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Is the Falling Leaf maneuver used for UAV recovery? The Falling Leaf maneuver is a way to lose altitude by descending like a tree leaf. Is this maneuver used in the recovery of UAVs? Source . <Q> The maneuver as described is not a particularly efficient way of losing altitude: You're alternately stalling & recovering from the stall. <S> More efficient descent procedures exist. <S> The technique of holding the aircraft in a wings-level stall (or putting it into a spin) was used in the early days of aviation to get back below a cloud deck if you were trapped "on top": when you broke out below the clouds you would recover from the maneuver & proceed to your destination / landing (if you were lucky enough to have sufficient altitude to recover when you came out of the bottom of the clouds). <S> Needless to say neither of these maneuvers makes much sense for an unmanned aircraft: If your goal is a rapid descent you will execute a maneuver that gives you the best possible descent rate (such as the emergency descent procedure in the POH, or the one in the Airplane Flying Handbook); If your goal is to get back below the clouds you've already busted the regs (you need to maintain visual line-of-sight with your UAS), but if and when the regulations change you should also be able to recover using more modern techniques (like descending on an instrument approach or using a synthetic vision system) to ensure you don't hit anything, like another aircraft. <A> For me, I can drop from 350ft to 30 ft reasonably quickly, and feel that I have full control using line of site. <S> After reaching about 30ft, I can easily pull out of falling leaf and do a nice slow landing. <A> While not a "Falling Leaf" Maneuver, a "Deep Stall" to landing is actually a very common way to recover a UAS. <S> This is the default behavior for RQ-11 and RQ-20. <S> The systems are designed for this and absorb the energy of the fall in padding and by breaking apart. <S> Each system has a spares kits for wing panels and nylon fastners. <S> An advantage of this method is that it improves accuracy by simplifying energy management; just fly over the intended recovery zone and stall it in. <S> The vehicle will be close to where you wanted to land.
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I use falling leaf with my suas when I want to loose altitude quickly, and don't want to risk entering vortex ring state.
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Why don't airliners use in-air refueling systems? Right now if an airliner wants to fly a really long distance (eg., a Boeing 787 flying from Seattle to Tokyo), it has to load itself down with lots and lots of fuel, which in turn weighs thousands and thousands of pounds. This, of course, makes the flight of the aircraft less efficient than it could be 1 . Thus, if the craft could theoretically carry half as much fuel, that should increase the fuel efficiency of the craft, right? 2 Mid-way refueling seems like it would be a Good Idea ™ at that point. Of course, landing would add a heck of a lot of time to the flight, so it seems the better option would be mid-air refueling. It would allow for the aircraft to be more efficient, without the need for stopping on a long journey. Boeing and Airbus both make a few airplanes | that can do | mid-air refueling , in fact one of them is a highly modified 747-200 (properly called a VC-25 ) used as Air Force One: (source: wordpress.com ) I assume that, because Airbus and Boeing's engineers and sales managers are really quite smart, they have a really good reason that they don't fit/sell this feature on any civilian transportation aircraft. But I'm not sure what that reason is. Does anyone know why airlines do not use aircraft that are capable of mid-air refueling? 1 If I'm not mistaken, increased weight means an increased AoA to maintain level flight, which in turn increases induced drag from the wing. Less fuel would mean less induced drag or, if mid-air refueling were common practice, a wing that was designed to be more efficient because it was required to handle less weight. 2 I don't know by how much, if it's not that much, well, that might explain why nobody does this. <Q> Fuel Quantity <S> Unlike smaller fighter jets, you would need to offload a substantial quantity of fuel. <S> For a B777, you're looking in the range of 60 tonnes of fuel for half a tank. <S> The boom of <S> a KC-135 (faster than a basket) can do around 3 tonnes a minute. <S> The math comes to then 20 minutes of aerial refuelling. <S> The KC-46 can do perhaps 180 tonnes, so you might squeeze out three refuelling operations from one flight. <S> Risk <S> This is considerably more dangerous than the very conservative safety margins aircraft normally operate within. <S> You would have one aircraft filled to the brim with fuel, and another aircraft with 300+ passengers. <S> A quick search on YouTube is enough to propose this entire thing is very dangerous. <S> Furthermore, you need to consider that the aircraft needs safety margin to divert should refuelling not work, which cuts into the benefits you can expect. <S> Many intercontinental routes will be flown at night, making the manoeuvre more difficult. <S> Refuelling Area <S> Looking at the route you proposed, the closest airfield would probably be in Alaska, at least 500km away. <S> Guess another relevant area would be Iceland/Greenland. <S> Even if you did reroute, you'd get away from the jetstreams that aircraft over the Pacific use lying considerably further south, reducing efficiency. <S> The same scenario applies for eastbound Atlantic flights. <S> Expensive <S> You would need to get another aircraft (~$200m for a KC-46) with special equipment and crew training. <S> The receiving aircraft crew would also need special training. <S> Furthermore, you would need to get everybody to agree on some common standard. <S> Logistics Planning is difficult. <S> Each aircraft would have to be rerouted to intercept the tanker at a certain time and place. <S> You want to refuel them perfectly one after an other, which is almost certainly not possible. <S> There's just not the volume of aircraft movements feasible for this, especially for the ultra-long flights where it may have the greatest benefit. <S> Other Landing Benefits <S> Include changing crews and possibly offloading passengers. <S> Applicability <S> The number of flights where this can be practically implemented and used is very limited and for all intents and purposes, you can just land the plane itself and refuel it. <S> Even for the route you propose, it's around 7,500 km which is not a lot for a B777. <A> Don't look at the fuel consumption of the airline flight in isolation. <S> An airline would need to combine the fuel used by both the revenue-earning flight and the tanker, and then add the cost of operating it, too. <S> Even if this could be shared by four or five revenue-earning flights, the total would still be worse. <S> To find out how big the fuel saving by in-air refueling is, the Breguet equation is your friend. <S> Let's assume an L/D of 18, a thrust-specific fuel consumption of $b_f$ = 0.018 <S> kg/kNs and a speed of Mach 0.82, which equates to <S> $v$ = 279 m/s in 11.000 m altitude . <S> Now look at the mass fractions which go with ranges of 8000 km and 2$\cdot$4000 km:$$\frac{m_1}{m_2} = <S> e^{\frac{R\cdot g\cdot <S> b_f}{v\cdot <S> L/D}}$$Flying the distance in one go needs the plane to start with a fuel load equivalent to 32.5% of the landing mass, while an air-refueled flight needs only 2$\cdot$15.1%. <S> The saving (fuel equivalent to 2.3% of airliner's landing mass) is real, but even if four others could benefit from the same tanker flight, it would need to cost less than the equivalent of the fuel price of 5$\cdot$2.3% = <S> 11.5% of the airliner's landing mass. <S> Since the tanker needs to carry 5$\cdot$15.1% = <S> 75.5% of the airliner's landing mass in fuel <S> , it needs to be an airliner-sized aircraft itself. <S> Add more if the tanker needs to do even as much as to take off, let alone fly to a refueling point and wait there. <S> And the fuel saving needs not only to pay for the tanker's fuel needs, but also for its crew, maintenance and depreciation. <S> Aerial refueling is a great technology to make complex military scenarios possible , but is a very ressources-hungry beast. <A> 2019 update: site is dead (now a scam service) . <S> See wayback machine here : <S> The people from Cruiser-Feeder http://www.cruiser-feeder.eu/ try to make it happen. <S> Here is part of the abstract from a paper describing their approach: <S> In this paper it will be described how the safety of air-to-air refuelling has been assessed, and how proposed new or amended regulations and acceptable means of compliance have been defined <S> They even created a conceptual design of joint-wing tanker for civil operations: http://www.cruiser-feeder.eu/downloads/li-la-rocca---conceptual-design-of-a-joint-win.pdf <S> In their papers, you will find data for which flights mid air refuelling is worth it, how they want to make it happen, and some interesting facts.
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The airframe modifications would be complicated and require certification.
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How did aviation industry come to know about the drastic difference in air pressure in high altitude? After watching many documentaries about air plane crashes, it seems that aviation industry learned many of its lessons from disasters. For example, from the 2 mid-air explosion of de Havilland DH 106 Comet in 1950s they learned a lot about metal fatigue that can cause Explosive decompression. So, I'm curious to know how did the industry come to know about the drastic difference in air pressure that occurs in high altitude? Was the knowledge already there before an airplane was even invented? <Q> The entire reason why the Comet broke up in midair is because they pressurized the plane in the first place. <S> It was known for a long time that air at high altitude was thinner. <S> This can be experimentally verified by taking a barometer up to a mountain. <S> This was first done in 1648 (and subject to hot debate regarding the nature of air) more than 250 years before the Wright brothers first flew. <A> Aside from mountaineering investigations, the service ceiling of WWII propeller-driven aircraft like the Spitfire was pushed up from about 34,000 feet to 45,000 feet, so the general effect of reduced air pressure on aircraft and engine performance was already known. <S> Of course both civil and military aircraft were unpressurised before the start of jet-powered civil aviation (though there were some experiments with full-body pressurised suits, to avoid damaging the aircrew more than the plane at those altitudes). <S> I think the significant novelty was discovering the effect of cyclic stresses (a.k.a. "fatigue") in a new situation, namely of the order of 100 to 1000 loading cycles to failure. <S> Before that, the most common design consideration was one loading cycle, <S> where over-stressing caused immediate failure. <S> With a suitably large safety factor and fortuitous choice of materials, that design criterion would also give an "infinite life" for high-cycle fatigue situations like rotating machinery (e.g. piston engines). <S> New materials, plus lower safety factors driven by the need for minimum weight, discovered a new "cliff edge" for designers to "fall off" - and the history of engineering contains many examples of cliff edges being discovered by falling off them. <A> The difference between the troposphere and stratosphere was discovered by balloon measurements by Teisserenc de Bort in 1902. <S> Most passenger airlines fly in lower levels of the stratosphere. <S> No planes can fly above the stratosphere.
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The range of air pressure from sea level to the maximum ceiling of modern aircraft was known even before the airplane was invented.
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Is it harder to learn to fly rotary wing after learning on fixed? I have a private license for single engine land and I want to transition to helicopters. I have been told by some that learning helicopters is more of a challenge after learning fixed wing. However I have yet to see any good sources or explanation for this. Is this generally true and if so why? <Q> Rotary flying is much harder than fixed wing to learn, however learning after you get a fixed wing license is easier in some ways because you already know: <S> Radio procedures How to set up and use instruments Navigation and flight in controlled airspace Air law and regulations <S> The "gestalt" of flying <S> This means all you need to do is learn to fly the helicopter, which is tricky because helicopters are much less stable than fixed wing airplanes. <S> If you take your hands off the controls of fixed wing airplane it will generally stay pointed where you put it, especially if it's trimmed properly. <S> If you take your hands off of a helicopter's controls in hover things will go very, very badly in a real hurry <S> so you have to be making constant control inputs. <A> I think as a fixed wing pilot you will will have gained fixed wing "habits" that are not transferable to helicopters. <S> The main one I can think of is if your engine fails on a fixed wing, you may pull to reduce the speed to best glide and gain a few hundred feet of height. <S> This would be a disaster in an helicopter. <S> No doubt an helicopter pilot (of which I am not) would tell us that possibly in high speed cruise it might be possible to lose some forward speed and translate this into height, but what I am saying is that the primary consideration in an helicopter is not to lose rotor speed because the blades once stalled cannot be un-stalled (they are at the back side of the drag curve), even assuming they are undamaged at that point. <S> So in an helicopter you drop the collective immediately to preserve rotor speed. <S> I once heard somebody say that you needed 500 hours in helicopters if you were experienced in fixed wing, before that guy would let his grandchildren fly with you. <A> AOPA has a series of articles where a fixed-wing pilot learned to fly a helicopter. <S> One of his lessons learned supports the idea that it's harder to go from fixed-wing to rotary: <S> There is a negative transfer of learning from airplanes <S> All my aviation experience prior to flying helicopters involved a sort of building-blocks approach. <S> Each new skill was based more or less on the previous skill. <S> Additional class ratings simply came down to differences training. <S> Such is not the case with helicopters. <S> In some cases, fixed-wing knowledge is a hindrance. <S> This is especially true with low-G mast bumping in the Robinson. <S> Most poignant for me was when I was maneuvering for a steep approach <S> and I saw the airspeed bleed off fairly quickly. <S> My first thought was "stall!" <S> when I was actually right where I needed to be. <S> But if you read the whole series, he does mention transferable skills like radio work, regulations, navigation etc. <S> that are still useful, so while maneuvering the helicopter may be more difficult for a fixed-wing pilot at first, that isn't the only consideration in learning to fly one. <S> There are lots of opinions out there about transferring from fixed-wing to helicopters, but there doesn't seem to have been any systematic analysis or investigation about it. <S> As far as I could see, the FAA's Helicopter Flying Handbook doesn't say anything about transitioning from fixed-wing aircraft so either they didn't consider it at all <S> or they did but decided that it wasn't a significant issue. <A> As a fixed-wing pilot who transitioned to rotary, I would agree that the actual "stick and ruder" -- or "cyclic, collective, and directional pedals" -- part of flying rotary wing is harder than flying an airplane. <S> First and foremost, there are actually three different kinds of flight in helis: hovering flight forward flight autorotation and each of these three types of flight needs to be learned individually, has its own muscle memory , and its own set of gotchas. <S> Secondly, helicopters are unstable, meaning they must be flown hands-on at all times, and helicopter trainers (e.g., Robinson, Engstrom, Schweitzer), in particular, don't have stability augmentation systems , precisely so that the pilot learns to control the helicopter with the controls. <S> Third, and this is more intuitive than evidentiary, <S> helicopter aerodynamics are much more complicated than airplanes. <S> Trainer nose-wheel airplanes can be flown quite lazily, without much rudder input, and with unsubtle control input, and not have too much an effect on the flightpath or safety of the aircraft. <S> In a helicopter, every single input on one control (cyclic, collective, throttle, pedals) must be fully compensated for on every other control, to keep the aircraft from deviating from its flight path. <S> Fourth, the controls on a helicopter are much more sensitive than on an airplane, and must be handled with the utmost of care. <S> The operative phrase for handling the controls is to "milk the mouse," meaning to use very small control control inputs. <S> (My own instructor, when I was unsubtle on the cyclic would joke " <S> Hey Bob, are you making salad?") <S> Those are the flight control issues, but there are a few other operational issues with helicopters that make them more difficult: <S> helis often operate off-airport, including confined area and pinnacle operations, operating on slopes , operating on unimproved (or even unlandable) surfaces, all of which require specialized skills helis often carry external loads , which adds an additional handling complexity
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The controls of a helicopter are also very sensitive, it is a very different (and more challenging) type of flying.
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Why do reciprocating aircraft engines have more than one spark plug? Most reciprocating aircraft engines have two spark plugs per cylinder. What are the reasons for this? <Q> Bold Method has a great post today about why aircraft engines have more than one spark plug per cylinder . <S> There are a few basic reasons. <S> Reliability <S> Having two sparks plugs is more reliable. <S> If one spark plug becomes inoperative for some reason, there's a second to provide the spark for the power stroke. <S> It should also be noted that the spark plugs are usually powered by dual, independent magnetos or, in some cases, an electronic capacitor discharge ignition. <S> More Power <S> This point is demonstrated during run-up. <S> When the magneto check is done the engine RPMs drop when running on a single mag and set of spark plugs. <S> Even Combustion Two sparks plugs and a two flame front leads to a more even burn of the fuel air mixture for a smoother running engine. <S> Prevent Fouling Aircraft engines burn leaded fuel which can lead to getting lead deposits on the spark plugs. <S> Having dual plugs leads to a more complete burn which can prevent the deposits from forming. <A> Engine Longevity as well. <S> The more even combustion resulting from dual sparks prevents hot spots inside the cylinder, resulting in improved engine life. <A> Reliability is the key thing. <S> The ignition system of a gasoline engine (the "magnetos" in most aircraft) is absolutely critical to the engine's operation, and thus the safety of the flight of the aircraft possessing it. <S> A small break in a wire, or fouling of one plug, could cause cylinder misfires or even a total engine failure. <S> To guard against this, dual independent ignition systems are incorporated into aviation engines to allow for continued operation in the event that any component of one ignition system fails. <S> Efficiency is a secondary benefit. <S> Two spark plugs per cylinder means the spark initiates combustion at two points within the volume of the cylinder. <S> Combustion rate of a vaporized fuel is typically a function of "surface area" of the region of combustion, so two sparks equals double the combustion surface area. <S> This produces faster and more complete combustion, increasing power at a given fuel flow rate. <S> One of the rudimentary "runup" tests of a piston engine involves selecting one or the other magneto, and watching the performance of the engine. <S> The normal result with a healthy ignition system is a slight reduction in power, as indicated (in a fixed-pitch prop at least) by lower RPM. <S> A severe power reduction, rough operation or an engine quit is a sign <S> something's wrong on that side of the ignition system.
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Having two spark plugs means the flame ignites from two points leading to more power per power stroke. The redundancy of the ignition system adds to the reliability.
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Why is luggage required to be loaded in containers? Luggage is loaded into containers, in Wide Body airliners (as mentioned here ). Why is this required to be done? Why don't they simply keep the luggage in the luggage compartment? Why is loading the luggage piece-by-piece time consuming, and at the end, in second photo mentioned there, the luggage is being loaded piece-by-piece. What is that? <Q> The central cargo hold is usually pretty big and open, if cargo was placed in loosely then it might shift in flight which can cause the center of mass to shift or damage the walls of the hold. <S> Putting them in containers and fixing those down will prevent that. <S> The containers can also be weighed before hand and their position set to ensure the center of mass ends up where it should be. <S> With loose cargo the pilot would need to rely on the intuition and experience of the loaders to ensure that they don't put all the heavy stuff on one side. <S> Loading loose luggage requires that the loader in the cargo hold handles each bag while stacking them. <S> The hold also needs to be full enough that the luggage can't shift around. <S> The smaller forward and rear cargo holds (or on smaller planes) can still accommodate loose luggage (or <S> more precisely they are too small for the containers to fit). <S> They will also have netting to provide barriers against shifting. <A> Why is this required to be done? <S> As far as I know, this is not required by law, it is an operational practice by airlines. <S> According to Wikipedia <S> "It allows a large quantity of cargo to be bundled into a single unit. <S> Since this leads to fewer units to load, it saves ground crews time and effort and helps prevent delayed flights." <S> Why don't they simply keep the luggage in the luggage compartment? <S> baggage can be loaded into ULDs while the aircraft they are intended for is still in flight. <S> This reduces turn-around time. <S> Aircraft only earn money when they are in the air, on the ground they bleed money from the airline's shareholders. <S> Airlines try to keep aircraft in the air and avoid having them on the ground as much as possible. <S> Why is loading the luggage piece-by-piece time consuming <S> Because luggage is not of uniform size, shape and strength. <S> Therefore it is a labour-intensive process not especially amenable to full mechanisation. <S> It simply takes longer to load 50 (say) <S> randomly shaped objects than it does to load one object of standardised shape and size. <S> at the end, in second photo mentioned there, the luggage is being loaded piece-by-piece. <S> What is that? <S> I don't know, but it seems plausible that some passengers are willing to pay for their luggage to be carefully hand loaded. <S> I.e. first-class. <S> This allows those passengers to pay for an express boarding process and spend less time in the airport. <A> Well there are several advantages of loading the luggage in unit load devices (ULDs) such as: <S> In ULD, the luggage suffers much less shock than it would, if left alone. <S> Else, the incidence of baggage manhandling would increase several times. <S> We are already losing \$2.58 bn/year due to this. <S> ULDs lead to better use of aircraft cargo space. <S> Stacking the luggage one over the other would be a very time consuming and tiring job, and if it is not done, then a lot of cargo space of aircraft would be wasted. <S> ULDs help prevent this. <S> ULDs are cost effective. <S> Compare the cost of 100s people busy in stacking the luggage, and one conveyor belt doing the job. <S> ULDs are safer, in the way they prevent unauthorized access to the luggage. <S> And, in the second picture shown there, the luggage is being loaded into luggage hold. <S> Which has several Pallets/Nets for storing small ammount of luggage. <S> Usually, they are used to store some small cargo belonging to first class passengers. <A> Think about the benefits of containerisation. <S> Ships could take days to unload if they carried many different items like lumber, sacks of corn etc. <S> Along came containers and now you can unload a ship in hours. <S> The labour intensive part of loading/stacking is distributed toward the containers themselves, and thus frees up the expensive capital item such as a ship or plane to be turned around more quickly. <S> It all makes economic sense. <S> so is it required? <S> yes, if you wish to stay competitive and in business it is. <A> There are some safety and security aspects to containing luggage within containers. <A> Also, if the airline is feeding flights to other destinations, baggage can be pre-sorted. <S> For example, a flight into CMB (Colombo, Sri Lanka) is commonly used as a feeder service for onward travel to MLE (Male, Maldives). <S> If all the MLE-destination bags are separated from the CMB-destination bags at the time of loading and are in their own ULDs, those ULDs can be simply moved into the MLE aircraft, saving the time to offload all bags, re-sort and separate the MLE ones, and then reload.
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When content leaks, goes bad, or even explodes , the container may serve to limit the damage to other luggage within the aircraft, along with the aircraft itself.
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Do Cargo flights carry anyone other than the crew? This question talks a bit about the crews that are involved in a commercial cargo flight, but I'm wondering if Cargo flights every carry other sorts of people on their flights? Say, a photographer to take pictures of operations for advertising or something. Or maybe one of the crews kids who want's to see what Mom does or something like that. Or, perhaps there's even another person who's normally there? If they do, here's a couple bonus questions: Do they have jump seats? And are they in the cockpit, or in the cargo hold? (Just in general, I assume different planes have different setups). Are there any regulations regarding this? <Q> Yes, cargo aircraft are like other aircraft in that there is generally at least a jump seat available. <S> Especially larger aircraft will also have additional jump seats, a lavatory, and a galley . <S> This area can be used for relief crew, or other crew that are just deadheading . <S> There are exceptions though. <S> The upper deck of the 747 is larger than just the cockpit, even on the cargo versions . <S> There is more room in the back for additional crew. <S> The An-124 <S> and An-225 also have additional space for crew behind the cockpit. <S> The extra crew can be loadmasters, navigators, mechanics, or other functions that can make it easier to operate in and out of airports with less services available. <S> Here is the upper deck of a 747-400F: <A> I spent many an hour crammed into the jumpseats of 727's (they have 2, both in the broom closet sized cockpit with 3 crew members). <S> I worked as a cargo handler at the FedEx hub in Memphis and at the time we could book any open jumpseat. <S> When i clocked out at 4am there were a couple hundred planes just about to depart for destinations all over the world. <S> It was awesome, but alas, no more. <S> It even continued after an off duty pilot with a hammer decided to try and hijack one of our planes from the jumpseat. <S> But 19 jerks ended all that on Sep 11, 2001. <S> There are still non-crew persons in the jumpseat but now you have to have a good reason to be there. <S> So if they need a mechanic somewhere or something like that they can go. <S> As far as what jumpseats there are it differs by aircraft. <S> Like i mentioned the 727's had 2 terribly uncomfortable seats in the cockpit. <S> The dc10's I've flown on had one in the cockpit and either 2 or 4 against the bulkhead facing backward. <S> [Think Tom Hanks in Castaway. <S> That was very accurate, you're staring at the first set of cargo containers behind a safety net the whole flight.] <S> In the 747-100 there were about 10 airline seats in the upper deck and two bunks at the back. <S> The 747-200's were the nicest. <S> They were formerly passenger planes so the upper deck still had the first class seating. <A> Some airlines operate their aircraft in a combination of freighter and passenger aircraft. <S> See here for the floor plan of KLM 's Boeing 747-400M Combi . <S> It has a large cargo door at the rear fuselage for loading freight containers. <S> Humanitarian relief flights have an obligation to carry journalists along if they wish. <S> Some governments have instituted a policy of transparency so the press may observe first-hand where the goods are delivered to. <A> Yes actually I have an uncle who flew on a c-130 cargo plane to Alaska that was carrying jet fuel if you consider that cargo. <S> The plane he was on was refueling jets in the sky. <S> And it usually when its only necessary.
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So yes sometimes they do carry people on planes with cargo. It's mostly deadheading pilots but anybody that has an "operational need" for the company can jumpseat.
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What data did the earliest HUDs display (for fighter jets)? Ideally I'm looking for a screenshot with a bullet list of data. I started my search at the obvious encyclopedic site and was surprised to learn that the earliest HUDs (on fighter jets) go all the way back to the 40's. So what data did they display? Presumably it would be a limited set of data compared to today's standards, and I'm very interested in what was considered the most important data for a HUD. Especially, did they have that circular piper showing where your bullets would impact? <Q> Reflector Sight: <S> The Me 262 Schwalbe , introduced in 1944 as the world's first operational jet fighter aircraft, did not have a full-blown HUD. <S> Instead, like many fighters of WWII, it had a reflector sight which used lenses and reflecting glass to display a reticle. <S> This sort of thing <S> [all of the bright yellow lines you see in the image are fixed together. <S> Although you only really needed a dot and a circle (like the Spitfire), some pilots liked the extra lines to help line up targets that were not dead-ahead. <S> They were favored by pilots over iron-sights because the pilot was not required to position his head in order to see where the guns would fire. <S> Simple HUD The MiG-21, introduced in 1959, used a combination of reflector sight and HUD. <S> Here is a guide on how to aim your guns using its sight. <S> Also, explanations of the displays. <S> The following image was posted on a forum thread related to the MiG-23, which came after the MiG-21, but this image looks much like those from the MiG-21 manual. <S> A different image from another author shows you how simple the display could get. <S> Finally, an F-16 in the sights of a MiG-21 . <S> You can tell this is a MiG because of the distinctive pitot tube . <S> Full HUD <S> The F-14 first flew in 1970. <S> Its HUD was equipped with an artificial horizon, altitude, speed, heading, gun data, missile data, and much more. <S> This is from the F/A-18, which first flew almost a decade later. <A> The earliest were reflector sights which were fitted to fighter aircraft at the end of WW I. <S> The picture below shows an Oigee Reflexvisier from 1918, built at the Optische Anstalt Oigee factory in Berlin-Charlottenburg and used that year in Albatros, Fokker and Pfalz D-type aircraft. <S> Two types were built and were the first, albeit very simple, head-up displays. <S> Oigee Reflexvisier (picture source ) <S> Only the height of the mirror needed to be adjusted for the sitting height of the pilot. <S> The brown plate in the path of light was used for this adjustment and removed for operation. <A> Computing (Gyro) <S> Gunsight <S> As a development of the existing "reflector gunsight" (which as other answers note was intended to eliminate parallax error due to the pilot's head position), the " computing gunsight " used the motion of the aircraft it was mounted on to generate a modified gunsight indicating the lead required to shoot a moving target. <S> A ring was projected onto the reflector, such that holding the target steady in this ring would provide the correct lead. <S> An estimate of the target's range first had to be set on the gunsight. <S> In practice, this was often left at the convergence range of the guns, and the pilot would attempt to manoeuvre the target to that range. <S> The first production models were produced in Britain in 1941, and successfully used against the Luftwaffe. <S> In 1942, a Thunderbolt with a computing gunsight was captured in Germany, which stimulated their efforts to develop similar technology. <S> In this early technology, no corresponding information about altitude, airspeed, heading or attitude were provided, being left to conventional instruments. <S> The Sperry K-14 was considered notable for including both computing and fixed (ie. <S> equivalent to a reflector sight) gunsights in the same unit.
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Though it didn't display the altitude, speed, heading, or attitude in a way that modern fighter pilots may take for granted, it had some ability to track targets with radar and to display predicted target positions for gun or missile use. What was displayed was basically a single dot of light which was projected on the semi-transparent mirror such that it would overlay the point at which the fixed guns were aiming, regardless of the pilot's eye position.
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What keeps Russian airliners from being as fuel efficient as their Western counterparts? Peter Kampf points out in his answer on IDing Tupolevs that the Russian transport aircraft designs tend to be quite aerodynamically refined, in some ways better than their Western counterparts on that front. What kept them from matching the West when it came to fuel efficiency then? Was it purely a matter of the Russian need to build sturdy aircraft to withstand their rough strips in the middle of Siberia? Or were there other factors, such as engine technology, in play? And have the Russians "caught up to us" regarding aircraft fuel economy, or are they still trying to get the hang of building fuel-sipping airplanes? <Q> The engines. <S> Russian engines were for decades behind the state of the art. <S> One reason was manufacturing tolerances. <S> I remember that we studied the Progress D-27 three-spool turboprop and found that just the cast casing could be made 250 kg lighter with Western tolerances. <S> The Russian designers kept their tolerances wider to make sure that the minimum wall thickness would not be undercut. <S> Also, since Russian designers had less powerful computers available to them, they could rely less on CFD, so the turbo machinery was less refined. <S> Improved engines explain maybe two thirds of the increase in fuel efficiency over the last 70 years. <S> Another reason is system redundancy. <S> Especially the military designs were built with the goal of maintenance-free operation for several weeks. <S> This thinking was also applied on the civilian side, since all Russian aircraft were designed with dual-use in mind. <S> In case of war, all Aeroflot planes would become military transporters, and Aeroflot crews received most of their training on military aircraft. <S> Why else would designs like the Tupolev <S> Tu-134 have a glazed nose? <S> Tu-134 <S> (picture source ) <A> This is my own take on this interesting question. <S> I've been reading about Soviet space and aviation realms for what seems like a lifetime. <S> Here is the general knowledge I've accumulated: The lion's share of resources went to the military, which meant they got the best aircraft engines. <S> Also, most "new" (post-WW2) military planes wanted turbojets for supersonic speed, whereas civil planes would benefit much more from turbofans (a pretty new concept at the time). <S> So many jet airliners got turbojets too for several decades IIRC. <S> For most post-WW2 Soviet history, petrol was very cheap and so the economic incentive like we see today just didn't exist. <S> This cheap petrol also existed in the US for a time, but the crunch came much earlier (1974 arab oil embargo IIRC, which didn't affect USSR. <S> In fact, the raised oil prices actually benefited USSR selling their native petrol at higher prices). <S> This eventually changed in the 80's IIRC (petrol in Baku drying up), by which time a whole contingent of other economic problems were stacking up and civil aviation just wasn't a priority. <S> Soviet aircraft place more emphasis on being able to takeoff from poor, dirt fields (for military reasons), which adds weight to the landing gear and maybe fuselage frame. <S> Soviet aircraft place more emphasis on cold-weather durability, which includes not just lower extremes in the envelope, but also just the general operation in temperatures which are on average colder than in US. <S> This adds weight to engines and other parts (I believe hydraulics? <S> plus any moving exterior joints?). <S> WW2 completely destroyed the Soviet economy. <S> This is sort of going beyond "the reason <S> is poor engines" and giving a reason for the reason, but it is relevant. <S> The exact opposite happened in America, where WW2 was economically a boon that completely reversed the Great Depression. <S> It seems like there are some more <S> but I can't think of them. <S> Will edit later if necessary. <A> Every aircraft manufacturer has their philosophy in designing the aircraft, depending on their experiences (regulatory conditions, economy, availability of materials etc.) <S> The Russians are the largest producers of crude oil and have no incentive to produce fuel efficient aircraft. <S> Though the Russian aircrafts are aerodynamically equal to their western counterparts, their fuel gulping engines mean that they are as a whole, inefficient. <S> This is because most of the fuel savings realized in aircraft are due to improvements in engine fuel consumption than due to aerodynamic improvements - 69% to 27% ( Lee, J. J., Lukachko, S. P., Waitz, I. A., and Schafer, A. (2001). <S> "Historical and future trends inaircraft performance, cost and emissions." Annual Review Energy Environment, 26, 167-200. ). <S> Improving the fuel efficiency of the engines requires not just a lot of research in aerodynamics, but also in materials (as the efficiency directly depends on the turbine temperature) and new manufacturing techniques. <S> The Russians most probably had decided that it is not worth the cost and effort. <S> However, this slowly changing as they try to export their aircraft to other countries in the world which demand better fuel efficiency. <S> Still, they have a lot of catching up to do with their western counterparts.
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Factories are expensive, so they tended to use the same military engines on civil aircraft that optimally needed a different engine design. Russian engineers made sure the aircraft would still be operable after being maintained by a substandard maintenance crew.
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How do combat jets know when to launch flares to counter IR missiles? From my related question , it seems fighter jets do not usually track missiles by radar. Instead, they have a system that warns of radar lock. So what about infrared missiles (heat-seeking missiles)? Flares are a countermeasure to these, so how does the jet know when one is incoming? I would be pretty surprised if such a system didn't exist. I want to know more about that system and when it was first implemented. <Q> Actually most aircraft don't actively know when a missile is being fired at them. <S> I have worked on helicopters and fighters that deploy counter measures. <S> The first is an IR jammer which we call a disco ball. <S> It is made up of mirrors at different angles that resemble a disco ball. <S> It radiates an IR signal at different angles to confuse the missiles. <S> The flares or chaff are fired periodically in known hot spots. <S> This creates heat signatures similar to the engines and confuses the missiles. <S> There are active systems <S> but they don't work well. <S> I have seen a helicopter in testing suspended from a wire with countermeasures turned on. <S> A missile was fired and the countermeasures didn't even get deployed. <S> This is why they usually keep firing the flares or chaff in known hot spots. <S> Hope that helps. <A> Before continuing, much of the how's and why's of IRCM are going to be either speculation, or classified. <S> Nations will not freely discuss their actual methods of defeating opposing nation's IR capabilities. <S> Therefore, actual answers will be difficult to give. <S> However, here is an excerpt from Wikipedia regarding a specific missile warning system that may be found on military aircraft. <S> This represents one possible method used for certain types of aircraft. <S> The AN/AAR-47 Missile Warning System is a Missile Approach Warning system used on slow moving aircraft such as helicopters and military transport aircraft to notify the pilot of threats and to trigger the aircraft's countermeasures systems. <S> The AN/AAR-47 passively detects missiles by their infrared signature, and uses algorithms to differentiate between incoming missiles and false alarms." <S> https://en.wikipedia.org/wiki/AN/AAR-47_Missile_Approach_Warning_System <A> The infrared missiles are usually detected using a Missile Approach Warning Sensor (MAWS). <S> The infrared based systems detect the infrared waves emitted by the missile. <S> The ultraviolet based systems detect the ultraviolet rays emitted by the missile's rocket motors and are more suitable for detecting missiles with solid rocket motors. <S> An example for the infrared based detector is the US-Israel PAWS, while the Swedish MAW-300 uses an ultraviolet detector. <S> Some systems like the MWS-20 uses Doppler Radar to detect the missiles. <S> All these systems have their advantages and disadvantages, and in relation to your previous question, give a 360 degree coverage based on the location of their installation. <S> In most of the aircraft, these detection systems, along with the Radar Warning Receiver, which detect the Radar based missiles are integrated into the Self Protection System(SPS), which determines the threat level of the incoming missile and responds accordingly by firing chaff and flares.
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The Missile Approach Warning Systems are passive detectors, usually detecting either the infrared or ultraviolet rays emitted by the incoming missiles.
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Why are airport firetrucks painted yellow green? In my city, most of, if not all of the fire-trucks that serve city emergencies are red , just like this one: But every time that I see an airport emergency that requires the fire-fighters, I see this kind of truck: Is there a reason why the airport trucks are yellow-green and not red? <Q> Yellow/green is also more easily identified by people with colour blindness and other visual disorders. <S> It's the same reason that safety vests are yellow/green. <S> This article gives some good references. <A> While Simon has told you about why ALL Fire Engines SHOULD better be yellow/green, not red, he did not tell you why all Airport Fire Trucks you have seen are yellow, and all normal Fire Trucks you have seen are red. <S> PBS's "Firehouse Primer" on the history of red fire engines: <S> Before firefighting was a paid profession, most communities were served by volunteer fire departments. <S> These firemen didn't have much money to spend on upkeep, and at the time red was the least expensive color of paint. <S> Red wasn't the only color used, however. <S> Before it merged with the force in Manhattan, the Brooklyn Fire Department painted its apparatus a two-tone green to distinguish them from the red apparatus of the Metropolitan Fire Department. <S> Today, there are still different colored fire engines, but red is the most common color out of tradition. <S> I don't know whether this is true or just an anecdote, but it's a nice story nevertheless. <S> While in the US, where fire fighting is a local issue, you will see yellow fire engines with some fire dept's (mostly in rural areas, I guess it's because you have long unlighted stretches of street there), in your native Brazil, the central government has decided to use red for all engines. <S> This is the same in my native Germany, where the color mandated by law for fire trucks used on public streets has changed slightly over the years, from a dark red over a orangeish red to a retroreflecting orange-red. <S> So I guess that you have only been to red-engine territory until now. <S> For airports, it's a different issue: Unless ordered otherwise, Oshkosh's (the US market leader) <S> airport fire engine lineup is painted green/yellow. <S> Rosenbauer (big player in Europe) on the other hand has a red lineup. <S> While you can order other colors, most customers stick to the default. <S> So my best guess is that you haven't attended any plane evacuations in Europe until now. <A> It's because it is the color specified by the Federal Aviation Administration and the only color of firefighting vehicle they will participate in funding. <S> Advisory Circular AC 150/5210-5D states <S> Aircraft Rescue and Fire Fighting (ARFF) Vehicles. <S> Yellowish-green is the vehicle color standard. <S> and APPLICATION. <S> The Federal Aviation Administration (FAA) recommends the guidelines and standards in this Advisory Circular for vehicles operating in the airport AOA. <S> In general, use of this AC is not mandatory. <S> However , use of this AC is mandatory for vehicles funded with federal grant monies through the Airport Improvement Program (AIP) <S> and/or with revenue from the Passenger Facility Charges (PFC) Program. <S> See Grant Assurance <S> No. <S> 34, “Policies, Standards, and Specifications,” and PFC Assurance <S> No. <S> 9, “Standard and Specifications.” <S> [emphasis in original] <A> Humans evolved in sunlight, which produces mostly yellow-green light frequencies. <S> Therefore, we are most sensitive to the yellowish green part of the visible light spectrum. <S> This is why safety vests are yellow-green. <S> Airport firetrucks and new firetrucks are slowly starting to be painted yellow-green instead of the traditional red. <S> There has been research which shows that firetrucks of this color are less accident prone than red ones. <S> Hope <S> this was helpful (:
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Because yellow/green has been shown to be more visible than red, especially in low light conditions. The Swiss, where fire fighting is a local issue as well, have mostly switched to yellow fire engines for visibility reasons.
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How do you hold at a non-towered airport? Let's say, hypothetically, that you enter the pattern for a small, non-towered airport (my local one, 3DW , may be a good example.) But as you get into the pattern you find out that the runway is occupied by another craft and, for whatever reason the runway will probably be occupied for another 20 minutes, much longer than it will take you to complete the pattern. So you'll have to delay landing. But you've already entered the pattern, so what should you do? Is there a standard holding pattern for small airports that incorporates parts of the pattern (maybe some little loop where the base leg and downwind meet)? Or do you just fly away form the airport a bit and make up your own holding pattern? <Q> There's no "standard holding pattern" at any airport, towered or not. <S> If the runway is occupied or temporarily closed for some reason, you might was well leave the traffic pattern and go putt around for a while someplace where there are fewer aircraft. <S> At a towered airport, the controller will likely tell you what to do - but again, you can make both his life and yours easier by just leaving the pattern and going somewhere else until the situation is resolved. <A> Given that you want to stay in the pattern you could use the upwind leg to avoid flying over the runway. <S> This is, from base <S> go to upwind, then crosswind, etc. <S> As others posted there is no standard holding pattern. <S> For VFR traffic there are no holds either. <S> The pattern may become congested quickly. <S> Your best bet is to divert until the situation improves. <A> As far as I know, there's no such thing as a "standard holding pattern" for uncontrolled fields, though I suppose Center might put you in some holding pattern if you're IFR. <S> For VFR, though, if I found out that the runway was going to be unavailable for 20 minutes (and was reasonably likely to be open again after that time <S> and I had plenty of fuel,) <S> I'd just leave the pattern and fly a few miles away from the airport for a while. <S> I'd then continue to monitor the CTAF to hear what's going on <S> and if/when the runway is open again. <S> If it seemed like it was going to be a while, I'd just go land at another nearby airport. <S> Most of the time, however, delays at uncontrolled fields will be brief <S> (i.e. someone is back-taxiing, is taking off, is on final, or just landed) <S> and you can just either make a 360 or a 270 degree turn to base (to the opposite direction as normal) to waste time until the runway is clear. <S> Normally, this won't be more than a couple of minutes at a time. <S> Normal checks, configuration changes, etc. should be made before entering the runway, so you won't normally encounter longer delays unless there's an actual problem of some sort. <A> In order to answer this question the terminology and procedures must be clarified. <S> If it's going to take 20 minutes the airplane would need to depart the pattern and return later. <S> The use of the word hold is out of context here. <S> As defined by the Instrument Flying Handbook : Holding is a predetermined maneuver which keeps aircraft within a specified airspace while awaiting further clearance from ATC. <S> The way the question is asked it reveals that the person asking assumes that a hold is something performed in an airport traffic pattern, but it is not. <S> A hold would be used at an enroute altitude and outside the immediate terminal aerodrome environment where traffic patterns are flown. <S> If a runway were unavailable for 20 minutes and an airplane were enroute on an IFR flight plan, ATC might issue that airplane a hold which is published on an instrument approach procedure for that airport. <S> The airplane might hold there for 20 minutes until the runway became available again. <S> This scenario would happen before the airplane reached the traffic pattern or after it departed it.
