Split (1)

train · 95.7k rows

source stringlengths 620 29.3k	target stringlengths 12 1.24k
What is the measurement system used in the aviation industry? I saw this question from History Stack Exchange and noted that the US is still using the imperial measurement system such as feet, miles and pounds. Given that a plane may need to fly from one country to another, is there any standardisation across the globe? Does planes manufactured by Boeing use one system and planes made by the Airbus another system? If not, wouldn't it be very easy for pilots to make calculation error? <Q> Outside US, SI is generally used for everything except altitude, distance and speed . <S> Altitude: <S> 1000 ft happens to be reasonable vertical separation, which is somewhat easier to calculate with than the corresponding metric figure 300 m. <S> Distance <S> : There are two quantities that were never converted to decimal. <S> Time and angle . <S> Since we didn't switch to gradians, it makes sense to keep nautical mile, which corresponds to 1 minute along meridian or equator, as it makes calculating distances from navigational maps somewhat easier. <S> If the maps were marked in gradian coordinates, 1 gradian would be 100 km and kilometres would be used. <S> Speed: Obviously based on the unit of distance in use. <S> In Russia, Commonwealth of Independent States (most former Soviet countries) and China (and I am not sure whether some other Asian countries), metric system is used for everything. <S> I believe in Russia they recently switched to flight levels based on feet, but they do use metres below transition altitude. <S> Before second world war, aircraft built in continental Europe usually had instruments in metric units as well. <S> However before the war aviation was more advanced in the USA, instrument procedures were developed in USA and after the war there was surplus of US-built planes, so most of the world just adopted the US procedures including the units they used as everybody using the same units was more important than any personal preferences. <S> Without these reasons we'd be probably using metric in Europe for everything too. <A> Some old airplanes still use Miles/Hour (MPH) <S> Nautical Miles or feet for distance Statue Miles or feet for weather (visibility and RVR) <S> Mach for high speed flight <S> Inches of Mercury for altimeter settings <S> Most of the airplanes that I have flown can actually switch between "hg and hPa (mb). <S> pounds/square inch for pressure Pounds for the fuel quantity on the aircraft (read by the fuel gauges) <S> Pounds/hour for fuel flow <S> Gallons to order/purchase fuel <S> These are pretty standard in most of the Americas (North/Central/South), but in certain parts of the world some of the units are different: Meters for height Kilometers or meters for distance and weather HectoPascals (hPa/Millibars) for altimeter settings Kilograms for fuel quantity on the aircraft Kilograms/hour for fuel flow <S> Liters to order/purchase fuel <A> Unless Boeing has recently changed to the metric system in their design work, the short answer to the question as to whether Boeing and Airbus use different systems insofar as aircraft manufacture is yes. <S> I'm only familiar with Boeing up through the 747-400. <S> Perhaps others can provide an answer for later models. <S> The Boeing Weight and Balance Control and Loading manuals I have do provide kilogram pages following the pound pages, but that the pound is the controlling unit is also stated. <S> Interestingly, for moment limitations, the manuals follow the inch-pound pages with inch-kilogram pages. <S> In other words, they're mixing systems, which I believe to be unwise as the net effect is to introduce a third, hybridized system. <S> In the past, many 747 freighter flights that I flew were slightly over gross at takeoff due to the fact that the common conversion used for kilograms to pounds was 2.2 when the actual value is 2.20462262. <S> As I remember, only the U.S. and Liberia are still non-metric officially. <S> There is a political dimension to this which you can explore at http://en.wikipedia.org/wiki/Metrication_in_the_United_States . <A> A common misconception is that pounds and kilograms, or nautical miles and kilometers are similar units. <S> They are not actually measuring the same thing. <S> The pound is a unit of force not mass, kilogram is a unit of mass not force.(newtons are the SI unit of force, and slugs are the "imperial" unit of mass) kilometers and statute miles are units of fixed distance and do not cleanly divide into the Earth-geoid's circumference, nautical miles are a fixed integer fraction of the circumference. <S> What matters most to an aircraft(which tend to have minimal acceleration once air born) is not the mass but the lifting force, drag force, and motive force(thrust). <S> As for nuts and bolts etc, all that matters is that an industry standard, "size B" just needs to be consistent between makers and batches, the units used to measure the tolerances of a size B make no difference. <S> The set of standards to be used is purely one of economics, this is why all plumbing in buildings around the world is based on inches, it is a standard so all spare parts fit and mass production makes it low cost. <S> That is what counts, that you call a pipe one inch, 26mm, or size <S> 37G doesn't change the fact that it has a known diameter tolerance thread pitch, thread form, and is compatible between manufacturers. <S> When it comes to machining many machines have, for example, set gear ratios for either metric or SAE forms (maybe carriage movement per rotation of a lathe) and these are very costly machines that last for many decades so just switching <S> may not be cost effective, especially if all the machines need to switch at the same time. <S> American auto makers attempted to mix metric and inch withing single vehicles during the '70s and '80s to ease the transition costs and it was a nightmare for maintenance mechanics.(really one of the several reasons for the downfall of Detroit) <S> The issue is eg <S> a 12mm screw is very close to a 1/2" screw, close enough for general strength but not close enough in thread shape to interchange but too close in size to notice by eye. <S> Also you need two full sets of tools to cover the same size/strength range.	I can tell you that all of the airplanes that I have flown (which are US registered, but some are French built) use the following: Feet for height Knots for airspeed (Nautical Miles/Hour)
Why doesn't the aviation industry use SI units? This is a followup to What is the measurement system used in the aviation industry? and related to this question from History . I can understand the arguments as to why adoption of SI units would not make sense for the general population, but aviation is a specialised business. All professionals are highly trained, and would ( should ) be well versed in both systems anyways, so the transition would be much simpler from the point of view of human factors. The technology would probably be much harder to shift but again, with more and more displays and documentation going digital in cockpits, this again seems to be a not so huge problem. Maintenance and manufacturing is again fairly specialised and restricted to a smaller number of companies as compared to the general case. What are the historical factors that lead up to the adoption of imperial units in the industry? Why are they still being used when widely accepted scientific standards exist? <Q> Non-SI is only used for altitude, distance and speed except in US and some other American countries. <S> Altitude is in feet because 1000 ft happens to be reasonable vertical separation and 1000 ft is easier to calculate with than the corresponding SI figure 300 m. <S> Also the procedures for instrument flying were first developed in the USA using feet. <S> Distance is in nautical miles because it is related to the unit used for measuring latitude and longitude. <S> 1 nautical mile corresponds to 1 minute latitude (and longitude on the equator), which makes it easier to calculate distances from navigational maps using the grid lines as scale (large area navigation maps need to preserve angles, so they can't have constant scale). <S> If angles were converted to decimal, 1 km would be 1/100 gradian. <S> Alas, angles and time were never converted to decimal. <S> Speed obviously based on the distance unit in use. <S> Nevertheless if it was not for the prevalence of US-built planes after WWII and more advanced state of aviation in the USA at that time, we would probably be using metric in Europe too as continental planes before WWII usually had instruments in metric. <A> You state that "the transition should be much simpler in terms of human factors." <S> Ideally, yes. <S> In practice, no. <S> When mistakes happen, they may well be lethal. <S> The Gimli Glider incident was partly caused by a confusion between which system was used to measure fuel quantity. <S> From Wikipedia : The subsequent investigation revealed a combination of company failures and a chain of human errors that defeated built-in safeguards. <S> Fuel loading was miscalculated due to a misunderstanding of the recently adopted metric system which replaced the imperial system. <S> The fact that the Gimli Glider incident ended with no loss of life doesn't negate my point: Human factors such as fatigue will find a way to defeat the best plans of the Safety Engineers. <S> One of the human factors of which you speak is "what you learned first, you learned best" — and this learning is likely to predominate in an emergency situation. <A> This is a historical development that dates back to that much of the early aviation equipment was sourced from the United States, and was consequently in imperial units. <S> This in particular occurred after World War Two, and hence mixing them was a bad idea, and the imperial system stuck. <S> Interestingly, the places where the US did not have a lot of influence- <S> the former USSR and China for example- use metric. <S> As for airspeed in Knots and distance in Nautical Miles, this comes from aviation's nautical heritage. <S> All pilots can do the conversion, but it's rather that changing all the instruments from the imperial system to metric system that would cause a huge headache, among other things, and the cost would outweigh the benefits. <S> Instruments would have to be changed. <S> All maps/charts/etc. would have to be converted. <A> The first part of the answer is that it is too difficult to change. <S> It would involve lots of rewriting rules and manuals and retraining. <S> The second part is that it does not really matter. <S> As a pilot you (or I) do not really care how height or speed or whatever is measured. <S> In the procedures we follow it says height 2000 and speed 200 (or whatever). <S> And the units are the same as the instruments are calibrated in. <S> If you the units where different, the instruments and the procedures would show different values. <S> As long as they are in the same units it would not matter.	Pilots would have to become accustomed to the new units and to learn the changed values which they will probably have memorised, such as important airspeeds. All reference material would have to be converted.
Where can I go to sit in the cockpit of a Boeing? This might sound like a silly question to some, but is it possible to go and sit in the cockpit of a Boeing 737, somewhere in the UK? (Otherwise in Europe, or beyond). Maybe at a museum or something? I'm building a [currently tiny] home cockpit based on a 737, and I'd like to see how the real thing looks and feels. I tried searching online, but I couldn't find anything. Hope this isn't too dumb of a question, i.e. "not possible Jim!" <Q> These are fully certified simulators and are frequently used by commercial pilots for currency training. <S> Their closest location to London appears to be in Paris. <S> I had an opportunity to fly one of their simulators a few years ago, and it was a lot of fun. <S> We spent some time doing landings at the old Kai Tak airport in Hong Kong. <A> Cotswold Airport, near the village of Kemble in Gloucestershire, England. <S> Cotswolds landing strip, has become the busiest aviation scrapyard in the world. <S> Usually the cockpit parts are taken out before they end up there, but you never know; you may get lucky and they grant you access for a day. <S> I don't see why not! <S> Chevron Aircraft Maintenance Ltd is responsible for the dismantling of all Boeing 737 series aircraft. <A> Bournemouth aviation museum? <S> BOURNEMOUTH’S <S> popular aviation museum has a new addition – of a more recent vintage. <S> The distinctive exhibit is an old Palmair jet, a familiar sight at the airport until the carrier closed three years ago. <S> The Boeing 737-200 carried tens of thousands of holidaymakers from Bournemouth Airport, before being replaced by a more modern plane. <S> The front half of the white fuselage was unveiled at the museum along Parley Lane last week. <A> I noticed that someone in the comments had asked about the U.S., too. <S> Delta's aviation museum in Atlanta does offer the ability to rent an hour in an old 737-200 simulator. <S> This is a full-motion pilot-training simulator. <S> Their website claims that it's the only one open to the public in the U.S. <S> It costs about $400 USD for an hour. <A> This is a little bit of an "outside of the box" answer, and I won't be accepting it. <S> I'm just sharing it <S> so there are more ideas of places to do this. <S> Virgin Experience Days offer 15 minutes of 737 simulator time to newbies for £24.50 in London. <S> I guess I could just tell them I don't want to fly, I just want to "play with the buttons" :P <A> British Airways' flight training program provides public access to their full motion simulators . <S> You can book a one hour training session in their 737-400 simulator. <S> In my opinion, well worth the money, since its a professional <S> and I stress again full motion simulator . <S> In fact, its the same one BA uses to train their own pilots. <S> They are located in Cranebank . <A> Your best bet would be SimSpot . <S> This way you can get a real look and feel. <S> I have been past this spot time after time as is in the Cineworld but never ventured in. <S> It's now on my checklist of things to do 2015 :)	There is a company called Flight Experience which builds 737 simulators and offers their use to the public.
How do airliners cross the ocean without GPS? How do airliners cross the ocean without GPS? Do they use dead-reckoning or are there navigation aids floating out there? <Q> The INS feeds into the flight management computer which is used to cross-check the GPS position, and can be used as a primary navigation source should the GPS signal be lost or corrupted. <S> Prior to GPS, inertial navigation was the primary means of navigating across oceans. <S> However, a great many airplanes did cross oceans before INS... with varying success. <S> Hopefully, this puts you in position after some period of time to pickup ground-based navigational aids, or to identify a coastline. <S> This actually works pretty well if your wind estimates are good, and the margin for error is high enough. <S> As DeltaLima points out, long-range radio navigation systems also started to emerge around World War II (LORAN and Decca) which had a much greater range than previous radio beacons, and therefore decreased the amount of time required to fly by dead-reckoning alone. <S> By the time inertial navigation became prevalent in the 1970's, airlines were already providing reliable transcontinental passenger flights every day. <S> Another possible outcome is that your plane is lost in the ocean, never found, and the Discovery Channel funds an expedition to look for you 75 years later. <A> We were crossing the seas centuries before GPS, INS or really any other form of modern technology. <S> All you need is a clock, a compass and a sextant. <S> And some largely-forgotten skills, like how to do math without a smartphone. <A> In the days before GPS, we routinely crossed the oceans using inertial navigation systems. <S> The system I was familiar with used 3 separate inertial systems <S> (Carousel was the brand name). <S> You could choose to navigate by any single one, but the most common way of using them was to have the autopilot "average" the positions. <S> You could also choose to exclude any given INS, in which case if you were averaging, you were averaging only two. <S> For the North Atlantic MNPS airspace system, You manually updated each INS passing over your last known ground position fix. <S> When you passed over your first ground-based nav fix on the other side, you again manually updated the INSes with that information and then recorded in the maintenance <S> log how far off left or right <S> each INS was in the maintenance log. <S> There were standards. <S> Offhand <S> I'm not sure I am remembering them correctly, but what I seem to recall was a max error of 2 nautical miles per hour flown without update. <S> The MNPS had at the time a max error allowed without penalty of 10 nautical miles left or right of course. <S> If that was exceeded, points were deducted from your company's score. <S> Lose enough points and the company would not be allowed in fly in MNPS. <S> Off course errors of two to six nautical miles for a crossing were typical. <S> There is the story, true or not I do not know, of the captain who, when hand held GPSs first became available, used one to cross the North Atlantic, and had a near zero off course error. <S> When ATC complimented him on that, he blurted out that he had used his hand-held. <S> He was subsequently violated for using a non-approved navigational system. <S> Whether the incident really happened, I don't know, but an airline's FAA approved op specs specifies not only which navigation methods are to be used but also which systems by brand and model name (at least back when I was flying). <A> Most aircraft cross the atlantic by GPS, usually with INS as backup. <S> INS as the primary form of navigation is still used as well. <S> Historically, a combination of dead reckoning and long range radio navigation systems were used on transatlantic routes. <S> These include Decca , LORAN C and Omega . <S> Omega was shut down in 1997, Decca in 2000 and LORAN C ceased in 2010. <A> They do use GPS, with backups, as the other answers describe. <S> If your question is inspired by MH370, remember that GPS tells you where you are: it doesn't tell anyone else where you are. <S> GPS works by having a bunch of satellites sending out signals and, based on the signals you hear, you can calculate your own position. <S> A GPS user doesn't transmit anything back to the satellites. <S> What MH370 lacked was a system that was reporting its location back to base. <A> Mode of air navigation <S> I've witnessed: Celestial - sextant and charts. <S> Like, no kidding, right out of days of sailing ships. <S> Atmospheric pressure - driving along specific barometric pressure lines. <S> By no means a primary form of navigation. <S> Omega - now obsolete. <S> Triangulates on a small number of very powerful radio transmitters spread around the globe. <S> At least good enough to hit the ADIZ w/in limits. <S> I'm told when particularly close to a transmitter it can be as accurate as A Cat 2 ILS beam. <S> Inertial Nav - GPS. <S> what's that?	Well, most airlines do cross the ocean with GPS in today's world. The general idea was to use a combination of dead-reckoning, radio beacons where you can find them (small islands and coastlines), the sun (with the help of a sextant ) during the day, and the stars at night. That being said, most (if not all) transcontinental airliners, and many flying domestic routes as well, have what's called an inertial navigation system (a form of dead-reckoning where gyros and accelerometers are used to compute changes in position).
Can large airliners be operated without ground support? I'm wondering if large A3x0/B7x7 airliners could be operated without ground support. Short of using the inflatable slides, I guess at least stairs would be required to load/unload passengers. Apart from that, assuming fuel and push-back is not required, would it be possible to land, switch the engines and systems off and then take-off again without electrical, A/C, etc. ground support? Bonus question: If possible, are there any circumstances where this is routinely/occasionally done? I know that it's definitely the case for smaller aircraft such as an ATR 72 servicing remote airports - I experienced that at e.g. Luang Prabang airport. <Q> There's a good example which is the A319 LR which flies scientists down to Antartica. <S> They utilize (very) little ground support, except for the stairs (they seem to have inbuilt ones in the front as well, although these are not used on site) and the trucks to offload the cargo. <S> APU provides the power on the ground, and the aircraft has sufficient juice in the tanks to make the round trip without refuelling. <S> (source: smh.com.au ) <S> You can read up on it here . <S> She does weekly flights from Hobart to Wilkins aerodrome in Summer. <S> 4 hours and 30 minutes of flying right into the uninhabited :) <A> In a word, yes. <S> The APU (auxiliary power unit) will supply air pressure and power the electrical systems needed to start the aircraft. <S> No ground support is required. <S> http://www.flyingmag.com/pilots-places/pilots-adventures-more/jumpseat-its-all-about-apu <S> It's routinely done all the time! <S> Next time you're at the airport, watch a 7xx or A3xx. <S> Ignoring stairs, fuel, food, toilet drains etc there is sometimes no external air or power supply attached. <S> The APU will be running during boarding to power the aircraft and condition the cabin. <S> It is then used to start engines during the pushback. <S> When in the cabin, you will notice the packs being switched off (the packs supply cabin air) as the air is diverted to the engine starters. <S> The only times I've seen this not done is when an external air conditioning cart is attached as the APU cannot cool the aircraft. <A> The venerable DC-9 was designed to service small airports out away from the hubs with a minimum of equipment. <S> The engines were up on the fuselage rather than under the wing so that the landing gear legs could be short, lowering the fuselage. <S> This result let the baggage compartment be reached without the usual portable conveyor belt. <S> Air stairs were built into the fuselage and were deployed horizontally, until they lowered the outboard end to the ground. <S> Gravel kicked up by the nosegear and then ingested by the engines <S> became a problem so the DC-9s and the MD-80s that followed had a gravel deflector shield mounted on the nosewheel. <S> Now the DC-9 is not a Boeing or Airbus in the original question (ok, ok, lets agree to set aside the Boeing 717 <S> that was the final iteration of the DC-9/MD-80 family) <S> but the principle endures: <S> However, the vast majority of commercial airports are well equipped to handle planes, so the designers of the planes have in many cases left all that stuff off the planes to save weight, complexity, and space. <S> So the ground support is necessary. <A> This autarky led to significantly increased weight, which meant that while these planes could land at remote destinations, they suffered from incompetitiveness in inter-airport service. <S> And well, how often would one need a wide-body to bring 350 people into the middle of nowhere? <S> Many military transport aircraft, while having similar size as the aforementioned airliners, can fly tanks and/or equipment into remote areas. <S> Fedex would never buy one, though... <S> these machines are plain incompetitive in both acquisition and maintenance. <S> No plane requires a pushback vehicle in a remote destination, if said destination has a rotunda big enough for a full-turn, or if you have a runway with double the normal length.	Large commercial airliners can be designed to function nicely without a ton of ground support. It is possible with the old soviet wide-bodies; they have built-in stairs and even allow for luggage stowage by the crew during boarding.
How are backlit aircraft panels (for simulators) made? I'm wondering by which method this sort of aircraft panel that enabling backlighting are made? What is the process? I've gathered they are acrylic but how is the gray paint selectively removed? pic http://www.simparts.de/WebRoot/Store/Shops/15465782/4B72/6E37/0BF8/50E9/641B/C0A8/28BA/29AA/A320-OHP-009-5.jpg <Q> This video says the following: <S> Here's <S> my Tonson TS-3040C CNC making an EFIS panel for my flight simulator. <S> For the lettering I am using a 0.4mm End Mill and for cutting out I'm using a 1mm End Mill. <S> RPM is 10000 and movement is 300mm / Min. <S> The material is Cast Acrylic which I have given one coat of black paint and two coats of grey paint. <S> So that's at least one method, but there are probably more... <A> It's a 3 layer color system with white opaque special laser colour, a black light block layer, and the final colour. <S> For military it stays black without the 3rd one. <S> After spray painting the special laser color is removed with a laser system. <S> You can see it here . <A> This page has some good information and a graphic, looks like the same as shown in the video Manfred posted.	Clear plastic with an opaque layer that is engraved off, and lighted from beneath.
What noises can you hear as a passenger? I'm just curious as to what the noises are that you can hear as a passenger in the cabin of an airliner? For example (ignore the crew talking), the noise at 7:09 - 7:30 on this video ; is that the flaps? What other sounds might a passenger be able to spot? <Q> On the ground you may hear (and feel) <S> In-flight you have engine noises and air flow noises. <A> At that point it was indeed the flaps extending in preparation of takeoff (you can see them moving through the rain). <S> You would typically also be able to hear the cargo doors closing (before the plane starts taxiing) and the engines ramping up as you start to take off ( at 8:54 in the same video). <A> An interesting noise you can hear is the sound of the PTU (Power Transfer Unit) during the A320 startup. <S> It sounds like a cross between a dog barking and someone dragging a wet finger across glass. <S> https://www.youtube.com/watch?v=9aGsXmNjPRw <S> What happens is that the PTU is transfering pressure from one hydraulics system to the other to equalize them. <S> Since the pressure is not always unequal between the hydraulics systems, this is not audible during every startup. <A> A major noise (and vibration) during the flight is the retraction and extension of the landing gear as well as the wheel brake on the wheels once the gear is fully retracted. <S> The vibration is more noticeable (obviously) on aircraft with the main gear in the fuselage and if you are seated over the main gear.	There are loads of noises you might hear; there are fuel pumps, hydraulic pumps, air circulation, adjustment screws, servos, and on Airbus aircraft a strange clanking noise when you go over bumps in the tarmac. cargo pallets rolling on the hold, and the hold doors being opened and shut.
What can the Flight Attendant Panel do? I've noticed that on some airlines (I may have seen it on SAS) the cabin crew had a small touchscreen at the front of the plane which they were using to select recorded audio messages etc, in both their language, and English. Searching the internet, I found out it's called a Flight Attendant Panel — here are some photos I found: So I gather they can control the lighting, and movies; but what else can these panels do? I also found a FAP trainer , which says: This virtual training environment generates a realistic FAP representation including OBRM, CAM and PRAM What are OBRM, CAM and PRAM? What is being displayed above? <Q> Here is an interesting presentation that discusses most of the communications systems on the A320 family (looks like the pictures you have and should apply in general). <S> The CIDS (cabin intercommunication data system) starts about halfway through on page 21. <S> The FAP is part of this system and can control: <S> Passenger reading lights Passenger call buttons <S> Passenger address (PA) <S> Automatic announcement and boarding music <S> Cabin/Service interphone and calls EVAC signal <S> Emergency light Door bottle pressure monitoring (either oxygen or escape slide?) <S> Door proximity sensors (doors closed properly) Smoke detection Water and waste tank quantities <S> The acronyms you listed are: Cabin Assignment Module (CAM) All the software for specific customer layouts and defined parameters in the FAP (same as OBRP). <S> On Board Replaceable Module (OBRM) <S> This is a generic term for any module that is easily replaceable. <S> In this case it refers to the module that contains all the information used by the FAP (same as CAM). <S> Prerecorded Announcement and Music (PRAM) <S> A good list of Airbus acronyms including these can be found here . <A> The OBRM, PRAM, CAM are three memory cards, which hold aircraft related data and softwares and plugged into the FAP at botton. <S> (You can see three slots).The page shown in the picture is cabin status page, which is showing current status of aircraft namely Music, Lights, Doors, temeperature and lavatories. <A> In simpler times the panel didn't do much at all.	Cabin lighting controls Cabin system monitoring/testing Passenger entertainment system
What is a "Flight Director"? What is a Flight Director , and how does it differ from Autopilot ? <Q> The flight director is related to the autopilot system. <S> It displays a guide on the artificial horizon, which shows the attitude of the airplane, but does nothing to control the plane. <S> The guide represents a reference of an airplane attitude that will follow the parameters set for the autopilot. <S> The pilot can manually fly the plane directly where the flight director indicates, and by doing so the plane will follow the parameters set for the autopilot. <S> If the autopilot is engaged, autopilot flies the plane to follow the flight director. <S> Although a flight director typically accompanies an autopilot system, some aircraft have a flight director without an autopilot. <S> The procedure to engage them is to first turn on the flight director, which will show where the autopilot wants the plane to be, and then to engage the autopilot, which will then automatically fly the plane. <S> This is what the autopilot controls can look like. <S> Here is the Boeing flight director, visible as the crossed magenta lines in the center of the screen. <A> It lets the pilot know what the autopilot would do if it were flying instead, by displaying an indicator, usually a miniature pink plane or line, on the artificial horizon. <S> The difference between the autopilot and flight director is that the autopilot flies the plane, the flight director gives the pilot an idea of what the autopilot would like to do if it was in charge. <A> It's the traditional flight instruments, integrated to work in a complementary way. <S> For example the steering bars moving across the face of the compass so as to give the pilot visual ques for turning onto a desired heading and/or altitude. <S> The flight director gives a visual display of the overall aircraft attitude in space. <S> The flight director display reacts to inputs coming from, for example, heading dials, electronic flight plans, and actual aircraft movement. <S> The flight director does not physically control the aircraft. <S> The autopilot physically controls the aircraft in response to essentially the same inputs. <S> The flight director essentially does not care if a human or the autopilot is actually in control. <S> The autopilot adds intelligence which allows for various levels of pilot non-intervention up to the point of virtually hands-off control from takeoff to landing. <S> Together, the flight director and autopilot permit the pilot to let his skills atrophy while inducing a sense of inferiority on the part of the pilot in command; thus permitting well controlled crashes. <A> Simply: Flight Director is a system that computes desired pitch and roll from parameters like heading, altitude, vertical speed. <S> Then an autopilot computes control surfaces deflection from given parameters: pitch and roll. <S> So: Pilot sets altitude, heading for Flight Director. <S> Flight director then computes pitch and roll for Autopilot (and human pilot, too).If Autopilot is engaged, then it computes control surfaces deflections and moves the surfaces. <S> Flight Director is also displayed on PFD in some way, so if Autopilot is disengaged, the human pilot can still fly to follow FD's directions.	The flight director serves as a visual indication of where the autopilot wants the plane to go.
What are these things hanging off the trailing edge of the wing? What are these things hanging off the trailing edge of the wing? I've seen them in almost all of the aircraft I've flown in, and can't remember if they're exclusively Boeing or Airbus. <Q> Those are static wicks -- Basically these are little wires screwed to the airframe. <S> Their purpose is to discharge the static electricity that an aircraft picks up moving through the air - especially in clouds. <S> The static discharge tends to happen at "pointy" protrusions from the aircraft - if this happened through antennas it could cause radio and navigation interference, so to prevent that static wicks are installed, providing a low-resistance protrusion for the charge to dissipate through (and as an additional benefit, dissipating the charge helps ensure your aircraft doesn't attract lightning strikes). <S> Here's a couple of closer pictures: <A> These are static wicks or static dischargers. <S> They dissipate static electrical buildup caused by the friction of air flowing over the surface of the aircraft. <S> The air friction tends to separate electrons from their atoms just as rubbing a balloon tends to do, causing an imbalance of electrical charge on a body. <S> The wicks work by providing a pointed surface where airflow separates from contact with the aircraft body. <S> The excess charge tends to flow into the air and is swept away from the aircraft. <A>	It's called static dischargers since aircraft body or fuselage is made up of metal and carrying tonnes of fuel and electronic devices, we will have to remove the static electricity charge from the fuselage to the air in order to not ignite the fuel or disturb the electronic devices, and that's how it's done ! :)
Why are FDR's called "black boxes" when they are actually orange? Why do they call flight data recorders a "black box" if it's orange in color? Just curious about this since I've seen several images of black boxes but they all come in orange colors, and not black. I can understand orange being used to help brightly identify the box , but then why call it a "black" box? <Q> The Wikipedia article on Flight recorder offers a possible explanation for the origin of the term: ... <S> they were essentially photograph-based flight recorders since the record was made on a scrolling photographic film. <S> The latent image was made by a thin ray of light deviated by a mirror tilted according to the magnitude of the data to record (altitude, speed, etc.). <S> Since the inside of the recorder was pitch black, this may be the origin of the "black box" name, often used as a synonym for a flight recorder. <S> Interestingly, the Wikipedia article on Black box claims that the term entered the English language around 1945, which is a few years after the first flight data recorder was built. <A> A black box (generally speaking) is a device or box whose internal working are not of as much interest or value but rather the input and output. <S> Flight data recorders are orange so that they can be located easily in case of a crash. <S> If they were black, they can be camouflaged by their surroundings. <S> Another reason is that they are painted/coated with heat-resistant bright orange paint. <A> The correct answer seems to be, "Nobody knows for sure" but here's some data. <S> The earliest citation in the Oxford English Dictionary for the phrase "black box" referring specifically to a flight data recorder isn't until 1964, from the UK Daily Telegraph : "The flight recorder is an indestructible 'black box' which automatically records the key functions in the aircraft..." <S> There are earlier uses of the phrase, with different meanings. <S> Since 1932, it has been used to mean a device whose internal workings are unclear but which is specified by its inputs and outputs; since 1945, it has been used in the Royal Air Force to refer to various navigational devices which, according to Wikipedia sometimes were housed in literal boxes that were black. <S> My interpretation/thoughts/speculation/ <S> whatever word you want to use: <S> The use of quote marks in the Daily Telegraph seems significant. <S> Second, "a 'black box' " suggests that the FDR might be just one of several devices on a plane that could be described as "black boxes". <S> Unfortunately, that seems consistent with both of the other given definitions: you could perfectly well imagine it being RAF-style slang for "This electronic box of tricks does navigation, this one holds the autopilot and this one records flight data" or the input-output version of " <S> I don't know exactly how the autopilot works, but I know what it does; ditto the navigation system; ditto the data recorder." <A> The adjective "black" in "black box" means "opaque". <S> Engineering also uses the phrase "black box testing", which means tests that are done without access to system internals. <S> Similarly, "white box" means transparent, in which internal signals may be recorded or manipulated. <S> A black box recorder is presumably recording pilot actions on the system as well as the state shown to the pilot on the instruments, but none of the avionics internal variables. <S> I doubt any modern FDR would be designed this way, however, since without the internal variables diagnosis of failure could be very difficult. <A> One other theory I've heard (but been unable to verify) about the origin of the term "black box" in popular literature is that the boxes when found often tend to be black. <S> Not as a result of being painted black, but as a result of having been inside a burning aircraft wreck, covered in soot and burnt paint. <S> Whether that's the (or even one of the) reason for the term is probably lost in the mists of time. <S> I seriously doubt it's ever been written down by the people inventing the term <S> (newspaper journalists most likely) what their reasoning was.	First, it suggests that we're not talking about a literal box which is black and you might imagine they'd say something like " 'black box' (which is now actually orange)" if they were formally literal black boxes. Bright orange color make them stand out easily, because nature didn't make many things orange, besides oranges.
Does an aircraft's nose landing gear extend on take off? Something I noticed while flying - while on takeoff it feels as if the plane is tilting upwards even though the plane is clearly still on the ground with all sets of landing gear. Does the nose gear extend immediately upon acceleration to perhaps generate more lift? Or maybe it's just an illusion caused by the acceleration. (I've only noticed this on large aircraft - like for example: Airbus A320 or Boeing 737.) <Q> No, the gear doesn't actively extend, and any passive change to the strut extension during takeoff is likely to be imperceptible . <S> It is a physiological sensation, not a physical change. <S> Rapid acceleration, as during a takeoff roll, causes the inner ear to report what your brain assumes is your head tilting back. <S> The otolith organs in your inner ears <S> sit in fluid and detect the tilt of your head. <S> Acceleration and pitching up (or tilting back) cause the exact same movement of the otoliths. <S> Because the otoliths are pushed backwards by the fluid, just like they would by you tilting your head back, it feels like a climb. <S> When an airliner is taking off, you have limited outside references to the horizon and your inner ear takes over the task of orienting you. <S> You might notice it in smaller aircraft if you closed your eyes; in very small aircraft, the acceleration may be too slow to trigger the illusion. <A> I'm assuming you are referring to the 'tilting backwards' that occurs when the aircraft begins its takeoff run. <S> There is of course a much more pronounced tilting backwards when the nosewheel actually lifts off the runway, a few seconds before the main wheels come off. <S> This tilting at the start of the takeoff run is actually a sensory illusion. <S> It's caused by the acceleration of the aircraft. <S> The forward force on you from the seat is combining with the upward force (resisting gravity) makes it seem as though the aircraft is tilting, when in fact it isn't. <S> You would get a similar effect in a fast-accelerating sports car; however in a car you have a clear view of the outside world which means your mind can understand that this is acceleration, not a tilt. <S> You can check this in a number of ways: <S> 1) if you watch a plane taking off from outside , there is no noticeable tilt of the plane, nor any noticeable change in the nosewheel extension - certainly nothing like as much as the tilt appears to be from the inside 2) <S> Looking at the outside world through the window will confirm that the plane is not tilting 3) <S> This effect occurs on planes with engines both above and below the wings, which you would not expect if it were an actual tilt. <A> I will assume you refer to the initial acceleration when you speak of "while on takeoff", since after the rotation the answer would be quite tautological. <S> The effect you are feeling is due to the acceleration and the inertia of the aircraft: the engines of a large aircraft sit below the Center of Mass which will incur a rotational force to the aircraft, lifting the nose up a bit. <S> The weight will be "sitting" more on the main gear rather than the nose, you have a similar effect on a car or, more notably, on an accelerating motorcycle. <S> You also have the reverse effect when decelerating: the weight will tend to stress more the nose gear rather than the main gear, the same way a motorcycle tends to "sit" on the front wheel when stopping. <S> On aircraft with the engines up high the rotational force will be reversed until the elevators have enough airflow to counteract it.	Let's be clear, the nose gear does not "extend" anywhere during take-off since its damper/shock absorber is not an active component, but rather a passive one. What you are perceiving during takeoff is the somatogravic illusion .
