avail. Where can this wind data be found, and how can it be used in a commercial product? For those of you who don't know what the Boeing winds are, I found this description of their software product on am informal message board (not related to Boeing): PC WindTemp INTRODUCTION The Boeing PC Windtemp program provides global average and statistical winds and temperatures aloft over a 30 year period. These data are used primarily for comparative transport airplane performance and economic studies. The data may also be used for transport airplane route planning on an annual, seasonal, or monthly basis. Note: Actual winds and temperatures at a specific location and time may differ appreciably from those computed by PC Windtemp. Therefore, data from PC Windtemp must not be used for flight planning, aircraft dispatch, airborne flight navigation, or any other type of actual flight operations. PROGRAM FEATURES A seasonal and monthly database with global coverage from 1000 millibars (364 feet pressure altitude) to 10 millibars (101,885 feet pressure altitude). Annual data updates to the most recent 30 year period. Airport codes and coordinates may be imported from a text file in a comma separated value (CSV) format Calculates enroute wind and temperature for up to 50 airport pairs at a time. Calculates enroute wind and temperature for simple great circle tracks or tracks with up to 250 waypoints, with or without altitude changes. Calculates average enroute wind and temperature or any reliability (quantile) between 50% and 99%. Months or seasons, reliabilities, altitudes, and speeds may be nested for input efficiency. Formatted and text output reports are available. Program subroutines (DLLs) can be called from other programs written with C++ or Visual Basic in order to incorporate Windtemp functionality in those programs. <Q> One such project is the NCEP/NCAR Reanalysis Project . <S> There are a few others, as well as archived data. <S> None of these is exactly the Boeing dataset, but I'd bet that the Boeing dataset is based at least in part upon data like these. <S> The benefit to the data below is that in most cases it is free and there is a lot of it. <S> Reanalysis Data Reanalysis data is constructed from the best available past observations, which are assimilated into a weather model to fill in the gaps between obs and in time. <S> There are many such projects with various scales (global, regional) and time periods. <S> The NCEP/NCAR Reanalysis Project <S> This dataset has 4-times-daily, daily and monthly values between 1948 and present and long term monthly means for 1981-2010. <S> The data is global. <S> The data is publicly available and you can retrieve files in NetCDF format from the linked website. <S> The wind data is stored on pressure levels (e.g. 1000 mb, 500 mb, 250 mb) and is stored in its u (east-west) and v (north-south) components separately. <S> The <S> ERA40 <S> This dataset is a global dataset covering 1957-2002 and has various output resolutions available. <S> Output from ECMWF is typically in the GRIB format and not all of it is free for non-research use. <S> The NARR <S> The North American Regional Reanalysis, as the name suggests, is a regional dataset covering North America. <S> The data covers 1979 - present. <S> Observations Long term past observations are archived at the NCDC and include surface stations, weather balloons and model data, among others. <S> From the various models available a statistical representation of winds could feasibly be produced. <A> The wind data that Jeppesen/Boeing uses is proprietary, they have their own meteorologists. <S> Similar data is available from NOAA . <S> They have a data server that can provide wind information. <A> Usually inside the dispatch document, you will have a list with all enroute fixes, like this: FIX FREQ <S> AWY <S> WIND <S> COORDS--------------------------------------- <S> VKZ 123.45 <S> UN857 235/60º W... <S> S... <S> Usually airlines have their own system to deal with that, but search about lufthansa's LIDO, they can provide this information for you, click here to understand a little bit more. <S> And as said by Jim, all data is provided by NOAA via winds aloft charts, you can find it here , section "Wind and Temperature".
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An alternative to the Boeing data (if it exists, you might need to call one of their sales reps to find it) is publicly available meteorological data.
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What are the requirements to take the private pilot check ride? In the US, what are the requirements that a student pilot must demonstrate to their examiner before they can take a checkride for their private pilot airplane certificate? <Q> Private Pilot Airplane Single-Engine Checkride Requirements <S> Instructor logbook endorsement certifying your flight proficiency ( 14 CFR 61.107 )and that you are ready for the flight test <S> Log all required aeronautical experience (below) <S> Aeronautical Experience ( 14 CFR 61.109 ): 40 hours of flight time (35 for 141 schools) that includes: 20 hours of dual instruction 10 hours of solo flight training <S> 3 hours of cross-country dual 3 hours of night dual (to get an unrestricted license) <S> that includes: 1 cross-country flight of over 100 nautical miles total distance 10 takeoffs and 10 landings to a full stop (with each landing involving a flight in the traffic pattern) at an airport <S> 3 hours of instrument dual <S> 3 hours of dual in preparation for the practical test within 2 calendar months 10 hours of solo including 5 hours of cross-country time 1 150 NM solo cross country flight, with full-stop landings at three points and one segment of the flight consisting of a straight-line distance of more than 50 NM between the takeoff and landing locations 3 takeoffs and 3 landings to a full stop (with each landing involving a flight in the traffic pattern) at an airport with an operating control tower <A> I'm sure someone will post the exact regs, but as a stop-gap, from memory: 40 hours (35 if the school is part 141) minimum total time <S> 20 hours dual instruction <S> 3 hours flight "by reference to instruments" (under the hood) 5 hours solo cross country ( <S> 50nm minimum between two points along each trip) <S> One solo 150nm XC flight with at least 3 airports <S> (two of which must be at least 50nm apart) <S> 3 hours night flight (dual instruction) <S> One night XC (dual) 10 night landings (full stop) <S> 3 hours of dual instruction explicitly for check ride prep, within 90 days of the check ride <S> Endorsements for the items above needing endorsements An endorsement from a CFI stating the candidate is prepared for the check ride. <S> Additionally, mine has a statement that my (part 61) CFI had seen my US passport (and its number) establishing proof that I am a US citizen, in accordance with 49 CFR 1552.3(A). <A> Mah explained everything very well. <S> Be able to read, speak, write and understand the English language <S> Obtain at least a third class medical certificate from an Aviation Medical Examiner Pass a paper/computerized aeronautical knowledge test <S> Pass an oral test and flight test administered by an FAA inspector, FAA-designated examiner, or authorized check instructor <S> Source: Wikipedia <A> Regulations are somewhat different for different aircraft (airplane, helicopter, glider, etc). <S> I'll assume the question asks about private pilot for single-engine land-based aircraft (SEL). <S> For the United States, answer can be found in FAR §61 subpart E. Applicable sections are: 103(a),(c)-(j), 105, 107(a),(b)(1), 109(a). <S> Reference: <S> FAR §61, Subpart E Disclaimer: not a lawyer, just a humble student pilot navigating this gauntlet himself :-).
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Eligibility Requirements ( 14 CFR 61.103 ) Be at least 17 years of age for a rating in other than a glider or balloon Be able to read, speak, write, and understand the English language Instructor logbook endorsement certifying your aeronautical knowledge ( 14 CFR 61.105 ) and that you are prepared for the written test Passed the written test and can present your original embossed Airman Knowledge Test Report The non-flying requirements are: Be at least 17 years old (14 years old for glider or balloon rating)
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For large jets, what is the primary means of slowing down after landing? I understand that a large(r) commercial jet slows down after landing using the following methods: Wheel brakes Reverse thrust Spoilers/flaps/airbrakes What is the effectiveness of each compared to the others? What if one of the first 2 fails? Can an airliner usually be stopped without using wheel brakes or without using reverse thrust? And what if the runway is slick because of rain, snow or ice? Does that change the equation? <Q> The brakes are much more effective than anything else, at least for the jet I have experience in (EMB-145). <S> Our landing performance data typically assumes full braking application, spoilers deployed and no reverse thrust. <S> The airplane will most certainly stop without using reverse thrust, just not as fast. <S> I never tried not using the brakes, and if I were to I would want a light airplane and a very long runway. <S> As Lnafziger pointed out in the comments, the brakes are part of redundant systems so that they are always available. <S> In the EMB-145, the brakes were serviced by two independent* hydraulic systems. <S> The inboard brakes were on one system while the outboards were on the other for a total of four wheels each with big carbon fiber brakes. <S> To address the comments on slick runways, assuming braking action allows an attempt to land in the first place, you have to be careful. <S> With reverse thrust alone you may not be able to maintain the runway centerline and directional control may become difficult through uneven deployment of the reversers and other factors. <S> In this scenario the spoilers are helpful to increase traction and brake effectiveness. <S> In short, if the runway is slick then the only way I'm attempting a no-wheel-brake landing is after declaring an emergency. <S> * You could transfer fluid between our systems through the parking brake. <A> Perhaps instead of thinking of a single primary means of slowing a large jet, we should think about a primary means for a given set of conditions, the combinations of which are numerous. <S> To mention a few: What is the weight of the aircraft. <S> Passenger aircraft are typically nowhere near max landing weight when they land. <S> Freighters are often loaded such that they may be very close (or even over truth be told) to max landing weight. <S> Is the aircraft going to be on the ground a sufficient time for brakes heated to their max to cool? <S> Was the leg from which you are landing long enough to allow the brake and tire energy from the taxi and takeoff to dissipate? <S> Is where you're landing used to having to handle hot brakes and thus can be expected to have a huffer readily available to cool them and people who know how to do it? <S> Do you have a reverser locked out for maintenance. <S> Does your next departure allow for safely leaving the gear down for awhile and thus gave you more leeway on heating the brakes when you landed. <S> Just some thoughts. <A> This video on YouTube shows a 777 in certification trials, accelerating at maximum gross weight from standing start to $V_R$, then stopping with maximum brake pressure and no reverse thrust. <S> The brake discs are also ground down to the minimum thickness permitted by the maintenance manual to simulate the worst case scenario. <S> The brakes get white hot! <S> Then the plane has to taxi for 5 minutes, before having the fire department cool the brakes. <S> The test is to ensure that the brakes can handle the maximum load as certified, and secondly that the brakes do not catch on fire and incinerate the airplane. <S> If the runway is slick it just takes longer to stop. <S> Thrust reverse will help significantly in this case. <S> Thrust reverse is prohibited below a certain speed because the reverse thrust will kick up FOD which the engines may suck in, causing expen$ive damage. <S> However, in an emergency, thrust reverse will stop the plane. <A> While landing you want to reduce speed for which you need spoilers and to have more lift and drag you have the Flaps deployed than just when you touch down on runway ground spoilers are deployed. <S> If want to land with short runway length then you go for reverse thrust (nice to have in normal scenario but <S> in case of emergency it can be a life-saver). <S> Then we need wheel brakes to stop the plane. <S> Effectiveness: <S> When in air/near ground: only spoilers/Flaps and airbrake (ground spoilers) are effective to reduce speed of aircraft but not to stop it <S> Flap are required to keep the aircraft in a configuration such that you don't crash on ground <S> When on ground: you still have airbrakes/spoilers effective when aircraft speed is high but its effectiveness decreases at low speed. <S> So, are other control surfaces useless @ low speed (Flaps/Spoilers etc). <S> Reverse thrust and wheel brakes are the one you can rely on. <S> Failures: <S> All critical systems on aircraft have redundancy so the probabilty of failure is around 1e-8 /flight-hr <S> but still you never know. <S> I think you will be able to land <S> but you need more runway length in case of two fail scenario. <S> Yes, I believe you can land without wheel brakes by using reverse thrust but purpose of reverse thrust is only to reduce aircraft speed such that we land on short runway. <S> so, its not recommended to not use wheel brakes and use reverse thrust. <S> Slick runway/rain or snow on runway has same effect as it has on other land vehicles.. <S> Aircraft will take more runway length than usual. <A> plain and simple: the brakes. <S> And that's just talking about the force to slow down, not even taking into account that jet engines need a few seconds to spool up (6 or more) and <S> brakes are effective immediately (perhaps 1 s delay).
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Finally, to address the question in the title, the wheel brakes are always the primary means of slowing the airplane. Reverse thrust is much less effective than brakes.
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Is trimming aircraft to relieve pilot of applying force on control stick/Pedal still applicable? I know that historically pilots used to trim an aircraft to relieve continuous application of force during climb/cruise/descent, and at that trim tabs existed on control surfaces (elevator, ailerons, etc) which could be used to hold the position of the control surface without the pilot applying any force. But now, we don't usually have trim tabs, and with fly-by-wire systems forces have been reduced on the pilot. Does trimming do anything other than reduce pilot workload? Also: Do modern aircraft still follow this concept of trim to reduce pilot's continuous force on the flight controls? Apart from pilot workload and fuel efficiency (I know that trimming an aircraft can produce drag), what other benefits does trim offer? Without trim tabs, how is trimming accomplished? <Q> Almost all airplanes have trim (I'm fairly certain that the Wright Flyer didn't, so <S> I can't say all airplanes do), but a lot of newer designs don't use trim tabs because they are less aerodynamically efficient than alternative designs. <S> For instance, the Falcon 50 & 900 that I fly doesn't have a single trim tab on it. <S> Normally the flight controls are moved by hydraulics and a small electrical actuator is used to adjust the position of the aileron and rudder for trim purposes. <S> Pitch trim is accomplished by moving the front of the entire horizontal stabilizer in order to adjust the angle and amount of lift produced by the tail. <S> This is done so that the elevator can be neutralized and not create the additional drag caused by being in the airflow. <S> On FBW airplanes, they may or may not have manual trim that is used (under normal circumstances) by the pilot. <S> Trimming is still taking place on FBW airplanes without manual trim, but it is simply automated. <S> Boeing typically designs their FBW airplanes so that they behave like a "normal" airplane, and require the pilot to trim in order to relieve the control forces. <S> This is all completely artificial though, programmed simply to give feedback to the pilot. <S> Airbus on the other hand doesn't give any feedback to the pilot through the side stick <S> so there are no control forces to relieve. <S> When you release the side stick, it centers and the aircraft maintains its current pitch and bank angle. <S> In this case, the autopilot automatically trims the airplane for the current conditions, and the pilot doesn't need to worry about it. <A> Trims function is to balance the downward directed lift from the horizontal stab against the upward directed lift from the wing. <S> Obviously, the lift generated by the wing varies with airspeed, and as a consequence we trim for an airspeed. <S> The other consequence is we trim for 0 control column/stick deflection, that is to say the balance of forces we trim for assumes no control input. <S> We do this for stability. <S> The perception we get from that is that we trim to reduce control forces, and while that conclusion is true, I argue that it is a consequence to what we are really doing. <S> With that said, the control column force reduction is absolutely essential, particularly when flying a high performance airplane capable of a wide range of speeds. <S> The trim won't have an impact on control forces in this case, but will adjust the need for deflection of the stick just as in a traditional control column or stick. <S> For larger airplanes without a trim tab, the horizontal stabilizer becomes a horizontal stabilator in which the entire horizontal surface moves. <S> The whole surface rotates to change its angle of attack and the associated change in lift is how trim is accomplished. <S> For the other trims (aileron and rudder) in larger airplanes these can be implemented in the hydraulic actuators that actually move those control surfaces. <S> These would cause a constant offset deflection from the control input. <A> In reference to item 1 of the question, it's not only to reduce the pilot's continuous force on the flight controls but also that of the autopilot. <S> For example, you're straight and level with the autopilot holding altitude, and as the flight progresses your center of gravity is moving forward due to fuel burn. <S> The autopilot compensates with an up-elevator force. <S> On 747-100s -200s there's a gauge that shows you how much up-elevator the autopilot is commanding. <S> So, if you're about to disengage the autopilot, you'd best glance down at that gauge to anticipate the control force you're going to need. <S> If you're in cruise, you may still want to keep an eye on it and add appropriate trim manually to save a little fuel. <S> If you're lazy, you can ignore it, and when the up-elevator requirement reaches a certain point, the autopilot will trim it out. <A> Trim still exists on new airplanes. <S> I don't know where you got the idea that planes don't have trim tabs, or that FBW eliminated this. <S> Any sources or evidence to support your claim? <S> ( This article describes the trim of the 787) <A> Yes, trim still exists, it's a really useful feature! <S> Imagine flying from New York to London while gently pulling at the column for 6 hours in order for the aeroplane to maintain its flight path, that would be most inconvenient. <S> Trim tabs were/are used back in the days when aeroforces provided the feel forces for the pilot, nowadays the planes are too fast and big and irreversible hydraulic actuators move the control surfaces. <S> This means that feel must now be produced by mechanical springs and dampers. <S> And this arrangement also provides a convenient way to introduce trim: just adjust the neutral point of the feel spring. <S> Picture the feel spring with the stick attached to one end, and the other end is connected to the aircraft structure via an adjustable screw-jack. <S> Push the trim button, and the jack starts to turn - a nut on its shaft shifts until the feel spring is not extended anymore.
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For FBW systems, the need to balance the lift on the trim and wing is still necessary and so the need for trim still exists.
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During a takeoff emergency, is it safer to abort or continue the takeoff if either can be done within the available runway? In a multi-engine airplane, if an engine failure occurs at the exact moment that a decision needs to be made to reject or continue the takeoff, and there is plenty of runway available to do either, which one is statistically safer? A more technical way to ask the same question would be: When there is sufficient runway available, is it better to artificially increase $V_1$ (via an assumed temperature takeoff or similar approved procedure) in order to stay on the runway longer in case an abort is required, or would it be better to leave $V_1$ at the lower speed and take any problems into the air? <Q> In my experience, admittedly dated (retired 1999) whether it's 'better' or not didn't enter into the consideration. <S> A reduced-power assumed-temperature was always used (unless there was something that prohibited it) because of the cost factor, and the power reduction used was always such that there was the proper amount of runway but not 'plenty' of runway. <S> There was a maximum amount of reduction above which you could not legally go, but that was rarely used in my experience. <S> All that said, <S> it's the captain's airplane. <S> While I was a 747 f.o., I occasionally saw captains use less than the power reduction called for. <S> More often, but still not a lot, I saw captains simply call for a max power takeoff rather fussing with adjusting the reduced power. <S> Max power takeoffs were always entered into the aircraft maintenance log because it was required to do one every so often. <S> I forget the exact requirement.. <S> When I was a captain, I almost always observed the recommended reduced power. <S> Twice doing this it became a closer thing than I would have liked. <S> The first time was on the reef runway at Honolulu. <S> We were over 800,000 lbs, it was my leg, and we lifted off at the very end. <S> I rotated a couple of knots or so early because the end seemed to be getting very close. <S> I thought a lot about that takeoff and discussed it with a number of people. <S> My view, and I think the consensus view was: beware of high-humidity reduced power takeoffs. <S> Humid air is less dense than dry air, but the performance charts (at least the ones we used) didn't take that into account. <S> A year or so later at Dhahran, Saudi Arabia, we were bringing a full load of troops back from Desert Storm. <S> Reduced power was called for, the humidity was very high, and it was the f.o.s leg. <S> A little over half way down the runway <S> I didn't like how it was looking, and called for max power. <S> Discussing it later with the f.o. and the f.e., we had all come to the same conclusion at about the same time. <S> I had simply been the first to verbalize. <A> The best answer I can provide is it depends . <S> For all other emergencies including engine failure and/or fire, I would takeoff. <S> That is how I briefed my FO when I was a captain and similar to how my captains briefed me when I was an FO. <S> The most common verbiage other captains used was "I'll abort after $V_1$ for failure to fly", and I consider the specific scenarios I mention to meet that criteria for the EMB-145. <S> I'll also explicitly say that I consider the aborts I listed to be safer than to takeoff: flight controls - for obvious reasons <S> trim runaways - an out of trim transport category airplane can be a beast to fly pitch <S> trim fail - in the EMB-145 <S> a re-trim from "8 up" to <S> "6 up" has to happen at pretty slow airspeeds after takeoff or the aerodynamic forces on the stab will overcome the trim motor. <S> full hydraulic failure <S> - we did it in the sim <S> and it is a two person job to manhandle the controls, not particularly fun. <S> windshear indication - low and slow and performance decreasing <S> windshear means you'll probably be back on the ground anyway. <S> I would consider aborting, given a long enough runway, to be safer than taking off for these scenarios. <A> Well, since you are asking about 'statistically' : <S> I have a Boeing presentation entitled 'V1 and the Go / <S> No <S> Go Decision' from 2002 <S> In there it presents the case of Rejected TakeOffs and Overruns out of an estimated 76,000 RTOs studied between 1958 and 1990 about 74 ended in Overruns . <S> 56% of them were initiated after V1 (most of them >120kts), and also 56% of them were avoidable completely by continuing the takeoff. <S> This puts your statistical chances of a mishap about 0.1% in case of RTO before V1 and about 56% after. <S> If you think you have a better chance in the air, take the flight. <A> In light airplanes, if you have runway remaining, landing is the preferred choice even once you've taken off. <S> It's not a "ground reject or continue" choice. <S> It's a 3 stage process. <S> Can I reject safely on the ground? <S> After that point, Can I now land safely in the remaining distance (or even have a survivable runoff, which you may choose if you know your particular airplane can't climb on remaining engines) After that, I'm committed to lost engine procedures and attempting to fly (in some configurations, sustained flight is not possible and you're actually committing to an off airport landing)
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For an emergency involving flight controls, trim runaways, pitch trim fail, full hydraulic failure, or a windshear indication, if the remaining runway was what I knew I could land and rollout on, I would abort the takeoff.
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Where can I get the FAA data that defines airspace, including MOAs etc.? I was looking at http://www.gelib.com/aeronautical-charts-united-states.htm , where you can download shape files for Google Earth that show US airspaces. I'm writing some software that has a similar need and need to find a source for this data. I'm looking for data that defines the extents of airspaces including MOAs, restricted areas, etc. I have been pouring through the FAA's website with no luck. The link I referenced above says its source was the National Aeronautical Charting Office (NACO), which I'm having very little luck finding as well. I think it may have been renamed, thus the poor results. I also called the FAA and can't seem to find anyone there that knows where to transfer me. So, does anyone here have any helpful pointers on finding said information? I want to pull it directly from the source to make sure it is always up-to-date and accurate. <Q> Take a look at the National Flight Data Center . <S> The data appears to be contained in NASR . <S> I mentioned in my comment that there may be no official source for spatial data, but I think this may include what you are looking for. <S> These are derived products. <S> The cannonical definitions are the legal descriptions found in FAA Orders with the prefix 7400. <S> At the time of this writing, order 7400.9Z covered airspace classes A,B,C,D and E as well as reporting points. <S> 7400.8X covered special use airspaces. <S> Both publications can be found at the FAA's Website . <S> 7400.9Z superseded 7400.9Y. <S> These are published yearly. <S> I'm not sure what will come after .9Z. <A> They have a number of digital products, which should have the data that you are looking for. <S> If not, their contact information is: Customer Service: (800) <S> 626-3677 <S> 9-AMC-Aerochart@faa.gov Abigail "Abby" Smith, Director FAA, <S> AeroNav Products AJV-3 <S> 1305 <S> East-West Hwy Silver Spring, MD 20910 (301) 427-5000 <A> You may take a look at openAIP . <S> It contains nearly up-to-date airspace and airport information besides other aviation topics. <S> Airspace data is available for download as .aip file. <S> This is actually a very simple XML file that can easily be used in any application. <A> This includes the digital vector copies of the sectionals and shape files for the airspaces. <A> FAA's Coded Instrument Flight Procedures . <S> Data elements included are: Airports and Heliports, Runways, VHF, NDB and ILS Navigation Aids, Waypoints (Terminal and Enroute), Airways, Off Route Obstruction Clearance Altitude (OROCA) <S> records, Departure Procedures (DPs), Standard Terminal Arrival Procedures (STARs), Special Use Airspace (SUAs) and Class B, C, and D Airspace. <S> Also included are GPS, RNAV (GPS), RNAV (RNP), GPS Overlay, ILS, LOC, LDA and SDF Standard Instrument Approach Procedures (SIAPs) with their associated Minimum Safe Altitude (MSA) data. <S> SUAs most likely includes MOAs. <S> It's encoded in ARINC 424. <S> The specification is not free but can be found using a search engine.
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You are looking for Aeronautical Navigation Products ( AeroNav Products ) (formerly NACO). The current information can be downloaded at: https://nfdc.faa.gov/xwiki/bin/view/NFDC/56+Day+NASR+Subscription
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Why is "dragging it in" considered bad in small aircraft, but fine in larger aircraft? In larger aircraft, shallow, high-power approaches are performed as a matter of routine, but in light aircraft it seems to be frowned upon, especially in clear weather and smooth fields. Why is "dragging it in" considered bad in small aircraft? <Q> For the GA fleet, there is some historical precedent operating here. <S> Years ago, engines were much less reliable than they are today. <S> Dragging it in generally means that you cannot glide it in if you have a complete power failure. <S> This translates to saying in the event of an engine failure <S> , you are landing off airport with limited selection of landing sites (your altitude is low as you are now below pattern altitude). <S> So if you are flying behind an old Curtis OX-5 in your Jenny, a gliding approach to landing was recommended back in the day. <S> Engines are much more reliable today. <S> After an analysis of landing accidents, the FAA determined that a stabilized approach to landing is less likely to result in an accident, and they changed their guidance accordingly. <S> Stabilized approaches are partial power-on landings. <S> Some old timers and some old time CFIs reject the FAA's statistical analysis and still teach/fly glide-it-in landings. <S> Properly executed, both approaches to landing are safe. <S> It is just that the FAA thinks that stabilized approaches are safer given engines commonly in use today. <S> It is also true that virtually all airlines require stabilized approaches in their operating specs, and that a go around is mandatory if the approach is not stabilized. <S> With this in mind, flight schools that aspire to send their graduates to the majors will all teach stabilized approaches. <A> This is less of a "big -vs- small" question, and more of a "single-engine -vs- multi-engine" question. <S> So, to answer your question with another question: What would happen if an engine were to fail during the approach in each case? <S> You want to be careful not to take this concept too far though. <S> See: <S> Short approach vs Normal <S> Also, in jet aircraft the power needs to be kept relatively high so that additional power is available quickly if needed since the engines take awhile to accelerate. <S> See: <S> Why do turbine engines take so long to spool up? <S> Partially because of this, the idea of a stabilized approach was widely incorporated. <S> This requires that the aircraft is in a stable, continuous rate descent to the runway and that the approach be abandoned if not within required parameters at a specified minimum altitude. <S> A secondary reason is that "larger" aircraft are commonly flying instrument approaches to help transition from the enroute/terminal phase of flight to the runway. <S> These standard procedures are designed for use in instrument conditions and allow plenty of time to safely configure for a stabilized landing. <S> Even in visual conditions, they are commonly used when there is a lot of traffic to "put everybody in line". <S> Even a small single-engine airplane will probably be further from the runway than they like at big airports, just because of the amount of other traffic. <A> Actually a power on stabilized approach makes sense. <S> Being close the runway in case power fails does not. <S> Else you would never leave the pattern! <S> After a cross country wherein my engine has been running just fine <S> , why would it all of a sudden be an issue when I land? <S> Now if you do have issues, carb ice, oil tempt, etc, I understand the safety margin. <S> Also it is Good for “off field” engine out practice. <S> So I do both, in the Citabria I glide it in from downwind abreast the numbers. <S> Skyhawk SP <S> I do a power assisted approach. <S> Mostly because that is what you do in IFR flying, it’s good practice even when vfr. <S> That is the main reason big guys power it in. <S> Same procedure every time regardless of external conditions builds consistency and kiss! <S> Also turbine engines are extremely reliable! <S> Remember, no matter what you choose, a stabilized approach after a stable pattern is the foundation of good to great landings. <S> I am not a cfi, so this is merely my experience not instruction!
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In a single-engine aircraft you want to always be in a position to land if the engine fails, so you don't want to get too far from the runway, while in a multi-engine aircraft you can continue the approach if an engine fails.
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What is the difference between a crabbed and de-crab landing? Both landings are done when an airplane's nose is not in inline with the runway. How are these two different? when should one technique be preferred over other? <Q> Consider where the center of gravity is in relation to the main wheels. <S> If you are in a tail dragger, you definitely would prefer to de-crab (never heard that term before now) before touching down. <S> If you touched down while crabbed, you'd have a moment created by the center of gravity around the main gear to ground loop the airplane. <S> In a tricycle gear airplane, that same moment would work to straighten the airplane since the center of gravity is forward of the main gear. <S> In a crosswind from the right, for example, when you apply left rudder to align the aircraft with the runway, the right wing will want to come up (you just gave it a little extra speed), so you will want to use right aileron to at least counter that as you certainly don't want the crosswind component to get 'under' the wing. <S> Both 747 operators I flew for recommended touching down in the crab. <S> Personally I didn't like that and used a combination approach in a heavy crosswind, take out some of the crab but not all. <S> Also, while they did caution against lowering the upwind wing, I always lowered the wing a little. <S> I once figured out how much the wing would have to be lowered before ground contact, and it was quite substantial, more than I would ever think of using. <S> Also, as I remember, It would not be the wingtip or an outboard engine pod that would make first contact, but rather the outboard corner of the outboard wing flap when set to flaps 30. <S> Finally, when your touch down speed is 140 knots, for example, you'll have to crab much less for a given crosswind component than if your touchdown speed is 70 knots. <S> Cosine or tangent of the angle, I forget which. <A> Wikipedia's definitions are a bit unclear but it seems to say that de-crabbing is where you straighten the aircraft in the air just before touchdown; crabbing is where you straighten on the runway after touchdown. <S> De-crabbing: <S> Just before the flare, opposite rudder (downwind rudder) is applied to eliminate the crab <S> Immediate upwind aileron is needed to ensure the wings remain level while rudder is needed to track center line. <S> The greater the amount of crab at touchdown, the larger the lateral deviation from the point of touchdown. <S> Personally I find these definitions odd: in my limited experience in light aircraft, a "crabbing" approach is what Wikipedia calls "de-crabbing", and "de-crabbing" is the action of straightening the aircraft in the air before touchdown. <S> I have no idea why a pilot would prefer to land the aircraft at an angle to the runway and then correct on the ground. <S> But perhaps this is normal practice in larger aircraft; I have no idea about that. <A> It also depends if you have a low or high wing airplane. <S> And if you are comfortable touching down on one wheel. <S> In my plane, A Socata TB, the plane has a monstrous rudder that has a demonstrated crosswind component of 25 knots. <S> That's demonstrated, I'll tell you it has the authority to do more but the manufacturer always errs on the side of safety. <S> It also is a low wing, so high crosswind landings get be nervous that I might scrape a wing edge. <S> To me being sideways is not normal. <S> Crabbing to the runway means that you are heading at the runway but it may not be at your nose. <S> But it is holding a steady view relative to a point on your windscreen. <S> Remember, the training if you see another plane. <S> If it's moving relative to a point on your windshield that's good. <S> If it's not and maintaining the same point, you are generally on a collision course. <S> Same with the runway numbers, if they are off to your left and the runway is coming at you, you might be pointing at the control tower but your "Ground Path" is straight down the runway. <S> I'll crab all the way down, then bleed off energy using the T-6 P-51 training I received, then just as I feel the final drop beginning, I'll add about 2 inches of MP to arrest the decent and kick out to point the nose down the runway. <S> Remember, the only time your wheels have to be straight down the runway is 1 millisecond before the rubber hits the road! <S> Also in retrospect, I assume the turn Crabbing is derived from the way a real Crab moves. <S> It walks sideways to go forward. <A> It all depends on the aircraft you are flying. <S> Some jetliners are certified to be landed with side loadings if that side loading on landing is within certain limits. <S> Some airliners like the 737 require the jet to be landed in a crab as cross controlling to keep the nose aligned with the runway centerline <S> runs the risk of scraping and damaging one of the engine nacelles on the runway. <S> Light GA aircraft are not designed to take high side loads on their landing gear and require cross control to align the jet with runway centerline during crosswind landings. <S> In an airplane fitted with conventional landing gear (tailwheel), it is imperative to land parallel to centerline with good crosswind technique as side loading creates a strong possibility on inciting a ground loop.
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Crabbing: upon touchdown the airplane tracks towards the upwind edge of the runway while de-crabbing to align with the runway.
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What is the best strategy for landing when a flock of birds is on the runway? At a controlled airport, the tower advises large flocks of small birds at the approach end of the runway. I'm in a small trainer aircraft like a Cherokee or Cessna 172. Should I request to land the other way (Rwy 9 vs 27), proceed as normal but just expect them to only be a distraction? What are the best options here? <Q> I think the answer depends on what the birds are doing, but all options are basically "at the pilot's risk" - the tower is just advising you there are some birds hanging around the airport, but nobody can say how they're going to react to you trying to land there too. <S> If the flock is airborne and flying across the final (completely neglecting to coordinate their movements with tower, as birds are wont to do) you can request an extended downwind until they've moved on. <S> This has happened to me twice, and in my experience birds tend to be far less interested in airports than pilots. <S> They're usually gone in a minute or two. <S> If they're sitting on the runway somewhere you can try a low pass over the field to scare them off, but my preference would be to ask the tower/unicom operator if they can chase them away for me with a ground vehicle (so I'm not near the flock in case they decide to disperse "upward" instead of "outward"). <S> If they're just pecking around in the grass near the approach end of the runway looking for lunch <S> Skip Miller & <S> p1l0t have the right idea with a go-around or low approach/overflight to scare them off. <S> (This is part of why a low pass over an unattended uncontrolled field is often advisable -- you'll hopefully scare off any critters on the runway that you wouldn't want there when you actually land.) <S> Some of the airports by me have resident flocks of birds that I'm convinced just sit there and <S> rate people's landings - I swear I saw the same birds every day shooting touch-and-gos. <S> These are the kind of birds that aren't going to scatter when you do a low pass unless you hit them with your landing gear, so just be aware of where they are (in case they lose their minds and try to commit suicide by propeller) <S> but they probably won't bother you. <S> I don't think I'd ask for a downwind landing because of birds (unless we're talking geese or hawks or something), but if it's a calm-wind day, the pattern is empty, and you're more comfortable with that idea go ahead and ask. <S> The worst the tower can do is say "unable". <A> The best option is to go around. <S> Maybe the noise of you passing overhead will scare them into the air and they will land elsewhere. <A> The biggest problem you face in a propeller aircraft when going through a flock of birds is instant IFR. <S> You don't want to do that on landing. <S> I had the experience of a flock of Canadian geese taking off as I was committed to takeoff while soloing as a student pilot. <S> It was a spectacular mess, right out of a Friday the 13th Movie (or Indiana Jones). <S> I had to fly by instruments to climb to a safe altitude then maintain straight and level. <S> Then I had to search the plane for some spare paper towels that I used to create a clear area in the windscreen so that I could see to land (reaching out the side window). <S> Thus, it is best to stay away from the birds. <S> If they take off, you can abort the landing and climb. <S> If the runway is long enough, you can land long, past the birds.
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If they're "airport birds" you might want to just land.