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If an airplane is in the airport traffic pattern and the runway won't be available by the time by the time it would reach it, the airplane can extend the traffic pattern to give the runway time to be available for landing.
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How can I know where wind is coming from by looking at water? For ground reference maneuvers, I know there are many ways that I can know wind direction: smoke, circling, weather reports from nearby airport and so on. However, how can I determine the wind direction by looking at water? I've tried to look for detailed explanations about it but I have found nothing useful. Can somebody help me to understand this issue? I would appreciate if there is any graphic materials. <Q> Barring that there are a bunch of other clues that should be familiar to any sailor (or seaplane pilot) which you can borrow: <S> Boats lying at anchor weathervane and automatically point into the wind This isn't 100% reliable: Some boats will set two anchors (fore and stern) and won't weathervane. <S> Also when the tide is shifting boats will swing to align with the tide if it's stronger than the wind. <S> Boats lying at anchor sometimes have a flag on them Flags on a boat at anchor work the same way as flags on land - they're excellent indicators of wind direction. <S> On calm bodies of water the wind creates visible surface ripples <S> The concave side of these ripples is the windward side. <S> (Visualize the water as being a large bowl of soup - now blow on the soup. <S> The ripples will have the same shape.) <S> This same principle applies to larger waves as well (other factors could cause the dominant breeze along a shoreline to not be quite perpendicular to the waves, but if your concern is ground reference maneuvers <S> it's "close enough"). <S> "Wind Streaks" on the sea indicate wind direction <S> Wind streaks are somewhat ambiguous in that they're aligned with the wind, but don't tell you which way <S> it's blowing: You have to figure that out for yourself (for example by looking at the shape of the waves as described above). <S> Surf spray gives wind speed and direction Waves breaking will produce spray that blows downwind <S> - I couldn't find a good illustration for this, but the finer spray tends to blow, while heavier drops just fall. <S> The distance the spray blows gives an approximate indication of wind speed. <S> It would take some pretty heavy seas to produce visible spray at altitude though, and you're more likely to see foam and whitecaps in that case <S> Foam or Whitecaps provide wind speed and direction Foam or whitecaps provide an indication of direction (the foam appears to move upwind - into the wind) and speed (it generally takes winds of 10-15 knots or more to produce whitecaps and foam). <A> Waves move in the direction of the wind, and form long lines. <S> Cresting waves always break downwind & whitecaps are generally pretty easy to spot. <S> So look for parallel lines of waves. <S> A line perpendicular to the wave-line will be directly-into / directly-away from the wind. <S> If the waves are very large or moving very slowly, it may be hard to determine which direction they're moving, but at least you'll have an axis for the wind direction. <S> If the water is calm enough that you cannot figure out wind direction, it generally means there isn't much wind to speak of. <S> It generally only takes a couple knots of wind speed to make discernible waves. <A> On inland bodies of water (lakes, ponds, etc.), as the wind blows across the ground the water will be calm on the side where the wind blows from. <S> It's hard to get a good photo with an iPhone at 10,000 feet, but this shows a pond with calm water on the left and waves on the right. <S> The wind blows from the left. <S> This photo was taken close to sunset so the difference in surface characteristics of the water is pretty dramatic, but this can be seen in just about any light.
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The easiest way to tell the direction of the wind when you're near the water is to look for something on the shore that indicated wind direction (beaches often have flags on them)
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Why does the Cessna 172S Skyhawk use only two blade fixed pitched prop? Surely it would get more thrust from a three blade variable pitch propeller. From what I've read it's all about the area swept and also should be far enough apart to not cause too much interference. Besides having a constant speed prop would allow for a wider range of optimum operation. <Q> You're not wrong, but a fixed pitch two-blade prop has a pretty big advantage: it's cheap . <S> Cheap to buy, cheap to install, cheap to maintain, cheap to repair. <S> 172s are predominantly trainers in FBO fleets, and cheap is the winner. <S> The efficiencies of a better prop are lost when you're just doing pattern work and short cross countries. <S> According to the linked Hartzell FAQ: Depending on the combination of [engine power, operating RPM for the propeller, diameter limitations, design requirements, etc] <S> a 2-blade propeller may be most efficient, but as power increases additional blades are generally required to efficiently utilize the increased power. <S> This means that on a 160 horsepower engine like the 172 is rocking, you aren't going to see particularly tangible benefits from increasing the number of blades. <S> Going to a constant speed prop would, on the other hand, give you greater utilization of power across the entire flight envelope. <S> For example... <S> An overhauled McCauley fixed pitch 2-blade propeller that fits a Cessna 172 is $2,100 on ebay. <S> It has no moving parts (I mean, aside from itself ) and is relatively easy to balance. <S> A (non-overhauled?) <S> Hartzell 3-blade <S> constant speed prop off <S> a Piper PA-46-350 Malibu Mirage is $15,000 on ebay with no logs , which is usually a bad sign. <S> It's not a direct comparison to, say, the prop on a C182, but it's probably in the ballpark. <S> It's harder to balance, and requires more maintenance to make sure the constant speed mechanism is up to snuff. <S> I was only able to find prices on ebay, which isn't the most scientific comparison ever, but it's a start. <A> My first few lessons in the circuit were busy enough just getting the altitudes, positioning, radio calls and checks completed correctly. <S> When I did differences training for variable pitch a few years later it suddenly became busy again, simply from trying to remember what the RPM and MP settings I was supposed to be using at each stage (generally 5 different combinations per circuit). <S> It's not much harder, admittedly, but just having one dimension (the black throttle knob goes forward for more power or back for less power) was easier on my already over-taxed student brain than the two-dimensional variable pitch setup (black knob for power, blue for RPM; with blue going forward both when you want more power (takeoff) <S> and when you're decreasing power (short final, in case you need to go-around)). <A> For a given horsepower two blades are more efficient than three, three more than four, and so on. <S> There are a few reasons to have more than two blades: <S> -the engine generates so much power that a two blade prop would need to be so long that it would contact the ground. <S> -the engine generates so much power that a two blade prop would need to be so long that the velocity of the blade tips would exceed the speed of sound. <S> -the application of the aircraft requires acceleration and climbing ability over top speed. <S> More blades for a given power equate to slower top speeds but better takeoff acceleration and rates of climb. <S> -in <S> the case of the V-tail Bonanza, the added weight of the three blade moves the CG forward making loading easier. <S> The most efficient prop for a given hp is a single blade (it exists). <S> Plenty of examples in Google images. <S> The cost and manufacturing/maintenance aspect are other considerations and have been addressed in other answers.
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Also, when you're not climbing, a two-bladed prop is actually going to be more efficient, not less as it's creating less drag. I can't improve on @egid's answer on efficiency or cost, but another point on constant speed units is related to 172s predominantly being trainers: fixed pitch props are easier to fly.
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Can bird strikes be dealt with by throttling down engines to idle? From a related question , I got to thinking about bird strikes again and the fact that they are sucked into the engine at great velocity. If a pilot had 5 to 10 seconds of warning time, would throttling down the engines to idle be a good idea? Would it save those engines even if a bird hit the intake fan? This would of course be a temporary measure, intended to prevent the birds being sucked in harder or faster than otherwise. Once the birds passed, the engines would be throttled up again. I'm thinking about large commercial jets like the Airbus A320. EDIT: one concern I have is that at high throttle, the engine will suck in objects from a wider area than just the engine inlet . Is this assumption true? <Q> A goose can easily be flying at 40mph and a commercial jet will be landing at about 150mph, giving a closing speed of about 190mph (305km/h). <S> That means that, to spot a goose with 10s warning, you would need to spot it when it's more than half a mile away. <S> Not only would you have to spot that tiny speck of a goose half a mile away during the busiest phase of the whole flight, but you'd also have to immediately work out whether the tiny speck was even coming towards you. <S> If it was, you'd have to estimate whether it would even hit the plane. <S> Then, supposing you'd immediately and accurately recognized the danger to your plane from that tiny speck, you'd have to immediately reduce power to the engines, while being very careful not to hit the ground the bad way. <S> In short, regardless of how much better the outcome of a bird hitting an idling engine would be than one hitting an engine under power, it's just not feasible to try to power down the engines. <A> In general, greater the engine thrust, greater the damage caused due to the bird strike. <S> This is to both the higher speed of the compressor blades and the pressure ratio. <S> So, it makes sense if the pilot can throttle down the engines if bird strike is imminent. <S> In fact, approaching in idle condition is on of the strategies for reducing the possibility of bird strikes. <S> See http://www.boeing.com/commercial/aeromagazine/articles/2011_q3/4/ and http://www.skybrary.aero/index.php/Bird_Strike_on_Final_Approach:_Guidance_for_Flight_Crews . <S> However, there are other things to consider. <S> For example, most of the bird strikes happen during take off and landing and it is not advisable to throttle back the engines at that point of time <S> (it is one thing to descend in idle power and another to reduce power during landing). <S> Also, given the speed of the aircraft and the size of the birds, it is unlikely that the pilot will have enough warning unless he's approaching a huge flock. <S> Another thing is, given that the velocity of bird strike is a function of both aircraft speed and compressor speed, reducing to idle power won't prevent damage due to bird strike as the compressor rotates at a very high speed even in idle condition. <S> In any case, modern engines are designed to operate (or fail safely) in the event of bird ingestion and it is far better to continue the flight and take appropriate action like go around and land. <A> "would throttling down the engines to idle be a good idea?" <S> Probably not, 3 reasons I can think of. <S> Landing speeds for an Airbus A320 (your example) will typically be in the region of 130kt to 140kt faster then the cruise speed of many GA aircraft. <S> Even at those speeds, a bird strike is likely to have a significant impact on anything it hits. <S> The published minimum speed of the high pressure compressor/turbine spool is 66% of the rated maximum. <S> Since the max turbine speed is VERY fast think 20-30k RPM, 66% of it is probably enough to cause any damage that would occur with a normal strike. <S> In the unlikely even you see the birds with more than 2-3s to react (there very hard to spot at high speeds), you would more likely want to INCREASE thrust to A) try to outmaneuver the bird and B) in case of an engine failure the other would already be running near the power required for continued flight on one engine (essential since most bird strikes are at lower altitudes where you may not have enough altitude to reduce power for 10s or so <S> then power back up to max thrust taking another few seconds) <S> EDIT: <S> an argument could be made for not touching the throttles at all until you can total verify one or more engines have failed based on the number of pilots, who in a panic manage to turn off the wrong engine during an emergency. <S> Note. <S> referenced speeds are approximate I would welcome edits with more specific data. <A> To answer your question "Can they be dealt with", I think throttling down is nowhere near a total solution, although it might have a small effect. <S> The big problem is that the aircraft is typically flying at a speed of between 130 and 250 knots towards the birds. <S> The engines don't suck the birds in (because there is relatively little time for this to have an effect) the birds just get in the way of the engines and the impact forces of a 10 lb bird doing between 130 and 250 knots (relatively) do the damage.
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Once you take into account the false alarms, which would vastly outnumber the actual bird strikes, trying to power down the engines would probably be far more dangerous than just hitting the bird.
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Why are twin engine airliners more fuel efficient than three or four engine airliners? It is said that given roughly similar aerodynamic and engine technology that twin engine airliners are more fuel efficient than 3 or 4 engine airliners. Why is this? The twin engine airliners tend to have more excess power so I'm thinking that they can climb faster and fly higher, lowering the amount of time spent climbing (uses more fuel than cruise) and lowering fuel consumption during cruise. I suppose that fuel consumption is less while the engines are idling as well. Are there other factors that go into the 2 vs 3 vs 4 engine fuel consumption issue? <Q> Not a fully definitive answer, but a large part of the "efficiency" of an aircraft is drag and weight. <S> Two (larger) round engines will have less surface causing drag than four smaller ones. <S> In addition, each engine will add complexity to the aircraft (fire monitors, fuel piping, extra hydraulics) as well as necessitating duplication of things like thrust reverses, all of which add extra weight and sometimes drag. <S> So, all things being equal, one huge engine would be most "efficient". <S> This would obviously be difficult, and impractical for most passenger jets, so when they will fit, without scraping the ground, two are used. <S> If more thrust is needed, then they break it down into three or four. <S> (Note, the main reason 4 engines were used in the first place <S> was for redundancy. <S> At least one country's [US?] <S> regulations stated that the aircraft must be capable of sustained flight, including climbing, with the loss of an engine. <S> 2-1 = 50% thrust lost where as 4-1= only 25% loss, therefore requiring less reserve power) <S> *Edit note #2 <S> "Twin engine airliners tend to have more excess power" they climb faster <S> may be relevant in terms of efficiency, but part of the reason a twin will usually have more reserve thrust is due to the redundancy "keep flying" rules described above. <A> Part of the reason is that large engines tend to be thermodynamically more efficient than small ones, and this isn't specific to any one type of engine. <S> Theoretical engine cycle is understood in terms of compressing, heating, expanding volumes of gas in an ideal environment. <S> The closer the engine approximates to that environment the closer the engine can get to its ideal efficiency. <S> Relatively cool metal surfaces like combustion chamber walls, or pistons and cylinder liners, detract from this, so <S> the further you can keep the gas from the metal, (i.e. the larger the engine) the more efficient (for the same theoretical cycle). <S> Off-topic, large marine diesels can exceed 50% thermodynamic efficiency while small diesels may reach 40% as seen here . <S> The same table shows this applies to gas turbines too, comparing a 36 MW gas turbine (Trent, 39.8%) to a 2.20MW one (P&W PW127, 27%) but these are just example numbers, not a really fair comparison. <S> (It would be nice to see like-for-like-but-bigger comparisons) <S> So larger engines tend to have higher thermodynamic efficiency, it just so happens you also need fewer of them. <A> I'm not sure if the twin engined aicraft are more fuel effecient compared to their four engined counterparts. <S> Is there any hard data available? <S> See http://www.transportenvironment.org/sites/te/files/media/2005-12_nlr_aviation_fuel_efficiency.pdf . <S> For example, the Boeing 747-8 first flown in 2011 is more fuel efficient compared to the 787-8 which flew first in 2009 while being less efficient compared to 787-9 (which flew in 2013). <S> It is instructive to note that the 747-8 uses the same engines as 787-8. <S> We can say the twinjets are more efficient because of the engines used in them. <S> Almost all the aircraft under development are twinjets, with the A380 being the last 4 engine aircraft to enter (commercial) service. <S> These aircraft incorporate a number of recent advances in the field (like increased use of composites along with better engines), which makes them more fuel efficient. <S> So, there is no reason to say that twinjets will be more efficient than four engines aircraft, but are usually so because of various other developments, which are also equally applicable to the four engined types. <S> Note <S> : See the References given in https://en.wikipedia.org/wiki/Fuel_economy_in_aircraft for comparison of fuel effeciencies of aircrafts.
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In general, newer aircraft are more fuel effecient compared to older ones.
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Why do spoilers seem to be slightly activated during take off? In this video (minutes from 10:46 to 11:00), the spoilers seem to be slightly deployed during take off. What's the purpose of this? I've already seen this in other videos too. I've also read the answers to the question When can spoilers be used on airliners , but they seem to be related to slowing down the aircraft or for descending faster. But what is the point during take off, when it's supposed the pilots want to climb and go faster? <Q> Spoilers lower lift and increase drag on the side where they are deployed. <S> Symmetric spoiler deployment, therefore, is for slowing down. <S> Asymmetric deployment not only creates a (small) rolling moment, but primarily a yawing moment which helps to counteract the adverse yaw created by ailerons, especially at the high lift coefficient at takeoff and early climb. <S> Spoiler deployment increases pressure ahead of the spoiler due to the slowing of local flow ahead of the obstruction caused by the spoiler, and it creates a local flow separation at and behind the spoiler, which in turn lowers the local pressure. <S> Only the first effect lowers lift, but both create drag. <S> The main effect of a limited spoiler deflection, therefore, is to increase drag. <A> In this case, the flight spoilers are being used for roll control. <S> However spoilers are also used during take off in case of a cross wind. <S> In that case, the pilot may want to reduce some lift in the upwind wing and employ spoilers instead of/along with the ailerons. <S> A very small deflection in spoilers helps in increasing the drag over the wing and thus aid in roll control. <S> However, it is to be noted that the operation of spoilers during takeoff is very restricted in order to prevent flow separation. <S> In modern aircraft, the spoilers are used automatically with the ailerons. <S> So, when the pilot operates the yoke, he is not consciously deciding to employ them, but rather the control system does it for him. <A> Large jet aircraft have multi function spoilers. <S> They aide in turning the aircraft at low speed. <S> When the aircraft needs to be slowed down in the air and on landing all of the spoilers are activated. <A> I agree with Eric. <S> Many business jets gave a spoiler on feature which aids the pilot with roll control. <S> Spoilerons are typically activated with a flaps below a preset level and aileron movement. <S> Spoilerons usually rise up when the aileron on the side rises. <S> Thus, they aid in rolling the airplane. <S> Most likely on takeoff the pilots are correcting for winds and the spoileron system is active.
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Usually, the spoilers are used for roll control in concert with the ailerons, and are used during descent in order to slow down.
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Why do farmers register their fields as airports? (this seems to be primarily a US phenomenon) So in the vicinity of my parents' place (in a rural area in Indiana), there are several registered airports within several miles' radius. I remember when I was a kid, there were a few farmers in the area who liked to fly ultralights, and I wonder if some of these might be for that. And some of these are listed as having certain aircraft based there. For many of them, however, looking at their fields on Google Maps there is nothing to indicate that it is ever used for anything but growing crops--in some places there is no obstacle-free area even reasonably close to the listed runway dimensions. What's going on here? <Q> Just spoke to the farmer that owns Graham Farms Airport (SN72), a grass strip in a cornfield near the sprawling metropolis of Harris, Kansas. <S> Here it is on the sectional: And Google Earth: <S> He has a Cessna 182 there. <S> He told me he had it registered as an airport back in the 1970's, like Dave said, in case someone had an engine failure or something, atc could vector them there. <S> He also occasionally allows people from nearby Garnett Municipal Airport (K68) to practice grass strip landings there. <S> He got an unexpected benefit from having it registered with the FAA several years back when the power company was planning to run a high tension line right across his landing strip. <S> The power company refused to work with him on it <S> so he called the FAA. <S> Since it is officially an airport federal regulations forced them to run their line around it. <S> Aviation trumps power company profits! <A> Private airfields are not at all uncommon in the U.S., especially the rural parts (which is most of the U.S.) <S> Of the ones I've seen, though, the markings vary from very simple (old tires painted white placed along the edges) to non-existent. <S> Sometimes smaller ones can be hard to see on Google Maps, but, at least in my experience, you can usually find them if you look hard enough. <S> They're probably easier to spot in places with a lot of trees rather than in places where the land is predominately wide-open farmland. <S> Here's an example of what it looks like on a Sectional Chart and on Google Maps: One Grand Field on a Sectional Chart <S> One Grand Field (yes, it's literally a field) on Google Maps. <S> The long, narrow clearing in the trees is the grass runway. <S> To give an idea of just how common these things can be, take a look at this sectional chart clip: <S> There are no less than 12 private airports here within a roughly 25 nmi x 25 nmi area, despite having two nearby decent-sized public uncontrolled airfields (one of which is home to a large flight training school,) and a class D airport (with a busy-ish Class C visible in the Northwest corner of the clip.) <A> They may have crop-dusters that they fly in and out of their own fields like this one. <S> If the crops need dusting often and there is no airport nearby it may be cheaper and easier to fly from their own fields rather than spend the gas getting back and forth to a local field. <S> Here is a great little article that may give you some info. <S> As to why they have them on the chart the article states, So, if private airports are so private, why do their owners choose to have them depicted on sectional charts? <S> Again, the reasons vary, but most owners seem to be motivated by altruism. <S> Pilots want other pilots to have options when they fly, especially in the event of an emergency. <A> I have considered registering my grass strip, as it establishes prior use, and should there be zoning changes, it would be grandfathered. <S> Of course there are other ways of documenting that use, in the public record. <S> The power company story is also a good reason to have established prior use. <S> Addendum <S> : There is a downside for registration and publication on a map, and that is when someone decides to use your strip, and has a problem. <S> A local public use grass strip ran into that, and the owner did not have it properly insured as a public use airport. <S> The financial consequences are not clear yet, but the headache is not one I would invite.
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These are probably for crop dusting or because the owner also happens to be a private pilot and wants to keep their plane at home rather than paying the local FBO for hangar or tie-down rental. With wind turbines going up all over the place, it might provide some level of protection in terms of protection of an approach and departure path.
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Can training for an Instrument Rating be applied towards a commercial pilot certificate? Per 14 CFR 61.129 , a person who applies for a commercial pilot certificate for airplanes (both single and multiengine) must log at least ten hours of instrument training. Assuming a pilot obtains their instrument rating prior to training for their commercial pilot certificate, can the instrument time logged during training for an instrument rating be used to satisfy this requirement (assuming class of aircraft requirements are met)? <Q> Short answer: <S> yes, if the training has been logged with the remark that it meets the requirements of both 61.129 and 61.65. <S> This topic became confusing because of an FAA interpretation that says: <S> [...] are the requirements of 14 C.F.R. §61.129(c)(3)(i) <S> [commercial certificate] met by the student getting an instrument rating or training for an instrument rating? <S> The answer is no. <S> The training giving to satisfy the instrument training aeronautical experience of §61.129(c)(3)(i) may also be used to count towards the aeronautical experience of §61.65(e) <S> [instrument rating], but the opposite is not true. <S> The reason for this is that the training required under §61.65(e) is general, while the training under §61.129(c)(3)(i) lists very specific operations that must be accomplished to satisfy the requirements. <S> But that interpretation was surprising to many people because it implied that a commercial certificate requires additional instrument training, even if you already hold an instrument rating. <S> So AOPA requested a clarification (more information here ); you can read the whole thing, but the key statement from the FAA is this: We are merely clarifying the requirement that the applicant for a commercial pilot certificate provide evidence that they have met the requirements of §61.129. <S> There is not an exact equivalence between the training required for an instrument rating under §61.65 and the aeronautical experience requirements under §61.129. <S> Practically speaking (as the AOPA article explains) <S> that means that your CFII should explicitly log the training as covering both requirements: [AOPA] urges instrument pilot applicants and flight instructors to be sure that instrument training is clearly logged to indicate that the training given meets the requirements of 14 CFR 61.65 as well as those of 14 CFR 61.129. <S> That would avoid questions about the training’s <S> applicability should the pilot one day advance to training for a commercial pilot certificate. <A> Yes, your instrument training conducted during your IFR certificate will count towards a Commercial certificate. <S> This is based on the assumption that your flights have been logged by a current CFII. <S> There may be additional IFR related training that pertains to CPL such as meeting certain requirements as set out by the Practical Tests Standards booklet (PTS). <A> Yes, and the acid test is what the examiner (DPE) considers acceptable. <S> So as a CFI, what I do, if there is any doubt, is to create a summary of the requirements, and reference the date&time for the log entry, so that the DPE can establish that the requirements are satisfied. <S> CFI initial rides tend to get extreme scrutiny, and I use the same approach there, namely a checklist of the essential requirements for the rating, and the references to show where those requirements were satisfied. <S> The FAA inspectors love it. <S> The DPEs love it. <S> It makes everyone's job easier, and saves hassles. <S> So as a student, instrument or commercial, I would assemble your list of the rating requirements, and reference the log entries supporting those requirements. <S> Then have your CFI signoff on your worksheet after he reviews your data. <S> Present a copy to your DPE (yep, a copy for his records if he wishes). <S> It will help your checkride start on a good note. <S> After 37 years, I have never had a student sent home because they did not meet the rating experience requirements. <A> does do that. <S> Aeronautical experience is immediately transferable to an certificate you are seeking, provided it meets the guidelines for aeronautical experience listed in the FAR 61.129 for the specific certificate. <S> Much of the experience you log early on can be immediately transferable to other certificates, even in other categories or classes of aircraft. <S> For instance a person who holds a commercial certificate in an airplane single engine land could apply for a commercial certificate in a rotorcraft helicopter with as little as 50 hours total time in helos; the rest may be transferred from the applicants flight experience in other aircraft.
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You absolutely can and just about to everyone applying for a commercial certificate
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Can helicopters land in a poor visibility scenario? The Instrument Landing System and some others systems can provide to incoming aircraft guidance to the runway in poor visibility scenarios. With that in mind, I have these questions: Can helicopters fly in IMC? Is there any system that can help the pilot land, just like ILS? <Q> Can helicopters fly IFR? <S> Yes <S> Do they use ILS? <S> Yes . <S> The only tricky part of it is the need to be slow at the end of the glide slope. <S> This PPRuNe discussion is interesting. <A> Helicopters can fly IFR and they fly the same approaches airplanes do. <S> At certain airports there will be ILS (or other approach) procedures specific to helicopters. <S> The difference between the above procedure and the normal ILS 4L is that the copter approach has lower minimums, allowing the helicopters to land in lower visibility than airplanes. <S> At airports without specific approaches for helicopters, they would fly the same procedures airplanes do. <A> Not only do copters fly instrument approaches, they are allowed by regulation to halve both the ceiling and visibility minima for a non-Copter approach (but no less than 1200 and 1/4, or as otherwise restricted). <S> Also, copters often convert an instrument approach at the Missed Approach Point into a Special VFR clearance, which allows them to fly with 0 visibility (see and avoid) and clear of clouds. <S> For example, this approach into JFK terminated in the middle of NY Harbor at 500 feet, and shows course lines to the various Manhattan helipads : <A> I am flying AS 365 N3 Helicopter which is a twin engine machine and is approved for IFR operations. <S> The helicopter is fitted with ILS and can fly a normal ILS approach like fixed wing aircrafts of CAT B. <S> The ILS system fitted on this helicopter takes the helicopter upto 50' above Threshold Touch Down Point and then makes the helicopter fly parallel to runway at 50'. <S> The approach speed for CAT B aircrafts is 120 kts which can be reduced as the helicopter descends closer to the TTDP. <S> A fwd speed landing of speeds 70 kts and below can safely be executed to avoid a flare in poor visibility conditions. <S> However this is not a standard landing procedure. <S> In normal conditions, pilot must flare the helicopter to reduce speed and land with zero fwd speed. <S> In my opinion, a RVR of at least 100 meters is necessary to execute a safe approach with flare at the end for touch down.
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An IFR helicopter can use any of the navigation and landing aids available to any other aircraft.
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What was the purpose of the "tail prop" on the Ilyushin Il-62 and why was it necessary? I read somewhere that the Ilyushin Il-62 had a "tail prop". What was this device and why was it needed on this aircraft? <Q> Are you asking about the rear support wheel? <S> It is for supporting the aircraft and avoiding tilt on the ground. <S> Image from wikimedia commons. <S> Autor: <S> M Radzi Desa <S> As the aircraft had four engines in the aft, the cg would've been aft too; so they added a tail prop to prevent tilt on ground. <S> Interestingly, this doesn't seen to be unique for Il-62. <S> Another aircraft with rear mounted engine, Sud Aviation Caravelle, has something similar to this. <S> Image from wikimedia commons. <S> Author: <S> Eduard Marmet <A> The 'tail prop' is more accurately described as a tail support. <S> I remember seeing these on Il-62s at Heathrow in the 70s. <S> They were deployed as the aircraft arrived at the gate, and retracted just before pushback. <S> Anecdotally, the aircraft had a propensity to tilt backwards and strike the tail on the ground during loading and unloading operations as the CG moved. <S> The tail support eliminated this possibility. <A> They're called "tail stands" for planes such as the Cessna Caravan. <S> During loading and unloading the CG can be tail-heavy enough that the aircraft would otherwise fall back on its tail. <A> I found an Aircraft Operations Manual for IL-62 and IL-62 M of former GDR carrier Interflug <S> (in German language) <S> : <S> http://www.interflug.biz/IL-62%20Flugbetriebsdokumentationen.htm <S> http://www.interflug.biz/Flugzeuge/IL-62/Handbuecher/FZH_Il62.pdf <S> According to this manual, the "tail prop" supports several functions. <S> Supporting parked airplane while centre of gravity isn't controlled: The manual requires to extend the tail prop when parking, before opening any door. <S> Tail prop shall be retracted only after closing all doors and only when centre of gravity is within limits (4.2.5. <S> No. 2., tab. <S> 4.2.5./1). <S> Taxi with extended tail prop is allowed, speed limit is 25 km/h. <S> (4.2.2. <S> No. 1) <S> When towing an empty plane the tail prop must be extended, speed limit is 15 km/h. <S> (4.2.2. <S> No. 2) <S> Moving the plane backward by utilizing reverse thrust: Tail prop must be extended, speed limit is "walking pace". <S> (4.2.2. <S> No. 4) <S> U-turn on a narrow runway (min. 45 m) by utilizing reverse thrust: <S> Tail prop must be partly extended. <S> (4.2.2. <S> No. <S> 5, fig. <S> 4.2.2./2) <S> The tail prop features two self-steering wheels and a suspension system. <S> No brakes, no active steering. <S> It is extended and retracted by an electric motor, backed by a hand crank. <S> (4.1.8. <S> No. <S> 1.3, fig. <S> 4.1.8./5) <S> Probably, the tail prop is also designed to provide some protection in case of a tail strike (since it's wheels partly remain outside fuselage), but this function isn't mentioned in the manual. <S> Btw., this plane features a 3700 ℓ water tank (just behind the front landing gear bay), for adjusting centre of gravity in some low-load situations. <S> (4.1.24., 4.3.2. <S> No. <S> 2.5, fig. <S> 4.1.2/2 item 5) <A> <A> Improvised tail-props were a feature of early, tricycle landing gear, military aircraft. <S> Grumman's F7F Tigercat, certainly. <S> There are photos with 55 gallon drums + assorted odds and ends as props, in place, and also photos of unsupported planes sitting with nose-wheels off the ground... <S> At that point in Grumman's history, nobody would have expected resting the tail on the ground would do any damage to the airplane... <A> This is a very interesting take on CG vs Clift, in this case while the aircraft is not moving!The wheels are holding the aircraft up. <S> It would take a relatively small amount of force to tip the plane onto its tail while loading or unloading. <S> A little like a table with 3 legs instead of 4. <S> While taking off, the aircraft has to be able to rotate, which means the main gear need to be only slightly aft of the CG when fueled and loaded for flight. <S> On the ground this creates the potential for it to go "tail dragger" if cargo is removed from the front or added to the back. <S> Moving people from front to back was actually used in airships to help trim CG. <S> But it is very, very important to realize this is not done "because engines are heavy" and the designed CG is somehow unsafely aft. <S> Jet engines are actually (lb weight per lb thrust) much lighter than their piston counterparts. <S> Aircraft with swept wings who must, by necessity, mount the landing gear closer to the fuselage (or in the fuselage) would have a greater tendency for "ground Clift" issues. <S> The B52 designers solved this by mounting the wing at a higher AOA than the fuselage and taking off WITHOUT rotating, relying only on speed to lift the aircraft off. <S> This also fits well in pilot training not to "pull up" a large aircraft, as shear mass would make recovery of precious airspeed difficult, even with lots of excessthrust available. <S> The "tail pogo" is strictly a safety precaution while passengers, cargo, and fuel are being loaded or unloaded on the ground, <A> Many smaller turboprops and piston twins use 'tail props' or 'pogo-sticks' as they are known here. <S> Certainly Twin Otters, BN Islander and Trislanders use them. <S> Can't comment on the Caravan. <S> The last one I was son a few weeks ago had floats ;-) <A> Robert DiGiovanni's response is correct. <S> While the empty IL62 is a bit tail heavy, once the airplane is laoded with passengers/bags and cargo the CG will be moved forward. <S> Look at how much longer the fwd fuselage is compared to the aft section, its around 4 times longer! <S> The MD11 has a similar proportion where the forward fuselage is much longer than the front. <S> I've done the load-sheet for MD11 freighters and while the empty CG is VERY tail heavy, with a full load the CG is usually at the fwd limit.
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It's a tail stand -- it prevents the airplane from tipping up and back onto its tailfeathers in a most embarrassing fashion, even if you have to load it back to front or unload it front to back (image from Aerospaceweb's question on landing gear ):
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Is there a difference between "aerobatic" and "acrobatic" flight? I hear and read both the terms "aerobatic" and "acrobatic" used to describe the more extreme maneuvers such as spins, rolls, loops and more. My questions is about the terms themselves. It seems that they are interchangeable, but is one actually more correct to use than the other? Why do we have these two very similar words in the aviation vernacular that seem to mean the same thing? <Q> Acrobatic is being incorrectly used, although it is slightly more complicated than that. <S> "Aerobatic" refers specifically to flight, and "acrobatic" refers specifically to feats of the human body, so referring to an aircraft as performing acrobatics is wrong. <S> That said, the word "aerobatic" is derived from "aero-acrobatics" and sounds nearly identical, so it's an understandable and relatively common error. <A> The Oxford English Dictionary's etymology for "aerobatics" is "After acrobatics " and defines it as: <S> Feats of expert aviation, performed esp. <S> for display. <S> Hence aeroˈbatic <S> a . <S> ; ˈaerobat , one who performs aerobatics; hence as v. intr ., to perform aerobatics; also trans . <S> So it's a new word pertaining to aviation based on one for (also Oxford English Dictionary): <S> A rope-dancer; a performer of daring gymnastic feats and evolutions; a tumbler. <S> lit . <S> and fig . <S> Edit: Notice the fig. <S> at the end of the definition (which is an abbreviation for figuratively ). <S> So "acrobatic" can correctly be used to describe a person, cat, airplane , etc ... performing "acrobatics". <A> Some of the other answers seem to claim that acrobatics would be incorrect when used to describe aerobatics, however when you look up various definitions you will find out that acrobatics : difficult and dangerous acts done by an acrobat; also : difficult or dangerous acts, movements, etc., done by another kind of performer <S> Source: http://www.merriam-webster.com/dictionary/acrobatics <S> acrobatics in the air flowing from the following etymology: <S> aer- <S> + acrobatics = <S> > aerobatics Source: http://www.merriam-webster.com/dictionary/aerobatics <S> So in conclusion it's fine to use either term, especially when it's already clear that the context is about aviation. <S> In an undefined context it might however be useful to have two words, for example <S> I went to an aerobatics display and <S> I went to an acrobatics display <S> of course hold two very different meanings. <S> Point is just: If you can pick, pick aerobatics, but don't go correcting people who aren't saying anything wrong. <A> In my opinion, acrobatic is more related to a person, "One who is skilled in feats of balance and agility in gymnastics". <S> However, aerobatic relates to maneuvers on the air. <A> “Aerobatics” is only a portmanteau of “Aeronatical Acrobatics” either is fine and anyone who corrects you is a word snob.
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So, acrobatics is just the generic word, whilst aerobatics is the more specific word describing a very specific form of acrobatics:
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Why are magnetized materials dangerous goods? I was reading about Dangerous Goods , and came across the fact that magnetized materials are classified as Dangerous Goods (item 12 in the linked page). We all see magnets every day, and they seem harmless. Why are magnets dangerous to airplanes and require more careful handling? <Q> 98% percent of magnets - the everyday ones - are completely harmless. <S> I believe the concern is with super-strong rare-earth magnets , where they can be problematic. <S> Aside from Simon's valid point on interference to compasses: Getting stuck to things, such as other bags or the infrastructure itself, in the baggage system. <S> Attract themselves to other packages and content, possibly damaging these. <S> Think of hard drives and electronics. <S> Being a nuisance and safety concern should somebody decide to open it, such as customs or security. <S> You can get your hand crushed in the process if you open the box and the thing springs out. <S> Be aware they do not appear to be banned - just regulated in that they have to be properly labelled and packaged for safe transport. <S> More curiously in that list are 'First Aid Kits' and 'Seatbelt Pretensioners'. <A> Because the aircraft has a standby compass in the cockpit which is a normal magnetic compass. <S> This compass must be fitted and must be working in case of extreme instrument failure. <S> There are three things which standby instruments must provide; height, speed and heading (the compass). <S> Magnetic cargo can interfere with this compass and therefore, is treated as dangerous cargo. <S> Whilst the risk is low, the aviation industry leans on the side of safety, and we can all see the benefits of that. <S> This report will tell you what you want to know. <A> I use neodymium magnets in my work as a research scientist and I regularly carry them aboard aircraft in packaging. <S> We are not talking fridge magnets here, these are serious high-field permanent magnets. <S> If two of them get properly stuck together they cannot be separated again easily. <S> (The fields are far too strong to be pulled apart by hand <S> and you can't use any metal tools for obvious reasons. <S> One trick is to use a heavy, non-ferrous plastic-coated mallet to smash one off the other at the edge of a table, but even then it's usually half the day wasted.) <S> The problem is that the strength of the force between two such magnets is not intuitively understood by people unfamiliar with them: for example, your typical customs or security inspector. <S> There might be almost no noticeable force between two magnets when they are some distance apart in the packing box but once they get within 5 to 10 centimetres they will suddenly be attracted together and anything in the way (flaps of skin, fingers) will simply be crushed flat under the force. <S> Or if nothing slows the magnets down as they come together, the force of the impact can chip the surface of the metallic protective layer, spraying shrapnel and metal fragments everywhere which poses a risk in particular to eyes. <S> (The alloys used in constructing these magnets are extremely brittle.) <S> If the magnets get stuck to other large metal objects it can be a pain to separate them. <S> They also induce weak magnetism in metals you normally expect to be non-magnetic. <S> Finally if they get wiped across anything like a credit card or ID badge that's usually the end of it (not always actually, it's a bit random). <S> So anything like this needs to be identified so that they can be treated with care if someone does want to open my luggage to fish around inside it.
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The magnets are not extremely dangerous, getting small bones broken or metal fragments in the eye is the worse case scenario on my risk assessment, but they are not toys and there is a risk to those untrained in handling them.