Why is laser illumation of a cockpit an emergency? Another answer pointed out that laser illumination of a cockpit may be considered an emergency, and that pilots may take evasive action when under laser illumination. Why is laser illumination considered an emergency? Have any documented instances of laser illumination resulted in injury to or loss of crew, passengers, or plane? <Q> Let me posit a hypothetical game ("Don't Try This at... <S> well Anywhere <S> "). <S> It's simple - there are just 3 rules: <S> Give your friend a nice laser pointer and have them stand at the end of a road <S> A half-mile or so should be plenty. <S> Get in your car at the other end of the road and drive toward your friend. <S> Your friend's goal is to shine the laser in your eyes. <S> Your goal is simple: try not to crash. <S> Clearly this is not a very safe game. <S> It should be clear that playing the same game with aircraft is substantially less safe. <S> Someone attempting to "play" without your consent certainly rises to the definition of "emergency" in my book. <S> If you actually play this game you'll note that the laser isn't a neat pinpoint when it's shining at you. <S> Between scratches in the aircraft's window and the way your eye perceives light the laser pointer can completely blind the victim - check out the examples in the graphic below. <S> [ <S> To date I don't believe any accidents have been attributed to laser illumination, but it is well within the realm of possibility, and the upward trend in laser illuminations of aircraft means the likelihood of such an accident is also increasing. <S> For more information check out the FAA's Laser Safety Initiative -- and particularly the video here . <A> Even if the laser doesn't cause temporary or permanent injury to the pilots' eyes, it causes them to lose night vision. <S> The most well-known cause of this is the pupils of your eyes. <S> In the dark, the pupils open up to allow in as much light as possible. <S> When they're exposed to a sudden bright light, they close up again. <S> If the bright light goes away, it takes your eyes some amount of time (say, a minute or two) for your pupils to open again. <S> During that time, you can't see very well at all. <S> Not good, if you're trying to land a plane. <S> You can experience this for yourself by playing around with the lights indoors at night: if you turn the lights off, you can see very little but, gradually, you begin to make things out as your pupils open. <S> If you then turn the light back on, it feels uncomfortably bright until you get used to it again. <S> Less well-known is a chemical called rhodopsin , in the rod cells in your retina. <S> Rhodopsin is extremely sensitive to light (even to single photons), and light makes it change shape. <S> Other proteins bind to this new shape and <S> a few little chemical reactions result in an amplified signal being sent to your brain. <S> Most of your vision in the dark comes from the rod cells because of their high sensitivity; the other cells (the cones) require tens to hundreds of photons to fire so they're great for colour vision in decent light but not much use in the dark. <S> However, being bound to other proteins means that the rhodopsin in your eyes is "used up" as light comes into your eyes. <S> When its dark, this happens slowly enough that the rhodopsin can be regenerated but a sudden burst of bright light, such as from a laser, consumes all the rhodopsin in your eyes almost immediately. <S> Now, you're only seeing with the cones, and you're not seeing much. <S> The really bad news is that it takes at least 5–10 minutes for a decent amount of rhodopsin to regenerate and 30–45 minutes to get back to the full amount. <S> So now, your pilots are operating on quite seriously decreased vision for a substantial amount of time. <A> Even temporary blindness, however, is something I think any pilot would consider an emergency. <S> A fairly recent Daily Mail article states that "the FBI noted that several commercial pilots earlier this year suffered significant injuries including a burnt retina. <S> " There are over 4000 reported incidents a year, and the number is apparently increasing rapidly. <S> It is now a federal crime that has at least in one case resulted in prison time. <A> You can legally buy lasers that are certainly able to damage someone's eyes. <S> They come with laser warnings for a reason, and being lasers, the intensity does not decrease much with distance. <S> People with more powerful lasers could do even more damage. <S> This laser safety site has good info about the effects it has on the pilot and what can happen to you if you are caught doing this. <S> Here is another article where the pilot suffered injury. <S> Laser illumination has not been identified as a factor in any accidents involving loss of life so far, but considering how many happen and the fact that they happen more and more often, it is certainly a hazard to safety and cause for declaring emergency. <S> Although many people charged with this crime claim their intentions were not malicious, that is certainly not always the case. <S> Police helicopters are often targets, and this recent incident in Egypt is a notable example.	Some of the cheap, powerful lasers available now are capable of blinding pilots and in some cases causing lasting injury.
Is there a limit of how close a runway can be to the water? Somtimes planes can either come up short or overrun a runway, ending up in the water. Is there some limit for how close a runway can be to the water? Does it factor into the runway safety area that is required to be clear of obstacles (i.e., is water an obstacle)? Is there any requirement for displaced thresholds near water? I am asking primarily about the US, but information about any other jurisdictions is welcome. <Q> FAA Advisory Circular (AC) <S> 150/5300-13A covers "standards and recommendations for airport design. <S> " It does not include any restrictions on proximity to bodies of water, but it does make the following recommendation in paragraph 319(a): It is recommended that the entire RSA and RPZ be accessible to rescue and fire-fighting vehicles such that no part of the RSA or RPZ is more than 330 feet (100 m) from either an all-weather road or a paved operational surface. <S> Where an airport is adjacent to a body of water where access by rescue personnel from airport property is desirable, it is recommended that boat launch ramps with appropriate access roads be provided. <S> The actual FARs ( 14 CFR 139, Certification and Operations: Land Airports ) also do not state a limit. <S> The only reference to bodies of water of any kind is in §139.325 (Airport emergency plan) paragraph (e): <S> The plan required by this section shall contain provisions, to the extent practicable, for the rescue of aircraft accident victims from significant bodies of water or marsh lands adjacent to the airport which are crossed by the approach and departure flight paths of air carriers. <S> A body of water or marsh land is significant if the area exceeds one-quarter square mile and cannot be traversed by conventional land rescue vehicles. <S> To the extent practicable, the plan shall provide for rescue vehicles with a combined capacity for handling the maximum number of persons that can be carried on board the largest air carrier aircraft that the airport reasonably can be expected to serve. <S> So, bottom line: there is no limit, but airports are required to take water into due consideration when developing emergency plans, and the FAA looks at each airport and plan on a case-by-case basis during airport certification. <S> As for the rest of the world, I have no authoritative information; but as others have posted, it certainly seems like the situation is the same, there being numerous examples of airports worldwide built on natural or reclaimed land very close to water. <A> There is no such limit indeed. <S> Princess Juliana International Airport in Sint Maarten is possibly the most iconic example of airport located near a water body, because of the beach over which airliners fly when approaching RWY 09. <S> As other mentioned, they are numerous other examples of airports that may be even closer to a water body (i.e. without a beach in between). <S> image source <A> Water is not an obstacle. <S> There are plenty of examples around the world where runways are built on purpose-reclaimed land and the ocean starts just a handful of meters from the end of the runway. <S> For some random examples, check Nice-Côte d'Azur or Gibraltar or St. Maarten. <A> Runway 28L and 28R at KSFO , as well as 19L and 19R, have their thresholds right next to the San Francisco Bay. <S> If you recall, in July 2013, Asiana Airlines Flight 214 landed short due to pilot error. <S> In November 1968, Japan Airlines Flight 2 completely missed the runway and landed in San Francisco Bay. <A> Not going by Barra Airport - Barra Airport is famous for its beauty - boasting beaches, machair and hills - and all in a small island; Barra is a special place to visit - especially memorable if you fly in because of the beach landing strip. <S> Washed by the tide twice a day, Traigh Mhor beach is reputed to be the only beach runway in the world to handle scheduled airline services . <S> See Barra Airport website <A> I'll expand for ICAO regulated airports, but this is also true for FAA ones. <S> ICAO defines an area surrounding a runway, called runway strip, which purpose is to: a) to reduce the risk of damage to aircraft running off a runway; andb) to protect aircraft flying over it during take-off or landing operations. <S> A water runway strip would not reduce the risk of damage to aircraft running off a runway. <S> It would in fact increase it, so a runway strip cannot be made of water. <S> The size of the runway strip depends on the type of runway, but it ranges 150 m to 0m (zero) in width, and it must extend 30 to 60 m beyond each end of the runway (or the end of the stopways, if there are any). <S> So, the runway strip contains at least the runway (and its stopways) and extends beyond it on its ends, and sometimes (depending on the type of runway) it also extends to the sides of the runway, and it defines the limits to how close a runway can be to water. <S> Airports such as Sint Marteen, where the runway is almost 190m from the water, are just examples of how the runway strip and the RESA are applied as safety measures against aircraft running off a runway. <A> Here is Albert Whitted Airport , a GA facility in St. Petersburg, FL, which has actually juts out into Tampa Bay.	Going even further, ICAO defines a Runway End Safety Area (RESA) for some types of runways which further increases the minimum distance of water to the runway. The answer to the question is yes, there are limits.
Can I be a commercial pilot if I've had a dental filling? Is there something like a health requirement in serious airlines? Or is it just a myth? How are potential pilots screened when it comes down to physical requirements? <Q> Here are the mouth and throat requirements for a pilot physical. <S> The main thing is that it shouldn't affect your ability to fly (i.e. having pain) and ability to communicate over the radio. <S> Commercial pilots who don't fly regular schedules need a Class 2 medical certificate. <S> Regular schedule commercial pilots need a Class 1. <S> FAA Class 2 medical requirements FAA Class 1 medical requirements <A> The major requirement for dental fillings as far as aviation (or diving) is concerned is there not be a trapped air pocket under the filling (this could cause problems for divers or pilots as the pressure changes may cause discomfort. <S> (It's called barodontalgia - pressure-induced tooth pain.) <S> Air pockets are something your dentist will try to avoid anyway because they promote further decay & will eventually require more work on the tooth, so if your dentist is competent you shouldn't have any problems. <S> If you do notice discomfort while flying mention it to your dentist - <S> an X-Ray can usually identify the problem in a few minutes, and your dentist can then take care of it (replace the filling, or if it's a new cavity treat it appropriately). <A> Dental fillings, false teeth, implants are all permitted so long as the mouth is healthy and there are no abcesses. <S> I don't have that reference here with me now, but perhaps someone can post either a link to the requirements for a first class medical, or list the requirements here.	Commercial pilots need a first class medical certificate.
How are airspace fixes named? Aircraft use nav fixes as waypoints or reporting points along their routes. I have noticed some interesting combinations. Some make sense, like LUCKI to LYNDI on the LYNDI arrival into San Diego International, known as Lindbergh Field, or KSINO LUXOR on the GRNPA arrival into Las Vegas. Some are more interesting, like HIMOM KALME on the FRNCH arrival into Denver, or ASTAH LVSTA ADYOS on the ADYOS departure from Albuquerque. Some get downright suspicious, like ITUNE MUSCC DWNLD on the LOWBO arrival into Albuquerque. So my question is: how do these points get named? These combinations are memorable, but are they also allowed to be sponsored? Or is this a case of "Any resemblance to actual entities is entirely coincidental." <Q> As well as the FAA's part mentioned in dvnrrs's answer , they are also part of ICAO's 5LNC (Five-Letter Name-Code) system, which records available pronounceable 5 letter codes <S> (they don't have to be words). <S> While these are meant to be unique, there are several cases where different countries have duplicate names from legacy naming systems. <S> As of February 2014, there are 130 codes that are duplicates of others in other countries. <S> Usually, there is usually some form of selection to prevent similar-sounding names from being used as a 5LNC in the area. <S> For example, the UK Civil Aviation Authority states that (emphasis mine): <S> Where a significant point is required at a position not marked by the site of a radio navigation aid, the significant point shall be designated by a unique five letter pronounceable ‘name-code’ (5LNC). <S> This name-code designator then serves as the name as well as the coded designator of the significant point and shall be selected so as to avoid any difficulties in pronunciation by pilots or ATS personnel when speaking in the language used in ATS communication. <S> The name-code designator shall be easily recognisable in voice communications and shall be free of ambiguity with those used for other significant points in the same general area . <S> The name-code designator assigned to a significant point shall not be assigned to any other significant point. <S> (Reference B) <A> In the US, they are assigned by a division in the FAA called Aeronautical Information Management (AIM) , per FAA Order JO 7400.2J <S> (Procedures for Handling Airspace Matter), section 3-3-2: a. Service area office are responsible for assigning and changing names of NAVAID and aeronautical facilities, and must follow the instructions contained herein and in FAAO JO 7350.8, Location Identifiers, Chapter 1. <S> b. AIM is responsible for issuing five−letter names for radio fixes, waypoints, marker beacons, and compass locators. <S> Five−letter names must be issued by AIM to the Terminal Procedures and Charting Group, Major Military Commands (MAJCOM) and Air Route Traffic Control Centers (ARTCC) for future assignments. <S> It's conceivable they accept suggestions from ARTCCs or other entities. <S> I don't know. <S> I doubt paid sponsorship is approved but have no first hand knowledge there. <S> Suggestions are probably casual and intormal. <S> They are often quite amusing, like <S> ITAWT ITAWA PUDYE TTATT . <A> Note, my answer that follows is per the US, and having been involved and discussed various naming of fixes and routes. <S> Paid sponsorship doesn't happen. <S> Usually it's the ATC facility that suggests names, and check the existing and reserved names lists.. <S> For SIDs/STARs, the divide is usually the TRACON names the SIDs and the Center <S> names the STARS. <S> For random fixes that don't have to be as pronounceable(lots of RNAV approach fixes/intermediate fixes on arrivals), they can just be randomly assigned as long as they stand a chance of being able to be pronounced. <S> Controllers have a sense of humor and will see what they can get away with in terms of naming fixes. <S> They have been named for people, both controllers, or people from the area. <S> They can be a joke like the above mentioned <S> ITAWT ITAWA PUDYE TTATT. <S> Though a lot of the more historical fixes on Victor and Jet Airways are named for towns or features they're near.	Very often enroute fixes are named for small towns or other points of interest near the fix.
Why is the total count of people on a plane given as the number of 'souls' on board? Why don't they just say 'people' on board, why souls? What is the origin of this term? I'm thinking it comes from sailing as I think I've heard that term in reference to crews out at sea, but I'm not a sailor so I don't know. <Q> The primary reason is probably that it ensures there is no confusion between passengers, crew, or infants. <S> Technically, "passengers" is the number of seats occupied, "crew" is both the pilots and flight attendants on duty. <S> So any small children brought on as "lap children" will not be included in the "passengers" count, but should be included in the total number of people on board. <S> I found another interesting point over on the English Stack Exchange site , which is that dead bodies are sometimes transported as well. <S> In this case, some might consider these "people" as well. <S> Also, in an incident, the bodies should not be confused with the regular passengers. <S> There may certainly be holdovers from the maritime influences on aviation as well. <A> I agree with what fooot said . <S> Also, I would add, as someone to volunteers in search & rescue (Civil Air Patrol) as a mission pilot, <S> when you hear the word "souls," it adds some urgency and seriousness to the handling of any emergency. <S> When an air traffic controller asks a pilot, during an emergency, for the number of souls on board, it communicates to the pilot that the controller and pilot are focusing extra hard together on solving the emergency successfully, and that one word tells the pilot that the controller is going to be marshalling resources to help in every way possible. <S> "Souls" is a term full of life and caring. <S> For rescuers, it communicates very quickly the total number of persons who must be found and saved. <A> The earliest reference I can find to 'souls' as a count of persons is mid-eighteenth century, although it probably was in use earlier. <S> It appears in maritime commerce, as the number of living humans aboard a ship, and in civics, as the population of a town or city. <S> I think that in the early 1700s the words 'people' and 'person' both had strong connotations compared to those words today. ' <S> People' meant humans of a certain country or a specific culture, and 'persons' meant humans of note or important characters. <S> So I conclude that a need arose, driven by government and commerce, for a word to mean an unaffected and precise head count, that yet afforded those being counted a little more respect than the barrels, boxes, coins, and cows whose numbers were also tallied. <S> Now if I could find a reference to that usage of 'souls' from the thirteenth or fourteenth century, I would simply assume that it arose from the learned churchmen who were doing the counting, as literacy was not yet widespread. <A> The term Soul appears many times throughout scripture, Hebrew translation of this particular use and meaning is literally "breather. <S> " Some are on the right track with anatomical heart as this is what is required to circulate oxygen. <S> This also clarifies why transporting deceased persons are not counted among SOB. <S> They are no longer breathing. <A> Aircraft (and previously, ships or trains) are frequently used to transport casketed remains en route to funeral. <S> " <S> Souls" was devised to remove any ambiguity about which "passengers" were among the living. <A> The term "soul" once meant a whole person: body and spirit. <S> Thanks to Hollywood's love affair with the word, most now believe it means spirit. <S> The sad result of this is several phrases now have a different meaning than the historical writings that contain them once intended. <S> "not one soul was saved" - everyone died, now means they are all dammed "bless his soul " - may he have a long life (literally blessing the integrity of the body and spirit), now means bless his spirit <S> "soul mate" - a person physically and spiritually matched, now means a single special someone that is primarily a match of the spirit <S> "he sold his soul" - he has given his life to evil, now means a state of evil that primarily affects the after life "bare one's soul" - to share the intimate details of once physical and spiritual life, now means to reveal primarily emotional details as a stand-in for spiritual things "rest his soul" - implying that sleep is symbolic of death, now solely a blessing on the spirit "lost soul" - a person not doing well physically and spiritually in this life, now means a person not following spiritual paths <A> It used to be "souls on board", but was frequently abbrievated to 'sob's", which somehow didn't sound right. <S> It is now "persons on board"; but there's a lot of momentum in the aviation business and "souls on board" is still used by many	So, "souls" effectively communicates the number of living humans on board.
Why can't an airplane stall at zero G? You may be surprised to find out that an airplane can stall at any attitude if the critical angle of attack is exceeded, but it cannot stall at 0 G. This quote found in the April 2014 issue of Flying magazine , but it seems counterintuitive to me. Why can't an airplane stall at 0G? <Q> At 0 G the plane does not need to generate any lift, therefore there is no critical angle past which <S> the airfoil cannot generate the lift required. <S> In addition, a sustained 0 G maneuver is a parabolic arc, which means that in theory your flight path should keep your angle of attack at zero the entire time (in a theoretical, symmetrical airfoiled aicraft). <A> It's probably more accurate to say "you cannot maintain 0 G in a stall". <S> Even a stalled airfoil generates some lift -- the stall just means that the lift coefficient drops below the best the airfoil can do, not that it becomes zero. <S> Since the stalled wing produces lift, and this lift is generally not in a direction where it can be canceled out by thrust, it will pull the aircraft away from the freefall trajectory. <S> And even that isn't completely true in the theoretical extreme. <S> If we imagine an aircraft with fully variable angle of incidence (never mind the engineering problems in building such a thing), we can imagine rotating the wings up to around 90° angle of attack. <S> Then, by symmetry, they will not produce any lift, yet it will be fully stalled. <S> There will be lots and lots of drag, but sufficiently powerful thrust can offset that and make the net motion of the aircraft follow a zero G / freefall trajectory. <A> Look at it backwards. <S> Why are you at zero G? <S> Because your downward acceleration is equal tothe acceleration due to gravity. <S> Why are you accelerating downwards so fast? <S> Because you're not creating any lift to counteract gravity. <S> Why are you not creating any lift? <S> Because you are at zero degrees angle of attack! <S> And that's why you can't stall at zero G. <S> You're always also at zero degrees angle of attack (you can get pedantic, depending how you measure it) when you're at zero G. <S> And stalling is always caused by high angles of attack. <S> And if that doesn't make 100% sense, you should look more into stalls before you dig too deep into how G loading affects stall speed. <S> EDIT: <S> Many people here seem to be replacing the world "airplane" in the question with the word "wing". 0 <S> g flight involves the entire airplane, not just the wing. <S> Sure, you could take a Cessna, strap highly controllable rocket engines to the top of it and drop it from another airplane. <S> Then, use the rocket engines to counteract drag and give downward acceleration equal to the force of gravity. <S> That would give you a stalled wing and 0g. <S> But that's not really an airplane anymore, and it doesn't really answer the question. <S> That means it must have an angle of attack above zero. <S> That means lift is being created, which means an upward force is acting upon the airplane. <S> That means you are no longer at 0g. <S> The point isn't that once an airplane is at 0g <S> it becomes unstallable. <S> The point is you have to leave 0g to stall it. <S> It's also an example of how airspeed is irrelevant to stalling. <S> (Sounds crazy, since we talk about stalling speed!) <S> Stalling isn't about the speed or amount of air flowing over the wings, it's about the angle, path and flow. <S> A wing on the same airplane can be not stalled at 5mph, or stalled at 100mph. <S> It just depends on the angle. <A> Critical angle of attack or stall angle of attack is by definition the maximum angle at which the stream over the airfoil is still attached. <S> It is also the angle of maximum lift. <S> Beyond this angle, the stream over the airfoil becomes unattached, leading to a sudden decrease in lift . <S> Now, I think the article is somehow misleading. <S> I think what they mean by stall is the airplane lift not being able to compensate weight. <S> Since the weight in 0G is 0, then obviously it won't "stall" in this definition. <S> A harder question is whether the airfoil can stall in 0G according to the actual definition. <S> Well, if the airplane is free falling in a straight line with its wings parallel to the ground, the airfoil is stalling, but in reality it will likely enter spiral dive, the airfoil will produce lift (which produces the centripetal force of the spiral) and won't be 0G anymore. <S> An airplane is so that it will naturally adapt to the relative air stream, so it's hard to maintain 0G. <S> You do this following a ballistic trajectory, on which at the top portion of the trajectory you get a short free fall feeling, where the airfoil is not producing lift (zero angle of attack). <S> source: <S> http://en.wikipedia.org/wiki/Low-g_condition <S> http://en.wikipedia.org/wiki/Angle_of_attack#Critical_angle_of_attack	To stall, the wing must exceed the critical angle of attack. You can't stall because your AoA is constantly 0 degrees and cannot exceed the critical angle.
Have B-25's and B-26's been converted for private business use? In the movie Cash McCall , the main character, McCall, owns an aircraft that looks remarkably similar to a B-25 or B-26, but is painted yellow and has no turrets. Have these aircraft been converted for private business use or were there business aircraft based on the design of WWII bombers? <Q> IMDB : <S> Since the film was made in 1960, I imagine there were plenty of them around. <S> (The A-26 was known a the B-26 from 1948 to 1965, according to Wikipedia . <S> The B-25 is easily distinguished because it has the twin tail.) <A> Yes. <S> After World War 2, surplus aircraft were cheap, plentiful, and offered great performance compared to pre-war designs, and many were converted to use as executive transports. <S> The A-26/B-26 was no exception, being the basis for the On Mark Marksman series. <S> Some of the On Mark conversions involved pretty serious modifications like a new wing spar carrythrough and a new (and much uglier) cockpit. <S> The B-25, to my knowledge, had no comparable program carried out, but many became water bombers for use in fighting forest fires. <S> There were undoubtedly some executive conversions made as well! <S> Other types like the Lockheed Hudson/Ventura/Lodestar transports and patrol aircraft were also popular conversion choices. <A> The aircraft is a modified Douglas A-26 Invader. <S> As mentioned in an earlier reply there were several companies which undertook such work. <S> Most well known was On-Mark Engineering of Van Nuys, CA. <S> The 26 in question, N36B was one of several (at least two used the same reg.) <S> owned by citrus tycoon Willis (Bill) Bailard of Santa Barbara, CA. <S> He had at least three of them over the years. <S> Possibly four. <S> Including an unpressurized On-Mark Marketeer. <S> This example does not have the ring- spar <S> mod as later versions did, <S> and I suspect that it is an earlier Grand Central exec. <S> version. <S> Note also in the movie that the 26 still has the fittings for the upper turret installed. <A> Here is a list of surviving B-25 <S> which may provide some references. <S> It looks like Redbull has one that they fly around (arguably for business reasons) <A> I remember Air Spray Ltd., at Red Deer, Alberta, had a highly modified A26 bought from the Mexican government that used to fly around call girls as the interior of the plane had a fully plush white shag carpet everywhere <S> and you could fully stretch out with your hostess. <S> It also had curtained windows in the back area and a bed type platform in the sealed bomb-bay area. <S> It also had an extra long nose cone with a small kneeling shower stall that had heated water pumped from a water tank in the nose section. <S> Just enough for rinsing off. <S> The A26 outside color was white with a nose to tail medium blue stripe half way up and Mexican registration.	McCall's plane is a demilitarized Douglas A-26 Invader, a type used in WWII.
Why do parked planes lock the control surfaces? After a discussion in chat about control surface locks I was wondering why they need to be locked in the first place. Why do they need to be locked? What is the best position to lock them in? up, down, neutral. <Q> In the small planes I fly, it is called a "Gust Lock", and consists of a small metal bar that fixes the yoke in position, so that the yoke cannot move (left/right, or forward/back), and by association, the ailerons and elevator cannot move either. <S> As the name implies, this is for dealing with Gusts of wind... <S> a sudden bit of wind over an unlocked surface can move the surface to its extreme position until it hits a mechanical stop. <S> If this happens repeatedly, say, over a stormy night, the repeated banging into a mechanical stop can create wear and tear on the surface, the control cables, or the yoke in the cockpit. <A> Other folks have already addressed why we want to lock the flight controls when we leave the aircraft - "to prevent damage from gusts of wind", and "to keep the plane from doing interesting things in a strong breeze". <S> To the question of the "best" position to lock controls in, for light aircraft <S> the general consensus is that the rudder and ailerons should be locked in the neutral position - <S> In this position any wind blowing over the wings will cause them to lift uniformly, putting tension on the tiedown ropes holding the aircraft to the ground. <S> (If the ailerons are locked at an angle one wing will generate more lift than the other, allowing one of the tiedown ropes to go slack.) <S> Elevators are a subject of a little more nuance and debate: It's generally considered best to lock the elevator in the "nose down" position (because any gusts of wind over the tail will push the nose down, rather than encouraging the nose to lift, this also means that those gusts will apply tension to a tie-down rope located at the tail rather than causing it to go slack). <S> On some aircraft locking the elevator in the nose-down (or nose-up) position opens up spaces that birds may try to nest in ( for example, check out the tail of this Grumman ) - some pilots prefer to lock the elevator of these aircraft in the neutral position to discourage avian visitors. <S> This often results in a "sub-optimal" control position (elevator fully nose-up, ailerons full-deflection left or right), but because the wind speed at which control surfaces may bang against their stops is usually lower than the speed at which the aerodynamically unfavorable control positions will substantially affect the aircraft this is a "lesser of two evils" approach. <A> For gliders (probably other aircraft as well), there are two reasons to fix ailerons, elevator (and rudder) positions: <S> You want to avoid uncontrolled (potentially damaging) <S> sudden movements caused by (repeated) wind gusts. <S> If you choose or allow unlucky positions/configurations, your plane might exhibit unwanted positional initiative (e.g. an aileron might motivate one wing to lift unexpectedly, hitting heads, tarmac or other obstacles). <S> In mildly gusty conditions, wings are often temporarily fixed by additional weights (usually old tires or similar) to avoid that, too. <S> As mentioned in the comments, this is not sufficient for anything more than average winds.	Generally it's better to lock the controls than leave them unlocked to bang around in the wind, so on some light aircraft not equipped with control locks pilots use the seatbelt to hold the controls in place.
Have any passengers crashed planes? The question Are pilots allowed to let passengers fly the plane? is interesting to read, noting that pilots are permitted to allow passengers to fly. I recall an Air Crash Investigation episode ( AFL593 ) where the pilot pretended to allow his son to manipulate the controls of an airliner, without realising the autopilot had been disconnected, resulting in an accident. I'm wondering how commonplace this is? Is this an isolated incident? On the flip-side, I've heard of at least 3 occasions where passengers have successfully landed planes, e.g: <Q> No passengers have crashed an airplane while the pilot was letting them fly. <S> In this situation, the PIC crashed the plane because he didn't do his job as the captain and final authority for the safe operation of the airplane. <S> Letting a passenger fly would most likely be listed as a "contributing factor" by investigators looking into an accident where this happened, but responsibility for the crash lies squarely on the PIC. <A> Please see the transcript of Aeroflot 593 Overview: The pilot allowed his 12 year old and 16 year old children into the cockpit to sit in the pilot's seat of an Airbus A310. <S> The older child's actions disconnected the autopilot. <S> All aboard were killed when the crew was unable to recover from an unusual attitude after the autopilot disconnect. <S> Another possible passenger-caused accident is the death of Thomas J. Stewart and his family in a Eurocopter EC135 in Phoenix. <S> Stewart allowed his 5 year old daughter to sit in his lap during the flight. <S> The NTSB concluded that the daughter kicked the controls and that the pilot's recovery attempt severed the tail. <S> Both Stewart and his daughter were passengers and may have caused the accident with their actions. <A> There was a passenger who crashed an light aircraft over Bodensee in Austria. <S> Psychological factors were assumed to be the reason the passenger forced the controls forward crashing the plane into the lake. <S> He and the pilot were killed. <S> Source: Der Standard (in German) <A> I recall an Air Crash Investigation episode <S> Aeroflot flight 593 <S> Moscow–Hong Kong, Airbus A310-300, Russia, <S> 23 March 1994 where the pilot pretended to allow his son to manipulate the controls of an airliner , The pilot actually allowed his son to manipulate the flight controls. <S> The A310 has a conventional yoke. <S> The autopilot was engaged at the time, so small movements of the flight controls had no effect. <S> The pilot pretended to his son that he was in full control. <S> Large, forceful movements contradicting the autopilot caused the autopilot to relinquish control to the pilot (the autopilot assumes the pilot knows best) - in this case, control over ailerons (but not over pitch, airspeed, altitude, throttles etc). <S> Pilots are not dropped into new aircraft without training to understand how use of the controls affect the autopilot. <S> The pilot's actions were reckless and he failed to monitor the childs actions and their effects. <S> A310 cockpit - Image source without realising the autopilot had been disconnected The appropriate indicator light illuminated to show that there was manual control over ailerons <S> but it seems the pilot was too busy entertaining his child to pay proper attention to flying the aircraft. <S> The "cavalry charge" audio alert only occurs when the autopilot is fully disengaged. <S> lights on the instrument panel show what aspects of flight the autopilot is controlling. <S> It was actually the child who first noticed that the aircraft was banking! <S> resulting in an accident. <S> In combination with inappropriate actions by panicing pilots. <S> Despite the struggles of both pilots to save the aircraft, it was later concluded that if they had just let go of the control column, the autopilot would have automatically taken action to prevent stalling, thus avoiding the accident.[11] <S> (Wikipedia) <S> I'm wondering how commonplace this is? <S> Is this an isolated incident? <S> No. <S> See dawg's answer . <S> It may be the only case on an Airbus.	It seems to be very uncommon for children and/or other passengers to enter the cockpit midflight and cause a crash.
Is it illegal for Joe Public to listen to ATC in the UK? I recall that in the UK (unlike in the rest of the world) we have a law forbidding the listening to of air traffic control, dating back a century, to the days of paranoia over spies! What is this law, exactly? Is it illegal for a member of the public to listen to live ATC in the UK? Are there any exceptions? It seems like something of a grey area, but some sources claim that listening to a delayed feed (or historical recording) works around this law; is this true? <Q> Yes, it is illegal . <S> The UK has some very strange ideas about Radio, which bear no resemblance to the reality of physics and how radio actually works. <S> Foremost among those ideas is the idea that you are only legally allowed to listen to transmissions intended for "general reception": <S> The services that can be listened to under the definition of general reception are: licensed broadcasting stations; amateur and citizens' band radio transmissions; and weather and navigation transmissions <S> Radio scanners should not be used to listen to any other radio services, including illegal radio stations (pirates) (by virtue of the fact that they are not licensed radio stations). <S> Aviation-band transmissions are not on Ofcom's list, so even though they are broadcast entirely "in the clear" and anyone with an appropriately tuned AM receiver could hear them you are legally prohibited from listening to them. <S> Providing feeds to LiveATC would also appear to be a violation, though it's not clear to me that listening to LiveATC streams would put the listener in violation of the law. <S> and … it is also illegal to tell a third party what has been heard in a transmission a person has listened to illegally. <S> So anyone providing UK aviation band transmissions to LiveATC may be in violation of both of those laws, but I'm not certain what that means for LiveATC <S> listeners <S> (that would be a question to ask Ofcom). <A> UK's OFCOM, the Independent regulator and competition authorityfor the UK communications industries write <S> Q. Isn't this all a bit heavy? <S> A. No. <S> No-one likes their private or business conversations to be listened to. <S> Parliament has passed these laws to protect the privacy of radio users <S> Obviously this appears pretty futile to many people, me included. <S> Practicality or enforceability of law is not an issue that prevents legislation. <S> There are other laws that are more obviously justifiable but which relate to actions that are equally difficult to prevent. <A> Strictly speaking it is against the law, the transmission is not intended for public reception (indicated by it falling outside of public broadcast frequencies) <S> and you are not the intended recipient. <S> However you will find that in practice this is ignored on a personal basis. <S> i.e. yourself listening nobody has a problem with, if you were to then make what you hear available elsewhere whether via retransmission, recording or transcript I would expect a knock on the door from Ofcom <A> Basic legislation within the EU, specifies that your are allowed to listen to any type of information available on the electromagnetic spectrum. <S> It is up to the users to protect said information by using encryption if so required. <S> This is not to say that there is not some very restrictive legislation in place in some countries. <S> They just hate the thought of their citizens getting informations of almost any kind. <S> Ignore the law and take your complaints to the courts in Brussels. <S> The local authorities will hate you for that, but you will probably win the case.	From the same Ofcom site: … it is illegal to listen to anything other than general reception transmissions unless you are either a licensed user of the frequencies in question or have been specifically authorised to do so by a designated person. Yes it is illegal.