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Is it safe to use a parallel runway's PAPI/VASI? Many airports have parallel runways but only one runway has a PAPI/VASI. If both runways start at the same point and have similar touch-down points, is it safe to use the parallel runway's lights for the approach and landing? <Q> Per the AIM ( 2-1-2 - Visual Glideslope Indicators ) <S> The visual glide path of the PAPI typically provides safe obstruction clearance within plus or minus 10 degrees of the extended runway centerline and to 4 SM from the runway threshold. <S> (Deviations from that are supposed to be noted in the Airport/Facility Directory, for example if the clearance path is offset from the centerline, or theoretically if you could use a parallel PAPI...) <S> A few miles out you're probably within the 10 degree arc, so the PAPI will be useful, but as you get closer that arc narrows, and as Lnafziger mentioned there might be an obstacle in your way (like the FAA-Standard 50-foot tree right at the threshold line). <S> Also as abelenky pointed out you're not supposed to be using parallel PAPIs/VASIs for approach guidance - <S> It's a good cross-check, but not a primary reference. <A> Not necessarily. <S> The PAPI is installed, and the angle is set for the obstacles in the approach path for that specific runway. <A> It is considered "safe" for a pilot to use all available information to safely conduct a flight. <S> This does not exclude using other references, such as a parallel PAPI as a means to cross-check. <S> However, it is not legal to use a parallel PAPI as your primary guidance. <S> If there were to be an incident, and you were to tell an investigator, "the parallel PAPI indicated that I was on the GS", he'd think you were a bit nutty, and fault you. <S> If instead, you were able to tell him "I was properly lined up for the Left, and then cross-checked with the PAPI on the Right, which also indicated a stabilized approach on the GS", he might commend you for creative cross-checking.
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There could be obstacles on the parallel that the other PAPI would not give you clearance over because it was never surveyed for that.
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What happens when a turbo-prop is over-torqued? What does one need to do when a turboprop engine gets over-torqued? I haven't over-torqued an engine before, but it seems it could happen inadvertently, say while doing a go-around. My questions are: Why is important not to over-torque an engine? What happens if you do over-torque an engine? <Q> And that's really about all that we can tell you in general terms. <S> The manufacturer or an engine repair shop could tell you what is most likely to fail for a particular model, but the failure modes won't be consistent from engine to engine. <S> As far as what to do if you were to over torque one, refer the the aircraft flight manual. <S> They will have a limitations section, and most airplanes will have "transient" limits in addition to the "normal" limits. <S> For instance, the limitation could be 100%, with a transient limit of 103% for 10 seconds and 105% for 5 seconds. <S> If the transient limits are exceeded, then you (or more likely a mechanic on your behalf) would need to refer to the maintenance manual for instructions. <S> Depending on the severity of the exceedance, it can be anything from simply logging it in the engine logbooks to a complete tear down and overhaul of the engine. <S> I'll also add that some pilots lean towards pretending that the exceedance never happened, and hope that nobody noticed. <S> This is not a good idea for several reason, the main one being that something could have been damaged that is not immediately obvious. <S> Even though things are running correctly now doesn't mean that all is well, and if an inspection is required, it's for a reason. <S> Another issue is that a lot of modern engines are computer controlled and monitored. <S> The next time that the computer information is downloaded, maintenance will see the exceedance anyway <S> and if you have flown it since then you could be in even more trouble. <S> In short, follow the AFM procedures for your airplane. <S> They are there to help keep you safe! <A> You shouldn't over-torque an engine because you can stress parts more than they're intended to be and cause accelerated wear, or possibly damage or failure. <S> Modern turbines are designed well past their published limits though, so over-torquing does not necessarily mean anything was hurt, it depends on how far over it went, and how long it lasted. <S> If you do over torque an engine, the first step is to determine (if possible) how much the limit was exceeded. <S> What happens next is determined by how much the limit was exceeded. <S> Up to a point, nothing needs to be done. <S> After that, varying levels of inspection might be required. <S> Beyond a certain point, part replacement or rebuild/overhaul might be required. <S> What exactly happens is specific to each engine. <A> By exceeding the torque limits of the engine you rush shearing the driveshaft or damaging the propeller gearbox. <S> Not a good thing to have happen with the engine running at full power and rebuilds of these components are expensive.
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This short answer is that you could break something if you over torque the engine.
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Who decides what measurement units are used for altitude, and why is there no standard? I know that some countries (Russia and China for instance) use meters to measure altitude while the rest of the world uses feet. Why isn't this standardized around the world? I guess all modern cockpit instruments nowdays offer both unit system measurements, but this must be creating some confusion for pilots. Who decides which measurement units should be used for aircraft altitude? The airlines? ATC? Each country? Why are both units of measure used? Are there any pros or cons with using meters? <Q> Unfortunately, countries tend to want to decide themselves how stuff is supposed to work once you're within their borders. <S> That's why we have different rules and laws, and when you go somewhere else in the world, you might need to know some of the differences. <S> In England they drive on the wrong side of the road, imagine that! :) <S> In order to have things run smoothly in something so utterly international as aviation, the organization called ICAO (International Civil Aviation Organization) where most countries of the world are members, dictates the rules, (I believe they are) called the ICAO drafts recommendations which the member states should incorporate into their respective laws and regulations. <S> If they choose not to, they need to inform the ICAO of such deviation, don't know exactly what happens then, but I believe the idea is to at least let everybody know there's a discrepancy. <S> The ICAO Annex 5 specifies units to use, including units for altitude and actually specifying meters as the primary unit, with feet being accepted as non-SI alternative. <S> Why on earth you'd want to go against the majority on this <S> I don't know, perhaps due to the fact that it's an SI unit and they want to be as much SI as they can. <S> So it's basically up to each country how they want to play it. <S> Most countries stuck with feet. <A> In the US, we generally use 500ft for visual separation, and 1000ft for separating IFR traffic from other IFR. <S> This translates to roughly 150m and 300m respectively. <S> This means, we can explain IFR cruising altitudes as odd-thousands going east, and even thousands going west (up to FL410). <S> If this were in meters, you'd have to try to explain that going east <S> it's 300m multiplied by odd numbers, and west <S> it's 300m multiplied by even numbers. <S> It's certainly not impossible to figure out in your head, it just isn't as quick and easy. <S> Unfortunately 100m is considered too little separation, and 500m would be an inefficient use of airspace (over-separation), otherwise there might be more of a global push to use meters. <S> Interestingly, although Russia does use meters, they have actually adopted the international "Flight Levels" (i.e. "climb and maintain FL350" which would be equal to 10650m), so now international flights do not have to change altitude when crossing the border into Russian airspace. <S> However, I believe this is not true for other countries which use meters, such as China, where the separation is typically 300m. <A> As to feet being the best measurement for height, what utter nonsense! <S> Prior to WW2, all metric countries flew in meters. <S> That changed after WW2 with America dictating what happened on this planet. <S> Unable to convert to the metric system for one reason, big money that has so far thwarted all efforts to accomplish this important task. <S> America forced the almost 80% metric world to fly in stone-age measurements called feet. <S> Well so much for democracy! <S> Maybe China will eventually do the same and force America to go metric! <S> Sure a drastic step, but a well-deserved one!
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In response to the pros/cons of feet vs. meters, the big advantage that feet have over meters, is that it allows you to use nice human-memorable numbers for cruising altitudes.
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How does the mounting location of a jet engine affect aircraft performance? Different jet airplanes mount the engines in different ways. For example: Under the wing To the fuselage How does the engine location affect aircraft performance? Is one better than the other? <Q> Engine location performance-affecting factors: 1. <S> Mounted in the wing root low asymetric yaw on engine failure, <S> less rudder required: less drag no engine pods: less parasitic drag engines closer to CG, less downforce needed from the tail: less drag very little reverse thrust available Little space for high-bypass-ratio engines 2. <S> Mounted in pods under the wing high asymetric yaw on engine failure requires larger rudder: drag penalties engines provide bending relief on the wing, allowing better wing design (thinner wings): less drag at high incidence angles the pods can prevent spanwise flow: less drag and better stall characteristics <S> full thrust can impose a large, undesirable, pitch up moment (think stall recovery) <S> less freedom in roll on cross-wind landings Location ahead of the wing's elastic line helps to dampen flutter 3. <S> Mounted inside the tail or on pods on the rear fuselage low asymetric yaw on engine failure, less rudder required: less drag wing design is freed from the need to accomodate engines, allows for more complex wing designs: better performance throughout the flight envelope heavy engines so far aft of the fuselage <S> require wings mounted further aft, and a higher tail to support that: more drag Lower landing gear required, especially in case of short fuselages <S> That's about what I can come up from memory, maybe someone can merge all answers into a comunity wiki kinda post.. <A> Mounting jet engines above the wings (see: Antonov An 72 , Boeing YC-14 ) takes advantage of the Coandă effect to increase lift and improve short-field takeoff and landing performance. <S> The high-velocity engine exhaust (I'm hand-waving a bit here) adheres to the surface and allows the wing to produce lift somewhat longer than it could otherwise. <S> This layout also vastly reduces the amount of debris and spray that can reach the intakes and damage the engines. <A> Generally there are 3 engine placements:In the tail, on the fuselage in the back, or under the wings. <S> I'll go over the pros and cons of each. <S> On the tail Pros <S> Not many pros, except that it lets one turn a four-holer into a three-holer which is usually more efficient. <S> Cons <S> Generally if you lose the engine in the tail, you risk losing rudder control <S> and you also need a thoroughly reinforced tail, plus you have fuel lines running near the cabin, and you have a significant amount of weight not near the center of gravity. <S> Cons Fuel lines near the back of the aircraft,tail has to be a T-tail, as well as reinforced. <S> and center of gravity issues. <S> Under the wings <S> Pros <S> Well centered with the center of gravity, allows for more weight shifting in the cabin, and with the bags. <S> The fuel is also kept away from the cabin, and the noise is better spread out through the cabin. <S> In the event that something goes wrong, debris is also less likely to enter the cabin. <S> Cons <S> Much easier to get debris swept into the engine, wings have to be reinforced, lose some area for flaps and slats, raising approach speed. <S> Some useful links <S> http://adg.stanford.edu/aa241/propulsion/engineplacement.html <S> http://www.airliners.net/aviation-forums/general_aviation/read.main/750042/ Performance Wise <S> Tail: <S> Generally not the best, as it has center of gravity issues and drag problems. <S> Fuselage: Good for poor quality runways or low approach speeds but can add weight in reinforcing the tail. <S> Under the wing: Good for getting more load as less center of gravity issues, but raises approach speeds. <A> For tail side-mounted: I think there are issues with airflow to engines at certain angles, reducing stall-recovery options.
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On the fuselage in the back Pros Helps to prevent debris from entering the engine, allows for more room for flaps on the wing, and lighter, more aerodynamic wings since they are not holding up engines, generally allowing for slower approach speeds, also the thrust is closer to the center of the aircraft.
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How do conventional and T-tails differ? What design considerations go into the decision between conventional tails and T-tails? Functionally the horizontal stabilizer/stabilator are the same in both cases, providing negative lift, the elevator control and a method for pitch trim. What are the differences though? As far as I am aware the T-tails I have flown have T-tails for avoiding propwash (PA-44) or aft engine placement (EMB-145). Are there other reasons for having a T-tail? What are the aerodynamic consequences a pilot needs to be aware of with a T-tail (e.g. avoiding hard de-rotation on touchdown, issues at high AOA, etc)? <Q> There is more to a T-tail than that: <S> Aerodynamics: <S> The placement on top of the vertical gives it more leverage,especially with a swept tail. <S> Depending on wing location, it stays in undisturbed flow in a stall. <S> Note: This is really depending on the details, <S> the HFB-320 had a forward swept wing and a T-tail, which made a deep stall possible (and in one case fatal). <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> It can help to increase the effectiveness of the vertical tail by keeping the air on both sides of it separated. <S> At the other end, the fuselage does this already, so moving the horizontal tail up does not hurt so much there. <S> As a consequence, the tail can be built lower. <S> Structure: <S> The mass of the horizontal tail on a long lever arm (= the vertical tail) means that the torsional eigenfrequency of the fuselage will go down. <S> This might be a problem in case of flutter. <S> As a consequence of the smaller vertical tail, a T-tail can be lighter. <S> Note that the increased leverage means that the horizontal tail can be smaller as well. <S> This reduces friction drag and is the main reason why most modern gliders have T-tails. <S> Control: <S> A T-tail produces a strong nose-down pitching moment in sideslip. <S> If it were not for the flutter and pitch-down, T-tails would be more widespread ... <A> There's a lot to this, and I'm no aircraft engineer, so if there are any other answers, I'll happily delete this. <S> Anyway, from what I've been told: The T-tail sticks the elevators out of the disturbed air of the wings, prop, and (usually most of) the fuselage which gives you better elevator authority, and makes a tail stall less likely. <S> It has some drawbacks though, by putting the elevators directly in the (turbulent) separated flow from the wings during a stall <S> can put you in a (more or less) unrecoverable deep stall . <S> (Picture from the linked Wikipedia article) <A> The considerations in the roe's answer are entirely correct but there might be other factors to take into account. <S> First, it is true that using conventional tail leads to the fact that the airflow over the tail might be disturbed by the main wing and/or the engines and/or the fuselage. <S> However, the downwash induced by the main wing on the flow is taken into account (for the cruise conditions) in the design of the tail in order to reduce some negative aspects of the interaction between the main wing and the tail. <S> Another major difference between these two configurations concerns the stability. <S> As I already explained in this answer , the tail is used to create some lift that is required to fulfil the trim relations. <S> Assuming that you have the same amount of lift generated by the both configurations (this is relevant due to the "vertical" force equilibrium), a quick sketch will convince you that both the angle and the lever arm are different. <S> The conclusion of this study cannot be drawn without a specific example <S> but I hope it is clear for you that stability is really impacted by the choice of the tail. <S> From a structural point of view, when flying transonic (or even supersonic) it is not good to have a T-tail configuration because it usually induces flutter on the tail. <A> A T-tail has structural and aerodynamic design consequences. <S> The structural considerations are of course the increased weight of the vertical tail due to now having to support the forces and moments on the horizontal tail, including strengthening for flutter. <S> The vertical tail can be shorter due to the end plate effect of the horizontal tail, and the moment arm to the CoG <S> is longer - however for most higher subsonic speed aircraft these effects merely reduce the weight penalty. <S> The T-tail stays out of ground effect for longer than the main wing. <S> Upon approaching the ground, the increase in wing lift causes an auto-flare: the aircraft lands itself. <S> From the wikipedia page of the Handley Page Victor: One unusual flight characteristic of the early Victor was its self-landing capability; once lined up with the runway, the aircraft would naturally flare as the wing entered into ground effect while the tail continued to sink, giving a cushioned landing without any command or intervention by the pilot. <S> The aerodynamic consequences of a T-tail have most to do with stability and control in stall and post-stall behaviour, and can be grave. <S> The Fokker 28 and F100 had stick pushers that acted upon detecting a high angle of attack, making it pretty much impossible to keep the columns at aft position. <S> The reason for this is the reversal of the $C_M$ - $\alpha$ slope of T-tails, as depicted below. <S> Graph A is for a tail height of 2 * MAC Graph B for 1 * MAC Graph C for same height as MAC <S> The aeroplane is aerodynamically stable when the $C_M$ - $\alpha$ slope is negative, such as in cases B and C. <S> For configuration A, the slope becomes positive after the stall point, meaning that the nose wants to increase upwards after reaching the stall - not a good situation. <S> The stall speed must be demonstrated during certification, and safe recovery from a stall is a requirement. <S> A stick pusher prevents the aeroplane from entering the deep stall area.
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Finally, at a lower level but still a difference, using a T-tail increases the wake (compared to a conventional configuration, where the tail is almost in the wake of the main wings and the fuselage) behind your aircraft and thus the drag you need to overcome is larger. Regarding the "vertical" force equilibrium equation, there is no real difference between the two configurations but there is a big one for the moment equilibrium.
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Why do commercial flights turn / bank so sharply? When I take commercial flights, or you see turns in the vapour trails, they turn very sharply. What's the reason for this - wouldn't it be more efficient to turn gradually? <Q> Airplanes are expected by air traffic control to turn at a "standard rate of turn" which is 3 degrees per second. <S> This will provide a 90 degree turn in 30 seconds. <S> A standard rate is used so that controllers can anticipate how long it takes for an airplane to turn to a heading <S> and they can line them up easier. <S> It also makes the turn happen in a smaller amount of airspace so that two airplanes can be flying in the same general vicinity without getting too close. <S> Unfortunately, at the speeds that jet airplanes travel this would mean a very high angle of bank. <S> A standard rate turn at 200 KT TAS is about 30 degrees of bank and jets can go much faster than this, which would require even higher bank angles. <S> They actually limit it to 25 degrees of bank when using a flight director, mainly for passenger comfort. <S> It can be impressive when looking out the window and seeing the ground, but don't worry, the airplane is more than designed for it! <S> This is used mainly at lower altitudes where there are lots of airplanes. <S> Once they are up high and airplanes are further apart (and the turns are also usually smaller) <S> they can bank even less (by using a "half-bank" mode) which adds to passenger comfort. <A> Airliners actually turn relatively slowly, but are often so far away (when viewed from the ground) that they appear to be turning sharply. <S> An airliner cruising at 35,000 feet is actually over 7 miles away, which makes scale hard to comprehend. <S> From the air, riding in an airliner, you may be confusing rate of turn with roll rate or angle of bank . <S> An airliner will roll relatively smoothly into a bank angle of up to 30° (which can seem steep), and a rate of turn (change in compass heading) of between 3° and 1.5° per second. <S> You often don't feel the roll, but will observe the bank by looking out the window. <S> Rate of turn is standardized , making that possible. <A> Most aircraft tend to make standard rate two-minute turns, as in it would take them two minutes to turn 360 degrees (3 degrees per second). <S> At higher altitudes and higher speeds (or heavier aircraft) they might do half-rate (four minute) turns, which are 1.5 degrees per second. <S> So at a higher speed (which high-flying planes are likely to be at), to turn a the same rate, they must bank more sharply. <S> That's why at higher speeds the halve the rate, so they can reduce the required bank angle. <S> More likely though, it's just your perspective. <S> From your position on the ground it looks like they're turning sharply but in reality it took them several miles to make the turn. <S> From your position in the plane, it's difficult to comprehend how fast you're going. <S> Finally, at higher airspeed speed sharper bank angles are required to keep the plane coordinated during a standard rate turn. <S> This means that when you turn, you feel like you're being pressed down into your seat instead of sideways out of it (like when you take a turn fast in a car).
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The reason for the 1.5-3° turn rate is so that Air Traffic Control can have some way to predict where an aircraft will be in x seconds.
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What vertical speed at touchdown makes a 'perfect' landing? Is there a general vertical speed that pilots shoot for, or is it entirely by feel/trial-and-error? <Q> Thinking in terms of G-force, the perfect force depends on what you're landing on and how long it is. <S> The various conditions I can think of offhand are: long dry runway, no wind or straight down the runway -- try for a greaser if you want, although arguably a greaser is not the safest landing. <S> cross wind -- the higher the xwind <S> the more you want a firm touchdown. <S> short runway -- firm <S> so you will have effective braking. <S> wet runway -- firm, especially if the runway has standing water. <S> The two times that I blew tires on landing was when there was standing water <S> and I didn't plant it firmly enough. <S> In the first case the tires blew before I used the brakes. <S> It was an F27 and one of our pilots was in back at a window seat. <S> He said the two right wheels never rotated at all. <S> I had touched down with a greaser on a puddle. <S> carrier -- I once checked out a Navy carrier pilot in a 182. <S> It was really hard for him to flare for a landing, since they don't do that. <S> As I remember, he said that they wanted a 4G landing impact. <A> In my experience it's feel/trial-and-error-and-error-and-error. <S> 5 feet off the runway is not a good time to be looking at your VSI. <S> Edit <S> Since you're looking at a record of your vertical speed after the fact: Lower numbers are better of course. <S> The goal is to get the rate low enough that the landing gear can absorb the impact without passing on any of the energy. <S> 60 FPM would be 1 foot/second. <S> I'm sure most landing gear would soak that up and earn you praises from your passengers. <S> I've had exactly one "squeeker" <S> - I didn't know I'd touched down until the wheels started moving. <S> Naturally, I was in a single seat airplane with no witnesses :-( <A> Are you talking the approach-to-land, or actual landing? <S> Keep in mind, when you flare, you are technically arresting a descent, so the VSI should not read much more/less than zero. <S> For a stable approach, 500-700 FPM on a 3 degree glide slope usually works out well for ILS approaches. <S> Keep in mind, all instrument approaches terminate visually, unless you are in a CAT III capable aircraft, which I do not fly.
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I would argue that the way to think of the perfect landing is not in terms of vertical speed but rather in terms of the G-forces involved.
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Can a glider make a go-around? Since gliders don't have engines, is it possible for them to go around? Are there any extra features on a glider to try to prevent that situation from happening? <Q> No. <S> A (pure) glider cannot make a go-around in the way a powered machine can. <S> The glide path can be influenced by airbrakes, flaps, chutes or slipping, but mostly those are for reducing your L/D, i.e. steepening the approach (you win again, gravity!). <S> Gaining height without updraft is only possible by converting kinetic energy (speed), and that gain is limited by the stall speed. <S> So while you can get up a few meters by pulling up from landing airspeed, you will find yourself way too high above the runway at minimum speed and hoping for the best. <S> The highly enjoyable* spectacle of a low fly-by of a glider is achieved by starting with really high (unlandable) speed which is then converted into height and shortly followed by the inevitable landing <S> **. <S> For some older (mostly wooden) gliders, even this is not a very good idea because they combine a lower V NE with lower L/D ratios, leaving you low and slow after pulling up from redline speeds. <S> In a glider, you get one chance for a smooth landing (freak thermals excluding). <S> But this is one of the most important points in training, and you get used to the concept very quickly. <S> A proper landing procedure together with brakes, flaps, etc. will bring you down safely. <S> *but not necessarily safe or recommended <S> ** <S> lest you catch a proper thermal or dynamic updraft. <A> The key to safely managing and landing a glider is energy management. <S> When coming in to land it can't be too slow and low OR too high and fast (only one factor can be adjusted by trading altitude for airspeed or vice-versa). <S> Most gliders have airbrakes or spoilers which are used to bleed off excess energy. <S> A typical approach will have them deployed about half way when on final to land so that they can be used like a throttle in an airplane. <S> If they get low or slow, the airbrakes can be stowed in order to increase the glide ratio (just like adding power in an airplane). <S> If they get high or fast the airbrakes can be extended further and/or the glider can be slipped in order to decrease the glide ratio (just like reducing power in an airplane). <S> Other than the very high glide ratio and no engine to go around with, they land very similar too an airplane. <S> If you've never flown one, I would highly recommend it. <S> Not only is it fun, it will make you a better overall pilot! <A> Yes,there is one scenario when they can. <S> At our club we are on the top of a hill and if the ridge is working you can abort the approach close the airbrakes and run over the threshold onto the ridge. <S> In fact our low cable break briefing is land straight ahead or takeoff. <A> Here's a forced example: <S> In 2006, I asked a CFIG what he would do if the rope release failed for both the glider and the emergency release on the tow plane. <S> He suggested we try the exercise of seeing what it would take to land on tow. <S> (It turns out, it is REALLY easy to overrun the tow plane when on descent). <S> So, technically, I have 3 glider touch-and-goes logged in my logbook.
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No, a glider can't make a go around, but if they are going fast enough they can make a low pass (which looks like a go around), but that generally means that they won't be in a position to actually land even if they wanted to.
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Is there a minimum altitude for ejection seats? Is there generally a minimum altitude for ejecting in order for the sequence to function reliably (all the way to opening the chute, and slowing down to a survivable descent rate)? I've seen ejector seats test being done on the ground, don't know if there were actually test pilots in those seats though. I assume all bets are off if you're not wings level (obviously a low-level inverted ejection has a 0% chance of success). <Q> It depends on the ejection seat. <S> Modern <S> Older ejection seats had different minimums which varied from model to model. <S> On a side note, the early F-104 ejection seats required quite a bit of altitude to deploy properly, since the pilot exited through the bottom of the aircraft. <S> This was done because there was some concern that the pilot would hit the F-104's T-tail with a standard ejection seat. <S> EDIT <S> It appears that it may actually be possible to eject from an inverted aircraft. <S> According to Wikipedia (bold added for emphasis): <S> The minimal ejection altitude for ACES II seat in inverted flight is about 140 feet (43 m) above ground level at 150 KIAS. <S> While the Russian counterpart - K-36DM has the minimal ejection altitude from inverted flight of 100 feet (30 m) AGL. <S> When an aircraft is equipped with the Zvezda K-36DM ejection seat and the pilot is wearing the КО-15 protective gear, he is able to eject at airspeeds from 0 to 1,400 kilometres per hour (870 mph) and altitudes of 0 to 25 km (16 mi or about 82,000 ft). <S> The K-36DM ejection seat features drag chutes and a small shield that rises between the pilot's legs to deflect air around the pilot. <A> Pilots have successfully ejected at negative altitudes in a handful of instances, after being forced to ditch in water. <S> Documented evidence exists that pilots of the US and Indian Navies have performed this feat. <S> Also: I once read, but cannot now locate, the citation awarded a pilot of the USAF for the world record lowest altitude successful (i.e. the pilot survived) <S> emergency ejection from a stricken aircraft over land: <S> sixteen feet below ground level. <S> Apparently the young pilot was practicing with his T-33 single-engine trainer when the engine flamed out and could not be restarted. <S> The pilot observed the flat desert below, crossed by several paved roads and highways. <S> One road seemed to be completely clear of traffic, so he opted for a gear-down dead-stick landing on it, hoping to minimize damage to the aircraft. <S> He discovered only after touchdown that the paved strip was not a road at all but a flash flood drainage ditch, wide enough for the fuselage but not the wings. <S> The aircraft was seriously damaged and set on fire. <S> The damage prevented the canopy from opening, so the pilot used the ejection seat to escape burning to death. <S> He survived with minor burns, some compression damage to his spine, and two broken ankles. <A> The Martin Baker MkGRU7 and EA7 on both the A6 Intruder and on the EA6B Prowler aircraft have "zero-zero" capability, which means that the seats could be fired at zero AGL and zero airspeed. <A> Quite a few years back, about 28 to be exact <S> I worked on Mirage III service for the RAAF and one of my jobs was to fit the ejection seats after major airframe servicing. <S> Originally they were fitted with Martin Baker OM6 and these seats were zero-90 classification. <S> They were powered by cartridges, basically a big multi stage canon that shot you out of the plane. <S> This means they were able to be used at zero altitude and <S> 90 knots forward speed, the speed was purely to have enough air flow to open the chute fully but mostly to help with the removal of the canopy by blowing it backwards. <S> The canopy jettison would unlock the canopy and lift the front into the airstream, the forward motion would do the rest. <S> Later we made a modification to the seats to make them into zero/zero capability and this included fitting a rocket pack under the seat that would launch the seat to a safe height enough for the parachute to open normally. <S> In both cases the seats were capable of going through the canopy but normally the canopy would eject first except in the zero zero situation where the seat would go through the canopy. <A> It all depends upon the seat type, altitude, speed, attitude and orientation of the aircraft during the ejection process. <S> Ejection seats just provide a velocity vector in order to give the pilot enough time to clear the crippled aircraft and deploy the recovery parachute, as this USAF training film shows. <S> This results in an envelope of airspeed, altitude, and attitude in which the seat can be activated allowing for a safe recovery. <S> For a so called 'Zero-Zero' ejection seat, it allows for a safe ejection from an aircraft on the ground in level flight attitude. <S> It does NOT guarantee safe ejection from an aircraft in unusual or inverted attitudes at low altitudes or airspeeds. <S> In the Boeing ACES II ejection seat a basic guide to seat characteristics is given here. <S> I can't comment on the capabilities of the Russian seats. <S> However the Russians do have a tendancy to be excessivly boastful and colorful with a gullible western press, such as the 1989 crash of a MiG-29 at the Paris Airshow, where the press ran with a story about the K36 seats being able to safely eject at low altitudes and extreme attitudes. <S> The reality was the seat in this incident was activated outside of its safety envelope; the pilot was just lucky he wasn't killed.
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zero-zero ejection seats are designed to be usable at zero speed, zero altitude.
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How long do airliner tires last? Can this be improved? I imagine that the tires on commercial jets wear out pretty fast with all those squealing landings as the tire suddenly has to spin up from zero to the speed of landing. 2 questions: How many landings does any average commercial airliner tire last before it is discarded? Before landing, why not have a small motor assembly on the landing gear to spin up the tires to the correct speed? Surely this would avoid the degrading tire burn. The tire might last a lot longer and might even offset the cost of the motor assembly. <Q> I've heard that airliners' tires will last about 200-250 depending on how many hard landings are made. <S> I had one start cracking around the wall and just looking unsafe long before the treads ever started to wear. <S> As for the spin-up idea, it's been proposed many many times, but generally always rejected due to weight and maintenance costs. <S> However, now that fuel is by far the main expense in an airliner's trip, companies are looking for any way to reduce fuel burn. <S> As it turns out, taxiing an airliner burns quite a bit of fuel. <S> They've already started turning one engine off for long taxis, and I think that electric wheel motors will be the next big thing. <S> The motors have gotten light enough and strong enough that they are a now a viable option. <S> They can be powered by the APU or by a set of batteries (which are also now becoming light enough, see the 787 when they get the kinks worked out). <S> So when they get around to putting them on aircraft for taxiing purposes, you can bet that they'll be spun-up right before landing. <A> Although tyres can wear out "pretty fast" with numerous landings however as long as the carcass is in good condition then the tyre will go for a retread rather than be discarded. <S> So from a purely economic point of view I suspect a retread is the cheapest option rather than trying to develop elaborate systems to extend the life of the tread. <S> The other issues I can see with spin up motors is lack of space and temperatures. <S> There is very little room inside a wheel rim for any motors, they are filled with multi-plate disc brakes. <S> The brakes get very hot when braking and would be a very harsh environment for any motor. <S> So far simpler and cheaper to retread the tyre when it starts to get worn out. <A> This article would lend a number of roughly 240 landings per set of tires an A340 will complete roughly 6,000 take-offs and landings, calling for about 25 sets of replacement tires Since some aircraft tires can be remolded and to a large extent recycled they are a fairly decent part. <S> In the end of the day the tires are sacrificial by design, its simply easier and cheaper to replace tires every 240 landings than maintain some complex spin up system or use some pricey material (which may or may not exist) that wears slower. <S> In response to this half of the question Before landing, why not have a small motor assembly on the landing gear to spin up the tires to the correct speed? <S> Surely this would avoid the degrading tire burn. <S> The tire might last a lot longer and might even offset the cost of the motor assembly. <S> Take a look at this similar question but basically in short there are a few issues with pre spinning tires even if the system was viable from a weight standpoint. <S> They did some research on it back in the day and found that pre spinning does not really reduce wear significantly (more on that in the linked answer).
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Bizjet tires will last longer, and light aircraft tires will last indefinitely, depending on how gentle you are and what kind of surface you're landing on.
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Should full flaps be deployed on takeoff? Are full flaps ever used on takeoff? One flying book I read strongly discouraged anything more than quarter flaps on most planes due to the amount of drag produced. I was just wondering if there are any scenarios where full flaps might be necessary. <Q> First, you have to remember on some configurations, the lower stages of flap will mostly add drag and very little lift. <S> Sometimes that extra notch of full flaps is only there to change the camber of the wing to add a bit of a nose down attitude to help with visibility on landing. <S> Both are items you do not require on takeoff. <S> Now, when selecting flaps for take-off there are two things to consider: runway length and obstacles to clear after the runway: Runway Length <S> Generally when lowering flaps your $V_{\text{mu}}$ (the speed at which you become airborne, “minimum unstick speed”) will decrease. <S> This means a shorter runway for normal stages of flaps. <S> As you continue to add more flaps <S> your $V_{\text{mu}}$ will be lower, but because of the added drag, which decreases acceleration, it will actually take a longer distance to reach that lower $V_{\text{mu}}$. <S> There is a sweet spot in-between, though. <S> “Take-off Flaps” is not always designed to give you the shortest takeoff roll. <S> Obstacle Clearance <S> And that is because once airborne, the more flaps you have deployed, the higher the drag, the less excess thrust available, thus the less you can climb. <S> Simply put, you are now flying at a low speed and barely climbing. <S> Not a good idea <S> if there are tall trees waiting for you at the end of the runway. <S> It would be illegal to take-off on full flaps if: POH says it is prohibited,or For commercial flying, if the flap setting does not provide the minimum required gross obstacle clearance climb gradient (depending on the type of operation and number of engines, between 2.4%-3.0% ). <A> Typically more flaps will get you in the air sooner, but due to the added drag your climb will be shallower. <S> There are aircraft that are not certified for full flap take-offs and in some cases that additional drag might in fact reduce the performance so badly that the take-off run will be extended. <S> The operating manual will provide guidance. <A> Not all flaps are the same and you should read the poh for the suggested and prescribed way to operate the aircraft you are flying. <S> For example the Grumman AA5 series flaps provide a lot of drag and no real extra lift nor slow speed ability. <S> They do allow sharp descents. <S> Whereas a Cessna 172 flaps will increase lift and lower stall speed. <S> Read the manuals. <A> Full flaps can be used on take-off whenever it is called for in the POH, but I have never seen it in any of the 40 different aircraft I have flown. <S> In some aircraft that I've flown (eg Cherokees and the Pilatus PC-12), there is an intermediate flap settings (about 25 degrees) which is used for short/soft field takeoffs because the extra lift from the downwash from the flaps helps the plane liftoff. <A> As a certification requirement, all planes must be able to climb from sea level at max gross weight with full flaps deployed, in standard day conditions. <S> As has been noted by others, the rate of ciimb will be anemic. <S> In the PA-28 that I fly, the third notch of flaps adds a lot of drag and very little lift. <S> POH procedure is to use two notches, not three, of flaps for a short field takeoff.
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So when the runway is really short and there are no obstacles, full flaps might be the solution.