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What are the advantages and disadvantages of have the wing positioned further aft on an airplane? I've noticed that there is some variation in the location of the wing on airliners: The Boeing 737 has its wing mounted near the midpoint of the fuselage: while other aircraft like the CRJ or the Airbus concept plane shown below have the wing mounted further aft. What are the advantages or disadvantages to these wing locations, and why might a designer pick one over the other. <Q> The overall centre of lift must be coincident (in the horizontal plane) with the centre of gravity, otherwise the plane would tip over forward or backward. <S> So the wing is mounted further aft if the centre of gravity is further aft. <S> Now the cargo will always have its centre of gravity near the centre of the fuselage. <S> So if the empty aircraft has aft centre of gravity, loading it will cause larger change of the CG position and for this it needs larger horizontal stabilizer so it can provide enough balancing force. <A> The wings produce not only lift, but also a pitching moment. <S> Usually, it is destabilizing in the sense that it causes nose up of the aircraft as the aerodynamic center is in front of the cg (which causes further nose up and so on). <S> This moment is then counteracted by the tail. <S> Pic: adg.stanford.edu. <S> As we move the wing to the aft, the stability increases and once the wing is behind the c.g, the aircraft becomes stable. <S> Pic: <S> adg.stanford.edu <S> Although this is stable, the configuration causes a nose down moment when lift is increased. <S> However, we also want that the aircraft be trimmed (i.e. at moment equilibrium at the desired c.g). <S> With single wing, this is not easy with a reasonable static margin. <S> Another thing is that as the wing is moved aft, the c.g also shifts aft. <S> It is possible to have wings in the rear. <S> In that case, it becomes necessary to add a canard for controlling at he aircraft. <S> A good example would be the Gyroflung Speed Canard. <S> As already noted, the aircraft has a canard for control. <S> The location of the engine and wing are related. <S> As the engines are moved aft, the c.g. shifts in that direction and the wing is moved aft to reduce the tail surface needed. <A> Rear placement of the wing was heavily influenced in design philosophy by the effort to develop planforms for supersonic flight, but goes back to the earliest days of powered flight. <S> It is important to remember that in the bewildering variety of aircraft shapes and sizes, the physics for stable and safe flight remain the same. <S> In subsonic flight rear wing placement offers the advantage of rear engine/propeller placement by which improves efficiency. <S> However, this is offset by the need for much larger vertical and horizontal stabilizers, as stability torque arms are now much shorter. <S> Also of concern is keeping the pitch nuetral point behind the CG, which assists pitching nose down in a sink. <S> These issues plagued the Army Air Force Ascender design and was only remedied by adding more area aft of CG. <S> One silver lining is that this is not a problem with canard/delta designs, but deltas do not produce lift as efficiently as straight wings. <S> Careful checking shows that amazing speed and fuel consumption benefits comes more from weight savings of lighter composites than from futuristic swept designs,though they are beautiful. <S> So for recreational aircraft the tried and true Piper Cub type design is one of the best one can pick.
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Since most planes have a large wing that contributes most of the lift and a small horizontal stabilizer that only contributes a little bit, the main wing needs to be close to the centre of gravity.
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Could airliners' wings be thinner if no fuel were stored in them? I ask this question because wings are pretty thin overall, but I am curious if you could make them more thin. <Q> No. <S> The wing thickness is primarily dictated by structural demands. <S> It has to provide an aerodynamic fairing for the wing spar. <S> Making it thinner would drive up the mass of the structure inside. <S> To simplify things, imagine the wing spar as an I-beam. <S> It has two flanges which carry tension and compression loads, and a web between the flanges to transmit shear loads. <S> The bending moment carried by the spar is the product of the forces in the flanges and the distance between them. <S> If you reduce the distance, the forces need to increase to keep the bending moment constant. <S> Bigger forces will result in bigger flanges to keep the stresses in the material below the yield stress. <S> Limiting the thickness is the desire to fly at a certain Mach number . <S> A moving wing needs to push the air ahead of it aside, and thicker wings need to do more pushing. <S> This results in a higher acceleration of the flow around the wing, and thicker wings have a lower critical Mach number <S> (the flight Mach number when local flow reaches Mach 1). <S> This drag penalty is especially severe in supersonic flight. <S> The plot below (taken from this website) shows that an airfoil thickness of 12% gives the best results, which helps to keep the wing area low. <S> A thicker wing also makes it easier to integrate complex high-lift devices, which again helps to reduce wing area. <S> The resulting wing thickness is always a compromise, and the fuel volume is only the result of that compromise. <S> If a wing needs to store more fuel, the designers will choose a lower aspect ratio , but will leave the relative thickness unchanged. <S> If less fuel is required, the tanks will become smaller, and again the thickness will not change. <A> Airplane wings are designed purely from aerodynamic and structural considerations. <S> Supersonic fighters often have much thinner wings (and store fuel in the fuselage) because those are the requirements of supersonic flight. <S> For subsonic (and transonic, which most modern airliners and business jets are -- over some parts of the wing the airflow is actually supersonic) flight, thick wings are fine, are structurally much better, and provide space for fuel tanks and the wheels. <A> Possibly, but having no fuel in the wing would likely be an effect of making wings thinner, rather than a driving cause. <S> In the past, thin airfoil theory ruled the day, and designers used external trusses to support two lifting surfaces in a biplane configuration. <S> Check out the De Havilland Dragon , which used the RAF 15 airfoil section (max t/c of 6.5%), as an example. <S> Compare this to the Boeing 247 , which was introduced one month later <S> (May vs. April 1933) and also carried ten passengers, but used a single cantilever wing, without external supports. <S> Its wing section, the Boeing 106 (max t/c of 13.5%), was thick enough to contain an internal support structure. <S> The main benefit of having all your structural members contained in the wing is the reduced drag. <S> You get some other benefits as well, like delayed stall due to the rounded leading edge, and room to store your fuel due to the higher enclosed volume. <S> It's unlikely that any serious airliner design is going to return to a biplane configuration. <S> Today, thanks to the wealth of materials and design tools the engineers have, the wing thickness seems to be around 10% based on glancing at a few Airbus/Boeing offerings. <S> Usually, a modern design will change the airfoil profile from root to tip, so it will be higher in some places and lower in others. <S> It's possible that if these techniques were applied to biplane designs, we could come up with some really thin wings, but the airplane would have high drag and likely wouldn't sell. <S> That said, some concepts arrange the wings in ways that might let you get away with this. <S> In particular, Lockheed Martin has proposed a box-wing concept (for which I couldn't find the name) and Boeing has studied a design with braced wings called Subsonic Ultra Green Aircraft Research (SUGAR). <S> If one of these designs ends up reducing the amount of stiffness needed in the wing spar, the designers would likely reduce the spar (and thus wing) thickness to save weight. <S> Depending on how much thickness they shave off, it might no longer be worthwhile to store fuel in the wing.
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Thicker wings also help with creating higher maximum lift coefficients, up to a point.
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Can excessive G-force break or dislocate bones during pilot maneuvers? Was wondering if the pilot would faint, could g-force be enough to maybe break the neck bone with the head and weight of a helmet being pulled downwards. Another relay to this is the effects on the inside of the body, more specifically, the brain. Like a boxer, after taking a few too many knockouts. Is there a limit, or an event horizon to permanent brain damage and bone structure deterioration concerning g-force and pilots in aircraft maneuvers? <Q> Can excessive G-force break or dislocate bones during pilot maneuvers? <S> Yes. <S> Even if the pilot remains conscious. <S> For example see http://medind.nic.in/iab/t00/i2/iabt00i2p1o.pdf which describes compression fractures suffered by pilots. <A> However, several cases exist where pilots have awoke in a supersonic, or near supersonic, dive and sustained massive flail injuries after ejecting. <S> Its also important to note that simply jumping in the air will exert your body to instantaneous G-forces well above what you'd experience in a fighter aircraft. <S> If such G-forces were capable of causing injury then you'd hardly be able to get out of bed without causing grievous injury. <S> The danger to high G-forces in the vertical axis is that the blood is pulled from the brain to the lower extremities causing a form of hypoxia commonly referred to as GLOC, or G Induced Loss of Consciousness. <A> Yes, there have certainly been cases in which fighter pilots break bones while performing high-G turns. <S> Unfortunately, the bone most susceptible to injury is the spine because that is the one of the few structures supporting real weight other than itself. <S> ... <S> pilots of high-performance aircraft frequently sustained cervical spine injuries due to their exposure to high gravitational forces (5), these investigators measured accelerations about the head of an F-16 fighter pilot during simulated air combat maneuvers. <S> With the aid of a spine model, they calculated the forces on the lower cervical spine and noted that the forces were of the same order of magnitude as failure loads of cervical vertebrae and estimations of maximum cervical spine muscle forces. <S> In one miraculous instance, a USAF pilot was able to land after pulling a 9G turn and breaking his back. <S> I currently cannot find a source for this <S> but I remember listening to my dad's friends (USN) talk about visiting the pilot. <S> I believe he was disabled in a leg or maybe both <S> but he did not fly again. <S> Less severe maneuvering will not break bones very easily, but they can produce neck injuries . <S> There are many safety features built into aircraft that can maneuver into such high-G turns, however. <S> The earliest example of this is the G-suit, which pushes blood that pools in the lower half of the body back up to the brain using air pressure lines and sacs. <S> In addition, some aircraft set artificial limits on how tight a pilot can turn to prevent pilot injury and airframe stress <S> (The F-14 could survive much more than 6-7Gs but that limit was set on the controls to reduce wing stress and failure). <S> More recently aircraft have adopted digital systems that will right an aircraft if the pilot fails to respond to an alarm within a certain period of time. <S> If a pilot is in blackout or prolonged greyout, the aircraft ignores pilot input and tries to fly straight and level. <S> This is mainly to prevent unconscious crashes into terrain, but it also prevents pilots from entering tighter and tighter turns that they cannot leave.
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No, the moment consciousness is lost, the body will go limp and the hands will release the controls and the aircraft will naturally seek 1g flight. For what it's worth, skeletal injuries due to G forces are so rare that they aren't even briefed during training.
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Could older airplanes be retrofitted with engines with chevrons? The 787 uses a variety of sound reducing mechanism including engines with characteristic chevrons: (Source wikimedia commons) Would it be possible for older airplanes to also have this type of quieter engine retrofitted? I'm assuming the engines would have to be recertified of course. But do the chevrons implicate a particular type of wing or airframe that requires them to be designed in from the beginning? <Q> However, the engine does need to be designed around having the chevrons, since they affect the performance as well as noise. <S> And the engine design certainly can affect the design of the wing. <S> In reality, chevrons are more likely to be incorporated in an engine design from the start rather than retrofitted later. <S> And a new engine design will probably be for a new airplane design. <S> This could be a totally new plane like the 787. <S> But it could also be a new derivative, like the 747-8 or the 737 MAX. <S> So while chevrons can be added to the engines on an existing aircraft model, it's much more likely that the aircraft model will be upgraded in other ways as well to accommodate the new engines. <S> Adding chevrons is likely to be part of a design change large enough to justify changes to the aircraft as well. <S> However, these changes are not really specific to the engine having chevrons. <S> Changes to the wing and airframe will be due to the inclusion of a new engine, not just the addition of chevrons. <A> Yes. <S> This kind of engine design is independent of the wing and airframe and can be fitted on compatible aircrafts. <S> For example, General Electric GEnx-1B64 , an engine with chevrons is fitted on Boeing 747-8, a variant of Boeing 747. <S> In general, the engines (especially civil airliner engines) are developed with compatibility in mind to reduce costs and increase commonality. <A> Yes. <S> The parts shown with the noise reducing 'chevrons' are part of an assembly called the engine cowling, which is usually manufactured by a separate manufacturer than the engine. <S> It is reasonable to assume new engine cowlings could be designed as part of an STC upgrade. <S> NORDAM and UTC Aerospace Systems (Goodrich) are examples of engine cowling manufacturers
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The chevrons do not implicate a particular type of wing or airframe.
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How long would a cruising aircraft take to crash if everyone spontaneously vanished? I recently saw a movie in which what appeared to be a Lockheed C-130 Hercules was suddenly without occupants. They did not move or exit the craft, they simply vanished. I assume that the craft remained pressurised, and no modifications to controls were made. I assume that any auto-pilot-like features remained either on or off as they were at the time, unless they have some kind of system to automatically engage in certain situations. At the time of the incident, the aircraft appeared to be cruising. I am wondering how long it would take for a cruising aircraft take to crash if everyone spontaneously vanished? <Q> There is a far more important question (and the real deciding factor) <S> How much fuel is on board? <S> This has happened on occasion before. <S> The Helios Airways Flight 522 is about as close as you can get to this hypothetical situation in real life. <S> The plane may travel farther (since its lighter) but it will go until its out of gas. <S> The same thing applies to smaller GA planes as well. <S> This is all of course assuming that the plane is not intercepted before running out of gas. <S> Helios 522 was intercepted by F-16's before it crashed and they visually established that the crew was incapacitated (although a flight attendant tried to save the plane). <S> I don't know what the procedure is for interceptions like this but if the plane were headed for a highly populated area they may not let it run out of fuel. <A> If the autopilot was on, it's a question of how much fuel is on board as related in another answer (unless high ground was in the way). <S> If the autopilot is off, even if in perfect trim, the aeroplane will usually gradually drop a wing (this process will start within 15-30 seconds) and develop an ever steepening spiral dive and crash at high speed into the ground. <S> Sometimes something different has happened, perhaps if a dead pilot has his hands on the controls, but in most cases there is insufficient stability for it to remain wings level for long without pilot input. <S> I'm thinking of an example in the States where an airliner's wing sliced through the cabin of a light aircraft and cut the three occupants into two. <S> That aircraft managed to land itself intact in a school playing field <S> I think it was, with blood covering the fuselage and wings, but no fuselage top and no visible occupants. <S> Also, in a small plane the trim might be affected by people disappearing (due to a change in CG) <S> but I think the usual result would be to drop a wing as related. <S> I am not aware of any systems that would turn an autopilot on automatically if it was off. <S> Finally, many light aircraft only have wing leveller autopilots, so in this case, even if it was out of trim on the elevators, it would take longer (perhaps much longer) to crash <S> , it just might fly long enough to run out of fuel, assuming no mountains were in the way. <A> I remember reading about another one--GA aircraft, a drug runner, the pilot jumped once he was intercepted. <S> The plane continued on until it ran out of fuel. <S> Someone involved (it's been too long since I read about it to remember who) was trying to get permission to shoot it down as it was heading for a city. <S> It was not shot down, it flew over the city and went down at sea when the fuel ran out.
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If left unattended a plane will fly until it runs out of gas quite literally, the more gas in the tanks the longer you have.
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Why are many military fighter aircraft designed to fly supersonic? It is my understanding that these aircraft rarely fly at supersonic speeds anyway—the ordnance they carry, the increased fuel burn (even with supercruise), and the increased chance of detection make supersonic flight either hard to maintain or seem unnecessary. In addition, it would seem more beneficial to perform subsonic evasive maneuvers against an incoming missile than to try to outrun it (many air-to-air missiles fly at Mach 3 or higher). Finally, the subsonic Sea Harrier even downed a supersonic-capable Mirage III and many supersonic-capable IAI Daggers to no losses during the Falklands War. Though this can be attributed to the superior pilot training and offensive technology of the Harriers, how come many other aircraft were/are produced with a supersonic requirement? <Q> One reason is interception (with interceptor, not missiles). <S> Defence is probably more important. <S> Defence with fighters is still important for three reasons: <S> There are relatively effective counter-measures against surface-to-air missiles. <S> A fighter pilot can adjust the strategy to the counter-measures encountered, missile can't. <S> In peace or limited conflict situations it is often not known whether a suspicious target is hostile at all and the only way to identify it is to have a fighter fly to it and have the pilot identify it with their eyes. <S> Fighter can also do other things than use lethal force. <S> In peace time you generally don't want to shot down an intruding military aircraft of another country straight away. <S> Fighter can chase it away from your territory or can try to arrest it (force it to land on your own airbase). <S> And fighters are also used to identify and possibly navigate to safety civil aircraft that lost radio contact. <S> So when a potentially hostile aircraft is detected entering your territory, fighters are sent to intercept it and help it, arrest it or shot it down depending on what it turns out to be. <S> If the fighters are slower than the intruder, they may not be able to intercept it at all (they don't usually know where it is flying so they can't wait for it). <S> In this case the interceptors take off without external fuel tanks (as they won't be flying very far) and with only relatively small air-to-air missiles, so they can fly fast. <S> Conversely if you try to penetrate the enemy territory, flying faster limits the number of fighters that can intercept you. <S> However in this case it is more useful to rely on stealth or flying low to evade detection, so attack aircraft often are either not supersonic or have lower maximum speed. <A> The answer, speed is life . <S> While that may seem abbreviated, superior speed gives fighter aircraft far more options to attrite the enemy or to survive another day. <S> The following is a limited subset of general reasons why having superior speed would be an advantage, but unfortunately, specifics are beyond the scope of this discussion. <S> Pure Speed <S> Offensively, speed is necessary to consummate an intercept, although, it often does not require superior speed, as geometry is a far more useful intercept tool. <S> However, offensively, speed becomes more useful when chasing down a fleeing aircraft, or when flowing to multiple targets. <S> Defensively, speed can help targeted aircraft bug out, as well as simply increase time to kill so that other friendlies can swoop in and save the day. <S> You burn far more gas exploding in a fireball than you do dumping fuel into the afterburners! <S> The Power <S> However, the power to go fast is often just as important, if not more important that the ability to go fast. <S> Those afterburning, fuel guzzling, engines allow fighters to have enormous rates of climbs, and to sustain airspeed through much more dynamic maneuvers than slower, less powerful, aircraft. <S> Thrust to weight ratio is paramount in a turn rate fight, and, in BFM, the ability to suddenly add a fist full of knots may be the deciding factor between missile giver and missile taker. <A> To add to other answers, aircraft speed and altitude greatly contributes to missile kinetic performance. <S> The range difference between a missile fired at mach 1.6 at 35k feet versus the same missile fired at mach 0.5 at 10k feet is (tactically) massive. <A> Another Addition to the previous answers would be:Most maneuvrability/performance theories are based on the Energy of the aircraft. <S> So the higher and faster you fly, the more Energy you have for combat. <S> You can convert this speed in altitude for example. <S> This was especially true for military aircraft in WW2.For example: https://en.wikipedia.org/wiki/Energy%E2%80%93maneuverability_theory
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Also faster fighters will generally climb faster while covering greater distance which is important for interception from ground scramble. The faster they are, the larger area they can defend.
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Why do some 2 seat fighters have side by side seating, while others have the pilots inline with each other? In some multi seat fighters, like the F-111 Aardvark the pilots sit next to each other, like so: While in other multi seat fighters (most of them it seems) the pilots sit with one in front of the other, like this F-15E : Why do some fighters have the pilots in a line like that? Is there an aerodynamic or performance advantage that comes with having them in a line? Or maybe it's so they can have a bubble canopy, which perhaps affords a better view? It seems it would be easier to work together when they are side by side. So why do some multi seat fighters have side by side seating, and others are in a line? <Q> The tandem arrangement (one behind the other) is used on aircraft that have single seat variants. <S> The F-15, F-16, and F/A-18 are all primarily single seat aircraft. <S> It's much easier to stretch the nose out a bit to add a second position than to make it wider. <S> This arrangement is also more aerodynamic, requiring less frontal area. <S> Fighter aircraft designed for a crew of two will often choose the tandem arrangement for aerodynamics. <S> If both seats need forward visibility, there are compromises available . <S> Some aircraft like the F-15E can be flown from both seats even though there is less visibility from the back. <S> It's possible to have a bubble canopy in side-by-side configuration (this is particularly seen in aircraft kits ), though it will create more drag than a tandem canopy. <S> Having the crew sit next to each other can be helpful for crew interaction and sharing instrumentation. <S> The F-111 is one such special case : <S> The USAF wanted a tandem-seat aircraft for low-level penetration ground-attack, while the Navy wanted a shorter, high altitude interceptor with side-by-side seating to allow the pilot and RIO to share the radar display. <S> This may have also been easier to design the escape capsule. <S> Of course the Navy changed their mind and went with the F-14 instead for better maneuverability. <A> This is why most of the high performance fighters have tandem seating arrangement. <S> " Sukhoi Su-30LL demonstrator flying along the runway at Zhangjiajie Hehua Airport less than 1 metre off the ground " by Xu Zheng - http://www.airliners.net/photo/Russia---Air/Sukhoi-Su-30LL/1025605/L/ . <S> Licensed under CC BY-SA 4.0 via Commons . <S> Another advantage in tandem seating arrangement is that conversion from single to double seat (and vice-versa) variant is relatively easy and requires minimal design change compared to the side by side configuration. <S> " Su-27 05 " by Unknown - DefenseImagery.mil ID DD-ST-88-09314. <S> Licensed under Public Domain via Commons . <S> The main advantage of the side-by-side seating arrangement is that it allows for better work sharing between the crew and reduces the need for duplication of flight instruments. <S> The crew comfort is also (comparatively) better for long range flights, reducing fatigue. <S> " Sukhoi Su-34 at the MAKS-2013 (03) " by Doomych <S> - Own work. <S> Licensed under Public Domain via Commons . <S> Also, the customers (Air Force/Navy) may also decide which arrangement to use. <S> For example, the initial postwar British trainers used side by side seating as RAF preferred this arrangement. <S> In case of B-52, the prototypes (and even the initial production aircraft) had a tandem seating arrangement. <S> " YB-52sideview " by Original uploader was Sf46 at en.wikipediaLater version(s) were uploaded by Nobunaga24 at en.wikipedia.(Original text: U.S. Air Force) <S> - Transferred from en.wikipedia; Transfer was stated to be made by User: <S> Nobunaga24 <S> .(Original <S> text: <S> USAF Museum Website). <S> Licensed under Public Domain via Commons . <S> However, Gen. LeMay decided that a aside by side arrangement utilizes the copilot better and improved instrumentation and the arrangement was changed from tandem to side by side. <S> " Boeing B-52D-40-BW (SN 56-0695) and GAM-72 Quail decoy missile and trailer 061127-F-1234S-010 <S> " by US Goverment. <S> Licensed under Public Domain via Commons . <A> One other point not mentioned here is that the F-111 was designed during the time frame that the Air Force and its contractors were experimenting with the lifting body principle. <S> At that time, a lot of work was going into widening the fuselage and making it act like a wing. <S> The main benefit the Air Force was looking for was that additional lift equals additional weapon payload. <S> The contractors also explored that a lift-creating fuselage reduced structural stress on the wings and increased fuel capacity (increasing range).
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The main reason for having tandem seating in fighter aircrafts is that it offers better performance compared to the side by side version.
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When was the first rudder on an aircraft used? I have seen pictures of World War I-era airplanes that have rudders much smaller than today. When did the first rudder come out? <Q> Planes as early as the wright glider (1902) had a rudder, it appears from pictures that the 1900 and 1901 variants did not have rudders but its hard to tell from the photos. <S> Depending on your definition if you are talking about powered flight <S> the Wright Flyer (1903) had 2 rudders much like its earlier glider predecessor. <S> So that may take the cake if you have consider it a true rudder. <S> Side Note: <S> Patented in 1930 <S> the V-Tail design could be argued as the first design that did not (as far as I know) employ a rudder. <S> The earlier Beechcraft Bonanza's are the most common plane of that design in commercial production. <S> There is quite a bit of debate as to the safety of ruddervators and the general theme seems to be that they are not perfect and do require some care to fly properly. <A> Rudder itself was used before the Wright. <S> It was just the idea of a rudder on a boat. <S> Otto Lilienthal flew a glider which had a tail with a modern look in 1894: <S> Source <S> Actually the whole airplane has a modern look, like the cambered wing <S> , Lilienthal was an aerodynamicist, he invented the polar curve . <S> Note <S> : The rudder is not meant to control the aircraft direction --this is done by rolling the wing,-- but to counteract the adverse yaw which develops when the wing is rolled (more drag on the upper half of the wing). <S> This effect can be obtained even with a fixed rudder (the turn will not be coordinated , but this tends to prevent a spiral dive). <S> Adverse yaw in a roll <S> ( source , more in this answer ) <S> So the size of the rudder is proportional to this force, which is smaller on small wings. <A> 1785 ,when Jean-Pierre Blanchard crossed the English Channel in a balloon equipped with flapping wings for propulsion and a birdlike tail for steering <S> according to pages 26-27 of L. Winter and G. Denger's "Minute Epics of Flight," published 1933. <S> We don't have photos, but we do have a woodcut . <A> The Wright Flyer had two rudders. <S> That flew in 1903. <S> Some of the wright bros. <S> earlier gliders also had rudders ... <S> To test the technology and to determine the optimum size. <A> The 1785 balloon answer is interesting. <S> However, we might note that flapping wings would be extremely ineffective at propelling a balloon, and a rudder will have no significant effect on a free (unpropelled) balloon. <S> With that in mind, we might conclude that George Cayley was the first to suggest the use of a rudder in a practical way on an aircraft. <S> In 1799 George Cayley inscribed a coin with a picture of a design for a glider that appears to include a movable rudder. <S> By 1804 he had built a flying model glider that included a cruciform tail that could be adjusted on the ground both in the pitch and yaw dimensions. <S> By 1848 he had created an illustration of a full-scale glider that included a similar tail that could be adjusted in flight. <S> He tested a full-scale glider built along these lines in 1849, and a larger similar glider in 1853. <S> Here is one link that covers Cayley's work: http://www.flyingmachines.org/cayl.html <S> More recently, the Wright brothers first used a moveable rudder on their 1902 glider, and also used one on their famous 1903 airplane, generally recognized as the first airplane capable of sustained, controlled flight. <S> Having said all that, I wouldn't be surprised if someone located an earlier example of a rudder in a drawing or even an operational (small) model airplane or glider. <S> It is a fairly intuitive concept, deriving directly from naval technology-- in fact, the naval precedents might well have tended to lead early inventors to overestimate the advantages and results of having a movable rudder on an airplane.
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In the lighter than air category, the Giffard Dirigible (1852) had a sail like rudder in the aft of the ship.
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Why are the Boeing 747-8 engines on the wings spread apart? I ask this because the Boeing 747-236 had the engines close together while the 747's have them spread apart. Does it have anything to do with the amount of thrust of the aircraft? Look at how spread apart the engines are: Now look at how close together those engines are on the Boeing 747-236: <Q> That picture of the 747-200 you have with the engines in a pod together like a B-52 is a movie prop. <S> http://www.airliners.net/photo/Boeing-747-236B/1070481/ <S> All real 747s from the -100 through the -8 have their engines positioned like the first picture. <S> EDIT - Federico's response reminded me of another aspect of the engine position, and to answer your original question of why they're spread apart. <S> If the engines are too close together, they're essentially competing for the same amount of air, and at high power settings, the interaction between the two fans will disrupt their operation, potentially causing engine stall/surge. <S> Additionally, the 747 uses thrust reversers, and the spacing between the engines <S> helps ensure that the reverse flow from each engine doesn't impact an adjacent engine, for the same inlet distortion reason. <S> I assume, though I don't know the details of this, that the B-52 can have them that close together because they've shown that the inlet geometry, airflow required by each engine, whatever other magic of fluid dynamics that I know nothing about, prevents the engines from distorting each other's airflow enough to cause an issue. <S> The 747 engines require a lot more air, and generate a lot more thrust, and are potentially more sensitive to inlet disruption than the engines on the B-52. <S> This last paragraph is mostly a guess on my part as I'm not an aerodynamicist, but it's inferred from issues we've had to deal with on the 747 and other related airplanes. <A> In addition to what Stickhog's answer says, the fact that all 747s (and A380s) have their engines spread apart has to do with the "single point of failure" concept. <S> Consider for a moment the picture of the movie prop you posted, if one of the pylons suffer any kind of mechanical failure, you lose 2 engines. <S> The same with one of the engines suffering explosive failure or uncontained fire. <S> Having the engines separated from each other reduces the risk that a failure that renders one engine inoperative will affect also another engine. <A> Short answer <S> It's the vastly different flow conditions from static to cruise which demand a separate placing of high-bypass-ratio jet engines. <S> They would produce less thrust and more drag when paired. <S> Why were there paired engines at all? <S> The early jets had their engines mounted directly beneath or in the wing, and comparisons between separately mounted and twinned engines showed a slight advantage for the latter due to lower wetted surface area and less impact on the wing. <S> Arado built two four-engined prototypes of their Ar-234 <S> jet, one with separate engines (V6, see directly below) and one with paired engines (V8, further down). <S> This twinned arrangement works well with turbojets and low-bypass-ratio turbofans. <S> The Boeing B-47 and B-52 bombers, and among airliners <S> the Illyushin 62 and Vickers VC-10 all had paired engines. <S> However, with the increasing airflow of high-bypass-ratio engines the interference between both will turn pairing into a disadvantage. <S> In cruise, only the central stream tube flowing towards the engine will be ingested , and the rest will spill over the intake lip. <S> Placing a second engine directly next to the first will block the flow of spilled air on that side and will increase spill flow on the opposite side. <S> This will most likely cause massive separation there if the intake is not heavily modified, leading to noticeable drag increase. <S> Also, the now asymmetric flow in the intake would reduce the efficiency of the fan - it needs very homogenous flow over the full cross section in today's engines. <S> Conversely, at low speed the engine sucks in air from all around and will face competition from a second engine, such that both will not be able to ingest as much air as when mounted separately. <S> The consequence of pairing would be reduced thrust during take-off. <S> The initial disadvantage of separate engines, their collective impact on wing aerodynamics, is now greatly reduced by mounting them on pylons , so they are ahead and below the wing. <A> As well as the issues relating to the aerodynamics of the engine intakes and single-point-failures, the distance of the engines from the aircraft center-line affects the vibration frequencies of the wing and hence the flutter stability margin of the aircraft. <S> That turned out to be a significant problem on the first version of the B747, to find a compromise position which could use three different engine types from the three engine manufacturers on a common wing design. <S> The first commercial jet airliner design addressed those problems by "twinned engines" buried in the wing root. <S> For pictures see https://en.wikipedia.org/wiki/De_Havilland_Comet . <S> That design persisted in the derivative Nimrod military surveillance aircraft https://en.wikipedia.org/wiki/Hawker_Siddeley_Nimrod until its recent retirement. <S> The problems of trying to shoehorn a modern engine into that airframe configuration, and meeting modern safety standards (as opposed to 1950s era standards) was one of the problems which resulted in the proposed upgrade of the Nimrod MR2 to the MR4 to be abandoned (The MR2s were retired from service in 2011).
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Spacing between the 747s engines is important due to the need to maintain sufficiently clean airflow into the inlet.
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Why does condensation form on the wing especially during take-off and landing? To start off, yes this question was asked before , yet I don't find the answers satisfying and here is why: It appears to me that this phenomenon only appears during the approach phase of a flight and during low speed turns, or rather when the angle of attack is rather high . Also, usually the flaps are deployed when it happens, yet I'm not sure if that makes a difference. Considering this, the answers wouldn't necessarily answer my question. They all talk about how there is a lower pressure above the wing, which causes the dewpoint to drop and thus makes the water condense. But is there a "lower" lower pressure when the angle of attack is higher and therefore making this phenomenon occur more often? Or is the point at which the laminar airflow gets turbulent (which moves forward as the aoa is increased) an important factor here? Here is a picture to show what condensation I mean: And a more extreme one: <Q> Yes, speed and flaps do make a difference. <S> The lift created by the wings is approximately constant over the duration of a flight. <S> With full tanks, it is higher at the beginning of the flight, and when the aircraft banks, it is again higher to create the centripetal force for changing its course. <S> But the difference is small¹. Lift is caused by a pressure difference between the two sides of the wing. <S> In cruise, this difference is low but extends over much of the wing's chord . <S> At low speed, however, the suction on the top surface has a peak right aft of the leading edge, so the maximum suction is bigger than it is in cruise. <S> Exactly this changed pressure distribution causes the humidity to condense, because it lets the air's relative humidity rise above the condensation point. <S> In cruise, the pressure change is lower and the dew point is not exceeded. <S> Also, since the airplane flies slower when close to the ground, the air has more time for the condensation to develop. <S> See below for a color-coded plot of the speed distribution over a typical airliner airfoil in the landing configuration. <S> Red symbolizes the lowest speed (highest pressure), while purple stands for the highest speeds with the lowest pressure. <S> Such suction peaks must be avoided in cruise to enable the aircraft to fly at a high cruise Mach number. <S> Airliner airfoil with high lift devices in landing configuration (picture source ) <S> ¹ <S> The fuel fraction of airliners rarely exceeds 40%, and the added lift in a 30° bank is only 15%. <A> As the angle of attack increases, the pressure on the upper surface of the wing becomes lower. <S> The following figure shows this. <S> Note that the pressure on top is suction. <S> Source: <S> avstop.com <S> During the landing phase, the angle of attack of the aircraft is higher compared to to other regimes. <S> This is the reason condensation clouds are formed during the landing phase. <S> However, the clouds are formed during any subsonic maneuver that reduced pressure over the upper surface of the wings, like high-g turns. <S> Source:www.telegraph.co.uk <A> Let's remember for a second that on the upper side of the wings there is lower pressure than the free stream (air far from the aircraft). <S> If the aircraft is travelling through humid air, the adiabatic process (which all packets of air that end up near the wing have to "suffer") dictates that: $$P_{\infty} ^{(1-\gamma)} \cdot <S> T_{\infty} <S> ^\gamma = <S> P_{wing} ^{(1-\gamma) <S> } \cdot T_{wing} <S> ^\gamma $$ <S> and since we just remembered that $P_{wing} < P_{\infty}$, it means that $T_{wing} < T_{\infty}$. <S> Still from the wikipedia link above: <S> Adiabatic cooling occurs when the pressure on an adiabatically isolated system is decreased, allowing it to expand, thus causing it to do work on its surroundings. <S> When the pressure applied on a parcel of air is reduced, the air in the parcel is allowed to expand; as the volume increases, the temperature falls as internal energy decreases. <S> If the initial $T_{\infty}$ was already low enough, or if there was enough umidity in the air, the packets of air above the wings finds themselves below the dew point, producing the condensation that prompted your question. <S> But is there a "lower" lower pressure when the angle of attack is higher and therefore making this phenomenon occur more often? <S> Remember that the lift is roughly $ <S> $L \propto <S> \alpha \cdot V^2$$ <S> and since the weight of the aircraft is not reduced, to keep the lift constant at lower speeds (such as the speeds just before landing) <S> you need an higher $\alpha$. To prevent the need of extreme angle of attacks, the effect of the flaps is to increase the $C_{l\alpha}$, meaning that for the same angle of attack you get more lift, changing the proportional relationship above. <A> When you next snap open a can of fizzy drink watch carefully at what first comes out of the hole. <S> A tiny cloud of condensation that quickly disperses. <S> This is your personal adiabatic decompression demonstrator. <S> It's exactly the same Physics as what's going on in the photos above.
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Yes, higher angles of attack mean higher lift, that is generated by higher differential pressure between upside and underside of the wing.
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Can fuel be stored in the anti-shock bodies? lets say an airplane needs to get to a certain route but doesnt have the fuel to do and it needs to store in the anti-shock bodies. Is it possible? <Q> Tip tanks of the period when aircraft flew already supersonic and jet engines were still very thirsty are a good example. <S> Below you see the area-ruled tip tank of the F-5. <S> F-5 tip tank (picture source ). <S> Now that @voretaq7 got me thinking, I should also mention the "Doppelreiter" fuel tanks (slipper fuel tanks) which were used on some German fighter airplanes in WW II. <S> They were mounted above and behind the wing, and to everyones surprise they had little impact on the top speed of the airplanes, and in case of the Me-309 helped to increase it slightly. <S> They were the first practical application of Küchemann carrots and worked much like the flap track fairings of today's airliners. <S> FW-190 A with Doppelreiter tanks. <A> Fuel is stored in fuel tanks, which typically have two requirements: They must be sealed so as to contain the fuel in all probable flight attitudes. <S> (Ideally they will keep it contained in a few improbable ones too.) <S> They must have appropriate plumbing to get the fuel to the engines. <S> (There are some exceptions to this, but fuel in a tank you can't use is not helpful in flight .) <S> Anti-Shock bodies are typically not fuel tanks - they meet neither requirement as they are not watertight (fuel will just pour out of them), and there's no plumbing to get the fuel out of, or for that matter into them. <S> As "Exhibit A", take a look at the anti-shock bodies around the 787 flap tracks & actuators- <S> Note that the anti-shock body is hollow, but unsealed. <S> Any fuel (or water) in here would simply pour out the trailing edge when the flaps are extended. <A> In at least one case, yes! <S> The Convair 990 jetliner (a derivative of the earlier Convair 880 ) had large, prominent antishock bodies on its upper rear wings, easily seen in this photograph of a retired NASA 990: (Image by NASA, via Stahlkocher at Wikimedia Commons .) <S> These antishock bodies - particularly the larger inboard ones - also served as fuel tanks, and held the aircraft's fuel-dumping apparatus. <S> Wikipedia sums it up nicely : <S> One change from the 880 was the large anti-shock bodies on the upper trailing edge of the wings to increase the critical Mach and reduce transonic drag. <S> The inboard shock bodies, which were larger, were also used for additional fuel tankage. <S> Later during the design period, Convair modified the design to include fuel in the outboard pods as well, but during the initial test flights the extra weight caused the outboard engines to oscillate in certain conditions. <S> The pods were redesigned once more, and shortened by 28 inches (710 mm), causing increased drag. <S> The inner set of pods also served a secondary role as fuel dumps for the fuel tanks, and the outlet pipe is prominent.
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Yes, and there have been cases of this.
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How close are we to replacing pilots with computers? Recently someone on another thread recommended the following video: Andrew Godwin - What can programmers learn from pilots? - PyCon 2015 where the speaker, at about ~3:14, talking about pilots mentions: not to the point where we can replace them with computers, because we're not there yet which got me thinking: How close are we to replacing pilots with computers? (like totally) <Q> As a person that "tries to replace pilots with computers" I personally say: not even close. <S> The processing power (certified for flight, not the latest pentium sitting under your desk) is too behind, in particular concerning the point here below. <S> Synthetic vision is still extremely lacking. <S> This is currently the biggest hurdle to overcome. <S> While pilots can look out of the windows and assess the situation (with some limits, admittedly), computers still have several problems with it, starting from a general lack of cameras and going all the way to the daunting level of processing power required. <S> Ability to adapt is still a long way to come. <S> Computers are "fundamentally stupid", they do what they are told (programmed) to do, they are not capable of adapting to an unforeseen (and never experienced before) emergency. <S> There are several people working in machine learning and the field has advanced significantly in the latest years, but good luck certifying those programs. <A> This is a complex question and one that involves both a technical aspect as well as a legal aspect. <S> From one standpoint there is nothing stopping the FAA from requiring that a human pilot remain in the plane should anything go wrong (or simply to create jobs). <S> Lobbying power should not be underestimated here, there are lots of pilots (and a union behind them) that would be out of work. <S> But lets talk machine take over for a minute. <S> In some regards parts of the systems do exist. <S> Obviously autopilot to an extent can fly a plane but this generally involves some human interaction and generally holds speed/altitude/heading a change in any one of those may require physical control changes. <S> In a similar vain auto-land systems do exist and they do work. <S> HOWEVER they are complex to set up and require human interaction to currently be used. <S> As far as I know there is no automated system that can currently control takeoff (i could be wrong about that though). <S> Do we possess the pieces to assemble a self flying plane, possibly... <S> To do so, and to get it FAA certified is a very big topic. <S> The other issue that arises is updating the whole ATC system. <S> If you have not been following the news this is already a mess. <S> But lets say you had a plane that had no one flying it. <S> If ATC needed to reroute the plane, or issue a change in course it would need a system to do so. <S> Currently that is handled via a radio and person to person communication. <S> You would need to dispatch some kind of command to the plane via a data link to do it in an automated system. <S> Then again you can automate ATC etc. <S> etc. <S> (lets not go down that road. <A> How close are we to replacing pilots with computers? <S> In some ways, this has already happened in some limited areas. <S> Flight Engineers and Navigators <S> As a precursor to replacing pilots, we have already replaced non-pilot crew on the flight deck. <S> A significant problem for the remaining pilots can be maintaining their skills during their time in the cockpit when they spend long hours mostly monitoring systems rather than doing hands-on piloting. <S> I suspect, a lot of what commercial and military pilots do boils down to issuing commands to computers, rather than manually (if indirectly) moving control surfaces. <S> Bomber pilots <S> In the first gulf war, 297 missions were flown by autonomous aircraft. <S> Many explosive payloads were delivered to targets by small aircraft that flew hundreds of km. <S> These navigated and flew without any on-board or remote human pilot controlling them. <S> Cruise missiles. <S> The alternative would presumably have been greater numbers of human pilots in conventional bombers dropping smart bombs over the target. <S> Ground attack pilots <S> Some jobs that would have been carried out by a pilot inside a ground-attack aircraft are now carried out by a UCAV with a remote pilot. <S> These UCAVs have increasing amounts of autonomy. <S> Some are intended to have full autonomy. <S> It isn't hard to envisage a not too distant scenario where the main human interaction with the aircraft is not piloting it, but authorizing firing of weapons. <S> Helicopter pilots Jobs like power-line inspection are, in some remote areas, mostly carried out from helicopters with human pilots but we seem to be on the brink of replacing some of those pilots with drones. <S> That seems a few technically short steps from using autonomous drones. <S> The main time-consuming barrier is probably regulatory change. <S> Currently, to operate a drone for this purpose, you don't need to be a licensed pilot. <S> Is such a drone operator a pilot. <S> Have they replaced one? <S> (like totally) <S> As others have answered, nowhere near.