How do pilots decide what their cruising altitude will be? When filing a flight-plan for a long-haul high-altitude IFR flight, how do pilots select a specific cruising altitude? Typically in the range of 25,000 - 35,000 ft. <Q> As has been stated, ATC will assign you an altitude, taking into account your requested altitude, traffic conditions, and of course the FAR. <S> Peter's formulas will apply from a design standpoint. <S> The aircraft designer will use something like that to calculate typical values, which will be included in the aircraft's operating handbook. <S> The table below is listed by pressure altitude and gross weight. <S> At each combination there will be performance values such as: <S> Average N1 (for a turbine) Max TAT for thrust rating <S> IAS Knots <S> Mach number <S> ISA fuel flow LB/HR/ENG ISA TAS Knots <S> The flight distance will determine the approximate gross weight, which corresponds to an altitude and cruise speed that provide the best efficiency. <S> Here is an example from a virtual 737 handbook, with the values I listed. <S> The optimum performance is in blue. <S> Higher gross weights have been removed for clarity. <S> Dispatchers for the airline will take the flight information and decide on a cruising altitude for filing the flight plan, which the pilot will then receive. <S> As you can see, as the aircraft burns fuel and gets lighter, it will be more efficient at higher altitudes. <S> This is the step climb that Peter mentioned, where the aircraft will climb to higher altitudes as the flight progresses when they are cleared by ATC. <S> Modern planning systems can take into account weather factors such as winds aloft and turbulence to pick the most efficient route. <A> I guess you know the FAR rules for picking discrete values. <S> When it comes to performance, with a jet you want to fly as high as possible. <S> The only reason not to do so is total distance; on a short hop there is not enough flying time to climb all the way up. <S> The higher you fly (in the troposphere) <S> the colder the air is, which makes the thermodynamic cycle of all air-breathing engines more efficient. <S> Also, the air gets thinner, so your friction drag is reduced at the same TAS. <S> The specifics depend on the thrust over airspeed, and generally you want to fly at a lift coefficient between $\sqrt{\frac13\cdot <S> c_{D0}\cdot\pi\cdot AR\cdot\epsilon}$ and <S> $\sqrt{c_{D0}\cdot\pi\cdot AR\cdot\epsilon}$, where $c_{D0}$ is the zero-lift drag and $AR$ the wing's aspect ratio. <S> The higher value is perfect for piston engines and props, and the lower one for turbojets (think fighter aircraft engine). <S> With a turbofan you will be between both values. <S> To yield more precise results, both formulas will be longer, but these are the major factors for optimum lift coefficient. <S> Since there is an optimum cl for maximum range, you might want to climb continuously during the flight to compensate for the lower mass (due to fuel burn) with lower air density, so in reality you adjust altitude in steps, in accordance with traffic control. <A> Cruise altitude may be assigned by ATC for separation (IFR especially, or in other controlled airspace -- since, in the US, these altitudes would be Class A and controlled airspace). <S> For example, when you request a DUAT(S) briefing, it will usually give suggested ATC routing and also altitude assignments (along with what's most frequently used). <S> The altitude you request somewhat depends on aircraft performance, I would imagine, but obviously any ATC clearance must be adhered to unless amended. <S> Hopefully one of the commercial pilots can fill in more of the blanks, though. <S> See also: Choosing an Appropriate Altitude	Airlines may have their own performance tables, choosing a custom balance of efficiency and speed.
Is there a general radio frequency in Class G for broadcasting intentions? Let’s say you’re in class G and doing some aerobatics. Is there any standard frequency you might use (perhaps MULTICOM on 122.9?) to communicate your intentions? Assume you’re not using flight following and that you’re VFR. <Q> I'm not aware of any regulation or AIM entry that specifies what frequency to be on. <S> I use the UNICOM frequency of the nearest airport when I'm out looping because I consider it to be the frequency most likely to be used by traffic near me. <S> It also has a mild safety benefit -- <S> if something on my plane were to break, I'd already be on the right frequency for the airport <S> I'm about to inhabit. <A> MULTICOM is used when operating in the vicinity of an airport that has no tower, no FSS, and no UNICOM so wouldn't be appropriate here. <S> There is an air-to-air frequency (122.75) but most pilots don't monitor it unless they have a specific reason to (i.e. someone else that they want to talk to). <S> 1 <S> In short, there isn't a good option for this, and in my opinion, <S> unless you have a spotter watching for traffic in the area it would be pretty hard to do safely since it will be very hard for you to watch the area for traffic while doing aerobatics. <S> Other pilots may also have a hard time spotting you because you could be approaching from odd angles. <S> If you can get flight following, I would highly recommend it, but there is an even better option: Practice in an Aerobatic Practice Area. <S> See <S> Where Do <S> Airshow Pilots Practice? <S> for more specifics on this. <S> Not only would ATC and airports in the area know where you were, but a NOTAM is issued any time that it is active to warn pilots transitioning the area. <S> 1 <S> See Services Available To Pilots for more details on communication frequencies. <A> The words "as well as" indicate that it isn't just for use around airports, and aerobatic practice certainly sounds like a "temporary" activity. <S> Of course, flight following would be preferable if it's available.	You can listen to the closest airport or approach control frequency, but that would only help if the other aircraft is on the same frequency. As far as I can tell, according to the AIM 4-1-11 you should use 122.9, which is described as follows (my emphasis): (MULTICOM FREQUENCY) Activities of a temporary, seasonal, emergency nature or search and rescue, as well as , airports with no tower, FSS, or UNICOM.
What is the bag for on a passenger oxygen mask? We may all be familiar with the part of the cabin safety briefing where they say that, in the event of a reduction in cabin pressure, oxygen masks will drop from a compartment above our heads, yadda yadda, the bag may not inflate. What is the purpose of the bag? <Q> Oxygen in passenger masks is either generated by oxygen generator or released from pressurized container via reduction valve. <S> In either case it is released at fixed rate. <S> But human breath is discontinous. <S> So the bag acts as a buffer. <S> You inhale the oxygen accumulated in it <S> and then it slowly refills while you are exhaling. <A> In addition to what our friend Jan Hudec mentioned: Wikipedia The mask may also have a concentrator or re-breather bag that may or may not inflate depending on the cabin altitude, which has (in some instances) made passengers nervous the mask was not providing adequate oxygen, causing some to remove them, who thereby suffered hypoxia. <S> AOPA <S> The partial rebreather is the most common. <S> With these, there's an external plastic bag that inflates each time you exhale. <S> The purpose of the bag is to store any unused oxygen, so that it can be inhaled with the next breath. <A> I can't actually track down the purpose of the bag; however, the FAA Oxygen Equipment guide <S> states that it is not for the purpose of mixing exhaled air with pure oxygen: <S> The phase-sequential continuous-flow mask looks similar to a general aviation re-breather. <S> However, both masks function differently, and the phase sequential mask allows the user to go to higher altitudes. <S> This mask uses a series of one-way ports that allow a mixture of 100% oxygen and cabin air into the mask. <S> Exhalation is vented to the atmosphere; as a result, the bag does not inflate. <S> [ emphasis mine ] <S> This mask can be safely used at emergency altitudes up to 40,000 feet.	Because of the construction, the bag seems to act as a buffer, as Jan Hudec states in his answer.
How do airliners get from the factory to the client if the aircraft does not have the required range? Today I flew on an Embraer 190 of Kenya Airways. Checking in the tech specs this aircraft has a range of roughly 2900 km. Considering it is built in Brasil, I was wondering how do they deliver it to Africa since they would have to cross the Atlantic Ocean which I suppose is more than 2900 kms of range it has available. Do they add temporary tanks and, of course, by flying the aircraft empty get more range out of it? <Q> Sometimes they do add temporary tanks. <S> Here's a picture of what Hawaiian Airlines had to do to get their fleet of 717's over the Pacific because they did not have the range. <S> There's a Cranky Flier blog post about this. <A> First of all, yes, there are tricks to get the aircraft fly farther. <S> You can leave the payload out, this will allow you to fill all fuel tanks without reaching the maximum take-off mass. <S> Less mass means less induced drag, so you can fly higher and at a lower fuel flow. <S> It will also allow you to install temporary tanks to carry even more fuel than the aircraft was designed for. <S> That is how small GA aircraft get transferred from the US to Europe. <S> This is a typical payload-range diagram with the three distinct points: <S> Maximum payload, maximum fuel and transfer range with no payload. <S> The slope between maximum payload and maximum fuel points shows how well the additional mass of fuel is converted into range (mostly due to engine efficiency), and the slope of the lower segment between maximum fuel and no payload shows how much the weight reduction increases range (due to induced drag reduction). <S> In jets and turboprops, you can use higher-density fuel (PDF) which gives you more energy per volume in order to get a few more percent of range. <S> And if all fails, you can disassemble the aircraft and ship or fly the parts over. <S> If the range is not sufficient, the plane will be small enough and will be designed for easy dis- and reassembly. <S> Short Belfast being loaded with JetRanger (own work) <A> I flew in a brand spanking new Airbus A320 on its maiden voyage from Toulouse, France to New York about 13 years ago. <S> We had to stop in Iceland and Newfoundland for fuel before heading to New York. <S> So I'm betting the jet <S> can easily make that crossing. <S> They do have to put down at the first airport to get fuel. <S> That flight is not one I'd care to do... <A> An Australian company I used to work for purchased a Jetstream 41 turboprop off an American seller. <S> With a range of only about 1400 kilometres, there was no chance of safely making it across the Pacific. <S> So the ferry flight went through Canada, Alaska, Russia, right down through south Asia to northen Australia. <S> So the answer is, when they can't extend the range far enough, they'll go the long way!! <A> I was chatting to one of the Pilots of Maldivian Air Taxi a number of years ago, who fly Canadian built Twin Otter's. <S> He remarked that one of the more interesting jobs for that carrier was the "Overhaul flights". <S> A few pilots spend almost all year ferrying their aircraft back and forth to Canada. <S> I don't remember the exact route but it involved lots and lots of stop-offs for fuel.	At Oshkosh every year (EAA Airventure) I hear about pilots crossing from Africa (the furthest western point) to the furthest eastern point of Brazil in a single engine small plane. I don't have the answer to your question specifically, but I would guess they either add temporary tanks and go from SBNT-GUCY which is not much further than max-range, or take the long haul through the US and Europe.
Why don't horizontal stabilizers have winglets? Winglets are used to reduce induced drag on the main wings of an aircraft as per explanations on wikipedia . Since they are very effective I was wondering why they are not installed also on horizontal stabilizers. For sure there must be some sort of induced drag being generated on horizontal stabilizers too as they are cutting through the air just as the main wings do. So why aren't there any sort of "minified" winglets available as an aftermarket installation (or, at least, I haven't ever seen some myself)? <Q> Horizontal stabilizers don't generate as much pressure difference as the wings. <S> Generally the stab deflections are very small in flight, and there's so much other drag during landing -- when the stab gets the most use -- <S> that wing vortices from the tail are probably the least of your problems. <S> Furthermore, the weight and trouble of adding little winglets to the horizontal stabilizers with larger actuators and hinges, for example, would probably outweigh the very slight aerodynamic benefit. <S> I could also imagine that since the airflow over latter part of the wing is complex and varied, find a good design solution would be difficult. <S> As @Federico points out, the DA42 has them, but that's a composite airframe rather than the metal construction you see in most Cessnas, for instance, where you have to be more conservative in construction. <A> Short answer: <S> In all cases these are not winglets, but fins. <S> Winglets are worse than an equal span extension and are only used if span should not increase: for limiting the wing's root bending moment, or for size limitations Putting them on the tail surface would not help to limit the wingspan: The horizontal tail can easily grow and still be much smaller than the wing. <S> There is no single case where winglets on a horizontal tail would have made sense. <S> What you see and might interpret as winglets are actually additional fins. <S> They stay in the general area of the vertical tail, so they do not increase the sideslip-induced rolling moment, and they do not increase aircraft height. <S> But they help to improve lateral stability, which had been worsened by a configuration change. <S> Example pictured below: <S> The Beech 1900 , a derivative of the Beech Super King Air . <S> The fins below the fuselage could not grow any bigger without risking ground contact during rotation, and the small stability deficit did not justify the development of a new tail section. <S> So the fins were added where they would cause the least amount of trouble. <S> Obviously, aesthetics were not considered. <S> Note the small planes at the bottom of the vertical tail <S> : The same trick was used to avoid increasing the size of the horizontal tail. <S> It could be argued that the horizontal tail of the Beech 1900 is a double decker. <S> And no, those horizontal fins are not "fuselage winglets". <S> So-called "winglets" on the tail of the DA42 <S> That is also the reason why the "winglets" are so much bigger on the MPP version of the DA42: They offset the destabilizing effect of the camera pod. <S> The canted tips of the original DA42 are working like an anhedral and create a compensating positive rolling moment for the vertical tail's negative sideslip-induced rolling moment. <S> Ideally, the whole horizontal tail would have anhedral, but it was preferred to keep the elevator hinge line straight. <A> So why aren't there any sort of "minified" winglets available as an aftermarket installation? <S> Actually the DA42 has them and in the MPP version they are even more pronounced <A> The induced drag from wingtip vortexes is mostly on lift generating surfaces, horizontal stabilizers don't generate that much lift. <S> That said there is a twintail design with double vertical stabilizer at the ends of the horizontal one; but that is not for reducing vortexes but for improving rudder response.	Stabilizer winglets on their own, when there's no pressure difference, would simply result in drag, whereas the main wing winglets are constantly effective while flying.
Does night takeoff and landing currency also count for daytime currency? My initial thought is that night currency satisfies daytime currency, but what gives me pause is FAR 61.57(a)(2) notes that a non-current pilot is allowed to conduct day VFR or day IFR flights without passengers to obtain currency. There is no mention of night flight being allowed. This seems to imply that day flights are required for daytime currency. <Q> Yes , night landings satisfy the requirements of §61.57(a)(1) for both nighttime and daytime currency. <S> The wording of the regulation is not crystal clear, and some (including me) have thought that the wording of (a)(2) required daytime landings for daytime currency. <S> This is not the case, per the following interpretation from the FAA (Springfield, IL FSDO, dated 16 April 2014): <S> Please note, in this section, there is no mention of a day or night differences in the regulation. <S> In 14 CFR 61.57(b) the regulation specifically mentions the requirement for Night Takeoffs and Landings and the time period they can be completed in. <S> If the passenger carrying will be done at night, the additional requirements of 14 CFR 61.57(b) must be met. <S> The night takeoffs and landings, as required by 14 CFR 61.57(b), will qualify for both the day and night requirement, provided all other requirements are met. <S> The day takeoffs and landings will NOT qualify for the night <S> (section (b)) requirement though. <S> Stanley E. Swank II <S> Aviation Safety Inspector Springfield, IL FSDO, AGL-19 <S> Other sources on the Internet agree with this interpretation: <S> Eric Gideon at askacfi.com : ... <S> your three takeoffs and landings to a full stop at night will also fulfill the recent flight experience requirements for day currency. <S> A thread at pilotsofamerica.com . <A> 61.57(a)(1) <S> explains: Except as provided in paragraph (e) of this section, no person may act as a pilot in command of an aircraft carrying passengers or of an aircraft certificated for more than one pilot flight crewmember unless that person has made at least three takeoffs and three landings within the preceding 90 days. <S> Period. <S> That's it. <S> Night currency limitations simply add an extra caveat to the above: you have to have done the landings to a full stop. <S> But what about 61.57(a)(2)? <S> It clearly says day VFR or day <S> IFR? <S> Your question is slightly misleading. <S> (a)(2) talks about how to regain currency after you've already lost it...and the quote in your question is incorrect. <S> You said this: a non-current pilot is allowed to conduct day VFR or day IFR flights without passengers to obtain currency <S> No! <S> The reg actually says: provided <S> no persons or property are carried on board the aircraft, other than those necessary for the conduct of the flight. <S> A non-current pilot is allowed to act as pilot in command in order to become current, so long as nobody is carried other than those individuals who are necessary for the conduct of the flight. <S> Such as the first officer, a flight instructor, or an examiner. <S> So why is there the day limitation? <S> Because there's no restriction on multi-crew operations at night. <S> 61.57(a)(1) <S> Except as provided in paragraph (e) of this section, no person may act as a pilot in command of an aircraft carrying passengers or of an aircraft certificated for more than one pilot flight crewmember unless that person has made at least three takeoffs and three landings within the preceding 90 days, vs 61.57(b)(1) <S> Except as provided in paragraph (e) of this section, no person may act as pilot in command of an aircraft carrying passengers during the period beginning 1 hour after sunset and ending 1 hour before sunrise, unless within the preceding 90 days that person has made at least three takeoffs and three landings to a full stop during the period beginning 1 hour after sunset and ending 1 hour before sunrise, and If you need to get current in a multi-crew airplane, you can. <S> (a)(2) says so. <S> You don't need to get current in a multi-crew airplane at night, because there's no restriction on multi-crew operations at night. <A> FAR 61.57(a)(2) is for the purpose of fulfilling (a)(1). <S> Meaning, if you are out of day currency than you must make day landings. <S> If are day current, then night landings will qualify to continue your day currency. <A> I just passed my PPL checkride a couple of weeks ago, and the examiner asked me this very question. <S> I said I'd have to look it up in the FAR, but as I started flipping pages he said don't bother... <S> 3 full stop night landings do satisfy the requirements for day currency.	Yes, night landings count for day currency.
Why is water in the fuel tank bad? I mean, on the one hand it seems kind of obvious, if you had a fuel tank that was mostly water then you would lack combustible materials for the engine, but I get the impression that having any water in the fuel tank at all is considered a really bad idea. Why is that? Is it all right to have a very small amount of water in the fuel tanks? Is there a defined percentage of liquid in the fuel tank that must be fuel in order to operate safely? (say 99.87% or something?) And does this differ from prop to turboprop to turbofan to jet? <Q> Fuel systems are in general fed by gravity, at least until the fuel leaves the tank, where sometimes (always if the tank is lower than the engine) <S> a pump pushes it toward the engine. <S> This means that fuel is generally extracted from the bottom of the tank (or slightly above the very bottom to avoid having small particles from the bottom of the tank clogging up the fuel filter, incidentally this also introduces the concept of unusable fuel , as the stuff remaining at the bottom of the tank, although there are a lot more factors to this). <S> Fuel is less dense than water, meaning it'll float on top of the water. <S> Or if you want to think of it the other way around, water is heavier and will sink to the bottom, right where you're trying to get your fuel to feed to the engine. <S> Water doesn't burn very well and the engine will stop. <S> Avgas is generally 0.72 kg/l and Jetfuel around 0.82 kg/ <S> l <S> (water being 1 kg/l, see have SI units work well that way?). <S> You'd have to pump all the water through the cylinder and out the exhaust, and I don't think this is generally possible in flight, especially right after takeoff which is generally the case when you have water in the fuel (could be right after switching tanks too though). <S> I don't know much about turbine engines, but I suspect they're less susceptible as the water will not prevent relighting the engine (the pumps will simply push the water out, <S> there's no cylinder that could fill up with water), and you'll generally be using up more fuel on the ground making the problem readily apparent. <S> This is pure speculation though. <A> Water in the fuel system is something of an over-inflated issue in aviation. <S> Most aircraft have unusable sections of the fuel tank that will hold upwards of one gallon. <S> That means that unless you have a gallon of water in the tanks it's unlikely that you'll be picking any up. <S> We sump the tanks before every flight because it's easy to prevent an issue, and we're also pulling out any debris which is a much bigger issue than water. <S> But if you're just running along and a bit of water sloshes into the fuel intake, it's unlikely that you'll even notice. <S> Now obviously an engine can't burn straight water, and that's why we have systems in place to mitigate how much gets into the system. <S> Small amounts of water injected into the engine will actually boost performance. <S> Water's heat-absorption properties allow it to (once injected) suck up much of the left-over heat from the engine's previous combustion cycle. <S> This means that the engine is cooled and less work needs to be done to compress the fuel/air mixture. <S> Upon combustion, the water vaporizes and expands much better than dry air, boosting compression greatly. <S> The practice of using water (and often alcohol) in engines is known as Water Injection and has been around for a long time. <S> However, putting too much water in the engine can over-boost compression, which can result in blown cylinders, cracked pistons, and many other forms of damage. <S> It can also lead to hydro-lock, which is when the expanded water vapor occupies more volume than the cylinder provides. <S> This can at best stall the engine, or at worse blow a cylinder. <A> Since water is more dense then kerosine, the water will sink to the bottom, where the fuel tank outlet also happens to be, meaning that if there is a sizeable amount, the engine will stop, since there's simply nothing to burn. <S> Approximate densities of a few fuels: <S> Water: 1 kg <S> /l <S> Kerosine: 0.82 kg/ <S> l 100LL: 0.72 kg/ <S> l <A> The other problem with water contamination is that it can freeze in the fuel lines at high altitude, effectively blocking the fuel line with ice, and preventing the fuel getting through. <S> Fuel treatments such as Liquid Engineering Fuel Set are recommended for preventing water from settling in fuel storage tanks, but not for aviation. <S> This is because the water will still be present in minute particle size,- suspended in the fuel , and burnt in the fuel. <S> But the tiny particles of water can still ice up at sub zero temperature. <A> Although I would agree that “because of ice” and poor combustion are probably the MOST important reasons, I thought I’d add that water can wreak havoc on many fuel quantity systems. <S> Most fuel quantity systems are a capacitance style system in which the fuel acts as the dielectric of a capacitor. <S> When water sits at the bottom of the tank, it can cause the dielectric value of the probe(s) to drop to essentially zero. <S> This can cause a myriad of problems ranging from inaccuracies to total system failure. <A> fuel tank corrosion will also be a problem at the lowest spot in the tank, where the water tends to puddle under the gasoline. <S> This is a very common problem in motorcycles during extended periods of disuse and can actually perforate the fuel tank.	A tiny amount of water probably mix with the fuel and simply reduce the power output slightly, whereas anything more will be drained from the tank first, and it'll be very hard to restart the engine.
Can aircraft other than rockets go to space? I always wondered if it was possible for planes and other aircraft to leave the Earth's atmosphere. Normal commercial transport airplanes can fly pretty high, but then they need air to get the speed boost from. Reactive engines seem like a better idea, but I don't know how much importance air has for them. Is it possible to get to space from Earth's surface using a non-rocket aircraft? <Q> Depends on what you mean. <S> Get to high altitude? <S> Yes you can. <S> It is really inefficient to get there, but some aircraft already do it. <S> Achieve a stable orbit and be able to maintain control? <S> For the sake of clarity, some definitions: reaction engine : includes both rockets and jets. <S> The engine pushes some mass in one direction and by reaction <S> it achieves thrust in the opposite one. <S> jet (engine): is used to refer to airbreathing engines. <S> The aircraft carries the fuel, but not the oxidizer; that is taken from the surrounding atmosphere. <S> rocket (engine): is used to refer to non-airbreathing engines. <S> The (space)craft carries both the fuel and the oxidizer. <S> No atmosphere is needed. <S> space : above 100km of altitude. <S> go to space : staying in space : <S> Images from xkcd <A> For certain values of "go to space", yes. <S> The Karman line (the altitude at which an airplane cannot generate enough lift to stay aloft at any speed slower than orbital velocity) is usually considered the lower edge of outer space. <S> This implies that with a powerful engine and enough fuel it's possible to "fly" up into space: you just keep gaining altitude and speed until you find yourself in orbit. <S> No aircraft has actually done this. <S> The <S> X-15 and SpaceShipOne were both able to reach that altitude in zoom climbs; neither went fast enough to stay there. <A> It depends what you include in "non-rocket aircraft". <S> Wikipedia has a whole article on " Non-rocket spacelaunch " which discusses the various options. <S> The short version is, there are no current space launch systems which do not use rockets. <S> The most practical one we know of appears to be space guns , which have been successfully used for sub-orbital launches (but are not practical for human spaceflight). <A> A jet engine can only accept air at around half the speed of sound. <S> If the plane is flying faster, the inlet system needs to slow the air down before accelerating it again. <S> Hence the higher the speed, the less thrust it can provide. <S> It is not like a rocket engine that always pulls with comparable force. <S> A plane needs to accelerate to Mach 25 or about to fly into orbit as a spacecraft, and this is only possible with a new type of engine. <S> Scramjet <S> that is a jet engine, not a rocket, could probably do this. <S> However this engine seems still under development and currently a rocket is required to accelerate to the speed under that this engine can even be started. <A> I'm not sure how you'd classify the proposed Skylon spacecraft spacecraft. <S> It would be an airbreathing reactive engine in lower altitudes but a rocket above 26 km. <S> It might be a game changer. <S> But this time I don't give even odds that Skylon will come to pass. <A> I recall hearing about F-15s making ballistic suborbital flights, by simply getting up enough of a head of steam to coast through near-space. <S> I don't think they actually went into "space" (100 km altitude) and they certainly didn't make orbit. <S> Does anyone else recall the specifics on this? <S> I can find some references online to using F-15s to test launch ASAT missiles, but my recollection was that the whole aircraft actually went high enough to get well above maximum cruising altitude. <A> No aircraft powered by engines which rely on atmospheric oxygen can operate outside of Earths atmosphere, 100,000 ft is approximately the altitude limit for air breathing aircraft using conventional fuels, higher sustained altitudes might be possible using liquid hydrogen, but the utility of very high speed and altitude performance as a means of avoiding interception is questionable today. <S> No air breathing aircraft is likely to outrun a rocket propelled Surface to Air Missile however apparently impressive it's performance statistics.	No, at those altitudes you do not have enough oxygen to keep your engines running, you have to bring your own (and thus use a rocket)
Do commercial aircraft have electrical outlets? As we see trains nowadays with sockets for you to plug your laptop into, as well as Wi-Fi on-board both trains and planes, I'm wondering why you don't see electrical outlets on planes? Do any airlines have sockets in the cabin? How about in first class? <Q> Several of the answers here seem to suggest that this only happens in first or business class. <S> While that was historically true, it's not so true anymore. <S> Airlines such as Cathay Pacific and Korean Air , for instance, have them at every seat in most (or all?) <S> of their long-haul aircraft. <S> Delta also has it in parts of economy on several of their long-haul configurations as well as in all of economy on their recently-acquired 717s and 737-900ERs . <S> As Lnafziger said, some airlines' systems require adapters, while others don't. <S> At least from personal experience, it seems that most of the recent ones do not. <S> On Korean Air, Cathay, and Delta, the plugs are designed to be able to fit any of the standard power plug types (e.g. North American, European, Asian, etc.) <S> Since most new electronic devices use auto-switching power supplies, they should accept the 110V/60Hz supplied by most of these systems, even if they're designed for 220V/50Hz markets. <S> Here's a picture of one of the outlets in economy on the Delta 717s. <S> Notice that the holes are cut such that any of the standard plug types will fit in it. <S> The slot on the bottom is a USB power port. <A> This depends on the airline, but to answer your question: <S> It seems that since the FAA relaxed the rules on portable devices that the airlines are seeing the need to add them to more of their fleet. <S> For example: US Airways has a Business Tools webpage which tells which of their aircraft have outlets. <S> There are some in both coach and first class. <S> United has an Inflight connectivity and power webpage <S> whichs shows that a lot of their fleet has electrical outlets and more are coming. <S> There are different types of outlets, and some of them require an adapter to use while others don't. <A> Some EMB-145 models have a 120v AC outlet mounted in the cabin just below the cockpit door. <S> This was powered by an inverter (EMB-145 is 100% DC busses). <S> It wasn't for passenger use (primarily for cleaning crews) <S> and I didn't trust the power coming out of it enough to plug in a laptop, though we sometimes did charge our phones with it. <S> Some larger airplanes have 120v AC in the cabin mounted at a subset of seats. <S> I can't recall which airlines, but I have been in a 757 and a corporate CRJ-700 that had this kind of power installed. <A> To answer your question of "why don't you see them," I think it comes down to power requirements. <S> As mentioned, new-ish first/business class generally will have outlets available. <S> You can explore different aircraft here . <S> The reason it's not available in every seat is capacity. <S> If you have 150 people pulling 75W, that's 11.25 kW. <S> On a 737 NG, each of the two generators is rated at 90KVA. <S> However, they need most of that power to run the radio equipment, avionics, lights, galleys, window heat, entertainment system, and everything else on the plane that runs on electrical power. <S> So besides a possible upgrade of the generators/power system, this also adds the weight of running cables and having outlets at every seat. <S> It's a lot easier to do that sort of thing on a train car, where it doesn't have to fly and can get power from the locomotive. <S> You can find more about the 737 electric system here . <A> They are universally available since maybe 10 to 15 years, but only in Business and First, and normally would accept both US and European plugs. <S> I have seen one instance a few years ago on an older 747 where they had a proprietary socket and would hand out adapters for the different laptops. <S> Naturally, the adapter kit was of the same age and unusable on some modern laptops. <A> Power Sockets are getting pretty common these days. <S> Most of the Widebodies (specially 777 and 380's have power outlets for 2 out of 3 Seats in each row). <S> The Power Ratings also are 110V 60Hz commonly.	Yes, some airlines do have electrical outlets in the cabin. You can check with your specific airline or with sites like Seat Guru before booking to determine what is available on any given aircraft and at which seats. In Economy you are out of luck, but if you consider that most airlines have reduced Economy seating pitch to the minimum 31", laptop use is near impossible there, anyway.
What are the advantages/disadvantages of diesel/Jet A-1 piston engine? Some GA aircraft, notably the DA40/DA42, are equipped with piston engines that use Jet A-1 and/or automotive-grade diesel instead of aviation gas (avgas). An example of such engine is the Austro Engine AE300 : What are the advantages/disadvantages of these engines and why are they not more common? <Q> Advantages Compression-ignition engines have higher compression ratio which leads to being more efficient. <S> So the aircraft range improves and on longer flights payload capacity may improve as well. <S> Fuel consumption is usually about 30% lower. <S> The higher efficiency combined with the fact that Jet A-1 fuel is cheaper mean they have lower operating cost. <S> Especially since in Europe the leaded avgas is heavily taxed to discourage it's use for environmental concerns. <S> They should be a bit more reliable. <S> A diesel engine needs high pressure fuel pump, but apparently there are less problems with those than there are with spark-plugs. <S> They are somewhat easier to operate, since they don't have separate throttle and mixture controls. <S> They don't suffer the problems associated with incorrect settings of those controls, namely knocking/detonation and pre-ignition. <S> Turbo-charging them does not carry the risk of pre-ignition and most of them are turbo-charged, so <S> the performance does not decline as fast with density altitude. <S> There is lower risk of fire since jet/diesel fuel is less flammable (has higher ignition temperature). <S> Jet A-1 has much wider availability, especially in the third world, so it's easier to plan for fuel stops on a flight through say, Latin America or Africa Disadvantages <S> They are heavier for the same power, because they need to be made from stronger material due to the higher compression ratio and because they need to have larger cylinder volume because of lower maximal rpm. <S> On longer flights the reduction in fuel weight often makes up for the heavier engine. <S> Turbo-charging comes with specific operating procedures unfamiliar to those used to normally aspirated engines and a slight lag in thrust lever <S> (it's not a throttle) response. <S> As others mentioned, small airports may not have jet fuel yet. <S> This is probably better in Europe where the pressure to phase out 100LL avgas is stronger. <S> Some engines also use automobile diesel fuel or even either jet or diesel fuel as diesel engines are less picky about what they burn. <A> Advantage: AvGas is heavily taxed in Europe. <S> This is primarily an envy tax, because it brings in less than the cost of its administration, but the non-flying majority feels good by "punishing the millionaires who waste their money on flying". <S> AvGas costs currently about 2.6 - 3 € per liter in Germany, for example. <S> Jet fuel cannot be taxed in the same way because arbitrage is too easy. <S> Airlines would simply stop refueling within Europe. <S> At prices of around 1 € at large airports the difference is substantial. <S> With a DA-40 you might not get the same price that airlines get, but a sizable difference remains. <S> Disadvantage: At pure GA airports, you will have a hard time to get Jet fuel at all. <S> There are very few piston engines which can use Jet A-1 and are rated for aviation. <S> Car engines cannot be used without heavy modifications, because they are not designed for continuous operation at 60% or 70% of their maximum performance. <S> Due to the higher internal pressure, the engines tend to be heavier and produce more vibrations. <S> However, since the specific fuel consumption of a Diesel engine is lower, the total system mass for ranges in excess of 1000 km should be lower. <S> We have to use what was created half a century ago. <S> It's a shame, but it has been shown several times in the last two decades - there were a number of attempts to create GA diesel engines, with very little to show. <S> In the 1930's Junkers made a range of very interesting Diesel piston engines (see here ) which powered a range of aircraft designed for very long ranges. <S> They were used for transatlantic mail service (see here and here for examples). <A> Modern aero-diesel engines are far more technically advanced than the majority of avgas powered engines as they are very new designs. <S> Most avgas engines are normally aspirated, most of the time carbureted, and have manually controlled fuel to air mixtures, which is ancient engine technology. <S> Prop pitch is also usually computer-controlled, giving the pilot a single-lever control. <S> So there are no real disadvantages to the engines themselves, the disadvantages are more around the logistics and start-up costs. <S> There are few mechanics who can work on them, and few aircraft with STCs which allow them to be retrofitted, so if you want one chances are you can't have one. <S> To retrofit (if permitted) requires substantial modifications to fuel tanks, fuel delivery systems, electrical systems, and more, so it's not a cheap option.	Aero-diesels have turbochargers, electronic fuel-injection, and computer-controlled mixture which gives them better performance and efficiency. The GA market is simply too small to support the design of new engines.