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On a chart, how can I find the frequency for flight following? Is there a map I can refer to in order to pick up the correct frequency for VFR flight following while enroute? I know I can request a frequency from ATC as I depart, but what if I want to fly around and do sight seeing, practice maneuver for my checkride etc. for a while, then pick up flight following for the remainder of the trip? <Q> Otherwise you'll need to consult the Airport Facility Directory for the region your are flying to find a ARTCC (Center) frequency. <A> I assume you're in the US? <S> If you got flight following when you departed from a controlled field then ATC should tell you if you need to change frequency, unless of course they have to stop providing you the service because of workload or whatever. <S> In general, flight following is provided by the nearest TRACON or ARTCC, so you can look in at least three places <S> , two of which are maps: <S> The VFR chart, if you're near a controlled field, which shows the TRACON frequencies <S> The IFR en route chart, which shows the ARTCC frequency for your general area even if you're not close to a controlled field The AF/D, if you're near a controlled field <A> There are three types of ATC service: terminal, approach control, and center (ARTCC). <S> Since you said you're en route, you'll want either approach control or center. <S> If you're inside the Mode C veil (but obviously not already in the airspace) of a Class B or Class C, or if you're near a military base (which all have radar, 'natch), you'll watch to contact approach control, whose frequencies can be found on the tabs of the sectional, such as this example from San Francisco: <S> If you're not within the Mode C veil, call up Flightwatch 122.0. <S> Flightwatch is manned at all times, but it usually takes them at least 5-10 seconds to respond because its infrequently used and they're busy with other things. <S> The trick is not to make your request on the first call up, but do announce your position, since Flight Service has many transmitters, and they will pick the one that is closest to you: <S> N347T: Flightwatch, Mooney 3-4-7-Tango, Crazy Woman 10 seconds <S> pass... <S> Fligihtwatch: Mooney near Crazy Woman, Flightwatch, go ahead <S> (they probably won't get your numbers, but they will pick out your type and position) <S> N347T: Flightwatch, Mooney 3-4-7-Tango, <S> what's the frequency for flight following near C-Z-I? <S> Flightwatch: 4-7-Tango, for radar services near C-Z-I, contact Salt Lake Center on .... <S> Many GPS units have a "nearest" function that will provide frequencies for the nearest FSS or Center: <A> My own experience with flight following, from operating out of both towered and non-towered fields in the Carolinas: After taking off on an XC from my non-towered home field, depending on my heading, I contact the nearest approach control, for example, Wilmington NC (KILM) or Myrtle Beach (KMYR). <S> Before taking off from a towered airport, I will ask the ground controller for FF and get a squawk code and post-departure contact frequency. <S> (ATIS at some of airports I have flown into include instructions for requesting FF); to back that up, if I have not already requested FF, ground or tower controller may be proactive and offer it to me. <S> Airspace around busy airports can be crowded, and I feel safer knowing that I am not an unidentified blip; ATC knows where I am, and what I am doing, and can redirect me if necessary. <S> Positive communication is key to staying safe.
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In the United States, you can consult the VFR Sectional Chart and look for the frequency box located near a terminal area.
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Can I use cellular data to receive in-flight weather on my iPad? I would like to use an iPad for preflight planning. Can I also use the iPad to check weather while I'm en route? <Q> Can you? <S> Yes, but service might be slow or spotty. <S> May you do so legally ? <S> That probably depends. <S> The FAA doesn't specifically prohibit the use of any electronics in GA aircraft; they only state that under 14 CFR §91.21, those aboard an IFR aircraft can't operate electronic devices unless they are Portable voice recorders; Hearing aids; Heart pacemakers; Electric shavers; or Any other portable electronic device that the operator of the aircraft has determined will not cause interference with the navigation or communication system of the aircraft on which it is to be used. <S> [emphasis mine] <S> It's possibly questionable that you as the pilot are an authority on whether or not your devices will cause interference. <S> The FCC, however, has banned the use of cellular phones in flight per 47 CFR §22.925 : Cellular telephones installed in or carried aboard airplanes, balloons or any other type of aircraft must not be operated <S> while such aircraft are airborne (not touching the ground). <S> When any aircraft leaves the ground, all cellular telephones on board that aircraft must be turned off. <S> Whether or not that can be interpreted to apply to an iPad's 3G connection is pretty iffy. <A> On the bright side, the FCC just released a press release which says: November 21st, 2013 STATEMENT OF CHAIRMAN TOM WHEELER ON FCC PROPOSAL TO INCREASE CONSUMER ACCESS TO IN-FLIGHT MOBILE WIRELESS SERVICES Washington, D.C. – <S> Chairman Tom Wheeler has issued the following statement: <S> “Today, we circulated a proposal to expand consumer access and choice for in-flight mobile broadband. <S> Modern technologies can deliver mobile services in the air safely and reliably, and the time is right to review our outdated and restrictive rules. <S> I look forward to working closely with my colleagues, the FAA, and the airline industry on this review of new mobile opportunities for consumers.” <S> -FCC- <S> That being said, even if it might work at low altitudes, I would highly recommend against it if you are flying IFR. <S> I have seen videos of cell phones causing flight instruments to act erratically and they can cause major issues if the airplane isn't specifically certified for it. <A> I have never had much luck with cellular data in flight. <S> This might just be a function of the kinds of locations where I fly, but in my experience the connection is never good enough to get reliable weather information. <S> Once in a while you might get an update, but I wouldn't count on it. <S> A much better option (if you can afford it) is FIS-B , which has always worked reliably for me, especially when there really is weather out there (which is when you really need it to work). <A> Yes....ish. <S> In the US up <S> until recently the answer was an emphatic (FCC-mandated) <S> NO, <S> but the FCC is considering relaxing those rules , and if those rule changes go through you will be legally able to use your iPad's cellular data connection in flight (provided the pilot in command deems it's not a hazard to the flight - so remember to tell yourself it's OK to use the iPad). <S> Pretty much every CFI I've flown with has ignored this rule, and I'll admit to occasionally checking weather on my phone in flight too. <S> There are long, boring technical reasons for this but basically the way the cell site antennas are designed the signal covers the ground below where cell site is - there's not much signal aimed at the sky above it). <S> Since it only generally works on climb-out (when my pre-flight weather briefing is still "fresh") or as I'm descending toward my destination (when I'm typically doing other things like talking to controllers or trying to get the field's weather on the radio) <S> I've not found it to be particularly useful to use cellular data to get in-flight weather / information updates. <S> As Steve said, ADS-B equipment is a much better (albeit more expensive) option.
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Unfortunately, in the US it is not permitted to use cellular service in flight because the FCC does not permit it. It sometimes works, but in my experience only at relatively low altitudes (I typically lose my cellular signal somewhere between 2500 and 3500 feet AGL.
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Are the airport "taxi" plans available online? Whenever I sit in an aircraft and we taxi around the airport, I wonder how exactly is the airport organized, for example, the arrangement of the taxiways and runways. Is it possible to locate airport diagrams? I'm mostly interested in Paris CDG, Prague PRG and Amsterdam AMS. <Q> A great site to download airport diagrams and other charts is charts.aero . <S> As of April 2015, however, the site seems gone. <S> Keep in mind that this is an unofficial website. <S> The charts should not be used for actual navigation. <A> In the US, you can find this on the FAA's website here . <S> You can search for a US Airport, and it will pull up a Airport diagram with Taxiways, Runup areas, and Runways on it. <S> I couldn't find an official guide for European airports, but this site has a detailed guide for CDG , among others, with a taxiway map being one component. <S> They also have a similar guide for AMS . <S> They do not have one for PRG. <S> Keep in mind these are unofficial charts. <S> As Lnafziger noted, this site also has airport charts, including approaches. <S> The downside is you must register (free) first to access them. <S> You can read more in this answer . <A> If you look up the ICAO code, e.g. here <S> http://en.wikipedia.org/wiki/International_Civil_Aviation_Organization_airport_code <S> then Google for the code + charts, e.g "EGLL charts" <S> , you will usually find what you're looking for. <S> https://www.google.co.uk/search?q=egll+charts <A> Airport ground charts are always part of the AIP (Airport Information Publication). <S> They are usually publicly available in electronic format, but not always easy to find. <S> Wikipedia's entry for AIP has a <S> For european airports, you can get them from Eurocontrol (requires registration). <S> However, you can also usually get these directly from the country's CAA or AIS. <S> Here's the ones you asked for (be aware these links may only work for a short period of time): Paris CDG . <S> Amsterdam Schiphol . <S> Prague . <A> Just stumbled across this directory, hosted by VATSIM. <S> Doesn't appear to be entirely up to date but does provide a link for charts for Prague, among many others. <S> (Includes links to content that may be behind a paywall though). <S> http://www.vatsim.net/charts/
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Airport diagrams show all the taxiways and ramps, which is what you are looking for.
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Why are the throttles of aircraft such as the Twin Otter placed on the overhead panel? Some aircraft such as the DHC-6 Twin Otter, have their throttles on the overhead panel: Is there a reason that they are not on a center console between the pilot seats or mounted to the panel like on most airplanes? It seems like it would be more comfortable for the pilot if he didn't have to reach up to change the power settings. <Q> I think it was for two reasons: <S> Many of these aircraft where also designed for harsh climates, so I imagine it's an advantage to have less pulleys and other things which might rust and require maintenance. <S> There is very little space to place the throttles further down, especially with the control column mounted on the DHC6 Twin Otter where it is. <S> If you did want a pedestal, you'd have to seperate the control columns, requiring further mechanical components, and you'd have to route the engine cables upwards, both of which would be undesirable. <S> As you mentioned, there are downsides. <S> Commonly mentioned ones are: <S> It is not particularly comfortable to have you arm raised for an extended period of time, and you lose some sensitivity in it. <S> You hope that the other pilot used his deodorant that morning. <S> Other somewhat similar aircraft which use this configuration are the PBY Catalina and Grumman Goose. <S> Another one is the Avro York heavy transport aircraft. <A> Overhead throttles are a pretty common thing in seaplanes (see the picture in Manfred's answer ). <S> This actually came up as an EAA Young Eagles <S> FAQ and in addition to the reasons Manfred gave the Grumman engineer they spoke to gave an explanation I'd not heard before: …first and foremost, the reason the throttle are overhead is due to a physiological issue related to the g-forces encountered during water landings. <S> At times, forces as high as 3 Gs can be registered on contact with the water, and by having the throttles hanging down from a pivot point above, it's nearly impossible for the hand of the pilot to bend the throttle. <S> When the downward force is encountered, the pilot's hands will move downward as well, so the force is applied to the throttle in a way that will not damage the linkage, and it will not likely result in an abrupt throttle position change. <A> In the case of a high wing multi engine plane, like the Grumman seaplanes, the distance and a less convoluted path for a steel cable from the throttle control to the engine may have a lot to do with this design choice. <S> However, this is a guess completely unencumbered with facts.....
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With a panel mounted throttle, it's likely that a higher-G landing on the water (or on the deck of a carrier) would result in a bent throttle. It makes for straight path for the controls to reach the engines, as all of these are fly by cable.
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What does a pilot have to do in order to fly as a second in command in a private jet? If a pilot has the opportunity to fly as an SIC in a private jet, what FAA requirements must they comply with in order to fly with passengers? <Q> Don't know if the same rules still apply, but back in the 70s and 80s I used to fly legally as the second pilot on corporate jets with just a commercial license with IFR and multi-engine ratings. <S> At the time I had no type ratings. <A> If you are flying passengers for profit you will then require at least a Commercial Pilots Licence. <S> Modern day training courses which prepare you to be the first officer or co-pilot as it were, tend to result in you holding a frozen ATPL, ie, you have done all the exams and you're now hour building in order to qualify for the licence. <S> You will also likely have completed a Multi-Crew Co-operation course of some description, obtained your jet rating and hold any relevant Instrument Ratings. <S> It probably depends on which provider you were choosing to apply for. <S> EDIT: <S> Ah, my apologies, this post was in relation to European (EASA) guidelines (more specifically in the UK really). <A> In general, FAR Part 61, section 55a,b outlines specific requirements for those designated as Second-in-command of Aircraft requiring more than one pilot. <S> Section b probably covers the specific training you're curious about. <S> See also parts 121, 125, and 135 for more specific requirements.
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Theoretically you can fly a Boeing 747 on a Private Pilots Licence as long as you have the relevant type ratings.
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What happens when a temporary pilot certificate expires? What can I do if my not-so-newly issued temporary pilot certificate is about to expire and I haven't gotten my permanent certificate yet? Is there any way that I can keep flying while waiting for it, and is there a way to check on the status of the permanent certificate? <Q> According to this AOPA article , you can request an extension online through the FAA's Airmen On-Line Services . <S> You also can look up your current status here: <S> http://www.faa.gov/licenses_certificates/airmen_certification/new_verification_info/ <S> In my case, this was updated about a week before my card arrived in the mail. <S> You can also see what date's submissions they have processed here: http://www.faa.gov/licenses_certificates/airmen_certification <A> When I got my ATP, I had to file on paper rather than through IACRA and my certificate was delayed long enough that I needed to ask an inspector to write me out a new temporary. <S> Took about ten minutes start to finish, the hardest part was the drive to the FSDO. <A> I passed my checkride on April 19th and was told by both the DPE and my instructor that typical wait times to receive the permanent certificate in the mail are around 90 days. <S> The DPE told me to mark the 120 expiration date of the temporary certificate on my calendar and that I should call the local FSDO if I had not received the permanent one in the mail and it was approaching two weeks from the expiration of the temporary. <S> The FSDO can grant 30 day extensions to your temporary certificate. <S> Just keep this in mind <S> : It's is very important not to let the temporary expire since that temporary certificate "supersedes" all previous certificates. <S> This means you have NOTHING if a temporary Private Pilot certificate has expired and you have not yet received the permanent one. <S> Even your original Student Pilot certificate is no longer in effect, since it was superseded when you were issued your temporary private certificate; therefore you won't even be able to fly solo anymore. <S> As long as you contact your local FSDO within a couple weeks prior to the temporary certificate's expiration, you should have no problems.
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The FSDO can issue you a new temporary certificate if your previous one has or is about to expire and your permanent one hasn't arrived in the mail yet.
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How do Ram Air Turbines get deployed? I understand that most larger jets have a Ram Air Turbine (RAT) in case of total electrical failure (for instance, when you run out of fuel ) in order to at least have some hydraulics and a couple of instruments. The RAT gets deployed automatically at the loss of electrical systems. But how does it get deployed? I'm interested in the triggering mechanism, as, during a complete electrical failure, there can be no electrical trigger (computer or otherwise). So it must be something mechanical. Or are they relying on batteries? I figured it'd have to be some failsafe mechanism, like stored (hydraulic or otherwise) pressure held back by something like an electromagnet or hydraulic pressure, cut the power and presto, the RAT deploys. However, I've never seen one deployed on an aircraft sitting on the ground with the power off, so that kind of shot down that idea. <Q> In between the loss of power and the RAT spins up <S> you have the batteries to fall back to which are normally fully charged. <S> The Airbus Manual has the following comment on the APU: <S> In case of total loss of all main generators, the RAT is automaticallyextended and drives the emergency generator via a hydraulic motor. <S> TheEMER GEN supplies the AC ESS BUS and the DC ESS BUS via the ESS <S> TR.The ECAM WD remains powered, with associated procedures presented. <S> Alternate law is operative through ELAC 1 and SEC 1 <S> ( Source ) <S> While this is for the CRJ , who call it an Air Driven Generator (ADG): <S> In the event of a complete AC power failure in flight, the ADG willautomatically deploy and supply emergency AC power to the ADG bus andto the AC essential bus. <S> If the automatic deploy function fails, theADG can be deployed manually by pulling the ADG manual release handleon the ADG CONTROL control panel at the rear of the center console. <S> ( Source ) <S> A RAT, with the spring loaded actuator visible: <S> I think most if not all are spring loaded, and have a little help from gravity on the way. <S> You'll also notice that many are stored to be pushed into place by the jetstream. <S> Have a look at this video below around 0:20. <S> The slow upwards motion suggests that it's having to reload the spring energy at 1:20. <S> The doors are attached mechanically. <S> Taking a look at the Airbus Electrical System : <S> As can be seen, there's a hierarchy to electrical power use, and the battery feeds the essential busses, where the RAT deployment would be included. <S> If I'm not mistaken, power is very limited: You loose some of the more fancy control computers along with the non-necessary stuff, like the copilot's displays, as can be seen in the following video . <S> Bear in mind that some aircraft, such as the 747 (up to -400), do not have a RAT on the aircraft, and rely on the windmilling engines to provide sufficient hydraulics to control the aircraft, and as such there's no deployment of sorts necessary. <A> But how does it get deployed? <S> I'm interested in the triggering mechanism, as, during a complete electrical failure, there can be no electrical trigger (computer or otherwise). <S> Think the other way: it is not difficult to create a mechanism which deploys mechanically when there is no voltage. <S> On powering on plane's circuitry a latch withholding the RAT device is retracted and since then the device is hold retracted only by magnetic force of electrically powered coil which is stronger than loaded spring. <S> If the voltage drops unexpectedly, the coil loses its effect and loaded spring pushes the device out. <S> On regular powering of plane's circuitry off, latch for keeping the RAT device retracted when there is no electricity is shifted back into its place. <S> I am unable to get any actual blueprints <S> but I tried to show you that moving something when a voltage is gone is not necessary a difficult mechanical engineering task. <A> But how does it get deployed?NORMAL: <S> RAT is retracted (by manual cranking or by electric motor), against heavy spring bungee force and locked in faired position. <S> EMERGENCY: <S> RAT is unlocked and the spring bungee extends the RAT in to airstream.
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The RAT is automatically deployed on many aircraft, including the CRJ and A320 series, but it can be manually released as well.
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How can I know if a landing exceeds the hard landing threshold for a Cessna 172S? How does a pilot determine the difference between a firm landing, and one that needs to be written up for a hard landing inspection in a Cessna 172S? <Q> Was it uncomfortable or did it hurt? <S> If it hurt you, it probably hurt the plane. <S> That 500 pound engine is hanging a foot and a half from the firewall by four bolts. <S> It's not hard to cause some damage. <S> Anyway, if you think it needs to be checked, just say something to the mechanic. <S> It's not that time consuming, and it's better to be safe than sorry. <A> StallSpin has already mentioned the crucial point. <S> The firewall will be damaged if the nose gear experiences an excessive shock. <S> It can easily be inspected for deformation by removing the upper half of the cowling (looking through the hole for the oil dipstick, even with a flashlight, is not sufficient). <S> The main gear is very sturdy and will probably be damaged last. <S> Anyway, I would sugest to have a close look on it and check the overall condition. <S> Also check the position of the tire valves. <S> They should be at a 90 degree angle to the tire. <S> A hard landing can go together with brake application during touch down which could cause damage to the tires. <S> Last but not least the oleo strut of the nose gear should be inspected. <S> Find the clearance of the oleo strut under normal loads in the POH. <A> You should refer to the service manual for your specific airplane, but to give an idea, the Cessna 172 AND SKYHAWK SERIES 1969 THRU 1976 <S> SERVICE <S> MANUAL says that you should look for "buckled skin or floorboards, and loose or sheared rivets in the area of the main gear support": 18-61. <S> REPAIR AFTER HARD LANDING. <S> When such evidence is present, the entire support structure must be examined, and all support forgings must be checked for cracks, using a dye penetrant and proper magnification. <S> Bulkheads in the damaged area must be checked for alignment, and deformation of the bulkhead webs must be determined with the aid of a straightedge. <S> Damaged support structure, buckled floorboards and skins, and damaged or questionable forgings must be replaced.
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Buckled skin or floorboards, and loose or sheared rivets in the area of the main gear support will give evidence of damage to the structure from an extremely hard landing.
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When/How may I replace the Turn Coordinator with an Artificial Horizon? I've seen a few panel shots where the traditional turn coordinator has been replaced with a second artificial horizon, as shown below. The benefits seem obvious - if my artificial horizon failed I'd certainly like to have a fully functional back-up rather than a turn coordinator with no pitch information. Under what circumstances/conditions are these second horizon gyros acceptable as replacements? Are there any drawbacks that I should be aware of if I'm considering installing one. <Q> The <S> How It Flies in section on Spiral Dive Recovery <S> mentions: <S> If you don’t have good outside references, you should not rely on the attitude indicator (artificial horizon). <S> The attitude indicator contains a gyro mounted on ordinary mortal gimbals, which can only accommodate a limited range of pitch and bank angles. <S> A steep spiral can easily cause the gyro to tumble, whereupon it will need several minutes of relatively straight and level flying before it can re-erect itself. <S> Military aircraft have non-tumbling attitude indicators, but you’re not likely to find such things in a rented Skyhawk. <S> Therefore, you should roll the wings level by reference to the rate-of-turn gyro. <S> 8 <S> Being a rate gyro (as opposed to a free gyro <S> ) it has no gimbals, and therefore can’t possibly suffer from gimbal lock. <S> 8 <S> That is, the turn needle or turn coordinator, whichever you happen to have. <S> And in section on Spin Recovery <S> it adds: If you get into a spin in instrument conditions, you should rely primarily on the airspeed indicator and the rate-of-turn gyro. <S> The inclinometer ball cannot be trusted; it is likely to be centrifuged away from the center of the airplane — giving an indication that depends on where the instrument is installed, telling you nothing about the direction of spin. <S> The artificial horizon (attitude indicator) cannot be trusted since it may have tumbled due to gimbal lock. <S> It is better to trust the rate-of-turn, which cannot possibly suffer from gimbal lock, since it has no gimbals. <S> Remember, it is a rate gyro (not a free gyro), so it doesn’t need gimbals. <S> But with ordinary artificial horizon the turn coordinator combined with vertical speed indicator (despite it's problems like rather slow reaction time) are useful backup for recovering from in-flight upsets. <A> Check out AC 91-75 . <S> I believe it has everything you're looking for. <S> It seems the FAA really doesn't like turn coordinators these days: “[T]he FAA believes, and all other commenters apparently agree … the rate-of-turn indicator is no longer as useful as an instrument which gives both horizontal and vertical attitude information.” <S> Which is completely true... <S> I don't see a drawback, really. <S> You'll also have to buy a slip-skid indicator (it seems that most replacement attitude indicators can be ordered bundled with one.) <S> , so you're really not losing anything. <S> Edit: The other posts and comments raise some good discussion, I suggest reading those as well. <A> I can think of a couple of things, the most prominent is the power source. <S> Turn indicators are usually electrically powered, whereas attitude indicators are vacuum powered, and the idea is to provide redundancy should either power source fail. <S> This is not always the case though, and if your second attitude indicator is powered electrically, that's obviously a non-issue. <S> The second thing is the absence of a ROT indication, forcing you to calculate the correct bank angle for a standard rate turn should you ever really need one. <S> The only situation I can think of where it is imperative that you can do a standard rate/half rate turn is a no-gyro approach in which case you've probably also lost your vacuum source, and you don't want to start playing mind games, but it's not as crucial as the power source redundancy. <S> As for whether it's acceptable, StallSpin seems to have that covered. <S> The pictured second attitude indicator is fitted with a slip indicator, so that should cover that aspect. <A> The turn coordinator or turn and slip indicator <S> (they are different) usually are electric powered. <S> The artificial horizon is usually vacuum driven. <S> If you replace the turn coordinator with an artificial horizon, it should be electric, assuming the existing one is vacuum. <S> Rate gyros are not prone to gimbal lock, or "toppling", as are most attitude indicators. <S> If an attitude indicator topples, it can take several minutes to correct. <S> Also, read 91.205. <S> Generally, a gyroscopic rate-of-turn indicator (needle) and a slip-skid indicator (ball) are required for IFR flight. <S> Two attitude indicators won't do.
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If you have good enough artificial horizon designed to avoid gimbal-lock, the you don't need turn coordinator.
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What is Crew Resource management (CRM)? I hear a lot about CRM these days (it seems to be a buzz word). It is related to safety, but what exactly is it? From what I know, it also applies to single pilot flights (even in a Cessna 150!), but where is the "crew" that is being managed in this case and how does it improve safety? <Q> Pilots these days (even single pilot ops) have a wealth of resources available to them. <S> Anything you can see and anyone you can talk to is a resource, and CRM is about making efficient use of those resources. <S> Flying a light single you will have a subset of these resources: <S> Cockpit displays <S> Charts <S> Checklists <S> ATC <S> FSS <S> Flight Watch (EFAS) <S> Live Weather downlinks (e.g. XM satellite weather) <S> On a large transport aircraft these change a bit: <S> Cockpit displays <S> Charts <S> Checklists <S> ATC <S> FSS <S> EFAS <S> Onboard RADAR <S> The QRH (quick reference handbook) <S> The FOM (flight operations manual) <S> The other pilot(s) <S> The cabin crew Passengers (Doctor in a medical emergency? <S> People helping in an evac?) <S> Dispatch Medlink <S> Company Ops For ground ops: Fuellers Ramp personell Gate agents <S> More and more emphasis is placed on managing these resources as you move up the chain. <S> By the time you are taking your first 121 upgrade checkride, it is more about judgement and CRM than it is about the flying. <A> CRM is not just crew anymore - it's now typically referred to as " Cockpit Resource Management" (or in some cases, when no crew is present, as "Single-Pilot Resource Management") and it's something the FAA emphasizes on all checkrides. <S> CRM includes all resources available to any pilot. <S> In a typical light GA aircraft this means checklists, instruments, gauges, radios, and nav. <S> However, ATC is a resource, especially during abnormal or emergency situations. <S> So is FSS, Unicom, or even other aircraft nearby (think relaying an IFR cancellation etc). <S> In a large aircraft, CRM obviously includes your flight and cabin crew, plus other airline or corporate perks like dispatch. <S> The safety improvements come from knowing when to offload work or call on systems or people for assistance. <S> Even a non-pilot passenger can be a huge help in spotting other aircraft, tuning radios, rummaging around for your spare pen... <S> that's all CRM and lets the pilot focus on flying. <S> From the Private Pilot PTS <S> (FAA-S-8081-14B) : <S> Special Emphasis Areas <S> Examiners shall place special emphasis upon areas of aircraft operations considered critical to flight safety. <S> Among these are: 15. <S> Single-Pilot Resource Management (SRM), and 16. <S> Other areas deemed appropriate to any phase of thepractical test. <A> In Europe: As far as I know, Crew Resource Management or Cockpit Resource Management training is only needed for commercial/airline flights where multi-pilot aircrafts are flown. <S> It's basically Multi Crew Co-operation (MCC) training (plus the communication aspect) with the purpose of increasing the efficiency of communication, coordination, decision-making and leadership in the cockpit. <S> In the end it breaks down to efficient pilot communication, efficient distribution of cockpit tasks and "inter-pilot-double-checks" (meaning a pilot checking the other pilot actions and vice-versa).
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CRM is about making use of all available resources to safely conduct a flight.
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How should the crew callout 1,000 ft. prior to assigned altitude? When climbing or descending in a multi-crew cockpit, most SOP's require a verbal callout at 1,000 ft. prior to the assigned altitude. I typically hear different callouts by different people: "One to go" "Six thousand for seven thousand" "Six thousand climbing seven thousand" "Six for seven" Is this just a personal preference kind of thing or is there an actual safety benefit to one or the other? <Q> As far as I know, there are no published FAA guidelines on it. <S> An operator develops their SOP, and the FAA approves it, so whatever the SOP says is approved by the FAA. <S> Ours is, "one thousand to go," by the pilot flying, and then, "nine thousand for ten thousand," responded by the pilot monitoring. <A> As Ralgha stated, this kind of callout would be included in the SOP. <S> A couple I found in searching were the NBAA (same in their helicopter procedures by the way) and Angel Flight NE , as well as some generic CRM guides. <S> The FAA Instrument Procedures Handbook also mentions altitude callouts, suggesting something like "two to go" and "one to go" (in thousands). <S> The NBAA includes this specific phrasing: <S> The callout is to include the altitude vacating and the assigned altitude i.e. “Six thousand for seven thousand” or “Flight level three-zero-zero for two-niner-zero”. <S> After the PF makes this call, the PNF will verify and validate the call by stating “check”. <S> This Flight Safety Digest mentions that USAir used to use the "two to go" and "one to go" phrasing, but opted to change this for the same that the NBAA uses. <S> The new policy has the pilot flying make this call, since they are in control of the climb, and makes it more clear what the final altitude will be. <S> The Flight Safety Foundation went in to a bit more detail about the "why" behind the callout. <S> They mentioned that in their observations, the callout was sometimes not done due to workload of other more important things going on in approach/descent. <S> They explain the benefit: <S> This is not to suggest that the 1,000-ft callout is trivial. <S> On the contrary, it ensures that both pilots concur about the altitude target, directs the attention of a flying pilot who might be distracted back to the impending level-off and draws both pilots’ attention to what the autopilot is supposed to be doing. <S> Another resource that suggests the important is a report of an aircraft overshooting its altitude by 600 feet because the callout was missed. <S> This report is in the ASRS database , report number 317750. <S> I also found it referenced in this book about communication. <S> They didn't really comment on it specifically, but used it as an example of how communication is critical. <S> Specifically, the more exactly the terminology is defined, the more clear the communication will be. <A> I don't really have some scientific reason for it, but it just seems more logical to me and easier to interpret. <A> This verifies again that the proper altitude is set and correct. <S> One to go has too many meanings. <S> 100/10000/1 mile/ one <S> leg/ one minute/?? <S> It’s ambiguous and has too many casual meanings and doesn’t verify altitude set. <S> Easy to ignor the verification.
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While I don't fly in a plane requiring more than one person, when there happens to be two pilots, such as one flying safety so the other can fly under the hood, I prefer the "1,000 feet remaining" or "1,000 remaining" call out. Our SOPs require Altitude leaving (climbing/descending ) to assigned altitude.
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Can large aircraft go VFR? Is it legal for large, multi-crew, aircraft (such as the A380 or B747) to go VFR? I would guess it's legal just as any other aircraft. Is this ever done, like during training or test-flights? If it isn't legal, what's the limiting factor? I'm talking real VFR from take-off to landing, not an VFR-on-top IFR clearance. As I don't have a spare 747 sitting around waiting for me to take it out for an afternoon spin, I'm interested more in the general sense, is it legal anywhere, and are airlines taking advantage of it? <Q> The FAA treats large airplanes the same as any other airplane when it comes to VFR flight. <S> They are required to maintain the same distance from clouds, only fly with the same minimum visibility, see and avoid other aircraft, etc. <S> However, since only IFR flights are allowed above FL180 (without a special exemption), and large turbine airplanes are terribly inefficient at low altitudes, so it doesn't happen very often. <S> In the US, Part 121 flights have the most restrictions of any of the operating rules, and they have multiple regulations relating to VFR flight, including this one 1 : <S> 14 CFR 121.611 Dispatch or flight release under VFR. <S> No person may dispatch or release an aircraft for VFR operation unless the ceiling and visibility en route, as indicated by available weather reports or forecasts, or any combination thereof, are and will remain at or above applicable VFR minimums until the aircraft arrives at the airport or airports specified in the dispatch or flight release. <S> So <S> However, they must also comply with their Operations Specifications and Flight Operations Manuals which will have detailed procedures covering the conditions where it is allowed. <S> Outside of 121 there are even fewer restrictions on VFR flight. <S> 1 <S> There is also: §121.347 - Communication and navigation equipment for operations under VFR over routes navigated by pilotage. <S> §121.349 - Communication and navigation equipment for operations under VFR over routes not navigated by pilotage or for operations under IFR or over the top. <S> § <S> 121.649 - Takeoff and landing weather minimums: <S> VFR: Domestic operations. <S> § <S> 121.667 - Flight plan: <S> VFR and IFR: Supplemental operations. <A> Generally the airlines operating procedures will only permit IFR operation. <S> I know of one pilot who has delivered old airliners to the Mojave boneyard on a VFR flight from LAX. <A> As far as I know, the size of the aircraft does not matter much. <S> You just cannot plan airline flights (carrying passengers) in VFR. <S> Although I think, in case the destination airport is uncontrolled and you have VMC (and the airspace class allows), you can cancel IFR and proceed VFR bellow the VFR maximum altitude. <S> Depending on the country and class of airspace you're flying in, you might also have other limiting factors such as speed (200/250 KIAS) and altitude (18,000/20,000 ft). <A> Do heavies go VFR? <S> Absolutely, and not only do they go VFR <S> they do carrier breaks as well. <S> The US Navy has a "scheduled airlines" that ferries personnel and equipment around the continent. <S> Its passenger line uses DC-9's. <S> I was in Beeville, Texas going through advanced jet training in the A4. <S> We were already in the pattern doing carrier pattern touch-and-go's when we heard a DC-9 call at the VFR initial. <S> We were expecting the following call to be for a straight-in VFR approach, and to our amazement we heard, "Tower Heavy 201 for the break. <S> " <S> The tower came back quickly, "Break approved." <S> This was the coolest thing I have ever seen. <S> Absolutely stunning. <S> This big guy comes in to the field at 800 feet and makes the break! <S> I was cheering in the cockpit watching it. <A> I believe if you are operating under part 121, you are IFR always. <S> I would suspect if you are relocating an airliner and under part 91, you could fly VFR <S> but I would bet the airline would require IFR as their standard operating procedures.
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Occasionally non-revenue flights for aircraft positioning etc, will operate VFR for expediency. yes, even if it is operated by a 121 carrier, they are allowed to fly VFR by the regulations.
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What is differential braking? How is differential braking different from regular braking? How do you accomplish differential braking and why would you need to use it? <Q> Aircraft with toe brakes have the brake pedals at the top of the rudder pedals. <S> You press the left one with top of your foot and it applies the left brake(s). <S> Press the right one to apply the right <S> brake(s). <S> Normally you press them at the same time and with the same force to keep the airplane from veering to one side <S> (imagine just locking up the brakes on one side of the airplane). <S> Differential braking is when you press one brake pedal harder than the other. <S> It is used as an additional form of directional control when <S> : You have no other forms of steering (either because the steering has failed or there is no nose-wheel steering) <S> The rudder/nose-wheel steering is not effective enough (because you are going too slow or the wind is too strong). <S> You want to be careful when doing this, though because you can over do it and create more directional control problems than you originally had. <S> If you use differential braking during the takeoff roll, it will increase the amount of runway that you use since you are applying the brakes (even though it is only on one side, it will keep you from accelerating as fast). <A> Simply put, differential braking means you can apply different brake pressure for each brake. <S> In a car you have one pedal that applies equal braking to all of your wheels. <S> In many airplanes you have two brake systems and you control the left side brakes independently from the right side -- this is differential braking. <S> You press the right toe brake and the right main gear wheels have brake pressure applied -- likewise for the left toe brake. <S> You use this to aid in turning the aircraft, as in many light airplanes the nose wheel is free castering, you cannot control it. <S> In larger airplanes you have a tiller to steer the nose wheel, but differential braking can still be used to make tighter turns. <A> I don't have a citation for this, but the classically famous Mikoyan-Gurevich MiG-15 jet fighter was fitted with differential braking, which operated via the rudder pedals in conjunction with a lever on the joystick. <S> As I recall, the instructions were: to brake in a straight line, remove feet from both rudder pedals and squeeze the brake handle. <S> To use brakes for turning, deflect one rudder pedal and squeeze the handle. <S> Typical USSR equipment. <S> Astonishing performance considering the technology available, but if you don't know exactly what you're doing you can kill yourself just trying to get off the ramp.
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To make use of differential braking, you need two brake pedals, these are typically actuated by applying toe pressure to the rudder pedals (known as toe brakes).