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The flight engineer role has been replaced largely by computerized engine systems.
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Why does the bottom part of an aircraft nose curve upwards? As you can see in this picture the bottom of the fuselage curves upwards to form the nose. <Q> If you move the tip down, the slope above it will either be steeper, leading to higher drag, or longer, leading to greater length and thus weight; or you don't extend the plane, but then the longer sloped part will provide less internal volume. <S> Only the cockpit windows, which need to be on the sloping part, shift the nose a bit down, to the centre of the cross-section just before cockpit. <S> Cars are different. <S> For a car you want the bottom surface flat, because you don't want to push and compress air in the gap between the vehicle and the ground. <S> But aircraft has air all around and it is most efficient for it to push air equally to all sides, so a circularly symmetrical shape works best. <S> Also note that lift is yet another thing. <S> Lift requires a sharp, downward-sloped trailing edge. <A> The RAF's Hawker Siddeley Nimrod does. <S> Source: <S> Wikimedia <S> But only because it is an anti-submarine aircraft; its radar is designed to point at the sea, not the air. <S> Of course you could still put weather radar in a downward-pointing nose, but that would be a waste of space and engineering. <S> Commercial aircraft strive for efficiency, and in this case it makes more sense in terms of balanced aerodynamics and instrument placement for a jetliner to have a nose that curves both upwards and downwards. <S> Also take a look at another view: <S> Source: <S> airliners.net <S> Where would you put the baggage? <A> The nose of the aircraft has to satisfy a number of requirements, some of them contradictory, like <S> The nose shape should produce the least drag <S> The pilots should have good visibility <S> It should house the weather radar and related avionics <S> The cockpit noise should be minimal <S> For example, the aerodynamic design of Concorde meant that the nose had to droop during takeoff/landing for good pilot visibility. <S> For aircrafts flying in transonic regime, some of the best nose shape from aerodynamic standpoint would be to have a symmetric body of evolution based on Haack series of curves. <S> " Nose Cone Haack Series " by Andersenman - Created with Gnuplot using the Haack series formula and a selection of input values for C relevant to the article. <S> Values are 0, 0.333, 0.667, 1 and 1.333.. <S> Licensed under CC0 via Commons . <S> However, due to fact that the cockpit is on the upper part of the nose region, this arrangement increases the complexity of cockpit windows (they will have to be curved in two axes, atleast) if the pilot has to have good visibility. <S> As a result, center of the the nose is usually moved downwards. <S> This is the reason for the common profile seen in aircraft noses. <S> However, the disadvantage of this profile is that the pressure is high in the windshield region compared to the flat profile. <S> Source: <S> AGARD LS-67, Paper-4 <S> The main problem with (dual) curved cockpit windshield is the tighter quality control required and the associated costs. <S> However, in 787, Boeing has achieved a continuous surface variation. <S> Source: airliners.net <S> It is to be noted that the aerodynamics is only one of the criteria for nose design. <S> For example, a nose with similar profile to that of 787 was proposed for A350. <S> However, it was later changed to accommodate other considerations. <S> Source: airliners.net <S> According to Didier Evrard, executive vice-president A350 programme, There have been a number of trade-offs in the nose area, enabling us to maximise the volume of the cockpit and avionics bay while optimising aerodynamics and the positioning of the nose landing gear " A350xwb nose 2009B " by Luis E. Contreras. <S> Licensed under CC BY-SA 3.0 via Commons . <A> Just to add to other answers, evenly sloped fuselage on the top and bottom in the front of the aircraft would create lift and drag somewhat equally in top and bottom direction, thus rendering fuselage aerodynamically neutral like BillOer mentioned in comments. <S> If you were to design fuselage like the vehicle below, downforce generated by the upper part of the fuselage would push the whole assembly downwards - this is desirable for road vehicles as the more planted on the road they are, the better. <S> For aircrafts however, balance is the key:
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Having the tip of the nose in the centre gives best combination of aerodynamic performance, weight and internal volume.
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Why doesn't the landing gear get raised on the first flight of a new airplane? This image shows the A350 first takeoff high in the air and the landing gear is still down. Why didn't they retract it? <Q> Test flying is thoroughly planned, and of the many things to test during development, the landing gear is just a minor part. <S> In the first flight the goal is to check out basic functionality and how well the low-speed performance was predicted. <S> The landing gear can wait for one of the later flights. <S> You can see in the photo of the A350 that the slats are extended and the flaps are in take-off position. <S> The pilots are busy testing handling in take-off configuration, and for that the gear must be down. <S> You can be sure that they also tested the landing configuration at altitude before going down to land. <S> Generally, the tested envelope of the aircraft will be expanded step by step. <S> Since every flight will contain a take-off segment, it is prudent to check out this part of the envelope first. <S> Once the low-speed regime is tested, consecutive flights will take the aircraft to higher speeds, and only then will it be necessary to retract the gear. <S> Also, the first flight of a newly developed aircraft has become a ceremonial affair. <S> After having spent hundreds of millions of dollars or euro, and with all the media attention, nobody wants to live through the embarrassement of a gear failure on occasion of the first flight. <S> This was not always the case. <S> The F-100 <S> went supersonic on its second flight; taking this kind of risk would be unimaginable today without the pressure of an arms race. <A> Aircraft flight testing a rigorous and elaborate affair, with the aircraft first tested at low dynamic pressures and as the performance data is received and analyzed, the flight envelope is expanded slowly. <S> During the first flight of test aircraft, the approach is to take minimal risk. <S> Keeping the landing gear extended serves two functions: <S> Landing gear systems are very complex in themselves and it serves no purpose to check them in the first flight. <S> There is a possibility that they may not retract or may not extend after retracting. <S> As Peter pointed out, this is not a good thing to happen in first flight. <S> Also, in case the aircraft has to land in case of any emergency, it is better to keep the landing gear in extended position. <S> There are a few cases in which the landing gear malfunctioned during the first flight. <S> In the first flight of YF-22, which went on to become the F-22, the landing gear retraction was not planned. <S> However, when it was tried in subsequent flights, the gear did not retract due to software issues. <S> However, it has to be noted that the while retraction was software controlled, extension was hardwired for safety. <S> Another case of landing gear failure is the NASA dream chaser plane, which suffered landing gear malfunction in its first free flight. <S> As the aircraft approached the runway, the left landing gear failed to deploy, and the aircraft skidded off the runway and was damaged. <A> The simple and easy answer is that the first of any new aircraft design, no matter how well-engineered <S> , well-constructed and/or derivative of earlier designs, is a complete unknown. <S> Gear extension, retraction and emergency release are all thoroughly tested many, many times with the aircraft on a lift prior to the first flight, but still, anything can happen, and better safe than sorry (especially in a civilian aircraft design without an ejection system).
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The first flight is always gear-down because if there's any problem, the test pilot/crew needs to be able to get the plane back down on the ground without having to deal with any additional issues (like not being able to get the gear back down).
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Why don't airliners have rudders on the winglets? There are a couple airplanes out there that use the winglet as the rudder, but why doesn't the winglet have a rudder on it to increase the turn of the aircraft? <Q> The purpose of the rudder is to control the heading of the aircraft. <S> It turns the aircraft by creating an aerodynamic moment about the vertical axis of the aircraft. <S> The moment is product of the aerodynamic force and the arm. <S> image: <S> NASA <S> The aerodynamic force is the the side force on the rudder, the arm is the distance between the rudder and the centre of gravity of the aircraft. <S> It would be possible the have airbrakes on the winglets / wingtips and use differential braking to create the rotating moment. <S> This is done for example on the B2 which doesn't have a vertical stabilizer. <S> The added complexity and weight increase makes it an unattractive option for conventional aircraft. <A> Short answer: <S> Vertical tails create more yawing moment per unit of drag. <S> The rudder works by creating a side force, just like a wing creates lift. <S> This incurs a small amount of drag (about a tenth of the side force). <S> Even on a swept wing their lever arm in lengthwise direction is small compared to the wingspan. <S> If the winglets would be used as rudders, they would be most efficient as drag devices, because then their force will act on a longer lever. <S> This has been done on flying wings (note that the SB-13 tailless glider has a maximum rudder deflection of 70° in order to create drag). <S> SB-13 <S> in flight (picture source ) <S> This makes the use of a rudder vastly more efficient for creating a yawing moment than using winglets. <S> The deflection of winglet rudders will also change the lift distribution on the wing, so they do not only create a yawing moment, but also a rolling moment. <S> Vertical tails wich are high above the roll axis also add a rolling moment, but this is comparatively small to the rolling moment of a winglet with rudder on a high aspect ratio wing. <S> In both cases, the rolling moment acts against the desired roll direction, so it is preferable again to create the yawing moment with the vertical tail. <A> It is possible, but just not that useful. <S> Controllability <S> In order to maximize the moment incuded by the rudder (or keep the rudder as small as possible to provide this moment), you want to place the rudder as far (in longitudinal sense) from the center of gravity. <S> This increases the moment induced, and thus the effectiveness of the rudder. <S> In a normal airliner, you'll have a tube with wings in the middle, and thus the most aft part to place the rudder is at the end of the tube. <S> On the aircraft in your picture, the most aft part is the wing tip, so it makes sense to put the rudder there. <S> Structural reasons <S> If you place the rudder at the end, this will mean there will be substantial forces induced at the tip of the wing if you use the rudder. <S> This means that you will have a substantial bending moment added to the wing, making it much heavier. <S> This is further discussed in Winglet vs span extension <A> The existing answers miss what seems to be a fairly obvious answer: the winglets are an afterthought, added to existing, proven designs (e.g. 737) to improve fuel economy. <S> Putting rudders on them would require running control cables, perhaps strengthening the wing structure, &c, rather than just bolting on new tips. <S> You could perhaps design a new airliner from scratch to do this, but again, why abandon a proven basic design unless there are large gains to be had?
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If the rudder would be on the winglets, the side force of the rudder would act at a short distance behind the centre of gravity, reducing the effectiveness very much. Vertical tails create less adverse rolling moment for a given yawing moment.
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Which aircraft manufacturers still include Vertical Situation Displays (VSD) feature in their cockpits? I'm curious about the aircraft manufacturer names who still interested in including the VSD on lower part of Nav Display (I read about Boeing 737 only). Are there any other guys on this filed still? I know this would be useful during the landing and takeoff. <Q> VSD Boeing have a patent on a VSD (Vertical Situation Display), which is part of the Honeywell EGPWS <S> (Enhanced Ground Proximity Warning System) <S> which first appeared as an option on 737s <S> about twelve years ago I think. <S> The system will be offered by early 2003 as a customer option on in-production 737s and by retrofit on 737-600/-700/-800/-900 airplanes already in service. <S> Implementation of the system on other Boeing models is under consideration. <S> - Boeing "Aero" magazine <S> I don't know if Boeing offer licences at acceptable terms to their competitors, or if Honeywell make available, to other aircraft makers, products that incorporate features licensed from those patents. <S> CFIT <S> It is possible that other manufacturers have equivalent options for alerting pilots of potential CFIT (Controlled Flight Into Terrain). <S> TAWS & EGPWS <S> The FAA, for example, requires aircraft be fitted with systems that comply with TAWS <S> (Terrain Awareness Warning Systems) <S> requirements. <S> EGPWS systems satisfy that requirement. <S> TAWS requires a terrain awareness display <S> but I dont think it requires something specifically like Boeing's VSD. <S> Airbus for example, on at least their A350 and A380 models, have a navigation display that incorporates "vertical flightpath data". <S> I guess they don't call it a VSD. <S> They also have what I think is a fairly common type of terrain display showing "peaks" ahead of the aircraft. <S> - Sources: FlightGlobal and Airbus RNP <S> It may be that some of the issues addressed by the VSD are, for many airports in mountainous terrain, taken care of by RNP (Required Navigation Performance) <S> which prescribes the required navigational accuracy of the aircraft's navigation systems. <S> Generally the aircraft is required to be able to follow an approach path that consists of a sequence of curved three-dimensional paths to the runway that avoids terrain. <S> I imagine this path is pre-programmed into the navigation systems along with the go-around paths. <A> Here is an image of the 787's flight deck showing the VSD on the copilot's side: <S> Source: Airliners.net <A> For the smaller aircraft market (and the big guys for that matter) many of the common EFB applications will display this information . <S> ( source )
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There are similar vertical profile displays available on Boeing 787, Airbus A380 and Airbus A350 aircraft.
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Why does the A340 have 4 engines instead of 2? I have noticed for a while the A340 has four engines and the Boeing 777 only has two engines and they are about the same size. So why can't an A340 have two engines instead of four? A340 . B777 On a jumbo jet like the B747-8 four engines are a requirement. <Q> The A340 was designed at a time when ETOPS (Extended-range Twin-engine Operational Performance Standards) had not been developed. <S> Some airlines preferred two engines which reduced operational costs, while others preferred four engines with increased reliability at an additional cost. <S> Airbus decided to split the development into distinct aircraft having the same wing and airframe - A330 with two engines and A340 with four engines. <S> However, as time has passed, ETOPS has become the norm with improved engine reliability, and A340 production has been stopped. <S> Almost all the civil airliners under development now have two engines. <S> The Boeing 777, on the other hand, was developed with twin engine operation in mind. <A> If it had only 2 engines, it would be an A330. <S> The main difference between the two models is that the A340 has four engines, and it was designed and produced specifically for airlines that needed that. <S> This benefit has since become smaller due to improved reliability of engines (or improved trust in the reliability), since the maximal distance from nearest landing opportunity is determined mainly by how long time you dare to need a plane to stay aloft after an engine failure enroute, before the risk that the remaining engine will randomly fail too becomes unacceptable. <S> The A340s that are already built keep flying until they reach the end of their operational life, of course. <S> The only large quadjets still in production are the 747 and the A380. <S> The A380 needs more than two engines because of its size, in order to produce enough takeoff thrust. <S> The 747 might conceivably have ended up with two engines if it was designed from scratch today. <A> I have a model of an Airbus A340-600 and a Boeing 777-200 and it is easy to notice by size that the 777-200 uses more powerful engines: (top: 777, bottom: A340)
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At the time the A330/A340 series was designed, having more than two engines was an operational benefit because a two-engined plane needs to stay within a certain range of diversion airfields, which made the A330 unsuitable for some routes.
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For the same airspeed does the attitude of an airplane change with varying wind directions? Should one maintain a constant attitude if he wants to hold a constant speed or does the attitude vary depending upon the wind direction? <Q> If by attitude you mean pitch attitude or angle of attack (which is how I automatically understood this), no it does not change as this is related to the aircraft's airspeed through the air. <S> So an aircraft flying downwind will have the same AOA as the same aircraft at the same airspeed flying upwind. <S> If you want to fly at the same groundspeed upwind as downwind, then you would have to vary your airspeed, which means varying you pitch attitude or AOA. <S> This might not be possible if say you were in a light aircraft in a 40 knot wind at altitude which cruises at 100 knots. <A> Yes. <S> Constant pitch, constant airspeed. <S> "Pitch plus power is performance, pitch for speed, power for altitude." <S> Wind affects groundspeed , not airspeed (except for sudden gusts or sheer). <S> Unless an aircraft has landed or is fastened to the ground, like a tethered balloon or gyrocopter, an aircraft is always moving along with the wind. <S> Think of an airborne aircraft as being one with the wind. <S> Wind exists only from the earth's perspective, it has no affect on a flying aircraft. <S> Except... <S> Wind does affect heading and groundspeed and becomes important when navigating relative to the earth. <S> It's especially a factor in landing and taking off! <S> So, yes. <S> Constant power, constant attitude will result in constant airspeed, no matter what the wind down on the ground is doing. <A> The lift generated is proportional to the airspeed and the angle of attack (amongst other factors). <S> To maintain level flight, by maintaining the same lift, the angle of attack, for the given weight and altitude, will remain constant <S> therefore there is no attitude change. <A> If the change is in direction, the airplane will change its yaw (also known as heading) angle, so that the track angle (the direction along which it is travelling) does not change. <S> For more informations about the differences between heading, track and similar angles, you can read this other question .
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If the wind direction changes, the aircraft will maintain a constant airspeed, by increasing or decreasing power.
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What airplanes can I fly with an EASA PPL license? Weird as it might seem, I'm not 100% sure what airplanes I can flywith an EASA PPL(A) license. During the training the instructors wouldtell me that I can fly airplanes up to 2000 kg MTOW and 5 passengersor so, but I think they are wrong and this applies only to the (old)national rules (Germany in this case). The license states that I have a SEP (land) class rating. I havesearched through the EASA rules (a cumbersome task on its own) andnowhere could I find a weight or passenger limit, nor a specificdefinition of what exactly qualifies as a SEP. So the question is, what aircraft am I entitled to fly with my PPL(A)license? Do aircraft with specificities such as a retractablegear fall into the same category? Please also point to the source of the applicable legislation. By the same token, may I/may I not fly light aircraft such as e.g. aK-10 Swift? <Q> Well to fly B737 you will need IR, ATPL exams as it's multi crew airplane, MCC and TR. <S> I don't know if it makes sense <S> but you can put everything on PPL if you want. <S> You only have SEP so you only can fly SEP airplane. <S> SEP is just any airplane with single piston engine. <S> But CAA can decide to require TR for any aircraft if they consider it to be complex... <S> If you get IR and TR and you can fly private jets without problem with PPL. <S> But you see that to get everything you will need to know the same theory as for ATPL license. <S> As for K-10 Swift it's Ultra Light aircraft. <S> Regulations differ by country I think. <S> In my country CAA doesn't issue ultralight licenses but ultralight planes association. <S> General rule is that you will need difference training. <A> I was wondering about the same and here is what I found. <S> Yes, for LAPL license holders, when switching to another airplane within the same class rating (don't mix it up with type rating) <S> the familiarization training shall be performed and signed off by instructor. <S> It's stated in the "FCL.135.A LAPL(A) <S> — Extension of privileges to another class or variant of aeroplane" section of the "Part FCL" . <S> Before the holder of an LAPL can exercise the privileges of the licence on another variant ofaeroplane than the one used for the skill test, the pilot shall undertake differences or familiarisationtraining. <S> The differences training shall be entered in the pilot’s logbook or equivalent document andsigned by the instructor. <S> There is no such requirements for PPL(A) holders. <S> Further away there is the section "FCL.700 Circumstances in which class or type ratings are required" which has class rating SEP (land) with many aeroplanes : SEP (land), SEP (land) with variable pitch propellers, SEP (land) with retractable undercarriage etc. <S> All those are aeroplanes . <S> The D to the right means that Whenever (D) is indicated in one of the lists mentioned in paragraphs (a) to (c), it indicates that differences training in accordance with FCL.710 is required. <S> Ok, going down to the "FCL.710 Class and type ratings — variants" where we have <S> In order to extend his/her privileges to another variant of aircraft within one class or type rating, the pilot shall undertake differences or familiarisation training. <S> I don't know why aircraft is used in this section instead of aeroplane , but later again it's explained as <S> (a) Differences training requires the acquisition of additional knowledge and training on an appropriate training device or the aircraft. <S> (b) Familiarisation training requires the acquisition of additional knowledge. <S> Conclusion: <S> the minimum required is "Familiarisation" which is just "acquisition of additional knowledge" which has no any requirements for legal sign off or so. <A> With an EASA PPL(A) you can fly single engine piston aircraft, for example the Cessna 172 or the tiger moth <A> My understanding is that if you are not flying for commercial purposes the PPL has no limits on the aircraft weight or complexity. <S> You must however have a Type Rating for the aircraft beyond Sep if required. <S> I have flown a few fast jet types on a PPL with a CAP632 which can be issued by any qualified instructor if they are satisfied you have met the military training standards. <S> Hope that helps.
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You can fly any airplane with PPL even B737 if you own one.
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How do young pilots in the USA accumulate 1500-hours to become a first officer? The FAA requires 1500 hours as a pilot : The rule requires first officers — also known as co-pilots — to hold an Airline Transport Pilot (ATP) certificate, requiring 1,500 hours total time as a pilot. I am just interested in how can you get 1500 hours? This number is super huge unless you fly a trans-continental airliner. But you cannot fly an airliner without 1500 hours. Even having a private airplane, 1500 hours I assume will cost a lot - probably more than €500,000 in Europe. What is so specific about the USA? I fly gliders and a tug plane. I fly every weekend without exception and even sometimes after work. But I won't reach even 100 hours during the season. So to reach 1500 hours will take 20+ years. What about if you fly aerobatics...? Well of course there are some people who have these numbers but they are in their fifties and have spent all their lives in aviation! They don't even think about starting afresh in a first officer's career. So I am just curious how do young people log 1500 hours in the USA? <Q> 1 word: Instruction. <S> I learned to fly in the US, and all but one of the 10-15 instructors at the school were young guys who had a Commercial license and were just building hours while doing their exams and applying to airlines. <S> This meant they were actually getting paid (not particularly well, I hasten to add!) <S> to build hours, rather than spending money on an airplane, or rental. <S> They say you don't become a pilot for the money, you do it because you love it. <S> Nothing could be closer to the truth IMO. <A> I think the most common answer will be, instructing. <S> You'll build hours much faster doing that, since it sounds like you're only getting about 100 hours / year now, which isn't much. <S> Of course, the difference between a good instructor job and a bad one can be huge. <S> Other routes, which are not necessarily incompatible with instructing, would be things like traffic watch flying and banner tow. <S> At some point, most pilots probably start flying for somebody in a job that doesn't require ATP minimums -- night cargo, tour flying, etc. <S> These jobs aren't entry level so they'll require some amount of experience, but not 1500 hours. <S> One pilot I know started doing right seat work at SimuFlight, filling the seat & reading the checklist for pilots who came in for the course without their own copilot. <S> Eventually got an offer to start flying right seat for one of the pilots that came through for refresher training. <S> That's hardly common, but one-off stuff like that is out there. <A> This link helps explain the differences. <S> This would be small commuter airplanes, cargo, and air taxi operations. <S> Also, experience does not have to come from US regulated air operations, you could go elsewhere in the world where the 1500 hour rule does not apply and get experience as a first officer <S> and it should still count.
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Instructing is the most common route, however you can also fly as a commercial pilot in part 135 operations, which would be anything 30 seats or under charter, or 9 seats or less as a scheduled flight, and <= 7500 lbs payload.
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Why are combi airliners no longer being built? Why are combi airliners no longer being built? Is the reason structural, economic or regulatory? <Q> While combi configurations are rare, they do have a place -- for instance, when operating narrowbodies into remote locations which have a demand for cargo that exceeds what can be put in the belly, but also need pax transport. <S> The most recent combi configuration I can find a source for is the 2008 work done by Aviation Traders to configure Iron Maiden's touring plane . <S> In this case, they used the existing seat rails to mount pallet fittings in order to avoid structural changes to the floor, and also are taking special steps (such as firebagging of cargo) to mitigate against a main deck cargo compartment fire. <S> As to why they aren't made otherwise? <S> It clearly isn't operating economics, at least for Alaska Airlines, Canadian North, First Air, and other current combi operators -- otherwise they'd have retired their combis by now. <S> The main issue, I strongly suspect, is actually the unsolved problem of fire suppression in large, main deck class B cargo compartments, such as those found on combi aircraft. <S> Aviation Traders' work on Class F is intended to solve this problem, made famous by the crash of SAA <S> 295 <S> after its main deck class B bay experienced a fire of unknown origin that proved catastrophic. <A> Combi aircrafts are basically modified airliners that carry passengers and/or cargo. <S> Though there are multiple reasons for not combi aircrafts not in use nowadays, the main reason is economic. <S> In case of mixed passenger/cargo operations, the cargo is usually one directional. <S> The aircraft will be half empty in the return flight. <S> The conversion of passenger aircrafts involve some significant structural changes like cutting open a cargo loading door. <S> Source: <S> www.airtransport.cc <S> Air cargo is highly seasonal, while the passenger traffic is not (Except for some spikes during festive occasions). <S> It makes little economic sense to operate combi aircraft while passenger and cargo aircrafts can be operated separately more economically. <S> The conversion of he aircraft to carry cargo is not one of simply removing seats. <S> it involves modification/installation of cargo handling systems, fire extinguishing systems etc. <S> For example, air cargo pallets are standardized and cannot be transferred through cabin doors. <S> The figure shows the work involved in the conversion of a Boeing 757 Source: <S> staero.aero <S> The airline passenger traffic has grown enormously through th years, while the air cargo has not seen such robust growth. <S> So it makes sense to concentrate on only a single sector. <S> Source: <S> centreforaviation.com <S> The only places combi aircraft are used are those in which operating such aircraft is necessary. <A> I think the term is being slightly misused :) <S> A combi aircraft is not a type of aircraft to be built , but rather an aircraft that is simply configured to transport both passengers and freight. <S> Alaska is an example of an airline that uses aircraft configured in this fashion. <S> One reason they aren't more widespread is that they inhibit economies of scale . <A> In addition to the above answers: Tightened cargo security since September 11. <S> Comparing to cargo-only aircraft,the cargo on passenger aircraft or combi aircraft must be restricted and limited. <S> Airfreight charge was kept lower due to big competition in the market. <S> Passenger business might be more profitable in using aircraft space.
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Simply put, combi aircrafts belong to another age of air transportation, while in the present (and near future), it makes more economic sense to operate specialized passenger and freight aircraft. They are more difficult to use effectively - you need a special purpose for them.
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Why was the Bristol Brabazon scrapped? According to Wikipedia , 6 million pounds were spent developing the Bristol Brabazon, and the only prototype was scrapped for 10,000 pounds, that is a 0.17% loss recoup. There was a lot more value in keeping that plane intact than scrapping it, maybe for future projects, or special assignments, or further testing, like an An-225. It held more value as a museum piece, or a "sculpture" in Bristol, than the value from the scrap metal. Was there a reason for being scrapped, other than the 10k in scrapped metal? <Q> You're right, as an exhibition piece it would had been quite an attraction. <S> But it was not up to the Bristol company to decide her fate. <S> During and after the war, most British aviation development was managed by the government. <S> The Brabazon was the result of a committee which set the goal to develop a transatlantic airliner with 1943 technology, not by a company and its technological visionaries. <S> If you had asked people like Willy Messerschmitt in 1943 how the future airliner would look like, he would had basically described a Boeing 707 : <S> Swept wings, turbojet engines, pressurized cabin for about 100 passengers. <S> But Government bureaucrats put the goal for the Brabazon quite differently, and the result was technically obsolete by the time it took to the air. <S> Even before the Brabazon flew first on September 4, 1949, the de Havilland Comet had already flown on July 27, 1949 and was on its way to revolutionize air travel. <S> Its development had started later and was directed by engineers, not bureaucrats. <S> When that became obvious, the bureaucracy felt too embarrassed to keep the Brabazon around. <S> The situation was similar to Beechcraft and the Starship : <S> Burt Rutan's 85% scale prototype was cut into pieces out of spite when it became eventually clear even for Beechcraft's board just what a turkey it was. <S> The same fate befell the Brabazon. <S> But its legacy for Bristol is still very positive - without the Brabazon, it would certainly not employ as many people in aerospace as it does up to this day. <A> You should also consider maintenance costs. <S> Even if you have museum admissions or the like you still must have it running well enough to cover the quite high costs of keeping your airplane together. <S> That they did not keep it for further research <S> indicates IMHO that the plane was simply not seen as a good fundament for further research. <S> I am very sure that the people in charge back then did consider carefully what they do with it. <S> For some reason they would rather write off almost 6 mio and get the money for the scrap metal. <S> Even though mistakes happen a lot, I think that they knew what they did :) <A> why would there be more value in keeping it than in scrapping it? <S> That's simply not true. <S> The ONLY value would be for a few aviation enthousiasts who might be willing to pay the entrance fees for a museum where it would be put on display. <S> But at the time there was a glut in aircraft to put in museums. <S> And of course most British museums at the time (and many even today) didn't charge admittance, they were run as public services for educational purposes. <S> In a country with massive debt, recovering from a long and costly war, where raw materials are scarce, and aircraft to show off to the public are a dime a dozen, scrapping something that has no purpose and contains tons of valuable metals and other materials is the best thing to do, aviation buffs 70 years later who'd like to look at it and marvel at the folly of designers long ago to think something like that would be the future be darned.
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Keeping the airplane will surely cause some kind of cost and the maintaining party has to cover them somehow.
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Are NACA airfoils used in modern aircraft design? I know that NACA is famous for its ducts: Gratuitous Ferrari F-40 from Wikipedia . Mmmm... pretty... It is also well known for its airfoils, and many planes in the early years of aviation used NACA designed airfoils for their wings (for example the Piper Cherokee referenced here ). Piper PA-28 also courtesy of Wikipedia Do current aircraft manufacturers still use stock NACA airfoil designs, start with a NACA standard design then modify it to meet needs, or are the airfoils completely bespoke ? I'm asking about the major airliner manufacturers like Boeing & Airbus , regional jet builders like Embraer , as well as private/GA companies like Cessna , Gulfstream , and, of course Piper . Information on the (few, dozens, hundreds?) of other aircraft manufacturers (and kit designers) that don't pop to the top of my head is also welcome and appreciated. Thinking about this further, I realize it could quickly devolve into a very broad this aircraft uses a NACA standard wing , that one doesn't list. That's not really my intent. A simple yes, this aircraft/wing from 5-10 years ago uses a NACA standard would answer the question completely, as would a the last one I'm aware of is from 35+ years ago . Also, the use of "modern" is rather vague as the Boeing 757 certainly feels "modern" (having been launched in 1982) but has been out of production since 2004, while the 747 started production in 1969 and is still being built. If someone wants to jump in to help define "modern", I'd take no offense. <Q> Just three data points: <S> The tail surfaces of the Pilatus PC-12 still use the venerable NACA 0012, even though a better alternative (from the Wortmann FX 71 L series) was proposed. <S> It did not help that the Wortmann airfoil is used on many small airplanes, has more lift and less drag and an abundance of data exists on it: <S> The (mainly British) engineers at Pilatus were too conservative to use anything newer than an airfoil from the 1920s. <S> Pilatus <S> PC-12 (picture source ). <S> The wing of the Dornier Seastar , designed by a group of old Dornier engineers in the early 1980s, used the same airfoils as the venerable Do-17 of the 1930s, namely the NACA 23012. <S> Later flight tests showed the need to add a leading edge droop on the outer wing, a modification that cost several knots in top speed and would have been entirely avoidable with better airfoils and/or the use of washout. <S> Dornier Seastar. <S> Picture by Rschider (own work). <S> The excellent Polish aerobatic glider <S> Swift S-1 <S> uses indeed a NACA 6-digit airfoil, the $64_1412$. <S> As Jerzy Makula explained to me, it gives excellent snap roll and spin control, and when flying the prototype, I could control the exit direction from a spin within ±15° with very little practice. <S> Jerzy simply took what had worked before . <S> Swift S-1. <S> Picture by TSRL <S> (own work). <S> Generally, small companies or experimental airplane builders still rely sometimes on the NACA series, but in general better alternatives exist. <S> Big companies use custom-made airfoils, helped by computer codes which model not only the two-dimensional flow around the isolated airfoil, but can optimize the specific wing section by including the influence of engine nacelles, pylons and the fuselage. <S> Well-designed wing roots do not use one single airfoil, but a three-dimensional shape which minimizes interference drag. <S> This is true even for glider companies. <S> While Wolf Lemke used his own creations for the early LS series of gliders on the basis of their good looks (and with good success), todays gliders are designed in the computer, helped by university departments which relish the chance to let students work on real-world designs. <A> For example, the Cessa uses either pure or modified NACA airfoils in most of its Cessna Citation jets, though newer models tend to use Cessna's own airfoils. <S> For example, the Citation V uses modified NACA 23014 airfoil at the root and modified NACA 23012 at the tip. <S> " Cessna uc-35a citation 560 ultra v arp " by Adrian Pingstone - Own work. <S> Licensed under Public Domain via Commons . <S> The recent ones, like the 750 Citation X uses Cessna's own Cessna 7500 airfoil. <S> Boeing, on the other hand has been mostly using its own airfoil designs from day one, though it has 'borrowed' ideas from NACA series (like supercritical design) On the military side, the F22 Raptor uses a modified NACA 6 series airfoil. <S> According to Public Domain Aeronautical Software F-22 uses a uncambered 64A section with 5.92 percent thickness at the root and 4.29 percent thickness at the tip <S> For a detailed list please see The Incomplete Guide to Airfoil Usage . <A> The Cessna 172R uses a modified NACA 2412 airfoil and has been in production since 1956 to the present. <S> This also substantiates the excellent points raised by aeroalias ( https://en.wikipedia.org/wiki/Cessna_172 ). <S> This airfoil guide also specifies the airfoils used for wing root and wing tip for a large range of aircraft and helicopters ( http://m-selig.ae.illinois.edu/ads/aircraft.html ). <S> From this airfoil guide, you can also check out any "modern" aircraft you are interested in and determine if the NACA airfoils or any other type of airfoils are used. <S> P.S. <S> I just saw that aeroalias also referenced the airfoil guide. <S> Do check it out, it's a fantastic resource.
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NACA airfoils are used still used in aircraft, though most of the airfoils used are modified in some way.
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Why do we call moving an aircraft on the ground "taxi"? We all know what "taxi" means to general public -- a car which carries you from A to B in exchange for your paying a fare. "Taxi" also means to drive an aircraft on the ground . Why do we call it that? What's the reason & history behind the term? <Q> This online etymological site suggests that an airplane moves slowly across the field in a similar fashion to how a taxi-cab driver would slowly make his way down a block looking for fares, and the term is borrowed from that behavior. <A> The verb, "to taxi," as it relates to a moving airplane on the ground, dates to about 1911. <S> The verb appears to be derived from the noun, "taxi," referring to a nearly flightless training aircraft that dates to about 1909. <S> Eventually, they started calling getting around on the ground (or water) "taxiing." <S> The expression started at Henri Farman's flight school outside Paris, and was later picked up by pilots at flight schools in England. <S> A "taxi" had shorter wings and a heavier body, so that it could not really take off and fly away at the hands of a new pilot, but a new pilot could get the feel of handling the aircraft and learn to take off and fly short distances, especially downhill along a slope. <S> See: http://esnpc.blogspot.com/2016/05/flight-school-taxis-history-and.html <A> I'll throw a thought in the mix although the term most likely pre-dates <S> this: When you are running a plane on the tarmac the "meter" is literally running since the engines are on. <S> Much like the meter that starts running when you get in a taxi cab. <S> There is no worse feeling than renting a plane for a nice day of flying and getting stuck in a departure line watching the Hobbs slowly tick on while you sit there hopelessly. <S> Interestingly the history of the word "taxi" as we use it for cars dates from the word taximeter <S> the device installed in taxicabs to measure fare. <S> Which comes from the french taxer-mètre. <S> The evolution may come from the fact that the ground operations of the aircraft are part of the ticket which you paid for. <S> (Its a long shot but its worth a thought)
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The word may allude to driving around like a taxicab, as others surmise, or it may relate to the fact that flight instructors gave rides to new students in the "taxi" airplane.
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Why is Denver International Airport runway 16R/34L rarely used? From watching planes land at DIA on Flightradar24, none seem to ever land on 16R (longest runway in the US at a length of 16,000 ft), but instead land on a runway 4,000 ft shorter such as runway 16L (12,000ft). So why do even large planes like the 747 not land on the longer runway to have an easier landing? <Q> KDEN has a lot of runways, so they have the option of not always using some of them. <S> As FreeMan pointed out , 12,000 feet is plenty for just about any aircraft flying in or out, even at 5,300 feet elevation. <S> Being such a long runway, it may also be good to leave it open so that no aircraft need to be moved in case an aircraft declaring emergency would need the extra length. <S> Runway use will depend on the wind and traffic, so depending on when you are observing, you may not often see conditions where it is used. <S> North flow: arrivals on 34L could interfere with runway 7/25, and for departures it is further from the terminal than 34R. TomMcW also points out potential noise abatement concerns. <S> South flow: departures on 16R could interfere with runway 7/25, and for arrivals it is further from the terminal than 16L. <S> Even with 17L/35R <S> currently closed it is not always necessary to use 16R/34L. 8/26 and 7/25 can be used for east/west departures and arrivals, and 17R/35L can be used as well. <S> Runway 16R/34L can still be used as a secondary runway though. <S> It can certainly be used as 16R for parallel approaches with 16L, or departures as 34L with approaches on 34R. To put things in perspective, Denver has more runways than both KLAX and KATL, which see more aircraft movements. <S> Also, while far from authoritative, the virtual Denver ARTCC lists 16R/34L as a secondary runway in all situations. <A> What time are you usually watching radar? <S> Just a guess, but the following paragraph from this document would suggest noise abatement procedures. <S> Runways 34L and 34R : Aircraft will be assigned headings of 355 to 010 degrees. <S> Intersection departures on Runway <S> 34L permitted if user has signed an agreement with the City and County of Denver regarding terms of use . <S> The City may request that FAA stop allowing intersection <S> departures if the City determines that use of the procedure is resulting in detrimental noise impacts <S> This map shows you might not want to buy a house off the north end of the runway! <A> Where the extra length becomes really valuable is takeoff during winter ops when the runways have enough snow on them that braking action (i.e. in the event of an aborted takeoff) is degraded, and the anti-ice systems on the aircraft are all running (reduces engine performance), and you have some really heavy aircraft. <S> At that point, given the high altitude at KDEN, then the extremely long runway DOES become more advantageous than the others -- especially for those heavy weight & performance limited aircraft. <S> But for landings on good weather days when the airport has 6 strips of concrete (actually 5 at the moment, as 17L/35R is closed for repairs for some length of time) to choose from, you simply don't need them all. <S> Departing on 16R probably won't happen, because it's such a long taxi from the terminals, but departing on 34L seems fairly common... <S> depending on where you're starting from, it's no more of a taxi than runway 8 or 25. <S> I've also landed (fairly recently, in fact) on 16R during good weather summer ops: arrivals from the west were getting 16R and arrivals from the east were getting 16L. <S> Departures were using 17R (not an ideal runway for arrivals anyway, given the taxi back north to the terminals), and the east/west runways were either being inspected or temporarily shut down so they could reverse the flow (i.e. switching from landing 26 to departing on 8, and/or landing on 7 to departing 25, or vice versa). <S> And I've landed on 16L enough times with traffic for the parallel 16R close by, that I don't think I agree with the premise of the question. <A> 16R/34L is normally used for departures only. <S> Having a long runway for departures ensures that even the largest aircraft can depart fully loaded. <S> I do see a couple of configurations utilizing that runway for arrivals, but it's always in VMC conditions when the airport is in a south configuration. <S> You can check the typical runway configurations for any major airport in the US on the FAA's OIS webpage. <S> ( http://www.fly.faa.gov/ois/ ). <S> On the left side of the page, click on East Directory or West Directory. <S> Expand the directory tree under the ARTCC (ZDV for Denver <S> , for example) desired and then click on the airport. <S> The resulting table will show you typical configurations and the number of aircraft arrivals per hour that can be accommodated under each configuration.
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Twelve thousand feet is a really long runway; during clear & dry conditions the extra four thousand feet of 16R isn't any added value.