What are the reasons for using an instrument approach on a clear day / CAVOK? As a new VFR pilot, I was wondering why anyone would fly (or be assigned) an ILS (or other) approach in clear weather? I ask this because I watched Vienna - Tokyo (Narita) on PilotsEye.tv where the F.O. flew the approach looking at the display all the way until the flare. The visibility was good. Runway 34R. <Q> There are actually quite a few reasons to fly an instrument approach, especially one with vertical guidance (like an ILS), even if the weather doesn't require it: It serves as a backup to the visual approach. <S> It helps to ensure that you land on the correct runway, and even at the correct airport. <S> (Unlike this airplane .) <S> ATC uses it when pilots do not have the airport or runway in sight. <S> This happens quite frequently at large airports where they have to line many aircraft up on final. <S> The last guy is a long distance from the airport so may not be able to see it but can fly the approach. <S> It can be useful if it is hazy or the sun is making it hard for the pilots to find the airport. <S> Some parallel runways are approved for simultaneous approaches (as is the case at Narita for runways 34L & 34R) <S> so ATC will clear two airplanes for the respective ILS's. <S> This keeps them tracking the centerline of the approach instead of maneuvering visually where they might drift over into the way of the other airplane. <S> Flying the approach on the autopilot leaves more time for the pilot to focus on other things and possibly catch something that might have been missed while hand flying a visual approach. <S> If I had to guess about the particular approach that you mention, I would say that it is probably company SOP (Standard Operating Procedures) to fly the ILS whenever possible for the safety benefits, and that Narita allows simultaneous parallel landings to the two runways <S> so ATC would require it as well. <A> There are three reasons I can think of: Noise abatement <S> I know that it is not allowed to fly visual approaches at many european airports due to noise abatement. <S> They prohibit it to avoid aircraft flying over residential areas left and right of the approach path <S> Traffic flow <S> At many international airports (e.g. Tokyo) they have to use every second to manage the huge amount of traffic. <S> Lining up the aircraft on an ILS with an assigned speed is the most efficient way. <S> Practice / Safety <S> There are many airlines which tell their pilots not to do visual approaches. <S> This should enhance safety (stabilized approaches) and keep the pilots well prepared for low visibility operations. <S> Sometimes you even practice autoland in VMC to keep current. <A> In addition to serving as a good cross-check for the visual procedure (which is probably the case here - one pilot looks down, one pilot looks out) <S> there's at least one other reason I can think of for a pilot to request & fly an instrument approach: <S> In order to maintain currency to act as pilot in command under instrument flight rules a pilot must log a certain number of instrument approaches within a given calendar period (in the USA <S> it's 6 approaches in the last 6 months, plus "holding patterns; and Intercepting and tracking courses through the use of navigation systems.", except for gliders which have a different requirement). <A> $0.02 to add to all that. <S> The question can be extended a little and one could ask 'why fly ifr on beautiful clear day'. <S> Added safety. <S> For a new instrument pilot it would still be a good practice to operate in the ifr system even if you can't log the flight for currency purposes.	There are various visual illusions that can cause a pilot to fly an approach too high or too low and monitoring the vertical guidance can help to mitigate those. Sometimes instrument approaches are used for noise abatement reasons. All other things being equal, if your currency is about to lapse you might request to fly an instrument approach (including one turn in a holding pattern) on a VMC day (with a view limiting hood and a safety pilot on board) to maintain currency on.
Have there been any cases of collision/airprox of small drones with manned aircraft? Small civilian mini-drones such as the DJI Phantom or professional surveying drones are becoming increasingly widespread, raising concerns about the potential collision/airprox with manned aircraft (especially GA where flight altitude is typically relatively low). Have there been actual cases of collision and/or dangerous airprox reported so far? What were the consequences? <Q> CASA (Australia's aviation authorities) has a report on an airprox between a crop duster and a surveying mini-drone: <S> ATSB incident report <A> There are two instances I remember hearing about. <S> This one happened to a plane landing at JFK, and the FBI was seeking information about it. <S> They reported seeing a small black "drone aircraft" with four propellers. <S> I don't think they every found anything more. <S> And just recently , two planes landing at YVR saw an RC helicopter, one plane coming very close to it. <S> The RCMP was investigating, but again it's not certain whether they will come up with anything about it. <S> There is also an investigation into a video taken from a quadrotor showing a plane landing at YVR. <S> And if you thought that was close, check out this video from Australia. <A> It september 2017, a DJI Phantom collided with an US Black Hawk helicopter causing a real damage to main rotor. <S> Obviously a military helicopter cannot be destroied by a small uav (why develop expensive Sparrow or Maverick rockets when a simple Phantom could land a military object ;-) ) <S> but... surely it would be a true danger... <A> This one in Tallahassee with a regional jet got a lot of attention when it happened but there are many more. <S> The FAA keeps a database, and I expect we'll see about an actual collision with a Part 121 aircraft soon enough as the number of airborne UAVs is increasing rapidly. <A> February 2018 - <S> What is thought to be the first drone collision in the US occurred in February 2018.	The National Transportation Safety Board is investigating a helicopter crash landing in South Carolina that may have been caused by a civilian drone, according to a report from Bloomberg .
What is the advantage of combining the rudder and brake pedals in aircraft? I've read about several aircraft having their rudder and brake pedals very close together. To me this seems confusing and prone to error. It looks easy to mistake the rudder / brake pedals and inadvertently press the wrong one when flying or taxiing the aircraft. Since these are fundamentally important controls, this could lead to disaster. So what is the advantage of keeping the rudder / brake pedals in this configuration? Are there any historical reasons for this design choice? <Q> All of the aircraft that I have ever seen have the rudder and braking functions combined into one set of two pedals. <S> To operate the rudder you press on the bottom part of the pedals, so that they slide back and forth on tracks, and to operate the brakes, you press the top part of the pedals so that they rotate towards the floor. <S> The left pedal operates the left wheel brake, and the right pedal operates the right brake, so you can use differential braking to turn the plane. <S> For rudder operation, the motion of the two pedals is locked together (i.e. press on the right pedal for right rudder, and the left pedal moves aft while the right pedal moves forward). <S> Because of the two different motions (rotation for brakes versus sliding for rudder) there isn't a problem with hitting the brakes when you want rudder or vice versa. <S> Typical early training is to operate the rudder using your toes on the lower parts of the pedals, so and to only put your whole foot on the pedal to actuate the braking mechanism. <A> Here are a few design constraints: Unlike a car, there is sometimes the need to apply the left brake independently from the right brake. <S> (See What is differential braking? <S> for more details and pictures.) <S> There is a need to control the rudder, and you need to be able to move it either direction. <S> The pilot needs to be able to make small and rapid adjustments to them both, in both directions. <S> The pilot needs to be able to use both while at the same time controlling pitch and bank. <S> Based on this, it's pretty easy to see that a push button, lever, or toggle switch somewhere wouldn't meet all of these requirements, especially if you need to use your hands (which are already occupied with the yoke) to do it. <S> There are three axis of motion on an aircraft that the pilot can control directly, and with current designs, the flight controls move the aircraft in the same direction that they are moved: <S> Bank is controlled by turning the yoke left and right, which lowers the wing in the direction that you turn it. <S> Pitch is controlled by pushing the yoke forward or pulling it back, making the nose raise or drop. <S> Yaw is controlled by pushing the pedals in the direction that you want the nose to pivot. <S> Since your feet are already on the rudder pedals and you need two brake pedals too (point one from above), they usually just put the brakes on the top of the rudder pedals so that they can be used at the same time. <S> 1 <S> 1 <S> There are also hand brakes in some older aircraft that require you to use your hand. <S> This has been pretty much abandoned in favor of toe (or heel) brakes since it did not allow for differential braking. <A> It is by design. <S> An airplane have three axes to move, unlike a car, thus more controls should be provided to the pilot. <S> As primates have two legs and two arms, the designers of airplanes put foot pedals to control the rudders. <S> Because Newton came up with the first law of motion before airplanes were built, we needed to have devise a way to stop airplanes, and hence brakes were invented. <S> But unlike cars, where a foot or feet are used to apply the brakes, rudder pedals were already occupying that region. <S> And hence airplane designers added brakes on top of the rudder pedals. <S> Like everything else, this also evolved overtime. <S> The rudder's direction in aircraft since the "Golden Age" of flight between the two World Wars into the 21st century has been manipulated with the movement of a pair of foot pedals by the pilot, while during the pre-1919 era rudder control was most often operated with by a center-pivoted, solid "rudder bar" which usually had pedal and/or stirrup-like hardware on its ends to allow the pilot's feet to stay close to the ends of the bar's rear surface. <S> I disagree with the statement that combining them leads to any confusion. <S> The mistakes you make as a student are minimal and do not happen after a little training anyway. <S> Another reason for having rudder pedals on the floor is that in a coordinated turn, you might have to add slight rudder along with banking the airplane. <S> As hands are used to bank, rudder pedals are controlled by feet. <S> This situation is only applicable during flight. <S> During flight , brakes do not have any effect as they are applied on the main landing gear. <S> During taxiing , when you press the rudder pedal (not applying brakes), on smaller airplanes, the nose wheel is turned. <A> One other factor... <S> this results in a more natural usage of the control. <S> Since a lot of aircraft steer on the ground by differential braking, the pilot will use the same control and same basic thought process for yaw on the ground that they use in the air. <S> In the air, left rudder to yaw left. <S> On the ground, press on the top of the left rudder pedal to turn left. <S> This is one less detail that a pilot has to keep in their mind. <S> They have plenty of details already, so any reduction in pilot mind load is a big bonus. <S> Early aircraft, especially early airliners like the Ford Trimotor and DC2, used a braking bar to accomplish the differential braking (called the 'Johnson bar'... <S> it was about .75 meters in length, so some wishful thinking was probably involved) <S> that required a fair amount of skill to master, as well as a fair amount of arm strength. <S> Hydraulic brakes on the rudder pedals were a huge improvement.	The rudder pedal/brake assembly is very easy to understand and master. The pilot needs to be able to use both at the same time.
Don't all airspeeds change with weight? Ok, so I'm a student pilot, and I'm going over the Vx, Vy, Vne, ... etc., and I see that "maneuvering speed" (the speed at which you can safely apply full flight controls) "changes with weight". Which airspeeds don't change with weight? I can pretty much guarantee the the takeoff speed changes with weight, as would flap operating speeds, never exceed speed, and cautionary zone, because that is just the basic application of physics (inertia). Why do we treat maneuvering speed as the only variable airspeed? <Q> There's a distinction, though, between "speeds at which something special happens aerodynamically" and "regulatory limiting speeds that prevent you from doing something bad." <S> For example, V NE is a regulatory value; it is prohibited to exceed this speed at any weight. <S> This value includes a safety margin and is determined from flight test data. <S> Nothing special happens aerodynamically at the published V NE speed. <S> (Thank goodness!) <S> The special stuff, like aeroelastic flutter or structural failure, happens at some speed well above V NE , regardless of your weight (as long as it's within the allowable CG envelope of course). <S> Another example, V FE , is similar. <S> Nothing special happens at this speed. <S> It's just a safety value: as long as you're below this speed, you won't tear the flaps off the plane if you extend them, regardless of your weight. <S> Almost all speeds that aren't "regulatory limits" do indeed change with weight. <S> Some examples: V A design maneuvering speed <S> V X best angle of climb speed V Y best rate of climb speed V R rotation speed V S0 landing configuration stall speed V S1 "specific" configuration stall speed <S> For larger multi-engine airplanes that you'll encounter later in your flying career: <S> V 1 engine failure recognition speed (or takeoff decision speed) <S> V 2 takeoff safety speed <S> V MC minimum control speed <S> (Note that a lot more factors besides just weight can go into these latter speeds, such as atmospheric conditions and reduced-thrust takeoffs .) <S> For small airplanes, it is common to publish these speeds as single values, measured at gross weight. <S> For many of them there are also graphs in the performance section that show you how the actual speed varies with weight. <S> For larger aircraft, the performance graphs (or calculations) are always used. <S> For example, you won't use a single "stall speed" value from a handy table in the "POH" of a 747. <S> In these types of aircraft, key numbers are calculated as needed on each flight for current weight. <A> To explain why these speeds change with weight: V A design maneuvering speed: this is because it takes a lot more force to move a heavy plane than it does a lighter plane. <S> On a lighter plane, the surfaces deflect, apply a force, and the plane moves. <S> Once the plane is moving, the surfaces move too, which lessens the force on them. <S> A heavier plane will move less, which means the surfaces are applying more force and for longer to move the plane the same amount. <S> V X best angle of climb speed V Y best rate of climb speed: A heavier plane will need to produce more lift, and therefore have more drag, which affects climb performance. <S> V R rotation speed V S0 landing configuration stall speed V S1 <S> "specific" configuration stall speed: A heavier plane needs more airspeed to produce enough lift to take off or not stall. <S> Here is why: <S> Among other things, lift is dependent on speed and angle of attack. <S> So at a given speed, angle of attack can increase to generate more lift. <S> The plane will have a maximum angle of attack above which it will stall. <S> Since these are minimum speeds, they are at the maximum angle of attack, so speed must increase to provide the lift. <A> Well, top of my head: V tyre and M MO are two speeds which are totally independent of aircraft mass. <S> The first is simply a tyre speed limitation and the second is aerodynamically determined by the wing. <S> The rest should all change one way or another with mass. <S> Why then use single values for most of these speeds? <S> Well, for one thing, in smaller aircraft, those changes will ammount to 1,2 maybe 5 knots from Basic Empty Mass to <S> Maximum Take Off Mass , <S> so memorizing your stall speed as variable between 39 to 41.2 knots (when you have about +/- <S> 5 kts accuracy on the airspeed indicator anyway) is pointless. <S> Round it up to 45 and stay above that. <S> Remember that most of these "fixed" speeds are CAS while some are EAS (and remember how that influences things), then remember those speeds will change from flight to flight depending on weight, but not too much. <S> As you get into slightly bigger airplanes you will start seeing the AFM giving 2 or 3 sets of speeds for different weights (850 kg, 1000kg, 1150kg) and it is your job to know them and interpolate them for today's weight.	Your instinct is correct; almost all of the key airspeeds — those at which something special happens aerodynamically — vary with weight.
Is there a practical way to demonstrate sustained flight on the back side of the lift curve without an AoA meter? Here is a $C_L$ / $AoA$ curve that I took from Wikipedia . The better textbooks say that a stall is that condition in which a further increase in angle of attack will result in a reduction of lift . The point at which that transition happens is known as the critical angle of attack. Theoretically, sustained flight is possible at angles beyond the critical angle of attack - take a look at the chart. If the airplane can sustain level flight at point $A$, it can sustain level flight at point $B$. Is there a practical way that I can demonstrate sustained flight on the backside of the lift curve without an angle of attack indicator? Or to ask the question another way, Is there a practical way to tell when an airplane has exceeded the critical angle of attack without an AoA meter? <Q> Flight on the backside of the stallcurve is unstable; any (infinite small) increase in AoA will result in less lift. <S> Less lift will cause the flightpath angle to decrease and the AoA to go up even more. <S> To increase the lift, the nose has to be pitched down, but not so much that the stall is recovered <S> otherwise you wouldn't call it sustained flight at the back of the AoA curve. <S> At the same time you are also on the backside of the powercurve. <S> This means that any reduction in airspeed would cause the drag to increase therefore decelerating the aircraft furthermore. <S> This double unstable situation would require a lot of fast responses from the pilot, probably causing too high workload. <A> Increase the aircraft's pitch in level flight. <S> If you climb, you are on the good side of the curve. <S> If you sink, you are on the bad side. <S> This will only be the initial response of the aircraft, as the airspeed will start to change and further affect the aircraft's behavior. <S> Without an AOA meter, you would have to look at your artificial horizon and vertical speed. <A> Gliders make sustained flight on the backside of the lift curve all the time while thermalling at 40-50 knots and 50 degrees of bank. <S> You spend a lot of time adjusting the elevator to keep the plane from stalling, a lot of time adjusting the ailerons to keep the bank angle, and a lot of time trying to stay coordinated (or in a slight slip) with your feet. <S> The bigger the wingspan, the more work it is. <S> The big difference in a glider is that you're usually going up, not down when this happens :) <A> Is there a practical way that I can demonstrate sustained flight on the backside of the lift curve without an angle of attack indicator? <S> Set up the aircraft for stalls, do all the stall safety checks. <S> Fly slowly, so that you're near the peak of that curve. <S> Pitch up sharply and confidently while adding power. <S> When you've done the right amount of both, you'll find that the aircraft remains more or less in level flight. <S> Make adjustments to zero the vertical speed, remembering that if you're climbing, you want more up pitch to stop it in this configuration, and vice versa. <S> P.S. <S> I'm no instructor and my flying hours are limited, but I was taught to do this during my initial training. <S> I suppose how easy this is depends strongly on the aircraft. <A> The drag at point B in your chart is much higher than at point A, so you might not be able to trim level flight there. <S> If you are willing to sacrifice altitude to compensate for missing thrust, the lift at point B will be sufficient to trim a quasi-steady flight condition. <S> Flying beyond stall requires sufficient pitch authority, so you might not be able to trim this condition with forward c.g. <S> That said, your pitch response will be much weaker than in normal flight, and you can pull suddenly without much happening. <S> Depending on your c.g. location, you will need to have your yoke/stick/ <S> whatever pulled way back to trim this condition, and if some more travel in pull direction remains, it will not help to further increase your angle of attack. <S> Some aircraft will not let you stay in this condition and either drop the nose by themselves (which is good) or drop a wing (which is really bad), so try to experiment with enough altitude for recovery. <S> My answer is Yes, if the aircraft lets you. <S> Just watch the sink speed. <S> Lift coefficient over 180° for several NACA airfoils, taken from Sighard Hoerner's Fluid Dynamic Lift . <S> @DeltaLima is absolutely correct: While the lift curve slope is negative (the region around point B in your plot), the aircraft will be unstable and will drop out of this alpha range quickly. <S> Note, however, that in the post stall region another section with positive lift curve slope follows, and here you can fly (well, let's better say mush) stably if the pitch control power of your aircraft allows. <S> You will detect that you are in this region when your sink speed is much higher than at around stall, but the aircraft is in a stable state. <S> Air France demonstrated that you can keep an A330 in this condition for three minutes without any trouble. <S> The trouble only starts when your altitude has run out.	I doubt if it is practically possible to fly on the backside of the liftcurve without special automation.
Why is one of two parallel runways sometimes closed in foggy weather? A few times, when flying into SFO, me and my fellow passengers were informed that due to foggy weather one of two parallel runways there is closed, causing delays. So, a few questions: Why can only one runway be used during fog? During an instrument landing, if the instruments are precise enough to land the plane exactly in the middle of one runway, then surely they are precise enough to differentiate between two runways? Is this standard practice in all airports or something specific to SFO? Is there some minimum distance between parallel runways above which it is safe to keep them both open in foggy weather? <Q> SFO makes use of simultaneous close parallel approach operations. <S> This allows higher density operations than would otherwise be possible for runways spaced so close, but to make use of these ops, in SFOs case, requires 1600 ft ceilings and 4 sm visibility due to the requirement that aircraft maintain visual contact during close parallel operations. <S> It does look like SFO can run the ILS <S> approaches simultaneously outside of close parallel operations, but is possible <S> the required spacing makes its pointless to use both runways. <S> If weather was bad enough that cat II ops were in effect, I don't see any verbiage on the cat II charts indicating simultaneous ops are approved. <S> Regardless of how precise your instruments are, there are strict requirements on how close you can be to another airplane in the approach phase and that separation be maintained if both parallel aircraft perform the missed approach. <S> The ability to run parallel approaches in low visibility depends on how far apart the runways are laterally. <S> Airports like IAH and ATL can run triple parallel ops and if you take a look at their runway layout you will find they are spaced quite far apart and may be displaced relative to one another. <A> While ILS is precise enough to guide the aircraft precisely onto the runway, it is only so precise in the immediate vicinity of the runway . <S> The instrument measures <S> angular divergence from the runway axis. <S> So while the one dot offset is just a few metres over threshold, it is much more at the point where the aircraft normally intercept the localizer, which is usually at least 10 miles out for large aircraft. <S> At KSFO the runways are so close to each other that while the localizer could perhaps ensure separation in the final phase of landing, it can't ensure it in the earlier part. <A> I didn't see specific distances mentioned for the second part of the question. <S> If the runways are ate least 2500 feet apart, they can conduct staggered approaches (both runways in use, but aircraft do not approach alongside each other). <S> As a reference, the SFO runways have a centerline separation of 750 feet. <S> From the AIM <S> http://tfmlearning.faa.gov/Publications/atpubs/AIM/Chap5/aim0504.html#?F8258ROBE <S> It also shows the situation that waivers are possible for separations less than 4300 feet if additional conditions are met. <A> It's not. <S> Precise enough, that is. <S> There's a point in the ILS landing process called "Minimums". <S> At that point the pilots must see the runway or throttle up and go-around. <S> Assuming they have seen the runway, they must be prepared to stick-fly it onto the centerline, and then keep it on the centerline during braking, against crosswinds (still pushing on the tail) <S> , asymmetry in braking or reverse thrust, etc. <S> The precision of this varies by different classifications of wayside and on-airplane equipment, so both minimums and the "when you take over and stick fly" points also vary (separately). <S> You can't decree that every landing airplane has the latest & greatest. <S> In fair weather, SFO ops (when my cubicle was directly under the flight path) involved bringing in airplanes near abreast, virtually wingtip to wingtip. <S> That's not the computer either . <S> That is the slightly trailing plane stick-flying it, using the Mark 1 eyeball for separation. <S> And that depends on both fair weather and a high cloud ceiling, so they can visually line up (with each other) early in the approach. <S> The abreast (not staggered) approach was required for capacity reasons, not for landing but for takeoff: <S> these two aircraft needed to land simultaneously and clear the runway intersections simultaneously. <S> There were two departing aircraft lined up on the two cross runways to start their takeoff roll the moment this pair swished by. <S> I've even seen a triple: a Japan Air Lines 747 and two F-16s. <S> Guess which day it was.	If the runways (centerline to centerline) are separated by at least 4300 feet (and other conditions are met), the airport can conduct simultaneous instrument approaches.
How is the pressure difference in passenger plane toilets generated? The toilets on passenger planes flush with an impressive amount of force - Is the negative pressure inside the tanks generated by a pump or are the tanks connected to the outside air pressure? Considering that the toilets should also work on the ground, I presume pumps are used - on the other hand, maybe the low pressure is stored inside the tanks from the last flight? Also, pumps would mean the toilets don't work when the aircraft is not powered up - is this true? Also, how was the engineering problem solved of keeping the pumps or the tubes connecting to the outside free from waste? <Q> How is the pressure difference in passenger plane toilets generated? <S> The pressure in flight is generated by using the vacuum outside. <S> This dosen't work on the ground or at low altitude, so there's a pump as well to draw out the air to create an artificial vacuum. <S> Considering that the toilets should also work on the ground, I presume pumps are used - on the other hand, maybe the low pressure is stored inside the tanks from the last flight? <S> Also, pumps would mean the toilets don't work when the aircraft is not powered up - is this true? <S> Not sure about this one, but since the aircraft is seldom not powered when a person is onboard (maintenance can't do much without power either) <S> , I can't think of this being a significant problem. <S> There might be a little bit of leftover pressure. <S> Airbus states that the vacuum pump is powered off the AC power bus, so it may be powered from the ground or the APU when the engines aren't on. <S> Also, how was the engineering problem solved of keeping the pumps or the tubes connecting to the outside free from waste? <S> As is seen in the picture below, the tank is rinsed out through with the help of a second port on the access cover to clean it out. <S> The rest of the system I believe is designed to last until the next maintenance, when (I think) it's connected up to a high pressure hose to thoroughly clean it out. <S> A320 Toliet System: <S> A320 System Details. <A> In this video is shown a test of the A380 system. <S> At about the 0:48 mark the presenter remarks that The toilets work by pumping air out of waste-tanks in the rear of the plane <S> So, at least in the A380 case, yes the negative pressure is achieved via pumps. <S> As for your last question <S> how was the engineering problem solved of keeping the pumps or the tubes connecting to the outside free from waste? <S> If you look at the video, you see that the pipes are connected on the top of the tank and the gravity will keep the waste away from the pump (in the assumption that no acrobatic maneuver will be performed, usually valid, but not always ) <A> The whole system is under low pressure. <S> Here is a video explaining how the A380 toilet system works.	There is a vacuum-pump that draws the air out of the waste tanks.
What is the effect of changing the autobrake setting after touchdown? If an autobrake setting is chosen prior to touchdown, but after touchdown and nosewheel compression (i.e. after the autobrake has engaged) a different setting is required, is it safe to change the setting during the roll-out? What happens when the setting is changed in this manner? I know application of manual brakes disables the autobrake. Does the autobrake immediately match the new deceleration requested? <Q> This answer was difficult to find as both Flight Operation Manuals and Maintenance Manuals did not say. <S> The only guidance was found in the system description provided by the OEM of the BCSU. <S> I am not mentioning the fleet type because at some point the detailed description might become proprietary. <S> According to the description I found for a given automatic braking system is that it is armed when the pilot presses one of the three pushbutton switches which set the auto-brake level. <S> The system will only arm if gear up is not commanded, there is hydraulic pressure as needed, and no existing faults exist that prohibit normal braking, as well as a few other computers available on the associated data bus. <S> Or more precisely from the black-box point of view <S> automatic braking is engaged whenever two spoiler signals in three appear once automatic braking has been armed. <S> In other words, once armed, the automatic braking will only engage if spoilers are sending the signal that they are being activated, or are activated. <S> It specifically says that the pilot can select another pushbutton switch even afterarming. <S> The BSCU acknowledges this new command and executesthe corresponding task. <S> Automatic braking is released whenever the braking sequenceis interrupted: when an arming condition disappears, when an engaging condition disappears, when one or both brake pedals are held down beyond thedefined threshold, when the selected pushbutton is pressed again. <S> The question, therefore is 'After you have already armed at a given setting and the system is actually engaged, because the spoiler actuation has initiated auto-braking, what happens when you press another setting?' <S> As long as the arming conditions still exist, which in most cases would, and as long as the engage conditions exist, as would be the case if the spoilers are activated (at least 2 of three spoiler signals being sent to the BSCU), then yes, you may change the setting after touchdown and the BSCU acknowledges this new command and executes the corresponding task. <A> This will be quoted from the B737 NG - Systems Summary [Landing Gear] which isn't an official Boeing document, but ... <S> Page 5 <S> Landing <S> When a landing autobrake selection is made, the system performs a turn-on-self-test. <S> If the turn-on-self-test is not successful, the AUTO BRAKE DISARM light illuminates and the autobrake system does not arm. <S> Four levels of deceleration can be selected for landing. <S> However, on dry runways, the maximum autobrake deceleration rate in the landing mode is less than that produced by full pedal braking. <S> After landing, the autobrake application begins when: - both forward thrust levers are retarded to IDLE - the main wheels spin-up NOTE : <S> Landing autobrake settings may be selected after touchdown prior to decelerating through 60 kts of ground speed. <S> Braking initiates immediately if the above conditions are met. <S> To maintain the selected landing deceleration rate, autobrake pressure is reduced as other controls, such as thrust reversers and spoilers (without disarming the system) by rotating the selector. <S> The autobrake system brings the airplane to a complete stop unless the braking is terminated by the pilot. <S> So, reading between the lines here, if the autobrake system has not been activated, upon touchdown it can be activated, before slow down to 60kts ground speed, as long as all other stipulations are met. <S> Also, although the sentence as written, is confusing, the last paragraph indicates that the level of braking can be changed during autobraking, by turning the selector AND that will not disarm the system. <S> I know this is not official documentation and is an older model plane, but thought I'd offer it up. <A> I have flown the 737NG and now fly 757-200. <S> It is now quite normal for us to set a certain AB setting (e.g. level 3), to match a desired runway turn off. <S> Then once landing distance is assured, at maybe 60-100kt, reduce the setting to 2, then 1, then off (or disarm on 757). <S> Alternatively you can cancel AB by using manual braking pressure (normal method on 737) or by moving the speed brake lever slightly forward, then back to fully deployed once AB have clicked out (normal method on 757). <S> All methods work on both aircraft, and the choice of method is more about the best way of avoiding the slight jolt <S> felt as the ABs disengage - it's all about passenger (or pilot!) <S> comfort - <S> oh yes, and also about stopping by the end of the runway! <A> Yes the autobrakes can be increased after landing using the selector switch but it depends on pilot preference and certain conditions.	There is nothing that says the system can't be armed after touchdown, however the system will only engage when the spoilers are being activated, or are activated.
What is the fastest airplane? There are many airplanes that claim to be the fastest piston, private jet, airliner, but what is the all time fastest airplane? How fast does it travel? <Q> This is a broad question. <S> The Wikipedia page on vehicle speed records gives a nice breakdown by various categories. <S> Some criteria are manned vs. unmanned, air-breathing vs. rocket, civilian vs. military. <S> The fastest manned, air-breathing aircraft was the Lockheed <S> SR-71 Blackbird with an (unclassified) record of 2,193.2 mph on July 28, 1976 . <S> However, some would consider the rocket-powered North American X-15 <S> the fastest manned aircraft at 4,510 mph. <S> If you consider the Space Shuttle an "aircraft" during its re-entry phase, it passed Entry Interface at around 17,500 mph. <S> This was unpowered flight though, and its speed dropped off as it entered the atmosphere. <S> I believe the rocket-boosted <S> HTV-2 Falcon <S> currently qualifies as the fastest unmanned aircraft at 13,201 mph. <S> The record for the fastest human-made craft of any kind is currently held by the Helios probes , at 157,078 mph. <S> The fastest manned human-made craft was the Apollo 10 spacecraft at 24,790 mph. <S> (Note that Apollo 10 holds the record not because it was any more or less capable than any other Apollo mission, but that its chosen moon fly-by trajectory resulted in a higher top speed relative to Earth. <S> It could also have achieved a much higher top speed on a different trajectory had that been a goal for mission planners, but it wasn't.) <S> Finally, every single one of these is either military or NASA (not civilian). <S> The fastest civilian, air-breathing aircraft were the Tupolev Tu-144 supersonic transport at 1,518 mph, and its Western counterpart, the legendary Aérospatiale-BAC Concorde , at 1,488 mph. <S> Both are now retired. <S> Several private organizations are developing civilian suborbital and orbital rocket-powered spacecraft; I'm not sure which is currently fastest. <S> And though these aren't crafts or vehicles , honorable mentions go to a 150,000 mph steel plate launched by a nuclear weapon, and to particle accelerators for propelling subatomic particles and "man-made" particle collision byproducts at ridiculously close to (99.99something percent of) the speed of light :-) <A> At present (and since 1976) <S> Lockheed SR-71 Blackbird holds record for the fastest aircraft. <S> As mentioned here : <S> On 28 July 1976, SR-71 serial number 61-7962, broke the world record: an "absolute altitude record" of 85,069 feet (25,929 m). <S> The speed it traveled was 1,905.81 knots (2,193.2 mph; 3,529.6 km/h), approximately Mach 3.3. <S> A list of airspeed record is on Wikipedia . <A> The NASA X-43A got up to almost Mach 10 <S> , I think that's pretty close to a record for an air breathing atmospheric vehicle.	The SR-71 was the world's fastest and highest-flying operational manned aircraft throughout its career.
Why do slats deploy first? I know on the 737, the leading edge slats deploy at the first flap setting, and the trailing edge flaps deploy after that at higher flaps settings. Why do the slats deploy before the trailing edge flaps? LE Flap and slat schedule as it relates to TE Flap position for the 737-300: <Q> The outer wing carries the ailerons, so there are no flaps, but the flaps inboard will induce more lift on the whole wing, raising the effective angle of attack even in the aileron section. <S> Slats push the stall angle of attack up. <S> Without the protection provided by the slats, the outer wing could stall, and if this happens on one wing first (very likely, there are many reasons for flow asymmetry), the aircraft will roll violently. <S> To do so during an approach is not good at all. <S> Look at aircraft with powerful flaps: They all have slats at least on the outboard wing to avoid outer wing stall. <S> One goes with the other. <A> (source: x-plane.org ) <S> What you can see here is that as the slats deploy, the lift coefficient in theory for the same angle of attack remains relatively unaffected. <S> Only the angle of attack at which stall is reached is increased. <S> This may be sensible because it increases the safety margin before deploying flaps particularly as these will increase drag which if left with the same power setting <S> will increase the angle of attack to maintain the same vertical speed. <A> Been long time since I learned this, but if memory serves me the slats produce more lift for less drag (more "bang for your buck"), whereas flaps are the reverse. <S> On typical airliner (I'm a 767 captain at AAL) <S> slats reduce your stall speed an average of 30 knots.	The slats help to protect the outer wing from stalling when the flaps deploy.