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What is the difference between a POH and an AFM? Some aircraft come with a Pilot Operating Handbook and some come with an Aircraft Flight Manual. Why the different name, and is there a difference between them? <Q> Both a POH and an AFM meet the "Operating Limitations" requirement in the ARROW acronym. <S> The difference between the two is mainly in length and content: an AFM is usually a thinner document, satisfying the requirements of <S> FAR 23.1581 and <S> not much else, while a POH contains these required items plus other information like system diagrams (The contents & format of a POH are standardized in GAMA's Specification 1 ). <S> A better explanation might be this: The AFM is a regulatory document (it's contents are prescribed under the section of the regulations the aircraft was certificated under - Part 23, Part 25, etc). <S> The POH is a GAMA-defined document whose contents meet the regulatory requirements of an AFM, and present other information in a standardized way so that a pilot can go from a Cessna to a Piper to a Mooney to a Socata and browse the book to learn about the airplane they're about to fly with all the information presented the same way <S> no matter who the manufacturer is. <S> The other two types of documents you may encounter are an "Owner's Manual" (which usually goes along with a thinner AFM & provides some of the information found in the newer-style POH) and a Pilot Information Manual (PIM) which is a "generic" version of the POH which many pilots buy so they can study the procedures without removing the regulatory document from the aircraft. <S> Chapter 9 of the Pilot's Handbook of Aeronautical Knowledge talks a little about the differences between the two documents (and a whole lot of other flight documents). <A> all the above answers are wrong. <S> A POH is a 'kind' of AFM. <S> All aircraft must have an approved AFM. <S> Before 1978 this could be anything (owners manual, POH, etc.). <S> After 1978 GAMA (general aviation manufacturers association decided to standardize the AFM around the POH format. <S> The name POH stuck ... <S> but it is still a kind of AFM. <A> All you need to know is that an AFM is specific to an aircraft serial number.
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Parts of the POH (like the Limitations section) are FAA-Approved, and serve as the AFM, and both documents are typically associated with a specific airframe (by serial number). A POH is less specific and generalized for a particular make or model
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How does a Mach Meter determine the speed of sound at a given altitude? By my understanding, the Mach Number at a given altitude is calculated by dividing IAS by the speed of sound at that altitude. So how is this speed of sound calculated to display the Mach Number on the Mach Meter? Does the Mach Meter share the same pitot tube used to calculate airspeed? <Q> An (analog) machmeter looks something like this: <S> So it's more like an more complex version of the airspeed indicator, in this case correcting for the altitude in the process. <S> That being said, I found this extract apparently from an FAA publication: <S> These systems assume that the temperature at any altitude is standard; therefore, the indicated Mach number is inaccurate whenever the temperature deviates from standard. <S> These systems are called indicated Machmeters. <S> Modern electronic Machmeters use information from an air data computer system to correct for temperature errors. <S> These systems display true Mach number. <S> Most systems today use more detailed data from sensors to give a correct value through a variety of (complex) calculations. <S> A little more discussion is available on PPruNe . <S> Side note: <S> Speed of sound ($a$) <S> itself is solely determined by temperature (that being said, you are able to determine it from pressure, as pressure is a function of temperature) <S> hence the problem with the analog system above. <S> For air: $$a=\sqrt{R{\gamma}T}~m/ <S> s$$ <S> Where: $R=287$ Specific Gas constant [dimensionless] $\gamma=1.4$ Specific heat ratio [dimensionless] $ <S> T=$ Absolute temperature [K] <S> Remember that you're reading off indicated airspeed [IAS] in knots in the cockpit, which is not the same as True airspeed [TAS] converted to m/s, in case you're trying to work out your mach speed manually ($M=\frac{TAS}{a}$) <S> For use without knowledge of airspeed & temperature, Wikipedia gives the following formula for subsonic flows: $$M=\sqrt{5((\frac{P_T}{P}+1)^\frac27-1)}$$ <S> Where: <S> $P_T=$ <S> Total Pressure <S> $P=$ Static Pressure <A> Most modern jets use an Air Data Computer (ADC) to calculate (among other things) <S> Mach Number. <S> Air Data Computer <S> An ADC is simply a computer which accepts measurements of atmospheric data to calculate various flight related data. <S> A typical ADC may be connected to$^1 <S> $: <S> Inputs Static System Pressure Pitot Pressure <S> Total Air Temperature (TAT) <S> Outputs (Calculated) <S> Pressure Altitude <S> Baro-Corrected Altitude <S> Vertical Speed <S> Mach Number Total Air Temperature <S> Calibrated Airspeed <S> True Airspeed <S> Digitized Pressure Altitude (Gillham) <S> Altitude <S> Hold <S> Airspeed <S> Hold <S> Mach Hold Flight Control Gain Scheduling. <S> Each of the inputs and outputs may be analog or digital depending on the design of the system, and are used for many purposes throughout the airplane. <S> Each output is a purely calculated value based on the various input measurements and data stored within the unit. <S> In the case of mechanical instruments, they are both connected directly to the pitot static system. <S> In the case of an ADC, the pitot static system is connected directly to the ADC and then electrical signals communicate the airspeed and mach number to the electric airspeed indicator and mach meter (or EFIS), which no longer require actual pitot static connections. <S> The Math <S> A simplified example for the Mach Number calculation$^2$ would be based on the pressure inputs: $$Mach~number=5((PT/ <S> PS+1)^{0.2857}–1)^\frac12$$ <S> Where: $PT$ = Total Pressure $PS$ = Static Pressure <S> The actual calculation makes corrections to the pressure data to compensate for installation errors and nonlinear sensor readings. <S> Note that it doesn't actually calculate the (local) speed of sound (LSS) in order to determine the current mach number, but with the TAT input and the calculated mach number, it could calculate it by calculating the outside air temperature (OAT/SAT) first: $$SAT=\frac{TAT}{1+0.2\times{Mach}^2}$$ <S> $$LSS=38.945\sqrt{SAT}$$ <S> For example, let's say that the TAT is -36C (237.16K) <S> and we are flying Mach 0.80: <S> $$SAT=\frac{237.16}{1+0.2\times0.8 <S> ^ <S> 2}=\frac{237.16}{1.128}=210.25 <S> °K=-63 <S> °C$$ <S> $$LSS=38.945\sqrt{210.25}=38.945\times14.5=564.70knots$$ <S> Again, these are simplified formulas because the actual ones would consider sensor error, etc. <S> $^1 <S> $ List of inputs and outputs obtained from Air Data Computers . <S> $^2 <S> $ Formula from TAT Sensor Operation and Equations . <A> A Machmeter does not determine the speed of sound. <S> It doesn't even need to: $$Mach~ <S> Number=\frac{P_T-P_S}{P_S}$$ <S> Mach number is simply the ratio between total pressure minus static pressure, divided by the static pressure. <S> Here is why: $$Mach~ <S> Number=\frac{TAS}{LSS}$$ <S> The Mach number is true airspeed versus the local speed of sound <S> $$TAS= <S> IAS\sqrt{T}\div\sqrt{P}\div16.97$$ <S> Converting indicated speed to true speed, we need to multiply with the square root of absolute temperature (in °K) <S> $$LSS=38.94\sqrt{T}$$ <S> Also the local speed of sound is directly proportional with the square root of absolute temperature (in °K) <S> If you divide $TAS= <S> IAS\sqrt{T}\div\sqrt{P}\div16.97$ by $LSS=38.94\sqrt{T}$, the $\sqrt{T}$ will cancel eachother out. <S> $$Mach~ <S> Number=\frac{IAS}{\sqrt{P}x}$$ <S> IAS we already have <S> , it's dynamic pressure minus static pressure, and $P$ is just static pressure, or <S> , like I said in the beginning: <S> $$Mach~ <S> Number=\frac{P_T- <S> P_S}{P_S}$$ <S> See, no thermometer... only dynamic and static pressure.
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Some older mechanical Machmeters not driven from an air data computer use an altitude aneroid inside the instrument that converts pitot-static pressure into Mach number. To answer your question about the pitot source for the Mach Meter: Yes, they use the same pitot and static sources as the airspeed indicator.
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Do similar angles on a plane make it more stealthy? I learned in my intro to engineering class at my college that 5th gen fighters (which are stealth aircraft) are designed with similar angles to evade radar. Why is this true? Also, does the angle matter? Many of these modern fighters looks to have very similar angles (no pun intended). <Q> The angle matters because radar works kind of like a mirror. <S> Imagine holding a mirror out in front of you. <S> If you start to twist it in any direction, you reach a certain point where the light coming off of you is no longer bounced back into your eyes, but is reflected off in another direction. <S> Radar however cannot ever be completely reflected away, but this same principle allows a significant portion of the radar's energy to be deflected off in a useless direction, instead of back toward the dish. <S> So it makes sense that every other facet on the same (geometric) plane would be at the same angle. <S> This means that the radar's energy is directed away in a very specific direction (away from the source), rather than a bunch of different angles (that would be more likely to return the energy to the source). <A> Short answer: <S> Yes. <S> Long answer: There are two ways to prevent the radar energy from being reflected back to its source in order to avoid detection: Absorption, and Directed reflection. <S> Absorbers work well only over a small wavelength band, so some reflection is unavoidable. <S> Now the idea is to collect all reflected energy along specific directions, so the aircraft will reflect very little energy in all other directions. <S> Radars can adjust their sensitivity, and if they operate at their most sensitive setting, they will detect many false positives, but also a stealth aircraft. <S> If the stealth aircraft maneuvers, it will momentarily shine one lobe of the reflected radar energy back at the radar receiver, causing it to reduce sensitivity such that the weak returns in all other directions will not be registered. <S> Compare this to a diamond which will reflect light back at specific angles, causing it to sparkle. <S> There are two-lobe designs (Northrop YF-23 and B-2) and four-lobe designs (Lockheed F-117 and F-22), but the idea is the same in all cases. <S> Reflected radar energy is focused in narrow beams, so very little is given off in all other directions. <S> This is not to say that such aircraft can evade detection. <S> When the radar stations are networked, they can pretty well trace those sparkles and stitch together the aircraft's location. <S> Also, NATO aircrews which had participated in international maneuvers were less than impressed with the stealth capabilities of their colleagues, but were under a gagging order to be more specific. <S> And then there is infrared. <S> What does it help to be invisible on radar if the aerodynamic heating of the leading edge can be picked up by an IR receiver from 300 km away? <S> When B-2s were flown over to the Farnborough airshow, British Eurofighters could detect them far out over the Atlantic already. <A> I assume you're using the term 'similar angles' in a geometric sense, to mean that the angle from a reference like the aircraft centerline to the lines made by two structural features are the same. <S> Your photo shows this well, with the wing leading edge angle the same as the horizontal stabilizer leading edge angle and the same as the inlet (?) angle. <S> I believe the reason for this is that the overall likelihood of radar detection is lower because each of these features will reflect radar signal in the same direction as one another. <S> This means that the reflection will be very much stronger in the direction they reflect, but that reflection has a very narrow spread. <S> In contrast, the features will not reflect radar strongly at all other angles. <S> Thus the radar dish has to be "lucky" to be at exactly the right angle from the aircraft to receive the strong signature, and so the overall probability of detection is reduced since at most angles the reflection signature is reduced. <S> This is also the reason that flat surfaces are used in many stealth designs. <A> Define "with similar angles". <S> In itself the phrase means nothing. <S> The basic shape of the airframe is of course a function primarilly of its required function to provide lift and enough inner volume for the aircraft's components. <S> Stealth depends on several factors: absorption scatter deflection <S> These are functions of the shape and materials used. <S> Creating surfaces that cause incoming EM waves to scatter in many directions rather than being reflected directly back causes the return signal received by a RADAR system to be much weaker, reducing the detection range. <S> But a big part is also played by placing grids in air intakes, shielding sharp edges with sawtooth overlays (see the canopy and bay doors, for example), and covering different parts of the aircraft in different materials.
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The angles are similar because that angle was determined to have the smallest radar signature.
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Is it legal to fly the localizer approach when cleared for the ILS? Most ILS approaches include localizer minimums that can be used if the glideslope transmitter or receiver fails. For example: In this case, to fly the ILS you would intercept the glideslope just before PRAIZ and fly the 3 degree glideslope down to minimums. If we were cleared for the ILS approach, but we instead wanted to ignore the glideslope and fly the LOC only approach 1 (for whatever reason: training, practice, etc.), could we do that without specific ATC approval since it is on the same chart and says "ILS or LOC"? 1 We could fly the LOC only approach by crossing PRAIZ at 2,200 ft. and then descend at an "optimum" rate until leveling off at the MDA of 520 ft. <Q> The question really boils down to: "ATC clears me to fly an approach. <S> Is the approach clearance defined by what is on the approach plate, or is it specific to the type of navigation equipment used?" <S> It turns out that it is based on the approach plate. <S> The answer is found here: <S> https://www.faa.gov/air_traffic/publications/atpubs/aim/aim0504.html Section 5-4-5.a.3(a) <S> More than one navigational system separated by the word “or” indicates either type of equipment may be used to execute the final approach (e.g., VOR or GPS RWY 15). <S> There is no requirement in FAR/AIM to tell approach control which equipment you will be using (beyond the equipment code in your flight plan). <S> As further corroboration, section 5-4-7.d in the above document specifies that ATC is allowed to clear you for an approach even if the equipment required for some types of navigation systems is not available. <S> This actually is not that rare because NDB/GPS approaches are still used even if the NDB is not working. <S> The requirement to notify ATC in the event of navigation radio failure is separate. <S> Oddly, you don't have to tell ATC if you have a glideslope receiver at all, but you are supposed to tell them if one that you do have breaks. <S> If it happened while you were actually flying the approach, I would encourage you to execute a missed approach. <S> But if you just want to fly an ILS/LOC approach as localizer-only for practice, ATC doesn't care and you don't need to tell them. <A> That's even very common when doing flight training, but instead of going to Exec I would sugest yo to shoot a real LOC (only) approach in Pompano just north of it <S> ;) <S> I can't offer you the 100% legal, floorless, perfect answer for this <S> but ther has been no trouble, yet. <S> Probably the most correct option you have is to particularly ask for the LOC APCH for flight training, but if you demonstrate good airmen ship flying the approch, following a predetermined descend profile leveling off half a mile prior to your DTL, this sould even keep you within half scale until leveling off at yor MDA. <S> It doesn't matter on which plate the approach is printed, the key point for ATC is, that you are following the same lateral and approximately the same vertical profile, at pretty much the same speed. <S> Ther is obviously no other technique to maintain seperation required. <S> Obviously you should not plan on doing this without one crew member having the runway inside, or at least with a cloud base <S> reported well above your LOC minimums. <S> If you fail your glide path indicator (put a sticker on it) and you are - for any reason - not visual with the runway at your minimums passing the DTL go around, do not change back to the ILS. <A> Practically, you could likely do it and ATC would not notice; however, you are not technically adhering to the ATC clearance as it was provided to you and as you read back. <S> §91.123 Compliance with ATC clearances and instructions. <S> (a) <S> When an ATC clearance has been obtained, no pilot in command may deviate from that clearance unless an amended clearance is obtained, an emergency exists, or the deviation is in response to a traffic alert and collision avoidance system resolution advisory.
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When the chart is written as in your example, you are cleared for the approach, and you must use one of the approved types of navigational equipment to fly it.
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Which companies develop software for airplane systems? I am wondering which companies develop software for systems on airplanes? I am a software engineer major and I would love to work with planes in some way. I am not sure if that would be more of an electrical engineering position or not, any input would be greatly appreciated. <Q> This entire branch is known as avionics (aviation electronics). <S> Limited work is generally done by the aircraft producers themselves, and the majority is subcontracted to specialist companies. <S> A name which does come to mind is Thales group , who are behind much of the Airbus A380 avionics. <S> Other ones are Rockwell Collins , Honeywell and Garmin . <S> These are however though often at the top of an iceberg of various subsystems and controls. <S> A huge increase in this field (particularly in small aircraft but now also coming to larger ones) has been in tablet computers and the like in the past few years, and while I'm not a pilot <S> I think it's hardly at the limit of what is possible. <S> An iPad has more processing power than most if not virtually all aircraft flying today. <S> Many customers today are disappointed if they don't get WiFi and inflight entertainment onboard. <S> With the increase in drones and unmanned aircraft, it's certainly not a shrinking field. <S> A large area of this includes complex calculations and plenty of sensors. <S> And more drones and unmanned aircraft require advanced communication and control systems. <S> I've even heard about dynamic models of aircraft who adapt the plane's control to maintain control in the event of structural failure or serious damage. <S> Only having scratched the field personally it's a very broad field with plenty. <A> Whether it is something for you depends a lot on your expertise as a software engineer. <S> Are you doing embedded programming <S> then avionics might be a possibility for you. <S> But you have to realize it is kind of a specialized field that is very strict in its procedures for safety reasons. <S> If you enjoy rapid development processes and see quick improvements you are destined to become very frustrated in the avionics world. <S> It is not a job I would recommend to everyone. <S> That being said, there are plenty of other software jobs related to aviation. <S> Airports, Air Traffic Control, airlines, maintenance organizations all run dedicated software to support their processes. <S> I did quite some programming in the past for Air Traffic Control related simulations. <S> Nothing safety critical, the focus was on validating new ideas, which in my view was much more fun than working on operational (safety critical) systems. <A> GE Aviation develops some avionics in addition to engines and other systems.
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As Manfred mentioned, there are quite a number of companies that develop systems for aircraft, all with a software component to it.
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Do some airplanes have weighing scales on the landing gear? It seems to me that takeoff weight is an important piece of data, and if one had weighing scales between the wheels and the aircraft body, one could precisely determine it. However, searching the internet, there seem to be no scales and cargo/fuel/passenger weight is estimated by adding up what is brought on board. Why aren't scales common? And are there any commercial airplanes that have them? <Q> Yes, such system exists, for example the Honeywell WBS . <S> * <S> It was developed during the sixties and installed as an option on the Boeing 707-300 freight aircraft. <S> Other aircraft that had a similar (optional) system include the L1011 and Boeing 747. <S> The reason they are not common is that they add cost in the form of installation, weight and maintenance. <S> While quite accurate when in good condition, the reliability of the weighing systems used to be poor, which probably contributed to the fact they never became wide spread. <S> Because crew are commonly operating on several aircraft types these days that have take-off weights of more than 100 metric tonne difference (e.g. A330 and A340, B747-400 and B747-8) there is an increase in take-off weight confusion related incidents. <S> This, combined with the fact that systems are becoming more reliable, makes it likely that these weighing systems will be used more in the future. <S> * <S> An advert for it in a 1987 Flight issue. <A> Simple answer <S> For one thing it will not work because of wind: <S> Once you put wings on a fuselage, you will need to bring that airplane into an enclosed hangar for the scales be accurate. <S> Mind you, this is exactly what being is done whenever an airplane is being weighted for mass & balance purposes, about every three years: <S> enclosed hangar and massive scales under the gears. <S> Doing it on a daily basis in an already crowded airport is not an option. <S> Complex answer <S> What you really need to know for your a/c is mass, not weight. <S> Also, you'd want to know the mass distribution inside the a/c, not just to calculate the center of gravity (which a scale can also do), but also to make sure that load limits are respected in each section (which a scale will not do). <S> Adding and removing numbers on a load sheet works pretty good for this purpose, as does estimating passenger weights and luggage as an average, although there are talks that those averages need to be increased lately. <S> Even if you eventually found a way to scale each airplane before takeoff, in a controlled environment, the extra costs will never be justified since you basically improved on something that works. <A> On some newer B747, there is a weight indication near the maindeck door. <S> I seem to remember Atlas Air aircraft having this. <S> This would probably have its sensors somewhere in the landing gear. <S> It was a big LED thing and showed you the current weight of the aircraft, e.g. 340.5 (thousands kgs). <S> When a pallet came in it would show a corresponding increase in weight, so if a pallet weighing 3000kgs came in the weight would now show 343.5. <S> It was never used for calculating the weights of the pallets in the airports I worked from <S> but I understand that Atlas does a lot of operations for the military in some dodgy areas and at these airports this device helps verify that the weights are not too far off.
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It is mostly found on freight aircraft because they have a less predictable load distribution (centre of gravity) than passenger aircraft.
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Are the window wipers on jet aircraft ever deployed in flight? Many commercial airliners have car-like window-wipers. I would presume this is for taxiing only, as the wind would surely keep the windows free from water when airborne, or do they turn them on in flight? Also, don't these wipers cause a lot of drag, and wouldn't it be more economical to have some kind of air-jet blowing from nozzles to keep the windshield clear? <Q> They are usually stowed out of the wind stream so don't really cause much drag. <S> The Learjet's on the other hand DO have hot air that blows on the windshield <S> and we sometimes used it to blow water droplets off of the windshield when on the ground. <S> However, the primary purpose of the hot air was to heat and defog the windshield. <S> On a larger airplane, the additional piping, valves, etc. required to get the hot air all of the way up to the windshield <S> actually weighs and costs more than just putting the windshield wipers up there along with electrically heated windshields to keep them from fogging up. <A> In the EMB-145 we could use the wipers below 170 KIAS. <S> Wipers are really only useful on or near the ground, so this was not a limitation that really mattered. <S> Our windscreen wasn't the best at deflecting rain, so in heavy precip we would use them inside the FAF when looking for lights/the runway and during taxi to the gate. <S> On departure we would use them in heavy precip to taxi and takeoff, turning them off in the after takeoff flow. <S> Other airplanes, as Lnafziger points out have better flow characteristics over the windscreen or blown air and are not equipped with wipers. <S> In any airplane, the wipers are only potentially useful for ground ops, takeoffs and landings and serve no purpose at altitude. <S> In addition to the wipers, we were also equipped with an electric defroster to keep the windscreen free of fog and ice, and this was used during the descent from cruise to landing. <A> On the 747-100 and -200 airplanes we had windshield wipers which we occasionally used on short final in heavy rain. <S> The switches were on the overhead panel on the captain's side, but the usual procedure was to ask the flight engineer to turn them on but to stand by to turn them off if the visibility was worse with them on than off, which was sometimes the case. <S> I only remember leaving them on for the touchdown a couple of times. <S> We never used them while taxiing that I recall. <S> They were very noisy, distractingly so.
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In the Falcon 50 and 900, we have windshield wipers that we are allowed to use in flight (up to 205 KIAS), but I have never used or seen them used in the eight years that I have been flying them because they simply aren't needed.
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Why were flying boats phased out? Before WWII, flying boats were a popular form of transport, and the advantages are many: No need to build runways, capability of emergency landing on water, availability of large landing sites and no tire wear and tear. Why have they been abandoned? <Q> The biggest single reason for the decline of flying boats was the proliferation of long runways during World War II. <S> Large airfields were a result of the long-range heavy bomber campaigns in Europe and Asia. <S> Century of Flight has an interesting article that goes a bit more in depth. <A> Apart logistics and the availability of long runways afterr WWII, the reason for the phasing out of the sea planes was maintenance . <S> The aircraft was operating in an extremely corrosive environment, something that can be seen nowadays in the firefighting planes like the Canadair and other smaller seaplanes. <S> More info: FAA Corrosion Control . <S> Generally speaking, operation in corrosive environments like water is something that requires very careful inspection and time consuming maintenance. <S> For example even the Chinook helicopter needs extensive cleaning after operations that involve landing on water . <S> Finally the increased drag due to the shape of the flying boat is something that every designer and airliner wants to avoid. <A> Flying boats were a solution for long over water flights when engines were less reliable and could not produce sufficient power to lift large loads. <S> Regular flying boat services between New Zealand and Australia which I am most familiar with, often never flew above 5,000ft. <S> This meant they subjected passengers to considerable discomfort at the mercy of bad weather. <S> In areas where there were primitive support facilities and no runways, especially in the Pacific, these flying boats continued to operate into the early 'sixties, but as more and more runways were built the need for flying boats diminished and the cost increased. <S> Tahiti and New Zealand operated the last scheduled routes for large flying boats in the Pacific. <S> Shin Meiwa in Japan did propose a civil version of their impressive STOL US-1 which would have carried >50 passengers in a pressurised cabin. <S> India is interested in such aircraft for search and rescue but no orders have arisen for the civilian aircraft. <S> Beriev in Russia has also developed an equally impressive Be-200 jet powered flying boat (smaller sibling of the A-40 Albatross). <S> The Be-200 is offered as an amphibious airliner configuration, but so far airlines have not shown any interest. <A> The second biggest reason: Where would they land in Denver? <S> And many more cities that have robust air traffic but not many lakes or waterways that are suitable.
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The infrastructure advantage of flying boats – the ability to operate heavy aircraft without long runways – was no longer relevant. Also the engines need to be inspected and cleaned after every operation.
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How does a commercial flight pilot handle turbulence? In general, passengers dislike turbulence. Avoiding all turbulence sometimes is not viable, as it would make the flight too long, too expensive (fuel consumed), or simply not having alternatives. How does the pilot deal with turbulence? Does he or she keep the same altitude? The same speed (relative to the wind)? Increase power? AoA? <Q> Most of the time the turbulence we experience is termed "chop", which is akin to what you experience on a boat on the lake -- bumps but no real altitude deviations. <S> With altitude deviations we'll call it "turbulence". <S> Within these broad categories we'll qualify them with "light", "moderate", "severe" and "extreme" in reports to ATC and other aircraft. <S> These reports do suffer from a fair bit of subjectivity with respect to aircraft type (wing stiffness) and pilot experience. <S> If it is light chop, I'll generally just ride it out and turn the seatbelt signs on. <S> The first thing I'll do if encountering moderate chop or turbulence is to query ATC and get ride reports from aircraft ahead of us and at different altitudes than us. <S> From this information I'll make a determination to ride it out or to request a climb/descent. <S> If the turbulence was particularly bad, slowing down was an option, but I only came across that need a few times. <S> Our ability to descend would often be limited by route length and fuel and major lateral deviations also depended on contingency fuel, so in some cases we had no choice but to stay in the chop. <S> If the turbulent areas were well forecast or had lots of PIREPS, our dispatchers would sometimes route us differently. <S> As for power adjustments, if we weren't slowing down due to aircraft limitations <S> I would just adjust power so that maximum airspeed deviations stayed below Mmo. <A> Some large aircraft (maybe all?) have a minimum and maximum turbulence penetration speed. <S> For the 747-100 and -200 aircraft the minimum was 270 knots and the maximum 320 knots IAS. <S> I forget the mach equivalents. <S> Those same aircraft had a turbulence mode on the autopilot that reduced the sensitivity to pitch and roll deviations. <S> However, many pilots (including myself) would hand fly through heavy turbulence because the autopilot ride even in turbulence mode <S> was worse than what we could get by hand. <S> There are situations in which changing altitude is not an option. <S> For example, if you cannot descend because doing so would burn too much fuel, but you cannot climb because you are already as high as you can go. <S> It also may not be possible to deviate much from your course because of fuel considerations. <S> Consider a Hajj flight from Jakarta to Jeddah. <S> It's 10 hours <S> and that's what you've got fuel for. <S> Depending on the time of day, there is often (seemingly always) <S> a line of thunderstorms too long to go around between Sumatra and India. <S> You pick your way through the line using radar to avoid the intense echoes. <A> He also has the option of flying around it, although many times this is impractical.
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The pilot can slow down the plane, or he can try flying at a different altitude.
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Can you fly a plane in a wind tunnel? There are very large wind tunnels out there. Wouldn't it be very efficient to test new airplanes flying them "on the spot" inside of these tunnels? That is, in free flight - not mounted to a pylon? One could presumably omit the test pilot and remote control them, get excellent visual feedback and have a completely controlled environment. Has this been done? If not, why? <Q> It would actually miss the point of wind tunnel testing. <S> A free flying model could only be subject to air stream in speed and direction so that the forces are balanced. <S> A fixed model on the other hand can be subject to air stream of any direction and speed and the forces measured. <S> It is important to measure the forces under those conditions too. <A> Could you? <S> Yes, probably, <S> but it would be very difficult due to the very limited space. <S> You would have to have a huge airflow in excess of 50 knots for a small aircraft, and you could not simulate any motion fully, such as takeoffs rolls. <S> You could also not test stalls and other manoeuvres. <S> I think the main reason against this is that this is simple areas of flight dynamics that can just as well be done with computational fluid dynamics on a computer for a fraction of the effort and cost. <S> I don't think it would be safer either. <S> It's a very confined space, and you couldn't cut the airflow very quickly, so it's probably more dangerous than flying outside with unlimited space and a stable airflow. <A> You certainly could fly a completely assembled aircraft in a sufficiently-large wind tunnel -- at least in theory (theory is an awesome place - everything always works there. <S> When I retire I'm moving to theory). <S> In reality there are lots of drawbacks which have already been pointed out, but there's one that hasn't been yet: <S> Wind tunnel testing is traditionally done with scale models, and even then it's not "cheap": It takes a lot of power to move wind through a tunnel at high speed, and scaling this up to a full size airframe - even small-airplane size like your typical Cessna or Piper trainer - is cost-prohibitive since you would have to build the entire plane and then pay to blow high-velocity air over it. <S> ( There are wind tunnels at this scale though - at least one. <S> NASA spent a lot of money on it, and then Boeing and Airbus came out with their new super-jumbo planes which don't fit!) <S> It's also worth pointing out that the kind of fluid dynamics modeling that used to be done with wind tunnels and smoke trails is now often done with Computational Fluid Dynamics (CFD) software . <S> Cheaper, Safer (no risk of parts blowing off and bouncing down the tunnel), and more accurate in many regards -- but nowhere near as much fun to watch :) <A> There have been tests of real aircraft in wind tunnels, with a pilot sitting in the cockpit. <S> But in all cases the plane had been tied in place with strings. <S> Trimming the lift and especially the thrust in all phases of the test is really impossible. <S> The Messerschmitt 109 was tested in the French Chalais-Meudon tunnel in 1940, the Bell P-39 was tested at Langley, where the top speed could be improved from 340 to 392 MPH, <S> the P-51 was tested at Langley in 1943 like most small military planes of that period, and lately a stealth demonstrator made by MBB was tested in 1984, in most cases with the pilot in place. <S> These are the ones I know; there were certainly more. <A> Yes you can. <S> Yes it has been done. <S> The caveat being that most (all?) <S> of the tests are done with scale models rather than full size planes. <S> Free flight wind tunnel tests are done for different reasons from static mounted tests. <S> Where static mounted tests are done to collect measurements of forces acting on the aircraft/part, free flight tests are done to understand/confirm the stability of the aircraft. <S> Flying a model plane in such confined spaces is very difficult and typically the plane will tend to wander around in the wind tunnel. <S> As such, the data that you can get from a free flight test is very limited. <S> Due to the difficulties of doing the test and the limited amount of data you can get from it most new plane designs don't go through such a test. <S> Instead, what typically happens is that the design goes straight to a radio controlled scale model that is flown outdoors to study its stability. <S> However, when trying out new ideas that has not been developed it is still worth doing the stability tests in a controlled environment - in a large wind tunnel. <S> Here are some old videos of free flight wind tunnel tests (these come from a time period where the behavior of delta wings were not yet fully understood): https://www.youtube.com/watch?v=OGmigdhxMRw <S> https://www.youtube.com/watch?v=aDIQc3-umf4 <S> Here's a more recent video of a free flight wind tunnel test of the Blended Wing Body: https://www.youtube.com/watch?v=B7zMkptajMQ <A> Problem is: propulsion is missing. <S> Once you expose a plane model to an airstream, the airfoils (wings) start producing lift but also drag. <S> In real world, an airplane requires propulsion to overcome the drag (induced drag,parasite drag,..) in order to move forward. <S> The wind tunnel airplane model would just lift-off and fall behind, there would be no chance to establish a stabilized flight attitude where propulsion equals drag and lift equals weight. <S> Such a stabilization is required to seriously start measuring. <S> That's why the models are strapped down to a pylon or whatever. <S> Measuring results can therefore also be reproduced (certain fixed AoA's at certain airstream speeds etc.)
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No, you cannot fly a plane like that. And yes people are still doing it.
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Where do airshow pilots practice? I would assume that buzzing the tower and general hot dogging around the airport is prohibited, so how do airshow pilots get practice? Do they practice at high altitudes? If that is the case, how do they practice stunts that by nature require low altitude, like Bob Hoover's waltzing landing? <Q> Many of the Part 91 rules which would need to be broken in order to practice aerobatics are waived within these aerobatic practice areas (such as the 1,500 ft. "floor" for normal aerobatics in 91.303 <S> (e)). <S> The FAA has to approve them, and their guidance includes a good description: 4. <S> AEROBATIC PRACTICE AREAS. <S> Aerobatic competition pilots, airshow pilots, and others who wish to practice aerobatic maneuvers not necessary for normal flight and below an altitude of 1,500 feet above ground level (AGL) must use a waivered aerobatic practice area. <S> These areas are not to be considered airshow sites. <S> The aviation community uses these practice areas to establish and maintain proficiency as well as enhance competitive skills in all the recognized aerobatic maneuvers. <S> They are established by the waiver applicant in conjunction with the local FSDO and may have dimensions of several miles in various directions or be as small as a contest box; i.e., a cubic box with a dimension of 3,300 feet on all sides. <S> Inspectors should be receptive to the establishment of these areas, consistent with safety and the efficient use of the NAS. <S> It is imperative that the safety of all nonparticipating aircraft be considered when issuing a Certificate of Waiver or Authorization for an aerobatic practice area. <S> An aerobatic practice area may be established over an airport if coordinated with airport management, and can be used to practice landings like those that Bob Hoover does. <S> Besides the special rules in these areas, it is also a good way to warn other traffic that aerobatics could be taking place because they are listed in the A/FD and a NOTAM is issued whenever they are hot. <A> A lot of the maneuvers can be learned and practiced at higher altitudes. <S> In the US, the airshow pilots usually request a waiver from the FAA (to waive certain rules) so they can practice at lower altitudes. <S> The waiver will specify the location, hours of operation, who can use the waiver, which specific rules are waived (usually aerobatics within 4 NM of an airway, and/or certain altitude restrictions). <S> In the US, a lot of airshow pilots get their start competing in IAC aerobatic contests. <S> This gives them the opportunity to learn the maneuvers and get some very experienced critiquing. <S> As they progress in the sport they attempt more difficult maneuvers at progressively lower (but still safe!) <S> altitudes. <A> That allows the crews to familiarise themselves with the actual local conditions as well as the visual cues ("hey, there's a tall red chimney <S> right where I need to start my turn, handy"). <S> And for "buzzing the tower", you can of course practice that with anything really. <S> A nice tall free standing tree for example, a chimney of an abandoned factory, anything tall and slender in an area where you're allowed to practice. <S> Or lacking that mark a spot on the ground and in your mind extend that up. <S> And oh, you can practice low altitude things at high altitude the same way, create an imaginary plane at say 10.000 feet, calibrate your altimeter to show 0 at that altitude, and now just fly like you would normally. <S> Safe too, if you get things wrong and would end up flying into the ground, you now still have 10.000 feet before you splatter yourself.