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When does a flight require a copilot? I was wondering if there are regulations for when a flight requires both a pilot and copilot. I always assumed a copilot is required once civilian passengers are aboard, but when I recently was a passenger in South-African and South-American sight seeing flights, the pilot was always flying alone. Flights in europe however always had a pilot and copilot. Is this regulated by laws or can the pilot / airline company decide it on their own? <Q> A multi-crew aeroplane is one that requires a flight crew of at least two pilots. <S> One of them is the pilot-in-command (the captain) and the other is the co-pilot (or first officer). <S> All jet air transport aeroplanes and the vast majority of turbine powered air transport aircraft and business jet are multi-crew aeroplanes. <S> The definition in Annex 1 — Personnel Licensing states that it is: "an aircraft required to be operated with a co-pilot as specified in the flight manual or by the air operator certificate." <S> So the secondary answer is no <S> , it cannot be decided by a pilot or an operator, it is a statutory requirement. <A> There is no regulation to cover minimum crew when flying privately, other than as required by the airplane manual. <S> For commercial flights it gets a bit more complicated and the answer is, well, "it depends". <S> In EASA comercial flying the minimum crew compositon is defined here: EU OPS (965) <S> Subpart N Ops 1.940 Composition of flight crew (b) Minimum flight crew for operations under IFR or at night. <S> For operations under IFR or at night, an operator shall ensure that: for all turbo-propeller aeroplanes with a maximum approved passenger seating configuration of more than nine and for all turbo-jet aeroplanes, the minimum flight crew is two pilots; or aeroplanes other than those covered by subparagraph <S> (b)1 above are operated by a single pilot provided that the requirements of Appendix 2 to OPS 1.940 are satisfied. <S> If the requirements of Appendix 2 are not satisfied, the minimum flight crew is two pilots. <S> And then the much longer Appendix 2 stating: (a) Aeroplanes referred to in OPS 1.940(b)2 may be operated by a single pilot under IFR or at night when the following requirements are satisfied: <S> the operator shall include in the Operations Manual a pilot's conversion and recurrent training programme which includes the additional requirements for a single pilot operation; in particular, the cockpit procedures must include: (i) engine management and emergency handling; (ii) use of normal, abnormal and emergency checklist; (iii) <S> ATC communication; (iv) departure and approach procedures; (v) autopilot management; and (vi) use of simplified in-flight documentation; the recurrent checks required by OPS 1.965 shall be performed in the single-pilot role on the type or class of aeroplane in an environment representative of the operation; the pilot shall have a minimum of 50 hours flight time on the specific type or class of aeroplane under IFR of which 10 hours is as commander; and the minimum required recent experience for a pilot engaged in a single-pilot operation under IFR or at night shall be 5 IFR flights, including three instrument approaches, carried out during the preceding 90 days on the type or class of aeroplane in the single-pilot role. <S> This requirement may be replaced by an IFR instrument approach check on the type or class of aeroplane <S> (text is copy-pasted since getting a working link to a consolidated version of EU-OPS is a pain) <A> In the United States there are 3 basic situations that generally lead to an aircraft being flow by 2 (or more) crew: <S> The aircraft is categorized in the "air transport" class (eg commercial jets) <S> The maximum takeoff weight of the aircraft exceeds 12,500 pounds <S> The aircraft is so complex that the manufacturer recommends that it be flown by two pilots Note that some aircraft, like variants of the 747, require 3 people because there is a station for an engineer. <S> In the old days the FAA used to require jets to be flown by two people, but now if a jet can come in under 12,000 pounds they can get certified for solo flight. <S> There are a bunch of planes right now pegged at 12,500 and multiple manufacturers would like to go over that limit and still have them certified for solo flight, so there is some pressure on the FAA to relax the limit.
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A flight requires pilot & copilot when the aircraft being flown requires it.
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What are the limitations of the aerodynamics modelling used in flight simulators? I've asked around, and it seems all flight training programs use a combination of flight simulators and aircraft flights to train pilots. This works well for most pilots who fly airliners which don't spend much time in turbulent air or close to obstacles, and the flight simulator aerodynamics are very close to what is experienced in actual flight. My question is where do the flight simulator aerodynamics models breakdown? I was wondering this in relation to rough air flying skills, where the aircraft or helicopter flow field interacts with surrounding environment (like inside a convective storm or near obstacles like trees and buildings) I would imagine these are situations that are hard to model since it depends on accurately modelling the interactions, which are difficult to run quickly enough for running a flight simulator. Fixing this by only doing flight training seems dangerous, especially for newbie pilots since the margin for error is very slim. Personally, even though its more expensive than a flight simulator, a first person view drone would be a good intermediate step between the flight simulator and full scale training, with the response characteristics and control interface being the same as the full scale aircraft or helicopter. That said, I don't know where the flight simulator aerodynamics begin to diverge from what is actually is experienced in real life, so the drone might be completely unnecessary. I'd love to see how this problem is resolved now. <Q> Size matters here. <S> Big aircraft have more inertia and take much longer to respond, but can equal out small-scale turbulence better. <S> Your drone idea for training will not be representative of the big airplane at all. <S> Turbulence can be modeled quite faithfully - you just need to fly once through rough air, collect all the data and replay it in the simulator. <S> The changes due to different pilot responses can be added on top without much loss in accuracy against a real flight. <S> Where models for airliner crew training break down is when the linear range of aerodynamics is left. <S> Their post-stall and spin behavior is most likely not suitable for training, but that is not what they are designed for. <S> Military aircraft simulators can even model the post-stall regime well, but need a lot of aerodynamic data, and most of that data is from wind tunnel models and not from real flight test. <S> What the simulation does is to plug the actual values of angle of attack, angle of sideslip, airspeed, power level angle and control deflections into matrices of coefficients and calculate the result from linear addition. <S> That works well as long as the forces vary linearly of the flow angles, and correction factors will give you still good agreement with reality well into a stall. <S> The coefficients are a mixture of CFD , wind tunnel data and flight test data. <S> Gust loads can be modeled with Markov matrices which produce a realistic distribution of gust intensities, so even external, stochastic factors can be modeled faithfully. <S> I have less knowledge of helicopter simulators, and I would assume that flying near tall buildings can only be modeled in general terms, but not well enough to train a pilot for a specific location and weather condition. <A> There are two aspects to simulation error: the aerodynamic model error and less commonly known, integration algorithm numerical error. <S> Aerodynamic models tend to break down in the transonic and post stall regime of flight for two reasons: lack of data due to safety or cost, and poor predictability created by non-linear response in turbulent flow/shockwave formation. <S> That is, the risk to reward would prohibit the conduct of full post stall(spin) test program on a wide body airliner. <S> There is no justifiable reason to do so in relation to the aircraft's role or certification requirements. <S> Contrast this to a fighter jet that might require this. <S> Note that buffet can occur prestall. <S> Despite the difficulties in predicting post stall handling qualities using tools such a CFD analysis, it is possible to collect reasonable data in relation to handling characteristics with detailed and thorough flight test. <S> Simulators are usually hamstrung by model complexity and realtime computing power. <S> For that reason, integration algorithms are chosen to best suit the simulation application. <S> Airliner sims tend to use forward predictive algorithms such as Adams-Bashforth-Moulton predictors, as the flight envelope is limited to regions where strong linearity exists. <S> Conversely this algorithm would induce significant errors even if reasonable aerodynamic data existed in post stall, spinning flight. <S> Other algorithms do exist and are better suited for this application. <S> Brute force may also be an option. <S> Using a drone could be beneficial, however it would be difficult to accurately mimic moments of inertia characteristics, and post stall handling due to Reynolds effects. <S> Ok for generic simulation, but not ok when replicating larger scaled aircraft. <A> Full motion simulators have no problems reproducing turbulent flight effects: they don't need to compute turbulence in real time like in CFD, they just replay one of several pre-recorded wind gust variants, and the reaction of the simulator flight model on this pre-recording is just a matter of mechanical physics modelling. <S> That is - as long as variables such as angle of attack stay within normal flying bounds, and do not enter fully established stall territory. <S> That needs to be modelled in a different way, indeed like Peter says from wind tunnel data, combined (unfortunately) with data from flight recorders of crashed aircraft. <S> This links to a site describing full stall simulation addition, certified by FAA. <S> (I've long hesitated to link to it due to it being a commercial product <S> and I've done business with the manufacturer). <S> Some confusion is created by Xplane using real-time laminar CFD. <S> Turbulent real-time CFD has all kinds of challenges, amongst others the stability of the real-time loop like @busdrivingtupperware mentions. <S> Flight training simulators don't use real-time CFD for computing flight dynamics, because computers are not yet powerful enough. <S> Only a matter of time: code that used to run at 30 Hz on a super duper computer 25 years ago, now runs at 3000 Hz on a laptop. <S> And model stability is usually not a problem at high iteration rates.
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Buffet, ground effect, external turbulence, and wake turbulence can all be simulated with reasonable accuracy according to the requirements and complexity of the sim, which is dictated by the aircraft role.
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If engine rotation was in reverse would it result in some kind of thrust reverser? I mean if you rotated the propeller the other way would it result in reverse thrust. I wonder this because the propeller has to rotate in a certain direction to produce thrust, but would putting it in reverse cause a force to help stop the airplane? And does this system exist with planes that have propellers? <Q> The propellers are like airfoils. <S> Source: <S> www.quora.com <S> That being said, it is possible to obtain reverse thrust from propellers by setting a negative pitch , similar to the airfoil being flown upside down. <S> Source: 12charlie.com <A> Absolutely, but as others have said it would be a very inefficient brake. <S> It's much more effective to simply rotate (or "pitch") the blades into a beta (zero-thrust -or- "flat pitch") or into a negative-pitch (reverse-thrust) condition. <S> This is a common feature on virtually every turboprop engine and many large, powerful radial engines. <S> It seems to be an emerging feature for small piston aircraft, although it is still rare to see a small piston airplane with a reversing propeller. <S> They do exist though but they are mostly sea planes. <S> Looking at the picture that you provided, the silver dome thing from where the propeller blades sprout is the hub of the propeller. <S> The bases of blades "plug" into this hub and can rotate through a certain range dictated by a device called a "governor." <S> The pilot can adjust a propeller control (usually part of throttle or power lever) that tells the governor to rotate the blades forwards or backwards. <S> During take-off, the pilot pushes the power forward which tells the engine to speed up and tells the propellers to push A LOT of air backwards for thrust. <S> When the pilot pulls this engine lever all the way back (on the runway during landing), he's telling the propeller blades to rotate in their sockets and push air forward instead of backwards. <S> Passengers hear this happen on landing as a loud roar for a few seconds as the plane slows down on the runway. <S> It feels like the pilot slams on the brakes <S> but it's mostly the propeller blades reversing in their hub sockets and pushing air forward to slow the plane down. <S> You can also hear the pilots adjusting the propeller blade pitch to control taxi speed as you taxi around the airport but <S> this isn't as noticeable as the landing noise. <S> It's important to realize that the engine will ALWAYS spin the propeller in the same direction. <S> It does not stop and then spin another direction. <S> The only thing that changes is the "pitch" of the blades in their hub sockets. <S> Hope this helps. <A> The propeller spinning in reverse would be like flying a wing backwards... <S> it wouldn't be efficient, and it probably wouldn't accomplish much of anything. <S> (Ceiling fans CAN be spun backwards to generate a breeze in the opposite direction, but they aren't exactly sophisticated airfoils!) <S> Spinning an engine backwards doesn't happen because you'd have to stop and then reverse direction of a lot of mass --- way too much momentum to reverse the direction of rotation unless you took a long time to do so. <S> When props go into reverse thrust, the engine & propeller continue to spin in the same direction, but the angle of the blades is changed so that the thrust vector is now in the opposite direction. <S> That process CAN happen pretty quickly, so you have reasonably immediate reverse thrust available.
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Just as the airfoils do not produce useful lift if flown backwards, the propellers don't produce thrust if spun in opposite direction.
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Why are airliner cockpits not shielded from lasers? With the recent increase in laser incidents reported by pilots, why don't airliner manufacturers shield airliner cockpit glass from lasers? The Abrams tank is shielded, protecting the crew from lasers. Why could a similar process not be employed in airliners? <Q> One of the simplest ways to protect against lasers is by filtering it using glass of a particular color, <S> depending on the laser we are talking about red or green glass (and some other colors here and there as well). <S> Generally they look something like this Coating an airplane windshield in glass of this tint, or a green tint would potentially impair the pilots ability to properly view PAPI or VASI lights which require red/white or red/green differentiation. <S> It would also cause the pilot to perceive all lights (during a night landing) differently. <A> Cynicism ensues. <S> Because it costs money, there is no regulation requiring it and airline companies <S> probably do not feel it as being an issue because there still hasn't been a hull loss due to it (and thus do not look for it in the aircraft they buy). <S> It is said that aviation regulations are written in blood , so I am afraid that either we will see a hull loss somewhere, prompting EASA, FAA and similars to update the regulations, or we won't see shielded cockpits in the near future. <S> Note that I refer to "hull loss" for a reason, there have been already events leading to injuries . <A> In a laboratory environment, incidental exposure to lasers is prevented by wearing specialized glasses . <S> This has been suggested as a possible solution to laser attacks on pilots. <S> Most who point this out as a potential solution will, however, admit that it only works if you know the wavelength of the laser. <S> You could go inquire on a different SE if you want to know more about laser safety. <S> I would assume that if the FAA knew what the laser was they would also know who was operating it and stop them. <S> As such, goggles are a long shot as a solution. <S> A promising emerging technology is electrochromics. <S> In particular plasmonic polymer electrochromic materials could be installed either in a pair of goggles or in all cockpit windows. <S> This poses its own issue though. <S> The device would need to be automatic, since even milliseconds of exposure to some lasers is blinding. <S> Imagine a pilot is on short final and his auto-electrochromic-goggles suddenly decide to block all light. <S> Not good. <S> you could instead fit the material to the cockpit windows. <S> Then, in the case of a laser event, the pilot would need to react the same way as for unexpected IMC. <S> this would mean a G/A if on final but would be much favorable to blindness. <S> As an added benefit, once you've installed a laser weapon detector on the aircraft, you could give it the ability to trace the source of the laser beam to be relayed to law enforcement (or a targeting computer.) <S> At any rate, we are talking many millions in R&D and production costs. <S> finally, this issue could be addressed by synthetic vision systems . <S> If the pilot is flying on cameras he cannot be blinded. <S> It is possible that a laser could be used to damage a camera but this could be more easily guarded against and <S> I'm sure that synthetic vision will have many redundancies. <S> So if you are asking if you can walk into the store and buy a laser defeating device, probably not. <S> If you want to buy several different pairs of cheap laser goggles on the off chance they are the right wavelength, it's probably better than nothing. <S> At the moment, though, there is no comprehensive solution available. <S> If you encounter a laser attack, do not look at it . <S> Put your hand in front of your face and fly on instrument.
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Money aside there is a bit of a practical reason as well.
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How is thrust generated by a propeller? I get confused sometimes because I hear different theories of how propellers generate thrust. One is that the propeller pushes air back to provide thrust. Another is the blades generate lift creating a high pressure behind the blade pushing the aircraft forward. Is it just one of these true or is it both? For you guys its the same way of generating thrust, but to me its two ways thats my confusion. And why does a propeller need to generate lift if it just accelerates air backwards to provide thrust. That question is my main confusion. <Q> It's the same thing, it changes only the point of view, see Newton's third law : for each action there is an equal and opposite reaction, i.e. to create thrust, the engine has to push air backwards. <S> Pushing the air backwards means that the air is pushing you forward and this, in the reference system of the propeller blade, is lift. <A> The propeller pushes the air behind if you are viewing from the aircraft (or propeller). <S> The propeller generates lift by creating a high pressure if you are in a frame of reference out of the aircraft. <S> Both are equivalent and can be used to describe what is going on. <A> If you imagine one of the propeller blades as a wing it can help you understand. <S> It spins around, moving air over both sides of its blade. <S> It is producing thrust the SAME way a wing produces lift. <S> Airflow over the top surface, which is in front of the airplane, causes lower pressure. <S> That negative pressure sucks the airplane forward the same way negative pressure over a wing has the effect of lifting the plane. <S> Thinking of it this way also helps with understanding P-factor. <A> When I think of fluids and pressure gradients, I go back to Newton's first and second laws. <S> A fluid can only accelerate in the presence of a pressure gradient, and if there is a pressure gradient then there must be acceleration (ignoring gravity for the moment). <S> So your propeller accelerating air past it only occurs because the propeller induces a pressure gradient in the air (high pressure behind the propeller, low pressure in front), or the pressure gradient occurs because the propeller accelerates the air. <S> They are essentially one and the same fenomenon, either side of the equation F=MA.
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Both the methods you are describing are the same :
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Are ETOPS rated planes denoted by a placard or other indicator? A recent AA flight to Hawaii was not ETOPS rated . ( alternate article ) Apparently the failures that led to this mistake occurred on multiple levels, including the schedulers who scheduled this equipment, and the dispatcher who may have prepped the flight plan. My question is if the crew had a means and responsibility to know if the plane was ETOPS certified? Would there be a placard for similar indicator in the cockpit stating "ETOPS allowed" (or perhaps "No ETOPS allowed")? Are parts of the checklist different for ETOPS/non-ETOPS aircraft?Can the crew reasonably expect to fly whatever plane they're assigned without checking over every piece of the certification, maintenance, and dispatch? <Q> According to FAA §25.1535 Appendix K, The airplane flight manual must contain the following information applicable to the ETOPS type design approval: <S> (b) Required markings or placards. <S> (e) <S> This statement: “The type-design reliability and performance of this airplane-engine combination has been evaluated under 14 CFR 25.1535 and found suitable for (identify maximum approved diversion time) extended operations (ETOPS) when the configuration, maintenance, and procedures standard contained in (identify the CMP document) are met. <S> The actual maximum approved diversion time for this airplane may be less based on its most limiting system time capability. <S> This finding does not constitute operational approval to conduct ETOPS.” <S> It does not require any identification marking on the aircraft itself, though as @woakley5 noted above, a number of aircraft do have them identifying the aircraft as ETOPS certified, like below. <S> Source: <S> www.thaiflight.com <S> I'm not sure about if any indications are there in cockpit <S> (there are no regulatory requirements, till today that is), but won't be surprised if it is available (in some aircraft, at least). <S> The ETOPS do have some additional checks. <S> According to Appendix G to Part 135, (This) <S> This ETOPS maintenance program must include the following elements: (b) ETOPS pre-departure service check. <S> The certificate holder must develop a pre-departure check tailored to their specific operation. <S> (1) <S> The certificate holder must complete a pre-departure service check immediately before each ETOPS flight. <S> (2) <S> At a minimum, this check must: (i) <S> Verify the condition of all ETOPS Significant Systems; (ii) Verify the overall status of the airplane by reviewing applicable maintenance records; and (iii) <S> Include an interior and exterior inspection to include a determination of engine and APU oil levels and consumption rates. <S> I'm not sure how the AA Flight 31 Flight and ground crew missed these checks. <A> ETOPS aircraft usually will have an indication on the front nose gear doors like this picture. <S> but I have no image to back this up. <S> I am certain that the airlines dispatch computer system will have some sort of tag as to whether an aircraft is ETOPS rated. <A> DGCA India CAR Section 8 Series <S> C Part <S> I Para 5.1.2 <S> (h) states: " <S> A procedure is to be established, through cock-pit placard / external marking, to indicate to maintenance and flight crew EDTO status of the aeroplane"
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I believe that an indication is given in the cockpit also on some type of aircraft info placard
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Did Boeing build airliners other than the 7x7 series? What I mean by the 7x7 series is the 707, 717, 727, etc. I took this picture at the Pima Air and Space Museum in Tucson, Arizona. What type of aircraft is this? Was it an airliner? I know that no 7x7 series aircraft was that small, so were there other airliners made by Boeing besides the 7x7 series? <Q> Yes, Boeing built other airliners, with different numbering , although none of them were jet-powered. <S> Three iconic designs come to my mind right away, although there were others: The <S> Boeing 247 predated the DC-3 into service, and was a highly advanced twin-engine, monoplane cabin design. <S> It was a pioneering aircraft, introducing all-metal construction, a cantilever wing, and retractable landing gear. <S> It was later surpassed by the DC-3, as the 247's cabin was too small for serious airline service. <S> The Boeing 314 "Clipper" was a large four-engine flying-boat transport from just before World War II. <S> Not quite as pioneering as the 247D, it nonetheless was massive for its time and heavily influenced later large Boeing designs. <S> It was large, pressurized, and technologically advanced, but relatively unsuccessful in sales compared to contemporary designs like the Lockheed Constellation. <S> As others have mentioned, the aircraft in your question is a Sud Caravelle , which was designed to solve the same problem as the later Boeing 737: it was a shorter-range airliner meant for smaller routes. <S> You point out how much the Caravelle's nose looks like the Boeing 787, and you're right - but it is even more similar to the De Havilland Comet ; Sud licensed the design from De Havilland. <S> All photos from Wikipedia. <A> To start with that picture from Pima Air and Space Museum: <S> Caravelle VI-R - the world's first medium-range jet airliner (source: Wikipedia). <S> This particular airplane has nothing to do with Boeing. <S> I believe it's in the Museum due to the fact that it was the world's first medium-range airliner. <S> You can read all about it at https://en.wikipedia.org/wiki/Sud_Aviation_Caravelle . <S> To answer your question about whether or not Boeing had anything apart from the 700-series: it does. <S> Not to forget the purchase of MD. <S> A list of ALL airplanes under Boeing can be found at: https://en.wikipedia.org/wiki/Category:Boeing_aircraft . <A> There was also Boeing 720, a shorter, smaller version of the Boeing 707. <S> Wikipedia article here: https://en.wikipedia.org/wiki/Boeing_720 <A> The military aircraft follow the US DoD designations, like C-17 <S> Globemaster III, K-46 <S> Pegasus (which is a modified 767) etc. <S> The aircraft is a Sud Aviation SE 210 Caravelle , produced by the French firm Sud Aviation. <S> " <S> Finnair Caravelle Basle Airport - April 1976 " by Eduard Marmet - http://www.airliners.net/open.file/0101623/L/ <S> Transferred from en.wikipedia. <S> Licensed under CC BY-SA 3.0 via Commons . <S> It was the first short/medium-range jet airliner. <S> It first flew in 1955 and was operated till 2004, with around 282 numbers built.
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All the Boeing civil jet aircraft (which are the only ones under production/operation) are named in the 7x7 series. The Boeing 377 "Stratocruiser" was a post-World War II design based on the B-29 bomber, with a double-deck (double-bubble) fuselage and four piston engines. It is a Sud SE-210
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Is the "Bay Tour" flight path documented, or is it a more informal route? Are there similar flight paths for other cities? During my Private Pilot's Licence days out in San Francisco, we often flew a "Bay Tour": a sightseeing flight northbound from San Jose through SFO's Class B , over the city and Golden Gate Bridge, then east to Oakland and south to return to SJC. Local approach controllers were familiar with this route, and a pilot could file a flight plan for a Bay Tour with everyone knowing what he was talking about. In addition, the tower at SFO would often go out of their way to give aircraft on a Bay Tour a better view of A380's and 787's out of SFO. However, I can't find any official information on it. Is it a published procedure, or just something that everyone out there has come to know about? Do similar flight plans exist for other cities and if so, where can I find information on them? <Q> There certainly are similar routes - the Niagara Scenic Falls route , given in FAR 93.71 comes to mind. <S> ( FAR 93 has plenty of these, by the way .) <S> Comply with the following procedures when conducting flight over the area described in paragraph (a) of this section: <S> (1) Fly a clockwise pattern; (2) Do not proceed north of the Rainbow Bridge; (3) <S> Prior to joining the pattern, broadcast flight intentions on frequency <S> 122.05 Mhz, giving altitude and position, and monitor the frequency while in the pattern; (4) Use the Niagara Falls airport altimeter setting. <S> Contact Niagara Falls Airport Traffic Control Tower to obtain the current altimeter setting, to facilitate the exchange of traffic advisories/restrictions, and to reduce the risk of midair collisions between aircraft operating in the vicinity of the Falls. <S> If the Control Tower is closed, use the appropriate Automatic Terminal Information Service (ATIS) Frequency; (5) Do not exceed 130 knots; <S> (6) Anticipate heavy congestion of VFR traffic at or above 3,500 feet MSL; and (7) Use caution to avoid high-speed civil and military aircraft transiting the area to or from Niagara Falls Airport. <A> As a Bay Area pilot, I've wondered this too. <S> Moreover, it seems there isn't just one "Bay Tour". <S> Instead, I think that phrase generally tells the controllers that you're on a sightseeing flight rather than simply trying to get from point A to point B. <A> There is not one official "Bay Tour" flight route. <S> However, there are general guidelines to follow. <S> This local flight instructor's site explains this and offers suggestions of where you can get a map. <S> Here is a flight briefing for one possible route . <S> In general, there are VFR Flyway Planning <S> Charts <S> that you can use in certain areas of the country. <S> San Francisco has one of these . <S> Flyway Planning Charts depict <S> flight paths and altitudes recommended for use to by-pass areas heavily traversed by large turbine-powered aircraft. <S> Ground references on these charts provide a guide for visual orientation. <S> VFR Flyway Planning charts are designed for use in conjunction with TACs and are not to be used for navigation. <S> Example section of a VFR Flyway Chart:
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It appears to be an unofficial but widely-understood local custom , similar to the not-always-charted VFR reporting points commonly in use at many local airports.
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Why is Concorde no longer in service? The crash of the concorde resulted in many deaths, but the crash was never caused by the concorde but by a plane that took off before it. Also airliners like the Boeing 737,747,and 777 have had accidents resulting in all deaths of the passengers and crew and was caused by the airplane, but are still in service today, so why are those airplanes still in service after the accidents and the concorde not in service after its accident that wasn't even caused by the concorde? <Q> The crash was only one of the (albeit an important) reason for the grounding of Concorde. <S> Actually, the aircraft was retired around three years after the crash. <S> The main reason was that not enough people were flying it to keep it profitable. <S> The Concorde as a technological marvel, but it had a number of disadvantages: <S> The aircraft was costly- <S> The program cost over $3B and produced 20 aircraft, of which 14 were used in commercial service. <S> Maintenance costs- <S> The small number of aircraft and technological sophistication meant that the cost of spares was high and options limited. <S> Operating costs- <S> The Concorde consumed nearly three times per passenger fuel when compared to the Boeing 747-100. <S> Still, the aircraft made operational profit due to the high cost of tickets. <S> Recession- <S> While announcing the retirement, British Airways cited commercial reasons, with passenger revenue falling steadily against a backdrop of rising maintenance costs for the aircraft. <A> This podcast covers the topic pretty closely and is a great interview with one of the old pilots of the Concorde. <S> From his accounts the Air France Concorde crash was the last straw that lead to its shut down but was not the only factor. <S> The Concorde itself was, in its prime, a very profitable airplane and made BA and Air France loads of money when they flew it. <S> However the plane was extremely costly to operate. <S> Due to its supersonic nature the air frame saw a great deal more fatigue than a subsonic plane and it became not only expensive but time consuming to maintain the aircraft. <S> All the while regular jets got bigger while the Concorde did not. <S> Consider that the plane had a 100 person capacity while jumbos kept getting bigger. <S> In turn the smaller margins jumbos made per person were beginning to catch up to that of Concorde (for what it's worth <S> it's a pretty old plane). <S> Much of this lead to its demise. <S> Along with that, the down turn in air travel after 2001 lead to a big passenger slump which did not help keep the very expensive and rapidly aging plane in the air. <S> On an interesting (and similar side note) check out the Boeing SST which was a similar plane that never made it to production for similar reasons. <A> Mainly for three reasons: <S> Increased maintenance costs. <S> Low number of passengers after the accident of July 25, 2000. <S> The decline in air travel following the September 11, 2001.
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After 9/11 attacks exacerbated the global downturn in aviation due to recession, there was an enormous drop in first class air travel, on which Concorde was dependent on.
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What is a canard? While browsing this Stack Exchange, I regularly come across mentions of canards . I am not familiar with this term, and Google only gives information about ducks when I search for "canard". So, what is a canard? <Q> In aeronautics, a canard is a small wing that is located in front of the main wing of the aircraft. <S> This is similar to the elevator, but is located in front of the wing, instead of behind it. <S> The configuration,and in some cases, the aircraft itself may be called a canard. <S> From Merriam- Webster dictionary: an airplane with horizontal stabilizing and control surfaces in front of supporting surfaces also : a small airfoil in front of the wing of an aircraft that can increase the aircraft's performance <S> The reason why it is called a canard (French for duck) has to do with the wing location. <S> From Flying Magazine Jan 1982 : <S> This is called a canard, from the French word for duck; with its long neck, a duck appears to have set its wing towards the rear of the fuselage. <S> The photo below shows the canard in front of the main wing of SU 30 MKI . <S> Source: <S> defence.pk <S> The canards have been used in aircraft for a long time. <S> infact, the first aircraft, the Wright Flyer was a canard biplane. <S> " <S> Kitty hawk gross " by Attributed to Wilbur Wright (1867–1912) and/or Orville Wright (1871–1948). <S> Most likely taken by Orville Wright. <S> - File: <S> Wilbur Wright after unsuccessful flight <S> trial.jpg (itself from Library of Congress). <S> Licensed under Public Domain via Commons . <S> The period from WWI to WWII saw the 'conventional' configuration with horizontal tail dominate the aircraft design. <S> The canard configuration was not revived until the jet age by the European manufacturers, starting with Saab Viggen . <S> " <S> Saab AJS-37 Viggen 37098 52 <S> (SE-DXN) (9256079273) " <S> by Alan Wilson - Saab AJS-37 Viggen '37098/ 52' <S> (SE-DXN)Uploaded by High Contrast . <S> Licensed under CC BY-SA 2.0 via Commons . <S> The canard configuration is used in almost all European fighter Designs, as they have more or less exclusively turned towards tailless delta configurations. <S> Also, a number of super-maneuverable aircraft use canards as the control authority is larger for unstable canard aircraft at high $C_{L}$ than for unstable aft-tail designs. <S> The photo below shows the canards in F-15 ACTIVE Source: tom-clancys-hawx.wikia.com <A> Your Google search has apparently had too much wine and can only speak French :) <S> The relevant dictionary definition is: Aeronautics. <S> an airplane that has its horizontal stabilizer and elevators located forward of the wing. <S> Also called canard wing. <S> One of two small lifting wings located in front of the main wings. <S> A picture, however, is worth all of dictionary.com: <A> Also, the term canard configuration is used to distinguish it from a conventional configuration. <S> The term comes indeed from the French word for ducks, since they also have a relatively rear wing location when they stretch out their necks in flight. <S> White duck in flight <S> (picture source ). <S> The airplanes built by the Wright Brothers were canards, as was the first all-metal airplane : <S> (picture source ) <S> Reissner Ente, the first all-metal airplane, in flight (picture source ) <S> A more modern example is the Speed Canard , which even uses this term in its name. <S> Flying direction is to the right: <S> (picture source ) <A> The expression is shorthand for canard wing(s), small lifting surfaces mounted in front of the main wings on certain planes. <S> Incidentally, many (all?) <S> current European fighter jets have this configuration, and you may therefore occasionally see references to "Euro-canards" as a general group of European-developed fighter jets, such as Eurofighter Typhoon , SAAB <S> Gripen and Dassault Rafale . <S> The picture below shows the configuration clearly on a SAAB Gripen ( Image source ).
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A canard can mean both, the horizontal control surface placed at the forward end of an airplane and the whole airplane of this configuration itself.
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Does cargo heat failure require a diversion? What about if there are live animals in cargo? There was a story in the news recently that an Air Canada 787-8, enroute from Tel Aviv (TLV) to Toronto (YYZ), diverted to Frankfurt (FRA) when the pilots discovered a problem with the cargo heat. There was a live dog in the cargo hold, and the diversion potentially saved it from freezing to death. The narrative has been that the pilots diverted specifically in order to save the dog. But I am wondering whether a cargo heat malfunction might require a diversion, as a matter of standard operating procedure, regardless of whether live animals are on board. After all, even if there are no live animals, there might be other valuable temperature-sensitive cargo. In general, according to airline policies or procedures, under what circumstances would cargo heat failure warrant a diversion? Any major airline would be of interest; if you want a specific one, let's say Air Canada. <Q> Does cargo heat failure require diversion? <S> It depends on the cargo being carried. <S> For your question about pets <S> , then yes. <S> Council Regulation (EC) <S> No 1/2005 regulates the protection of animals during transport in the EU, which itself is in accordance to IATA Live Animals Regulations. <S> The guidelines based on that EU regulation say: Commanders, and loadmasters and aircrew under their authority must ensure that the aircraft and equipment are suitable for carriage of the animals concerned in the manner intended. <S> They must ensure that the animals are loaded, carried and unloaded in a way which will protect their welfare. <S> In particular they must ensure that the animals are accommodated in accordance with the IATA LAR, and that an appropriate environment of air quality and quantity, temperature and pressure is maintained whilst the animals are on the aircraft. <S> The ability to ventilate and regulate the temperature of an aircraft belly hold varies considerably. <S> The arrangements vary between individual aircraft depending on the make and type, the compartment, and whether or not ‘standard’ or ‘special’ specifications have been fitted. <S> It is therefore essential that the aircraft operator, who should know the individual features of each of its aircraft, is satisfied that the belly hold to be used <S> can be sufficiently ventilated and maintained at a satisfactory temperature during all stages of the proposed flight. <S> This assessment should take into account the species, number, weight and size, and volume of the animals to be carried, and the heat and moisture that they will produce. <S> Even the Minimum Equipment List of aircraft takes that into consideration. <S> For example, the aircraft can be dispatched with an inoperative cargo heater or ventilation fan, but not if there's an animal in that respective cargo hold. <S> All that confirms the pilot's action in the story you mention. <A> Company rules normally dictate diversion/abort rules. <S> For most aircraft there are not temperature requirements for areas of the plane, except for the cockpit and avionics bays. <S> They may require non-polar temperatures to operate correctly, and may require cooling for power equipment like radar transmitters. <S> Obviously, if one is a carrier like FedEx and transporting live animals, it is different than transporting machined parts. <S> A manifest for cargo will describe handling precautions, including issues with the cargo impacting the operation of the aircraft. <S> (eg. chemicals, radioactive isotopes, strong magnets, etc.) <S> Also, normally bleed air is used to heat cargo areas. <S> Bleed air takes energy, and is not "free" so normally the areas are not heated to temps like 20C. <S> Generally, if one is flying generic freight, good operating practice avoids having a cargo area which is below 0C. <S> Again, company rules will be where guidance is for a particular flight. <A> Exclusive Cargo airlines are expected to take extreme care of temperature sensitive cargo (pharmaceutical products, food, animals, etc.). <S> Modern cargo aircraft have complex air-conditioning systems not less sophisticated than passenger compartments and special briefing to operating pilots. <S> Cargo airline company procedures will provide clear guidelines to pilots under what circumstances would cargo heat failure warrant a diversion. <S> This will depend on the ethical nature /and/ <S> cost of damage due to damaged cargo. <S> (Example: Is the cargo in question, thousands of a day old chicks /or/ a few expensive racing horses)
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Other cargo being carried at the same time will also need to be taken into account.
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What equipment is used by Boeing to convert the F-16 into an unmanned aircraft (QF-16)? How exactly does this equipment convert the F-16 into an unmanned aircraft? Is it possible to use this equipment on any other fighter (like the F/A-18 Hornet for example) in order to convert it into an unmanned aircraft? <Q> THE USAF has had a program for converting manned aircraft into unmanned ones for decades. <S> The aircraft used so far include, <S> QF- 104 (from F-104 <S> Starfighter) <S> QF- 102 (from F-102 <S> Delta Dagger) <S> QF- 100 (from F-100 <S> Super Sabre) <S> QF- 106 (from F-106 Delta Dart) <S> QF- 4 (from F-4 Phantom II) <S> Note that both aircraft are piloted. <S> According to fencecheck.com, (QF-4s are)..almost always flown with a pilot aboard, unless a weapons launch will occur. <S> Usually he does not touch the controls but stands ready to take over if ground control is lost or the aircraft departs. <S> The pilots fly the aircraft themselves on chase missions and to maintain proficiency. <S> The QF-16 replaces the QF-4. <S> The conversion of (retired) F-16 to QF-16 involves the following steps : Removal of non essential items like the Vulcan cannon and the radar (in previous versions like QF-4, the radar was simply deactivated) Modification of the FCS (Flight Control System) so that both manned and unmanned flights are possible (previous drones were remotely flown) Installation of Flight termination system to destroy drone in case of flight path deviation, which results in this: Source: <S> f-16.net Installation of onboard telemetry systems to control the aircraft from the ground. <S> Installation of a scoring system to measure the missile success rate. <S> This is required as most of the missiles are launched with dummy warheads or the flight path is programmed to evade the missiles, so that the costly aircraft could be reused. <S> Only in a few cases are lethal missiles used. <S> The self protection suite (flares, chaffs etc.) are usually left on the aircraft to provide a realistic engagement scenario. <S> New paint job :), which looks like this: Source: <S> www.wired.com <S> It is possible to convert (any) other aircraft into drones. <S> For fly by wire aircraft like F/A-18, only the software portion will change, but it is a minor thing. <A> I doubt it would be possible to give you a detailed and specific answer to this question (with a components list and such <S> ) - the US government and military contractors generally don't divulge complete plans and schematics for aircraft/modifications in active service. <S> In basic theory however, I can tell you that the F-16 is a fly-by-wire aircraft . <S> Much like an Airbus aircraft, all flight controls are actually manipulated by the on-board computers, and the pilot is just telling the computer what they would like the plane to do. <S> Because it's a fly-by-wire aircraft all that's really needed to turn it into an unmanned aircraft is to change the source of the "pilot input" from a control stick and throttle handle to a radio receiver that's getting commands from the ground, effectively turning it into the world's most expensive RC aircraft. <S> Presumably there are also failsafes in the event the control uplink is lost, and at least some basic security protocols to prevent someone else from sending commands to the system. <S> In the case of the QF-16 (which is designed to serve as a target drone for aerial combat training) not much more needs to go into the design - it doesn't need extensive fire control capability for example. <S> It also gets some other features added which are designed to aid in scoring training exercises (determining the accuracy of the aircraft attacking the target drone). <S> If it were to go into a combat role it would require those features as well, and probably substantially more work in securing the control <S> uplink so an enemy can't disrupt (or worse, hijack) control of the aircraft. <S> As to what would have to go into another aircraft to make it unmanned, that depends on the aircraft. <S> Obviously the control uplink has to be installed so you can communicate with it from the ground. <S> Control system modifications may be required as well, particularly if the aircraft is not "fly-by-wire" computer-controlled (the QF-4, which was the QF-16's immediate predecessor based on the F-4 phantom, likely required servos to operate the throttle and other flight controls). <A> Check out this article from Flightglobal on the Loyal Wingman program: https://www.flightglobal.com/news/articles/pentagon-touts-loyal-wingman-for-combat-jets-423682/ <S> You turned your aging manned combat platforms into an unmanned expanded magazine for your manned platforms. <S> The QF-16 costs just over $1,000,000 for the conversion. <S> Given the size of legacy F-16 and F/A-18 fleets this seems like a practical solution for countries with constrained military budgets.
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It looks like Boeing and Lockheed Martin are in a position to provide a drop-in solution whereby you swap out a couple of LRUs (Line-Replaceable Units) and bang!
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What is the meaning of “American 755, turn right, heading 320"? I am studying a text entitled Unmanned Aircraft Systems . How can we simplify the instruction in quotes so that it is more understandable and can be understood by a nontechnical. Please note I am not seeking to know all technical jargon of routing aircraft, rather to get what a pilot is told with this instruction to do. Ideally, the communication process includes three parts: the initial call, readback, and hearback. For example, an ATCO would issue an instruction “American 755, turn right, heading 320.” Pilots onboard the aircraft would respond, or readback the message “Right, heading 320, American 755.” <Q> American 755, turn right, heading 320. <S> Aviation phraseology is direct, specific, and concise. <S> The three items here: <S> The controller is instructing the aircraft identified as American 755 to make a right turn such that they maintain a heading (direction) of 320 degrees (5 degrees north of north-west) . <S> Though you may not be interested right now, at some level you might have to get technical, as communication involves defining terms :) <S> In case you are interested, for references and further reading <S> see this page from the FAA . <S> Especially of note: <S> Pilot/Controller Glossary - contains definitions for radio communications. <S> Aeronautical Information Manual - contains instructions for pilots. <S> JO 7110.65 - (more technical) <S> the handbook for controllers. <S> Everything they say should be in there. <A> It is quite simple if you look into the answer linked by Steve V. to understand what the headings are. <S> Here is a simple example: aircraft flies at 290. <S> Controller instructs right turn to 320. <S> The image below shows how should the aircraft turn. <S> Heading is on top and on the orange "bug". <S> (Needle shows track but you can safely ignore it for this example). <S> But here is a subtle case: if the aircraft flies on a heading of let's say 030 and the crew is instructed to turn right heading 320, then they should perform a 290 degrees turn to the right to meet heading 320. <S> This might not be obvious at first sight as it seems awkward, but it's critical in air traffic control. <S> Notes for the images: <S> Compass is set to show "head up" ie the current heading of the aircraft on top and not "north up". <S> Also the compass rose for brevity <S> does not depict degrees but tens of degrees. <S> So "15" stands for 150 degrees. <S> Images source: own work. <A> <A> 'American' is the callsign of American Airlines and '755' is the flight number. <S> Here the plane is being intructed by the Air Traffic Control to make a right turn until they are pointing towards the 320 degrees mark on their heading indicator or the compass.