Do you ever get to practice ejecting out of a plane as a fighter pilot? The military throws away a lot of equipment simply because it doesn't hold up to current standards. So I was wondering the following. As a fighter pilot, would you ever get a practice run ejecting out of a plane, or is it just kind of one of those things you read about and hope you never have to do it? What is it like ejecting out of a plane at 500 knots? 1000? <Q> Example video <S> Plenty of pilots have survived ejection (Wikipedia says "As of 20 June 2011 ... <S> the number of lives saved by Martin-Baker products was 7,402 from 93 air forces") <S> The types of injury are illustrated by this example <S> The ejection seat has been responsible for saving the lives of thousands of pilots around the world since its introduction in the late 1940s. <S> Typical survival rates quoted in the literature vary from 80–97%. <S> It is generally accepted that radiographic evidence of vertebral fracture can be found in 30%–70% of aircrew after ejection <S> The reason real ejection seats are not used is almost certainly the high risk of injury. <S> Ejecting clear from a high speed jet requires a lot of acceleration. <A> Ejecting at 1000 knots means ejection into supersonic flow. <S> Not even the Zvezda K-36 , the indisputably best ejection seat around, is rated for that. <S> For this kind of speed, whole enclosures have been designed which did not work all too well when they had to be used. <S> For training, there are simulators to prepare pilots for that hopefully rare occurrence (the picture above is from this link; there you'll find more pics and a list of their customers), but mostly, simulations are run with simulated pilots, too. <S> The spinal loads are too high to have pilots exposed to them regularly without the benefits which go with a successful ejection. <S> For the things that might happen, see what William Rankin went through on July 26, 1959. <S> It can last quite a while, too. <S> In his case 40 minutes. <S> By the way, ejection seats started to save pilot's lives in 1942 (Germany) and 1945 <S> (Sweden) . <A> I particularly like this site <S> What is it like ejecting out of a plane at 500 knots? <S> 1000? <S> Look for this story on the linked site... <S> A USAF F-15 crew ejected, at night, estimated well over mach 1. <S> The back seater was killed in the ejection; the pilot survived; wreaked havoc on his musculoskeletal system and required the lower part of one leg to be amputated but eventually returned to flying status. <S> As a fighter pilot, would you ever get a practice run ejecting out of a plane <S> My experience in a ejection trainer, much like the "air force training rig" above, gave a very short initial jolt equivalent to the real thing. <S> I had my head bent ever so slightly <S> and I had a sore neck for weeks. <S> There was never a repeat ride in our year long training. <S> Ejecting out of the real thing for training? <S> We would have called that sort of thing "practice bleeding". <A> There are ejection seat trainers, most concentrate of the required procedure before ejection and upon successful completion do a short 10 cm hitch upward, only a jolt to indicate end of procedure. <S> Some air forces do have trainers that give more of a ride. <S> I got a demo ride in the sim in the picture, since I was involved in supplying some of the hardware. <S> It was a severely toned down ride with much lower accelerations than pilots experience for real, but still too much for my blood pressure: one moment I was giving the all clear to the instructor, the next moment I was 3 metres in the air with an aching neck. <S> I have no recollection of what happened in between.	Air forces use special training rigs rather than real ejection seats.
Why tap the brakes on take-off in fixed gear aircraft? The Socata TB10 checklist indicates that you should touch the brakes after lift-off. I assume this is to stop the wheels from turning, but why? In a retractable gear aircraft this would make sense to avoid using anything in the wheel-well to stop the wheels and potentially causing damage or generate heat (as a side note, I think some airliners actually have brake-pads in the wheel wells for this purpose). However, the TB10 is not equipped with retractable gear. The TB10 and TB20 are very similar, and it might be a case of copy & paste between the two POHs (the TB10 POH also lists V-speeds for "flaps and landing gear retracted"). Do spinning wheels have an adverse effect on aerodynamics (or handling in general)? I would assume, if anything, they'd produce less drag. And as a cherry on top, I'd also assume they'd start spinning again fairly quickly, as only the lower part of the wheels are protruding out in to the air flow. <Q> This answer to another question has a link suggesting that the spinning wheels may be sufficiently large gyroscopes to affect handling of the aircraft. <S> That was however on a larger aircraft and higher speed (Lockheed Constellation). <S> I don't know whether that effect would be observable on TB10. <A> On a Cessna 172, spinning wheels do create vibrations. <S> Once the brakes are hit the vibrations stop. <S> It could be due to the wheel balancing. <A> My initial hunch tells me that the reason for this is a bit of angular momentum . <S> Remember back when you were a kid, first learning to ride a bike? <S> At some point you realized that the more speed you have, the more stable you are on your bicycle. <S> This is because of angular momentum. <S> So imagine your up in the air, and you have to wheels rotating at 75 rpm (assuming a takeoff speed of 55KIAS, no headwind, and a tire diameter of 18 inches). <S> You have a decent amount of angular momentum fighting any maneuver that the aircraft wants to make. <S> Consistency is key in safety in aviation. <S> The difference in ground speed for a takeoff could vary from the Vr KIAS ± max head/tail wind. <S> That's enough to significantly alter the dynamics of a maneuver. <S> --EDIT-- <S> If you want to know how much you are affected by this angular momentum, check out the question I posted on the physics stack exchange. https://physics.stackexchange.com/questions/111353/what-is-the-inertia-caused-by-angular-momentum-when-twisted-on-its-rotating-axi/111422 <A> Spinning wheels are not a problem in fixed undercarriage aircraft, there's no good reason to tap the brakes after takeoff if the gear is nailed down. <S> I suspect you answered your own question when you theorized that they may have simply copied that part of the manual. <S> From a wear perspective you may save some wear on the bearings by stopping the wheels spinning, but since you are using the brake pads to do it <S> it's likely less overall wear just to let them stop naturally. <S> CLimbout is a busy time, anything that adds workload without a benefit shouldn't be on a checklist. <S> I'd say you are probably safe to ignore that in a TB-10, however that is just my opinion and it may be worth contacting a TB-10 club and asking them what they think. <A> 1) <S> The spinning wheels will cause vibrations until they are stopped. <S> 2) <S> Flailing tread can do a lot of damage, especially if it becomes thrown tread. <S> After you stop the tire rotation, it just becomes "hanging tread" and will not do any damage. <S> This is why commercial airlines have systems in place to automatically apply the brakes on retraction and the nose tires get pressed against "spin brakes." <S> Also by learning the practice with fixed gear aircraft, it is more likely to be second nature when you move up to retractable gear.	It is good practice to stop your wheel after you lift off due to flailing tread.
Who assigns an arriving aircraft a runway and runway exit to use? I recently bought a simulator for tower controllers ( Tower! 2011 ) and have some questions about the responsibilities of the tower controller: When an aircraft wants to land at 'my' airport I get contacted once they are established on the approach path and already have a runway assigned ("Tower, N1234 with you runway 26L"). Unfortunately sometimes it happens that aircrafts are assigned a runway that is actually to short form them to land - which I found out the hard way by getting punished because the plane was not able to stop on the runway. Who is responsible to assign the correct runway in real-life, the tower controller or the approach controller? If if were up to the approach controller that would basically be a bug in the simulator. Who decides which runway exit an aircraft will use after landing? Again in the simulator I can advise the aircraft to taxi to the terminal via a certain route ("N1234 taxi to terminal via L4 M4 N4") with L4 being the exit from the runway I want this aircraft to take. Unfortunately the aircrafts - in the simulator - decide which exit they are going to use on their own. So it might happen that the aircraft I assigned the route to exits the runway at exit L5 and therefore cannot comply with my assignment. How is that handled in real-life? Does the pilot land the plane and then report back where he is (if I queried the airplane for a position I get a "N1234 is on the ground") or does the tower controller assign an exit that the pilot needs to take - and therefore the simulator would have a bug? <Q> The tower gives the ultimate clearance to land, though the approach controller (if one is available) assigns a specific approach to a runway in the approach clearance. <S> I'm not sure about the game, however in real life if the runway was too short to land on, the pilot would report being "unable" to use that runway and would be assigned another runway instead. <S> It is not the responsibility of ATC to ensure that the runway is long enough to land on. <S> Unless there is a NOTAM otherwise <S> noting that a particular exit is unavailable for use, the pilot can slow down at whatever rate to vacate at any particular exit. <S> However, once they've slowed down to taxi speed they should vacate as soon as practicable. <S> The tower controller may request that a pilot vacates at a specific exit, but if they are unable to they will go for another exit. <S> After vacating the runway, the pilot notifies the tower that they are clear of the runway at a particular taxiway, and then will be (depending on the airport) be asked to switch to ground or be given taxi instructions. <A> The tower will ultimately give the landing clearance as they have the detailed picture of what is going on at the runway. <S> Note that it is a landing clearance, not an instruction. <S> The tower controller can request a runway exit to be used for landing aircraft, however ultimately the pilot is free to choose. <S> If he cannot make an exit or it would require excessive braking a pilot will elect to take a later exit. <S> In general pilots will vacate as soon as practicable not to cause interference with other traffic. <S> Once the aircraft has vacated the runway, the pilot will be given taxi clearances either from the tower controller or from a ground controller on a separate frequency. <A> The Tower controls the runways and therefore designates active runways for arriving and departing traffic. <S> Typically this is done based on current surface winds and aircraft type.	The approach controller is responsible for assigning the runway to the aircraft, but the pilot of the aircraft is responsible for verifying the runway is long enough for his aircraft and rejecting the approach clearance if he feels it is unsafe.
Has a commercial passenger airliner ever had its cockpit fully upgraded? In an earlier question What are the barriers to feasibility of stratospheric cruising for commercial air travel? (i.e. Concorde?) it was suggested that Concorde was not properly maintained as its analogue flight deck had never been upgraded. Concorde production ceased in 1979. Fourteen Concordes saw commercial service. By end of operation in 2003 there were nine Concordes in use. Excluding the military, has any airline or manufacturer ever retrofitted a new design of flight deck to an existing fleet of old commercial airliners? <Q> While many times an upgrade is not economical for older airplanes, sometimes the new features make it worth the cost. <S> Two examples I found were Southwest upgrading their 737-300 fleet , and Delta upgrading their MD-88 and MD-90 fleet . <S> The second article also mentions American and Icelandair 757 and 767 upgrades. <S> The Southwest and Delta upgrades involve over 100 aircraft in each case, which probably helped to make the upgrades more economical. <S> In both cases, a major factor mentioned was the ability to perform required navigation performance ( RNP ) procedures with GPS and other modern features. <S> As the FAA works to implement the NextGen ATC system in the US, these upgrades will offer more benefits for the operators. <S> Also, I'd like to comment on the following statement: <S> Concorde was not properly maintained as its analogue flight deck had never been upgraded. <S> Proper maintenance and technology upgrades are not always the same thing. <S> Aircraft with older systems can be maintained just as well as newer planes. <S> We have airplanes that are 50 years old or older, like the DC-3, which are still flying. <S> While technology upgrades certainly have benefits, aircraft with analog cockpits are still operating just fine around the world. <S> They may not be the most modern machines out there, but proper maintenance is what has kept them flying this long. <A> There's also the MD-10 upgrade to the DC-10. <S> The MD-10 program allows operators to retrofit DC-10s with a new, advanced- technology flight deck. <S> Benefits of the retrofit include a two-person flight deck, weight savings, increased reliability, and commonality with the MD-11 fleet. <S> http://www.boeing.com/commercial/aeromagazine/aero_02/textonly/ps02txt.html <S> Just adding a little more info: FAA Certifies New B757/767 Aftermarket Flight Deck Dreamliner-Inspired Large-Format Display System <S> Enhances Situational Awareness <S> http://www.aero-news.net/index.cfm?do=main.textpost&id=c3201f75-7587-4438-a2b8-e35c3cb34759 <A> There's a couple of cases I know of to hand. <S> UPS upgraded their 727 fleet with glass cockpits, there's also an STC for a full DC9 cockpit upgrade. <A> This required automation of fuel management systems, hydraulics, electricals and pneumatic systems and repositioning these to the overhead P-5 panel. <S> The pedastal was also extended rearwards. <S> There are a number of VIP B727s flying with all glass EFIS cockpit panels. <S> Usually a cockpit redesign will feature a suite of instrument products from one manufacturer for example like Rockwell-Collins, or Smiths etc and present it as an integrated platform. <S> I don't know who owns the STC <S> currently but in theory if you wanted to the conversion could be carried anywhere out through a sub-contractor.	Vaslan developed an STC for a two man Boeing 727 cockpit on the re-engined B727-RE.
Will landing gear with wheel fairings keep spinning due to airflow? I asked this in a side note to a previous question , but I figured it warranted its own question. If a fixed gear aircraft is fitted with wheel fairings, even if you tapped the brakes after lift-off, would the wheels start turning again? With typical wheel-fairings I guess about one third to one quarter of the tire sticks out into the oncoming air flow, and would face perhaps 120 kts wind. All aircraft tires I've seen have grooves running along the direction of travel, with nothing going sideways that would be any obvious wind catcher, so I guess they're pretty much slicks in this regard. Or would any 'normal' amount of friction in the bearings keep them from turning? <Q> This is a very general question. <S> Have you ever seen a car with a bicycle on a trunk rack, and the front wheel is spinning. <S> Sometimes they spin fast, sometimes slow, sometimes not at all. <S> It just depends on the air flow. <S> Sometimes it happens, sometimes it doesn't. <S> I've seen both. <A> My plane has fixed gear with wheel pants. <S> When the wheels are spinning right after take off I can feel the vibration (it's a really small plane). <S> If I tap the brakes or wait a minute or so, the vibration stops and doesn't start again. <S> My guess is that there's too much friction in the wheel/axle to permit the wheels to spin. <S> As you've noted, there's not much on the tire to catch the wind anyway. <A> When flying in formation, I've witnessed landing gear with and without fairings continue to spin for the duration of the flight. <S> I think it really all depends on the specific aircraft designs.	Airplane wheels are the same way, and it all depends on the airflow, the tires and the bearings. So the answer is: Sometimes they spin, sometimes they don't. The airflow over tires sticking out from wheel pants is going to be turbulent and unpredictable.
How would an airplane land if the on-board radio breaks down? Is there a special protocol for a situation where the on-board radio communication equipment suddenly breaks down? Would the pilot be able to land on a busy towered airfield or would they be forced to look for a small landing strip in the middle of nowhere? <Q> It is important to remember that it is often difficult to diagnose radio malfunction during flight. <S> Therefore it is hard to know whether you have a malfunctioning transmitter, a malfunctioning receiver, or perhaps both. <S> You also have the point-of-failure that is the headset you are using. <S> For this reason it is quite usual to carry a spare headset and the first piece of diagnostics <S> is to swap headsets. <S> Many General aviation aircraft also have a handheld microphone and speakers integrated into the radio stack. <S> Once you've ascertained that its the actual transmitter and/or receiver that has failed it is common to set the transponder to 7600. <S> For landing, the relevant detail for the procedure to follow is contained within Chapter 4, Section 2-13 of the AIM : Receiver Inoperative Remain outside class D airspace until the direction of air traffic can be ascertained Notify the tower <S> your type, position, altitude, intention to land and request you are controlled with light signals <S> At 3 -5 miles, advise the tower of your position and join the traffic pattern <S> Watch <S> the tower for light signals Continue to advise of position (downwind, turning base, etc) <S> Transmitter inoperative <S> Remain outside class D airspace until the direction of air traffic can be ascertained <S> Monitor the primary local control frequency as depicted on sectional charts for landing or traffic info. <S> Look out for light signals that may be directed to your aircraft During hours of daylight, acknowledge tower transmissions or light signals by rocking your wings <S> At night, acknowledge by blinking landing of navigation lights Transmitter & Receiver inoperative <S> Remain outside class D airspace until the direction of air traffic can be ascertained <S> Maintain visual contact with the tower and acknowledge light signals as above. <S> The light signals used for an aircraft in flight <S> are as follows source : <S> Steady green - Cleared to land <S> Flashing green - Cleared to approach airport, or return to land Steady red - Continue circling, give way to other aircraft Flashing red - Airport unsafe, <S> do not land <S> Alternating red and green - Exercise extreme caution <S> They can be seen in this video . <A> First thing you do when the radio breaks down is to start squawking 7600 (the code for radio malfunction) on your transponder. <S> Then when you approach the airport they will attempt to contact you first through radio (to see if you can still hear them) <S> and you use alternate means of replying (sending IDENT on transponder, rocking your wings,...). <S> If you can't hear them they will use a light gun to convey messages. <A> Ratchet Freak has a good answer. <S> In addition, please pull out your cellphone and try calling the tower . <S> Somewhere in the bottom of my flight bag I have a small book with telephone numbers at towers. <S> If you don't have that, call Lock-Mart Flight Service at 1-800-wx-brief tell him you need the tower number. <S> Also remember that there is no requirement for a radio in an airplane. <S> NORDO (No Radio) aircraft are perfectly legal although in practice, they operate mostly out of non-towered fields. <S> Operating out of a towered airport is still possible, but it requires prior coordination with the tower. <S> Note please that flight in the SFRA around Washington DC does require a radio, and I have seen no procedures to allow for NORDO aircraft in this area. <A> I was a Junior Technician, later Corporal, Air Wireless Fitter in the R.A.F. in 1952-4, servicing Gloster Meteors' radios at a Flying Training School, and the signal then was for the pilot to waggle the aircraft's wings as he approached, or flew by, on his way to land, to show he could not contact the Control Tower. <S> Then we had to fix it. <S> I was made a Corporal so that I could sign off our work on the aircraft out on the airfield, usually just tuning up to a new crystal to suit the frequencies of a distant Station. <S> I got the promotion so the Sergeant could stay in the nice warm office: <S> I didn't mind -- I was "/Paid" <S> extra, nice for a "National Service Only" erk. <S> Happy days <A> The NORDO procedures are covered extensively in the AIM. <S> That is suggested reading for any pilot. <S> Cellphones are unlikely to work airborne, except close to the ground, and then in remote areas. <S> Most cell systems will ignore a phone which brings up many towers, thereby preventing it from calling. <S> Text might work better. <S> Most pilots don't frequently call towers, but it is worth noting that many times the tower will not answer the phone, depending upon workload. <S> Calling FSS might work better, and they have more direct access to the tower through multiple means. <S> Many pilots carry a small transceiver, which is a good backup device. <S> I use mine to get ATIS and Clearance prior to engine start. <S> At least that way I know it is frequently working. <S> A final point, if you do loose transmit capability, listen on the last frequency you were talking on. <S> They will probably try to contact you, and you may likely get walked through communications changes until you are on the ground, listening only. <S> That has happened to me. <S> The radios lost transmit capability due to a failure in the audio panel. <S> Center handed me to approach, who vectored me to the ILS, and gave me a frequency change to the tower. <S> Tower gave me taxi instructions. <S> There was no need to transmit. <S> No need to use a cellphone or anything else, and no need to dig out a backup radio. <S> But the starting point for understanding the procedures is to visit the AIM. <S> https://www.faa.gov/air_traffic/publications/media/aim.pdf	If your radio stops working, one option is to fly to a non-towered field and do what the NORDO planes do: Overfly the field at a safe altitude, note wind direction from the wind sock or tetrahedron, note other traffic in the area, and fit yourself into the traffic pattern... and land.
If turning off electronic gadgets is so important, why are there no detectors used to find them? It's supposed to be that electronic gadgets' emission are dangerous for airplane systems. If this is true, why don't they use any detectors to locate such emissions? <Q> Three reasons I can think of: It's easy to detect the general presence of a specific transmitting device (a WiFi antenna, say), but very hard to precisely localize it. <S> They could tell if there's one on the plane, but someone with a very sensitive piece of equipment would have to walk up and down the aisles pointing it at people to actually find it in somebody's pocket. <S> And cellphones (when not in use) are generally burst transmitters: they don't broadcast continuously, they just "ping" the tower every so often. <S> This means it could take a long time and a lot of aisle-pacing. <S> Many "electronic devices" which are banned are entirely passive and have no traceable[] emissions. <S> Think cameras, handheld GPS receivers, iPods. <S> (On the other hand this passiveness also means they are extremely unlikely to harmfully interfere with the operation of the airplane, but right or wrong, such devices are still banned in some cases.) <S> It's not that important . <S> There are a few incidents where electronic interference is suspected as a possible factor, but no conclusive evidence. <S> As soon as there is actually a fatal accident where an electronic device can be conclusively blamed as the cause (and I doubt this will happen), the airlines will be a lot more willing to spend the kind of money that would be required to implement this. <S> For a full, evidence-based discussion of the actual risks, I refer you to this question on Skeptics Stack Exchange: <S> Are personal electronics a risk to commercial aviation? <S> [] <S> No traceable emissions. <S> All electronic devices generate some very, very tiny incidental signals. <S> But these are so weak that they will be virtually impossible to detect on a crowded plane filled with its own (approved) electronics. <S> Such emissions are measured in laboratories with extremely sensitive antennas in special, heavily-shielded rooms under carefully controlled conditions. <A> Due to plentiful aircraft shielding and low power emissions of personal electronic devices, practically speaking only a malfunctioning electronic unit that is transmitting the exact same frequencies that the antennas are designed to receive and filter out carry significant probabilities of affecting avionics. <S> One hundred iphones with wi-fi turned on would almost always have an effect, as they would not be emmiting signals received by the antennas. <S> (If there was a rare malfunction a signal could pass from the cabin, through the window and into a GPS receiver, for example). <S> To identify the position of a malfunctioning unit one would need expensive multiple receivers and a computer that triangulates the location. <S> This is just too expensive for the low risk. <S> Even if you could identify a malfunctioning unit, the unit would notmyet be malfunctioning otherwise the aircarft would already be receiving the bad signal and in a sense the aircaft systems are the first detection. <S> It is the aircraft that provides the saftey by properly shielding its electronics from interfering signals to begin with. <S> The antennas restrict communication on narrow frequencies amd usually with certain communication protocols, so even at the right frequency disturbing the aircarft instrumentation or navigation is a freak accident. <S> I think the most probable interference is that a malfunctioning noise transmission across various uncontrolled frequencies could distort the coding a proper signal trying to communicate through the antenna to a given receiver. <A> One thing to point out, electronics on planes really isn't as big of a safety factor as the airline would have you believe, and it's becoming less and less of an issue since consumer demands are pointing towards the aircraft that allow them to be entertained while traveling, such as have WiFi. <S> For the companies that run the phone lines it's a different story entirely. <S> If your careening through the air at 500 knots and you make a phone call, you require the phone towers to do a lot more work receiving your call. <S> I'm not sure why, but I remember reading that the main movement behind not using electronics while flying was really because our telephone infrastructure isn't capable of handling the excess load. <A> The greatest danger appears to be when an aircraft is flying slowly, with landing gear open and there are cell towers on hills level with the approach path, because these are circumstances when a cell phone is most likely to make a call connection. <S> Many years ago working as an airline baggage handler in a country which prohibited all cell phone use during commercial flights, I was astonished to hear baggage carts with phones ringing all the time <S> and it is the airport baggage halls where one could implement this policy or at the check-in counters. <S> I imagine airlines would not be too keen on the extra manpower and wages required.	On the whole the answer lies in the fact that the interference for the odd electronic, people forget to turn off is low risk and does not justify the expense of an advanced locator system.
Do hot air balloon pilots file flight plans? Are hot-air balloon pilots ever required to file flight plans? (can they file?) <Q> As a balloon pilot: no we do not. <S> We do fly regularly in classes G, D, and E and will occasionally wander into class C; but it is very frowned upon... <S> and you better have an aircraft radio or at least call the tower to let them know you are there. <S> Of course balloons always have right-of-way so <S> if you see us get out of the way; we can't control where we're going. <A> So, theoretically, they could file a flight plan or at least alert local ATC to their activities. <S> All of that being said, having been involved in hot air balloon operations before, I think it would not be terribly feasible. <S> Firstly, flying a hot air balloon outside of Visual Flight Rule conditions (being able to see several miles) would be extremely dangerous, so you wouldn't need to file a flight plan for that. <S> Secondly, you generally only want to fly a hot air balloon in very sparsely populated areas (Class G airspace), and while you could have a flight plan there really isn't a need. <S> A more congested area (Class B or Class A) would be extremely dangerous to navigate in a hot air balloon. <S> It's pretty hard to get out of the way, since controlling where you are going is... <S> iffy sometimes. <S> So, in summary, yes it could be done, but in the vast majority of cases there's little need to do it. <S> Other than to just alert local ATC that you will be in the area. <A> ICAO Standards do not differentiate between hot air balloons and other flights when it comes to flight plans. <S> The following is from Rules of the Air (Annex 2): <S> 3.3.1.2 <S> A flight plan shall be submitted prior to operating: <S> a) <S> any flight or portion thereof to be provided with air traffic control service; b) any IFR flight within advisory airspace; c) any flight within or into designated areas, or along designated routes, when so required by the appropriate ATS authority to facilitate the provision of flight information, alerting and search and rescue services; d) <S> any flight within or into designated areas, or along designated routes, when so required by the appropriate ATS authority to facilitate coordination with appropriate military units or with air traffic services units in adjacent States in order to avoid the possible need for interception for the purpose of identification; e) <S> any flight across international borders. <S> Note. <S> — The term “flight plan” is used to mean variously, full information on all items comprised in the flight plan description, covering the whole route of a flight, or limited information required when the purpose is to obtain a clearance for a minor portion of a flight such as to cross an airway, to take off from, or to land at a controlled aerodrome. <S> As mentioned in the note, a flight plan may simply be an abbreviated flight plan, which is submitted over the radio. <S> Such a flight plan would typically just include identification, type, flight rules, persons on board and intentions.	A quick look at the FAA rules regulating hot air balloons makes it sound like, in the USA, they can enter any sort of airspace provided they can do it safely.
What were the disadvantages of early prop driven blended-wing aircraft? I've been researching the history of pre-jet aircraft and I've come across several famous, and not so famous, blended-wing aircraft. The idea seemed to show promise but never really caught on, even for a limited span of time or confluence of technological factors e.g. weight vs engine power etc. Just to be clear, I'm not interest in flying wing and/or tailless aircraft whose early problems are well known, but rather those designs that have tails but have a fuselage shaped to produced a significant component of lift. Just a few of the designs I've stumbled across: Burnelli CBY-3 Cunliffe-Owen OA-1 (Burnelli license) French de Monge 7.4 Soviet LK-1 a.k.a. Fanera-2 There are quite a few more I don't have handy web links for. Junkers did a couple that would probably qualify. The large number of designs from all over the world show that the basic idea offered promise but all the designs eventually went no where despite being tried in many countries, economies and even political systems. That in turn seems strange because in the 1920s-early-1940s, lift seemed more important than speed for larger multiengine aircraft i.e. just getting a load airborne at all was worth quite a few other tradeoffs. As engines grew more powerful that tradeoff lessened but for at least 15-20 years a high lift design should have been more desirable than a high speed one for larger aircraft. The failure of many different designers over the course of three decades to make the blended wing work suggest to me that the basic idea has some inherent disadvantage/s that outweighed any gains. Unfortunately, none of the resources I have consulted offer any clues to why the designs did not "take off." I suspect the designs showed some rapid onset of stall of instabilty but that's just an uninformed hunch on my part. Any clues? <Q> Generally, to create lift means to deflect the oncoming airstream downwards. <S> How and where this is done in detail on an airplane is less important than doing it with a smooth spanwise lift distribution such that the wake behind the aircraft is trough-shaped. <S> A fuselage is disturbing this lift distribution, but not severely. <S> In case of the N-250 <S> it was found that an incidence of 2° produces the lowest drag. <S> However, this also means that the lift is only just right at one angle of attack, and when the aircraft is flown in different conditions, the fuselage can mess up the lift distribution quite easily, especially if it is wider than necessary. <S> During the 1930s and 40s, when this was understood in detail not only in academia, but also in the design offices, progress in engine technology pushed operating altitudes up until planes needed pressurized cabins to transport passengers comfortably. <S> Pressurisation demands a round or nearly-round fuselage cross section to keep structural mass down, so any attempt at widening and shaping the fuselage would result in an unacceptable mass penalty. <S> This ended the experimentation with lift-creating fuselages. <S> As for the N-250, the idea of fuselage inclination in cruise is correct in theory, but resulted in massive protests from the cabin crew which now had to push their carts uphill, ending this kind of optimization quickly. <S> This is why it never caught on. <A> I remember having read that in these airplanes, at high speeds and low angle of attack, it was the center section, the lifting fuselage, that provided most lift, but at an steeper attitude, it was the regular wing that lifted. <S> The shape of the 'lifting fuselage' sides makes suspect an increased 'marginal vortex' drag, this reducing the efficiency of idea. <S> For a new procedure to be added to series, at least in the Automotive industry, they say it must provide a 10% increase in efficiency, along with a 10% reduction in costs, this is why changes that a private owner can introduce in their engines or vehicles may be worth for them but not for a company. <S> The mail boxes open to suggestions by people in the production lines, that once received concepts such as the way to use a single screw or bolt instead of the several previously used, saving the cost of thousands of bolts a year, are closed now, changes in the production line for this minimalist improvements were too expensive to implement in recent times. <S> Besides this, a patented idea must offer an overwhelming advantage for a builder to pay for it and incorporate to their production, if improvement is not big enough as to offer noticeable gains from the patent, the time will be left flowing, when the patents have expired, in most cases advances in technology offer better things. <S> However, some XXI century airplane designs incorporate concepts analog to the Louis de Monge and Burnelli's lifting fuselages. <S> The time will say if it are good enough. <S> Salut + <A> Looking through your first link about the CBY-3, it seems there may be political reasons for the failure of this design. <S> To this day, many organizations still refuse to acknowledge the merits of the design. <S> Part of the issue is probably the interests of much larger companies which were already deeply entrenched by this time. <S> Your second link is related to the Burnelli designs, and the page also offers this explanation: <S> The Cunliffe-Owen OA-1 <S> Flying Wing was almost certainly too late to be a success in the civil marketplace. <S> By the time it was ready to fly <S> it was already 4 or 5 years behind the times in terms of performance and economy.	The length of the fuselage means that it creates considerable lift at small incidences, even with the low lift slope of slender bodies.
Why turn off pitot tube heating? I'm merely an amateur simulator (X-Plane) pilot. On a flight yesterday the airspeed indicator stopped working. After the initial panic I remembered reading something about pitot tubes freezing, found the pitot heating switch, and turned it on. The problem was resolved immediately. This led me to think: Is there a good reason to not turn pitot heating on before take-off, and leave it on for the entire flight? I'm flying a Sud Aviation SE 210 Caravelle <Q> I'm not sure what kind of airplane that you are flying in the simulator, but the checklists for jets typically do have you turn the pitot heat on just before takeoff and leave it on until after landing, just so that this is less likely to happen. <S> Update: I found a French checklist for the Caravelle and it says to turn on the pitot heat before takeoff: <S> Rechauffage Pitot..... <S> MARCHE <A> The aircraft checklist will determine when the pitot heat should be on. <S> Strictly speaking, if the checklist says it should be on, the only reason it should not be on is if the system is inoperative or is causing some issue (if the generator system fails it will drain the battery, as falstro commented). <S> The checklist linked by Lnafziger has the pitot heat ON before takeoff and OFF after landing. <S> Other times it may be "as required" by conditions. <S> The pitot heat makes sure the pitot system remains free of ice. <S> Failed airspeed, especially in IFR conditions, can be serious. <S> The failure may not be obvious, leaving you to stall/overspeed. <S> Leaving the heat on can cause the system to overheat. <S> While some systems automatically protect against this, not all will (especially with smaller aircraft). <S> Checklists for larger jets also seem to have probe heat on before taxi and off right before shutdown. <S> The reason for this is probably safety. <S> Modern aircraft rely heavily on pitot static systems. <S> AF447 crashed partially due to icing on the pitot tubes. <S> Why leave it off and run the risk of icing? <S> The cost of leaving it on is fairly low. <S> On smaller aircraft where the pilot may even be able to see the pitot tubes, the situation may be different. <S> These aircraft have less automation, and the cost of repairing a pitot heat system is higher relative to the rest of the aircraft's maintenance. <S> However, the issue of safety remains. <A> At our airclub, the checklist for C172 shows: ... stuff ... <S> Pitot heat on, check tube warm, turn off. <S> ... complete the walk-around... <S> start... <S> taxi to engine run-up... <S> do run-up... <S> Do final pre-take-off checks, one of the last of which is "pitot heat: ON". <S> I've seen some C172 checklists that say "as required" instead of "on" near the end. <S> There are no further pitot heat items on the checklist except for the "after landing checklist". <S> So we're supposed to just leave it on. <S> During my initial training my instructor mentioned that we turn it off until just before take-off because it can overheat and fail if operated while stationary. <S> I don't remember seeing this in the C172 operating handbook, so maybe they're just being overly cautious or something. <A> Although pitot heat is quite reliable, it can burn out much like an incandescent light bulb. <S> Why waste its useful life without immediate reason? <A>	On the ground, without airflow over the pitot tube to cool it, it will burn out very quickly. By operating something like this when it's not needed you risk not having it available when you need it.