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Aerobatic pilots typically use "aerobatic practice areas" when they practice. In addition to what's already been mentioned, there's usually at least one day and more often several days of practice sessions at the field where the show is to take place before the actual event.
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Do any flight simulators go completely inverted? From the pictures I have seen of airline simulators, it looks like the range of motion is limited to somewhat level flight. Are there any flight simulators, possibly military trainers, that can do a complete barrel roll? <Q> These sims fall into the entertainment category more than the training category, but they are full motion, in cockpit sims. <S> I have also been in a similar type of sim at a Harris/Boeing sponsored party in Seattle made by a company whose name I cannot remember that did the same thing. <S> That one in fact was capable not only of rolls but also loops and could be pretty violent (I wanted to see if it would spin... <S> it did). <S> Here's a video of one of the Pulseworks models. <S> They have some at the Udvar-Hazy center at IAD (free admission, and a shuttle from the terminal). <S> They cost a bit of money to get into. <S> They are also often setup in pairs <S> so you can go into a dogfighting scenario with the box next to you. <S> Bring a friend. <A> It is possible to design one which does but impractical. <S> The PulseWorks simulator, while entertaining, is not realistic and cannot accurately simulate inverted flight. <S> The simulators motion is not made so the sim cabin matches the actual attitude of the real aircraft during maneuvers; rather to induce sensory illusions in the trainee crew which match what one would expect in flight. <S> They are designed to create motion which can mimic sensory illusions during flight in the +1-1.3 G range, typical for all commercial air carrier or cargo operations. <S> As such building a simulator with full inverted capability would simply be unwarranted for the requirements of a typical FMS. <S> It also provides a pretty inaccurate simulation of the kinesthetics of inverted flight, as most inverted condition end up being in the positive G range. <S> It's also not practical for aerobatic or military flight training as at most <S> it could only simulate -1G and -1-2G for a brief moment, and the whole simulator module would have to be rolled inverted for the effect even when simulating negative G maneuvers while the aircraft is erect. <A> Like it has been said here it is very difficult to simulate g-forces outside of the common civil flight envelope. <S> But it is possible! <S> I have built one, you can watch videos of it on YouTube here , and here . <S> Like Zeus said, even with this 2DOF 360° you will feel "wrong" g's very often, e.g., banking with 90° feels like a 1 g rudder slide. <S> And a loop feels more like flying inverted (-1 g). <S> But in real life you have +3 g's. <S> I think this simulator is very useful to practice aerobatics! <S> You feel the same emotions, fear, and excitement, like in real life, e.g., my first real life loop scared me in the same way the simulator did. <S> Same thing with barrel rolls, lazy eights, cubans, hammer heads, inverted, etc. <S> Also it is very exhausting and your stomach will have some fun for sure <S> :-D <S> Flying with a VR headset teaches the right reactions very, very well. <S> Actually I make, or do not make, the same mistakes both in the simulator and in real life. <S> A friend (a Lufthansa A320 pilot) was also surprised how good this thing is in teaching, but to reach this level the simulator requires many little (invisible) additions: sound shakers, g-effects (on set cueing), VR headset, g-belt tensioner, force feedback, and many things more. <S> In comparison to standard simulators, this concept is far advanced for aerobatics or military training, IMHO. <A> I believe there was one at RAFC Cranwell that could go inverted. <S> Source: <S> my sister's, at the time, fiancée who was training there. <S> I may be remembering wrong - it was a while ago. <S> Also, while not a flight sim in itself, many years ago there was an arcade cabinet for Sega's G-LOC called the R360 that had full 360 degree motion about all axis. <S> I would be gob-smacked if that same tech had not been used in more professional environments.
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Full Motion Simulators (FMS) are used, primarily for transition and currency training on large aircraft which operate in the air transport category and where the training is simply impractical for both cost and safety reasons to do it in the real thing. Pulseworks makes some full motion sims that are capable of inverted flight and infinite barrel rolls.
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Why does cabin air have to be dehumidified? When air is piped in from outside and into a pressurized cabin, it is also dehumidified in the process. All airlines provide beverage service on even short-haul flights to combat the dryness of the air. Why is it necessary to dehumidify cabin air? <Q> A lot of consideration is placed on the airframe (which has to hold for 20+ years) rather than the passengers. <S> One of the primary reasons is to slow corrosion of the aluminium airframe. <S> This is also why the Boeing 787 is <S> a lot more humid - corrosion is no longer an issue in a composite fuselage (or a lot less at least). <S> Boeing and the Economist sum it up nicely <S> I think: the greatest issue lies with the cold fuselage skin interacting with moist air, which will condensate and speed up the rate of corrosion. <S> But condensation in the gap between cabin and hull can be lethal. <S> This gap contains much of an aircraft's wiring, and water can damage <S> that wiring's insulation . <S> Such a problem is thought to have contributed to the loss of a Swissair DC-11 off the Atlantic coast of America a few years ago. <S> Too much condensation causes other difficulties, as well. <S> There have been cases when ice has built up inside the tailplanes of aircraft, causing their rudders to freeze and thus preventing their pilots from steering them. <S> An aircraft such as a Boeing 747-400 can accumulate as much as 700kg of condensation before it reaches equilibrium . <S> Even though that is only about 0.17% of the 400 tonnes such an aircraft weighs fully laden, it is enough to cause problems for the pilot when he tries to trim the balance of the aircraft. <S> And 700kg is about the weight of nine men. <S> So the aircraft is carrying the equivalent of at least nine non-fare-paying passengers, in an industry where every extra kilogram affects fuel consumption and profit margins. <A> There are a couple of things that contribute to the dryness of cabin air: <S> Cabin air is drawn from engine bleed taps in the high pressure compressor. <S> This is ambient air, which at the flight levels is normally quite dry and then heated and compressed, which will lower the relative humidity, making it seem even drier. <S> The air cycle machine subsequently extracts moisture from this hot, high pressure air within the pack and used it to provide evaoprative cooling in part of the pack responsible for cooling the air flowing through it (The pack needs to extract heat so when air is expanded into the cabin <S> it is cool enough - it does this with compression/expansion cycles and cooling). <S> As the air coming out of the packs undergoes expansion to cabin pressure, it will cool down and <S> this will help counteract some of the dry feeling by boosting relative humidity. <S> The Boeing 787 takes a new approach and provides pressurization and air conditioning with electric compressor motors instead of engine bleed air, and using this method (and a composite airframe) allows for much higher relative humidity in the cabin. <A> When I flew the C-141 and C-17, their environmental systems weren't intentionally dehumidifiers (designed to reduce the overall humidity), but they did push the air through a fabric bag called the 'sock' to capture droplets that formed during cooling. <S> As air continued to flow, that moisture could evaporate and rejoin the stream, or be vented overboard through a drain. <S> At altitude, the air is very dry. <S> Flying through weather in the approach/departure environment could cause a lot of moisture to get ingested, and so needed to be sorted out. <A> To add to the answers above: the other main reason (besides condensation) for keeping humidity low is to prevent the growth of mold and bacteria in the cabin and the air conditioning system, which over time may pose a health hazard to the plane's occupants. <S> And I can't stress enough that the air is not de-humidified , but that the outside air (which is pumped into the fuselage to provide pressure and fresh air) at cruising altitudes is bone-dry. <S> The air in the cabin is actually more humid than it would otherwise be, thanks to the passengers ( <S> when they exhale or sweat they release water vapor into the air, and since about 50% of the cabin air is re-used it helps to keep the humidity levels a little higher than they would normally be). <S> The newest-generation of widebody planes from Boeing and Airbus (787 and A350) actively humidify the air in the cabin, but that requires carrying extra water on every flight (50-100kg, according to Flight Global , plus the weight of the humidification equipment). <S> Additionally, these airplanes need to install active drying systems in the the areas outside the cabin (e.g. behind the lining or above the cabin ceiling) to prevent the insulation mats from soaking up all that extra humidity ( example from CTT ). <S> In conclusion, the air will be more humid on these aircraft, but it takes a lot of effort (and weight).
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The primary reason low humidity is desirable in most airplanes is that water contributes to corrosion and that is bad for the airframe.
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What is Cost Index? I'm not sure if it's just in Boeing aircraft, but I've heard that Cost Index has something to do with flight planning but have no idea what it is. What is it for and how is it calculated? (I'm happy for the simple version of the calculation if it's too hard to explain) <Q> The cost index is a number used in the Flight Management System (FMS) to optimize the aircraft's speed. <S> It gives the ratio between the unit cost of time and the unit cost of fuel. <S> With this number, and knowledge about the aircraft's performance, it is possible to calculate the optimal speed for the aircraft, which results in the lowest total cost. <S> Speeds slower than the optimal speed will result in less fuel burn, but also in more flying time. <S> The cost of the extra flying time outweighs the fuel savings at speeds below the optimum speed. <S> Speeds faster than the optimal speed will result in more fuel burn, but also in less flying time. <S> The saving of less flight time do not outweigh the fuel burn at speeds above the optimum speed. <S> A low cost index means that the cost of time is low or that fuel is expensive. <S> It will result in a low speed. <S> High cost index means high cost of time (e.g. passengers about to miss their flight connection) or low fuel price (rare these days). <S> At the minimum cost index (0) only fuel counts. <S> This will result in the aircraft flying at Maximum Range Cruise. <S> At the maximum cost index only time counts. <S> This will result in the aircraft flying at Maximum Cruise Speed (V mo / M mo with a buffer) <S> Airlines generally have a standard cost index they use for planning and adjust them on a flight by flight basis. <S> This document from Airbus explains the cost index in more detail. <A> According to this article , Cost Index of a flight is: <S> The ratio of fuel costs to all other costs. <S> So the lower the Cost Index, the lower the fuel burn in relation to the other operational costs of the trip. <S> This generally means flying the airplane slower and higher in order to conserve fuel, but that is offset by the higher maintenance costs due to the airplane being in the air longer and inspections becoming due sooner, so is true only to a certain point. <S> It is a generic term, not specific to Boeing. <A> High Cost Index : <S> Fast flight, low crew times, high fuel use, etc. <S> Low Cost Index : Slow flights, high crew times, low fuel use, etc. <S> It's always a complex compromise on what is best, and policies vary between airlines and how they use their aircraft. <S> I don't think you can 'do' a calculation though in that sense, since it's a value which often comes from computer formulas. <A> Cost Index is the ratio of time related cost to Fuel related cost. <S> The time related cost considered, is the fixed cost. <S> The time related costs ( <S> airplane operated costs affected by flight time), include but: -flight crew-cabin crew-leasing-maintenance (time related) <S> -airframe <S> material /labor-engine material /labor-other costsThe time related costs may be difficult to calculate. <S> You will have to get the time related cost form your account Unit/department <S> The fuel costs are expressed in units of currency per quantity of fuel :cents/pound, while the time related cost is USD/min
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While somebody else might be able to explain it better, Cost Index is the relationship between fuel use and flight time.
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How are Virgin Galactic's SpaceShipTwo's windows so large? From Virgin Galactic on SpaceShipTwo: Windows in the passenger compartment will be 13 inches (33 centimeters) wide by 17 inches (43 centimeters) tall. IMO that's enormous for an airplane, especially for a spaceplane! But, wouldn't such large windows cause problems? The Concorde had particularly small windows (passengers say that it's almost passport book sized) to maintain the integrity of the airframe and cabin pressure if a window happened to crack at 60,000 feet AMSL. But wouldn't such a large window cracking at 110 km AMSL on SpaceShipTwo definitely cause cabin pressure to equalize to atmospheric pressure in seconds? What redundancy does SS2 have to prevent catastrophe in such an event? <Q> Here are a few ideas: <S> First and foremost, we're not handling metals here. <S> Composites have the advantage of being able to be made stronger by adding on a few layers around high-stress area like windows. <S> This was difficult with metals since this needed some sort of fasteners or adhesives to do. <S> This reinforcement is seen in the photo below. <S> The windows are designed to keep an even pressure all around in the context of the fuselage shape at that point. <S> You'll notice the flange design which keeps the fuselage shape and stop it from popping open. <S> This is a little like the thicker part of a bottle neck. <S> This is very difficult (if possible) to do well in a metal fuselage to this extent. <S> (source: msn.com ) <S> The usage is completely different. <S> Concorde was a commercial aircraft, intended for many years of operation. <S> This is a very low-cycle aircraft which will see a fraction of that flying. <S> The number of pressurisation cycles is a lot lower , putting much less force on the windows. <S> As for safety, the style of flying is completely different. <S> Probably flown by test pilots, the aircraft might never even experience rain and will fly under very predictable conditions, with very few flight cycles . <S> Periods of elevated temperatures gradually degrades many materials, this is much less a concern with short flights . <S> If I gather correctly this is the main issue with sustained high-speed flight, as seen on Concorde and SR-71 and other aircraft. <S> (source: guardian.co.uk ) <S> Composites have a lot lower thermal expansion <S> (CFRP vs. Aluminium is an order of magnitude lower) which reduces issues with expansion in the fuselage. <S> Concorde was a commercial aircraft with weight and operating price in mind. <S> This aircraft is built for this purpose, with the windows considered as a main feature from the start . <S> You could probably have been able to make the windows a lot larger on Concorde, at the unacceptable price of weight, production and operating cost. <S> Needless to say that knowledge of materials and structures has advanced substantially, all our these features can be modelled in detail on computers, not necessitating the traditional conservative approach. <S> As for redundancy, predecessor SpaceShipOne had double pane windows and double seals everywhere. <S> For the passengers without suits, if a window were to blow entirely, you're most probably out of luck. <A> I think ultimately it's a business question. <S> Virgin Galactic is selling tours at a premium price where as Concorde was sold to move people from point <S> a <S> to point b. <S> With Concorde, since the point of the craft was to get people from point A to point B very very quickly, they put money into big engines and efficient aerodynamics. <S> The view doesn't really matter in that equation, but you do need structural integrity. <S> So they went with the cheapest way to get that structural integrity, small windows. <S> Virgin Galactic, on the other hand, is selling an experience. <S> And frankly, if you're going into space the two biggest selling points are going to be zero gravity and, honestly, the view. <S> Hence, even though it will make the craft more expensive to reinforce properly, they are installing very large windows. <S> As a note, airliner manufacturers could also install big old huge windows if they wanted as well, but do you want to pay another $50 a flight just to have a bigger window? <S> For most people the answer is no...hence small windows. <S> Basically it's just a matter of figuring out what you are trying to sell <S> and, then, putting money into that selling point. <S> It's what gets you a good return on your investment :). <S> PS- lol, and after all that writing I appear to have answered the "why" and not the "how". <S> Well, let the internet judge me as it will <S> , I'll leave this answer up for now :). <A> The Concorde had a lot of thermal expansion due to air/skin friction, that may have impacted window size. <S> SpaceShipTwo travels at much lower speeds, and doesn't have that issue. <S> As long as it is thick enough, made out of strong enough materials, they should work safely.
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Ultimately, the issue is whether the window is designed to withstand the pressure differential of cabin to space.
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Why are you required to commit to a full stop landing if reverse thrust is selected? According to Airbus: ‐ After the flight crew selects reverse thrust, they must perform a full stop landing. Does it really make sense to have this limitation, and why? What happens if you realise there's not enough space to land, and you've still got adequate speed? <Q> The biggest problem is that thrust reversers take time to move. <S> During that time they are still producing reverse thrust (even if only at idle) and slowing you down. <S> They must all completely close before you get forward thrust and can add power to start accelerating again. <S> Then, what happens if they don't stow, or only part of them stow? <S> Now you've used up valuable runway that could have been used to stop (or at least slow down more) and are no longer in a position to takeoff from. <S> The consequences can be pretty severe. <A> Once they're out, you're committed to stop because you don't know if, and <S> how quickly/symmetrically, they'll stow. <S> Even with a long, long runway, if you push up the power and one reverser is still out, you're going off the side -- one side of the aircraft is producing forward thrust, the other is producing reverse thrust, you're done! <S> All the safety interlocks & features in the TR's are all about preventing uncommanded deployment -- since that might well be unsurvivable in flight. <S> But when you HAVE commanded the deployment, those safety features are all satisfied. <S> There isn't any similar level of engineering to guarantee that they stow, and do so simultaneously, because you're simply TOLD, don't try to take off once the TR's are out. <S> If one fails to stow at the end of the landing roll, the effect is pretty minimal with the power at idle and the aircraft at or near taxi speed, so in general there aren't great issues with the TR's perhaps still out after you're done with them. <S> The one case where it's a grave issue is handled with a policy solution ("don't") rather than an engineering solution. <S> As far as realizing that you touched down too long and you need to take it back airborne rather than trying to stop, that IS possible... <S> right up until the point that you deploy the TR's. <S> Then you're committed. <A> Because if you do try to go around after the reversers deploy, you run the risk of them failing to retract - or, much worse, of just one of them failing to retract. <S> As happened on 11 February 1978, when a 737-200 flying Pacific Western Airlines Flight 314 touched down at an uncontrolled airport (Cranbrook/Canadian Rockies, CYXC) during a snowstorm, deployed its thrust reversers... and saw a snowplow further down the runway (Calgary ATC, in charge of the flight, screwed up their estimation of how long it would take to reach Cranbrook, and the runway was still in the middle of being plowed when Flight 314 landed). <S> During the resulting attempted go-around, the right thrust reverser restowed, but the left one did not. <S> The 737 cleared the snowplow, but it (the 737, not the snowplow) then, to quote the official accident report , ...climbed to 300 to 400 feet above the airfield, banked steeply to the left, lost height and side-slipped into the ground to the left of the runway. <S> This was despite the crew applying full right rudder and ailerons in an attempt to counteract the deployed left reverser. <S> 42 of the 49 on board were killed as a result. <A> If you landed on the dry lake bed at KEDW with over 15,000 ft of runway to work with, slowed down using thrust reversers and then closed them and attempted a takeoff roll <S> , it's possible <S> you could again get airborne. <S> Of course, this generally is not the case on a revenue flight where your landing rolls will exceed several thousand feet, depending on aircraft type, local conditions, etc. <S> you simply would not have enough runway left to attempt a second takeoff roll without a taxi back.
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Theoretically no, you could depart again, once the thrust reversers retract and properly stow, provided you have enough runway left to takeoff and obstacle clearance at the departure ends of the runway.
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What are the most popular areas to do private pilot flight training in the United States? Are there any statistics on the most popular states to do private pilot flight training in the USA or a similar measure? I know Florida is very well visited, but I was wondering if there were other states which also have high number of students. <Q> The FAA has a document on their website which breaks knowledge tests down by FSDO rather than state, and it gives a good idea of where the most training is taking place. <S> It is called: 2013 Airmen Knowledge Tests by Region and FSDO , and lists the following Regions/FSDO's as processing the most knowledge tests (in descending order) <S> 1 <S> : <S> Southern 28,333 <S> Orlando 9,996 South Florida <S> 5,958 Alabama & NW Florida <S> 4,680 Atlanta 3,882 Tampa 2,504 Western Pacific <S> 18,416 <S> Scottsdale 6,053 Riverside 1,556 San Diego 1,463 Sacramento 1,460 Long Beach 1,327 Fresno 1,270 Los Angeles 1,142 San Jose 1,121 <S> Southwest 15,943 Dallas 2,731 Fort Worth 2,581 Houston 2,438 Oklahoma City 2,347 <S> San Antonio 2,321 <S> Eastern 14,552 Richmond 1,956 Greensboro 1,366 Farmingdale 1,280 Philadelphia 1,198 New York City 1,069 Boston 1,041 <S> Great Lakes <S> 11,860 Fargo 2,120 Dupage 1,414 Indianapolis 1,358 Minneapolis 1,142 East Michigan 1,111 Northwest Mountain <S> 9,784 Denver 2,205 Portland 2,131 Salt Lake City 1,964 Seattle 1,611 Central 9,019 Nashville 4,293 <S> Wichita 1,304 <S> Alaskan 812 <S> 1 <S> To improve readability, all FSDO's with less than 1,000 tests have been removed. <S> See the source data for the complete list. <A> There are two popular areas: 1) Where you live. <S> Most pilots desiring to fly for fun train near their home and family, and 2) Where the weather is good. <S> aka somewhere down south, Arizona and Florida are the most popular. <S> Why? <S> Fewer no-fly days. <S> There is a reason that ERAU has branches in Florida and Arizona. <A> I used to train in the Phoenix area. <S> Very busy. <S> Lots of chinese, vietnamese, dutch, germans, englishmen etc. <S> (CAE Oxford, KLM Flight Academy (although I believe they recently ceased their training facility there) and many others. <S> I'm sure this will not satisfy as an answer since these are all CPL training facilities and not PPL. <S> Thought it would be interesting to share though. <S> Cheers.
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Based on this data, I would say that the areas surrounding the Orlando, Scottsdale, South Florida, Alabama & NW Florida, Nashville, and Atlanta FSDO's are the most popular training areas, with the Southern region being the most popular by far.
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Do rudder pedals slide or hinge? I am planning on making a pair of rudder pedals from scratch. I don't know whether they should be hinged, or slide forwards and backwards. On real aircraft, how do they work? Does it vary from plane to plane? <Q> If you're looking for simplicity for a homebuilt aircraft or simulator I'd go with hinged pedals pivoting at the floor similar to what you'll find on a Piper Cub (which can be made by welding tubes together into an I shape), or any number of similar floor-mounted designs: (As shown in the first picture, toe brakes can be easily retrofitted onto such a design, and as shown in the second you can mount square pedals on them if you want to, though the round bar has some advantages.) <A> Sliding pedals are very unusual - I do not know of a single aircraft which uses them. <S> It is also mechanically more complex and fragile - you would need to keep all those sliding lines clean, at a section of the aircraft where dirt is most common. <S> But there are three different ways to hinge the pedals. <S> The most common one is at the bottom, but they could also be mounted on a crossbar. <S> By using two crossbars, you get a parallelogram wich helps to keep the pedals at the same angle. <S> This picture shows the "cockpit" of the schooling glider SG-38, simply because it doesn't hide anything. <S> As you can see, the pedals sit at the ends of the parallelogram, and you could add another hinge at their base easily for activating brakes (which the SG-38 did not have). <S> Now you would have two degrees of freedom which make controlling two separate functions easy. <S> The third way is to hinge the pedals from the top. <S> This again helps to add a second degree of freedom, especially when the top hinged mechanism uses two parallel rods to again ensure a constant angle of the pedals, independent of their position relative to the hinge point. <A> On the Cessna's I've flown they both slide and pivot- <S> sliding directs the rudder, pivoting engages the respective wheel's brakes. <A> The gliders I've flown (Blanik L-23 and Grob 103) have hinged pedals with regards to controlling the rudder, and they slide closer or farther in tandem to adjust for different pilots' heights.
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I've never seen "sliding" rudder pedals in a light GA plane - though there may be such designs in transport aircraft, especially fly-by-wire planes.
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How can one enter an airliner without stairs or a jet bridge? I see that big planes (B737, A319 etc.) always need a staircase or a boarding tunnel in order for crew or passengers to enter the cabin since the position of the entry door is quite high (meters above the ground). What solutions are there if none of these options are available? (Except, obviously, for aircraft like DC-9's/MD-82 and 727's which had the rear entrance) How could the pilots get in? Is there some sort of manhole under the aircraft that can be opened to get inside with a sliding staircase or similar? Living in Africa, I have been to a couple of airstrips where these aircraft do land. Obviously all the airports had stairs but since we cope with some strange situations over here, the question came into my mind. What is the alternative should something go wrong and no traditional means be available to get in the plane? <Q> There are no rear entrances these days, but many smaller jets like the Avro-RJ, Bombardier CRJ series or Embraer regional jets have their own air-stair on the main (front left) door. <S> On the smaller planes the door are hinged at the bottom and the stair are part of the inner side of the door, on the larger ones there may be folding stairs stowed beside the door. <S> B737 can have those too, but it's optional, so many operators choose not to have them (and on second-hand aircraft the operator sometimes bother removing them, but rarely adding them back). <S> I've never heard of them on A320 family as it's a lot higher. <S> You can get always out using the emergency slides and in cockpit they have a rope to climb down through the side window (where it's too high to jump from it) in case the cockpit door can't be used (happens sometimes). <S> However the only way in is using stairs . <S> It's hard to imagine you wouldn't be able to scramble at least a ladder even at very remote landing strip where the plane has made an emergency landing. <S> Regular landing will obviously not be done to a place without regular stairs (unless the plane has integral airstairs, of course) and if it was emergency landing you need to bring in mechanics and fuel to get the plane out, brining a ladder is not much extra trouble. <S> Edit: As Kevin noted below, many aircraft have engineering access hatch in or behind nose wheel well. <S> Not an option for boarding passengers, but the crew can use it when they don't have stairs/ladder handy. <A> At Cairo West, a joint Egyptian-US military airfield, we once used a fork-lift with an empty pallet to get military personnel on and off a 747-200 when the stairs weren't available. <S> It took awhile. <S> That was the method sometimes used to get JFK on Air Force One (when that airplane was a 707 and never in public view, although one picture got out) to avoid him exacerbating his back troubles by walking up the stairs. <S> Also, unless modified, 747-100s and -200s can be entered and exited from the ground if you're reasonably fit. <S> At age 75 I could still do it, although I might groan a bit. <S> We used that means on occasion, usually when the stairs had been pulled away, and we needed to get someone into the airplane and didn't want the delay of getting the stairs. <S> Given these days of security concerns, I'm not comfortable with providing the details. <A> The air stairs are quite heavy though, so most airlines have made the business decision to remove them (to save money) and only operate out of airports that have appropriate ground facilities, including stairs. <S> If something happened and the stairs were not available on the ground, they would simply divert or reposition to an airport with adequate facilities. <A> In Canada's northern areas older large planes are used for freight. <S> The crew just bring along an aluminum ladder. <A> Very good answers but <S> this image from @Qantas94Heavy comment link is self explanatory!
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Some large aircraft (like Air Force One) have been specially modified to include air stairs so that they don't have to rely on equipment on the ground:
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Why are military and civil aircraft landing gear generally so different? Why do military aircraft have a lower landing gear than civilian? I have in mind the difference between a Lockheed C-130 Hercules and a Boeing or Airbus. The first possibility that jumps to mind is that one is more comfortable than the other, which is more robust. But would an aircraft designer reduce robustness to provide more comfort? <Q> There is no difference between civil and military aircraft. <S> Many military planes have civil variants like Lockheed C-130/ L-100 , other military planes are derived from civil ones, e.g. C-135 is B707. <S> The difference depends on where the wings and engines are placed. <S> All the aircraft actually have similar clearance from the ground. <S> Just on some the lowest point is fuselage, on others it's the engines hanging down from the wings and on propeller driven ones it is often the propellers. <S> Cargo planes (like C-130, C-5, An-124 or An-224) are often built with high wings, so the fuselage is lower and therefore easier to load. <S> This is also concern for regional airliners as they are designed to carry their own stairs. <S> That's why BAe146 , ATR-42 or Dash-8 are high-wing and other like Bombardier CRJ series <S> have tail-mounted engines so they can also be lower. <S> On the other hand low or mid-wing designs with wing-mounted engines have better aerodynamic properties, which is why that construction prevails for large airlines. <A> Easier to Load As stated earlier, this is your primary reason. <S> You have to be able to load in cargo from the ground. <S> If you want to get troops and vehicles in fast to somewhere with minimum equipment, you want to be able to roll them of the aircraft, and the lower the aircraft, the easier this is done. <S> Other considerations: Shorter gear is stronger <S> The longer you make the gear, the more it will bend. <S> Bad news if you're trying to land on rough ground. <S> More Cargo space <S> The shorter you make the gear, the less trouble you have finding space for it inside the aircraft, where you want to maximise the amount of space you have for cargo, especially for vehicles and the like. <S> The anatomy of a cargo aircraft is that they are typically hollow inside, unlike passenger aircraft where they fold up into the center section. <S> Landing gear is heavy Landing gear is very heavy, since its got to support the weight of the entire aircraft above. <S> The shorter you make it- <S> the lighter the aircraft gets. <S> Better use of ground effect <S> The low gear may bring the aircraft a little bit closer to the ground, maximising ground effect and lowering your landing speed, again very ideal for rough terrain. <S> Note: These don't only apply to military aircraft, but to a lot of commericial ones as well, since the benefits are the same. <S> Look at the Dash-8, ATR 42/72, BAe 146 along with the rear-engined planes, and they all try to do this for these reasons, although ease of cargo loading might not come first on the list. <A> For the aircraft you use as examples the aircraft height above the ground (landing gear height) is mostly a function of use-case and clearances. <S> For the Boeing and Airbus airplanes you mention, the gear need be long to accommodate the engines hanging under the wings as well as the minimum bank angle needed to avoid wing strikes. <S> On the other hand, the C-130 has the engines mounted up on a high wing and the aircraft needs to handle big slow heavy things like tanks being driven into the cargo. <S> The need of the tanks specifically probably mandates the interior floor be pretty close to the ground, or you might need extremely long ramps to for the tank to ascend (and these would pose their own problems). <A> C-130 Addendum <S> Purpose-designed for cargo - rather novel at the time back then, perhaps. <S> Look at WWII films of the C-47 or Berlin Airlift film of C-54 ' <S> s. <S> How the heck do they get anything in there? <S> Designed around a "standard truck bed height" floor and a "standard railroad box car" dimensions - 10' x 10'. <S> The short landing gear derives from the basic design goals. <S> Further, the wheels are in tandem - one behind the other vice side by side. <S> And the tires are fat. <S> These aid operating out of unimproved/dirt fields. <S> The leading tire "plows the way" so to speak for the rear tire. <S> Fat tires lowers the "per square foot" weight on the tires. <S> The longer you make the gear, the more it will bend. <S> Bad news if you're trying to land on rough ground. <S> Ironically the C-130 landing gear is wimpy when it comes to side loads. <S> It does not have adequate side-bracing. <S> Straight ahead, we can pretty much plop that puppy on the ground relatively aggressively. <S> But, during taxi, stopping while still in a turn is a write-up and requires maintenance inspection prior to flight. <S> The first possibility that jumps to mind is that one is more comfortable than the other, <S> The C-130 is designed for utility, by masochists. <S> It is painfully loud, too cold and too hot at the same time, vibrates like the inside of a jack hammer; and if the the prop synchro-phaser ever fails will drive you insane in short order. <A> The C-130 and turbo-prop commuter airliners (Embraer and Bombardier) have the engines in line with the bottom of the wing which is attached to the top of the fuselage. <S> Large airliners (Airbus and Boeing) have engines slung well under the wings which attach near the bottom of the fuselage. <S> The turbo props get a lot of clearance from the height of the fuselage while the jets rely on longer gear legs.
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The biggest factor in landing gear length is going to be how the engine(s) is/are mounted and ensuring they have clearance. Not the least because the civil and military transport aircraft are actually the same models .
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What defines a cycle on a jet engine? Is there a legal definition of a "cycle" on a jet engine? We must log the cycles, and some maintenance is determined by cycles. From my understanding, this is partially because of the thermal dynamics of an engine cooling and then reheating, and partially because full takeoff power is used. The "usual" time that you log a cycle is when an engine is started and the aircraft then takes off (using full rated takeoff power), but what about unusual situations like: Engine shutdown and restarted in flight Engine started, aircraft takes off, and then returns for a low pass or a touch and go: Would this be two cycles (does it depend on the amount of power used during the touch and go?)? Engine started and then shut down without a flight <Q> A cycle is a start to a shutdown. <S> Lets say there is a flight that is loaded with pax, bags, and fuel. <S> They push back and start both engines since the weather is good and their at an outstation. <S> As they taxi to the departure runway, BAM, ground calls up saying there is a groundstop for the hub and its going to be about 30 minutes. <S> The flight pulls into some empty ramps space, and shuts down both engines. <S> Groundstop lifts, both engines started again, and the flight departs. <S> After landing, pulling into the gate, and shutting down the engines, we can say that for this flight, each engine went through two cycles. <S> ALL of this info is logged and maintenance can access it. <S> With some of the newer engines and higher service packages, OEM <A> According to the FAA in AC33.70-1 : <S> (b) <S> The applicant should validate and maintain the accuracy of the engine flight cycle over the life of the design. <S> The extent of the validation depends on the approach taken in the development of the engine flight cycle. <S> For example, a conservative flight cycle where all the variables are placed at the most life damaging value would require minimum validation. <S> A flight cycle that attempts to accurately represent the actual flight profile, but is inherently less conservative, would require more extensive validation. <S> Applicants may apply further refinements to the engine flight cycle when significant field operational data is obtained. <A> I am an Aviation Maintenance student. <S> The way my instructor explained it to me was: any time that you exceed 70% RPM, you have just run an engine cycle. <S> It is more about acknowledging that the engines reached a certain temperature and was exposed to stresses that maintenance should know about. <S> Different engine manufacturers will probably have different definitions of a cycle. <A> Engine flight cycle. <S> The flight profile or combination of profiles on which the approved life is based. <S> To establish a safe life, the applicant needs to establish an appropriate flight profile (or combination of profiles) and consider the expected range of ambient conditions and operational variations to determine the service environment. <S> The engine flight cycles should include the various flight segments that describe a complete flight (or flights). <S> For example, for fixed wing aircraft applications this may include segments such as start, idle, taxi, takeoff, climb, cruise, approach, landing, thrust reverse and shutdown. <S> AC <S> No: <S> AC 33.70-1 <A> Refer to the engine manufacture they have received approval from the FAA for their engines. <S> On a TFE731 one engine cycle is one take off and landing which can be found in the LMM. <A> As far as the engine is started in ground and shutdown it is not considered as a cycle since no Aerodynamic forces/Loads are acting e.g. when engine is tested in Test cell it is not considered as a cycle. <S> In the case of IFSD it will be considered as a cycle as the engine went through most of the phases of a cycle.
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The cycle is one takeoff and landing , meaning engine start,climb,cruise,landing and shutdown.