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The basic answer is that the controller is instructing American 755 to turn right in order to point the airplane a direction which is 320 degrees clockwise from due north (basically northwest) For the specifics of what a "heading" is, see this excellent answer (with pictures!) .
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How does a coaxial rotor helicopter achieve yaw? Without a tail rotor, how does a coaxial rotor helicopter achieve yaw control? Does a coax have to bank in order to turn? The link goes to wikipedia's article, and down a ways it says: Rotational maneuvering, yaw control, is accomplished by increasing the collective pitch of one rotor and decreasing the collective pitch on the other. This causes a controlled dissymmetry of torque. However, I cannot understand what it's saying. AFAIK both rotors always spin at the same RPM because the mechanical engine links are built that way and it's set in stone (correct me if I'm wrong). So I can't see how one rotor makes more torque. EDIT: related, is this kind of yaw, however it's achieved, slower or faster than yawing in a conventional tail helicopter? <Q> In a conventional helicopter the lift generated by the rotor is controlled by the collective pitch. <S> Raising the collective pitch increases the Angle of Attack of the the rotor blades and consequently the lift, and inevitably increases drag. <S> The drag is overcome by increasing the torque from the engine. <S> Vertical movement is achieved by balancing the collective pitch against the torque while maintaining a relatively constant rotor speed . <S> The torque from the engine pushing the rotor one way results in a tendency of the fuselage to rotate in the opposite direction. <S> This is conventionally countered by a tail rotor or other similar device, and varying the force generated by this rotor controls the yaw. <S> So far, so good. <S> In a helicopter with coaxial rotors there is no tail rotor, but the torque issue remains. <S> Here, it's resolved by applying equal but opposite torque to each rotor. <S> Lift overall is controlled by changing the Angle of Attack of both rotors. <S> If the same inputs are applied to both rotors then the torque remains balanced. <S> However, the Angle of Attack of one rotor can be increased while that Angle of Attack of the second is decreased, leaving lift overall unchanged. <S> This will increase the drag on the first rotor, and hence the torque required to maintain rotor speed. <S> Simultaneously, the lift, drag and torque on the second rotor has been reduced, producing an imbalance in the direction of torque between the two rotors, and a consequent yaw moment around the axis of rotation. <S> All this can be achieved without a significant change in rotor speed. <S> In fact, the exact rotor speed doesn't play a part in yaw control. <A> In addition to @Airsick's excellent answer, some coaxial helicopters, like the Gyrodyne Rotorcycle , use tip brakes to achieve yaw authority. <S> Below are a couple examples of tip brakes, found at this website <S> A tip brake is a drag-inducing device on the end of the blade, that can be extended or retracted to increase or decrease drag. <S> To yaw in one direction, the tip brakes would be extended on one set of blades, but not the other, generating a net torque due to increased drag in that rotor. <A> By the same token, reducing the collective pitch reduces the amount of torque it had been inducing. <S> This is evident in a single rotor helicopter with its need for an anti-torque rotor. <S> So in a coaxial rotor system, with the two main rotor blades counter rotating, increasing the collective pitch of the top rotors (thus increasing its torque effect on the main rotor shaft) AND reducing the collective pitch of the bottom rotors (thus decreasing its torque effect on the main rotor shaft) will make the aircraft yaw in the opposite direction that the top rotors are rotating. <S> So let's say that as viewed from the top of a coaxial helicopter, the top rotors rotate clockwise and the bottom rotors rotate counter-clockwise. <S> When left pedal is applied (to point the helicopter's nose to the left or yaw counter-clockwise) <S> the collective pitch for the top rotors is increased (increasing the torque counter-clockwise) while the opposite is done to the lower rotors (thus decreasing the clockwise torque). <S> I hope this helps! <A> In simple terms, you increase the drag on the rotors going one way, and reduce it on the rotors going the other way. <S> Normally you increase the pitch of one rotor (meaning more lift and more drag), and decrease it on the other (meaning less lift and less drag). <S> The lift balances out, but the difference in drag causes yaw.
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When you increase the collective pitch of a rotor blade, it produces torque thus inducing a yaw in the opposite direction of the aircraft.
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Can radar detect a small flying device with MEMS microengines? I have seen some MEMS micro engines and some micro turbines and I would guess they can be attached to some payload to fly. Is it possible for commercial/military radars to detect those micro flying devices? <Q> Obviously the MEMS engine itself is not going to be detected: they're only a few millimetres across. <S> The question entirely depends on what you attach it to. <S> Conventional radars have trouble detecting UAVs less than a couple of metres long, and replacing their power plants with micro turbines won't change that. <S> My neighbours at Aveillant already have a holographic radar system that can detect smaller targets such as UAVs more accurately. <S> Again, changing the power plant technology won't change that. <S> Micro-turbines are not intended to replace propulsion systems, but to replace batteries, allowing them to use denser hydrogen, methane, or methanol fuel. <S> As far as I've been able to find, they don't produce break-even power yet, but it's envisioned that they will become commercially relevant once they can produce more than 10 W (about .01 hp), in a few years' time. <S> For comparison, a current, small, military UAV might generate tens of horsepower, and some experimental super-lightweight UAVs need as little as 5 hp, but with no payload or cargo. <S> TL;DR: <S> (a) <S> MEMS turbines aren't going to be relevant for UAVs for some years, and they'll have to be much bigger than they are now; <S> (b) replacing the power plant won't make much difference to the radar signature. <A> Radar detection depends on the scattering of radar waves on objects. <S> If we use the common X-band (8-12 GHz frequency) as an example, the wavelength $\lambda$ of the radar waves is in the order of 3 cm. <S> Now the size of the target comes into play, expressed as a ratio α, defined as $$ <S> \alpha = <S> \frac{\pi\cdot D}{\lambda}$$with $D$ the diameter of the object to be detected. <S> α ≪ 1: <S> Rayleigh scattering (small particle compared to wavelength of light) <S> α ≈ 1: <S> Mie scattering (particle about the same size as wavelength of light, valid only for spheres) α ≫ 1: geometric scattering (particle much larger than wavelength of light). <S> Only for large α you will get a return signal which can be used for detection. <S> Then we speak no longer of scattering, but of reflection . <S> If your MEMS engine is just a few mm across and attached to a plastic airframe (which should be transparent to radar waves), it should be impossible to detect with conventional radars. <S> Since the atmosphere is rather opaque for microwave radiation above 20 GHz, infrared or optical detectors will be needed to detect such an aircraft. <S> Also, the software driving the radar display is an important factor. <A> It does not matter what type of engine is used; if the Radar is powerful enough and the flying object is near enough (making allowances for any low observable design) i.e. based on the Radar Cross Section, it will be detected by the Radar. <S> In case of small flying objects, the main problem is not in detection (Radars usually pick up bugs and such) but in recognizing the object in background clutter. <S> In this case, the military Radars have an edge as they are more powerful and are optimized for detection of small targets in ground clutter.
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Common aviation radars will filter out small, slow-moving objects , so even a metallic or carbon-composite airframe several centimeters across will not be detected.
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Are commercial aircraft required to have the model number painted on them? On a lot of aircraft, the model number / aircraft name is clearly marked somewhere on the fuselage, e.g. "Airbus A320". Is there any rule or mandate, that all aircraft must bear the model number at some designated place on its body, to help others identify them? <Q> Every aircraft I have flown had a data plate mounted somewhere in the outside, showing the make, model, serial number, and the year of manufacture. <S> You probably can't see it unless you're 3 feet away, but it's there. <S> The relevant regulation in the US is: <S> § 45.11 Marking of products. <S> (a) Aircraft. <S> A manufacturer of aircraftcovered under § 21.182 of this chapter must mark each aircraft byattaching a fireproof identification plate that— (1) Includes theinformation specified in § 45.13 using an approved method of fireproofmarking; (2) Must be secured in such a manner that it will not likelybe defaced or removed during normal service, or lost or destroyed inan accident; and (3) <S> Except as provided in paragraphs (d) through (h)of this section, must be secured to the aircraft fuselage exterior sothat it is legible to a person on the ground, and must be eitheradjacent to and aft of the rear-most entrance door or on the fuselagesurface near the tail surfaces. <S> and § 45.13 Identification data. <S> (a) <S> The identification required by § 45.11 (a) through (c) mustinclude the following information: (1) Builder's name. <S> (2) Model designation. <S> (3) Builder's serial number. <S> (4) Type certificate number, if any. <S> (5) Production certificate number, if any. <S> Here's an example from a Stinson 108 : <A> No. <S> It's easy enough to find photographs online of aircraft that don't have the model number written on them in an obvious way. <A> FAA AC-45-4 act is regulating that. <S> Each airplane made after that year must have nameplate attach to the fuselage.
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If there were any regulatory requirement to have the model number painted on the plane for recognition purposes, it would have to be obviously visible or there'd be no point.
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Why are most weapons in AC-130 on the left-hand side? Lockheed AC-130 gunship is a heavily armed ground-attack aircraft variant of the C-130 Hercules transporter. The plane is manufactured by Lockheed and converted by Boeing. Why are most of the guns in AC-130 installed on the left-hand side (but not right)? Picture Source <Q> It is not designed to strafe, it is designed to loiter over a target or, to apply suppression fire or support fire for a sustained period of time. <S> It often circles a target area and a counter clockwise orbit (circling to the left) <S> makes sense since the captain sits on the left and can keep the area in view at all times. <S> Therefore, the weapons are mounted on the left. <A> It follows that there are more, more accessible, pre-existing holes on that side of the fuselage. <A> The AC-130 is the evolution of modified C-47s from the Vietnam War. <S> At the time, a small group of USAF personnel explored arming cargo aircraft with side mounted weapons in order to bring greater firepower to bear for ground support. <S> In particular, they wanted to solve the problem of strafing , where aircraft can only bring their firepower to bear for a short period of time, and often without a great deal of time to aim. <S> Captain Ron Terry was in charge of the initial effort which adapted these planes to gunship use in Vietnam in 1964: <S> Terry arrived at Bien Hoa Air Base near Saigon on December l. <S> After the miniguns arrived the following week, he selected two test crews of six flight members and an interpreter, and two C-47s with relatively low flight time from the 1st Air Commando Squadron. <S> The planes were modified to accept three minigun pods along the port side (two in the last two windows and one in the cargo door); an MK 20 Mod 4 gunsight mounted in the left cockpit window; and a selective trigger placed on the pilot’s control to fire one or all the guns. <S> source <S> Since AC-130s are now specially converted from C-130s by Boeing, and they use modern targeting sensors (IR and visual cameras), and that windows/doors are no longer large enough for the custom mounts they use to install the weapons <S> , there's probably no specific reason for keeping them on the left except that it's the status quo. <A> All the guns are on the left side. <S> The method of targeting is that the aircraft circles counterclockwise so that the left side is pointing downward. <S> Thus all the guns can be brought to bear on the target (unlike an old frigate with guns on both sides) and the pilot can see the target as he circles.
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Often weapons are mounted in door apertures so that additional holes do not have to be introduced into the fuselage. Traditionally, the doors most used on an aircraft (including civilian ones) are on the left (captain's) side.
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How do drones overcome latency? The US Military's use of drones has become commonplace, and widely known at this point. Although these vehicles are operated from nearby bases during these attacks, it seems like the latency (time of transmission) would be problematic as far as flying goes. Are these vehicles typically flown 100% by autopilot, where there's very little real-time reaction? <Q> There are multiple ways to fly and control Unmanned Aerial Vehicles (UAV), or drones, for e.g. the Predator. <S> Source: science.howstuffworks.com <S> Most of the UAVs, like Predator can perform (i.e. fly in) some simple missions (like reconnaissance) autonomously. <S> In case a geostationary satellite is used for communication with the UAV, the latency is around 300 ms <S> (The electromagnetic waves have to travel ~70000 km). <S> In case of other delays (like equipment etc.) <S> this will not be greater than 500 ms or around half a second. <S> This is not significant in case of slow moving systems like Predator (they are not dog-fighting, after all) and the 'pilot' can effectively control the aircraft. <S> The only situation where this is a problem is when the UAV is taking off/landing and in this case, the control is handed over to local LoS operators. <S> According to the telegraph , But the two-second delay between a pilot moving a joystick in Nevada and an aircraft responding in Afghanistan is enough to cause a crash during take-off and landing. <S> Crews in Afghanistan control 'launch and recovery’ through direct contact with antennae on the aircraft. <S> Half an hour after take-off, control of the Reaper is handed to a crew in Nevada; half an hour before landing, it returns to the crews on the ground in Kandahar. <S> Note that the RAF also does things the same way. <S> According to the report on formation of 'drone' squadron' at RAF Waddington , Although the personnel will be permanently based at RAF Waddington, some will go to Afghanistan to control the take-off and landing of the drones locally. <A> The aerodynamic surfaces of a drone are controlled by computers, not by humans. <S> When a human makes a control input this input is broadcast to the UAV, and the computers on the UAV make the appropriate changes to the flight surfaces to carry that input out. <S> It's not direct control of the drone by humans via radio. <A> Source: Acquaintances who worked on avionic software and hardware development <S> Latency matters for anything mechanical that flies ! <S> On-board equipments are developed to handle sub-second interactions. <S> Any interaction from ground is assumed to take many 100s of milliseconds to reach the flight (anything that flies). <S> To minimize the impact of latency, a series of information keeps flowing thereby converting latency problem into throughput problem. <S> This does not reduce latency but pre-loads onboard systems with accurate data to anticipate next 500 mS <S> or so. <S> To understand the solutions for latency, look for 2 businesses that are latency sensitive - gaming and high frequency trading. <S> To put things in perspective, in HFT, a market event is detected by software and it generates an order and sends it - all under 1 micro-sec. <S> Further latencies in network stack is not measured here <S> but it gives you a sense of what operates here. <A> A significant number of these devices use "top/level" control. <S> The operator may have a camera to see what is in front of the device but the main screen they are looking at is a top view of the landscape (including height map) of where it is flying. <S> The altitude is set to <S> x meters/yards above ground/sea level. <S> The device maintains height and direction based on this input. <S> As the drone isn't in live action and dodging anything - the delays and adjustments do not impact the route of the machine. <S> E.g. A 90 degree turn only requires 2 signals. <S> One to initiate the turn and the other back to base to confirm the turn is complete and the drone's current positioning. <S> You would rarely find a full scale drone needing manual adjustment of anything less than 500 meters. <S> Also the video footage from the drone is usually only uploaded at full quality once it has returned home.
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Some UAVs (like the Global Hawk) can perform the entire mission (from takeoff to landing) autonomously, negating the need for a pilot. The Predator is reported to have a 'latency' of around two seconds, which causes problems during takeoff/landing. Humans operating the flight are trained to be quick and anticipate rather than react ! Throughput problems can be handled using multiple beacons / transmitting sources.
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How to maintain straight and level flight after a climb? I'm new to flying and I have this question. Suppose I'm ascending to 2000 ft. at 67 kts and 2450 RPM. When I reach 2000 ft. maybe the plane wants to keep going up, even after I lower the RPM TO 2200, for example. How do I make the plane flight straight and level at 2000 ft? With the trim and keeping 2200 RPM, or lowering the RPM to, for example, 2100? <Q> Attitude + Power = <S> PerformancePerformance is your airspeed, climb/descend rate, and rate of turn. <S> Attitude is pitch, bank, and yaw. <S> Power is RPM, if you have fixed pitch prop. <S> So how do you transition from climb to level flight? <S> When you reach 2000ft, or maybe 1950, push forward on the yoke or control stick to about level pitch, check the altimeter to make sure you're at 2000ft, not climbing or descending. <S> Your airspeed will start going up. <S> Maintain forward pressure, it is going to increase as the speed increases (you can put some trim in to help). <S> Once you reach the desired airspeed, reduce throttle to keep the airspeed constant. <S> Then use trim to take out the pressure on the yoke. <S> Now this will give you a workout, because if you don't know exact RPM that you need to maintain desired speed, you will be chasing it and working the yoke to keep constant altitude. <S> So I would lower the nose after the climb, let it accelerate, then lower RPM to 2200 and keep the plane in level flight with the yoke and trim. <S> After a few minutes when everything is stabilized, I would note the airspeed. <S> Then I would reduce RPM to 2100, retrim nose up to keep level, wait a few more minutes and note the airspeed for 2100 RPM. <S> And so forth. <S> You can build a table of RPM and airspeed. <S> Then, next time you fly, you will just set the correct RPM for desired airspeed. <A> It all depends... <S> There will be some minimum power required to maintain level flight at any given altitude. <S> If you're applying more power than that then you can trim for level flight at any power setting. <S> More power means faster flight, higher fuel consumption and less range, while less power will save fuel and take longer. <S> It's really your call, but I'm sure your flying school will opt for economy every time! <S> You may also find that some light aircraft have prohibited ranges for RPM. <S> Some Robin aircraft, for example, prohibit continuous operation in a band just above 2000rpm (don't remember the exact details) <S> so you'd have to trim at a power setting below or above that band. <A> You need to reduce power or lower the nose. <S> Most likely you will want to travel faster than 67kts <S> so you will need to lower the nose and allow the airplane to accelerate. <S> As it accelerates, you will need to trim the airplane. <S> Proper trim technique requires you set the pitch and power for phase of flight and hold that with yoke pressure. <S> You will then trim off that pressure with the trim wheel. <A> Leveling out and accelerating to cruise speed is something done after every take off and will become routine. <S> The best way to experience it is to take a lesson! <S> One way to make it easier is to "round off" to your desired altitude starting from 500 feet below. <S> You are climbing at 67 knots, certainly do not want to yank back power with your nose in the air. <S> So you start working the elevator and pitch control (yoke or stick) together. <S> This will become much easier with time. <S> Start by easing yoke forward. <S> Speed will increase. <S> Ease off throttle. <S> Reach altitude and hold with yoke. <S> (I flew a 172 <S> so it's yoke). <S> Speed will increase. <S> Ease off throttle. <S> After practice you will hear and see good cruise rpms, at first keep working at it. <S> It is worse to miss altitude than to be off on speed by 5 knots. <S> (Don't forget to continue scanning around you as well!) <S> Once at altitude and speed, set trim for cruise and lean mixture if needed. <S> Enjoy your flight.
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Try to hold altitude, and work for desired speed with small throttle and pitch changes.
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What information might go in the remarks section of an IFR flight plan? When filing an IFR flight plan, what information might go in the "Remarks" section? <Q> The list of possible items in an ICAO flightplan ITEM 18 field is available over at the Skybrary , but here are a few examples that are commonly used: (c) <S> “TYP/” followed by type(s) of aircraft, proceeded if necessary by number(s) of aircraft, if “ZZZZ” is inserted in Item 9 Example: <S> TYP/2 DE HAVILLAND HERON. <S> Up to 60 characters may be used. <S> (e) <S> “ALTN/” followed by the name of alternate aerodrome(s) or bearing and distance to navaid/navigation point closest to alternate point, if “ZZZZ” is inserted in Item 16. <S> Up to 100 characters may be used. <S> Example: <S> ALTN/MEDIUM AIRPORT <S> (k) “OPR/” followed by name of the operator, if not obvious from the aircraft identification in Item 7. <S> Example: OPR/BIG COMPANY <S> (o) <S> “RMK/” followed by any other, plain language, remarks when required by the appropriate ATS authority or deemed necessary. <S> There is no limit in number of characters to be used. <S> Example: <S> RMK/TRAINING ILS APPROACH <S> AT SMALL AIRPORT <S> RMK/STUDENT SOLO FLIGHT <A> No SID/STAR if flying a small airplane and can't make the required climb gradients. <A> Put anything that you believe would be relevant for the controllers to know, but not recorded in other fields. <S> For example, you are filing from XYZ to XYZ to shoot practice approaches. <S> You can put that in the remarks, noting airports where you want to practice. <S> This will help ATC handle your flight. <A> Around the Great Lakes it is common to put "NO OVERWATER" if you don't want to be routed over the lakes. <A> In helicopters, IFR flights can often terminate in S-VFR. <S> In this example, one might add "Request S-VFR from HELOG to Downtown" <A> First, ATC does see the remarks section of your flight plan. <S> You should use it for anything that you, as the pilot, deem relevant to your flight. <S> As a 34-year retired Chicago Center controller and lifelong flight instructor, I have taught students to use this on every flight. <S> NO SIDS/STARS <S> ; NO OVER WATER; VFR GPS; NEW INSTRUMENT PILOT, etc. <S> In the controller world, a new instrument pilot is held to the same standard as a veteran airline pilot because we have no way of knowing the difference - unless you tell us. <S> Controllers are always trying to be efficient by turning aircraft onto final as close to the "approach gate" as possible. <S> This works great for seasoned IFR pilots but for new guys - not so much. <S> The localizer is flight checked to 18 NM. <S> A longer final for a new IFR pilot offers an opportunity for a more stable approach. <S> Why not put "REQUEST EXTENDED FINAL APPROACH" in the remarks section? <S> Just a thought.
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The remarks field, also called ITEM 18 field on ICAO flightplans can take a lot of information that you as the pilot deem necessary for controllers or authorities to know about your IFR flight.
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Do any aircraft carry spare parts for making repairs? I was curious to know, are there (or were there) any aircraft that regularly carry spare parts to be used for replacement or repairing the aircraft itself? If so, what are those spare parts? I'm not talking about built-in redundant systems like a second radio, but rather actual physical spare parts. For example, a car carries a spare tyre. <Q> If there are no suitable repair facilities, supplies or maintenance personnel available at the destination, then their own guy can fix any minor mechanical issues. <S> If there's a major problem then they would have to fly in additional repair supplies and staff (and fly out the stranded passengers). <S> I found this out on a flight from Johannesberg to Lilongwe (Malawi). <S> A seat was broken in the passenger cabin and SAA's on-board mechanic was able to fix it after a short delay. <S> The captain explained briefly why he was on board. <S> I assume that other airlines or operators who operate in undeveloped areas would do the same. <S> It's a lot cheaper to carry a mechanic and a few spares than it is to have an aircraft, crew and passengers stranded. <S> If anything on the MEL is broken then an airliner isn't airworthy so even a 'minor' issue can ground it. <S> I guess that the military might do the same for similar reasons, but I have no idea at all about that. <A> All of the 747-100/200 freighters I flew in the 1990s had FAKs <S> (Fly Away Kits) aboard. <S> I just checked a couple of the weight & balance data sets I still have from having done weight & balance work for one of them up until 2013, and the weights were 1967 and 1939 lbs. <S> If the aircraft was a nose loader, the FAK was usually along the side of the in the vicinity of the retractable ladder used to get from the main deck to the upper deck. <S> If the aircraft was not a nose loader, the FAK was always up against the main deck forward bulkhead. <S> The FAKs were constructed of heavy duty plywood and opened from the top. <S> One of the airlines had two BOW configurations for each aircraft, one with its FAK, one without, to expedite weight and balance calculations with or without its FAK. <A> After some brief googling, it seems the exact contents vary depending on the aircraft, operator, and the manufacturer of the FAK, but most seem to contain tools, spare tires, and other items for simple repairs. <S> Smaller kits are designed to fit behind a panel in the main cabin, while some larger ones are designed to fit in a Unit Load Device in the cargo hold. <S> I found a brief description here . <S> A fly away kit is a bunch of small spare parts and some tools and fluids to get the plane out of a place you don't have any support for the airplane. <S> We have one on all of our 727's because we operate into remote places that would take forever and a day to get a simple part to us that is a show stopper for the flight, it allows us to swap the part and fly away. <S> Things like spare landing light bulbs, radar altimeters, instruments, gyros, gauges and things like that are generally what I have seen and used from in there. <S> In addition we usually have a spare tire and sometimes a brake assembly somewhere in the belly. <S> Example of kit from airliners.net : <A> Yes. <S> If a US-registered aircraft is to be operated at night, it must carry: §91.205 <S> (c)(6) <S> One spare set of fuses, or three spare fuses of each kind required, that are accessible to the pilot in flight. <S> Now, as far as other types of spares go - no clue! <S> But some spares must be carried if certain requirements are met - eg, your airplane has fuses accessible from the cockpit. <S> In the event of an electrical problem, the flight crew can replace the fuse as required. <A> When I flew C-130 transporters in the RAF, we always carried a FAK and a 'Ground Engineer', but then the extra weight was of little consequence compared to the delay of the mission in some remote location. <S> I now fly Business Jets, where there is significantly less room, less available (spare) payload weight, and certainly no-one qualified to make the repairs on board, so the only thing carried is a small set of wheel chocks, a couple of cans of oil and clamps for the trust-reversers. <A> Normally planes don't have major spare parts. <S> Instead of parts they have redundancy in almost every flight system, which under certain circumstances an experienced pilot can take advantage of in order to keep operating the plane safely. <S> Have in mind that the weight issue in a plane is very important. <S> That's why a popular phrase between pilots says: Every takeoff is optional, but landing is mandatory
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South African Airways flights to 'less developed' locations in Africa often carry a mechanic and some spares on board. I've heard what you're describing called a "Fly Away Kit" or FAK.
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Why are safety demonstrations done while taxiing? In airliners, safety demonstrations are performed when the aircraft is leaving the gate. I understand it cannot be done latter as an aircraft incident including an evacuation may occur at take off roll. But I think it could be done earlier (e.g. in waiting area before boarding). This way, if any passenger has any question (e.g. this one ), this passenger has plenty of time to ask flight attendants before takeoff. This time may also be used to explain why safety demonstration include all those items (life vest inflated outside the airplane is not the only item that could raise questions). Moreover it could be a good use of waiting time before boarding. EDIT : As highlighted by one answer , some airliners use video to do this demonstration. In this case, the generic items (i.e. not aircraft specific) of the video could be played on screen in waiting area in addition to the actual briefing. <Q> Many passengers don't reach the gate until seconds before the gate closes for a variety of reasons. <S> They won't get the pre-boarding briefing. <S> Taxiing is the only time before takeoff where the crew knows for sure that all passengers that will be on the plane are there. <A> The waiting area is a poor choice of place to give a safety briefing. <S> Passengers are talking amongst themselves, fiddling about with hand luggage, or listening to music on earphones, and may not respond well to being interrupted for the briefing. <S> There are often disturbances (e.g. passengers on other flights passing the gate). <S> As ratchet freak pointed out, not all the passengers will arrive early, and if everything is running to schedule, there shouldn't be a wait between the announced boarding time and the actual boarding. <S> Typically, before boarding (most of) the cabin crew is on the aircraft getting ready for the boarding. <S> They don't have spare time to go to the gate to perform the demonstration, so it would mean having extra staff who just do briefings, with an extra risk of briefing for the wrong aircraft. <S> In addition, it's only possible to point out the overhead panels and emergency exits when you're in the aircraft. <S> On the aircraft immediately before take-off, every passenger is in their seat, with no headphones in (in case of an emergency), and the cabin crew are spread out with nothing else to do. <S> It can be an anxious time for passengers and crew alike. <S> It's not only a suitable free period: the briefing makes an important activity to keep passengers and cabin crew alike busy during this time. <S> Finally, even if passengers don't listen to the briefing, it gives them a minute to picture the exit routes in relation to their actual seat location, and mentally plan for an emergency. <A> A very simple answer to this question is that the FAA (and international agencies) require it to be so to ensure that all passengers are available to hear/see the briefing. <S> The other more robotic/pilot-like answer to this is because it is on the taxi checklist. <S> Haha :) <A> This simplest answer is a matter of economy. <S> If the airline gave the briefing in the terminal or wherever before loading the passengers, then the airline would have to allocate resources (personnel, demo gear, logistical planning, and policies) to preform this task. <S> It could be done but the cost (monetary and intrinsic) would be high and the ROI would be little to none. <S> Instead, they choose to do it while taxiing because it is the most economical time to do so as the flight attendants have little to do (as opposed to during flight where passengers are unpredictable in their needs). <S> Also, interesting to note is how some flights (Delta at least) have switched to a fully automated system for the safety briefings. <S> Note that this procedure actually saves money by freeing up resources previously committed (as well as potential ad revenue). <A>
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While the above are certainly good reasons how this came to be, today the answer is very simple and is the same for almost all commercial aviation questions starting with "why": because there is an FAA regulation and changing an FAA regulation needs monumental effort and thus needs an extremely compelling reason first.
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Would a headwind result in a faster propeller rpm? A few weeks ago I did an experiment with a model aircraft that has a motorized propeller. I turned on the propeller and it turned at a constant speed. Then I turned on a desk fan and put it in front of the propeller (see the picture below) and I saw an increase in propeller rpm and an increase in noise. Does this also happen to a propeller when a headwind hits it? <Q> The problem is you're holding the aircraft with your hand. <S> Imagine a windmill. <S> It has no power at all, it spins freely. <S> What happens when wind is blowing at it? <S> It turns. <S> Now imagine a propeller with no power connected to it, so it acts like a windmill. <S> If wind is blowing at it, it will turn just the same. <S> Why? <S> Because a propeller pushes wind backward when it turns. <S> When it is facing a headwind, the propeller wants to turn such that it is pushing air at the same speed as the arriving air. <S> In your case, I suppose the fan is blowing air at a faster speed, compared to the propeller is pushing air on its motor. <S> Say the motor pushes air backward at 1 m/s. <S> The fan blows air at 2 m/s. <S> That's why it spins faster with the fan on. <S> But that's only true as long as you're holding the aircraft with your hand. <S> In flight, nothing is holding the aircraft at a constant ground speed. <S> For example, assume in a no wind condition, an aircraft is flying at 80 knots. <S> Suddenly it encounters a 10 knots headwind, and continues to fly into this headwind for the remainder of the flight. <S> What happens? <S> At the moment of encountering the headwind, the airspeed indicator in the cockpit jumps from 80 to 90. <S> The propeller rpm will also suddenly jump to a higher value. <S> But that is not going to last. <S> The aircraft is getting pushed backward by the wind, the airspeed is going to slowly drop back to 80. <S> There is not enough power to keep the propeller at the higher rpm which pushes air at 90, it can only to 80. <S> After a while, it is flying at 80 knots relative to the air, and 70 knots relative to the ground. <A> A propeller is always facing a headwind, it's called "airspeed". <S> I don't really know what to tell you, the wind relative to the ground doesn't matter to the airplane or the propeller, the wind hitting it head on does, and yes, as the airspeed increases the load on the prop is reduced and the RPM increases unless you have a constant speed propeller (and thus a governor that changes the pitch of the blade when the RPM increases to combat this). <S> A wind shear does indeed change the airspeed momentarily (more so for larger aircraft with more momentum), but so does pitching over and diving. <S> The net effect is that a "headwind" (as measured relative to the earth) will only affect your ground speed, and thus the time it takes to get to your destination. <S> The headwind, as measured relative to the aircraft, is called airspeed, and is usually kept at some set value appropriate for the aircraft in cruise. <A> Surprisingly, the answer is yes for geared engines. <S> With geared engines, the propeller has enough mechanical advantage to drive the gearbox (rather than the engine driving the gearbox). <S> This can hurt the gearbox and the engine. <S> The Rotax engine employs a built-in 2.4:1 reduction gearbox. <S> When descending, you are not supposed to reduce power, otherwise the propeller will push on the gearbox and the engine (rather than the engine turning the gearbox and then the prop).
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If the airspeed increases abruptly, the RPM will increase slightly as the load decreases (air doesn't have to be accelerated as much), which is countered by the prop governor (if you have one) and the fact that the airplane will slow down to match the new headwind since you're not feeding it any more power to maintain the new higher airspeed.
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What size/engine/payload aircraft would be needed for carrying two passengers and a motorcycle? I'm not even in the realm of knowledge of aircraft so don't chew me out on lack of terminology please. My objective is to fly myself and a 300-pound motorcycle to destinations to ride from there. I weigh 185 lbs, the motorcycle weighs 300-400 lbs, any secondary seating and other interior furnishings would most likely be removed to reduce weight, and, obviously, all the necessary components would stay. As a side note, the aircraft needs sufficient enough door to get a small motorcycle in. Let's not even talk about how unsafe this might be; this is all hypothetical. How large, or what class, of an aircraft would be needed for such a task to be completed? <Q> The question is incomplete without information about the range this aircraft should have. <S> Pilatus in Switzerland is always fond to tell of one of their customers who bought not one, but three PC-12 s for exactly this purpose, and has one plus a Harley-Davison motorcycle stationed on each continent of interest. <S> The size of a PC-12 allows the installation of a crane, so loading and unloading of the motorcycle are simplified. <S> PC-12 side view, with open cargo door (picture source ) <S> Obviously, even a PC-12 does not have the intercontinental range to go anywhere, but if you plan to stay within one continent, range is not an issue. <S> Alternatives in this class are the Czech Aero 270 or the Cessna 208 Caravan . <S> All use a PT-6 turboprop engine, and you will need professional maintenance to keep them flying, so using them does not come cheap. <S> However, fitting the bike in will be a challenge. <S> If you want more internal space and are not afraid of antique taildragger airplanes, the Antonov An-2 or the Canadian DHC-3 Otter would also be a good and reasonably priced choice - however, maintaining one (and especially its radial engine) will also burn a hole in your pocket. <S> DHC-3 in Pensacola <S> (picture source ) <A> The question is what small light GA aircraft has a payload of 185 + 400 + 185 (ball park for the second passenger) = <S> 770LBS <S> The second question is how far you want to fly and thirdly getting the bike into the plane. <S> The list may include Piper Saratoga (nice loading doors with the seats removed, rumor has it you can get a piano through the loading doors of a saratoga ) <S> Beechcraft Bonanza Cessna Caravan (with type cert) or Cessna 206 on the smaller side of their offerings Piper Seneca (if you have a twin rating) <S> Beechcraft Barron and the list goes on <S> (these are just the common ones). <S> Remember that you can always take a gain in useful load if you sacrifice fuel but this is highly dependent on how far you want to go. <S> Removing the seats will buy you back some useful load but here in the US that will require a new weight and balance to be prepared for you by and <S> A&P. This is a pretty common task but need to be done for the plane to be legal without seats. <S> On top of that since most motorcycle weight is in the engine I would be very cautious when doing your W&B for the flight. <S> I can only assume you will strap the bike in, in which case I would measure engine to CG for calculation purposes. <S> You can also take a bit of a gain by draining the gas from the bike before flying. <S> Since you are presumably going to an airport you will be able to gas it up again (possibly with 110LL...). <S> Continuing on from the above list you get into turbo-prop land, depending on cost that may be doable or not for you. <S> Can you further define your mission to include both distance and budget, that will make a big difference. <A> Cessna 206. <S> This plane has been to Alaska twice carrying a motorcycle. <S> QED.
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A more reasonable alternative would be piston-engined, and here the Cessna 206 or 207 (which @Terry already suggested) would be a candidate.
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What happened to the blades in this picture? Here is the picture Source:(brians-travels.com) This looks like a photoshopped picture, but I believe it isn't. Is this some kind of strange occurrence that occurs only with the human eye? The blade on the top looks bent downwards. I can't figure out what happened in this picture. And will your picture look like this every time you take a picture of a fast moving propeller? <Q> Essentially the image is captured a single line at a time and the fast moving propeller changes location between each line captured. <S> Wikipedia has a nice diagram showing what happens step by step: <S> On our sister site photography. <S> SE has a question asking about it. <A> This is a result of the way the camera shutters operate. <S> Usually, the cameras don't capture images in the same way as human eye i.e. they don't take image of the whole scene simultaneously but rather 'scans' horizontally or vertically. <S> In normal cases, this rolling shutter method is not a problem, but can cause issues when the object is moving at high speeds. <S> Quote from user FGK : <S> The plenomenon is due to Rolling shutter (also known as line scan) is a method of image acquisition in which each frame is recorded not from a snapshot of a single point in time, but rather by scanning across the frame either vertically or horizontally. <S> In other words, not all parts of the image are recorded at exactly the same time, even though the whole frame is displayed at the same time during playback. <S> This in contrast with global shutter in which the entire frame is exposed for the same time window. <S> This produces predictable distortions of fast-moving objects or when the sensor captures rapid flashes of light. <S> Source: <S> ephotozine.com <S> In other words, it is due to camera rather than <S> the propeller blades themselves. <S> The effect of a simulated rolling shutter on a spinning disc shown below: " Rolling shutter effect " by Cmglee - Own work. <S> Licensed under CC BY-SA 3.0 via Commons . <A> This is an effect produced by the digital camera that took the picture. <S> The CMOS sensor "scans" the picture from one edge to another, possibly bottom to top in this example. <S> Each line of the photo is taken at a slightly different time, and the prop moves fast enough that it moves a little bit in between each scan line. <S> After the camera puts all the scan lines together into an image, you can get the effect you see here. <S> You can read more about this effect at Rolling shutter .
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It's an artifact of how a digital camera downloads captures the image from the sensor called rolling shutter .
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Why do jet engines take a long time to throttle down? Apparently jet engines can take several seconds, up to ten or fifteen seconds, to go from full power to idle. Why is this? Can't a simple fuel valve shut off fuel flow? Or reduce it to whatever flow rate corresponds to idle? Either of these, if done with a valve, should happen almost instantly as far as I can tell. This would surely cut thrust, regardless if the engine still spins for a while. Is there something dangerous about this idea? To me it seems like a fuel valve can close and open again as many times as it wants. Note: I'm interested in turbojets and turbofans. And I care about throttling down only. <Q> The simple answer is rotational inertia , once you get a heavy mass spinning fast that heavy mass will have a tendency to continue spinning fast unless something else is acted upon the object. <S> Piston engines have a great deal of friction between the piston walls and pistons (how they hold the explosion in) <S> this helps them slow down faster than a jet in which the turbine is made to easily handle this <S> thus the joints are very well made and very free moving. <S> While cutting fuel will keep the engine from continuing to generate thrust the turbine will continue to spin until a force causes it to stop (drag and friction really). <A> Jet engines have little mechanical margin, and operate at high temperatures. <S> That means all components expand by more than the mechanical margins when heated. <S> This is no problem when everything expands and contracts together in a controlled fashion. <S> This may be counterintuitive but is easily demonstrated. <S> Cut a circular hole in a metal plate, and heat up the plate. <S> The hole will grow with the same expansion rate as the surrounding material. <S> Now what happens if we suddenly stop the fuel flow? <S> The compressive heating of air flowing into the engine doesn't suddenly stop, but all the air flowing through the engine does cool it. <S> This means that the turbine in the back does cool as relatively cool air flows through it. <S> Not only does this cause thermal stresses, but the turbine will shrink. <A> It is the same in all object which have a large mass. <S> In an automobile, there is the flywheel which stores some of the energy the engine produces so that a little hiccup in the pistons would not interrupt the spinning. <S> With the jet engine, the large mass of the turbine also keeps the increase or decrease of speed at a constant rate so that the engine would not produce "jerks" of power when the throttle is changed.
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Basically it is that the more weight the moving object has (the turbine in this case) the more time it takes to slow down because of the energy stored in a moving object.
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Are there any aerospace examples of applying a boat tail? A way to reduce the pressure drag of bluff bodies is to apply a tapering of the tail (so called boat tailing) I know some (extreme) examples of this method of drag reduction applied to cars: Source And I know that this a feature of the Very low drag bullet Source I was wondering if there are any aerospace applications? <Q> This depends on the mission the plane is built to fit. <S> Some planes need the cargo space so the tail is less tapered but most planes have at least some taper. <S> Diamond Aircraft have very tapered tail sections <S> ( source ) <S> Even the older GA designs like the Piper Seminole <S> have a good deal of tail taper <S> ( source ) Larger planes have some tail taper as well however sometimes there is less as there are often systems in the tail like the APU or there is storage space. <S> ( source ) <A> Aerodynamic fairing fitted to the space shuttle for transport aboard NASA's 747 ferry aircraft <S> Although uncommon it has been used for aerodynamic and stealth reasons on fighters. <S> An example is the chisel like engine enclosures on the YF-23 aircraft. <A> Some notable exceptions which only taper in one dimension are rear-loading cargo planes like the C-130 and the Shorts Sky Van.
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Almost all plane designs are made in wind tunnels and have a tapering empennage.