Did Wolfgang Langewiesche ever change his mind about rudder pedals? I get the feeling that if aviation was a religion and had a holy book, that book would be Stick and Rudder . Mostly because it's often spoken of with great authority by people who have never read it. Well, I'm reading it right now. And let me tell you, Wolfgang has got some opinions . Here's one of them, from Chapter 11. The important thing to understand about the rudder pedals is that they are unnecessary; like your wisdom teeth, they serve no very good purpose but can cause much trouble. The airplane needs no rudder pedals. It should have no rudder pedals. In all probability it will have no rudder pedals 10 years hence. I have to give him credit: he put his money where his mouth was. However, the fact that it's now 2014 and rudder pedals are still very much in vogue makes me wonder: Did Wolfgang Langewiesche ever change his mind about rudder pedals, or did he go to his grave defiant to the end? <Q> I cannot source or cite this negative however. <S> I don't actually like this question, since only an answer that he did recant can be sourceable. <S> Any cites showing him supporting his own written beliefs could be disputed by saying "but what about later in life?" <S> This means that a negative answer can only be opinion. <S> It's not like he left in his LW&T the statement that everything he had written previously was a lie. <A> That is how chapter 11 of the book begins. <S> IMHO, <S> I suspect it was a rhetorical statement. <S> For he then spends the rest of the chapter explaining what rudders are used for in aircraft <S> and he contrasts this by giving an example, as a thought exercise, of how it could be done without a rudder. <S> One needs to read the whole chapter and the context <S> the writer comes from rather than just use a sentence in isolation. <S> Having said all this, the author is entitled to his opinion and to have that critically examined, which he does anyway. <A> I think you gentlemen have missed the point. <S> Ercoupe aicraft have no rudder pedals at all. <S> The flight controls are designed to keep the aircraft in coordinated flight automatically, thus eliminating the need for the pilot to use the rudder. <S> Since it is possible to build and fly airplanes without rudder pedals Wolfgang is correct. <S> His main objective in pointing this out to the pilot is to emphasize that in the air the rudder does NOT cause the aircraft to turn. <S> Wolfgang also points out legitimate uses of rudder pedals if the airplane has them, or <S> more precisely, MUST have them because of design inadequacies that leave the designer no choice but to make rudder pedals available to the pilot to address undesirable flight characteristics in certain modes of flight. <S> But again, in the air the rudder does NOT cause the aircraft to turn. <S> Wolfgang did not need to recant his position on rudder pedals because he was correct. <S> He did miss that the trend towards building automatically coordinated flight controls would be short lived. <S> No doubt in 1944 he believed the Ercoupe was the start of things to come. <S> This is understandable considering that no man can predict the future. <A> I don't think he every changed his mind because the statement, and the enclosing chapter, is a proof by contradiction . <S> Assume the contradiction ("Planes don't need rudders!") <S> then go on to show why they do, and therefore the assumption must be false.	NO There is no written record that I have found in researching this question that Langweische ever 'recanted' his beliefs.
How do pilots detect and respond to windshear while landing and taking off? How does wind shear affect aircraft while landing and taking off? How do pilots detect that they are encountering wind shear and what would they have to do to prevent it from turning into a bad situation? <Q> The most dangerous form of windshear for planes is the microburst. <S> This is a downdraft that after it hits the ground spreads out in all directions. <S> It is dangerous particularly for planes low to the ground (on takeoff and landing) <S> When a plane coming in for a landing approaches the microburst it will enter a headwind and see and increase of airspeed and lift, the inexperienced and unsuspecting pilot may then reduce engine power to slow down and keep himself aligned. <S> After the plane passes through the burst it will enter a tailwind decreasing lift which may cause the plane to crash into the ground short of the runway. <S> To prevent crashing the pilot would need to keep power and possibly abort the approach to wait out the burst. <S> All turbine powered airplanes used in §121 operations, except for turbopropeller powered airplanes, must have a windshear detection system installed , this is detected in one of 2 ways, using the onboard weather radar (predictive) or using the wind sensors on the aircraft like the angle of attack and airspeed (reactive). <A> Windshear recognition and recovery, both during takeoff and landing are regularly practiced in simulators. <S> Recognition includes a sudden loss of airspeed or a sudden increase in airspeed (probably to be followed by a sudden loss). <S> Recovery (at least back when I was flying) included going to max power while bringing the nose up until stick shaker activation, which condition you would fly in until through the shear. <A> As soon as uncommanded: speed deviation of 15-20kts. <S> Vertical speed deviation and glide slope deviation of 1 dot <S> and if EGPWS incorporates windshear call outs and Flight Director guidance for windshear recovery; SIMULTANEOUSLY: DISCONNECT AUTO PILOTMAX THRUSTFOLLOW FD GUIDANCE (or WINGS LEVEL MAX PITCH TO STICK SHAKER)DO <S> NOT CHANGE <S> CONFIG(EXCEPT SPEED BRAKES <S> CLOSED <S> IF THEY WERE OPEN)ADVISE ATCADVISE CABIN	Detecting windshear from the ground is done with doppler radars ( TDWR ) and multiple wind sensors ( LLWAS ) which can detect the changes in wind which will be relayed to pilots in accordance with regulations (3-1-8) .
What is a general rule for crosswind correction, especially when landing? I am wondering what is the rule of thumb with correction of the bat? Is it 2° for every 5kts? Now i know you can use a E6B.But im talking about landing ILS or visuals without bracketing the approach. So lets say you landing on runway 06 the magnetic heading is 060, the wind is 080/05kts.So would the correction be 062? The aircraft is a C172 Apologies if this is not a valid question, getting back into aviation <Q> If we set our runway to be aligned to a $x$ axis <S> so the angle is $0°$ and we have an airspeed of $\vec{v_a}$ and a wind of $\vec{v_w}$ <S> , this means that ground speed is $\vec{v_g} = \vec{v_a} - <S> \vec{v_w}$. <S> We want the $y$ component of $\vec{v_g}$ to be 0 <S> so this means that the $y$ components of $\vec{v_g}$ and $\vec{v_w}$ must cancel each other out. <S> The $y$ component of the wind is our crosswind ($v_c$). <S> To get the $y$ component of our airspeed we take $\|\vec{v_a}\|\cdot\tan \theta$ where $\theta$ is our heading (0 is parallel to the runway). <S> This means that $\|\vec{v_a}\|\tan \theta - v_c=0$ or that $\tan <S> \theta = <S> v_c/\|\vec{v_a}\|$. <S> At low crosswind speeds this means that your crab angle in degrees is $\sim 60\frac{crosswind}{airspeed}$. <A> What I have learned during my commercial flight training is making use of the speed number. <S> Take your TAS, devide it by 60. <S> This is your speed number. <S> Now take you XWC (crosswind component).Devide the XWC by your speed number. <S> This is the amount of degrees you should crab to stay on track (wind correction angle) <S> Lets use an example: <S> We are flying in a C172 at 120kts TAS.XWC <S> is 18kts from the left. <S> 120 devided by 60 is 2, so our speed number is 2.18kts wind devided by 2 is 9. <S> Now adjust your heading by 9 degrees to the left (into the wind), and you should stay on track. <S> Worked perfectly fine for me so far. <S> Hope it helps! <S> Cheers <A> For VMC approaches, just fly whatever tracks the extended centerline. <S> There should be no need to look at your HSI, heading bug, etc. <S> other than to make sure you're landing on the correct runway. <S> You find this by dividing your TAS by 60 or just using your mach number. <S> Miles/Minute = <S> MachNumber <S> 10ORMiles/ <S> Minute = TAS / 60Drift <S> correction = Crosswind / (MilesPerMinute) <S> This will get you in the general ballpark. <S> What you should do is then bug this heading and see how it's working for you. <S> If the localizer is swinging one way or the other, then make a 1-2 degree correction to avoid chasing. <S> Rebug this heading and see how that adjustment works. <S> Or just use the flight director... <A> Turn into the wind so you continue on a course parallel to (better directly over) landing runway. <S> Eyeball. <S> No computation required. <S> As you flare, kick rudder to swing nose over runway centerline as you descend. <S> If you time it correctly, you'll land rolling forward down the runway rather than taxiing off across it. <A> Just look out of the window, crab down the centre line and kick off the drift at the flare. <S> No need for numbers. <S> I gather this doesn’t work so well in airliners.	For IMC approaches, take the crosswind and divide it by the number of miles per minute you're traveling.
Can a small plane be floated off of an aircraft carrier? Would it be possible to float a small plane (say a Cessna 150 ) off of the deck of an aircraft carrier without the Cessna achieving any forward motion with respect to the aircraft carrier? If not a Cessna 150, is there a standard GA aircraft that could do it? EDIT: Per a comment from ratchet freak: the takeoff would be done via lift from the wings, not via an engine duct (VTOL), like a Harrier . <Q> As far as I'm aware this has never been attempted (and I doubt the Navy would let me try - though I'm certainly game if they are!), but: A Piper J3 Cub stalls at 38mph (33kts). <S> The USS Enterprise (CVN-65) had a maximum speed of 38.7mph (33.6kts). <S> Achieving zero relative motion would require a little more effort - specifically you'd have to seek out a headwind, and the Cub would have to be operating at an airspeed above stall, but still pretty close to it. <S> For example, if the Enterprise were making 30 knots and steaming into a 10 knot headwind the relative wind on deck would be 40 knots. <S> That's enough to lift the Cub, but as soon as it was in the air it would need to pull itself along (via its engine) to maintain that speed. <S> The Cub would have zero relative motion above the deck at an airspeed somewhere around 40 knots). <S> As a (slightly ridiculous) bonus: <S> The Belite Superlite has a stall speed of 28 mph (25kts). <S> It would be theoretically possible to fly such a plane like a kite from an aircraft carrier. <S> Its advertised takeoff and landing distances <S> (both ~500ft) are also such that it could operate from a carrier deck without need for the catapult to launch or arresting wire to stop. <A> A Cessna 150 can take off at 48 knots rotation speed. <S> An aircraft carrier can do 30 knots, and an 18 knot headwind is certainly possible at sea. <S> That puts a 48 knot wind over the wings, enough for the Cessna to take off. <S> The engine would counteract drag, allowing the plane to "float" off the deck. <S> If you have any doubt about this being possible, just watch what happens if you don't tie down your plane properly. <S> http://www.youtube.com/watch?v=IPOtDPHjW-Y <A> What you say is not only possible, but it has been used to land a plane on a much smaller (and a bit faster) ship than an aircraft carrier. <S> Try to search in the web for the video "Extreme small plane landing on a ship at sea". <S> Here is a working link at the moment: http://www.youtube.com/watch?v=pUdzVnZBaoY <A> It all depends on the minimum flight speed and the ship's maximum speed. <S> Even with the slow speed of submarines, floating a flying machine is possible if the machine has been designed that way. <S> In order to increase the observation radius of submarines (typically only 5nm), an unpowered gyrocopter was designed in 1941 to lift an observer 500 ft up into the air to increase the observation radius to 25 nm. <S> Gyrocopters are known for their low flying speeds, and this one, the Focke-Achgelis 330 , was designed to be folded away in a watertight container and to be stored on the deck of the submarine. <S> It could be assembled and de-assembled within 20 minutes and was then towed behind the submarine like a kite. <S> The minimum flight speed was only 27 km/h (14.5 its), just enough for a submarine going at full speed and a little wind. <A> The forward speed of a carrier might not be the listed max speed, if heading into a strong headwind. <S> However, if the relative wind is great enough, the aircraft wings would create more lift than the weight of the plane. <S> There are of course issues like structure induced turbulence which might adversely impact handling. <S> And if near equilibrium, the aircraft may never fly beyond the bow. <S> If planning on this type of operation, would look for a Vx (adjected for engine off or idle) relative wind to allow a reasonable climb (if you call the ascent that) to clear the structure. <S> Also, I would plan on factoring in the ground effect of working off the carrier deck, and then having that effect reduced as altitude was gained. <S> Finally, from practical experience, I would expect the aircraft to become airborne prior to the stall speed, due to ground effect, probably a lighter that gross weight loading, and lots of other factors.	So, given a lightly loaded cub and an Enterprise -class carrier at flank speed, it is at least theoretically possible to float that aircraft off the deck (if it were lightly loaded, and thus had a lower stall speed).
How does a large cargo plane like the C-130 Hercules take off and land in such a short distance? So I was at an air show and saw a C-130J Super Hercules showcasing its capabilities. The take-off distance it covered was amazingly short (I guess equal to fighter jets), even though it uses propeller based engines. The landing was also super short. My questions are: How does such a massive plane manage to take off in short distances ? Is it because it has four engines? During landing, I couldn't see any thrust reverser (as in commercial jets) in play. What tech does it use to stop so quickly? <Q> Assault Takeoff/Landing Technique <S> This is a significant reason for the C-130's performance that you witnessed. <S> " <S> Assault" takeoff/landing speeds are lower than normal speeds, and closer to stall speed. <S> Also there are some weight limitations. <S> Further, the crew must be specifically trained. <S> Stopping Quickly Any idea of a smooth landing is thrown out the window. <S> The intent is to "plant" the wheels at about 300 feet down the runway. <S> That is, transition immediately from approach attitude to actually landing rather than assuming a touch-down attitude and letting the aircraft float down to the runway. <S> The nose gear is pushed to the ground and the instant the wheels are on the ground the props are thrown into full reverse, now pushing air forward. <S> At the same time the pilot puts all his might into mashing the brakes. <S> He would "stand on the brakes" as we say. <S> The yoke is also pushed full forward which puts as much weight as possible on the landing gear. <S> The anti-lock brake system is critical here, preventing skidding out of control and blown tires. <S> In Vietnam, in combat conditions, 130 pilots would put the props in reverse before touching down. <S> If you've seen the video on YouTube of a C-130 landing on an aircraft carrier, they did it there too. <S> J's Props are a Huge factor <S> The performance boost of the J models thanks to the new prop and engine is amazing vis-a-vis the older models. <S> But fundamental airframe limitations are still there. <S> Nonetheless more blades (6 vice. 4) and the "un-ducted fan" design simply pushes more air. <S> Show <S> Off Configuration <S> An empty airplane with a light fuel load of course maximizes the short takeoff and landing performance. <S> C-130 <S> Has Fowler Flaps <S> Not blown flaps. <S> Just because the props push air over the wing does not make it blown flaps . <S> Otherwise, yes, the C-130 was given lots of flapage precisely for this purpose. <A> Takeoff and landing distance have a lot of variables. <S> One is certainly thrust. <S> The plane is designed such that it has enough thrust to reach takeoff speed within the available takeoff distance. <S> For landing, the propellers are able to reverse the thrust and add extra braking power to stop in a shorter distance. <S> Another variable is landing and takeoff speed. <S> If you lower takeoff and landing speeds, it takes less distance to get going and to stop. <S> Being a propeller plane with a straight (non-swept) wing, it is designed to fly slower than jet aircraft. <S> This means the plane needs less angle of attack to fly at slower speeds. <S> The C-130 also has very large flaps for this purpose, and they contribute to lowering takeoff and landing airspeeds in two ways. <S> First, the flaps are very large, which adds more wing area and also deflects more air downwards, increasing lift. <S> Second, the flaps are placed directly behind the engines, which allows the flaps to direct some of the engine thrust downwards, further increasing lift. <S> Weight is also important. <S> While the C-130 is designed for good performance at 155,000 lb, and can fly at up to 175,000 lb, it will be much lighter in a demonstration. <S> From an empty weight of 75,562 lb, fuel and crew will still leave it well below its typical operating weights. <S> Landing performance will also be better with a lower landing speed and better deceleration. <S> The newer C-130J also performs better than the older C-130H . <S> The newer engines on the J model produce up to 4,637 shaft horsepower (shp) each (though they are listed here at 4,705 shp), while the engines on the H model produce up to 4,590 shp each. <S> The empty weight on the J model is 75,562 lb and on the H model is 75,800 lb. <S> So with the empty weight going down by 238 lb and the power increasing by at least 47 shp, and improved propellers, the J model has better performance. <S> The takeoff distance at 155,000 lb is 3,127 feet for the J model versus 3,586 feet for the H model. <S> The H model can take off in 1,400 feet at 80,000 lb (probably closer to the weight in demonstrations), so the J model can probably do even better. <A> the props are turbo props (more specifically the Rolls-Royce AE 2100 with 4.6k shaft horsepower) and very efficient propeller blades. <S> This combines into a takeoff distance of 953 m at 70 ton, and at the air show they would have kept the plane nearer the empty weight (which is half that) which shortens the needed takeoff length. <S> To compare the Lockheed C-130 Hercules has a slightly longer takeoff distance at the same weight but only needs half that when the weight is reduced to 36 ton. <S> These propeller blades can change their pitch which can reverse the thrust direction, plus the wheel brakes (even large jets use mostly wheel brakes see this answer ) <A> Propeller driven aircraft usually have a better acceleration/deceleration rate compared to similar jet driven aircraft. <S> This, combined with a straight/tapered wing, instead of a swept wing, and large blown flaps (as stated by fooot) make an aircraft which is able to take-off and land on very short runways.	The lower weight means that takeoff performance will be increased by better acceleration and a lower liftoff speed.
Is ground school required to get a Private Pilots License? I know that there is a written exam that you are required to take, but do you have to go to a class in order to study for that test? If I'm really good at just learning from a book, can I just learn that way, maybe take a couple practice tests and then take the exam? Or are they going to need proof that I went to some certified class? More subjectively: Assuming it's allowable, is it a bad idea? <Q> In Canada, you are required to have 40 hours of ground school instruction. <S> See Canadian Aviation Regulations 421.26 (3)(a) : completed a minimum of 40 hours private pilot aeroplane ground school instruction on the following subjects ... <S> Ground school instruction is defined as ( CARS 400.01 ): classroom-type instruction generally given to one or more persons and covering an organized program of lectures, homework or self-paced study that adheres to an approved training program. <S> So, you can learn by self-study, but it needs to be an approved training program. <S> This would mean that a flight instructor would need to sign off on the self-study program. <S> The regulation is at Title 14 Code of Federal Regulations, §61.35(a)(1) : Received an endorsement, if required by this part, from an authorized instructor certifying that the applicant accomplished the appropriate ground-training or a home-study course required by this part for the certificate or rating sought and is prepared for the knowledge test ... <S> Because in both cases an instructor must sign off on your preparedness for the examination, and passing the examination demonstrates that you meet the standard, in my opinion, the only thing that would make self-study a bad idea is if self-study is not an effective learning method for you, which could delay your training. <A> My students have not been typical, and many are scientists and engineers, and motivated high school students. <S> Only one, out of hundreds has taken a formal "ground school." <S> Probably 50 (just a guess) have bought, borrowed or somehow used videos or online coursework. <S> The rest (hundreds), have elected to study on their own. <S> I provide a modified FAA syllabus, my supplemental syllabus, and pointers to a large number of resources. <S> I also provide a reading list. <S> Since I am in the Northeastern US, they read "Weather Flying," by Robert Buck. <S> Even if they are a primary student, I want them to understand many of the things Buck talks about. <S> But that is just an example. <S> Most of my students meet with each other for review sessions, and if they get stuck on something, I might get a call. <S> This method won't work for everyone. <S> Many flight schools make money by offering ground schools. <S> Many CFIs are more comfortable with their students getting a comprehensive ground course in a more formal setting. <S> Some students might be more comfortable with a structured classroom. <S> However, when the students have free reign to explore their material, I find they do better. <S> As an example, one student had a hard time with turbulence in flight as a primary student, and she studied weather phenomena and became quite knowledgeable on lifted index, and so on. <S> This is typical of students who are curious and motivated. <S> So if one is disinclined to go with a traditional ground school, and your instructor(s) are supportive, from my experience it is not only doable, but can produce superior results. <S> Oh, on the written? <S> I cannot remember any student getting below a 94. <S> It may have happened, but if it did it was unmemorable. <S> I realize that this answer is not laden with regs and manual quotes, but it reflects experiences having instructed for 40 some years. <S> An aside for CFIs, the rules may have changed recently, but I normally sign off for the written with my AGI certificate. <S> The record keeping requirement is different. <A> As noted above, a ground school is not required by the FAA but a sign-off by an instructor is. <S> I do not know if this is still valid, but <S> a decade ago, one of the big pilot training companies (King? <S> Sporty's? <S> Gleim?) <S> would send you the equivalent of an instructor's endorsement after you took that company's ground school course in the comfort of your own home. <S> So at least back then, yes, if you sent in the required completed home school tests, you did not need to attend a ground school class. <S> Is it a good idea? <S> I vote NO. <S> the reason is that these courses teach pretty specifically to the tests and little else. <S> There is a lot of knowledge that you won't get by taking these courses without an instructor even though you can pass the test. <S> Remember that they are teaching the MINIMUM you need to be safe. <S> Choose well. <A> A ‘ground school’ per se is not a required part of a Part 61 flight training program but ground instruction is an integral component of Part 61 instruction per §61.105 and §61.107. <S> The FAA has tightened down considerably on this stuff <S> and it’s a good idea for CFIs to document this ground work with logbook endorsements verifying all items of §61.105(b)(1-13) and §61.107(b)(1-10). <S> As for home study ground school programs like Sportys, King Schools, Jeppesen, etc., they are acceptable, though I recommend using the FAA handbooks for this as they are much more concise and succinct and the FAA will inevitably test you on their content. <S> If you have questions from the reading, you are advised to discuss this with your flight instructor. <S> As to in classroom ground schools, I can advise that they are useful in some respects as they can help you with ‘catches’ in the regulations and learning the enormous amount of material that goes into flight training.	The FAA says : If you are unable to attend a ground school, the self-study method can be satisfactory, provided you obtain the proper study materials and devote a reasonable amount of time to study.
Why is it rare for small aircraft to have winglets? I've noticed that winglets are very rare on small aircraft. I wonder why this is the case. Wouldn't they have the same advantages, especially because they travel at low speed? Or is it just a wrong impression I got and they aren't that rare? <Q> I've talked to a couple of aerodynamicists, and for small aircraft when you run the numbers the improvement offered by winglets is often less than the drag penalty caused by their weight (which also reduces allowable payload). <A> As others have pointed out winglets don't make much aerodynamic sense for small aircraft. <S> The point of a winglet is basically to deflect the wingtip vortex away from the lift-producing part of the wing, granting an increase in effective wing span without the added form drag of actually making the wing longer. <S> The winglet itself creates some form drag though, and it adds weight. <S> On most small aircraft the potential improvement in wing efficiency doesn't exceed the weight and form drag that result from adding the winglet. <S> What you will find on many small aircraft are Hoerner-style wingtips (either installed at the factory or added later through an STC modification). <S> At lower speeds these have aerodynamic benefits similar to winglets, but without the additional form drag, and usually little or no added weight. <A> First, winglets look fancy but will not help that much in drag reduction. <S> They were pushed less by engineers than by marketing , Boeing's in particular. <S> They help a litte in ideal conditions, but in sideslip or at high speed they can quickly increase drag. <S> Then, most small aircraft are designs from a pre-winglet era. <S> Adding them means to invalidate the type certificate, unless someone takes the initiative to re-certify the aircraft with winglets. <S> I guess nobody has seen this as a profitable endeavor so far. <S> Gliders benefit from winglets because in competitions they are grouped in classes. <S> Membership of some classes is defined by wingspan. <S> Gliders get better with increasing wingspan, so if regulations limit the lateral extension, the way out is to extend the wings upwards. <S> If there is no such artificial limit, it will in most cases be better to expand the wing in spanwise direction . <A> Many small aircraft designs are rather old and winglets were not common on airliners either when they were certified. <S> For airliners that fly 8 or more hours a day saving a few percent on fuel quickly pays off the additional development and certification, so winglets were adopted quickly there. <S> But typical general aviation aircraft does not fly anywhere close to that and the few that fly more and would be worth upgrading (and their owners have money for upgrade) are not enough to make the design and manufacture profitable. <S> Note, that winglets did find their way to gliders, especially competition ones, as the little benefit is more noticeable there. <S> They also do appear on some newer designs, most notably the Diamond ones ( DA20 , DA40 , DA42 ). <S> The situation is very similar to why we don't see more aircraft diesel engines. <S> They are more efficient, use cheaper fuel and are somewhat cheaper to maintain, but the certification is so complicated that there are only few modifications available. <S> Also most GA aircraft are not really very efficient to begin with. <S> The DA20-A1 claims glide ratio 14:1 and that is way better than most competitors. <S> Compare with airliners where 18:1 is nothing special (was claimed by A320 some 30 years ago). <S> So winglets are not going to help as much. <A> One possible explanation is that large amounts of sweep and higher indicated airspeed are less common in "smaller" GA aircraft. <S> Larger and faster aircraft with large amounts of sweep literally plow the air aside, resulting in a significant spanwise airflow at the wingtips. <S> Winglets are touted for reducing the strength of wing tip vortices, and are said to generate some forward force from the wingtip vortex, but they also may improve efficiency simply by bouncing the span wise flow aft, which would generate a small amount of thrust. <S> The winglet "fence" may also allow a slightly lower AOA for the same amount of lift by helping maintain pressure differential all the way to the wingtip. <S> Lower AOA means less drag. <S> An earlier form of winglets, wing tip fuel tanks, also served as a wing tip fence in addition to acting as a wingtip weight roll damper and spanwise weight distributor. <S> Many smaller, slower planes do not benefit enough from winglets to justify the additional cost and weight. <S> However, they may be seen on STOL aircraft to help trap a bit more air under the wings for high AOA slow flight, along with slats and flaps; and more competitive gliders, where a slight advantage is meaningful. <A> My general understanding is that winglets are most beneficial for aircraft that spend a lot of time in a rather narrow window of possible angles-of-attack-- e.g. an airliner in long-range cruising flight. <S> Small aircraft tend not to fit this profile, unless they are flown by really boring pilots.	For larger aircraft that fly long distances, the proportion of the aircraft's weight that is due to the winglets is much smaller than it is for small aircraft, so they don't have this problem and that makes winglets a viable strategy.
Why are swept wings better for breaking the sound barrier? I'm told that swept wings perform better when an aircraft is trying to break the sound barrier. I was wondering why that would be? <Q> It's all about the 'effective' Mach number that the wing sees. <S> In essence, for a swept wing, the Mach number that the wing 'sees' as far as compressibility effects are concerned is the Mach number of the component of the freestream normal to the wing chord: <S> (Source: stanford.edu via archive.org ) <S> so you'll get supersonic flow over the wing before the freestream is supersonic). <S> Of course, once you fly supersonic, there's really no getting around having shock waves over the wing - however <S> , you can reduce their strength with wing sweep. <A> Swept wings are beneficial at transonic flight regimes (M=0.8-1.2). <S> At transonic flight regimes there is a drastic increase in drag (CD is more or less constant up until that point) due to the effects of compressibility, which manifest themselves in local sonic regions on the wing (the plane itself can be flying at M=0.78, yet over some portions of the wing, where the pressure is low, velocities may go sonic and supersonic). <S> There is a very large amount of wave drag in such regions. <S> The swept wing essentially reduces the effective velocity, so the flow remains subsonic and shocks do not form over the wing, thus not leading to the generation of large amounts of drag. <S> Check out stuff on critical Mach number (drag divergence number). <A> In general, swept back wings aren't better at breaking the sound barrier. <S> Indeed, if you see the first plane to break the sound barrier in horizontal flight (the Bell X-1) it didn't have swept wings. <S> And it was developed after swept wings were developed. <S> What happens to wings as you get supersonic is shockwaves flowing over the wings. <S> Specifically control surfaces. <S> If you get shockwaves over your control surfaces you will basically lose control. <S> During WW2 several P-51 Mustangs and P-38 Lightnings crashed after being unable to recover from a dive. <S> Both planes had engines fast enough to bring them to 70% the speed of sound in horizontal flight. <S> In a dive it is entirely possible for them to break the sound barrier. <S> And indeed it was speculated that that's what caused the crashes. <S> Dive breaks were retrofitted to P-38s to allow them to slow down enough in a dive to regain control. <S> If you want to continue flying at or beyond Mach 1 you need to avoid your control surfaces from entering shockwaves. <S> Since shockwaves are generally conical in nature you basically have two techniques you can use: <S> Sweep the wing back so that they stay within the cone of the shockwave. <S> Make your nose longer so that you push the shockwave away from the wings (or push the wings back away from the shockwave depending on your perspective). <A> Jacob 's and Flanker 's answers are correct. <S> That's effective Mach Number. <S> As I remember it's been detected by Busemann. <S> Swept wings can fly therefore sub-sonic depending on Mach number. <S> OK- one can fly also with straight wings supersonic- <S> then one needs other airfoils. <S> See e.g. the starfighter. <S> This is a non-swept-design because Starfighter is an american design and Busemann was a german. <S> Disadvantage of sweep: One has boundary layer displacement and therefore it's nearly impossible to keep laminar flow. <S> Advantage of sweep: Reduced motion of neutral point compared to straight wing when going to supersonic. <S> Therefore some machines with straight wings crashed because pilots couldn't recover. <S> ----Edit <S> ---Sweep reduces motion of the neutral point. <S> Lowest motion is visible for a delta wing. <S> : See Schlichting/Truckenbrodt Band <S> 2 P. 214/227 ch. <S> 8 pict 8.59/8.70 (my bible). <S> Therefore sweep/delta reduces control problems, sorry.	By sweeping the wing back, you can get closer to the speed of sound without getting supersonic flow over the wing (remember, a wing generates lift by accelerating the air flowing over it, thereby decreasing the pressure -
What does the Boeing 777 autopilot do after reaching the last programmed waypoint? As I understand it, a series of waypoints can be programmed, by a pilot, into one of the autopilots on a Boeing 777. If the autopilot is engaged, the autopilot will cause the aircraft to fly to each waypoint in turn, automatically steering the aircraft as necessary. It is not clear to me whether the autopilot automatically disengages after reaching the final waypoint or whether it maintains (for example) a magnetic heading and altitude. What happens after reaching the last programmed waypoint if the pilot does not intervene? <Q> The first point I would stress on is that you don't program the autopilot. <S> You program the FMS (Flight Management System), which looks like a very large calculator. <S> In this picture it is the device under then first officer's hand. <S> On top of the PFD (Primary Flight Display) you see the MCP (Mode Control Panel). <S> This is what controls the modes that the autopilot system will follow, here is another image of it: <S> Typically the entire flight plan is programmed into the FMC and then during various stages of flight, the autopilot is engaged to help with navigation. <S> This flight plan includes the departure, enroute waypoints or tracks, and then generally the arrival at the destination; but that is it - <S> it does not include the runway information, etc (as this may be subject to change). <S> The FMC takes this information and other data (weight, fuel, temperature, weather, etc.) <S> to calculate a flight plan which is then displayed; and the pilot will then select and activate a flight plan. <S> In most commercial flights however, the flight plan is already loaded in the FMC from the flight operations department and the pilots simply select the predefined flight plan. <S> Punching in a large flight plan takes a significant amount of time so many times this is already downloaded from the flight ops center. <S> At any stage of flight, the autopilot may be armed and engaged to do one of many things - either maintain thurst, or heading, or control the climb/descent; or follow the flight plan. <S> It may also be disarmed during any stage of flight. <S> If the autopilot is armed and it set to follow the FMC's flight plan; then after the last waypoint it will follow the waypoint heading. <S> So, if the last way point is a holding pattern, it will continue on that pattern. <S> Note that reaching the end of the flight plan from the FMC does not disengage the autopilot <S> ; there are many other things that might do that though. <S> All the above comes from my time in a 737 and 777 simulator. <A> The last waypoint is usually at a holding pattern where the plane will fly in circles until the pilot disengages to continue to land. <S> For example in Helios flight 522 <S> the crew got incapacitated and the plane ended up in a holding pattern for an hour until it ran out of fuel. <S> This was a Boeing 737 <S> but I imagine the 777 having the same. <A> When a Boeing Jetliner reaches the end of the programmed flight plan track with the autopilot engaged in Lateral NAV and the pilot does not intervene, (which is usually at a terminal aid (VOR or NDB) at the destination airport); the autopilot will remain engaged, however the tracking mode will default to the last flown track heading into the last navigation aid and the heading window will open showing the numerals. <S> Pilot intervention is then required to change the heading or tracking of the aircraft as desired or instructed by ATC.	If the last waypoint was a marker it will reach that marker, and then continue at that heading and speed; even though there are no more commands coming to it from the FMC (since its at the end of the programmed flight plan).
Why is Thunderbird 5's number upside down? Why is Thunderbird 5's number written upside down? <Q> This is because Thunderbird 5 is the opposing solo, and spends almost all of its time inverted. <S> Apparently though, this plane's number was not always painted upside down: Just guesswork on my part, but maybe the Thunderbirds did not fly inverted maneuvers before the F-16s? <A> Dennis Graham USAF "Thunderbirds" Alumni 1985-1989. <A> Just for clarification sake, Thunderbird 5 is the LEAD solo, not the Opposing Solo. <S> Opposing Solo is Thunderbird 6. <S> The 5 is upside-down because During the show he spends the most time upside-down. <S> On crowd passes, and show center, he is usually inverted. <S> Also, the F-4 Phantom and T-38 Talon fly perfectly well inverted. <A> When the Thunderbird's fly the reflection pattern, one plane will be right side up flying level. <S> Number 5 will be upside down and below the first one. <S> They are like reflections in a mirror, bottom to bottom. <S> Number 5's engine number is written upside down, so that it can be read correctly. <S> If they fly the calypso pattern, where one plane is flying right side up and the second will be above it, upside down, the upside down plane will always be number 5.	The #5 is painted upside down because it represents how the lead solo spends most of his time during an aerial demonstration.