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What's the difference between a balked landing and a go-around? Is there a difference between a balked landing and a go-around? If there is, what exactly is a balked landing? <Q> GO AROUND- Instructions for a pilot to abandon his/her approach to landing. <S> Additional instructions may follow. <S> Unless otherwise advised by ATC, a VFR aircraft or an aircraft conducting visual approach should overfly the runway while climbing to traffic pattern altitude and enter the traffic pattern via the crosswind leg. <S> A pilot on an IFR flight plan making an instrument approach should execute the published missed approach procedure or proceed as instructed by ATC; e.g., "Go around" (additional instructions if required). <S> (See LOW APPROACH.) <S> (See MISSED APPROACH.) <S> The ATP PTS also includes a Rejected Landing, which is what our simulator instructors refer to as a Balked Landing, and must be at or below 50 feet AGL. <S> It has the following note describing it in the PTS: <S> NOTE: <S> The maneuver may be combined with instrument, circling, or missed approach procedures, but instrument conditions need not be simulated below 100 feet above the runway. <S> This maneuver should be initiated approximately 50 feet above the runway or landing area and approximately over the runway threshold or as recommended by the FSB Report. <S> The pilot follows the same procedures for both of them by aborting the landing, cleaning up the airplane, and flying the appropriate procedure afterwards. <A> Almost everything I read says that a balked landing is the same thing as a go-around. <S> (Indeed, the wikipedia page for balked landing redirects to the 'go-around' page). <S> In these cases, a balked landing, also known as a go-around, creates a better opportunity for a near perfect landing [ src ] <S> This thread mentions that they are the same as a go-around, but can include when the wheels briefly touch down. <S> However, I did find one <S> slightly dissenting opinion <S> here : <S> I don’t know of an official definition of a balked landing that makes it different from a go-around. <S> The way the balked landing term is generally used is that the actual landing procedure has begun and must be aborted. <S> A go-around generally begins at a higher altitude and lacks the urgency of the balked landing. <S> So, in summary, they're pretty much the same thing (or exactly the same thing), but some people differentiate the two by the altitude the procedure begins at. <A> While there is no distinction between balked landing <-> go arround, "technically" you will find in regulations a difference between balked landing and missed approach . <S> Missed Approach climb is defined as a go-around from at or above DH (possibly with one engine inoperative). <S> CS(Part) <S> 25 assumes required gradient on: <S> Go-around thrust on remaining engines <S> Landing gear retracted Approach flap set <S> Balked Landing climb is a go-around from below DH, possibly in the flare (note that all engines are assumed available). <S> CS (Part) <S> 25 assumes required gradient on : <S> Go-around thrust all engines <S> Landing gear down <S> Landing flap set <A> Balked Landing is a very low altitude Go-Around. <S> Not a term you would use with ATC, they don't care. <S> It's a term found in certain aircraft flight manuals and requires a slightly different procedure than a normal go-around, similar to a rejected landing. <S> Usually wheel touchdown is likely and you must verify airspeed increasing past a certain point (safe flap retract speed) and positive rate of climb before de-configuring, otherwise you risk touching down with the gear in transit or slamming down because of loss of lift from flaps/slats. <A> The missed approach procedure is published with considering the terrain in the area. <S> It is calculated that an aircraft can safely go around clearing the terrain if it starts go-around at the DH. <S> If the aircraft descents below DH, and decides to go around things go different. <S> Because now it starts the procedure approximately 200' below and also 1NM ahead of the published missed approach procedure. <S> This is a balked landing, and has to be handled with more care. <S> to carry out the engine out SID after balked landing in low visibility conditions also has to be considered <A> A balked landing is a go around in the landing configuration: flaps and slats at the required setting, gear down, etc. <S> A go around can be performed in any aircraft configuration. <A> Balked Landing – A discontinued landing attempt. <S> Term is often used in conjunction with aircraft configuration or performance assessment, as in “Balked landing climb gradient”. <S> Also referred to as “Go-Around” <A> Balked landingd it is not a simple go around or missed aproach landing, in a balked landing <S> the airplane must be able to maintain a steady gradient of climb of at least (different for each airplane)with: <S> (1) Not more than the power that is available on each engine eight seconds after initiation of movement of the power controls from minimum flight-idle position; (2) <S> The landing gear extended; (3) <S> The wing flaps in the landing position; and (4) <S> A climb speed equal to VREF, available: http://www.risingup.com/fars/info/part23-77-FAR.shtml <A> A baulked landing and a go around are very much TWO different procedures. <S> A baulked landing only happens on very short final if for instance the captain isn’t happy with what they see. <S> The procedure is simply to pitch nose up and simultaneously apply full power. <S> The wheels may touch the runway but that is fine. <S> This is an escape maneuver to quickly get away from the ground. <S> Once the aircraft is in a stabilized climb, the go around procedure can be applied. <S> This is initiated by a term like “Go around, flaps” which helps bring both pilots back into the loop. <S> A go around procedure always follows a baulked landing, but a go around procedure can of course be flown on its own.
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A balked landing – also known as a go-around, is an aborted landing of an aircraft that is on final approach … for landing [ src ] The only term in the Pilot Controller Glossary is Go Around, so should technically be the only term used, at least when communicating with ATC:
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How does having multiple ATC towers affect airport operations? I know there are airports with more than one ATC Tower, though I only know it from my own country (SCHIPHOL - EHAM). This airport has two towers called Tower-Center and Tower-West. Tower-West is built because of a sixth runway (18R - 36L), that wasn't clearly visible from Tower-Center. (They found this out after completion of the sixth runway.) How common is it an airport decides to built a second tower, and are there a certain rules or limitations before the decision can be made? Next to that; what are the practical consequences for pilots and ATC's? Do they not only switch between startup- and ground-controllers but also between several ground controllers? <Q> Sometimes they have different towers for ground control frequencies and tower control frequencies, and the position of the tower is optimized for the appropriate task. <S> For very large airports, they may need towers in different areas of the airport to properly see airplanes at each runway. <S> As far as practical consequences it doesn't matter much whether they have one or more towers. <S> At very busy airports they split up the tower/ground controllers/frequencies because one person can only control so many airplanes at a time. <S> For instance, there may be one controller for the North runway and one for the South runway. <S> In this case, there could be only one ground controller, or there may be two or even more, depending on the complexity of the ground operations. <S> With multiple ground frequencies, if you need to taxi from one controlled area to another, the controller that you are talking to will tell you to hold short of a particular point and contact ground on the other frequency. <S> Once you contact the second controller, they will clear you to continue taxiing. <S> In short, it is very specific to the local conditions, and they do what they have to in order to properly control the traffic. <A> How common is it <S> an airport decides to built a second tower, and are there a certain rules or limitations before the decision can be made? <S> It's fairly common where there's more than one runway, and it has a lot to do with visibility from the ATC Tower cab. <S> Under optimal conditions, ATC would need to be able to see all airfield paved areas with a minimum Line of Sight angle which varies from regulator to regulator. <S> This can sometimes prove difficult for runway thresholds if their elevation and distance to the tower location make this angle too low. <S> Big terminal buildings (or any other building for that matter) can also be an obstacle to visibility, especially on apron areas. <S> The decision to go for more than one tower, from an operational point of view, comes down basically to the need to have control of all airfield areas. <S> Building an additional control tower is not only very costly, but also adds complexity to ground operations which is always an undesirable (albeit inevitable) effect. <S> In some airports apron control is transferred not to another tower, but to follow me personnel under the supervision of ATC, for example. <S> As for the practical consequences for pilots and ATC, Lnafziger has done a better job answering your question than I could have hoped to achieve. <A> These days building more than one ATC tower in an airport is not advisable because of availability of many technological tools that help you to extend your surveillances over the far corner of the airport and prevent runway incursion. <S> This is called A-SMGCS (Advanced-Surface Movement Guidance and Control System) depending on the need of airports there are 4 levels using radar and modern surveillance plus data links techniques for making visible aircraft and vehicles, <S> I believe that is cheaper and less complex than making a new tower which in its turn would be an obstacle for flight operation.
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At larger airports it is fairly common to have more than one tower, but it all comes down to how well the tower controllers can see airplanes.
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Is rebooting the computer normal before/during flights? On a recent flight the captain made an announcement at the gate that they need to reboot the computer as somethings aren't working, and rebooting usually solves the problem. After posting this on twitter I got a replying saying that most planes have 3 computers and rebooting during flight is common. What are the reasons for reboot? For me it sounds like a software/computer that isn't tested thoroughly instead. <Q> Today's modern airplanes have many computers, and sometimes things get out of sync and don't communicate properly. <S> During the preflight checks, we check each system according to the recommendations of the manufacturer, and occasionally one of the checks will not pass correctly. <S> Depending on the system, when a check fails, rebooting the computer may be an option to see if it fixes it (similar to rebooting your home computer). <S> Other times, the issue is the communication protocol between two (or more) different computers. <S> Often times in this case, the entire airplane must be powered down in order to reset them all at the same time. <S> Since these tests aren't performed in the air, the problem usually doesn't crop up there. <S> In the vast majority of cases it isn't a safety critical item that we are dealing with (where the software testing is more thorough), but rather a monitoring system. <S> The safety critical items (like flight control software, etc.) will have multiple redundant systems and often have different versions of software on at least one of the computers "just in case". <S> Generally the flight crew won't tell the passengers when they need to "reboot" a computer unless we have to power down the entire airplane. <S> That's very noticeable and will cause some people to worry <S> so we like to give you a heads up before all of the lights go out and the air conditioning system shuts down. <S> That of course is up to the discretion of the flight crew though. <A> This was probably the captain trying to be funny and use relatable terms for what was going on. <S> In the EMB-145 <S> occasionally the ACARS would stop working and you could re-initialize that during flight. <S> The actual computer systems, however, could be reset <S> but this is something you'd only do on the ground as it either involved powering down the aircraft or getting MX out to open some panels and pull breakers / flip switches. <S> The few things that could be reset in the air by pulling and resetting a breaker were things like FMS, ACARS and the autopilot, which we would do when directed by the QRH or MX and perhaps this is what the captain was referring to. <A> Airliners are more complex, so I suppose it's possible. <S> On light aircraft, I've never heard of anyone having to reboot the computer (glass panel systems). <S> Sometimes we have to reboot our radios, and I've had to reboot FADEC (engine control) <S> computers before though. <A> Is rebooting the computer normal before/during flights? <S> It is wrong to write about "the computer" because a modern airliner probably contains hundreds or thousands of microprocessors and microcontrollers. <S> For example, the seat-back information and entertainment systems almost certainly each contain a microprocessor running some embedded operating system. <S> Each of the items of avionics equipment will contain several microprocessors, probably running real-time operating systems that are certified for use in aircraft. <S> Unlike a typical desktop computer, I'm pretty certain that critical systems on board an airliner are designed to handle multiple failures and keep working, in a degraded or fall-back mode if necessary. <S> most planes have 3 computers As I wrote above, large commercial airliners will likely have hundreds or thousands of microprocessors and microcontrollers. <S> The "3 computer" idea comes from the use of redundancy in each critical system. <S> Each subsystem may have two, three or more independently created systems with different hardware and with software written by different teams, each doing the same job. <S> An arbitration system compares the outputs and if one of three disagrees, the other two get to determine what happens. <S> conclusion <S> No, it's not normal part of the pre-flight checklist for the pilot to walk round to the rear of the aircraft, flip a big red switch off and on again and wait for a start-up jingle. <S> If the in-flight movie system isn't working, I'd expect someone will try turning it off and on again. <S> If there is a problem with one of the many independent systems in the cockpit, I'd guess it's plausible, in some cases, the pilot or engineer's checklists for the problem include some kind of reset operation.
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Critical avionics systems have the ability to reset themselves if they detect problems - for example they will have hardware-based watchdog timers that will restart a processor or system that isn't showing signs of running it's software normally.
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What is the dark spot visible below the cockpit on A-10s? On most A-10s I have seen, the area under the cockpit is darker than the rest of the plane. Is there a reason for this? <Q> It's a false cockpit, a type of camouflage patented in 1980 by Keith Ferris, a US artist and camouflage designer. <S> From some angles, it makes it difficult to determine the orientation of the aircraft. <S> The Canadians were the first to apply it; pictured is a CF-18 Hornet with one: <S> Notice how at a glance, it takes a second to realize the Hornet is inverted and pulling towards the ground. <S> During dogfights this can be enough to make opposing pilots think the aircraft is going a different direction. <S> It might not seem like much in a photo, or if you're watching an aircraft fly past at an air show or airport. <S> In the stress of combat while pulling extra Gs it's more than enough to confuse or delay a reaction. <S> For the air to ground mission, this is particularly important. <S> If an A-10 encountered antiaircraft fire or an enemy aircraft it would have to rely on its own agility to escape or gain the upper hand. <S> Other nations have adopted this technique — I've seen French and Russian types, and possibly Gripens of some air force. <S> As far as I know, the A-10 is the only US aircraft regularly camouflaged in this way. <A> Also used by the South African Air Force on its Gripen fighter aircraft and, before that, its Cheetah (upgraded Mirage) fighter aircraft. <S> An image of a South African Air Force Gripen C, showing the false cockpit on the bottom: By Brent <S> Best And an image of a South African Air Force Cheetah C showing the same: <S> By Christo Crous Note the diamond-shape on the bottom of the Cheetah C. A similar pattern is painted on the top surface of the SA Air Force's Gripens. <S> This reportedly helps create more uncertainty when seen in brief glimpses during combat, similar to the way dazzle camouflage on ships in WWI worked. <S> This is an illustration, taken from a flight sim, of what the effect looks like on a Cheetah C with a mostly 'clean' configuration (no drop tanks or bombs): South African Air Force fighter aircraft have used the false cockpit and diamond-shape camouflage ideas since the last 1980s, after proving the concepts through testing. <A> Wikipedia cites the biological concept of automimicry , or intraspecific mimicry, where a species develops a part of the body which appears similar to another part, e.g. a tail appearing like a head, so that predators become confused as to the orientation or direction of movement of their prey. <S> See also the similar concept of dazzle camouflage or razzle dazzle used on combat and merchant naval ships during World War I. <A> There was an article on this in Aerospace magazine way back in the late 1980s (I still have a photocopy somewhere). <S> They called it Visual Stealth. <S> The article included the long history, includingusing lights to illuminate the darker regions of aircraft when viewed from the ground. <S> One picture I saw clearly showed a 'tail shadow' painted on the bottomof an F16. <S> False cockpits were common, as were painting the tops and bottoms different colors. <S> Ground Strike aircraft would commonly have yellows and brown camouflage, white in the winter (Germany). <S> The Navy was using blues andgrays, with the tail squadron markings rather dull.
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The intention is to create momentary uncertainty as to which direction an aircraft may turn, both for air-to-air encounters against other aircraft and when doing low-level manoeuvring in the ground-attack role. As per egid's answer, this technological form of automimicry ideally helps to degrade an enemy's capability to successfully attack an A-10C (or similarly painted aircraft or vehicle).
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How does an A330 detect stall without airspeed? On Air France 447 the crew had experienced complete failure of the pitot static system, which meant they lost their readings on their airspeed indicators, but according to the Mayday / Air Crash Investigations episode the aircraft had detected that the plane was about to enter an aerodynamic stall and the stall warning systems were activated just before the crash. How did the A330 in question detect that the plane was on the verge of stalling without the airspeed indicators working? <Q> Stalls occur based on a wing's angle of attack rather than the aircraft's airspeed. <S> (In fact, one of the basic facts that all pilots learn in their initial training is that an airplane can stall at any airspeed). <S> The A330 measures angle of attack using vanes mounted on the fuselage: <S> However, below 60 knots, these vanes become ineffective . <S> During the AF447 accident, the stall warning only engaged intermittently because the computers detected that the airspeed readings from the blocked pitot tubes were invalid, and therefore silenced the stall warning system. <S> Furthermore, because of the lack of valid airspeed data, AF447 was no longer in normal law (and therefore had no automated angle-of-attack protection), a fact which the pilots may not have been aware of. <S> By the time the deicing equipment had cleared the pitot tubes, the aircraft was at such an extreme pitch that airspeed indications were still considered invalid, and the stall warning system did not activate. <S> The computers only activated the stall warning system when the crew pitched down, which brought valid airspeed data back into the cockpit. <S> An Airbus press release suggests that this may have contributed to the accident: <S> We also note that the aircraft, or more specifically the design of the stalling warning system, misled the pilots: each time they reacted appropriately, the alarm triggered inside the cockpit, as though they were reacting wrongly. <S> Conversely, each time the pilots pitched up the plane, the alarm shut off, preventing a proper diagnosis of the situation. <S> (Emphasis mine) <A> Aircraft can stall at any airspeed , the only real indicator for a stall is an angle of attack indicator. <S> This is because weight, icing, flaps, G-forces being pulled, and speed all effect the aircraft's stall speed. <S> Although the other instruments had failed, the angle of attack meter was still functioning, though not very well. <A> To backup flyingfisch, the angle of attack (AoA) sensor is the only sensor used to determine aural stall warning. <S> The AoA sensors were operating correctly in the case of AF447. <S> The failure mode of sensors due to ice crystal icing is typically limited to those probes which collect by way of geometry such as pitot and TAT probes. <S> Static ports and alpha probes seem unaffected. <S> The aural Stall warning system in Alternate law is purely a limit AoA, and that limit is primarily determined by Mach; it reduces significantly at high mach due to compressibility. <S> For AF447, the stall warnings stopped when the limit of the AoA probes were exceeded. <S> This was presumably due to a validity checking algorithm of the system to discount extreme AoA beyond which an airliner would never conceivably achieve in its lifetime whilst airborne. <S> Although in their case, that AoA was actually correct and the aural stall warning should never have ceased. <S> As AoA probes become increasingly inaccurate beyond certain angles, some manufacturer s choose to temporarily derive AoA from other sources such as inertials.
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Most large aircraft, including the A330, have angle of attack indicators that detect the high angle of attack which precedes a stall.
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What do winglets do to increase aircraft performance? It seems like a lot of the newer airliners have winglets or wing fences. How do they improve aircraft performance? <Q> they reduce the wingtip vortex and the associated drag by deflecting the air that wants to escape over the tip back down ( source: wikipedia ) <A> Wing generates lift by creating area of higher pressure below and area of lower pressure above. <S> At the wing tip, some air flows around the tip, reducing the pressure differential and thus the efficiency of the wing. <S> This is called transverse flow. <S> The wing tip reduces this flow, thus improving the efficiency. <S> The effect of wing tip is actually similar to making the wing a bit longer, but since the wing tip does not produce lift itself, it is less stressed and therefore can be lighter, even though the extension would be about 1/3 shorter for comparable efficiency. <A> Winglets, raked wingtips, fences, sharklets all do the same thing; reduce drag. <S> When the wing is working hard (high AoA), it will produce a lot of this kind of drag since vortecies of all kinds will be stronger. <S> Winglets makes the passage of air from the bottom of the wing to the lower pressure top of the wing more difficult, thus reducing induced drag. <S> The big manufacturers explored offering winglet retrofit kits to their customers but at the time, it wasn't economical since fuel was so cheap. <S> These days, however, the retrofits pay for themselves fairly quickly even on airplanes wings that have a fairly high aspect ratio. <S> Every 737/757/767 guy that I talk to says they get in the neighbor hood of a 4-6% boost in fuel savings. <S> On an tangentially related topic, the hump from the satellite internet antennas has a negligible impact on performance, less than 1% according to the few guys that I talked to. <A>
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Basically what happens with an airplane without a wingtip is the high pressure area comes over the lower pressure area and creates a giant vortex called a wing tip vortex and the winglet reduces the strength of the vortex reduces drag, increasing lift, and increasing the aircrafts range.
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Is a propeller a wing? An aviation expert claimed to me that a propeller is a wing. While I understand that propellers use similar principles to generate force, it muddied the definition of a rotary wing aircraft vs a fixed wing aircraft. If the propeller of a fixed wing aircraft is considered a wing, what is the distinction between the two? Is it how much surface area each type of wing works on? Is it the direction of force? <Q> I think most people would say the answer is no . <S> Consider the dictionary.com definition as it relates to Aeronautics: 9. <S> Aeronautics . <S> a. one of a pair of airfoils attached transversely to the fuselage of an aircraft and providing lift. <S> b. <S> both airfoils, taken collectively. <S> The wings are the big airfoils which are responsible for generating most of the vertical lift. <S> A colloquial test of this definition would be to grab a CFI and ask him/her to "point out the wings on this airplane to me. <S> " They won't point out the propeller. <S> ( Not a scientific experiment ) <S> However, both wings and propellers are airfoils (and so are the other wing-like surfaces such as the vertical and horizontal stabilizers). <S> You might get some disagreement about whether those other surfaces are wings, but I believe the answer is still no. <S> There is nothing to be gained by calling them wings, and only leads to ambiguity. <S> We already have a word which describes lifting surfaces in-general, and again, it's airfoil . <A> Is a propeller a wing? <S> Maybe. <S> It depends on how pedantic you feel like being about your definitions. <S> A propeller is certainly an airfoil (usually several of them - each blade is an airfoil, and you can have one blade , two, three, four, or more attached to a hub). <S> A wing is also an airfoil. <S> Aerodynamically a wing and a propeller function the same way <S> : Air moves over the surface of the airfoil(s), producing "lift". <S> In the case of the wing the lift is mainly vertical and we call it "lift", while in the case of a propeller it's mainly horizontal and we call the resulting force "thrust" instead. <S> My two cents, ignoring all the dictionary pedantry? <S> Why? <S> Simple: <S> If I'm flying along and my propeller magically vanishes <S> I'm now flying a really inefficient glider. <S> My day is ruined and when I catch the guy with the genie-in-a-lamp who wished my propeller away I'll probably beat them up, but I have a fair chance of putting the aircraft on the ground without killing myself or anyone else. <S> If I'm flying along and my right wing magically vanishes the genie-posessing miscreant is safe as I'm almost certainly going to die. <S> All the lift from the remaining wing is going to try to flip the aircraft over, and I'm nowhere near skilled enough to <S> keep control with a missing wing and land safely . <A> An aviation expert reminded me that a propeller is a wing. <S> This is not false- <S> a wing generates lift by creating a pressure difference, in the same way a propeller does. <S> Wing typically refers to the structure lifting the main weight of the aircraft, while a propeller generates thrust, so from definition it's probably incorrect, from a theoretical standpoint it's the same principle. <S> While I understand that propellers use similar principles to generate force, it muddied the definition of a rotary wing aircraft vs a fixed wing aircraft. <S> A fixed wing aircraft will move at speed to generate sufficient lift to get airborne. <S> A helicopter will be able to lift off vertically by spinning the blades quickly enough, which will have the same effect as moving forward. <S> If the propeller of a fixed wing aircraft is considered a wing, what is the distinction between the two? <S> Is it how much surface area each type of wing works on? <S> Is it the direction of force? <S> Propeller thrust is directed forwards. <S> In level flight it contributes very little to lifting the plane up- <S> that's left to the wings to do. <S> Rotary wing aircraft's blades do really work as a propeller: By increasing the angle of attack on one side, you generate more thrust, and the helicopter flies in the direction you want it to, since there's a force vector in that direction. <S> (source: tiscali.co.uk ) <S> Distinction between the two: Rotorcraft generate the thrust to lift off themselves. <S> A propeller generates the thrust (and in turn speed) necessary to create lift over fixed surfaces. <A> Since no one else mentioned this, I thought I would. <S> Wilbur Wright, of the Wright brothers, said that a propeller was nothing more than a twisted wing. <S> If you accept his analogy, then the twisted wings that compose a propeller are clearly specialized wings, but they do generate a differential in air pressure above/in front of and below/behind as the surface moves through the air. <S> That is what a wing does. <A> When one thinks with respect to plane, things are a lot less "muddy". <S> Forget about definitions and rote and focus on what the function is. <S> First, while airborne, the only thing with respect to ground is gravity. <S> Everything else is dependent on orientation of the aircraft. <S> This is not muddy, it is actually a crucial step in becoming a better pilot. <S> So, starting with straight and level flight, it is obvious what is the wing (lift) and what is the propeller (thrust). <S> Now pitch up, add power and climb. <S> Yes, the propeller is now helping you climb as well as maintaining airspeed. <S> Is it now called a wing? <S> No, it is still out in front of the plane, so, with respect to plane, it is still the propeller! <S> The key is to draw the thrust vector, then break it down to vertical and horizontal components. <S> The propeller is helping lift the plane. <S> Now rotary wing aircraft. <S> All lift is provided by spinning the rotor, and forward motion too! <S> So it is both wing and propeller. <S> Birds have learned this trick as well! <S> So do not worry about muddy, take what you need and fly.
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A propeller is an airfoil, but it is not a wing.
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Is a wind speed of 150 km/h dangerous during a flight in an Airbus A321? I am just curious about this... during one flight on Airbus A321 we experienced turbulence and the pilot told us that the wind speed is 150 km/h, so we won't get drinks and snacks due to safety reasons. The question is: Was that wind speed 'normal' or 'dangerous'? What could happen? <Q> For example, in the wintertime it is not uncommon to find a strong core of fast winds embedded within the polar jetstream. <S> We term this windspeed maximum a 'jet streak'. <S> There are a couple of meteorological phenomena associated around these jetstreaks, such as regions of ascent and descent in the entrance and exit regions of the jetstreak and often times turbulence in the periphery. <S> You'll also find regions of turbulence on the lateral extent of the jetstream (polar side in particular). <S> Lastly, if you are flying at an angle to the jetstream or perpendicular to it, you will often experience changing wind direction along with speed, and this can be turbulent. <S> There is nothing dangerous about that wind speed alone. <S> What likely happened is that other airplanes were reporting turbulence and the pilots were being cautious with you and just offered that wind speed up as an easily understood number to justify the precaution. <A> It's not unusual for aircraft to experience a lot of wind at altitude. <S> In fact, there's a website dedicated to speed records- <S> all of those shown would be impossible without the help of the wind boosting the aircraft in addition to its normal speed. <S> Many people have unknowingly travelled at a velocity faster than the speed of sound on the ground when crossing the Atlantic. <S> While I'm not too familiar with it, I think that jetstreams and the like have a tendency to develop more air pockets and turbulence than calm air, including clear air turbulence , where there are no visual cues before the turbulence hits. <S> Many incidents happen when people are unprepared for a bounce at cruise altitude, probably hence the pilots decision. <S> A broken ankle is not unheard of. <S> As for catastrophic consequences, they are very rare. <S> Typically, the pilot will slow the aircraft down a little to reduce shaking and stress on the airframe. <S> Here's an incident on a Cathay Pacific 747 around a month ago, midflight: <S> Passengers reported the turbulence appeared to have lasted for about 2 minutes, at the time the fasten seat belt signs were not illuminated, passengers and cabin crew were moving through the cabin, when the aircraft suddenly and unexpectedly jolted throwing passengers and cabin crew to the ceiling causing damage to ceiling panels and overhead lockers. <S> Aviation Herald <A> To put wind speed in perspective (further to the previous remark that 150 km/h is not fast at altitude): The speed of the Jet Stream is typically 100 kts (185.2 km/h) but can reach 200 kts (370.4 km/h) over North America and Europe in the winter. <S> Speeds of 300 kts (555.6 km/h) are not unheard of, particularly over south-east Asia. <S> Aircraft flying west-east will try to exploit the Jet Stream to increase ground speed and, similarly, aircraft flying East-West will plan to avoid the Jet Stream.
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High windspeeds themselves are not a problem, but the environment surrounding them may be.
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Aviation ebook for beginners? I'm new to aviation but I am very passionate about it. I'm just 14 years old, so please help me in finding a good e-book about aviation for free. I don't know how to search with Google about it. <Q> Although this is a question based on opinion, it might perhaps have some value as a community wiki <S> so I've marked this 'answer' as such. <S> I also borrowed one of Manfred's links. <S> Feel free to append stuff to the list. <S> There are also a number of other handbooks there which are great reads. <S> To be honest, I find this the best introductory book I know, free or otherwise. <S> If you're out for a good reference book, something like Anderson's Introduction to Flight will be good, but bear in mind <S> this is hardly an easy read but does cover virtually everything you will need to know. <S> An older edition seems to be available online. <A> Aviation is a pretty complicated topic and can get very overwhelming very quickly, so it's not easy to locate something specifically. <S> eBooks however are not too easy to find, since you'll get the full load of manuals and regulatory documents in the search. <S> You might find something (including the ordinary print books below) by searching for book_name filetype:pdf in google. <S> If you're out for a good reference book, something like Anderson's Introduction to Flight will be good, but bear in mind <S> this is hardly an easy read but does cover virtually everything you will need to know. <S> An older edition seems to be available online. <S> There are plenty of books on flight simulation, which is often a great place to start. <S> A fantastic one I picked up with lots of facts and stuff was Flight Simulator X for Pilots written by Van West and Lane-Cummings. <S> This covers everything from navigations, maps and handling the aircraft. <S> There are a lot of similar stuff on websites and youtube as well. <S> There are plenty of websites on model aircraft building and drones. <S> Less theory and more practise, but anyway interesting and educational. <S> There are plenty of pilot blogs around, where you can read lots of good stuff. <S> I could also suggest that you join the edX free online course given by Delft University of Technology in Aeronautical Engineering . <S> You get a certificate at the end as well if I'm not wrong, and it should give you a decent introduction if you're able to keep up with it :) <S> Top 20 technical university and the largest faculty in Europe. <A> Sporty's ground school course is pretty helpful, you can get it for free if you can get yourself on an EAA Young Eagles flight. <S> I am not sure about ebooks, but you can find copies of these books on eBay or Amazon. <S> As the Pro Flies (John R. Hoyt) <S> Stick and Rudder (Wolfgang Langewiesche) <S> General interesting aviation books Janes <S> All the World's Aircraft Janes Aircraft Recognition Guide A Field Guide to Airplanes, Third Edition (M. R. Montgomery)
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In terms of free download, I can definitely recommend the FAA Airplane Flying Handbook which can be found on the FAA web site.
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Is it possible for a modern commercial airliner to stop being tracked without substantial mechanical failure? I was speaking to someone about the MH370 incident , and they suggested that a hijacker could turn off the device that sends the plane's current position, resulting in the appearance of a catastrophic midair failure. I assume that such functionality could not be turned off, but I could be wrong. Is there any way that this could be done? Could an aircraft's internal tracking systems be "turned off" midair, and also not be located by external tracking like radar? <Q> The device you are talking about is called a transponder . <S> This is a device that listens for a signal (an interrogation) and responds with information about the airplane including an ATC assigned code, altitude information and additional aircraft info for certain equipment. <S> There are 2 ways ATC watches airplanes: <S> Primary Radar Secondary Surveillance Radar <S> The transponder is interrogated by the Secondary radar and the response is listened for. <S> Even with no transponder, the aircraft can still be tracked by primary radar. <S> This is just a normal radar that is good at seeing airplane sized objects and not so great at seeing weather and can occasionally spot a large flock of birds. <S> The primary radar is what provides the "blip" on radar and tracks the airplane. <S> The datablock ATC has on the airplane comes from the secondary, so what ATC will see is a blip with no information. <S> Turning off the transponder is as simple as setting it to OFF or pulling a circuit breaker and yes, it can be selected OFF in flight, it is just a switch. <S> The problem with radar is that it only works so far from a radar transmitter and <S> the further away you are the higher <S> you must be to be seen by the radar. <S> Over the ocean away from land, you are going to be on the fringe of radar or out of radar contact completely and thus unable to be tracked directly by ATC (at this point, non-radar procedures such as position reporting and ETAs can be used to track positions). <S> The flight in question was apparently visible by a military radar before it disappeared from the scopes (it allegedly observed what appeared to be a turn back toward its origin). <A> With the proper knowledge of the aircraft systems almost anything can be turned off. <S> That's what we do at the end of almost every flight day. <S> Most of the communications systems can actually be turned off fairly easily, but the average person would not know how to do it. <S> Some are automatic and some are manual, and not all aircraft have all of them. <S> Most of them have a switch or can be controlled through the Flight Management System, but the ones that don't will have a circuit breaker designed to protect the system which may be pulled in order to deactivate the system. <A> As a B-737 pilot, I can tell you that ALL electrical components are wired into the electrical system to a specific electrical BUS. <S> It would not be hard to determine which BUS(S) run power to the associated component and therefore knowing which circuit breaker(s) to pull. <S> The ACARS that transmits our FOQA information can be disconnected on the BBJ I fly. <S> I assume it can be done in the B-777. <A> With today's locked cockpit policy it is extremely unlikely that hijackers would be able to turn off the transponder without pilots being able to set it to 7500, the code for unlawful interference, for at least a short while. <S> Because while the transponder can be turned off, the hijackers would have to get into the cockpit first. <S> The cockpit door can't be opened from cabin side. <S> Even if the stronger code is entered that will open the door (for cases when one pilot is incapacitated while the other is in the lavatory) the pilots still have some time to cancel the unlock request. <S> Therefore the hijackers would have to threaten with something to get the pilots unlock, but that would give the pilots time to provide some indication of the hijack to the ATC. <A> Another Boeing 777 on 12th July 2014 suffered smoke in the cockpit and cascading loss of electrical systems, navigation displays and Comms in the cockpit. <S> That was Continental Flight 201 which made an emergency landing on Midway island. <S> There are disputed claims that flight 201's transponder also failed during the emergency. <S> In the case of MH370 it is acknowledged that the ACARS suffered a power interruption prior to log-on requests. <S> It seems possible that the transponder was affected by whatever power interruption the ACARS suffered therefore <S> it is not an automatic assumption that the transponder and ACARS were turned off deliberately. <A> The plane's position is reported by ACARS and by the transponder. <S> MH370 lost ... ... <S> its Mode S transponder (shortly before 17:20:33 UTC) ... <S> ACARS <S> (somewhere between 17:07:49 - 17:37:29 UTC) ... and the SDU (somewhere between 17:07:49 - 17:37:29 UTC). <S> The SDU was repowered, however, at 18:25:27 UTC, when it logged onto theInmarsat satellite network again. <S> The first 2 items can be easily disabled in the cockpit. <S> The SDU can be disabled by either turning off the AES circuit breaker in the E&E bay or depowering the left main AC bus in the cockpit (which results in the collateral loss of various systems). <S> India has made it mandatory for aircraft flown by Indian operators to install a device reporting the aircraft's location every 15 minutes, thereby preventing the aircraft from disappearing: India makes its aircraft disappearance proof post MH370 incident <S> « <S> India has taken several steps to remove any possibility of the aircraft operated by its airlines disappearing without a trace in the aftermath of the shocking incident in March 2014 involving Malysia Airlines’ MH370. <S> It has made it mandatory for aircraft flown by Indian operators having a seating capacity of 19 passengers or takeoff weight of 45 tonnes or more to install a devise that will send location of the aircraft at 15 minute intervals. <S> The government had ordered airline companies to compulsorily install an automated aircraft tracking system (ATS) in all aircraft falling in the above categories. <S> The system will pass location information to ground stations even if the aircraft is flying over the oceans during long international flights throughout the duration of the flight. » <S> ( source )
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In airplanes like the 777, there are multiple ways that they communicate but all of them can be turned off (transponders, ACARS reports, CPDLC, ADS-B, radios, satellite phones, etc.).