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What causes tail-down force? What phenomenon causes aerodynamic tail-down force? Why will there be more downforce on the tail when an aircraft picks up speed? What happens if the aircraft goes too slow - does this means less downforce on the tail? Do the center of lift and center of gravity play any part in determining the downforce on the tail? <Q> The phenomenon is called trimming. <S> This is the process by which the pilot adjusts the lift at the tail surface to shift the center of pressure right above or below the center of gravity and removes any stick force so the airplane will keep this attitude unaided. <S> If the center of gravity (CG) is right above or below the aerodynamic center (AC), the aircraft's longitudinal static stability is indifferent. <S> Move it forward and stability increases, move it further back and the plane becomes unstable. <S> The aerodynamic center is where the angle-of-atttack-dependent lift forces act, and in an indifferent configuration the lift coefficient on wing and tail will be equal. <S> Increasing stability thus means to reduce lift at the rear surface, and if a lot of stability is desired, lift at the rear surface will become negative. <S> When the airplane is hit by a gust (change in vertical wind speed), the angle of attack at both wing and tail will change by the same amount. <S> Now it is important how much lift changes relative to the lift before the gust. <S> If the lift coefficient on the wing is larger than on the tail, the same amount of angle of attack change will cause a relatively smaller change of lift on the wing than on the tail, and the center of pressure will move such that it causes a correcting pitch moment. <S> By selecting the proper center of gravity location, the pilot can adjust the level of stability he/she desires. <S> To stay at the desired attitude in flight, he/she now has to move the incidence of the empennage (or the elevator deflection) to a point where any pitch moment disappears. <S> The consequence is a downforce on the tail if that is what it needs to trim the aircraft with the given center of gravity location. <A> On a conventional wing and tail configuration the center of lift is normally behind the center of gravity. <S> This causes a pitch-down force, which is counteracted with the stabilizer's downward lift. <S> On a rear-wing configuration the same is accomplished with a canard. <S> The only difference is that the canard provides upward lift <S> and so it adds to the total lift, contrary to a conventional tail just increasing drag. <A> The tail is a lifting surface just like the wings. <S> Downforce is just the phenomenon of lift directed in the opposite direction. <S> You can also see examples of downforce in things like the spoilers on a Formula 1 car. <S> Going faster produces more lift and so more downforce. <S> What's unique about the tail is that it can be affected by the downwash of the wings themselves which comes into play when looking at design choices like a T-tail. <S> Zooming out more broadly, the reason you want downforce is longitudinal stability. <S> On some planes and in certain configurations the tail produces positive lift instead of downforce, all in the name of balancing the plane, though those designs tend to be harder to fly. <S> You may notice that the tail is usually much smaller than the wings. <S> This allows for better longitudinal stability as the tail experiences larger relative changes in lift (downforce) compared to the wings which provides a negative feedback loop that brings the plane back to equilibrium. <S> The location of the center of gravity relative to the center of lift matters because it produces a certain pitching moment that then needs to be counteracted by the force produced by the tail.
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As speed increases, the wing produces more lift, thus more tail-down -force is required to maintain attitude.
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Why is the fuselage on an airliner circular-shaped? Consider the fuselage of an A300 . I have noticed this not only with airliners, but also for private jets and turboprops: why is the fuselage circular-shaped? Why don't aircraft have square-shaped fuselage? Does it have to do with too much drag? <Q> If you pressurize any hollow structure, it will try to assume a round shape. <S> If you want to create a lightweight pressure vessel, again a sphere will be the most efficient result, because there the stresses in the skin will be equal at every point. <S> Blow up a party balloon if you are in doubt. <S> A sphere is not the most efficient shape for aerodynamics, so fuselages are elongated spheres with a nice fairing at the end. <S> If you make them cylindrical in the middle, you can build most bulkheads on the same jig and can interchange sections of the internal fairings. <S> Plus, if you need a longer or shorter fuselage for the next version of the plane, you can easily add or remove sections - the parts will still fit after the modification. <S> Note that the fuselages of unpressurized aircraft don't follow this logic <S> A Short Skyvan or a Dornier 228 have fuselages with a rectangular cross section, so large cargo can fit in. <S> Also, some fuselages are combinations of cylinders. <S> The Boeing 377 Stratocruiser used the lower fuselage of the B-29 and had an upper, larger cylinder on top to give the passengers more room. <S> Boeing 377 cross section (picture source ) <S> For the same reason, rocket stages are cylindrical, too. <S> They also need to be aerodynamic, have to tolerate high internal pressure and need to be lightweight. <A> The fuselages are circular (or nearly circular) in shape for two main reasons : <S> Also, the non-circular sections have stress concentrations when pressurized, which may lead to failure. <S> In case of a circular design, the flow will not separate under small (to moderate) angles of attack and in sideslip. <S> In case of non-pressurized aircraft, the fuselages are dictated by volume constraints and are usually rectangular in shape as it is more efficient in space utilization. <S> Source: <S> adg.stanford.edu <S> In the case of pressurized aircraft, the best option structurally is to have a circular fuselage, but in order to have a useful internal space, an elliptical or 'double bubble' design is used, with an outer circular section and divided internal sections, like the A380. <A> Why don't [airliners] have square shaped fuselage? <S> Shorts Skyvan photo from Wings over Europe <S> Shorts Skyvan diagram from A Tall Guy <S> Most airliners are pressurized. <S> If you inflate a rubber balloon you'll notice that the most economical and strongest shape for a pressurized container is one with a circular cross-section. <S> You'll also notice, when you inflate an Origami water bomb (you should stop reading this and make an origami water bomb now), that the flat sides buckle and bulge - flat sheets are not good at resisting pressure. <S> As you can see above, in some circumstances, aircraft manufacturers do beleieve that the advantages of a rectangular cross-section are worthwhile. <A> Drag has little to nothing to do with it. <S> The primary reason why the fuselage is circular (or elliptical ) shaped is that the cabin is pressurised. <S> This means that, mostly during cruise, the interior of the fuselage has an higher pressure than the outside atmosphere. <S> The circular (or roughly circular) shape allow the fuselage to avoid blowing up like a baloon with minimal amount of material, minimizing the overall weight of the aircraft. <S> A square fuselage would break apart at the corners due to stress concentration . <S> A circular shape do not have corners were the tensile stress can concentrate.
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Spherical airliners would have too many disadvantages but cylindrical ones have a good balance between strength, weight, drag and space-efficiency. The main reason is that for a circular cross section, the pressure loads are resisted by tension, rather than by bending loads in non-circular sections.
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How to correct for crosswind in VOR holding pattern without wind information? I've heard many articles about crosswind correction in VOR holding pattern. They mainly tell the outbound leg=correction times three things for slow speed aircraft. I notice all of them require wind information in holding pattern. What if somehow under some circumstances the pilot doesn't have the wind information whatsoever in holding pattern? Like the wind may change unexpectedly. Is there any method to maintain precise 4 minutes holding pattern in such condition? <Q> One you are established inbound on the VOR radial note the heading you are flying to maintain that course. <S> The difference between that and the radial is your wind correction angle. <S> Multiply it by 3 and apply it to the outbound course heading. <S> To do this you don't need to know anything about the wind. <S> You just need to be able to intercept and track the inbound radial. <S> You can repeat this every inbound leg <S> so if the winds are changing you can update your correction every 4 minutes and you always know you are on course one of ever four minutes. <S> With the generous obstacle protection area even small errors will not compromise safety. <A> When holding, it is true that you should take then inbound wind correction and multiply it by three and use that for the outbound correction. <S> Your question centers on what happens if you don't know the correct wind information and obstacle clearance. <S> Fortunately for us, the FAA has given us a wide obstacle clearance area for the holds. <S> While it is important to stay on the protected side of the hold, if you find yourself on the unprotected side of the hold, you are still "protected". <S> Picture taken from http://forums.jetcareers.com/threads/holding-pattern-protected-area.80377/ <S> The idea is to fly the correct entry procedure and it will help to ensure you stay within the obstacle clearance protected area. <S> A direct entry requires passing the holding point and immediately turning to the outbound leg. <S> You may not know the wind correction so fly the outbound heading. <S> Upon turning inbound get back onto your inbound course and try to determine your wind correction angle <S> A parallel entry requires passing the holding point and tracking outbound on the radial. <S> You should be able to figure out your wind correction. <S> Turn 180° + <S> 45° to re-intercept the inbound course. <S> At this point, you should have a good idea where the wind is coming from. <S> A teardrop entry requires passing the holding point and turning 30° into the protected side. <S> When you turn inbound, there should be enough time to figure out what the winds are doing. <S> If the winds are constantly changing, do your best to stay on the protected side of the hold, if you venture a little to the unprotected side, you are still covered. <A> For lateral corrections, use a trial an error process of crabbing to maintain the selected track to the fix. <S> To compensate for unknown headwinds and tailwinds, fly a consistent indicated airspeed and time your outbound leg from and inbound leg to the fix. <S> Note the difference between intended and actual times to fly the leg eg <S> you’re flying a 1 minute leg <S> but it takes you 1 minute and 40 seconds from rollout on inbound leg to crossing the fix, <S> there’s a 40 second difference. <S> If your leg takes longer than planned at constant airspeed <S> you have a headwind, if it’s shorter, you have a tailwind. <S> Take half that difference and subtract that time for your outbound leg for inbound headwinds and add for inbound tailwinds. <S> Eg as in the example above, difference was 40 seconds longer, so it’s a headwind. <S> Half of that is 20 seconds <S> so you should fly an 1 min - 20 seconds = <S> 40 seconds long outbound leg <S> so your next inbound leg is one minute long.
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One the airplane maintains a stable track on the inbound leg, note the crab angle and make use of that, applying the same angle inbound to the fix and an the same angle in the opposite direction on the outbound leg.
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How Centre of Gravity (CG) is adjusted? I've gone through the following questions on Stack Exchange and other few questions too: Why is managing CG (centre of gravity) important? How are the limits of the center of gravity chart established? I still do have 2 questions in mind: How do they adjust the fuel quantity/weight based on the passengers' weight on the plane? (was there any situation where few fat guys have been asked to move to front or back because I never saw any airliner weighing their passengers before boarding) As the fuel starts burning, the pilot will fill/empty/exchange it from wing to wing or other storage location to balance CG, Will this cause imbalance (moving out of defined tolerances) in CG based on the passengers' weight? <Q> The main issue is what is referred to as the Weight and Balance of the aircraft. <S> When an aircraft is in flight, its weight and balance needs to be within a controllable range in order to ensure the plane can both recover from a stall condition and rotate on takeoff. <S> This is visualized by the weight and balance "envelope: As you can see, there are limits where the aircraft is not fit for flight. <S> We must stay inside the drawn lines in the center. <S> This caused at least one notable accident: Air Midwest Flight 5481 . <S> As a result of this accident, policies were changed to get more accurate baggage and passenger weight. <S> In GA flight, it is not uncommon for pilots to ask for passenger weights. <S> Usually, as a rule, we add a bit to that <S> in case people are embarrassed (10%). <S> It is very common for pilots to assign seating on smaller aircraft with heavier people sitting in a location where the distance to the datum is smallest (near the front). <S> Weight and balance can be moved out of limits by fuel burn. <S> In fact, a few questions on the private pilot written exam deal with this exact scenario. <S> Most planes have tanks near the CG, so they don't experience problems with fuel burn. <S> In planes with an aft belly tank, the CG can move forward significantly and out of limits. <S> This would cause the aircraft to be unable to pitch up as desired. <S> Swept wing jets that use horizontal stabilizer tanks in the tail of the aircraft have computers and pumps to move the fuel as desired to keep their CG in the desired place. <S> Pilots of smaller/less traditional airplanes need to be conscious of this, and plan accordingly. <S> Especially those with a-typical fuel tank positions. <S> Pilots of larger commercial style aircraft are less concerned with the exact position of 1 or 2 large people or heavier bags because their aircraft has a much bigger capacity and less "sensitive" envelope. <S> They still are affected by the physics, though, just like everyone else. <A> In the majority of airplanes fuel is stored in the wings and tanks which are positioned at or near the center of gravity at empty. <S> This limits the forward-back moment arm of the fuel so as fuel is used up the center of gravity does not shift forward or back that much. <S> Balancing fuel weight is therefore more of a question of lateral CG, a pilot (or automatic onboard system) can pump fuel or switch tanks to balance fuel load. <S> The seating configuration of passengers does not have much impact on lateral CG as their moment arm is very small. <S> In light aircraft passenger weight and position is a big concern, however passengers are actually one of the smallest weight components on a commercial airliner compared to the plane itself, fuel and cargo. <S> You won't see overweight people being asked to move to balance a commercial aircraft. <S> Seating systems deal with numbers and are designed to spread the load evenly across CG. <S> Even if all the passengers of a half-empty commercial jet sat at the back there would still be enough trimming power to keep the airplane in balance. <A> In some newer planes i.e.B-787, A-380 etc., the CG is adjusted after loading the cargo. <S> The landing gear have solid state scales built in and in the extreme tailcone is a jackscrew with a very heavy weight attached, usually made of dense depleted uranium. <S> This can be moved laterally + <S> /_ several feet to adjust the CG.
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To answer your detailed questions: On airlines, a "Magic" number was used to approximate all weight for passengers and baggage.
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Why don't stealth aircraft designs use podded engines? Normally, it seems all the stealth designs dont use podded engines like others. Is this just to avoid the radar cross-section? <Q> Yes. <S> From the PoV of stealth aircraft, the podded engine has significant disadvantages: <S> For example, the B2 Spirit engines were located inside the fuselage, as shown in the schematic below. <S> The exposed compressor blades in the podded engine reflects radar waves, which is not good. <S> For example, in Boeing X-32, the location of the engine meant that the compressor blades will be exposed to the Radar and baffles were (proposed to be) added to reduce the Radar cross section. <S> On the other hand, it can be seen that it is practically impossible to see the F-22 compressor blades from any angle of the inlet. <S> Source: <S> f-16.net <S> In case of podded engine, it is difficult to shield the exhaust thermal signature. <S> Compare the infrared signature of the typical airliner in the following picture with that of the B-2 Spirit in the next picture. <S> Source: laserfocusworld.com <S> Source: <S> bestfighter4canada.blogspot.in Of course, contemporary combat aircraft don't use podded engines at all (with the exception of the A-10, which is a ground attack aircraft). <A> In addition to aeroalias's very detailed answer, I think a good point to start with this question is: "Why would any aircraft not use podded engines?". <S> There are a few advantages of having an engine in a separate pod, commonly it comes down to a simple lack of room in your fuselage. <S> Either your thrust requirements would require too many or too large of engines to fit streamlined in a body that fulfills your other specifications. <S> So, we see these on things with massive thrust requirements, which are almost exclusively cargo/transport or bomber aircraft. <S> There are a few other bonuses too, like accessibility for maintenance or removing the sound and heat from the body of the aircraft. <S> Unfortunately, they also present massive, super-hot, and exposed targets. <S> So for any combat aircraft that has the option, they will be onboard. <S> The only combat aircraft I know of with podded engines, the A-10, has to push a very heavy airframe around with high mission loads. <S> The main body is kept remarkably thin, thanks to the lack of internal weapon bays, so it makes more sense to mount these two large engines in pods then to grossly swell the body to fit them. <S> It also gives more freedom in the placement and alignment of these engines, which are a bit particular for the A-10 given its unique lift and weight distribution. <S> There are additional reasons why you would avoid mounting these on a stealth aircraft, but for airframes like the F-22 or F-35, it wouldn't have made sense anyway. <S> Large stealth aircraft like the SR-71 and B-2 are sleek enough that the requisite engines can fit rather comfortably within the design of the wing as well, so podding them would only hamper the design. <A> The A-12's engines are podded partly for field replacement. <S> The port and starboard engines are IDENTICAL (not symmetrical). <S> That is to say, one of them is mounted upside down. <S> As a result, they are interchangeable and can be field swapped. <S> They built it so that if you have two A-12s stuck on the ground each with one bad engine, no matter which engine it is <S> you can turn those into one A-12 with two good engines. <S> It was designed for grimdark WW3 with Russia in Eastern Europe. <S> Its designers expected that it would be necessary to cobble damaged planes together at airstrips to continue the fight.
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The engine pod has a high Radar Cross Section; In fact, stealth aircraft bury the engine inside their fuselages to minimize radar cross section.
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Airbus is to fly-by-wire as Boeing is to...? If the control system in an Airbus is fly-by-wire, then what is the control system in Boeings? How does it work? What are its general differences from the fly-by-wire? <Q> Boeing uses a more direct approach to control (but both systems have warnings). <S> In short it boils down to who has final authority of control surface actuation. <S> Fly by wire does not just mean that control surfaces are controlled electronically (even the Cessna 172 has electric flaps) but that a computer in some way takes the pilot (or pilots) inputs and generates a control surface output. <S> In the airbus case the computer has the final say, so if the pilot commands the plane to do something it should not, the computer will not move the control surfaces and allow it to enter such an attitude or speed. <S> Boeing takes the reverse view and gives the pilot final authority so what ever control inputs are made translate to control surface movements. <S> With that in mind Boeing does have things like a yoke shaker in the event of approaching a stall and a yaw damper etc. <S> Airbus will allow full control surface actuation with Direct Law however the plane is not normally in this mode. <S> Boeings Standard protections and augmentations is similar but will allow the pilot to enter the conditions "...to inform the pilot that the command being given would put the aircraft outside of its normal operating envelope, but the ability to do so is not precluded." <S> ( source ) <S> On the contrary vertical stick motion in an airbus in flight actually controls load factor and not necessarily pitch directly. <S> So its always some form of proportion to the aircrafts speed. <S> If memory serves Boeing control surfaces are set up such that movement of one yoke will move the other yoke in tandem, likewise they can not be simultaneously moved in opposite directions while airbus controls can be moved in opposite direction and the computer will summate the inputs (although an override button is present on each stick to disconnect the others should something be improperly acting on it). <A> tl;dr: <S> Boeing has built some FBW airliners (777, 787) and some that aren't (707/720, 737, 747, 757, 767). <S> Airbus has built some FBW airliners (A320 series, A330, A340, A350, A380) and some that aren't (A300, A310). <S> long version: <S> Fly-by-wire (FBW) is a system that replaces the conventional manual flight controls of an aircraft with an electronic interface. <S> The movements of flight controls are converted to electronic signals transmitted by wires [...], and flight control computers determine how to move the actuators at each control surface to provide the ordered response. <S> Fly-by-wire, Wikipedia <S> With that description in mind, both manufacturers build FBW aircraft. <S> Pilots' control inputs are translated into aircraft flight control surface movements by a set of redundant computers. <S> Boeing's first FBW airliner was 1994's 777 , and their only other pure-FBW design is the 787 . <S> The 748 is a partial-FBW design. <S> Both the 777 and 787 have some computer-enforced limits in place to keep the aircraft within the flight envelope, but those limits can be overridden, and the aircraft generally are said to 'feel like a normal airplane'. <S> Airbus's first FBW airliner was the 1987's A320 , and all their subsequent designs are FBW. <S> Airbus's control logic is much less direct than Boeing's , containing full flight envelope protection in the 'Normal Law' configuration, and correspondingly less protection if the aircraft reverts to 'Alternate Law' mode (which is roughly comparable to Boeing FBW). <S> None is provided in what is called 'Direct Law', where the computers simply pass commands directly to the flight control surfaces. <S> That said, both manufacturers build fly-by-wire airliners <A> Boeing is to fly by wire as Airbus is to fly by computer, would probably be closer to the mark. <S> Both are fly by wire, but Boeing is closer to direct input - I move the yoke halfway to the limit, the controls move halfway to their limit <S> While Airbus is a suggestion to the aircraft as to what you'd like it to do - I move the side stick halfway to the limit, and the plane performs that action at something like half the rate the performance envelope should allow. <S> Sort of.
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Using a pure definition of fly-by-wire , both Boeing and Airbus airliners can be considered fly-by-wire .
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What are the advantages of a variable-incidence wing as used in the F-8? What are the advantages of a variable-incidence wing as used in F-8? Do weight and other issues outweigh the advantages and that's why it's not found in many (any?) other aircraft? <Q> The main reason for having variable incidence wing in the F-8 was that it allowed the production of increased lift due to a greater angle of attack without reducing pilot visibility as the fuselage stayed level. <S> For aircraft with high angle of attack TO/landings (like delta winged aircraft), pilot visibility is a problem in low speed landings, as the nose will obstruct the runway (or carrier, for that matter) in extreme cases. <S> There are two ways to solve this problem: <S> Droop the nose, like the Concorde or Make the wings variable incidence, like the F-8. <S> The first option is usually preferred (same thing was done in Tu-144) as the weight penalty is (significantly) less. <S> However, this wasn't possible in the F-8 as the engine air intake was in the nose; so the incidence of wings was changed. <S> The variable incidence wing had the added advantage of reducing the length of landing gear required and improved the low speed characteristics. <S> In case of Martin XB-51, the variable incidence wings were used to reduce take off distance as it was expected to be operated from forward airfields. <A> The Vought <S> F-8 Crusader had a variable incidence wing because of the role it was designed to fulfill. <S> Both the <S> F-8 and the F-104 <S> had comparable performances, but the F-104 was designed to operate from long runways on land, while the F-8 was a naval fighter. <S> Higher take-off, approach and landing speed were not an issue on the F-104, so the angle of attack (AoA) was not critical. <S> On landing the '104 could also make use of a drogue chute. <S> On the other hand on the F-8 the AoA was critical because of the short, cable-arrested landings on the deck of the aircraft carriers. <S> Considering the relatively small clearance under the fuselage of the F-8, an high AoA during landing could lead to an in-flight engagement of the hook (something definitely undesirable), hence the necessity to keep the fuselage as horizontal as possible. <A> Tail clearance on take-off and landing and visibility from cockpit. <S> The aircraft needed rather high angle of attack on take-off and landing. <S> The resulting attitude would: require long gear, provide poor visibility to the pilot and make arrested landings harder, because the centre of gravity would be higher when the hook engages the cable. <S> So they chose this method of reducing the pitch. <A>
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This design feature provided more lift during low speed flight, reducing the approach speed of the F-8 during carrier landings, while providing good aerodynamic characteristics for high speed flight.
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How do redundancies work in aircraft systems? I've read about many aircraft systems having redundancies. For example, both Boeing's 787, and Airbus's A380 have a triple-redundant FCS. In this case, it makes sense to act upon the majority's decision. If all three components disagree, how is it decided which one wins? Is there any record of disagreement amongst redundant systems in airplanes? The primary differences I have compared to the question about Airbus's control systems ( How does the Airbus flight computer's voting system work? ), is verification for non-deterministic systems, as well as optics for visibility. Given that the entire systems run in parallel up until the verification component (from sensor input, onwards), there will be some, obvious delta in their "decisions." -- Although, most of the time, this isn't perceivable, is there any visibility into what's going on with the FCS? <Q> One system = <S> No redundancy. <S> Two systems = <S> Simple redundancy. <S> Three systems = <S> Double redundancy. <S> Four systems = <S> Triple redundancy. <S> However, often the term "triple redundant" is used when the system has only three members. <S> And if all three disagree, two of them must be faulty already, so this is a case of multiple failures. <S> In case of Airbus, besides the three main FCS computers two backup systems are available to help isolate the faulty one. <S> Inside, each has two channels which run software written by a different team, run on a processor different to the one in the other channel and which are supplied by two different suppliers. <S> This helps to reduce systematic errors, when all together would fail because of a common malfunction. <S> Airbus flight control system diagram (picture source ). <S> Only the first system of each is expanded; the boxes for system 2 and 3 look the same on the inside. <S> Input is from the side sticks, and output goes to the hydraulic valves at the control surfaces. <S> The voting happens first in the comparator step (between the two channels) and again in the filters (between the single systems). <A> Your question also makes the implicit assumption that redundancy involves multiple systems trying to come up with the same answer. <S> This isn't necessarily the case. <S> I've worked on a multiply-redundant hybrid electric vehicle controller. <S> These things are drive-by-wire as far as go/stop are concerned, so a lot of the same safety principles apply. <S> A primary control system ran the whole thing, managed emissions, best driver response, and all that good stuff. <S> A secondary system had a simpler model of how things should behave, checking for when the primary system was outside some tolerance of its simpler model for some time. <S> Because it was a simpler model, testing could be more complete. <S> And a tertiary system checked that the primary and secondary systems were coming up with valid behaviour, using an even simpler (and hence even-easier-to-validate) model. <S> For added fun, the secondary and tertiary systems periodically injected spurious faults and checked their fault-reporting mechanisms were detecting them correctly, so they knew a real fault would trigger correctly. <S> In this case the fallback behaviour was simply to pull the plug on the car if the primary system went dodgy, because for a car that's reasonable. <S> In principle though the secondary system could have been the basis of a perfectly competent fallback strategy if we'd thought it was necessary. <A> In general, the number of redundancy indicates the number of independent members i.e. triple redundancy indicates three independent members, while a quadraplux redundancy indicates four independent members. <S> A triple redundant system used in Flight Control Systems would look something like this: Image from A Novel Family of Weighed Average Voters for Fault-tolerant Computer Control Systems by Latif-Shabgahi et.al. <S> There are two ways the 'Voter' can determine the output from redundant systems: <S> Agreement based voting system produces an output only if a certain number (e.g. majority) of the voter inputs agree. <S> This is usually the method used in Flight Control Systems (like Airbus). <S> The other system produces an output even if there is no agreement between the redundant systems, usually by 'combining' (for e.g. averaging) selecting one of them based on some metric (for e.g. median). <S> Consider the air data input in case of Airbus: there are three Air Data and Inertial Reference Unit s. <S> The input of the 'voter' ( each flight computer) comes from all three ADIRUs. <S> The FCS needs two matching (with some allowed variation) values to generate output. <S> The Flight computers degrade to alternate law or direct law under two circumstances: <S> More than one unit fails. <S> No two units agree. <S> In case of Air France flight 447 , the FCS reverted to alternate law due to temporary inconsistency between the measured speeds (likely due to obstruction of the pitot tubes by ice crystals) of two ADRIUs. <S> The another one had already been diagnosed as faulty and excluded from consideration. <S> This and the consequent pilot actions resulted in the crash.
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Triple-redundant systems have four independent members, so if one fails, a two-to-one vote of the remaining three is still possible.
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Why do airlines have geographical names in them? Why do airlines name themselves for example "Cathay Pacific" or "Virgin Atlantic". Aren't they indirectly limiting themselves to always fly over "Pacific" or "Atlantic"? It would be weird if Virgin Atlantic flies over Pacific and vice versa. <Q> In a lot of cases it's because they started serving a specific region. <S> Lucky tells the story of Cathay Pacific. <S> Virgin Atlantic was started specifically to fly from Britain across the Atlantic . <S> Lots of US airlines started in a specific region, like Southwest. <S> Westjet started serving the west of Canada. <S> It doesn't make sense to change a well-known name just because the reach of the airline is extended. <A> The naming of an airline completely left to the investor(founder) who is registering the airline name. <S> Reason behind the naming for the one you are referring "Cathy Pacific" is Cathay, the ancient name given to China and Pacific because Roy Farrell (one of the founding member of airline) speculated that they would one day fly across the Pacific. <S> More on this can be found here . <S> There may be a reason behind the name or may not be. <S> I feel that it is not necessary to have a particular reason behind the airline naming or even other naming convention. <A> The name of a business is the business's brand name so people can identify it easily. <S> It is totally separate from what the business does, or in the case of airlines where it flies. <S> Its just a name and it is up to the owner to decide what the business is called and when (if ever) to change it. <S> The names of airlines often come from the place that the airline started operations but there is no rule saying this must be so. <S> Generally changing names of businesses can confuse customers, so it is not done very often. <S> I would think also that airlines are proud of their history <S> so that's another reason not to rename just because they created a new route.
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There is no rule stating you have to call the airline by the places it actually flies over.
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Can a fighter jet be hit by guns? Can a fighter jet travelling at fast speed be brought down by a weapon like an M134 Minigun or any machine gun? <Q> They're called SPAAG's -- Self Propelled Anti-Aircraft Guns. <S> Older systems tended to fire 23 mm shells. <S> Newer systems tend to fire 30 mm shells augmented by short range missiles. <S> They are equipped with radars and high-speed elevation and traverse motors for the turreted guns, so they can react quickly to fast a/c flying low ahead. <S> They're also useful against attack helicopters, which also hug the ground (see below). <S> These are short range weapon systems, typically only effective under 10,000 ft, the guns at much less than that. <S> They're still useful even today. <S> Medium and long-range SAM's have forced a/c to fly low, below their search and fire control radars, but within range of the guns. <S> This was standard NATO doctrine during the late Cold War--- low level penetration <S> ---and gave rise to the F-111 (for example), which was designed to fly fast and low, hugging the bumpy terrain of Central Europe. <S> This would have worked very well had the Soviets not fielded SPAAG's (basically modern AAA) and developed their own MANPADS (shoulder-fired SAM's). <S> Soviet AWACS and look-down shoot-down radar also contributed to the decline of this tactic. <S> These systems denied the use of low-level airspace so effectively that during Desert Storm, the Coalition air forces basically gave up low-level operations within the first week and switched to bombing from medium altitude exclusively (above the reach of AAA and MANPADS). <S> Not even the A-10 with its titanium armor could long survive in that environment. <S> Afterward, they did occasionally venture below 10,000 ft, but typically with special permission and enthusiastic support. <S> Even after the first week, when Iraqi air defenses were ineffective, few a/c still flew below 10,000 ft because the AAA and MANPADS were too numerous to be eliminated entirely. <S> NATO air forces are getting around this problem by buying stealth fighters, namely the F-35A, which can hide from SAM radars, allowing it to fly at medium/high altitudes, far above MANPADS and AAA. <S> But that's for another question/answer. <S> Here's an older Shilka (Vitaly V. Kuzmin - http://vitalykuzmin.net/?q=node/306 ): <S> A later Tunguska (Leonid Dzhepko / <S> Л.П. Джепко): <S> And a modern Pantsir (Vitaly V. Kuzmin - vitalykuzmin.net): <S> (All images taken from their respective wikipedia pages.) <A> Can a fighter jet traveling at fast speed be brought down by a weapon like an M134 Minigun? <S> or any machine gun? <S> There are machines guns designed to bring down cruise missiles and jet fighters but they look like this: <S> see: <S> The Phalanx CIWS close-in weapon system for defense against anti-ship missiles. <A> Phil Handley shot down a MIG19 while his F4 was going supersonic (around Mach 1.2), after both the AIM7 Sparrow and AIM4 Falcon missiles had failed to launch correctly. <S> Admittedly, this was a one time event, hasn't been repeated since then, but not only can a fast moving aircraft be brought down with a gun, it can be brought down by a gun fired from another fast moving aircraft. <A> During the Falklands War the British naval ships came under close attack by Argentine Mirage III jets. <S> The ships' crews would fire any weapons they could into the air to create a curtain of fire that the attacking jets had to fly through. <S> The attackers typically flew lower than fifty feet to avoid radar, so they were definitely in range. <S> In fact, they were so low on the flight across the South Atlantic that their visibility was hampered by spray flying up off the waves. <S> Reputedly, at least one aircraft was brought down this way, but I haven't yet found confirmation. <S> Nevertheless, it's perfectly possible that with enough lead or a lucky shot one could hit some vital component (like the pilot) and garner a kill. <A> <A> 7.62 mm machine guns are not usually considered adequate for air defence, but are used when nothing better is available. <S> During the Korean war (1950-53) <S> the .50/12.7 mm projectiles fired from the M3 machine guns of the F86 Sabre proved less effective against the MiG 15 than was desirable, frequently deflecting off without causing damage at shallow impact angles.
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Records suggest that jet fighters are not brought down by hand-aimed bullet-firing weapons.
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What is the requirement of a higher glidepath/approach angle and is this a flight safety issue? To reduce noise in the London urban area, Heathrow airport has announced plans to trial a steeper approach for aircraft landing - changing from 3 to 3.2 degrees. If this is successful, they will further steepen the landing approach to 3.5 degrees. Moreover, London City airport uses a 5.5 degree landing approach. What are the requirements of higher angle landing approaches and how do they affect flight safety? <Q> The most important sources of noise in an aircraft (especially during landing) are the engines, the slats/flaps and the gear. <S> An aircraft’s angle of descent has an effect on the noise experienced by people below. <S> Steeper the angle, the less time an aircraft spends at low altitudes, which means that fewer people should be affected by higher levels of noise. <S> The reduction in noise (as experienced in Frankfurt airport ) due to steeper (3.2$^{\circ}$) landing approaches are due to the following: <S> The aircraft is higher (compared to the 3$^{\circ}$ landing angle), and as a result, less noise is heard by the people below. <S> The deployment of flaps before intercept may also be 0.7 nm closer to the airport as the ILS intercept occurs 0.7 nm closer to the airport. <S> Thrust increase for a/c stabilization 0.3 nm closer to the airport; this results in lower noise. <S> The thrust required was also reportedly lower. <S> Landing gear deployment is 0.4 nm closer to the airport (at the same height of 2000 ft) <S> The differences due to changing the glideslope to 3.2$^{\circ}$from the present 3$^{\circ}$ is shown in the following image: <S> Image from Experience with the steeper approach angle of 3.2 degrees - Presentation by DLR <S> As for safety, this system is expected to pose no problems as most aircraft and pilots are easily capable of doing this. <S> As an added measure, the trial is only being carried out when visibility is good (Cat I) and the trial is optional (for aircraft using ILS anyway). <A> Since the forward speed is determined by required lift, steeper approach path means higher vertical speed. <S> Considering approach speed of 130 knots: <S> at 3.0°, which is 5.2% or 1:19.1, the vertical speed is 690 ft/min, at 3.2°, which is 5.6% or 1:17.3, the vertical speed is 736 ft/min, at 3.5°, which is 6.1% or 1:16.3, the vertical speed is 805 ft/min and at 5.5°, which is 9.6% or 1:10.4, the vertical speed is 1268 ft/min. <S> Since normally the criteria for stabilized approach is that vertical speed does not exceed 1000 ft/min, the 5.5° requires different procedure with different criteria. <S> Vertical speed equals power ( $P = <S> mgv_v$ <S> where <S> $m$ is mass, <S> $g$ is gravitational acceleration and <S> $v_v$ is vertical speed) and to maintain speed, the engines have to develop less power by this amount, or drag has to be increased. <S> This is usually not a problem for propeller aircraft, especially those with variable pitch propellers (which turboprop requires and larger piston-engined aircraft have as well). <S> With maximum RPM selected the propeller produces quite a lot of drag at idle, but since everything is already spinning fast, adding power has immediate effect if needed to go around. <S> It may, however, be problem for jet aircraft. <S> Jet engines need to spool up to increase thrust and from very low power settings that can take several seconds. <S> The normal glide-slope is well below the gliding angle with no power (with flaps and gear), so the engines are still running at considerable power. <S> In the slightly steeper approaches the power is less, but the difference is not as big, so it usually isn't a problem. <S> But the 5.5° steep approach is getting close to the unpowered glide angle even with full flaps and gear and is steeper than unpowered glide angle with lower flaps settings. <S> This means the engines will react more slowly and pilots have to consider it. <S> Also in some aircraft an engine-out approach can't be flown at full flaps, because the remaining engine(s) would not have enough power for go-around at that drag, which means such aircraft can't fly steep approaches with failed engine. <S> And some aircraft may not be permitted to do these steep approaches at all, because even at full flaps the engines would run too slow and take too long to spool up. <A> What is the requirement of higher angle landing approach? <S> Is basically requiring the aircrafts to stay at higher altitudes for longer and approaching the ground faster. <S> The normally used term is " glideslope ". <S> how does it affect flight safety? <S> The airport authorities will have performed a safety assestment and decided that this change would not sensibly affect flight safety. <S> What will change is how the pilots will have to perform the flare manoeuver (a bit more sharply than before) and for unexperienced students might lead to a higher rate of hard landings, but I doubt that there are many student pilots landing with airliners at those airports.
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Some airports (like London City) have very steep landing approaches for clearing obstructions and may require special certifications and aircraft modifications.
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Why do the Lycoming HIO-360 A1A and IO-360 engines produce different power? I have just acquired an aerobatic aircraft fitted with a Lycoming HIO-360 A1A. Reading the specs on the engine I see it has the higher (8.7:1) compression of the 200hp IO-360 engines, which seem mainly to make that power at 2 700 rpm, but this one actually makes the same power (180 hp) of the 8.5:1 carburetter engines, but at higher rpm (2 900) than they turn. This was a helicopter engine originally which I think accounts for the higher rpm rating, but it seems to me wholly counter-intuitive that an engine with the same swept volume, fuel injection for greater efficiency AND more revs would make - relatively - so little power. Can anyone explain this? <Q> Helicopter engines have different operating parameters than aircraft engines. <S> They operate in a narrower power band and the difference in horsepower would be due to camshaft lift and duration optimized for that power band. <A> While engines of the same size may have different ratings for a host of reasons, the FAA rules (14CFR33) for rating the power of a helicopter engine are much more demanding than those for rating an airplane engine, and it has nothing to do with SAE. <S> Specifically, the endurance test for certifying rated power is more stringent. <S> Both sets of rules require 150 hours of sustained running (servicing allowed) and alternate between periods (mostly 1.5-2.5hr) of rated speed/power and reduced speed/power. <S> The average reduced power for helicopters is 71%, for airplanes it is 64% <S> The average reduced speed for helicopters is 71%, for airplanes it is 84% <S> The speed range for helicopters is 30% to 110%, for airplanes it is 79.5% to 100% <S> The helicopter rules require a sustained 15hr run at 105% of continuous rated power and speed, and has 12.5hrs at 110% speed. <S> There is no similar requirement for airplane engines. <S> An airplane engine spends half of its time at reduced speed, a helicopter engine spends 15hrs more at rated power than reduced power. <S> Helicopters must produce more power under a wider variety of more difficult test conditions: 71% power at 71% speed is 24% harder on the engine than 64% power at 84% speed. <S> Consequently, a helicopter engine that is internally exactly the same as an airplane engine will be rated 5-10% lower in power at 5-10% higher in speed. <S> The helicopter version of similarly rated engines will be beefier than the airplane version. <A> The Lycoming HIO-360 is a horizontally-mounted version of the IO-360. <S> (H for Horizontal). <S> It reaches its power band peak and has a lower peak at different RPM for that reason. <S> This is often the case when you work against gravity / work with gravity. <S> (IO-360-J2A for the Robinson R22 for example). <S> These are further derated because of the weaker cylinder walls. <S> Note that there is no H designation here because a)H is for horizontal and this is not one, and b)H is NOT for helicopter :) <S> E <A> Those power rating explanations in other answers are incorrect. <S> The Helicopter engines are rated at a lower horsepower at a higher RPM because they cannot accept the SAE "5% less than rated is acceptable" rule. <S> The power rating must be correct, and is set at an altitude above sea level, for example, 1500' ASL. <S> This is easily understood when you look at the engine operator's manual. <S> I have an IVO-360A1A from a Brantley B2B Helicopter modified to fit in my RV-8. <S> It's a parallel valve engine, 8.5:1 compression ratio, rated at 180 HP @ <S> 2900 <S> RPM. <S> It has a TBO of 1000 hours. <S> It had a huge oil cooler and it also has oil lines that extend from the oil galleries on the engine block to the exhaust valve guides, where oil flows into the head, around the outside of the exhaust valve guide and drains into the valve chest to cool the head. <S> That is because helicopter engines work very hard and run very hot. <S> Internally they are nearly identical to aircraft engines, and use the same parts. <A> Reciprocating light helicopter engines are derated to allow for out of ground effect (OGE) hover at an altitude above sea level. <S> To the best of my recollection the R22 is limited to a manifold pressure of 25 inches. <S> This allows for rated power to be achievable at roughly 5000 ft. altitude.
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Some helicopter engines are designed with thinner cylinder walls for lighter weight.