Where can I find Air Traffic Control information material suitable for beginners and students? I would like to learn more about how the Air Traffic Control system works - are there any resources available which describe the system that would be suitable for a beginner or student? <Q> Another good reference would be the training materials for VATUSA. <S> This is part of an online system called VATSIM where people both fly and provide ATC virtually. <S> Although some of it does not apply to real operations (and of course none of it should be actual operations), it still covers real procedures based on the actual rules. <S> The basic guides do a good job of providing an introduction to the basic concepts, but the more advanced stuff is less helpful. <S> Other regions have their own VATSIM organizations, if you prefer a region other than the US. <S> In addition to the materials available, participation is also great for learning. <S> Through VATSIM you can get training on the materials and then get hands-on experience working with (virtual) traffic. <A> The first two places I would start would be the FAA's Air Traffic Control landing page , and Chapter 4 of the Aeronautical Information Manual which deals with air traffic control (and is generally the level of information student pilots are expected to be familiar with). <S> While these references are both for the US/FAA air traffic control system there are strong similarities among the systems in most countries (the ones with the greatest variation would be countries where the military handles air traffic control). <S> If you're looking for more advanced information pretty much all of the operational and training manuals the FAA uses are available to the public . <S> These are likely of more interest to someone studying to become an air traffic controller - the information in them is substantially more technical and "job-oriented" <S> than what's presented in the resources above. <A> This is a comprehensive introduction to background aviation knowledge from a controller's perspective. <S> Beyond that and getting into phraseology, there is FAA JO 7110.65 . <S> This document is THE standard for U.S. air traffic control procedures. <S> Everything controllers say comes from that book.	The Air Traffic Basics course is the first information new FAA controllers are exposed to, and it is available to the public .
How much data do FDR and CVR generate on commercial jets? I'm wondering about how much CVR and FDR data an A320 (for example) would produce and at what intervals. I believe that there are 4 or 5 voice channel and several sensor data things. I'm trying to get some data on commercial jets. Is there any place I could get some data on this? <Q> The requirements for Flight Data Recorders (FDRs) on airliners like the A320 is in 14 CFR 121. <S> For a good summary of the requirements for flight recorders in various types of aircraft, see the NTSB FDR Handbook . <S> Depending on the certification date of the aircraft (14 CFR 121.343), the FDR must record between 6 and 17 parameters. <S> Since engine parameters are included, this could be up to 23 different parameters on 4-engine aircraft. <S> Newer Digital FDRs (DFDRs) must record at least 88 items (14 CFR 121.344). <S> Some of these parameters are conditional, and some require multiple parameters, so the total will probably be more than 88 parameters. <S> According to this page , tape-based DFDRs can record at 64 12-bit data words per second. <S> Newer DFDRs using solid state recording can store up to 256 12-bit data words per second. <S> This 256 words per second is also specified in the information on this FDR . <S> It says it can record >100 hours at 64 words/second, which translates to about 35 MB total. <S> The parameters are per DO-160C standard, which you have to pay to access. <S> Accident reports will generally include readouts from relevant parameters, to give an idea of the items that are recorded. <S> There is a table here showing some parameters, the measurement range, and recording intervals. <S> The interval is anywhere from 0.125 seconds to 4 seconds depending on the parameter. <S> Aircraft may also have a Quick Access Recorder (QAR), which records many parameters (over 2000). <S> However, aircraft are not required to have one and the QAR is not required to survive an accident. <S> Airlines use them for data to improve operations, and they can also be used in less severe crashes for analysis. <A> From Wikipedia: Flight recorder An FAA-standard flight data recorder will record a minimum of 88 parameters, sampled several times per second. <S> An FAA-standard cockpit voice recorder will record four channels of audio. <A> You can access the Honeywell website and download and read the manuals, brochures, drawings and schematics about connections of voice and data recorders. <S> Honeywell is the largest manufacturer of black boxes for commercial, civil and military aviation. <S> Honeywell was among those who provided the black boxes for the A320 that crashed in the French Alps. <S> There are many models and types of Flight Data Recorders (FDR) and Cockpit Voice Recorders (CVR), and they also record the status of other devices. <S> There are many types of FDR's and CVR's whose characteristics depend on the type of aircraft and customer specifications.	The NTSB report on the US Airways 1549 accident notes that the FDR recorded 178 parameters during the flight.
Can a super land without flaps/spoilers? Can the Airbus A380 or Boeing 787 land safely without flaps/slats/spoilers or thrust reversers? <Q> See a report here <S> where an A380 landed with no flaps. <S> This was at the Auckland, New Zealand airport, where the runway is 3,635 m (11,926 ft) long. <S> The pilots have checklists to follow in the event of issues with flaps, which include information about what speeds they should fly with what amounts of flaps. <S> They simply land at a higher than normal speed. <S> The brakes can end up getting hotter than normal, so they may have to stop and let them cool or have them inspected by emergency services. <S> The tires are designed to deflate with fusible plugs before high temperatures would cause them to blow. <S> Aircraft are also tested to make sure they can reject a takeoff at high weights (higher than normal landing weights) using no thrust reversers. <S> Here is a video of the 747-8 doing this test. <A> Specific information can be difficult to come by, and each airline may have their own guidance on the subject. <S> I wasn't able to find anything for the 787, but for the according to one 777 crew handbook I found , flaps up landing was not part of certification: <S> All Flaps and Slats Up Landing <S> The probability of both leading and trailing edge devices failing to extend is extremely remote. <S> System reliability and design have reduced the need for some traditional non-normal landing procedures. <S> As a result, an all flaps up landing <S> NNC was not required for airplane certification and does not appear in the AFM or in the QRH. <S> Basically this means that a demonstration of a no-flaps landing was not required during certification, so no specific guidance appears in the official handbook, and the manufacturer makes no claim that it can be done safely. <S> None of the Boeing 787 handbooks I found had official procedures for a flaps-up landing either. <S> That doesn't mean that it can't be done, but pilots are "on their own" so to speak, and the airplane may not be usable afterward. <S> [ <S> ] <S> But the basic procedure you'd expect them to follow is somewhere along these lines: <S> Attempt to troubleshoot flaps first (best to avoid the problem altogether) <S> Remove excess fuel (either dump or burn) <S> Pick suitable airport considering runway length, altitude, and safety gear (e.g. EMAS ) <S> Declare emergency and prepare airport (ready the fire trucks, etc) Approach above no-flaps stall speed and touchdown as close to the start of the runway as possible Engage brakes, spoilers, and thrust-reversers as appropriate "Please please please stop..." <S> Write a book. <S> [] <S> "If you can walk away from a landing, it's a good landing. <S> If you use the airplane the next day, it's an outstanding landing." <A> Any aircraft can land without those devices. <S> I would say that the Gimli Glider is a nice example, with no power it could not extend its flaps/slats. <S> They are used, as @ratchetfreak notes in the comments, to reduce the touchdown speed and, as a consequence, the runway length needed to reach a stop or taxiing velocity. <S> To be noted, also, that a safe landing is mostly defined by the vertical velocity at tochdown, usually in the order of 1-3 feet per second. <S> See for example this accident report where it states mild touchdown rates [...] less than 5 feet per second <S> Since the vertical component is the relevant parameter for a safe landing, and given that without flaps/slats the forward velocity will be larger than usual, the aircraft will have to approach with a shallower angle than the usual 3°. <S> The absence of thrust reversers, as you might imagine, will only affect the braking process.	Even the largest commercial airliners are able to land without flaps, since flap failures do happen occasionally.
Is it technically feasible to make a solar hang glider? Is there any hang glider with solar sheets on top that can charge the e-trike or the e-Lift's battery in flight ? Just like the Sunseeker ... <Q> I think you've got your terminology crossed here (but it's not your fault - your sources don't seem to clear on it either). <S> A hang glider is by definition a solar vehicle: <S> They're non-motorized, and the pilot keeps them aloft by seeking thermal lift (created by the sun shining on the ground and heating it up) or ridge lift (created by wind striking the side of a mountain/hill (ridge) and being deflected up. <S> Both of these rely on the sun (either directly heating the local ground, or unevenly heating various parts of the Earth's surface, ultimately creating wind). <S> What you're referring to would be a solar-powered ultralight aircraft -- basically a hang glider with a motor strapped to it, or possibly an electric powered paraglider . <S> (A little more Googling reveals <S> this wasn't as cool as I previously thought <S> - they seem to have been using a support vehicle to recharge their battery packs (with solar cells). <S> As far as I'm aware no such vehicle is commercially available at this time (May 2014), but the materials and technology to construct such a vehicle are certainly available (the folks over at the Experimental Aircraft Association could probably provide guidance on building something like this), and it wouldn't surprise me if commercial or kit-build solar ultralights become available at some point in the future. <A> I don't believe it can be done. <S> The area of a tandem wing isn't large enough. <S> With solar power at 1kW per square meter that will be 15 horse power but the conversion efficiency is not 100%. <S> It is more like 20% so you are looking at 3 horse power. <S> A typical trike needs a minimum of a 25 horse power motor. <S> For example the electric Icaro uses a 10kW motor <S> and it's not even Tandem. <S> The wing area would only be enough to provide 20% of the needed power. <A> Solar power on Earth peaks at somewhere between 400W and 1.3kW per square metre, in theory, at midday. <S> In practice, we can typically expect more like 40-70% of this to be available due to inefficiencies in the solar panels and the fact the wing wouldn't be pointing directly at the sun. <S> This is discounting clouds, and only at midday. <S> At any other time, the amount available is lower. <S> Taking the best case scenario (1.3kW at midday at the equator, 70% available) <S> then we still only have ~910 watts, or a little over 1.2 horsepower, per m^2 <S> Let's take a typical hang glider: a Wills Wing Alpha 210 has 19 square metres of wing area. <S> That would give 17 kW, or 22.5 BHP. <S> In theory, that's more than enough to get a microlight into the air, if you can keep the weight of the battery, motor, and solar panels down. <S> In practice, though, are you really going to be flying at the equator, with your wings perfectly level, at midday? <S> And more importantly, are you really going to get a 17kW motor, 20 m^2 of solar panels, wires, and a battery (pretty much required) into the weight of a hang glider that weighs, itself, less than a typical person? <S> It's theoretically possible to make some kind of small ultralight type aircraft solar powered, but probably not until we find a way to make lighter motors and lighter solar panels that can take advantage of the wing area without causing weight/stability issues	One could conceivably create a solar-powered ultralight using flexible solar cells on the wing - in fact a little Googling reveals that it has apparently been done with an electric paramotor (a type of powered parachute)
Why shouldn't you use HF radio while refueling? FCOM limitations for many aircraft state: DO NOT USE HF RADIO WHILE REFUELING Why is this? I have heard from people that it's because most of the big airliners have a 'notch' antenna for HF; it's a small notch cut at the base of the vertical stabiliser. HF transmission power is fed to this notch and the whole fuselage acts as an antenna,radiating the power. Can someone explain in detail and in simple terms? <Q> The safest way to refuel an aircraft is with everything turned off and the airframe grounded (or bonded) to the fueling system. <S> This is often not practical (particularly for airliners), so a number of other rules exist to make refueling as safe as possible -- not using HF radio while refueling is one of them. <S> So why is the HF radio singled out? <S> Power , combined with the antenna design factors you mentioned. <S> With small radios you can easily light a fluorescent lightbulb <S> (incidentally this is why radio geeks are such great fun at parties). <S> HF antenna designs which use the aircraft itself to radiate part of the energy can further increase the chance of a spark. <A> Yes, at the free end of the HF antenna are voltages of several hundred to some kilovolts. <S> With hundred watts the HV can reach levels to start fluorescent lamps and that is also enough to spark into free air. <S> With some fuel dust it is like an electric detonator and TNT... <A> That power can cause sparks when it gets grounded through the fuel opening, that spark can ignite the tank. <S> (Ref: ratchet freak )	HF radios can put out several hundred watts of power - this makes them more likely to generate a spark that can jump the gap between say a refueling nozzle and the refueling port/tank, igniting fuel vapors and ruining everyone's day.
In an airliner, does the Captain or the First Officer fly the airplane? If there is such a thing as a 'normal' flight (in a commercial airliner), who flies the plane? Is it usually the Captain, the First Officer, or whomever needs the hours? <Q> At the commercial airline level, there is very little difference between a captain and a first officer, other than the amount of time that they have been at the company (seniority). <S> Typically, each of the two pilots takes turns flying the airplane. <S> For instance, if today's trip is from Miami to Charlotte to Chicago to Atlanta to Miami, the captain may fly from Miami to Charlotte, the first officer from Charlotte to Chicago, the captain from Chicago to Atlanta, and the first officer from Atlanta back to Miami. <S> These duty positions are independent of the captain/first officer designation. <S> The PF is responsible for physically flying the airplane (usually only during takeoff and landing) and for controlling the autopilot. <S> If the autopilot acts up, the PF immediately takes over. <A> As has been said in previous answers, the duties are divided between the PF and PNF, and the Captain and First Officer typically change which they will do each leg. <S> However, company policy may specify changes to this procedure. <S> For example, the first 747 carrier I worked for specified that approaches and landings to runway 13 at Kai Tek, the old Hong Kong airport, with it's supposed difficulties, were to be conducted by the Captain. <S> They also had a rule that first officers were not allowed to fly instrument approaches below certain minimums until they had accumulated a certain number of hours in the airplane. <S> The second 747 carrier I worked for had a rule against first officers taxing the airplane, this a result of some taxi problems they had had with first officers at the tiller. <S> In all instances, after I transitioned to the left seat at both of those carriers, I ignored those rules as I felt they were not only unnecessary but counter-productive. <S> In a few instances I had first officers decline to do these things when offered, but the vast majority were happy to take advantage of the opportunity. <A> Both pilots will log time for the flight, although their log entries will be slightly different. <S> The captain will log hours as Pilot-in-Command (PIC). <S> In practice, " George " (the autopilot) will probably actually fly the plane.	The duties in the cockpit are divided between the Pilot Flying (PF) and the Pilot Not Flying (PNF)/ Pilot Monitoring (PM).
Where are the microphones for the black box located in the cockpit? All modern commercial airliners have a CVR (Cockpit Voice Recorder) on-board to record what the pilots are saying during the duration for a flight. I feel that the location of the microphones is important because they should be in a place that can easily pick up the cockpit conversations but should also be discreet enough to avoid accidental damage or even intentional sabotage by hijackers/suicidal pilots. So where are the recording devices or microphones located in the cockpit for this? Moreover: Is there more than one microphone in the cockpit to provide stereo sound? If so, do investigators listen to the recording from each microphone? Are there any pictures of these microphones in the cockpit? <Q> The headsets worn by the pilots have a microphone arm. <S> These audio channels are split and routed to the black box. <S> The black box can support recording of up to 4 audio channels, so each channel can be examined separately. <S> Since the headsets and overhead microphone are inside the cockpit, stereo audio is available. <S> Can't find any pictures for you, sorry! <S> Seethis sources: Avstop FAA (pdf) <A> Each of the three crew gets its own array of mics including the hand mic, boom mic, mask mic, his speaker and headphones (the microphone he uses for radio communication and what he hears from the radio). <S> The third crew member's channel may be connected to the PA. <S> The fourth required channel is for the cockpit area mic which records general sounds and alerts. <S> Source: NTSB <A> The Cockpit Area Microphone (CAM) can be in a variety of places due to different cockpit designs. <S> Generally, it is supposed to be installed in the best position for recording voice communications. <S> On a Boeing 777, it is on the overhead panel next to the passenger seat belt sign switch: Image credit: Craig Murray / <S> Airliners.net <S> On an Airbus A318/A319/A320/A321, it is in between the windscreen and the overhead panel, just below the exterior lights switches: <S> Image credit: Niksa <S> Radicevic / Airliners.net	Additionally, there is at least one microphone embedded in the cockpit, usually overhead.
When might a pilot hand-fly a jet at cruise altitudes, and is it difficult? How difficult is it to hand-fly a jet at cruise altitudes? Other than autopilot failure and just doing it for the fun of it, when might you want to hand-fly at those altitudes? I suspect the answer to the first question varies with different aircraft. I have an answer for the 747-100 and -200 series below. <Q> For 747-100 and -200 aircraft at 35,000 ft and above, you can do it, but it's hard to keep the airplane within 100 feet of the assigned altitude, and you typically can't do that (or at least I couldn't) without practice. <S> 200 foot altitude excursions were the norm when I first took control if I had not done it for a while. <S> For the few first officers that accepted an invitation to try it, an initial 300 foot altitude excursion was typical when they first tried it, especially immediately after disengaging the autopilot. <S> I found the concentration required was very tiring. <S> Ten minutes was typically enough to satisfy the urge. <A> It's probably not a good idea to hand fly jets at cruise altitudes in many cases ( US , EU , and others). <S> The reason is that from FL290 to FL410 (29,000 to 41,000 feet standard pressure altitude), a lot of airspace is under RVSM rules (Reduced vertical separation minima). <S> This means that aircraft are only separated by 1000 feet vertically. <S> One of the requirements for flying in RVSM airspace is a system for automatically maintaining altitude. <S> If this system is not working, either the aircraft must fly at an altitude outside RVSM space (most likely below) or ATC must agree to provide 2000 foot separation above and below from other traffic. <S> Some examples of this in practice: Allowed to continue with increased separation Not allowed to continue, had to return to airport <S> Did not inform ATC in violation of rules <S> See the related question for more details: <S> Is it legal to fly in RVSM airspace with an inoperative autopilot? <A> Aerodynamic damping is proportional to density, so all maneuvers require less control input at altitude than near the ground. <S> On the downside, excursions from the trimmed condition produce greater amplitudes before stability pulls the aircraft back. <S> This explains why hand-flying needs more attention at high altitude. <S> Background: <S> Damping is the reaction of a system to movement, and positive damping means the reaction slows the movement down. <S> Case in point: The horizontal tail. <S> When the pitch attitude changes (say, by a vertical gust which changes lift first on the wing, then on the horizontal tail), the rotation of the aircraft around the Y axis (the one pointing sideways) creates an additional vertical speed on the horizontal tail surface. <S> This vertical speed is proportional to pitch speed (obviously) and the distance between c.g. and tail. <S> This speed changes the local angle of attack by the ratio between the vertical speed and flight speed. <S> Now we are at the core of it: A high flight speed will cause a smaller angle of attack change at the tail for the same pitch rate. <S> Since this angle of attack change creates the damping force (by creating lift on the tail which counteracts the pitch movement), a higher flight speed at the same dynamic pressure will lead to less damping. <S> This is a fancy way of saying that flying in lower density air makes the aircraft more responsive to disturbances.	Insofar as when you might want to do it, I found hand-flying produced a smoother ride in heavy to severe turbulence than the autopilot's turbulence mode, which tended to try to keep the assigned altitude and aircraft pitch too slavishly.
How do PAPI lights work? Usually, there are four lights at the sides of runways which show airplanes' altitude status: four red lights: too low two red, two white: appropriate altitude four white lights: too high. If two airplanes with two different altitudes approach, do they see different number of white and red lights? Or are the lights set for the closer airplane? <Q> Here's how the PAPI lights work: Depending on the angle of the viewer, a different color is seen: <S> Then each light is calibrated to an angle: <S> The good thing about this is that it's dead simple technology where very few things can go wrong: The lights have to be on and calibrated for the correct angle. <S> The downside is that its usefulness decreases with lower visibility. <S> Some new systems appear to have solar panels as an off grid (and alternative/backup) power source which is sensible. <S> Many systems today also have LED lights. <S> If two airplanes with two different altitudes approach, do they see different number of white and red lights? <S> Or are the lights set for the closer airplane? <S> The system is independent and passive , in the sense that it never makes contact or note of the aircraft approaching. <S> It lights up all to all aircraft in the beam. <S> Hence, it 'works' for all aircraft at the same time. <S> Some new systems feature FAROS <S> ( Final Approach Runway Occupancy Signal ) <S> giving an indication that the runway may be occupied by another aircraft by flashing the lights. <S> For a little information on differences between similar systems to PAPI, see this link . <A> They use a lens system that projects the light in a narrow beam so each plane sees something different and makes the glide slope indicators a passive system. <S> you can see this nicely on a foggy morning: <A> The lights you refer to are called PAPIs (Precision approach path indicators). <S> They to do not change colour based on the altitude of the plane but are rather passive light boxes that have a different colour depending on the angle that you look at them. <S> Each light is mounted at a slightly different angle. <S> If you are at the neutral axis of such a light you will see a blend of red and white. <A> For that reason, there can be an unlimited number of aircraft in view, and each will see the appropriate color selection.	The PAPI lights are not set for any airplane, they're unintelligent displays that are visible in different ways based on the angle of the viewer.
Why is the flight going north just to go south? I am tracking my kid's flight from LAX to EWR. It seems like a pretty straight West to East kind of flight but the flight path has the plane moving somewhat north through Ohio and then angling back to the south Why wouldn't the flight just keep going East? <Q> Aside from the storms causing an earlier re-routing, that jog north is to join the arrival into EWR. <S> A common fix in NE Ohio on flight plans into EWR is the DJB VOR which is in Loarine county (I think, somewhat near Cleveland). <S> and then routing over Slate Run and then Williamsport, PA on the way into Newark. <S> If you are a jet coming from the west, this is literally the only way into EWR. <S> The other two ways in are from the south joining somewhere on a line between Atlanta and Baltimore (which you can transition to from the west by going over Beckley, WV) or from the north coming in over Albany, NY. <S> The primary reason for the strict routing starting at around the OH/PA border is the need for multiple arrival descents for both jets and turboprops into the various NY area airports (EWR, JFK, LGA, TEB, etc), the westbound departures out of NY center and the letters of agreement between Cleveland and NY centers to manage these traffic flows. <S> See this image: <S> This represents a route of ..J29.DORET.J584.SLT.FQM3. <S> This is not the exact route a LAX originating flight would normally get as they would end up a bit further north (going over Detroit instead of Cleveland), but they would still converge on J584.SLT.FQM3 (the portion east of the OH/PA border). <S> No matter your position west of the OH/PA border, Cleveland center is going find a way to put you on J584 before you get very far into PA. <S> This is why the flight couldn't just go direct to EWR and had to first fly north. <A> Part of the answer is that, as noted in waiwai933's comment, the earth is (roughly) a sphere, not a flat plane. <S> This means that the shortest distance between two points is not a straight line on the map but what's called a great circle . <S> To find this, you'd take a circle whose centre is the centre of the earth and which passes through the two points you're trying to connect. <S> The shorter route along that circle is the great circle distance. <S> The intuitive reason for this is that the earth is "narrower" closer to the poles so you can gain a lot by flying towards the pole, using the "narrowness" and then flying away from the pole again. <S> The "ideal" route from LAX to EWR is this (images from gcmap.com ): <S> A much more pronounced version of this would be if your son was flying to Casablanca instead of Newark. <S> Although Los Angeles and Casablanca are at roughly the same latitude, the shortest route between them actually goes over Canada, over a thousand miles to the north of LA! <A> Actually, that flight was first routed South of its original flight path, in order to avoid a very large storm system in the mid-west. <S> At that point, it still could not head straight to Newark, due to another storm system in Indiana. <S> They were originally flying a little more East, but then got routed a 'smidge' North, to avoid the system, most likely when the system didn't move as fast as they figured. <S> As to why they kept heading North-East, instead of a more direct path from Indiana, I cannot tell. <S> If you (quickly) look at the flight on FlightAware.com , you can see the course corrections due to weather. <S> scratch the following, the TFR (temporary flight restriction) <S> isn't until later this week. <S> So they most likely were shunted farther North by ATC in order to avoid the TFR.	Another factor for this flight, was that it looks like once they went North to avoid the weather in Indiana, when they came east of the weather, if they'd have gone straight towards Newark at that time, there is a NOTAM for a TFR in Western Pennsylvania.
What is a flight leg and why it is so important for an aircraft? A flight leg is basically flight from one point to another point, (I'm not sure if flight leg number increase with touch and go around). I would like to know more about flight leg under what all conditions usually it increases and when it is reset. Also, most important why is it so important for an aircraft/airlines because usually it is 1 or 2 flight leg per travel. From what I know, flight leg is most important parameter in case of recording or storing data in NVM but I believe flight phase should be sufficient enough. <Q> I don't think flight leg is important for either aircraft no airline. <S> The reasons why most flights have one or two legs is purely economic. <S> Aircraft have to be operated with rather high load factor to be profitable. <S> If you have a line with less passengers, you really want to use smaller plane or run it less often. <S> Because different links have different demand, it's rather rare to have many consecutive links with similar demand so it would make sense to fly them with one plane as multi-leg flight. <S> And few people would want to fly the whole trip as the stop-overs take rather long. <S> For aircraft what matters is not legs, but <S> cycles , meaning pressurization cycles . <S> For pressurized aircraft the material fatigue is most closely related to the cycles and since each cycle also involves one period of running the engines at high thrust, the engine wear is also somewhat related. <S> It does not matter whether the aircraft accumulates 4 cycles in 4-leg journey or 4 separate journeys. <A> what is flight leg? <S> A flight leg is a trip of an aircraft, from take-off to landing. <S> Use of the term implies a multi-leg flight. <S> Each leg starts and ends at a different airport. <S> From the point of view of a passenger it is a part of a journey that may start or end with a stopover, a change of plane or a change of airline. <S> why is it important for an aircraft <S> It isn't really. <S> See Jan's answer regarding aircraft cycles . <A> With respect to avionics and fault logs, flight legs is just one more data point. <S> It's not any more important than any other piece of data, but it does have value. <S> Avionics are not structure and don't care as much about pressurization cycles, but it can be a factor - the pressure change between sea level and 8000 cabin altitude does have some effect. <S> It's just that avionics can easily count flight legs and it makes for an easy way to organize the fault logs along with flight phase. <S> It is useful data when trying to find the root cause of an intermittent fault in a piece of avionics. <S> Fault logs typically log at least 20 legs before they "roll over" and overwrite old data. <S> With some aircraft flying 6 or more legs a day, that ensures the plane can get to a base with maintenance before the fault gets overwritten. <S> The value is the ability to help detect patterns. <S> I've seen faults that only occur on the first leg of the day after the plane was parked overnight at a very humid airport. <S> Re-creating the conditions allowed us to duplicate the fault. <S> The problem was a flaw in the conformal coating (sealant) on a circuit card that allowed moisture to cause a short. <S> Once the unit had operated for an hour or so, the heat had dried it out and it worked fine.	It is obviously important administratively for scheduling and financially for optimizing return on investment etc. From the point of view of an aircraft's operator, it is a smaller part of an overall journey which involves landing at an intermediate airport.
Does the weight of the battery count as "fuel" in a battery powered ultralight? 14 CFR 103 compliant powered aircraft should be less than 254 pounds (excluding fuel). Do the batteries account for fuel in case of electric engine? <Q> The jury (i.e. FAA) is still out on this question as of early June 2014. <S> FAA has indicated it will not give a gasoline "fuel allowance" to be credited against weight for batteries. <S> Given that fuel weighs 6 lbs. <S> per gallon, or 30 lbs. <S> for the maximum legal gas an ultralight can carry, it would be a somewhat negligible, but certainly welcome, allowance for would-be electric manufacturers. <S> One company, Chip Erwin of AeroMarine, has imported a barebones ultralight motorglider based on the Goat towed ultralight glider. <S> It's called the Zigolo , and carries batteries enough for 30-40 mins. <S> of flight, without exceeding the 254-lb. <S> weight limit of the part 103 category. <S> In time the FAA may well decide to grant the allowance. <S> It's still not going to amount to much more time <S> , maybe 10 minutes given current battery energy density, which is a fraction of the energy density of gasoline, but research into electric storage is at a feverish pace worldwide. <S> Look for sport, then commercial electric aircraft, within the next 5 to 10 years. <S> Several electric single and two-seat electrics are already flying. <S> The Airbus ducted fan, recently ballyhooed as the first electric aircraft, which it certainly isn't, is a promising look at one way commercial electric applications might come to market. <A> No. <S> The FAA was approached about this in 2012 and responded that there was no allowance for battery weight. <S> All batteries must be included in the 254lb airframe weight. <S> https://rainbowaviation.company/wp-content/uploads/2017/08/elect-103-battry-def.pdf <S> September 4, 2012 <A> There seems to be consensus that built-in batteries count against the weight, but removable batteries might raise questions that are unanswered to date. <S> If it's not integral to the plane, it might be argued to fit the spirit of the rule.	Although batteries may indeed be used to provide power to an electric motor, the FAA does not agree that those batteries should be equated to usable fuel and excluded from an ultralight vehicle's empty weight.
How did aircraft communicate during early air travel? During the initial era of air travel how do the pilots/Navigation officers would communicate with ground stations? Do they use radio communication? Or Telegraph was used? <Q> Radio was not widely used until the 1930s, before that, mostly light signals were used. <S> Early ground support aircraft in WW I could drop little notes which were pencilled by the observer, stuffed in a small capsule to which a streamer was fitted, and that was dropped as closely as possible to the troops which should get that message. <S> This method was still used in WW II, when most aircraft had radio, because only specially equipped ground troops had compatible receivers. <S> The first regular flights by night were 1921 for the air mail connection between Omaha and Chicago, and electric flood lights were positioned along the flight path. <S> Communication the other way <S> (air to ground) was not possible on those flights. <S> The first air-to-ground radio communication used morse signals, and this is the origin for these strange three-letter names for things like local air pressure at the ground (QFE) or pressure corrected to sea level conditions (QNH). <S> There was a whole lot more of those, including some to order coffee before landing, but they are no longer necessary. <S> Read all about it here . <A> While radio was available (meaning it existed) it did not exist in a form usable by early aircraft. <S> If you are talking early-early travel, not commercial travel, communication was not necessary. <S> Navigate to the destination, circle the (farmer's) field to check for livestock, then land. <S> As things progressed, morse code became practical. <S> This was when cockpit crews required both hands to count. <A> Up until World War One, there was no radio communication between air and ground, or between planes. <S> Communication from ground to air was done by means of light signals. <S> From 1915 onwards aircraft were used as artillery spotters which involved Morse code wireless signals one-way , (from the aircraft to the ground). <S> There was no communication from ground to air, and the air-to-ground communication was limited to simple codes. <S> The only form of air-to-air communications was signals such as 'wing-waggling'. <S> Air-to-ground and air-to-air spoken radio communication became common between the wars, and was widespread in major air forces at the start of it. <A> Military aircraft frequently used radiotelegraphy (Morse code) well into WWII, if not 'til the end. <S> The binary nature of it (on/off constant amplitude signal) gave greater effective range and more resistance to degradation by static than radiotelephony (voice). <S> Most aircraft had voice radios for communication with nearby friendly aircraft and bases, but relied on Morse code at long ranges. <S> shades of digital transmissions today! <A> There was limited communication from ground to aircraft using the following three methods;Ground Strips. <S> Lamp Signals. <S> Poppet Panels. <S> The pilot had to fly and watch for signals at the same time. <S> Ground strips were white sheets 3 metres by 300 mm (10 feet by 1 foot) or larger. <S> They were laid out as patterns or letters with a letter for such messages as 'Your (wireless) signal is weak' or, 'Repeat last (wireless) message' or ' <S> I am not receiving your signal'.Lamp signals, used later in WW1, used 'Lucas' signalling lamps. <S> The operator aimed the light beam at the pilot when he thought it would be visible to him and send the message in Morse Code. <S> The Poppet Panel was a canvas shutter arrangement fixed to the ground and was worked by pulling a cord which made a white patch visible from the air. <S> When the cord was released the panel showed a black patch. <S> By pulling and releasing the cord the operator could send Morse Code messages to the pilot who had to fly with one hand, look over the side and write down the letters with his other hand. <S> It was a difficult task.	In World War 1 there were aircraft spark gap transmitters and the pilot could send messages in Morse code to receivers on the ground but he could not receive wireless (now called radio) signals. When Lufthansa opened the first night connection between the Reich and East Prussia in 1926, they posted burning oil drums along the way to mark where the pilot had to fly. Communication with other aircraft was not necessary as there usually were no other aircraft.
Why do the engineers need to be on board during testing? I just finished watching National Geographic's Megafactories: Boeing 747-8 . During the test flights, a bunch of engineers are on board the plane, presumably controlling the water tanks that distribute weight, and collecting the data. Another time I'd seen it was when they were testing detection systems for microbursts . There were about a dozen engineers sitting on the plane, watching monitors while the crew deliberately flew into hazardous conditions. Why do they risk the safety of these engineers, when presumably the work they're doing could be automated or controlled remotely? For data to be observed, couldn't they do that from the ground? Is this a case of "we've always done it this way?" Even now that we probably have the technology that would allow the engineers to avoid having to go on test flights, I'm guessing that changing this procedure would be a lengthy and difficult process. Besides the pilots, why does anyone else need to be on board? <Q> More and more data is collected in flight testing of aircraft. <S> While 50 years ago they might have only designed for a small number of scenarios, the advances in computing allow them to design modern aircraft for thousands of scenarios. <S> Modern certification standards include more and more requirements, which include flight testing for many of these requirements. <S> While some information is sent to the ground (like in this video ), other information may not be. <S> Airplanes in flight test have sensors for temperature, pressure, stress, and many other parameters located throughout the plane. <S> These generate a lot of data, more than may be practical to send on a live data link. <S> There may be several reasons that the engineers would want to analyze a lot of information onboard. <S> Some of the tests need to have multiple parameters coordinated with the pilots. <S> If they are flight testing stall, for instance, they need to be sure they have <S> flight parameters are correct for that test. <S> The engineers also verify that the the information they collect is sufficient for the needs of the test. <S> It's much more expensive to come back and realize they didn't get what they needed and must go back up to re-run the test. <S> Some of the data is also critical for safety. <S> One subject of the tests is flutter. <S> Flutter conditions can be very dangerous to the aircraft . <S> If a data link were to be interrupted in a case like this, safety could be compromised. <A> In a perfect world, you wouldn't need the pilots as well... To your question: <S> No modern instrument can currently match the feeling of "just being there". <S> Data recorded on the plane and transmitted to the tower is lagging or even impossible to collect live (due to technical difficulties). <S> Flying takes a lot of attention from the pilot. <S> Even if they're good engineers (besides being a pilot), you wouldn't want to waste an experiment. <S> Engineers don't go to preliminary (dangerous) flight test. <S> Some engineers enjoy being on board the machine they designed. <A> Usually, engineers on board on the aircraft serve the same purpose as engineers in a control room. <S> (The control room for space missions in Houston is probably the best, most widely known example of a control room.) <S> Having the engineers on board reduces the need to send the data to the ground via telemetry (TM), which may be a necessity based on limited bandwith, etc. <S> A description and illustration of the control room and its purpose appear here . <S> It also allows for better coordination amongst the crew, as the pilots, who need information that the engineers are monitoring, can discuss more effectively with the engineers when they are on intercom. <S> Flight Test Enginners (FTEs) are another kind of engineer on board the aircraft, and they specialize in test conduct. <S> They are present to guide the test pilot, assist in determining if the maneuver was flown correctly, evaluate data quality, and make decisions about whether to continue testing.	The engineers give the pilots guidance on getting the airplane into the right configuration. The engineers help monitor the data and make sure that things don't get out of hand.