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How do commercial pilots send distress signals? If a commercial jet is in trouble, how does a pilot send a signal indicating distress? Does it take long? For instance, behind reception desks in many institutions and executive offices, there's a hidden red button that, when pressed, calls security or the police. (I know this since I sit at such a desk.) Do commercial airliners have a similar switch, or do they need to radio in for help? What happens when such a transmission is received? <Q> Key the microphone and announce to the world Mayday, Mayday, Mayday , the flight's callsign, and a description of the emergency. <S> This is generally the way an emergency is declared, particularly for commercial (airline) service, as they're generally always in contact with an ATC facility Over the radio, to anyone monitoring the "emergency" frequency. <S> The VHF frequency 121.5MHz is reserved for aircraft emergency communication. <S> It is monitored at most air traffic control facilities, as well as by many airliners and other pilots with multiple radios in their aircraft. <S> If you're not able to make contact with the facility you're currently talking to in (1) above (or if you're not currently talking to an ATC facility). <S> Using the aircraft's transponder. <S> Three transponder codes are reserved for unusual/emergency situations: 7700 for general emergencies <S> 7600 <S> for loss of communication (radio failure) <S> 7500 for hijacking or other unlawful interference <S> All of these transponder codes alter the way the aircraft's radar target is displayed, to alert the controller to the possible problem (exactly how the display is modified depends on the radar equipment the controller has, and can range from additional text in the data block, like RDOF <S> (RaDiO Failure) for code <S> 7600 <S> to changing the color of the displayed block on newer systems. <S> Bret detailed some of the procedures around these codes in his answer , and more information is available from the FAA , though you'll have to dig through a few referenced documents to put it all together. <S> Note that sometimes the order of preference changes - For example if a pilot is being threatened by a hijacker they may quietly set their transponder code to 7500 without saying anything on the radio to alert the hijacker. <A> It depends on the type of distress, but generally the easiest way to communicate a problem is to use the radio and describe the situation. <S> However, there are some special transponder codes which will get the attention of any controller which has you on their radar screen. <S> 7500 indicates a hijacking <S> 7600 indicates a communications radio failure <S> 7700 indicates an emergency <S> What happens after switching to one of these beacon codes depends on the scenario. <S> In any of the cases, ATC will attempt to make contact with the aircraft. <S> In most cases, they will also try to vector other traffic away from the aircraft for everyone's safety (especially true in the case of a hijacking). <S> I assume your question is primarily asking about a hijacking scenario. <S> A recent, and very odd, example of 7500 being used is Ethiopian Airlines’ Flight 702 where the co-pilot actually hijacked the plane and squawked 7500. <S> Unfortunately, pilots don't always have the time to reset the transponder if they are engaged in a physical fight in the cockpit. <S> Also, the first step of the hijackers may be to turn off the transponder (this is what happened on 9/11), but if a controller is able to see the 7500 squawk, even briefly, it may help the controller understand what is happening if communications are lost, and to alert the military, if necessary. <S> As for the other two "distress" signals: <S> For 7600 (lost communications) they will probably ask "if you're receiving this, ident" or "if able, reset transponder code XXXX. <S> " If you comply with their request, it indicates that you can receive messages, but cannot transmit. <S> A tracon or center controller might ask you to ident to acknowledge further instructions (when you ident, your datablock flashes on their screen), or just watch your actions closely. <S> At towered airports, light-gun signals are used to give landing clearances when a pilot cannot receive radio communication. <S> For 7700 (emergency) they will try to inquire as to the state of the emergency and offer any assistance possible, such as providing you suggested headings or information about nearby airports. <A> There is another procedure which has not been mentioned although I doubt it's ever been used. <S> If you are lost and the radio has failed and the transponder has failed, flying at least 2 triangles is a recognised distress signal. <S> Since the transponder has failed, this does require that someone sees you on primary radar which is a long shot. <A> One incident that I heard (listening to ATC recordings) was a case where a pilot was suffering from hypoxia (lack of oxygen). <S> In this case, there was nothing wrong with the aircraft, but the pilot itself was incapacitated; so he could not initiate the normal procedures to declare an emergency. <S> He repeatedly keyed the mic, and then (in slurred speech) tried to communicate. <S> The ATC controller couldn't pick it up but luckily another pilot understood the situation and related to ATC. <S> I will try to find the transcript for the recording. <S> The ATC recording is available on YouTube.
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There are three common ways to send a distress signal (roughly in order of preference): Over the radio, to whoever you are currently talking to. If you're on with a tower controller in visual conditions, rocking your wings or flashing your landing light can be used to acknowledge instructions.
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Will the landing gear work mechanically in case of total power loss? In case of a total power failure in all the aircraft systems like engine failure and APU failure, would it be possible to use mechanical means (manually) to open the landing gear bay door and deploy the landing gear through mechanical means? I know it’s possible to glide the flight if the engines failed. But, wondering how they land. <Q> Not a real example, but this comes from the FAA , including some nice drawings around page 13-20: <S> The emergency extension system lowers the landing gear if the mainpower system fails. <S> There are numerous ways in which this is donedepending on the size and complexity of the aircraft. <S> Some aircrafthave an emergency release handle in the flight deck that is connectedthrough a mechanical linkage to the gear uplocks. <S> When the handle isoperated, it releases the uplocks and allows the gear to free-fall tothe extended position under the force created by gravity acting uponthe gear. <S> The popular small aircraft retraction system ..... uses a free-fall valve for emergency gear extension. <S> Activated from the flight deck,when the free-fall valve is opened, hydraulic fluid is allowed toflow from the gear-up side of the actuators to the gear-down side ofthe actuators, independent of the power pack. <S> Pressure holding thegear up is relieved, and the gear extends due to its weight. <S> Airmoving past the gear aids in the extension and helps push the gearinto the down-and-locked position. <S> Large and high performance aircraftare equipped with redundant hydraulic systems. <S> This makes emergencyextension less common since a different source of hydraulic power canbe selected if the gear does not function normally. <S> In some small aircraft, the design configuration makes emergencyextension of the gear by gravity and air loads alone impossible orimpractical. <S> Force of some kind must therefore be applied. <S> Manualextension systems, wherein <S> the pilot mechanically cranks the gearinto position, are common. <S> Consult the aircraft maintenance manualfor all emergency landing gear extension system descriptions ofoperation, performance standards, and emergency extension tests asrequired. <A> The rulebook for transport category aircraft says 14 CFR 25.729 c) <S> Emergency operation. <S> There must be an emergency means for extending the landing gear in the event of— (1) <S> Any reasonably probable failure in the normal retraction system; or (2) <S> The failure of any single source of hydraulic, electric, or equivalent energy supply. <A> The F-16 has an "emergency blow-down" reservoir containing approximately 3,000 psi gaseous nitrogen. <S> Hitting a switch will release this pressurized nitrogen into the hydraulic system dealing with the landing gear. <S> Ergo, hitting that switch will extend the gear, even with the engine off. <S> So <S> yeah, the landing gear will still work in the event of a complete power failure. <S> It has backup systems. <S> In the older A-4 Skyhawk, the landing gear retracted up and forward. <S> So, in the event of a hydraulic failure, if you could get the gear doors open, the airflow past the aircraft in flight would "drag" the gear down and aft and lock it into position. <S> I think that's a pretty slick design. <A> Almost all aircraft have some sort of backup system for getting the gear down. <S> On the planes I have owned they were: Manual hydraulic pumps to pressurize the system with a car jack type handle. <S> You sort of pumped the gear down. <S> Obviously does not work too well if the problem with gear system is a no fluid (blown line or seal). <S> Mechanical crank (21 turns to get down, 2 more to lock) that drove the gears if the electric motor died. <S> Good workout. <A> The Twin Comanche I used for my AMEL rating had an interesting mechanism. <S> First you had to disconnect the electric motor, then you stuck this handle into a hole and crank it as far as you can. <S> Then you shift it to a second hole (that becomes usable after the first one is used) and crank on it again until it stops. <S> Not something you get to try until you need it though. <S> Once you pull the disconnect it requires an A&P to restore the system to normal operation. <A> All aircraft have some kind of backup system. <S> As mentioned before- <S> Skyhawks Landing gear gets sucked <S> down.most of the other planes- just fall down thanks to gravity. <S> A lot of the airplanes (including military and some <S> civilian)- have a handle to open the bays mechanically (like in the 737) and the gear falls down and locks automatically with a mechanism that is independent of all hydraulic or electricity. <S> As for the big jets- <S> they have an amazing amount of backups. <S> And still- if in a 787 all your computers catch fire for some reason- <S> probably you wouldn't be able to extend your gear. <S> But then- even flying the plane would be a challenge, as the aircraft needs voltage for everything. <S> In this case, there is another backup for flying the plane using a special connection of direct wires from the stick to the flight control surfaces, powered by backup generators. <A> It all depends on the airplane in question. <S> Typically for small GA airplanes using an electro-hydraulic power pack for actuating the gear, they’re held retracted by hydraulic pressure. <S> If the system fails, the pressure goes to zero and the gear just drops down due to gravity. <S> I have time in the DA-42 and DA-62 twins and those airplanes use an alternate gear extension handle - basically an emergency valve which releases hydraulic pressure and allows the gear to drop down on their own. <S> Electrically powered landing gear can be typically lowered by means of a hand crank in the cockpit. <S> This is prominent on Mooneys and light Cessna twins. <S> Larger airplanes and jets may make use of emergency reservoirs of compressed nitrogen called blowdown bottles to provide emergency hydraulic pressure and extend the gear. <S> Typically the landing gear retraction jacks can be isolated from the main hydraulic system via a cockpit switch to prevent total loss of hydraulic fluid in the event of a leak. <S> It also removes the additional workload from emergency systems eg APU, RAT, etc. <S> for more critical flight control functions. <S> Transport category airplanes often have multiple layers of redundancy ie multiple hydraulic systems and power sources to get the plane down safe.
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Other aircraft use a non-mechanical back-up, such aspneumatic power, to unlatch the gear.
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What is airport tax used for? Since a very large sum of your ticket goes to airport tax, I was wondering how do they justify it and what is it used for? Take your tax paid on your ticket and multiply it with the number of seats on that airplane and you realise that, per flight, the airports are receiving a substantial amount. Is it all going to the government? This question is very 'general' and just to get a loose idea of what the tax goes for. To get detailed information of every country is unnecessarily complex. <Q> As jwenting pointed out, there isn't one "airport tax" - there's a whole bunch of them, and they're not all taxes (some are "fees"). <S> airlines.org has a list of the common ones you'll pay in the USA, and approximately what they cost you . <S> Broadly the taxes you're paying on airline tickets break down into two categories: Taxes that fund the Airport and Airway Trust Fund <S> These taxes pay for Air Traffic services (a little under half the operating butdget for ATC), maintenance of the airway infrastructure (radio navigational aids, RADAR sites, etc.), research and development to improve the airway infrastructure (e.g. NextGen ), and to fund the Airport Improvement Program (which provides grants to airports, mainly to implement safety improvements). <S> The actual tax categories themselves break down further (again, airlines.org's breakdown is excellent). <S> Fees that fund DHS programs <S> These are often called "security taxes", and include things like the "September 11 th fee", APHIS fees (for inspecting plants and livestock), and customs/immigration charges. <S> Note that all of these are technically fees , not taxes -- these are only levied when a flight is using the services the fee is funding (or at least that's what's supposed to happen. <S> In practice the airline is responsible for paying the appropriate fee as a cost of doing business. <S> They can recoup that cost any way they'd like (typically they lump it in with "taxes" or itemize it out on the ticket rather than including it in the base fare, so they can advertise lower base fares). <S> What about the little planes? <S> General aviation doesn't pay "ticket taxes", but that doesn't mean they get to escape paying for the infrastructure the flights are using. <S> The government recognizes that the air traffic system costs money, and they like to ensure that the money is available. <S> Accordingly there is a tax levied on all aviation fuel purchased in the US: <S> Airlines currently pay about $0.04/gallon in taxes for the jet fuel they burn Non-Airline flights burning jet fuel pay about $0.22/gallon in taxes(the higher rate making up for the other taxes they're not paying) Piston-powered planes burning aviation gasoline pay $0.19/gallon in taxes (higher than what the airlines pay for jet fuel, but lower than the standard jet fuel tax because piston planes don't travel as far, and are thus less of a burden on the air transport system) <A> Assuming the question was referring to the US airport market, where indeed a big chunk of the airport fees are indeed taxes, here's their composition according to Airlines for America : <A> There are many things which together make up the 'tax' listed on your ticket. <S> And depending on the airline this may or may not be honest; many use the term to bulk up the final price from the list price (and then advertise the list price of course). <S> For example, a "fuel tax" is a sum the airline adds to counter changes in fuel price from the moment the ticket price was set to the moment you board the flight. <S> And the "security tax", were that really a tax, then why do different airlines charge different amounts for the same departure/destination pair? <S> There might be a tax component in it, but it's massively padded by the airline itself (and most of the rest will be not tax, but contract fees with their contractors). <S> Of course some countries do charge taxes, but those are usually collected directly and not as part of the ticket. <A> Airports may be managed by private entities (even private security agencies) and then airports themselves are expensive to maintain, so apart from leasing its space for shops/eateries etc, they charge every passenger a tax which they collect from each airline. <S> But all "taxes" on the ticket are not taxes; as jwenting pointed out, the yq (or yr) component on the ticket is actually a "tax" levied by airlines at their discretion and is called fuel surcharge. <S> Other "tax" components may be an ROE (Rate Of Exchange) component which helps airline absorb fluctuation in currency (if they are operating in the country having different currency from theirs). <A> If it is genuinely a tax , it goes to the government. <S> Other countries may be different but, in the UK, all money that the government receives from taxes goes to a central fund to be spent wherever it's needed: there's no mechanism for, say, the money from aviation-related taxes to be reserved for aviation-related spending, such as ATC. <S> Fees and surcharges are different and may go to the airport, the airline or whoever else charged them. <A> In the US, you can see most airports income, by going to the FAA site: http://cats.airports.faa.gov/Reports/reports.cfm . <S> This lets you see the breakdown by year, and revenue sources and costs. <S> Form 127, contains the most detail in the data available there. <S> Running, modifying, and just maintaining an airport, is very expensive.
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Its the duty of the airline to collect taxes and reimburse it to the concerned authority (whether private or government but probably government).
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What does the zig-zag pattern on Hawker Hunter's leading edge represent? On some Hawker Hunters , there is a zig-zag on the leading edge of the wing, as shown below. Why do only some Hawker Hunters have this feature, and what is it for? <Q> After doing a little more research I found the answer. <S> Quote from wikipedia: A dogtooth is a small, sharp zig-zag break in the leading edge of a wing. <S> The effect is the same as a wing fence. <S> Where the dogtooth is added as an afterthought, as for example with the Hawker Hunter and some variants of the Quest Kodiak, the dogtooth is created by adding an extension to the outer section only of the leading edge. <A> As already answered, the zigzag is a dogtooth extension or leading-edge extension on the outboard portion of the wing. <S> It forces the airflow over the wing into a vortex, preventing spanwise flow outward along the wing at high angles of attack. <S> A lot of modern designs incorporate them, including the horizontal tail of the F-15 Eagle, because they often have a side benefit of increasing airflow over the ailerons and increasing control. <S> To answer the second part of your question ( why do only some Hawker Hunters have this feature? <S> ): <S> the dogtooth extension wasn't incorporated into the design until the F.6 variant. <S> Wikipedia's list of Hawker Hunter variants mentions it in a couple of entries. <S> Basically, the earlier models didn't have it; at some point the designers and aerodynamicists working on the Hunter tested it out. <S> Once they figured out that it was an improvement, they would have made the necessary changes to the production line to make it standard on all late-model aircraft built. <A> Cirrus incorporates this design into their wings as well. <S> Quoting from their site : <S> The outboard section of the Cirrus wing flies with a lower angle of attack than the inboard section. <S> When the inboard section, which produces much of the lift, stalls the outboard section, where the ailerons are, is still flying. <S> The result is that a stalled Cirrus airplane can be controlled intuitively using aileron. <A> Update : The hawker hurricanes wings are better describes as dogtooth extension as flyingfisch points out. <S> These features are known as a Leading edge cuff and aims to reduce spin tendencies by delaying the onset of stall. <A> As an added piece of information, this feature may have something to do with the fact that the Hawker Hunter, for many years, was the only swept wing fighter that could be reliably recovered from an inverted spin. <S> For this reason the Empire Test Pilot School at Boscombe Down used one for advanced training purposes (and may still do so).
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It is usually used on a swept wing, but also on straight wings ("Drooped Leading Edge" arrangement), to generate a vortex flow field to prevent separated flow from progressing outboard at high angle of attack. The zig-zag on the leading edge is a type of leading edge extension called a dogtooth extension .
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What happens if a parachute does not open while skydiving? While skydiving we have to jump from the airplane at a certain altitude above Earth. So if for some reason the parachute doesn't open, then will that person (or any object similar to a human body) fall to Earth or will it be incinerated/vanish in the sky due to air-friction in space before coming down to the Earth? <Q> The majority of the heat developed during reentry of a space-vehicle comes from air compression not friction. <S> Remember, to go into space, you don't have to go very high, but to orbit you will have to go very very fast , and it's not the fall that produces the heat, it's the slowing down part. <S> If you had a human fall without a chute, <S> the terminal velocity (where air resistance cancels gravity and you continue downward at a constant speed) would be around 100-200 mph, not nearly enough to cause any kind of heat (or cars would burn up by going normal cruising speeds). <S> To get higher terminal velocities, you'd have to go a lot higher, where the air is a lot less dense, higher than any skydiver have, and as far as I can tell Felix Baumgartner did not experience any incineration during his jump. <S> The unfortunate skydiver will almost certainly die, but there'd definitely be a body, and it'll probably be in one piece. <A> Qualification: I worked at a sport parachute center as an instructor for 10 years <S> and I hold an FAA Master Parachute Rigger certificate. <S> I believe that qualifies me as an expert on the subject. <S> The fastest a human can fall unassisted is about 300km/h (head-down dive). <S> Far too slow for frictional or compressive heating. <S> Fighter pilots have ejected at supersonic speeds and not warmed up any (it's also rather cold at higher altitudes). <S> You would have to jump from the space station to incinerate yourself. <S> To answer the primary question, if parachute #1 doesn't open, you use parachute #2. <S> If that doesn't work, you have about 10 seconds left. <S> In consolation, it's not all that messy unless you are unfortunate enough to impact on pavement. <S> An open-coffin service is usually possible. <S> To reply to other inaccuracies: <S> the #2 parachute is not spring loaded, the small (1 meter) extraction parachute is. <S> we don't depend on the idiot box auto-activator. <S> There's a handle. <S> skydiving in pairs is not "recommended" (that's scuba diving). <S> You want to be very far away from other people when deploying parachute #1, and by then it's far too late for anyone else to help. <S> The close-up videos you have seen are carefully planned in advance - the cameraman and subject agree on relative position and sequence, and the video subject deploys his parachute higher than usual. <S> Videos you may have seen of several canopies together are also carefully planned in advance, and it's a lot harder than it looks. <S> holding someone else during deployment is not possible. <S> No one is strong enough to hang on during deceleration. <S> It's not (normally) a shock but the forces involved are rather substantial. <S> Backup parachutes DO open very quickly - at freefall speeds it's rather unpleasant. <S> the exceptionally rare cases of someone surviving without a parachute typically involve a steep slope and either deep snow or crushable foliage. <S> Forget water - at 200km/h it's only slightly more forgiving than concrete. <A> There is a spring-loaded backup chute that will auto-deploy when the jumper goes too fast and is below 2.5k feet. <S> If that also fails, the jumper becomes a smear on the ground. <S> Freefall speed (aka terminal velocity) is not fast enough to start any type of burn. <A> If they are unlucky enough to have a failure to deploy the parachute: They will probably hit the ground at approx 190 Km/h (120 Mph) in one piece.
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The unfortunate victim will most probably die instantly.
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Why is a large flashing "X" placed on a closed runway at Reagan National Airport? Runway 15 at DCA (Reagan National) is closed at night and other times. By "closed," I mean that airport management places a gigantic lit/flashing "X" in the landing zone of 15. I'd estimate the big "X" is 8 by 8 feet, at least. It's like one of those roadside trailer flashing signs, except it's a runway. The flashing X is very evident to pedestrians, bikers, etc., on the Mount Vernon trail. It's not some bizarre national secret. My question: Why, in the tightly controlled airspace of Washington, DC, would DCA need to roll out a giant lit "X" to keep planes from landing there? As if the obstruction were not there, you could fly in? That doesn't calculate, given how tight the airspace is controlled. Why does this airport in the center of the world's highest airspace security roll out a construction trailer with a big X to keep planes from landing there? <Q> The standard way of marking a runway as "CLOSED" is to put a big giant <S> X on it - for fields which operate at night that X needs to be lighted. <S> The specifications for the runway closure marker are outlined in an FAA advisory circular (AC 150/5345-55A) <S> The purpose of the marker is to indicate that the runway is temporarily closed (either administratively, as is the case at DCA, or for construction/repair/maintenance). <S> (Obviously in the case of DCA they would have other problems <S> were they to wander blindly into the area without talking to anyone, but believe it or not it happens far more often than any of us would like.) <S> The big flashing <S> X doesn't "stop" you from landing on the runway - it just tells you you really, really shouldn't be landing there. <S> There is a United States Senator who has achieved some notoriety in the aviation community after landing on a closed runway . <S> The X is also quite a bit bigger than you think it is to ensure it's visible from the air (the arms are 14 feet long): <S> (I was looking for a good aerial photo of one at night, but unfortunately couldn't locate one. <S> The intent is for the X to be about the same size as runway numbers so there's no good reason for a pilot to not see it.) <A> Any time that a runway is closed, it is marked as such by an X on the runway so that pilots will know, visually from the air. <S> At night it is lighted. <S> This is an additional measure that is used to help protect people and equipment on the ground along with the aircraft if a pilot were to make a mistake and land on the wrong runway. <S> It is even more important than normal at this particular airport because the runway threshold for runway 19 is very close to that of 15 and they are on similar headings. <S> The Jeppesen airport diagram even includes a note which says "Be advised some aircrews mistake runway 15 for runway 19" (although the one below doesn't include this note). <A> This is particularly important at DCA because aircraft landing on runway 19 will either by flying the LDA 19 or River Visual 19 approaches if landing to the south. <S> Take a look at these approaches: <S> You'll notice that you approach the airport lined up with runway 15 until very close in when you follow the river and turn for runway 19. <S> Having flown into this airport a number of times, it is easy to misidentify the runway if you are unfamiliar. <S> Putting a big X on the runway when it is closed increases the situational awareness and helps identify the proper runway. <S> You'll note in both procedures you must be flying visually to make the turn and identify runway 19, neither approach lines you up for that runway. <S> There is no straight-in for runway 19.
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It is redundant with air traffic control measures (such as NOTAMs) indicating that the runway is out of service, in case some pilots didn't check NOTAMs or somehow managed to stumble into the airspace and happen upon the airport while it's closed.
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Why do aircraft on Flight Radar 24 jump around randomly sometimes? I use Flight Radar 24 on my iPad to track friends/families flights when they are traveling (not paranoia, just curious). I've noticed that, quite often, their plane will jump from one location to another, or jump backwards down the flight path, or zoom forward, or any other number of motions that I assume the plane isn't actually making. (My personal favorite being when they miss the runway on touchdown and the plane disappears. If that actually happened as often as Flight Radar 24 made it look like it was happening...) What makes the planes do this on Flight Radar 24? Why can't it just track the planes correctly? <Q> FR24 relies for most of the tracks on ADS-B data. <S> Part of the ADS-B transmissions is the position. <S> There are three causes of the behaviour that you observe: 1). <S> Aircraft landing next to the runway <S> The position source onboard the aircraft is not always GPS. <S> Mainly older aircraft (e.g. Fokker 100) have their Inertial Navigation System (INS) coupled to the ADS-B transmitter. <S> The INS relies not on external radio measurements but only on measured acceleration and rotation to track its position. <S> It is usually correct at take-off, but it develops biases over time and therefore the landing appears quite often next to the runway. <S> I can assure you that this is mostly misleading. <S> 2). <S> Short time track offset <S> In most aircraft the ADS-B position is from GPS. <S> When the GPS loses its position fix, the system falls back to INS. <S> As described above, the INS position is slowing drifting from the truth during the flight, so the ADS-B track will shortly jump aside to the INS position until the GPS comes back. <S> When short (e.g. 1 position update) <S> the offsets appear as spikes. <S> 3). <S> Long distance jumps (180 NM, 360 NM) <S> Due to the limited number of bits available in the ADS-B messages, position is encoded in a complex format called Compact Position Reporting. <S> It requires at least two position messages to decode the first position of a track, from that point onward, every message will constitute a position update. <S> Also note: When INS is used a the position source, the ADS-B data contains an indication that the data is not to be trusted, but that is silently ignored by FR24. <A> Not to take away from already great answer provided. <S> In my experience the jumping behavior you are describing in Flightradar24 is due to MLAT triangulation that is used to establish approximate location rather than absolute (using GPS). <S> Older planes transmit a SUBSET of ads-b data, which does not include aircraft location. <S> So FR24 knows that there is an aircraft in the air, but doesn't know its location. <S> This is where multilateration (triangulation really) comes into play. <S> If you have a few (minimum of 4) receivers available AROUND the aircraft that are tuned precisely to the same clock, you can measure how long that same ads-b signal reaches all 4 receivers from which approximate location can be determined. <S> In FR24 you can verify which of the "jumpy" planes are being tracked by MLAT setup by looking at "radar" that is tracking it. <S> If MLAT is used you will see "T-MLAT" as the source. <S> If you indeed see jumpy behavior on the planes that are tracked by "T-###" or "F-###" sources <S> then I would agree with already posted answer by DeltaLima <A> Re: INS - <S> Since there are no ground based radio transmission navigation stations in the ocean (VOR's or ADF's), the INS (inertial navigation system) was designed to help jets navigate safely over the ocean (before GPS). <S> INS uses a series of gyroscopes and accelerometers to measure how far a plane has traveled from a specific point. <S> With multiple accelerometers it's able to figure if the plane turned to a specific heading and how far it's gone (it can do this through multiple turns and speed changes). <S> To set the airplanes INS, a pilot pulls up to a specific INS set point at an airport and calibrates it (before the trip). <S> INS is so accurate that it typically holds a planes position to within a few miles after traveling 2500 miles. <S> The INS system can also be set from a GPS. <S> The major advantage to INS is it doesn't rely on any external signal to work.
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When no proper verification algorithms are used in the software, it may occur that a receiver station initializes the track wrongly, usually causing a jump of 180 or 360 NM.
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What data does ACARS send back to base? Can it be used to track a plane? An aircraft's Aircraft Communications Addressing and Reporting System uses line of sight HF via ground stations or satellites to communicate with its base station. This system allows for three types of messages to be sent: Air Traffic Control Aeronautical Operational Control Airline Administrative Control Aeronautical operational control and airline administrative control messages are used to communicate between the aircraft and its base. Various types of messages are possible, for example, relating to fuel consumption, engine performance data, aircraft position, in addition to free text. So, questions: Can ACARS be turned off? Would this generate a warning at the base station? Can ACARS send postion, altitude and heading information automatically? Can ACARS be repeatedly pinged to track an aircraft's position and heading? Would this require any intervention by the pilots? ( posted separately ) Is this system standard on commercial airliners? What data do Airlines collect from the ACARS, if any at all? <Q> Can ACARS be turned off? <S> Would this generate a warning at the base station? <S> See another answer of mine for more details. <S> Typically other systems use ACARS to send reports on a regular basis to update position and track other information, plus on an "as-needed" basis for abnormal things. <S> It would be up to the individual airline to look for these reports and to generate a warning if one didn't check in at the expected time, but I don't believe that they do this. <S> There is a lot of variation in the communication systems and they aren't 100% reliable so a lot of false alarms would be triggered. <S> Can ACARS send postion, altitude and heading information automatically? <S> ACARS itself can not, but other systems like the Flight Management Systems (FMS) or ADS-C on board the aircraft can use ACARS to send reports like this automatically, and in some cases they do. <S> Can ACARS be pinged to track an aircraft's position and heading? <S> Would this require any intervention by the pilots? <S> Again, ACARS is simply a communication system. <S> A message can be sent via ACARS which will forward to the appropriate system requesting this information and have it respond. <S> Is this system standard on commercial airliners? <S> I believe that most airliners that travel over international waters have ACARS, but I'm not sure if it's a requirement or not. <S> What data do Airlines collect from the ACARS, if any at all? <S> This varies from airline to airline, but messages at the beginning and end of the flight (used to track flight time, etc.) <S> and periodically during the flight are typical. <S> Usually periodic position updates and abnormal system indications are included as well. <A> Can ACARS be turned off? <S> Would this generate a warning at the base station? <S> Everything can be turned off, especially in an aircraft. <S> It will probably not generate a warning at the base station immediately, because long distance data comms are not always reliable. <S> It would cause too many false warnings. <S> Can ACARS send position, altitude and heading information automatically? <S> Yes, ADS-C (Automatic Dependent Surveillance - Contract) provides such functionality over ACARS for ATC purposes. <S> ATC have to establish the link first to get the reports automatically. <S> Can ACARS be pinged to track an aircraft's position and heading? <S> Would this require any intervention by the pilots? <S> Using ADS-C position can be extracted by ATC, and the airline can do the same. <S> Intervention by the pilots is not needed <S> Was this system installed and functional on MAS370? <S> Installed <S> yes, <S> functional I don't know. <S> What data does Malaysian Airlines collect from the ACARS, if any at all? <S> I have no idea. <A> ACARS does not include coordinates. <S> It does include airspeed and altitude, as these are of interest for engine health. <S> ACARS was functional on the Malaysian air flight, it was stated that before it went of radar, several messages were received. <S> A good starting point on ACARS can be found on SKYbrary .
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Yes, ACARS can be turned off.
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Can the pitch be very different from the angle of attack? How much the pitch (horizontal orientation) can differ from the angle of attack? I am trying to understand the claim that "angle of attack indicator was unfortunately not available", contributing to problems during Air France Flight 447 . Attitude indicator most likely was available? <Q> The angle of attack is the angle between the wing (wing chord to be precise) and the direction of travel (undisturbed airflow). <S> The angle of pitch is the angle between the main body axis and the horizon. <S> The difference can theoretically be any angle, but during normal flight it will be limited to about 15 degrees. <S> The reason that the angle of attack sensor was inoperative was due to low airspeed. <S> Below 60 knot IAS the indication is unreliable and therefore the indicator is inhibited. <S> This also inhibits the stall warning. <S> This lead to the confusing situation that lowering the nose to correct the stall increased the airspeed beyond 60 knots, thereby reactivating the stall warning. <A> It can be. <S> Remember that the angle of attack is the angle between the chord line of the airfoil and the relative wind. <S> Imagine if the plane is level with the horizon with zero airpseed. <S> It will fall straight down, putting the angle of attack close to 90 degrees with the pitch close to zero. <S> That said, during normal flight it's not likely that pitch and angle of attack will be excessively different. <S> But honestly the two aren't closely related: You can exceed the critical angle of attack and stall at any pitch, bank, or yaw angle. <A> Just want to add the image. <S> Angle of attack is relative to the direction of relative wind (which is equivalently relative to the direction the plane is going, if in still air and the angle of incidence = 0, i.e. the wing is mounted parallel to the longitudinal axis of the plane), while pitch is relative to the horizontal axis. <S> Angle of attack depends on the pitch, current velocity of the aircraft and the wind. <S> They can be different. <S> Image source Assumptions for the image: <S> still air and angle of incidence is 0. <A> Just before the ground impact Just watch this video of a looping gone bad during a flight display. <S> At 1:30 into the video it becomes painfully obvious by how much both can diverge in extreme situations (shown above). <S> The flight path angle is the difference between pitch attitude and angle of attack. <S> If pitch attitude and angle of attack would be equal, the airplane could only fly straight ahead at the same altitude. <S> Once it climbs, it has to increase pitch attitude at constant angle of attack. <S> With enough thrust or speed, both can be 90° apart. <S> Now consider flying inverted <S> : Both are almost 180° apart. <S> In a dive, again the difference will become large because the flight path angle takes on negative values. <S> The more fun it makes to fly an aircraft, the more both angles diverge. <S> Only boring aircraft will keep both of them at similar, low values. <A> How much the pitch (horizontal orientation) can differ from the angle of attack? <S> 270 degrees appears to be the maximum angle that the pitch attitude can differ from the angle-of-attack. <S> Some examples of extreme differences between pitch attitude and angle-of-attack: <S> Jet fighter or aerobatic airplane or aerobatic glider in a prolonged vertical climb. <S> (May be a steady-state situation or the aircraft may even be gaining airspeed or it may just be a "zoom" climb where airspeed is exchanged for altitude; obviously only the latter is possible with the glider.) <S> For simplicity assume a symmetrical airfoil. <S> Pitch attitude is 90 degrees, angle-of-attack is zero degrees, for a difference of 90 degrees. <S> Now the throttle (if present) is pulled back to drop the engine power to zero, but the nose is kept pointing straight up until the aircraft starts to tailslide backwards. <S> Pitch attitude is still 90 degrees, but angle-of-attack is now 180 degrees, for a difference of 90 degrees. <S> Now imagine the tailsliding aircraft experiences a slight variation in angle-of-attack-- perhaps due to a horizontal wind gust striking the aircraft-- that changes the direction of the relative airflow by one degree, so that the relative airflow is aimed slightly toward the top surface of the wing, rather than aimed directly at the trailing edge. <S> Now the angle-of-attack has changed from 180 degrees (which also could be called minus 180 degrees) to minus 179 degrees. <S> Now the difference between angle-of-attack and pitch attitude is 269 degrees. <S> Flat spin with flight path approximating a vertical descent. <S> Angle-of-attack may be close to 90 degrees, but pitch attitude may be close to zero degrees. <S> Actually on the retreating wing it would seem the angle-of-attack may go beyond 90 degrees (wing actually moving backwards relative to the airmass, so the local airflow comes partly from behind), in which case the difference between angle-of-attack of that wing, and pitch attitude of the aircraft, would also go beyond 90 degrees.
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Angle of attack is important to the aerodynamics (amount of lift, drag, etc.), while pitch tells you the aircraft's orientation relative to the ground.