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Are airliner flight plans/routes preset? KLM has 3 flights daily from BLQ to AMS. How do all of the crews handle the flight plans? Do the make a plan for every flight every day or do they have a database in which preset and stored flight plans are available and are ready to be extracted? <Q> Airlines have an own department that is solely responsible for their flights and flight plans: Dispatch . <S> The flight plan is usually submitted by the dispatchers and not the aircrew. <A> Most airlines will have predefined plans, which can be modified as needed (for example when there are NOTAMs). <S> And newer aircraft may even have a standard list of plans preprogrammed in their FMCs, again modifiable of course. <A> They are called company routes. <S> They are customised for an airline and added to a section of the monthly Navigation Database the FMS manufacturer sells to each airline. <S> Flight plans can also be uplinked by the airline operation center to the FMS. <S> Both of these the pilot can select into the active/primary flight plan.
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Since single airways can have different availability or just direction for different days or even times of the day, there will be a preset pool of routes for recurring flights, which can then be adapted for anything out of the ordinary, like NOTAMS, weather forecasts, operational requirements like airspace closure, etc...
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When is a fuel pump needed on GA aircraft? When is a fuel pump needed on GA aircraft? I am a flight simmer and have noticed that you can leave the fuel pump off and start/fly the aircraft. When would you use the fuel pump? <Q> On a low wing monoplane you'll need a pump all the time. <S> There will be a mechanical pump fitted to the engine for the purpose. <S> On a high-wing monoplane the engine is often gravity feed. <S> However, during critical phases of flight (specifically take-off and landing) you wouldn't want to have that fail <S> so a second auxiliary electric pump is fitted that the pilot switches on beforehand and can switch off once that phase is over. <S> The Pilot's Operating Manual will give specific recommendations for use on any given type. <A> Refer to the POH for the aircraft but in the PA-28-161 I fly the electric fuel pump is used on take off, landing, and while practicing maneuvers like steep turns and stalls. <S> Most GA planes are configured with either a gravity feed fuel system (like the Cessna 172 ) or an engine driven fuel pump ( Piper Cherokees ) that can be supplemented with an electric fuel pump should it quit or become partially inoperative. <S> The FAA has a nice document on it here (see pump feed systems ) <S> their opinion is, The engine-driven fuel pump acts as the primary pump. <S> The electric pump can supply fuel should the other fail. <S> The electric pump also supplies fuel pressure while starting and is used to prevent vapor lock during flight at high altitude. <S> The switch you see in the cockpit controls the electric pump. <S> As far as I know there is no way to turn off the mechanical pump (not that you would really want to). <S> The general startup procedure for carbureted PA-28's (low wing mono planes (fuel tank below engine)) often involves turning the fuel pump on, checking for fuel pressure, then turning the pump off. <S> This can also help to prime the lines with fuel, if the lines are dry you will need a few extra cranks of the engine to draw fuel in with the mechanical pump which drains battery power. <S> Since you claim you can fly with out the pump running we can assume it is an engine pump driven plane however smaller turbine planes that still fall under the GA header may require an electric fuel pump to feed the engine. <A> Virtually all GA aircraft, high or low wing, use both an engine driven fuel pump and and electric auxiliary fuel pump. <S> The aux pump is used on low wing aircraft, both for priming the engine as well as a backup in critical phases of flight where EDP failure could be disasterous such as takeoff and landing. <S> This is due to the low wing arrangement requiring siphon feed from the tanks to the engine.
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Typically high wing GA aircraft will use the aux pump only for priming the engine (fuel injected engines) as gravity feed from the main tanks offers a backup in case of EDP failure.
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What is the chime that can be heard roughly 30 seconds after takeoff? This may be confirmation bias on my part, this might be impatient passengers pressing the call button, and it might be me imagining things, but it's one of those I've wondered about. I'll try to describe as best I can. Of all the times I've flown recently on an airliner, of which most of the time it's a short haul carrier often flying smaller Boeing/Airbus aircraft*, I have been aware that there is an audible chime which can be heard throughout the cabin (ie, not only when sat in the vicinity of crew seats) very soon (30-45 seconds) after take-off. It is heard well before the passenger seat-belt signs are switched off. Can anyone describe what I am hearing and what its purpose is? Who is this a signal for, and who is sending the signal? * the two times I've flown on an Embraer I don't recall hearing it <Q> It's signalled from the cockpit (the cabin chime) to let the cabin crew know it's OK to move around. <S> If you watch, this happens before the seat belt sign goes off which at the earliest, is at 10,000 feet. <A> The chime shortly after takeoff is triggered when the landing gear is fully retracted and the gear doors are closed. <S> (Depending on where you are sitting, you can probably hear or feel it moving. <S> If you’re downstairs in the pointy end of one of our Boeing 747’s – you’re basically sitting right on top of the front landing gear). <S> https://www.qantasnewsroom.com.au/roo-tales/cabin-crew-lingo-101/ <S> I've heard that on virtually all A320 planes that I've flown on (AirAsia, Cathay Dragon, HK Express), a few seconds after the plane is airborne. <A> To be precise, on the Airbus, the chime comes on after the emergency exit signs are turned off. <S> In the Airbus Normal Procedures, the Emer Exit Signs are set to Auto, meaning the Signs would turn off after the LG are up and locked. <S> So it is not a chime to inform the cabin crew that the gears are up and locked, but a chime that sounds when the Emer Exit Signs are turned off. <A> There is no automatic chime on a Boeing! <S> Any chimes heard immediately after takeoff will likely be the cabin crew using this “dead” time (unproductive time prior to the extinguishing of the seat belt light by the captain) to start coordinating service details.
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On our Airbus aircraft you’ll hear the ‘boing’ sound shortly after take-off – this sound lets crew know that the landing gear is being retracted.
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Why do winglets reduce maneuverability (of fighter jets)? In this answer Ethan makes the following statement concerning winglets on fighter jets: [Winglets] reduce maneuverability which is why you don't see a winglet on a fighter jet I could image that adding more weight at the end of the wings increases inertia, reducing maneuverability, but I'm not sure if this is the only reason. Perhaps there is some aerodynamic phenomenon at play as well? <Q> Your observation about roll inertia is correct: Winglets add proportionally more roll inertia for their small increase in L/D, and this increase exists only for the higher range of lift coefficients. <S> At low lift coefficients (think cruise), when the induced drag is low, they add more friction drag and reduce the L/D overall. <S> There are three aspects to maneuverability: <S> How quickly can you accelerate into a roll? <S> Here the added inertia of winglets reduces roll acceleration <S> How high is the maximum sustained turn rate? <S> This is determined by the maximum lift at zero sink rate, and here winglets are helping. <S> Especially when mounted to low aspect ratio wings. <S> How high is the maximum turn rate? <S> Now only lift counts, and the increased drag is compensated by an increased sink rate. <S> Again, winglets help a little, but less than with the sustained turn rate. <S> Now look at the time any fighter will spend around 1g <S> (hint: Something close to 100%) and how much is spent at high lift coefficients, like when turning tightly in air combat. <S> Winglets would help in the turn (and I think Ethan's opinion is wrong), but be a source of drag for the rest of the mission. <S> Adding winglets would require to increase the fuel volume to prevent a reduction in flight time and range. <S> Normally, winglets are only used on highly loaded, high-aspect ratio wings when their L/D at a rather high lift coefficient needs to be pushed up even more. <S> Highly maneuverable configurations are less concerned with single-percentage increases in L/D for a small part of the flight, and in order to improve turn performance, increasing wing span is much more effective. <S> But that increases roll inertia and roll damping, so fighters use low-aspect ratio wings and compensate their higher drag in a turn with more powerful engines. <S> Note that the trend in fighter aspect ratios went down with the improving thrust-to-weight ratio of jet engines. <S> Now that is the reason why you don't see winglets on fighter jets: They would lower L/D for most of the flight. <S> To perform the same mission, the fighter without winglets can be made smaller. <S> But let's make no mistake: Low aspect ratio configurations gain the most from winglets <S> : They were essential on the Hermes re-entry vehicle project to give it enough L/D for a successful flare. <A> The effects of winglets on the maneuverability of aircraft is not straightforward, with different effects on various maneuverability parameters. <S> In the simplest sense, the winglets have the effect of increasing the aspect ratio of the wing. <S> This results in lower roll angular acceleration as a higher moment of inertia needs to be overcome before the movement begins. <S> The roll rate (at maximum aileron deflection) is slightly greater with winglets, as they increase the local span loading near the wing tips, thereby augmenting aileron effectiveness. <S> This means that smaller aileron deflections are required for a given rolling moment; meaning less drag for a given roll rate and a higher maximum roll rate. <S> As the winglets increase the L/D ratio, the climb performance is improved. <S> There are other reasons for the absence of winglets in combat aircraft, such as: <S> For example, the winglet increases profile drag while reducing induced drag; in conditions where profile drag is a major contributor to the total drag, this is a disadvantage. <S> The winglets will have disastrous effect in supersonic flight due to the added drag. <S> The thin winglets are prone to flutter problems. <S> Winglets will add considerably to the radar signature from the most critical angles. <A> An unsung property of winglets is that they improve yaw stability, which can actually reduce drag, especially for designs which require yaw damping. <S> Going back to the days of the Sopwith Camel, fighters benefit from instability to turn more effectively. <S> While today's fighters have computers to make them safer, the Camel was very challenging to fly. <S> Contrary to some opinion, winglets are not a "drag disaster" and were very sucessfully used on the XB-70 design (folded down) to increase the lift coefficient of the delta wing, allowing it to fly at a drag saving lower angle of attack.
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Winglets are optimized for a particular configuration of wing, flight speed and profile and are usually ineffective, and may even have adverse effects on aircraft performance in other situations.
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What is the primary means of IFR navigation for private pilots? I have been doing a lot of reading into IFR navigation, and have been looking at the various instruments and systems that are used. I am going to exclude GPS here, as I have been focussing on some of the more 'old-school' methods. My question is, if a private pilot decided to fly their GA aircraft from A to B, lets say a distance of 500nm, what IFR systems would they use to navigate? My first answer myself would be VOR, but the range seems to be a limiting factor. For example, high altitude VORs have a maximum range of roughly 130nm ( http://flighttraining.aopa.org/magazine/2000/December/200012_Features_The_ABCs_Of_VORs.html ). If we were flying between two major cities, this wouldn't be an issue, as I would expect plenty of stations to track to on the way, but what if I was flying between two airports where the VOR stations were positioned 300nm apart? Is this sort of IFR navigation only possible with GPS? Thanks in advance. <Q> There are numerous options, and it depends highly on your route. <S> But there are generally enough VORs scattered across the country such that you should be in range of a couple of them pretty much everywhere. <S> As mentioned in another answer, there are NDBs, but in the continental US, generally, the ones not on an approach are getting fewer, as the FAA has followed a path of not repair them once they break. <S> Other parts of the world, still use them and there are also NDB based airways(AIM has examples for how they can be charted on US charts). <S> If you had to plan a flight from a field that doesn't have a navigational fix, and you don't have GPS, you'd start by looking for airways near where you are. <S> Once you find some that go in the general direction you want to go, you start figuring out intersections near that or how you plan to intercept the airway. <S> Then you end up most likely planning a zig-zag course following airways towards your destination. <A> In the UK I generally use VORs where possible, then NDBs, then good old dead reckoning. <S> GPS spoils the fun!... <S> and besides the planes I regularly hire are at a flight school and each has a different GPS installed (or in one case no GPS at all). <S> You "program" a VOR radio in pretty much the same way in all planes (or at least all of the ones I fly), but I reckon trying to remember what random combination of buttons, twists and presses I need to enter a route on each system is far more likely to end in a mistake. <S> For example to get from my local field to our nearest GA-friendly airport with an ILS is 2 VORs then an NDB (located at the ILS airport, and forms part of the procedural ILS). <S> I only use for dead reckoning for short legs, like getting through gaps in airspace around London - e.g. track outbound on from VOR to 8DME, then heading x for 7 minutes, then heading y until you intercept the z track onto an NDB]. <S> I guess if you're in an area with very sparse VOR coverage you probably have less airspace issues, so less need for accuracy (terrain issues notwithstanding - <S> but the higher you are the further the reception). <S> In that case longer-distance dead-reckoning may get you between VORs. <S> I also have an app on my iphone which warns if I'm about to bust controlled airspace, but that breaches your "no GPS" question :). <S> Technically you can use "VDF" too in the UK <S> (i.e. some airports can tell you your bearing from radio transmissions), although I've not tried that myself. <A> Of course, VOR/DME, GPS/GNSS and radar (by ATC) can also be used.
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You can use Automatic Direction Finder (ADF) along with Non Directional Beacon (NDB).
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Could bypass air be used to cool a rocket engine like in turbofans? Rocket engines typically employ a cooling jacket of sorts, usually dual-purposing the fuel as a liquid coolant before it flows into the injectors. Here is an example turbojet using a bypass. As you can see, the bypass air is far cooler in temperature than the air combustion chamber: Source Why are there no designs that use an air bypass (similar to a turbojet) to cool the engine/nozzle? Obviously once the rocket has escaped the atmosphere, a bypass would be of little use. However usually by that stage in a rocket, thrust has been greatly reduced and therefore generated heat as well. Wouldn't a bypass cooling system make a rocket engine a tad less complex (especially for the first stage)? <Q> Air cooling is not going to contribute much here. <S> The Shuttle engines were cooled by liquid hydrogen (-253°C) from the fuel supply being pumped up cooling ducts inside the nozzle. <S> Typical nozzle temperature in operation was around 54°C. <S> Yes, fifty-four Celsius. <S> (BBC Engineering Connections - see this Youtube clip ) <S> The top speed of the SR-71 (about Mach 3.2) was limited by the temperature of the air arriving at the engines which, after being compressed in the inlet ducts, reached temperatures around 400°C. <S> ( Wikipedia: SR-71 ) <S> The shuttle passes Mach 4 about 2 minutes after launch. <A> Virtually all jet engines use a technique very similar to the technique you're proposing: the inside of the combustion chamber, turbines, and exhaust, (and afterburner, if the engine has one) as well as the turbine blades and stators, are covered with small holes. <S> Cooling air is forced through these holes, forming a boundary layer between the metal and the super-hot gases. <S> The temperature of burning fuel/air in a jet engine is well above the melting point of the metals used to build these components, which is why this is necessary. <S> In fact, the temperature of the gases exceeds the vaporization temperature of a number of metals. <S> Where does this cooling air come from? <S> It comes from the engine's compressor. <S> In this case, the boundary layer is made of hot gas instead of cool gas, which destroys the engine. <S> To get air of adequate pressure, air is "bled" out of the compressor at points where the pressure is high enough to provide adequate flow (in the right direction!) <S> to the parts of the engine that need it. <S> This method of cooling is so effective that the components in a jet engine that need to withstand the most heat are actually the highest pressure parts of the compressor, because (a) air heats up when you compress it, and (b) you can't use the same cool boundary layer technique in the compressor because you need higher pressure air than the hot air from which you're trying to protect the component, and the component is part of the highest-pressure part of the compressor. <S> Here's a picture of a jet exhaust guide vane, with cooling holes clearly visible: <S> On a rocket engine, you could potentially cool it with compressed atmospheric air, but doing would add weight and complexity, and would only work in the lower layers of the atmosphere where there's enough air density to provide an adequate mass flow rate to absorb the heat. <S> Since, as you mentioned, fuel (or potentially oxidizer) can be used to effectively cool the engine for a much lower penalty in weight and greater freedom in operating environment, that's been the obvious choice for most high-performance liquid fueled rockets. <A> The air augmented rocket <S> uses air from the freestream to provide extra thrust (and potentially) <S> cool the motor. <S> Two of the main issues with trying to add 'extra' air into the rocket stream are: drag over the rocket body (pretty much the main one) and disruption of the high-temperature flow (especially if you are trying to introduce air somewhere around the nozzle). <A> Two main reasons: Firstly rockets operate at a preposterous level of power - the fuel and oxidiser pumps alone on a space shuttle have a combined shaft power greater than a GE90 turbofan - so you'd really struggle to get enough airflow, liquid hydrogen is a far better heatsink especially in the quantities they use. <S> Secondly, most rockets are built with the intention of going to space, where there in no cooling air at all, so as you got higher and the air got thinner your air-cooled rocket would rapidly overheat.
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The reason bypass air isn't used is because it is at a lower pressure than the inside of the core of the engine, so the hot gases would move out through the holes toward the bypass duct.
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Who flies planes on ferry flights? Two questions regarding ferry flights: When an aircraft has to be delivered, who flies it to the destination airport? Does the manufacturer have a dedicated crew for this or is it up to the airline to send someone over? When an aircraft is sent to Victorville (Southern California Logistics Airport), who flies the plane? Is it a dedicated airline crew or is it a contracted-out service? Thanks! <Q> Ferry flights encompass much more than delivery and retirement flights. <S> Any time an airplane has a problem that can't be fixed on-site they can generally obtain a ferry permit to get it to an airport that the maintenance can be completed at. <S> I'm familiar with have the same requirements in their contract language. <S> Our airplanes were manufactured in Brazil and a crew would be take an airline flight down to the Embraer factory, accept the airplane and fly it to a US customs station and then on to our main maintenance airport. <S> These flights were fairly uncommon and often went to very senior and management pilots. <S> In all cases though, at my airline, ferry flights were conducted by company pilots. <A> Usually, ferry and delivery flights have different meanings. <S> It differs from aircraft to aircraft. <S> In case of new commercial aircraft, the delivery team from the airlines are sent to the manufacturer, where they accept and bring the aircraft to the airline location. <S> The delivery procedure of Airbus is as follows: <S> The delivery phase is spread over four or five days on average, dependent upon the aircraft programme. <S> A standard delivery procedure takes place as follows: 1st day: ground checks: external surfaces, bays and cabin visual inspection, static aircraft system and cockpit checks, engine tests. <S> 2nd day: acceptance flight: checks during flight of all aircraft systems (including cabin systems) and aircraft behavior in the whole flight envelope. <S> 3rd day: physical rework or provision of solutions for all technical and quality snags open in delivery. <S> 4th day: completion of technical acceptance. <S> Technical closure of the aircraft and all associated documents attesting the aircraft’s compliance to the type certificate and conformity to the technical specification allowing the issuance of the Certificate of Airworthiness. <S> 5th day: transfer of the aircraft's title deeds to the customer airline: the aircraft changes owner. <S> Preparation of the aircraft for the ferry flight to its home base. <S> For GA, ferrying is done by ferry pilots . <S> There are also some companies that perform these services for small airlines etc. <S> A ferry flight usually refers to the positioning of aircraft for maintenance, repair etc. <S> This is done by the pilots of the airlines usually, with a special permit (i.e. the aircraft is not airworthy, but is flyable). <S> As noted before, this can also be contracted out. <S> For military aircraft, it is done by the service pilots. <A> All the new aircraft deliveries I have been involved with were done by the buyer or the leasee. <S> The normal process involves a physical inspection of the aircraft, paperwork, accessories, making sure the correct documentation is in hand, as well as one or more test flights to assure aircraft performance. <S> In every delivery I have accepted, there is usually a squawk list, and the manufacturers are great at performing seeming miracles overnight. <S> It is not uncommon that there is a couple of days of squawks. <S> I often invite a factory test pilot along on the flights, as that helps identifying issues. <S> Some of the things I check include the rigging and trim of the aircraft, the power plant performance, the radio installations (which can require some coordination when picking up a plane mid-continent and testing HF), the autopilot systems, and the ECS. <S> Funds are transferred and paperwork is filed, and a flight to the destination is accomplished. <S> Normally close fuel and power plant monitoring is done for that flight, and things like WX radar, strike finders and other avionics are extensively run. <S> If we don't have someone who has significant experience in the aircraft, we take training at a place like Flight Safety, in a simulator. <S> Training is normally classified as initial or recurrent. <S> The training outfit can tailor the training to include the specific equipment and engines that are included in the delivered aircraft. <S> The bulk of the aircraft I have personally accepted of delivery on are turboprops and jets, but it also includes a few piston aircraft. <S> Some local flight schools, charter and FBOs have hired me to accept delivery of aircraft for them. <S> In my opinion the acceptance of new aircraft is more than just kick the tires and ferry the aircraft. <S> It is a through systems checkout, and verification that all documentation is in place, cosmetics are good, and so, <S> verifying that the end user receives a plane which is unlikely to have any issues, and that it performs as advertised.
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At the airline I worked for, all flights, including initial delivery, were conducted by pilots on our seniority list and other airlines Normal ferry flights for aircraft repositioning or maintenance needs were generally done by low-seniority reserve crews because those tended to be non-scheduled activity and show up with short notice. This can vary by airline and there probably isn't a universal definitive procedure common to every airline.
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How is the amount of time for an A check or daily maintenance determined? How can the time for daily maintenance or A Check be calculated for different aircraft types? Is there any exact formulation depending on the aircraft specifications? P.S.,I'm very new to the aviation field. <Q> This answer is not specific for A-checks, but covers the whole maintenance effort. <S> Try Eddins-Earles, Mary: Factors, Formulas and Structures for Life Cycle Costing, Eddins-Earles, 89 Lee Drive, Concord MA 01742, USA, 1981 <S> It's a bit dated, but has a wealth of data. <S> Another source would be Fabrycky, Wolter J.; Blanchard, Benjamin S.: Life-Cycle Cost and Economic Analysis, Prentice-Hall International. <S> ISBN 0135383234. <S> Also, the white volume (I think it is No 8) of Jan Roskam's collection is a good start. <S> Roskam, Dr. Jan: Airplane Design, Roskam Aviation and Engineering Corporation, Ottawa, Kansas 66067, USA, 1990. <S> Generally, this is not exact science, so exact times cannot be expected. <S> With experience, each operator will be able to estimate how long things take, but you do these checks to find possible damage which needs to be taken care of. <S> A lot depends on the training and experience of the maintenance crew. <S> The best way to approach this is with statistics. <A> The time taken for the daily maintenance or 'A' checks (or any other checks for that matter) depends on a number of parameters like: <S> The aircraft configuration. <S> The experience and skill level of the aircrew. <S> The condition (or age) of the aircraft and its components. <S> Requirement of any special checks (whether manufacturer/regulator mandated or operator requirement) <S> Usually, the checks to be carried out during each schedule (hourly or calender based) are determined by the manufacturer (sometimes in co-ordination with the operator) and laid down. <S> One thing to note is that this is not exact and will vary based on a number of factors. <S> For the same checks, different operators (and manufacturer) may allot different time periods. <S> If two different checks (for e.g. airframe and the engine) are required to be carried out at the same time, the time required will differ. <A> To answer your first question: The manufacturer (OEM) usually publishes an estimate of maintenance man-hours (MH) needed for each task within their Maintenance Planning Document (MPD). <S> For non-MPD tasks, source documents such as Service Bulletins usually also have an estimate. <S> When an A- or C-Check work package is created, the OEM's estimates for each task can simply be added up to get a rough idea of the total number of MH needed. <S> HOWEVER: this is just an estimate! <S> The OEM's figures assume that the work is being carried out in ideal conditions, i.e. the tools are all at hand; paperwork is printed out; access to the aircraft is readily available; and the mechanic is well versed in doing that task. <S> The OEM's estimate therefore needs to be adjusted. <S> I've seen various organizations use factors varying between 2 to 4 i.e. if the OEM says one hour, you plan for between two to four hours. <S> Once the total MH for the A- or C-Check package is calculated, you can get a rough estimate of the ground-time you'll need for the check, based on the manpower you have available. <S> HOWEVER, a word of caution! <S> As Peter says, this is not an exact science! <S> Remember that the number of MH is different from the actual time it takes to do the task (known as "elapsed time")... <S> E.g. time for a sealant to cure doesn't count towards the MH, but does still need time in the real world. <S> Remember, just because a woman can deliver a baby in nine months, doesn't mean nine women can deliver a baby in one month! <S> Ideally, the company should have a process in place to gather and analyze data on planned MH vs utilized MH and planned vs utilized ground-time and incorporate this into their production planning activities. <S> The calculations based on the OEM's MPD and source documents provide a ballpark figure, to which you then need to apply your engineering judgement and experience. <S> This is where data gathering and analyses can be invaluable to an organization's planning process.
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The time required is then calculated by actually timing the operations and adding correction factors or by statistical analysis over a period of time. The factor will typically vary depending on factors such as:- facilities / equipment available at the maintenance location;- experience and skill levels of the technicians;- age and condition of the aircraft;- and even the type of check (e.g. A-Check vs C-Check). To answer your second question: As can be seen above, there is no "exact formulation".
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What is the thick, dashed, magenta line on a sectional chart? In the attached area of the sectional chart we see restricted areas R-2101 and R-2102. Also covering that general area is a circular, thick, dashed magenta line. There's a notice there that I assume corresponds to it, but I wasn't familiar with this marking before I saw it. I glanced at the Aeronautical Chart User's Guide but didn't see a reference. Anyone know what's happening here? <Q> The Atlanta sectional near KANB, KASN, and KPLR gives a hint: <S> FOR REASONS OF NATIONAL SECURITY PILOTS ARE REQUESTED TO AVOID FLIGHT AT AND <S> BELOW 5000’ AGL IN THIS AREA <S> It is called a National Security Area , which FAA’s training ALC-42 <S> : Airspace, Special Use Airspace and TFRs describes as follows. <S> National Security Areas National Security Areas consist of airspace of defined vertical and lateral dimensions established at locations where there is a requirement for increased security and safety of ground facilities. <S> Pilots are requested to voluntarily avoid flying through the depicted NSA. <S> When it is necessary to provide a greater level of security and safety, flight in NSAs may be temporarily prohibited by regulation under the provisions of 14 CFR Section 99.7 . <S> Regulatory prohibitions will be issued by System Operations, System Operations Airspace and AIM Office, Airspace and Rules, and disseminated via NOTAM. <S> Inquiries about NSAs Inquiries should be directed to Airspace and Rules. <S> Example — National Security Area near Pueblo, Co. and request to avoid flight at and below 3000’ AGL. <S> Wikipedia gives a brief description . <S> In United States aviation, a National Security Area is a designated airspace through which flight is discouraged for reasons of national security. <S> Flight through NSAs is not prohibited and no special advance clearance or authorization need be obtained to enter them. <S> However, pilots of aircraft are strongly encouraged to either stay clear of NSAs or obtain prior authorization to pass through them in order to reassure the controlling agency that no threat to national security exists. <S> NSAs are a compromise between normal airspace and restricted or prohibited airspace. <S> NSAs can be temporarily converted into restricted airspace by NOTAMs. <S> On VFR sectional charts, NSAs are delimited by a heavy dashed magenta border and a special notation. <A> The thick dashed magenta line indicates a National Security Area. <S> National Security Areas indicated with a broken magenta line national security area dashes and Special Flight Rules Areas (SFRAs) indicated with the following symbol: sfras , consist of airspace with defined vertical and lateral dimensions established at locations where there is a requirement for increased security and safety of ground facilities. <S> Pilots should avoid flying through these depicted areas. <S> When necessary, flight may be temporarily prohibited. <S> The answer is in the Aeronautical Chart User's Guide , I just initially overlooked it. <A> National Security Area. <S> ( source ) <A> Here is the description from the guide: <S> National Security Areas indicated with a broken magenta line and Special Flight Rules Areas (SFRAs) indicated with the following symbol: , consist of airspace with defined vertical and lateral dimensions established at locations where there is a requirement for increased security and safety of ground facilities. <S> Pilots should avoid flying through these depicted areas. <S> When necessary, flight may be temporarily prohibited.
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Apparently there are "National Security Areas" which are marked with a dashed magenta line.
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Why do the Cirrus SR-20 and SR-22 have the CAPS (parachute) system? Cirrus touts the parachute as an added layer of safety. The parachute has obvious marketing value, but is the parachute's added safety a spin on the airframe's shortcomings? CAPS is not an option when buying a Cirrus, so what's the real reason for it? Why do the Cirrus SR-20 and SR-22 have the CAPS parachute? Can a Cirrus SR-20 or SR-22 be certified to fly without it? <Q> Briefly, without the CAPS the aircraft could not be certified because it wouldn't meet the spin recovery requirements of 14 CFR 23.221 . <S> You can read a lot of detail in Cirrus's own CAPS Guide but their design premise is that pilots are bad at recovering from spins, especially close to ground. <S> Normally, the Cirrus would have to comply with 14 CFR 23.221(a): <S> Normal category airplanes . <S> A single-engine, normal category airplane must be able to recover from a one-turn spin or a three-second spin, whichever takes longer, in not more than one additional turn after initiation of the first control action for recovery, or demonstrate compliance with the optional spin resistant requirements of this section. <S> But, rather than comply directly by demonstrating the spin recovery, Cirrus asked the FAA to certify them based on the wing design and CAPS instead, as the CAPS Guide explains: Given that Cirrus had demonstrated enhanced low speed handling characteristics that will help pilots to avoid inadvertent spin entry and the presence of CAPS, the FAA granted Cirrus an Equivalent Level of Safety (ELOS) for the spin recovery requirement of the certification regulations. <S> This ELOS is accepted by all civil aviation authorities that have certified the Cirrus SR20 and SR22 <S> The CAPS also has some other benefits, such as being easy to use for an untrained passenger (think pilot incapacitation). <S> That might be an important "why" reason and selling point from a Marketing perspective but it isn't directly relevant for certification. <A> My father has a fairly detailed answer to this question, based on experience. <S> His particular evaluation of the parachute: <S> Don’t fly a single engine plane that isn’t equipped with a parachute. <S> Although the chances of actually encountering an emergency situation that is worthy of “pulling the chute” are probably small to infinitesimal over the course of any given pilot’s career, the penalty for not having a parachute is almost certain death. <S> Each pilot has to establish and evaluate their own risk assessment criteria, but for me something that has a greater than 50% risk of death, even if only 1% of the time, is an unacceptable risk. <S> That’s why I bought a Cirrus in the first place. <A> There is no shortcoming to the Cirrus SR airframes requiring the installation of a ballistic parachute to make them safe for spins. <S> As I commented, the Cirrus SR aircraft have been spun and recovered successfully during flight testing, though the spin certification process was bypassed with the wing cuff technology to provide more roll authority and stall prevention. <S> Cirrus originally added the parachutes an an integral part of every new airplane which they designed as a result of a mid air collision Cirrus founder Alan Klapmeier was involved in. <S> He resolved to find a means to make light aircraft safer for their uses and found the best solution lay in the installation of ballistic parachutes. <S> The POH and CAPS training documents list activiation of the CAPS in the event of a spin both for ease of recovery and to make the OEM more immune to litigation. <S> The rumors that Cirruses cannot recover from spins fester on GA forums by ignorant pilots trash talking each other about their aircraft. <S> Other aircraft such as the Lancair/Columbia LC-550FG series did not undergo spin certification as part of the certification process and were not equipped with ballistic parachutes (they also can successfully recover from spins as well).
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Cirrus wanted to make a safer aircraft that could recover even if the pilot has no spin training at all, so they implemented two safety features: a "cuffed wing design" from NASA and the CAPS.
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Do quadcopter propellers break the sound barrier? I recently bought a quadcopter and noticed every time I fly it there is this weird buzzing noise. I have heard this noise on other quadcopters around the same size as mine(4in by 4in). On an airliner turbofan engine you can sometimes hear this weird buzzing sound from the engines, which this sound is the n1 fan spinning faster than the speed of sound and resulting in this loud buzzing sound. So is my little quadcopter motors going supersonic or is it something else? Source:(dynomodels.co.uk) <Q> Almost certainly not. <S> Given the comments specifying a $0.5$ inch radius (blade length,) that means the circumference of the path of the blade tips would then be $$2 <S> \pi \cdot <S> 0.5 \, \text{inches} \approx <S> 3.1415 \, \text{inches} \approx 0.2618 <S> \,\text{feet}$$ <S> To get to the speed of sound (which is approximately $1,126 \,\frac{\text{ft}}{\text{s}}$ at sea level,) that means you'd need to have the fan spinning at $$\frac{1,126}{0.2618} \approx 4,301 \,\text{Hz} \approx 258,060 \,\text{rpm}$$ Needless to say, that's not happening unless you have one seriously expensive quadcopter. <S> The buzzing you hear is probably either the frequency at which the motor is spinning or, perhaps, the frequency of some oscillation of the fan blades. <S> Most likely, though, it's just the frequency of the motor/fan. <A> Supersonic propeller tips really mess with efficiency. <S> There is a formula to figure out the speed of the blade tip. <S> For your quadcopter multiply the blade <S> RPM by the diameter (in inches), and multiply that by 0.00426 <S> $ TipSpeed = <S> RPM <S> * Diameter <S> * 0.00426 <S> $ <S> The result is in Feet per Second. <S> Anything over 1125 feet per second (343 meters per second) and your tips are supersonic. <S> Anything over about 650 feet per second (200 meters per second) and the propeller is probably really loud and annoying . <A> It is entirely likely that your quadricopter, based on the picture, is not even in the range of expensive supersonic models. <S> They do exist, but they're mostly modded or privately made. <S> The buzzing, if it is underlying the whine of the fan, is probably either the motor itself or some other internal friction. <S> Fortunately, this isn't a huge problem. <S> It is, however, annoying. <S> On the other hand, if it is the whine of the rotors, which you described as a "buzz", that's just the way they sound at that size and type, evidenced by your knowledge of the sounds of similar copters. <S> But a model of that size and apparent cost could never reach the sound barrier. <S> There would be something on the package about that, because producers like bragging about speed. <S> Also note the shape and size of your average turbofan.
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The tip speed of many aircraft propellers is close to supersonic, and if not properly controlled can exceed the speed of sound, but most models don't get up that fast (and your blade tips don't have to be supersonic to be annoyingly loud). It's possible, but I would say unlikely.
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Is it possible to drop a payload via anchored parachute? Apologies if this is not the proper forum for this question - Here's my situation: I'm trying to drop a payload via parachute with some accuracy. I'm worried that in the above setup, the line will interfere with parachute deployment or - if not deployment - operation during flight (imagine wind pushing the chute into the line). I haven't tested this yet but plan to. Does anyone know how the payload <> anchor connection might be engineered to ensure full deployment throughout the descent? <Q> I'm trying to drop a payload via parachute with some accuracy. <S> Cut a hole in the middle of the parachute, make its edge smooth and install a pipe through the center of the box that contains the payload. <S> Run the line through the pipe and parachute and let the payload fall from the balloon. <S> I believe the trick will work for small parachutes able to deliver up to 10 kg to the ground. <A> If the hot air balloon is well anchored you can probably just use your original plan. <S> The winds aloft will push the balloon in the direction the wind is going, so the anchor rope should be at an angle relative to the ground. <S> When you drop the parachute, those same winds should keep the parachute/payload pushed clear of the anchor rope. <S> I worry about Energizer777's solution though. <S> Mainly because the rope might be angled because of the winds aloft, as stated before. <S> Payloads on a parachute like to hang right below the parachute (more or less), and if the angle on the rope is sufficient the payload will simply end up resting on the rope itself, which might foul up and collapse the parachute since it's load <S> will not be pulling on it properly. <S> All of that being said, that solution will work if you do this on a day with very calm, or non-existent wind... <A> Set up the payload and small chute on a bar, the opposite side of which has a counterweight with a small chute of equal size, so as to keep it parallel to the ground. <S> Also consider setting up a bar with the payload attached and a large parachute, attached at both ends to two separate anchor lines. <S> Both of these ideas have the advantage of modular, uncut boxes. <S> Chute```````````````Chute <S> Box-----Line-----Counter Or <S> |........... <S> Box+Chute...........| <A> The problem is that you can't fix the angle with a single beam. <S> Instead, use the following setup (90 degrees rotated for ASCII art): ,<) __/___________A____________/ \\ \__/ <S> That is to say, use two beams to guide two rings along the anchor rope, and connect the parachute to the top of the A. Furthermore, connect the payload to the middle of the A (below the connecting bar) to balance the air friction of the parachute and the rope friction on the other side. <S> This reduces the tilting torque.
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So long as the drag rope connecting the payload to the anchor rope is sufficiently long and the mechanism connecting the drag rope to the anchor rope is sufficiently slippery, you shouldn't have a problem.
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Is this a wing-tip device on the A-10 "Warthog"? Source: Flickr courtesy of: U.S. Air Forces Central Public Affairs, photo by Master Sgt. William Greer Notice at the side edges, the wing peels down and back around towards the fuselage. (The airplane is upside-down in this photo.) Never noticed this before. Is this a wing-tip device producing more lift? If so, what kind is it? I would like to read more about it. <Q> The wingtip devices used in A-10 Warthogs are called drooped wingtips (also called Hoerner wingtips in some cases), which essentially increase the aspect ratio of the wing by forcing the vortices further out. <S> Source: <S> zenithair.com <S> There are a few reasons for having this wingtip device: <S> The drooped wingtips act in a manner similar to the winglets and reduce the induced drag. <S> As a result, the loiter capability of the aicraft, an important one for Close Air Support (CAS) aircraft, is improved. <S> The A-X competition, that lead to the A-10 develpment, required the aircraft to have Two hour mission loiter time at max mission radius with 9,500 lbs payload <S> The drooped wingtip increases the local span loading near the wingtip, due to which the aileron response is improved, increasing the manuverability at low altitudes. <S> The A-X competition required the aircraft to be Highly maneuverable below 1,000 ft <S> The drooped wingtips also improve the takeoff performance, an advantage as the aircraft is expected to be operated from short, forward fields. <S> Infact, drooped wingtips are found in STOL kit of some aircraft, like DC-2 Beaver . <S> One of the requiremens of the A-X competition was that the aircraft should have 4,000 ft takeoff distance at MTOW. <S> As can be seen, the drooped (down) wingtips wingtips serves these purposes. <S> There seems to be some confusion regarding the reason for these wingtip devices. <S> However, I think this is unlikely, given the ailerons, when extended, go well beyond the wingtips, as shown below: <S> Source: <S> scienceforums.net Dropped down wingtips do serve that purpose (sometimes) in gliders. <S> However, there is no reason to believe that is the case here, considering the height above the ground and the aspect ratio. <S> The drooped wingtips, on the other hand serve to hold the countermeasure system. <S> Source: rcgroups.net <A> It's called a drooped wingtip. <S> The general idea is to move the vortex away from the wing, reducing it's influence. <S> As with all the winglet variants, opinions vary about whether or not it generates more lift than other variants. <S> Source <S> There are more aircraft that employ this type of wingtip device: Source Source <A> If I add raised wingtips to one of my RC planes they significantly decrease the aileron authority, meanwhile improving the dihedral effect and the self-stabilizing tendency. <S> But for maneuverability, it's not as good. <S> If I add an autopilot, like Ardupilot, the raised wingtips will make harder for the autopilot to instantly correct the leveling when passing through turbulence, because the effect of the ailerons is dampened by the self-leveling tendency. <S> Basically, the ailerons have to fight not only to change the attitude of the wing, but against it's tendency to rotate by itself, that might not act in the right direction when flying through turbulent air. <S> If I add dropped wingtips, they improve lift (the same wing is capable to carry more weight) and they increase greatly aileron authority, while decreasing passive auto-leveling. <S> The plane becomes harder to fly manually, but for the autopilot the effect is good, because the smallest deflection of the ailerons will have a big effect. <S> The autopilot is capable to correct instantly the horizontal attitude of the wing, by moving the ailerons very fast, and in minute increments. <S> The plane will look like it's flying on rails, even when it passes through turbulence. <S> And the lower the altitude, the greater the turbulence, because the wind is moving over ground obstacles and it's not flowing laminarly. <S> When the wind is strong and there are bushes and trees on the terrain, the turbulence can be so great, that a RC model can become impossible to fly low if it doesn't have some sort of electronic self-leveling device. <S> The conclusion is that, for a plane that has to fly low, dropped wingtips and an active self-leveling device are the best combination. <S> If the plane was low wing - high CG, I would have used raised wingtips. <A> Oh boy, you guys are obsessed with that wingtip vortex, seemingly the source of all drag. <S> No, the reason for this wingtip shape is much simpler . <S> It's about the protection of the ailerons from ground contact at low level flight . <S> This is especially important for gliders with their central wheel, but also for aircraft which maneuver a lot at low altitude. <S> They will benefit from something that takes the impact forces and keeps the control surface intact and working, especially when this surface will be deflected downwards at the time of ground contact. <S> Honestly, this is the reason, not some esoteric vortex shifting. <A> I thought of another one; if you're installing wingtips and it doesn't matter whether they point up or down, the latter will be less of an obstruction to the view from the cockpit, which is convenient for an aircraft also used for forward observation. <S> It's an interesting question! <S> I think my answer wasn't mentioned yet?
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One theory (@Peter Kämpf) is that they are there to protect the ailerons from ground contact.
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