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Where is the airspace not covered by primary Radar? Most ATC in the world rely primarily on secondary radar to know where planes are. This requires that the transponder on the plane works correctly. This means that maintenance and deployment of primary radar is no longer a primary concern for airspace regulation. It becomes at best a secondary backup system before they need to pull out the flight progress strips and airways charts . Where are the spots that is not covered by primary radar? I understand that some military ships have primary radar and can act as a mobile radar during operations. <Q> There are a few spots not covered by primary radar. <S> Here are a few I can think off: <S> Afghanistan, not really what you'd expect from flying between Europe and South East Asia. <S> I was told though by the pilots that the Americans were keeping an eye on us. <S> I'd imagine there are a few holes in the CIS countries as well. <S> Multiple areas in Africa, but this is improving <S> I believe. <S> There's a post on PPrune . <S> Apparently known as the 'dark continent' for spotty coverage and consistency. <S> South Africa has good coverage, and I'd guess the same for much of northern Africa as well. <S> A few remote areas in South America, then again, improving. <S> Oceans are not covered. <S> Determining factors are population density, aircraft density and economic development. <S> As more you Malaysia map, if there's a radar at Kota Bharu [KBR] airport, here's the map assuming a range of 200 Nm for the radar. <S> It should in theory be well within reach. <S> map <S> http://www.gcmap.com/map?P=&R=200nm%40KBR&MS=wls&MR=60&MX=540x540 <S> And an extended version: <S> SGN Ho Chi Minh City (Saigon) <S> [Tan Son Nhat Intl], VN KUA Kuantan [Sultan Abmad Shah Airport (Pedang Geroda Airport)], Pahang, MY KUL Kuala Lumpur (Sepang) <S> [Intl], Selangor, MY KBR Kota Bharu [Sultan Ismail Petra], Kelantan, MY map http://www.gcmap.com/map?P=&R=200nm%40SGN%0a200nm%40KUA%0d%0a200nm%40KUL%0d%0a200nm%40KBR&MS=bm&MR=120&MX=540x540&PM= Just for the interested <S> , here's a map showing Japanese military radar , just to get an idea of coverage in a country full of people and planes. <S> Maps from http://www.gcmap.com/ <A> Most airspace above seas and oceans are not covered by ATC primary radars. <S> ATC relies mainly on secondary radar for surveillance, primary radar is used mainly for airspace infringement protection and airport surface surveillance. <S> Over oceans and remote areas procedural control is used, without any surveillance. <S> Most primary radars used for long range surveillance in ATC are operating in the L-Band. <S> L-Band signals do not follow the curvature of the earth very well; at low altitude the range is limited because the aircraft are below the horizon. <S> At higher altitudes the range is up to about 250NM, but only when the radar is operated at very high power, which is costly both in design and electricity bill. <S> In many cases it is not needed to operate at long range. <S> Radar is also shielded by terrain; in mountainous areas it is difficult to cover the valleys. <S> In Europe, and I believe also in the US, high altitudes are well covered by primary radar, at low altitude there are many gaps. <S> A lower band (HF - UHF) radar can be used to look over the horizon (OTH radar). <S> This type of radars is used for Air Defence purposes. <S> The resolution is very poor compared to radars used for ATC <S> but it serves well as an early warning system for incoming enemy aircraft and missiles. <S> This type of radar requires huge antenna arrays, over a kilometre long and they consume enormous amounts of power. <S> The effective range is typically about 3000 km. <S> For example Australia has the Jindalee Operation Radar Network , that can see past Jakarta, Indonesia. <S> JORN coverage <S> In case of the missing Malaysian MH370, and the latest suspicions that the aircraft ended up West of Perth, I wonder whether the flight was tracked by the OTH Air Defence radars of Australia. <A> In relation to missing flight MH370, and the radar coverage of that region, please see the link to the Department of Civil Aviation Malyasia's primary and secondary (SSR) radar services in the region. <S> http://aip.dca.gov.my/aip%20pdf/ENR/ENR%201/ENR%201.6/Enr1_6.pdf <S> The first page lists all the Primary and Secondary (SSR) civil/military radar services and then page 10 <S> graphically represents the 200NM SSR ranges of each station. <S> So to determine how much of the map is covered by primary radar only, you can match the names of the stations on the map with the table on page 1, and use the 200NM area as a guide to determine the primary radar reach of each station. <S> As an example, the BBC website shows how flight MH370 changed course with this graphic: <S> If we look at the radar coverage map again, we can see that this means the flight passed through the primary radar station coverage of Kota Bharu, listed as 1.1.4(g). <S> Hope this helps, <S> and I hope all the people are found safe. <A> There are large gaps in radar coverage in the Gulf of Mexico. <S> The FAA sponsored a study that looked into receiving ADS-B reports from aircraft in the surveillance gap and reformatting them to look like radar reports from a fake radar sensor in the Gulf <S> so they could be ingested by their existing air traffic control software systems.
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A lot of airspace is not covered with primary radar, at least not for ATC purposes.
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How do airlines pay for their planes? Taking easyJet as an example, they have a fleet of over 200 A319's and A320's. At a price tag of around \$90m per plane, that equates to about \$18bn. Given that their turnover for 2012/13 was around \$7bn, and their net profit was only \$660m, how exactly do they own so many planes? Are they financed long-term? Are they leased? How are the deals structured for the big airlines when purchasing new planes? <Q> The overwhelming majority of major airlines do lease at least some of their aircraft. <S> And most airlines who choose to buy do not end up paying that full price tag. <S> In the case of Easyjet, around half their fleet is leased (as of 2013). <S> Leasing allows airlines with weak balance sheets or with poor future prospects to increase capacity without locking capital. <S> In fact, the largest aircraft owners are aircraft leasing companies. <S> For example, GECAS (General Electric Capital Aviation Services), the largest aircraft lessor, currently owns around 1,700 aircraft, being operated by 230 airlines around the world. <S> There are other (not state-owned and generally low cost) airlines, such as Ryanair, who are fond of owing most of their aircraft. <S> What Ryanair does is negotiate very good procurement deals with Boeing (by buying large packs of planes, all being B-737s), use them for around 5 years, and then sell them before their price has gone down too low. <S> This takes a burden on their debt levels, but seems to work for them so far on the long run. <S> This aircraft resell value is an important aspect to consider when comparing leasing vs purchasing, as well as tax incentives derived from amortization. <S> Legacy carriers (many of them state owned), on the other hand, have a tendency to purchase most of their fleet, and keeping them around for the full lifespan of the machine (around 30 years). <S> The actual price a company pays for a given aircraft is not public (understandably) and most figures you would be able to find are related to "list prices". <S> However, in 2005 Ryanair was forced to disclose facts about one of the massive (by the time) purchases of Boeing aircraft. <S> Apparently, they paid less than half of the public list price . <S> More current data on the actual price airlines pay for Boeing planes can be found here , where Javier Irastorza analyses the discounts Boeing is applying to their aircraft based on a balance sheet assessment. <A> Much of course depends on the companies involved, but there's several common schemes in place: <S> Lease <S> At the end you either get a right to purchase the aircraft for a nominal price or it reverts to the lease company, or you extend the lease. <S> Purchase <S> Outright <S> Yes, you can pay cash. <S> Bank Loans <S> Either a bank or the manufacturer underwrites a loan with the aircraft as collateral. <S> Pretty similar to a mortgage on your house Trade in Like buying a new car, you might get a fair price for that old aircraft you had sitting around Subsidies <S> There's still a lot of national prestige involved in some countries with getting foreign airlines to fly your product. <S> Some aircraft manufacturers as a result can deliver well under the list price to foreign airlines because such sales may be heavily subsidised by their governments. <A> While scrolling through the prices of aircrafts which cost’s more than the GDP of many countries, it seems logical to take aircrafts on lease rather than see one’s balance sheets drooping health. <S> Well, this might not be the only reason why many airlines pick leasing options. <S> By taking leased aircraft the airlines are able to maintain a fuel efficient and latest designs fleet, have better survival options at the time of geo – economic crises and traffic fluctuations. <S> So this becomes a very company specific and situation specific decision. <S> Aircraft leasing market is a very capital intensive business with high risks and higher returns. <S> Since last few years this market is expanding –with Asia- Pacific region fuelling this growth. <S> Asia-Pacific region is becoming the hub of emerging economies -China, Hong Kong, Japan to name some. <S> Among these China is moving fast and is growing its fleet at a humongous rate. <S> Boeing projected in its 2014 annual report that China will buy about six thousand aircraft worth 870 billion U.S. dollars by 2033. <S> Multiple financing options, reduced lease and interest rates, bulk orders, growing Low Cost Carriers are all amplifying the growth of Global Aircraft Leasing Market
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Especially older companies may have the cash reserves to pay for new aircraft out of pocket. Effectively like your lease car, you pay a fee per month or year over a contract period.
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Where does my pee go when I flush at 35,000 ft? One thing I guess a lot of people wonder is: what happens you flush the toilet in an aeroplane? Does it fall out the belly of the plane and disintegrate? :) A kiwi woman complains that "aeroplanes are taking a s**t on her driveway", beneath the flight path. Is there any way this might actually happen? <Q> I can speak for the most common commercial models (the 7x7s, A3xxs and the like) via an engineer friend. <S> All of these models flush into a tank which is emptied on the turnaround. <S> For Vulcans, I can speak with first hand experience. <S> Each crew member had a stainless steel "pee tube", a funnel, which fed into a rubber bladder. <S> They are emptied and cleaned during the after flight inspection. <S> I was changing a radio under the rear crew table where the electronics, navigator and radar operator sat. <S> This involved squeezing down behind the seats to lie under the table, disconnecting and unfastening the radio, hauling onto your chest then pushing it up onto one of the seats and reversing the process to get out from under the table. <S> As I pushed the radio up onto the seat, I knocked one of the pee tubes and bladders out of it's clip holder which then emptied the contents onto me and the radio. <S> The bladder had not been emptied - and the aircraft had been in the hangar for 3 weeks! <S> Of course, it was my job to clean up the mess - lots of french chalk as urine is very corrosive to airframes. <S> The radio also needed writing up <S> so I tagged it as "suspect urine ingress". <S> The same radio came back to me with a tag attached saying (and this might work only for non-American English speakers) - "are you taking the p*ss?". <S> Yeuch. <A> On newer airliners it is fed into a septic tank. <S> Decades ago, it was simply dropped overboard. <S> Before the introduction of vacuum flush toilets , water flushing was used which involved big tanks which could leak their content overboard. <S> The Boeing 727 had at least two cases where the right engine was lost as the ultimate consequence of this malfunction . <S> Since the lavatory piping was on the right side, ice which had built up there could break loose and be ingested by the engine behind. <S> If the ice block was large enough, it could damage the fan, and the resulting imbalance could shake the engine off. <S> Boeing engineers designed the engine mount with a rated break point so hefty engine vibrations would not damage the rest of the plane. <S> Glider pilots have all kinds of means to lighten themselves when nature calls. <S> The product of this is then thrown overboard - <S> that is what the small sliding window on the left side of a glider canopy is for. <S> A friend of mine uses plastic bags and once forgot to take one with him in a competition flight. <S> He realized his omission just before he was aero-towed on his way and asked bystanders for help. <S> Someone handed him his plastic bag which had been used to hold apples - and was perforated. <S> My friend realized this detail too late, but very soon after he began using the bag. <A> From Yahoo! <S> Answers and Wikipedia: Aircraft lavatory .
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It is stored and then disposed of when plane touches down.
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How can Ryanair offer flights for a penny? Of course, we all know that you're not exactly treated like a rockstar on Ryanair, and their CEO wants to charge us £1 to use the toilet ; but still, how can they offer flights for a penny?! Looking at flights with budget airlines, they usually end up costing more, with taxes etc added on, but I've seen Ryanair offering flights for literally a penny, all in. <Q> Besides @Sebass van Boxel's answer, I'd like to add the following: <S> I was talking to a Fastjet pilot (ex easyJet) <S> and he was telling me that obviously not all seats are available for a cheap price. <S> If you book early you will get a special price but try booking a day before and you will see. <S> As has been said, a lot of money is made on all the extra services such as luggage, food, etc. <S> From what he told me, the profit on each flight for easyJet is minimum \$400 per flight at 96% full — which is not much, but consider that easyJet has something like 1,000 flights a day and that means \$400,000/day profit. <S> Not bad... <S> That how the money is made. <A> Basically taxpayers are paying a part of your ticket ( See this businessweek article ). <S> Next to that they fly on relatively cheap times and small airports which means they have to pay less to an airport. <S> Lastly; as you know that charge fees for everything. <S> Whether you want to bring an extra bag, something to drink or like to go to the toilet in the feature, you'll have to pay for it. <S> I wonder whether they can make money when people don't want to make use of the 'extra's' they offer. <S> I don't think so. <S> Maybe someone can do the math and calculate what an average Ryanair flight costs ( See this answer ) and how much money they get from only the tickets. <A> The marketing term is "loss leader" - you lose money on the advertised product but make more money on other things. <S> In this case fees and other things the customer might buy ( checked bags, water ) after we get them in the door (website). <S> Your grocery store does this weekly. <S> For example: 2 litre Coca-cola $0.49 deals. <A> The real answer has not been given yet, it boils down to marketing. <S> Offering flights for a penny sounds to good to be true for most people. <S> It makes them curious and draws them to the Ryanair website. <S> That is exactly what Ryanair wants, it is free publicity. <S> Then for given flights there are a set of seats available for that price. <S> It will be on the days that most people can't fly for a leasurly reason thus during weekdays or on flights that draw not that many customers. <S> But since people have been drawn to the website they stick around and try to find a cheap deal. <S> Ryanair knows this and the whole website is set to encourage you to buy a flight, they state how many seats are available for the discounted price, encouraging you to keep searching for a cheap deal. <S> In the end most people will settle for a reasonable cheap flight to a destination which was not there first choice but the flight was cheap so they bought it. <S> ;) <S> As of now they state that they have 500.000 seats available for discounted price of 25% off <S> , they have roughly 2000 departures a day, with 189 seats per plane this works out to 378.000 seats departing on a single day. <S> the campaign runs for a month so that results in 11.3 million seats. <S> In the end they have put 4.4% of there seats for that month on discount. <S> Not that many, that is roughly 8 seats per aircraft or little over 1 row of seats. <S> In the end it is just a very cheap marketing strategy! <S> Then the part of the question, How can they offer them so cheap? <S> Willingness to pay is the key, last minute seats are expensive, since you obviously need to go somewhere in a hurry, this means that you are willing to spend more on a ticket. <S> These customers pay for the cheaper tickets bought way in advance buy others. <S> Routes with a high demand also allow the airline to ask more for a seat. <A> "how can they offer flights for a penny?!" <S> Do some research on the topic of Yield Management <S> (hint: only a small proportion of people on any given flight will pay "a penny"). <S> All airlines work on yield management for their pricing. <S> Just the LCCs (Low Cost Carriers) have taken it to a whole other level. <S> Its a fascinating topic. <S> But incredibly complex, especially in the "cutting-edge" form adopted and embraced by the LCCs. <S> P.S. Revenue Management is another big topic to look into in relation to airline commercials, again its an area all airlines do but again turned into an artform by the LCCs. <S> Another one to investigate once you're done reading up on Yield Management ! <A> As mentioned above, there are many (hidden) fees. <S> Plus, Ryanair uses small airports with small amount of movements a day, which gives the advantage to Ryanair when creating contracts with these airports. <S> Basically, airport has 15 minutes to refuel, check, clean and service aircraft after landing, and the aircraft has to be ready to leave within this 15 minutes period. <S> If the airport doesn't meet these requirements, the airport has to pay a huge fee (can't remember how much exactly, but at least close to two thousands Euro, maybe more).
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One of the reasons Ryanair has some benefits on other airlines are the subsidies they get from airports.
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Could an aircraft 'hide' in the aircraft shadow of another aircraft without being detected or noticed? I just finished reading an interesting post where the author suggests that the missing Malaysian Airlines flight 370 could have 'hidden' under the cover of Singapore Airlines flight 68 to fly to a covert airstrip. I've read multiple thrillers where submarines have hidden behind the acoustic signal of large cargo vessels to mask their sound over sonar arrays, and this (at least in the book) sounds plausible. I also read another book where a bomber (flying under the identity of a commercial jet) masked a business jet to get it into an area without detection. Naturally, both examples are taken from fiction, but I'm wondering: Would there be any hints now in retrospective to suggest they were being followed? Their transponder was off of course, but I'm wondering if for instance there might be some radio interference or static from such as large aircraft behind them? Are there every any issues when refueling aircraft do this sort of thing? What is the resolution of radar? Would one be able to notice the two blips on the screen unless they were literally under or beside each other, or would it still appear as one dot on secondary radar if say they were 200 meters behind and below? <Q> Radar resolution is defined in terms of degrees of arc (or alternatively in steradians/solid angles) and as such, the further away from the radar, the larger volume is being sampled. <S> At altitude and some distance from the radar you should have a bit of leeway on how loose of a formation you can fly and show up as one contact on the radar display. <S> I'm not giving credence to the theory presented, but I am saying it is plausible that one aircraft could fly a formation with another and be detected as one airplane by a radar. <S> If the transponder is off, the aircraft you are following will not see you on TCAS <S> and if you are behind them you will be visually undetectable by the crew or passengers. <S> If you fly above them you will be clear of their wake, so I would put behind and above the best position to shadow. <S> A lateral offset might be safer, but if you stray too much, you might wander into the FOV of the cabin. <S> I can't see any way the following airplane would cause nav or com interference in the followed airplane. <S> The biggest threat to being detected in this scenario are being seen by other airplane. <S> If ATC calls traffic and you see two planes in formation instead, you would probably say something. <S> In the case of the airplane you refer to however, it was night and <S> if you turn all of your position lights, beacons, strobes, tail lights and if there is no moon out you might escape visual detection by a third party. <A> Fighter aircraft routinely fly close to give a false indication of numbers (I used to do it), but close formation is rarely necessary. <S> The basic resolution angle formula for a radar is 1.22*wavelength/diameter = angular resolution in radians (circular antenna).For long range Air Traffic Control, typical wavelength is 0.15m, diameter of aerial is 14m. <S> So at 60nm this gives a distance resolution of about 3/4 of a mile. <S> Real antenna have various physical and electronic devices to improve this, so in practice staying at less than 1/10 of this, say 150m, usually means no detection. <S> 150m is the standard FAA specification for its long range radars. <S> We used to use about 75m since we liked to stay "numbers disguised' till about 30nm range. <S> The real problem for the pilot of MH370 would be that he has very little overtake available to effect the intercept, or a suitable Air Interception radar, which makes it highly unlikely he could have achieved it, as he had no fighter background. <S> There used to be a prohibition on HF radio ops during aerial refueling <S> but I believe this was for static electric reasons rather than transmission interference. <S> Flying in close formation (5m or less separation) can cause buffeting effects, but basically a plane <S> 75m away is not going to give any indication it's there. <S> Formation flying is not easy, especially in an airliner! <A> Theoretically possible once you get close enough. <S> In fact military aircraft do it all the time, making a group of smaller aircraft look like a single larger one. <S> But there's a catch, getting close enough in the first place, and without being noticed. <S> The crew and passengers of the other airliner would notice a T7 flying in close formation, and even if they didn't see it, they would notice the buffeting and certainly the proximity alarm on the other airliner would notify the crew, who'd notify ATC, who'd send in fighter aircraft to see what the heck was going on. <S> And don't forget that it takes rather serious training to get aircraft to fly that close, and close coordination between the aircraft to retain that formation and not crash into one another. <S> All of which would not be in place in your scenario. <S> So no, it's just another conspiracy theory dreamed up by people who've seen aircraft with crews trained for it fly in close formation at an airshow and didn't know what is involved, just like the idea that the T7 would have flown at wavetop level to avoid radio contact, or diving and weaving through the mountains just over the ground. <A> I think this is more possible in theory than in fact. <S> One radar station has given blind spots, but most nations use a whole array of stations. <S> So if you were not seen on one sensor you'd probably be seen on another. <S> Plus shadowing behind another jet would likely put you in a zone of dangerous wake turbulence. <S> Aside from sensors noticing you dilligence is required by those who monitor the sensors. <S> Seems like that might have been absent on the Malaysian jet, if it actually diverted course radically and crossed the Malaysian peninsula as is being suggested in the news.
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Over the ocean it's easier not to be noticed since ATC radar stations are built on land.
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Like transponders, can flight recorders be turned off? I never knew much about airplanes before the tragic incident of Malaysia 370. I have been spending a lot of time on Twitter reading various articles and investigations; in one of the articles I read , they stated that unlike transponders, "black boxes" cannot be turned off. However, each ELT is specifically designed for each aircraft, so it cannot be tampered with. You also cannot turn off the black box, as it runs throughout the flight, recording every 30 to 60 seconds. Is it really impossible to turn off the black boxes from within the plane? <Q> There is no switch for the FDR, but there is a circuit breaker and by pulling this you are removing aircraft power from the FDR. <S> However, this does not mean you are necessarily turning it off, as some FDR can be equipped with an internal power supply as a backup to aircraft power. <S> The quote in the question (bolded emphasis mine): <S> You also cannot turn off the black box , as it runs throughout the flight, recording every 30 to 60 seconds. <S> is a case of an "expert" or journalist confusing the lack of an on/off switch as an inability to turn something off. <S> As you'll find many examples of in the media, they don't always get it right. <S> The circuit breaker may not be a true on/off switch, but pulling it does accomplish de-powering (assuming no internal power supply) and thus turning off the FDR. <A> However, i'm pretty sure that you can pull the corresponding fuse behind the cockpit. <S> It's a safety thing after all, since you don't want a short circuit from the FDR causing problems to the rest of the plane. <S> While I'm not sure of how this works on the Boeing 777 as in MAS370, it was attempted on FedEx flight 705 . <A> Neither the FDR CB nor the CVR CB are accessible from the B772 flight deck. <S> The FDR is powered on at engine start. <S> In the event of a mishap the CVR CB is pulled as a means of saving the data. <S> The CVR CB is accessed from the E&E bay. <A> On most commercial aircraft there is a circuit breaker for the cockpit voice recorder. <S> The recorder can record communication in the cockpit for 30 minutes or up to two hours on later model aircraft. <S> They are continuous loops which will record over the oldest previous recordings. <S> Whenever any incident occurs during the operation of a flight, the circuit breaker is pulled to keep the pertinent cockpit conversation on record and not be recorded over. <S> I am unaware of any such circuit for the flight data recorder.
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Generally, I'm pretty sure there's no switch for a Flight Data Recorder on the overhead panel in most aircraft, since I think it switches on automatically.
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How does aileron reversal work? I want to know how aileron reversal takes place when control reversal velocity is higher than divergence speed and operating speed is in between them (for conventional wing) <Q> As I understand it, aileron reversal can occur in two regimes of flight, high speed and near stall. <S> Near stall, the wing is very near <S> it's critical angle of attack. <S> When the pilot inputs let's say a left turn, the right aileron will deflect downward. <S> This downward deflection increases the AOA of the outboard portion of the right wing such that the lift generated by that outboard portion is lower (drag higher as well) than the lift generated on the opposite wing. <S> You can kind-of visualize this by thinking of a wing operating on the backside of the lift curve. <S> Aileron reversal at high speed, (again, as I understand it) can occur when the wing isn't stiff enough tortionally to prevent twisting about the aircraft's lateral axis when a control input is made. <S> Some old warplanes had this characteristic at high speeds. <S> For example, the pilot makes a control input to the left. <S> The right aileron deflects downward, and instead of raising the overall AOA of the wing, it lowers it because the aileron acts like a trim tab, twisting the wing's leading edge downward. <S> Your question is asking: If the control reversal velocity is calculated to be higher than the divergence velocity, (When the wing breaks apart), how then can control reversal take place in flight? <S> The answer would be when it occurs near a stall. <A> Control reversal speed is way lower than divergence speed . <S> It may actually be lower than operating speed for some aircraft, which is why they have inboard ailerons/flaperons and/or use spoilers (that don't suffer control reversal) for roll control at high speeds. <S> For that the wing has to flex, but it does not have to flutter at all. <S> Spoilers act closer to the wing mid-chord, so they don't twist it much and thus don't suffer reversal. <S> In fact they twist the wing a bit, because pre-stall lift acts more forward than post-stall lift, but this twists the wing forward and thus further reduces the lift, so still no control reversal. <A> At high speeds a large downward aileron deflection can cause the laminar flow to separate from the top of the wing and become turbulent. <S> At this point the wing essentially ceases to produce lift, whereas the other wing has an upward aileron deflection and continues to produce lift. <S> This rolls the aircraft in the opposite direction than intended. <S> I have experienced this in a C152 aerobat while recovering from a steep dive, there is some buffeting and a slow roll opposite to the control input. <S> I have also heard that at trans-sonic speeds control inputs can precipitate shock waves on parts of the airframe that can cause control reversal without laminar flow separation. <S> But I have not experienced this in a C152 (yet). <A> There is another effect that would have been the cause of the tail of the space shuttle to have a reverse effect above about mach 1.5, where the front of the tail is blunt, designed to deflect hot air during re entry. <S> See diagram.
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Control reversal (at high speed; there is also control reversal at stall, which is different) occurs because the force generated by ailerons twists the wing sufficiently so that the aileron starts to act more like a trim tab.
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Can a commercial airliner sink to the bottom of the ocean? Is it possible that a commercial airliner could hit the ocean surface at such an angle that it made a deep dive intact, got filled with water, sank, and got stuck in mud at the floor of the ocean? <Q> Can a large modern jet airliner plunge intact underwater from flight? <S> No. <S> Large airliners are not desgned for this and are not even strong enough to make a landing on water in less than perfect conditions. <S> E.g. <S> 961 <S> striking the surface at a larger angle would certainly lead to widespread disintegration. <S> Is it possible for a large modern jet airliner to sink intact? <S> Yes (as near as makes no difference) <S> Almost all large aircraft impacting the sea surface in an emergency or uncontrolled will break up immediately and catastrophically. <S> One notable exception was US1549 , an A320, which was landed on water without breaking up. <S> It was described as "still virtually intact though partially submerged and slowly sinking". <S> The left engine detached and sank. <S> So a controlled landing on water is possible under extremely favourable circumstances. <S> It would then be possible for the aircraft to sink in more-or-less one piece without creating a large amount of floating debris. <A> Hitting water at speed is a lot like hitting concrete (try experimenting with different positions hitting the water off a high diving board—some will hurt). <S> Aircraft are simply not designed to withstand the sudden forces introduced upon impact with water, no matter the angle. <S> If an aircraft were to hit the water at high speed, the relatively flimsy structures of the aircraft would shatter, disintegrate, and completely lose structural integrity. <A> As always. <S> Generally, yes, it is possible to land an aircraft on water intact. <S> But the aircraft has to help you with that. <S> Many are even tested for ditching qualities during development. <S> I personally know of the ditching tests of the Breguet Atlantique and the Antonov-70, and there are certainly more (see https://www.youtube.com/watch?v=jK8ydLY5QHQ at 2:15 min into the movie). <S> A Dutch Atlantique once had to go down and landed intact in the North Sea. <S> It was towed into a harbor and lifted out of the water a few days later. <S> The openings (for cooling air etc) have special valves which close automatically when the aircraft is in the water, much like a snorkel on a submarine <S> (sorry, could not find a web source for this). <A> It would be judged upon the state of the aircraft once stopped after the collision, taking into account velocity and angle of impact etc. <S> If the A/C is in-tact and no water is taken on-board it will float for a greater time <S> but I highly doubt it will for a large amount of time because water always finds entry points. <A> If the plane flew to empty, and the pilot made a manual controlled glide and water landing, he would still strike the water at a speed in excess of 150 mph. <S> The engines would still be ripped off, baggage hold doors would most likely open on impact. <S> There would have to be some kind of debris field. <S> The plane would sink, but not intact. <S> Something would come free and float to the surface.
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If the engines are not below the wings (turboprop, piston, jet at the rear fuselage), and the pilot flares to minimum speed right above the water, gear up , then most aircraft will stay intact. My answer is: It depends.
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What are these hooks on the A320's wing used for? I was flying on an A320 (equipped with sharklets) the other day, and I found these hooks on the wing's surface: Note that the single hooked attachment is outside the wing's "DO NOT WALK OUTSIDE THIS AREA" line. What are these hooks used for? Why is the single hooked attachment outside the "safe" walking area line? <Q> From Wikipedia , these are for overwing exits. <S> The use of overwing exits in a ditching varies from airline to airline. <S> On aircraft fitted with overwing exits, there is typically a raised escape rope bracket (about a third of the way from the door) <S> attached to the wing's upper surface and typically painted yellow. <S> This is accompanied by an escape rope found in the frame of the exit after opening the hatch. <S> Once this rope is attached to the escape rope bracket, it will aid passenger evacuation onto the wing to await rescue or to enter the water (depending on the airline's procedures). <S> On aircraft with life rafts to be launched via the overwing exit, the wing will be used to provide a boarding platform onto the life raft. <S> On certain regional aircraft, the overwing exits are the only escape route in the event of a ditching. <A> Likely they are tethering points for emergency exit ropes. <S> The Boeing 737-800 has the same type of hooks. <S> See top row from the water evacuation procedures: ( Image source ) <A> The inner ones are mounting points for evacuation slides and/or a rope handrail since the wing is likely to be slippery and wet. <S> Several aircraft including the A320 and B737 have additional overwing life rafts when ditching. <S> You clip in a rope either at these points or in a hook at the window, throw it overboard, and give it a sharp tug to inflate. <S> Joyous passengers will then board the life raft. <S> Source <S> The outer one works as a harness securing points for the maintenance guys working on the wing, but I guess this could be used for the first purpose as well if you would want to gather everybody around one wing or something.
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In the event of a water evacuation, there is a line associated with each overwing exit that is extended, and clips to that yellow bracket, as a guide to get everyone out on the wing.
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Could Malaysia Airlines Flight 370 have sunk without leaving any floating wreckage? With all the searching on the surface of the Indian Ocean for evidence of Flt. 370, I'm wondering if there's any conceivable scenario in which the Boeing 777 could have sunk without producing any floating wreckage. Is it possible for a 777 or similar model to hit water without leaving a trace of remains on the surface? <Q> Yes, but only under highly unlikely circumstances. <S> An airplane contains all sorts of materials that float, from fuel to seat cushions to the plastic cups in the galley. <S> In order to sink without leaving any floating wreckage, all of that material would need to be trapped within the airplane while it fills with water. <S> In order for this to happen, the airplane needs to land intact on the water. <S> As any number of ditchings indicate, this isn't going to happen -- even US Airways 1549 had the rear of the fuselage tear open on landing. <S> More often, the engines or wings will tear off, leaving oil and fuel slicks. <A> Yes, it's certainly possible. <S> But it all depends on a lot of factors. <S> Speed of impact. <S> Obviously, the lower the speed of impact the fewer pieces will break away. <S> time. <S> Even if things break away and float, after a while they'll sink as they become water logged. <S> And that may only take minutes. <S> environmental conditions. <S> Water temperature affects the speed at which chemical spills dissipate. <S> So do wind and currents. <S> Wind and currents, through wave action, can also break up into tiny fragments and cause to sink any floating debris. <S> So even if something were left on the surface after the impact, after a few hours most of it would be gone. <A> It may possible like the US Airways Flight 1549 ditched in the Hudson River <S> This was in a river with smooth water. <S> I'm not sure if there's ever been a passenger jet successfully land intact on the sea. <S> If the Malaysian flight successfully ditched like Flight 1549, then I'm not sure if the plane could float for hours. <S> It would sink for sure if the doors were opened.
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After days, unless the aircraft crashed near a shore and pieces wash up, most likely there's nothing left to see unless very large pieces broke off and managed to stay afloat (which would require very calm surface conditions indeed).
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Why do flight times differ between traveling East versus traveling West? Why does it take longer to fly West to East than East to West? Which factors affect this? Does Earth's spinning affect the time difference? Maybe the air circulation? <Q> As Robbie's answer implies, the answer is <S> wind - Trade Winds govern what happens on or near the surface and were historically important for sailing ships, and today in aviation we deal with the the Winds <S> Aloft at whatever altitude your plane is flying. <S> As an example, consider two hypothetical flights at 30,000 feet with the winds shown below: <S> With these winds a flight from A to B <S> (East-to-West) will be fighting headwinds the whole way. <S> My handy flight planning program tells me that at 500 knots (airspeed) you'd be in the air for about 5 hours 30 minutes. <S> Traveling in the opposite direction from B to A <S> you'd have a tailwind, and with the same 500 knot airspeed you would make the trip in roughly 4 hours. <S> The winds aloft vary seasonally, which can affect flight times for summer versus winter trips. <S> According to one of our folks who is regularly up at those altitudes <S> even the daily variations can be noticeable, and may make the difference between being able to make a nonstop trip or having to stop for fuel on the way. <S> Pilots and flight dispatchers will often review the wind data prior to flight and try to select an altitude that affords a "good ride" (free of turbulence) and favorable winds (either a tailwind or the lowest headwind they can find). <A> The main reason for the difference in time are trade winds . <S> The true air speed of any aircraft is not affected by the wind. <A> The jet stream moves from West to East. <S> At the altitude an airliner flies the speed of the tail wind or head wind will have a significant impact on actual ground speed. <S> This was first observed when B-29 bombing raids on Japan during WW2. <S> Before that there was no notion of a 'jet stream'. <A> Short answer: As you have indicated in the question description, the answer is winds. <S> Better known as Jet Streams. <S> Long answer: https://alliknowaviation.home.blog/2019/03/29/why-do-planes-travel-faster-west-to-east/ <A> Opposite flying west. <S> Some of this is made up for when flying at the latitudes of west to east jet streams when travelling east, so the actual flight time going east under those conditions will be shorter,even though you arrive at a "later" time. <S> A closer look at your flight time based on your original time zone may give greater insightto your question, and maybe a little less "jet lag".
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Trade winds generally travel East to West, and so aircraft travelling in this direction have a faster ground speed , that is the speed relative to the ground. Although the rotation of the earth and weather created by solar energy do affect the air circulation of the planet, and jet streams aloft, the main reason why west to east flights take "longer" is that flying east into new time zones adds an hour to your landing time for each time zone flown through.
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Why do pilots announce the cruising altitude of a flight? At some early stage in the flight, why will commercial pilots announce the cruising altitude of the flight? <Q> No real reason other than it keeps people from bugging the flight attendants by asking "how high are we??". <S> It also lets the flight attendants know that the aircraft is at cruise so won't be climbing and making the carts harder for them to push around. <A> Passengers like information and even if some do not, it isn't much an inconvenience to hear it anyway. <S> It is written nowhere in my manuals what is to be said in the boarding PA except some general guidelines on how to conduct yourself on the PA system. <S> PA announcements you've heard have the cruising altitude, and the captain showing a new first officer how to do the boarding announcement will include that information. <S> That first officer will go on to include the cruise altitude and when he is a captain he'll pass it along to his first officers. <S> If you took a look at every pilot individually you'll find that the vast majority of each pilots boarding announcements are exactly the same (aside from things that vary like the specific cruise altitude and weather information). <S> After saying the announcement a few times you settle into a routine and it perpetuates. <A> If it is at the beginning of the flight, I would guess they are just sharing in case any passengers are interested.
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It may give flight attendants an idea of how long it will take to reach cruise. That information is a matter of tradition as far as I can tell.
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