How do airplanes get stacked in a holding pattern? This question prompted me to wonder how it works at a major airport. Let's say four airliners all are scheduled to arrive within a few minutes of each other to a major airport, perhaps from the four cardinal directions. Things are already backed up at the airport, let's say landings are (temporarily) restricted due to an emergency landing. Can you describe how ATC might direct the four flights and what they would do themselves? <Q> ATC has many tools "in their belt" to keep traffic separated. <S> When things back up, it can get crowded. <S> Emergencies and weather regularly cause disruptions and ATC handles them according to the circumstances. <S> To illustrate some possibilities, I will use Seattle as an example here. <S> You can find the airport information here . <S> Most aircraft coming into the area will be commercial flights on IFR flight plans, and they will follow a Standard Terminal Arrival (STAR) into Seattle. <S> You can find this seciton towards the bottom of the AirNav page. <S> There are different STARs depending on the direction from which the flight is arriving. <S> Each STAR will include published holding patterns. <S> Listed here is the direction of arrival, the name of the STAR, and the holding fixes: <S> East - EPHRATA - FLAAK, EPHRATA, ODESS East - GLASR - LOSTT, TEMPL, JAKSN Southeast - CHINS - SUNED, BRUKK South - OLYMPIA - BTG, OLYMPIA Southwest - HAWKZ - BTG, HAWKZ Northwest - JAWBN - JAWBN <S> Northwest - MARNR - MARNR <S> As you can see, there are 11 different holding fixes across the seven STARs. <S> If you have one aircraft from each direction, they can each hold at the fix according to their STAR. <S> The busiest STARs have multiple holding fixes that may be used. <S> Aircraft may also be stacked on the same hold at different altitudes. <S> You can read some FAA information about holds here . <S> Aircraft may also choose to divert. <S> Depending on how much fuel they have and how the weather/emergency is playing out, they may not want to hold indefinitely on the GLASR arrival at LOSTT. <S> Generally ATC will not ask for a diversion unless absolutely necessary. <S> Among others, Portland, Vancouver, and Spokane are all fairly close to where the aircraft may be holding and could be viable alternates. <A> As @fooot mentions, most, if not all, holding will take place at fixes along the arrival, not within the terminal airspace. <S> Once airplanes are being controlled by an approach facility they will resolve spacing issues with vectors. <S> Altitude changes within this airspace can be difficult (see: NY Tracon) and <S> the airspace requirements for holding make it quite inefficient. <S> Once approach runs out of room to properly sequence with vectors, they'll use their landlines to call the controller at the center feeding the arrivals and tell them "We're closed -- update at 2130Z". <S> The center will then start the holds. <S> Aircraft that are closest to being handed off will be assigned the holding at the closest fixes to the destination. <S> This usually means holding at low altitudes (E.g. holding over Yardley at 8000 ft inbound to EWR). <S> Aircraft further back will either get a hold close to them, or they'll continue the arrival and hold toward the end. <S> These decisions are based on airspace availability and how long the anticipated holding will be. <S> Where center has altitude blocks available, they'll stack aircraft at that fix. <S> I've been in holding at FL240 where I have seen 10-12 airplanes below me and a few above me, all flying the same racetrack spaced 1000' vertically. <S> If delays become long, aircraft will begin to divert to their alternates, refuel and then wait under a ground stop or ground delay to get back in the air to their final destination. <A> First come first serve. <S> Typically ATC will direct the first plane to the lowest free altitude in the holding pattern and the next 1000 ft on top of that and so on. <S> It may be possible that a plane comes in at a lower altitude right after a plane at a higher one and gets to skip to a lower spot (so it doesn't need to climb up). <S> When the runway/next segment is available ATC will clear the lowest plane to continue/land and then shift the entire stack down.	When arrivals resume ATC will peel airplanes off the bottom of the hold, one at at time at intervals dependent on the spacing requested by the approach facility.
Can I use a 150mw green laser to scare pigeons and not interfere with air traffic? Pigeons are annoying since they make aggressive cooing noises near my house. Considering many options for their dispersal, it seems lasers are one options since for some reason the lasers drive the pigeons crazy. In one video pigeons are completely dispersed by a 150mw green laser, making it appear to be an attractive option for dispersing my pigeon problem. However I am concerned that maybe the lasers will continue into the atmosphere past the pigeons, and will affect air traffic....Obviously this is not worth the benefit of dispersing pigeons. Is this totally out of the question? Are there any rules of thumb one should follow here to be on the safe side to not affect aircraft? <Q> There are cases where you can use a laser pointer safely, such as pointing out constellations in a dark field far from any air traffic, but as a general rule of thumb lasers should not be pointed skyward - not even to get rid of irritating sky rats pigeons. <S> Should you wind up illuminating an aircraft with your laser <S> you can cause serious problems for the crew - inadvertent or not it could get you a visit from some very unhappy law enforcement officials. <S> Your local Animal Control group may be able to offer some additional ideas. <S> (Avoid the "predator bird statue" idea - in my experience pigeons <S> realize it's fake and use it as a toilet.) <A> I use a marshmallow gun to scare away squirrels and grackles from my bird feeder. <S> The mini marshmallows are biodegradable (and yummy) and the gun's pop when it shoots is enough to get the critters running. <S> In the uncommon event of actually hitting them, no permanent damage is done. <S> And in response to your question, I think you might end up blinding the pigeons and building up bad pigeon karma. <A> This kind of laser is class 3B laser. <S> You may not be allowed to possess it. <S> Even if you are, this laser come with serious technical restriction such as deactivation if you point it upward.	There are many other ways to get rid of pigeons , some of which are used at airports and many of which are more effective (and safer) than your laser idea.
What aircraft has the highest suggested landing speed? Just out of vague curiosity, what aircraft has the highest recommended landing speed for an earth bound (atmospheric) craft? And, btw, when I say "landing" I define it as thus: Controlled Powered (though if you want to note unpowered, feel free) Safe, with the vehicle/aircraft fully recoverable On a runway On wheels or skids I know there may be multiple answers, even with my trying to narrow it down, so feel free to list a few different scenarios. I'm mostly wondering about planes that are in common usage though, both military and civilian (past and present)... I'd have to think something like the SR-71 or MIG-25 would be very close to the top of the list, if not the top. <Q> Based on its fixed-wing hypersonic design and inordinately high wing loading, I would predict that the X-15 has the highest recommend landing speed of any earthbound aircraft, with a preliminary search seemingly bearing this hypothesis out. <S> But if unofficial sources are to be believed, its actual landing speed was much higher, closer to 390kph=208kts (although these numbers are admittedly more dubious): <S> “According to an early edition of 'the Guinness book of world records' the X15 also holds the record for fastest landing speed at 242 mph compared with 210 mph for the space shuttle.” <S> http://area51specialprojects.com/x15.html <S> If only powered aircraft are open to consideration, then the F-104 Starfighter would have to be up there as well. <S> It needed a blown-flap flow control system just to be sane during landing... <S> “To make landing speeds “reasonable,” The F-104 forced engine air through the wings to smooth the airflow and give more lift. <S> With bleed air, the Zipper could land at the challenging but not extreme speed of 160 to 165 knots. <S> If the air-bleed system was not working, landing speeds climbed to 240 knots.” <S> http://www.pacificaviationmuseum.org/pearl-harbor-blog/lockheed-f-104-starfighter <S> So, if mechanical failure scenarios are deemed admissible, then the F-104 without its crucial boundary layer control systems would be the clear winner for powered landing speed, weighing in at an absolutely terrifying 240 kts. <S> Otherwise, it would appear that the X-15 (unofficially) reigns supreme. <A> More high speed lawndarts: Presenting the F-102A Delta Dagger. <S> http://www.amazon.com/Convair-Dagger-Pilots-Flight-Operating/dp/1430310464 lists final approach speeds as high as 185 KIAS, with touchdown speed of 145 KIAS for the same fuel load. <S> And the B-58 Hustler <S> http://www.aviation-history.com/convair/b58.html says it had a touchdown speed of 165 KIAS. <S> Which would lead to an approach speed even higher than that of the F-102. <S> http://wikimapia.org/7029449/Important-B-58-landing-approach-aid <S> says it landed at "just under 200 knots", even higher then unless they mean approach speed rather than touchdown speed. <S> The XB-70 http://www.nasa.gov/centers/dryden/pdf/87774main_H-587.pdf mentions an approach speed of 200-210KIAS, with touchdown at 175-185KIAS. <S> And that for a lightly loaded prototype, the production machines would have been heavier... <S> So that may well be the top candidate for the job (excluding non-normal operations), if we exclude the X-15 and Space Shuttle which were gliders during their landing phase. <A> Concorde's landing speed was 300 km/h . <S> Its high speed was due to its small wings, designed for supercruise, which required higher airspeeds to maintain lift during the approach. <S> Possibly the XB-70 Valkyrie, being also a large supersonic aircraft, would have had higher landing speeds, but I can't find a reference for its landing speed. <S> The Space Shuttle regularly landed at 350-400 km/h under control, though without power. <A> The CF-101 Voodoo had a landing speed of 175 kts plus fuel weight over 3000 lbs over which it was 5 kts per 1000 lbs of fuel. <S> BTW crash landed one at 195 kts in Feb 82. <A> The USAF 101-B (ADC)did fly final approach at 175 plus fuel... <S> it also had a 300 foot altimeter error subsonic at most landing altitudes! <S> This was an all-weather interceptor! <S> I will never forget landing at Kingsley fold, Klamath Falls, OR,at night, in a rain storm wth my rain clearing system inop!	According to an ostensibly legitimate NASA source (link below), the X-15's normal landing speed was 200+mph (173.8kts=321.9kph), http://www.nasa.gov/centers/armstrong/news/FactSheets/FS-052-DFRC.html
Single engine failure in a light twin after lift-off: what to do? In a previous question the case about if a turnback would be feasible, specifically for a single engine aircraft, has been analysed. But given a twin-engine general aviation aircraft and a single engine failure immediately after lift-off, considering that my Pilot handbook says: A continued take-off is not recommended if the steady rate of climb according to "Section XX" is less than Y%. Considering the quite dangerous setting, I would say that is quite impractical to go and check that table in such a situation. What kind of indicators might I look for to check if it safe to continue? Should I learn by heart such table? (I am not sure this is practical either, is a quite complex table) In case I am unsure what to do, apart from trying to climb for a while then turn around or immediately try land in front of me (granted that there is enough space), are there, generally speaking, other options? In the accepted answer of the listed question is said that It's not reasonable to try it [a turnaround] without knowing what altitude is needed for it at current conditions. is it possible to estimate this quickly inside the cockpit? <Q> What you really should learn by heart is the flight speed for best climb with one engine inoperative. <S> Try to trim that immediately and you will win more time to make a decision. <S> The rest is really depending on circumstances: Is there a landing opportunity ahead? <S> Are you high enough to do a 180 and land on the same runway in opposite direction? <S> Or are you high enough (and the aircraft does not lose altitude) that you can fly a pattern and land normally? <A> After you've learned your airplane and its characteristics, you will know if something is not right. <S> The decision to land, when that's something that can be safely done, is never the wrong one if you're not comfortable with your performance and problems can be checked out on the ground with nobody dying usually! <S> Regarding a safe altitude to turn around in... <S> you need to know your aircraft to answer this, but it's not terribly difficult to learn. <S> You can fly to a few thousand feet AGL (preferably with a CFI or other capable safety pilot), fly at whatever speed you climb at, pull your throttle out and see how much altitude you lose while doing a 180 degree turn (simulating turning back to your departure runway). <S> Try this under different conditions (max gross weight vs. <S> generally empty; high density altitude vs low for example) to learn how these factors affect your altitude loss. <S> Then apply a safety margin. <S> I've been taught that a general figure (without recognition of the specific aircraft or conditions) is 500 feet. <S> This is not to say a turn-around is safe at 500 feet! <S> It's just a baseline of consideration. <S> Other factors are going to include how much runway you're going to have if you're able to turn around! <S> One of my primary instructors, before every first launch of the day, had me go through an aborted landing briefing similar to: <S> if we have an emergency below 500 feet we're going to land straight ahead. <S> Below 700 feet, we're going to turn to the (left/right) and land on the crossing runway (my airport had 9/27 and 5/23). <S> Higher and we will turn left/right and land on the parallel runway (9/27 R/L; <S> easier to get to than a full 180 in-place). <A> You are more likely to kill yourself in a stall/spin trying to turn back than you are from a forced landing straight ahead. <S> Since the altitude required to make a successful 180 turn is quite considerable the chances are if you are high enough you will be too far from the runway to make it back. <S> I remember seeing an article in plane and pilot magazine back in 1974 dealing with that topic <S> and I seem to recall anything below 780ft AGL <S> was a no-go	Testing the aircraft at altitude with one engine throttled is highly recommended, but be aware that the remaining thrust / drag of the throttled engine might be different from that of the stopped engine.
How do you repair a grounded aircraft at a remote location? If a large passenger airliner needs repair at a remote airport without services, are there "flying repairshops" that can swoop in and do the work on site? <Q> If you can, you'll fly in maintance yourself to get it fixed, perhaps by chartering a cargo plane on the way. <S> If you can land the aircraft, you can probably get any spare part in through the same runway, with varying degrees of difficulty. <S> If it's bad, Boeing has an Aircraft On Ground team who should be able to fix pretty serious damage. <S> Often, it may just be patched up until it's good enough to fly to get it to a place with better facilities. <A> From memory, the protocol to be observed includes: <S> The Captain must do the flying. <S> Only the cockpit crew can be aboard. <S> The fan must be tied down to prevent it's rotation in flight. <S> A specific takeoff procedure is to be followed. <S> At the two 747 carriers I worked for, we usually did a 3-engine takeoff in the sim on our 6-month checks. <S> I did two of them for real, and it's no big deal. <A> No airport capable of handling widebodies will have no services at all, but of course many places lack a full maintenance shop. <S> As mentioned elsewhere, Boeing has a go team that can get most repairable damage brought back to flyable condition. <S> "Flyable" does not necessarily mean "normal, scheduled service" - it means able to leave the remote field and limp back to a facility able to do the proper work. <S> This could easily be Seattle or Hamburg from Johannesburg. <S> If you want to reposition an aircraft for maintenance you can have a LOT of stuff <S> broken - basically if the engineers say they'll ride in it, and you avoid overflying large cities, you're good. <S> Several large aircraft have an option to carry an extra engine on the wing to a remote grounded aircraft - expensive, but cheaper than cargo (it can be on a scheduled revenue flight). <S> Put a couple of mechanics on board and the job's done in a day or two. <S> The bad engine comes back the same way. <A> That would depend on the damage that needs to be repaired. <S> Some repairs (like replacing an engine) can be done on site. <S> For more serious damage that can't be fixed on site they will make a quick patch and then fly the aircraft to a facility capable of properly doing the repairs while taking care to not aggravate the existing problem.	If the problem is a bad engine and the aircraft is a 747, the most cost effect solution is usually a 3-engine ferry to a repair station.
Why do (almost) all military transports have high wings and civilian transports low wings? I've observed that almost all military transports have high wings (with a pronounced anhedral) and almost all civilian airliners have low wings (with a pronounced dihedral) — why is this? The high-wing configuration gives the military the advantage of easier loading and unloading (especially when operating from irregular airfields), and lower overall height for the aircraft, but then why do civilian aeroplanes hate this design? Except in the erstwhile USSR, I haven't really seen high-winged military aircraft being used as civilian airliners (Boeing 737 size and beyond), though I can't think of any reasons why not. <Q> For military transport aircraft: Wings further off the ground will mean that the engines will also be further off the ground, reducing the risk of foreign object damage. <S> You can move vehicles under the wing, and taxi across smaller taxiways. <S> The fuselage can be closer to ground, facilitating transport. <S> No wing spar crossing the cargo floor. <S> Reasons why most commercial transport jets don't have it: Many are converted passenger jets. <S> They are mainly pallet loaded, less vehicles and bulky objects. <S> They normally use prepared airports, which military jets cannot assume they will. <S> They often loaded from a side door, and it makes little difference I think if you go up one meter or three meters. <S> but then why do civilian aeroplanes hate this design? <S> Airlines don't 'hate' this design, look at the BAe146 Quiet Trader for instance. <S> It's just not that many commercial aircraft from which cargo jets are derived are built this way. <S> Except in the erstwhile USSR, I haven't really seen high-winged military aircraft being used as civilian airliners (Boeing 737 size and beyond), though I can't think of any reasons why not. <S> Military jets are very expensive to operate and the east block Antonov 124 probably satisfy the most demand. <S> There are a few commercial C130 (L100) around though. <S> It's also not like the US airforce will give us C-5 Galaxy to a commercial company to do whatever it wants with it. <A> There are probably two main factors that come into play with the placement of the wing: Height of fuselage from ground Especially for military airlifts, the ability to load cargo is extremely important. <S> This means that the fuselage should be as close to the ground as possible to allow roll-on/roll-off of cargo with built-in ramps. <S> Placing the wings on top of the fuselage allows the bottom of the fuselage to be closer to the ground. <S> This is less of a problem for airlines. <S> Commercial cargo can usually count on ground equipment for loading and unloading cargo containers on aircraft. <S> Ease of maintenance Since airliners don't need easy access to the fuselage to load cargo, maintenance should be as simple as possible. <S> Especialy with the larger aircraft like the C-5, a high-wing puts the engines and wings far above the ground. <S> This makes it much more difficult to work on these components. <S> Keeping the wings and engines low to the ground makes it much easier to replace an engine or access the wings, such as for refueling. <S> The military wants planes to be easy to maintain as well, but they are willing to make some tradeoffs for the better cargo loading configuration. <S> There are of course many other tradeoffs in areas like structure and stability. <S> However, it's clear that both configurations are perfectly feasible. <S> The most important factors come down to the usability of the design. <A> Low wings are favored for civil aviation because this puts the passenger cabin on top of the wing. <S> Damage from non-normal landings (gear up, no runway, missed the runway, etc.) will happen to the wing, first. <S> Thus protecting passengers. <S> Fuel tanks are usually in the wing and having them also underneath is considered good for the same reason. <S> A low wing allows engines to be near the ground for easy servicing. <S> And main gear legs fit conveniently into low-wing structures. <S> The legs are tidy and short with low wings. <S> High wings are favored for military cargo and passenger planes because the high wing keeps the engine, propeller, fan, etc, away from the ground. <S> Military cargo and passenger planes don't always have paved runways- <S> a flatish spot may be as good as they get. <S> High wings make landing gear design more difficult, they're either taller, or stick out from the fuselage and are narrow, maybe mounted in pods on the sides of the fuselage, with extra weight and drag. <S> High wings require strong structure to keep them from crushing the passenger space, in a crash, which is extra weight and complexity. <S> High wings make fuel tank access and engine access difficult. <S> Meaning it can take off again, after each landing. <S> Dihedral provides stability to low wing airplanes by giving negative feedback to stabilize straight and level flight. <S> Anhedral reduces stability, allowing a high winged airplane to be maneuvered more easily, but doesn't enhance straight and level stability.	But high wings protect the engines, and that allows high wing airplanes to operate in rough conditions. They need to be able to load large objects and vehicles, and with little or no ground support available.
What are the steep ramps often erected at large airports? For example, the following white and orange striped ramp: I've seen these at a couple large airports but I've never seen them actually used for anything. <Q> Here in the United States these are called blast fences. <A> Apart from blast fences, they also serve as wind breaks and to deflect engine noise away from the area behind them. <S> And of course they can (and the one you showed looks <S> like it might be) intended to be a visible marker of a closed taxiway or runway. <A> If you've ever watched an aircraft carrier launch a plane, you'll see such a barrier pop up (on hinges) <S> right behind the jet exhaust to deflect it upward and away from other aircraft and deck crew behind the launch catapult. <S> These things (picture above) look pretty heavy, so they won't be blown over easily. <S> I doubt they would use them to mark a closed runway, unless it's quite long term, as they would be difficult to move around. <S> Does anyone know if they are in fact lightweight, and attach to the runway in some manner? <A> The following is speculation, as I have no specific knowledge on the matter, but searching a bit it seems that they are needed for deflecting upwards the engine blast http://www.bdi.aero/ <S> Also, it seems from that website that they also provide a minimum of noise abatement.	They protect whatever may be behind them from the direct effects of jet blast by directing the blast upwards.
Is LPV considered a precision approach? WAAS LPV approaches can have decision altitudes as low as 200 AGL, the same as many Cat I ILS approaches. Previous opinions on the Internet have quoted the FAA as saying LPV is considered a non-precision approach, but many of these entries were made more than seven years ago, when the technology was much less mature. Does anyone know if this is still the FAA's position, and are there any RECENT references to their position? <Q> These types of approaches are differentiated from 'Precision' approaches (ILS, PAR, etc.) in the FAA AIM (Section 5-4-5, Paragraph 7): (b) Approach with Vertical Guidance (APV). <S> An instrument approach based on a navigation system that is not required to meet the precision approach standards of ICAO Annex 10 but provides course and glidepath deviation information. <S> For example, Baro−VNAV, LDA with glidepath, LNAV/VNAV and LPV are APV approaches. <A> From the Helicopter ATP PTS (Didn't look at FW): C. TASK: <S> PRECISION INSTRUMENT APPROACHESREFERENCES: <S> Part 61; AC 61-27; Pilot's Operating Handbook, RFM, AIM; Instrument Approach Procedure Charts. <S> NOTE: <S> Two precision approaches must be accomplished in actual or simulated instrument conditions. <S> NOTE: <S> If the installed equipment and data base is current and qualified for IFR flight and LPV approaches, an LPV approach can be flown to demonstrate precision approach proficiency if the LPV DA is equal to or less than 300 feet HAT. <A> The question has become redundant. <S> ICAO never did like the term ‘APV’ (which as defined logically ought to have included ILS but didn’t) or ‘non-precision’. <S> As of now, in UK at least, it’s correct to refer only to two operational approach methods, 3D - of varying precision, from ILS CAT IIIB to LNAV/VNAV with RNP0.3 to ‘overlay’ NDB - and 2D approaches where vertical guidance isn’t presented to the pilot. <A> An LPV approach is in a category by itself. <S> IAW the AIM <S> it is considered an APV or approach with vertical guidance. <S> It "may" not meet the requirements of ICAO 10 precision approach requirements, but does in fact have a Decision Altitude.	LPV, LNAV/VNAV, and Baro VNAV are considered to be an 'Approach with Vertical Guidance (APV)'.
What are good books to learn basic aerodynamics in plane design? Well, since this stack is in beta, I thought I'd take a wack at asking a book question to see how it fits in this particular community (of if it even fits to begin with). I'm very curious about how aerodynamics work in plane design (especially wing design), but it's hard for me to ask questions here because I'm lack knowledge of so many of the basics. So I wondered if I could get a recommendation on a good book to learn the basics of aerodynamics? Keeping in mind that my understanding of math is limited, so I would need a book that explains the math being used to some extent. Bear in mind when answering: This is a Q&A site, so try and have some reasoning behind why your book is the best. Especially if you could show it has good explanations of the math and, also, the books is good for the somewhat beginner. Let's see if this works... <Q> Beginner Fundamentals of Aerodynamics by John D. Anderson, <S> Jr. Introduces the basics of aerodynamics with historical background, the mathematical explanation and some practical applications. <S> In the latest edition, Computational Fluid Dynamics is also discussed. <S> Mechanics Of Flight by Warren F. Phillips. <S> Anderson's book is a good text for understanding the building blocks of fluid dynamics, such as the different types of flow. <S> It is good for understanding how airfoils and wings work, as well as understanding the microscopic flow considerations. <S> Phillips' text also talks plenty about flight dynamics and control, so you can better picture the forces acting on an airplane. <S> Anderson's and Phillips' make a very good learning pack. <S> Intermediate <S> No books found as of yet <S> I wouldn't consider these to be great "learning" textbooks, and the math can get very intensive at times, but <S> these are still go-to reference text, and they are a great resource if you want to start a "deep dive" into aerodynamics and the practical effects of various design decisions. <S> Both books are replete with wind-tunnel testing information and diagrams, as well as the supporting equations to back it all up. <S> Classics / Older Aerodynamics for Naval Aviators by H. H. Hurt Jr. <S> This is a good primer on basic aerodynamics - as the title implies it's primarily aimed at naval aviators, but the material is pretty accessible and much of it is applicable to all fixed-wing aviation. <S> There's even some helicopter stuff in there, though the section is rather thin. <S> This book is available from a number of publishers. <S> It is also known as NAVAIR 00-80T-80 or NAVWEPS <S> 00-80T-80 and available from the FAA in PDF form. <S> Additional references <S> As far as mathematics goes, you can get Stewart's Calculus text. <S> It is a pretty good book with quite satisfactory explanations, and you can get an older edition for almost nothing (make sure you get the full text with both single variable calculus and multivariable calculus sections). <S> Without a basic understanding of calculus it will be difficult for you to get a good grasp of the aerodynamics material. <A> I'm with DeltaLima's book recommendation [pdf]. <S> Otherwise, this chapter of a larger ebook covers some basic aerodynamics: http://www.av8n.com/how/htm/airfoils.html <A> Nobody mentioned the FAA handbooks yet, so I will. <S> The FAA has a cornucopia of handbooks on various aviation-related topics, and in particular has a few on aerodynamics. <S> They have the advantage of being easy to find, written to be understandable by anyone, and available free of charge. <S> Here are a few In particular, I would recommend reading aerodynamics of flight . <S> It was written for student private pilots, so everything discussed pertains to aviation, and it does not assume that the reader has more that a high school education. <S> There are other books, that are aimed at the same public, but that expose the aerodynamics of helicopters or of gliders , though the contents of these books partially overlap, of course. <S> Finally, <S> this manual is a bit outdated, but the first section features a useful glossary of aero terms. <A> I don't know a book which will provide you with a thorough mathematical explanation and at the same time treat the aerodynamic content in depth. <S> Perhaps one exists, but I have not come across it as yet. <S> There are plenty of books which can serve this purpose. <S> Anderson's book, meanwhile, presents the material in a manner which is quite easy to understand, and build a strong foundation of aerodynamics and its applications. <S> However, if you feel reading a mathematics book might take away a significant quantity of your time, another book I would recommend is Flight Without Formulae by A.C.Kermode. <S> It is a classic book on aeronautical engineering, and covers the various aerodynamic phenomena over a wing. <S> In my view, it is quite apt for a beginner. <A> A famous reference is: 'Aerodynamics, selected topics on the light of their historical development', by Theodore von Karman. <S> There's also a site: Desktop. <S> Aero offering a digital textbook on applied aerodynamics, but as I'm not engineer, I never went beyond cover page. <S> NASA/ <S> NACA Cranfield database contain lots of aviation related papers since very early, a link to a list exists in Rotaryeng.net site: <S> NACA UK Archive results page	I would recommend that you you can go for a book like Fundamentals of Aerodynamics by John D. Anderson, Jr., and simultaneously refer to a mathematics book which will give you the necessary background knowledge. Advanced Fluid Dynamic Lift & Fluid Dynamic Drag both by Hoerner
What is the difference between being instructed to land "as soon as possible" or "at nearest suitable airport"? On commercial airliners, the FCOM (Flight Crew Operating Manual) sometimes gives instructions to the pilots to land sooner than planned, following various in-flight failures or emergencies. For instance, for serious emergencies (e.g. in-flight fire), the pilots would be instructed to LAND ASAP (as soon as possible), as there is a real danger to the aircraft and its occupants if they stay in the air any longer. For less severe situations, the pilots would be instructed to LAND ANSA (at nearest suitable airport), which gives them more leeway in deciding where to land. My question is: other than the fact that LAND ASAP is obviously more urgent than LAND ANSA , could anyone go into more details as to how a pilot would interpret these instructions, and how they differ? (for instance, does LAND ASAP mean "land on the nearest reasonably smooth surface", or is it less extreme than that? Are there guidelines on approximately how long you should keep flying after receiving a LAND ANSA instruction?) <Q> I would interpret them as: <S> ASAP means the plane is going to kill you. <S> Soon. <S> So land before that happens. <S> Short runways, military airports, abandoned airfields, a decent highway, dry lakes (e.g. Edwards AFB), calm bodies of water (e.g. the Hudson River) are all possibilities. <S> Do not concern yourself with operational issues like taking off again, and bureaucratic formalities like immigration will be summarily ignored. <S> Obviously if you are near the Hudson you would try very, very hard to reach JFK, Teterboro or Newark, but sometimes that doesn't work out. <S> ANSA means try for a real airport considering immediate operational and bureaucratic requirements, but not beyond immediate. <S> this could include turning around and landing at Goose Bay. <S> Basically I'm going to punch "Nearest" on the Nav panel and make an educated choice. <S> Most Nav sets will only show open airfields that can accommodate your aircraft. <S> For example, Gimli would not have appeared for Air Canada flight 143 , assuming they had a suitable unit back then and the power hadn't gone out. <S> The terms are deliberately unclear to give the pilot some flexibility - you can't predict and write a procedure for everything. <A> LAND IMMEDIATELY <S> Continued Flight may be more hazardous than Ditching or Forced Landing <S> Landing airfield and duration of flight are at the discretion of the pilot. <S> Extended flight beyond approved landing airport is not recommended <A> Engine fire is land immediately. <S> Land immediately (e.g. Engine FIRE - <S> > land where you can) <S> Land as soon as possible and land at the nearest airport is the same (e.g. PFD fails but MFD and standby instrument is still working - <S> > <S> Pilot is able to continue flying but the safety margin is reduced) <S> Land as soon as practicable <S> (e.g. Loss of vertical airspeed on the Standby instrument - <S> > Pilot uses primary displays and vertical airspeed is not a critical parameter. <S> This is a Minor failure condition which does not significantly reduce aircraft safety. <S> Flight crew will decide if the failure does involve actions within their capabilities and if change in flight plan/mission is needed.	LASAP Land as soon as possible at which a safe landing can be made or is assured ANSA Land at nearest suitable approved airport Land as soon as Practical Extended flight not recommended.
Is a single-engine ferry flight allowed with a twin-engine plane? If a twin-engine aircraft has an engine problem and could fly somewhere for maintenance, is a single-engine ferry flight ever allowed? If so, do airlines or pilots ever decide to do this? <Q> Civilian aircraft are not designed for this - but some military aircraft are. <S> The Antonov-70 can easily take off with one engine inoperational (it has four in total), but it has a limited capability to take off with two engines out on the same side! <S> For that, it has to be empty and can carry only minimum fuel. <S> This capability is the consequence of the demand of the Soviet Air Force for the An-70 to operate for 6 months with minimum maintenance. <S> The Antonov design bureau, well aware of the limited capabilities of front-line troops in aircraft maintenance, designed this transporter with lots of redundancy. <S> I would expect there is a way to do it, but it needs the agreement of the owner and some paperwork with the local authorities. <S> If you can prove that this particular ferry flight is safe, I think you would be allowed to fly. <S> But I am certain that without lengthy preparation and paperwork there is no way to legally take off on one engine only. <S> This is in contrast to military aviation where this kind of operation is planned for. <A> I can find no evidence of the FAA or any other authority ever issuing such a permit. <S> It has happened, though (without a permit). <S> An SN-601 tried to take off from Portland with one engine. <S> Unsuccessfully. <S> Luckily no one was hurt. <S> There's also a lengthy thread about it on airliners.net , in which there are several undocumented, anecdotal stories about this being done successfully (and illegally), e.g. in a P-38 and either a Convair 240 or 600 . <S> There are some good technical reasons why this is unlikely to be safe, or approved by any authority: <S> Asymmetric thrust will make the takeoff very difficult. <S> In particular, until the airplane reaches V MC , it may not be possible to keep the airplane on the centerline with takeoff thrust on one engine. <S> Especially for piston airplanes, single-engine performance is often very poor. <S> Hence the expression, "in the event of an engine failure, the other engine will get you to the scene of the crash." <S> All-engines-out operation in a multi-engine airliner is usually considered an extremely unlikely event, and as such, training is <S> patchy and contingency procedures are very dire if they exist at all. <S> Basically, if your one good engine dies, you'd be in mortal danger, much moreso than in a single-engine airplane, in which pilots are well trained for engine failures, since all-engines-out is a much more likely event. <S> Back to the notion of ferry permits, some guidance is given in 14 CFR §91.611 , which lays out conditions for one-engine-inoperative ferry permits for 4-engine or 3-engine-turbine airplanes. <S> It says nothing about twins though. <A> Large aircraft with huge power reserves probably could , assuming you can find a pilot willing to do it. <S> A twin-engine fighter like an F-18 very likely can - the single-engine thrust-to-weight ratio is nearly double that of a 777, and if you light the afterburner it has more thrust on one engine than a 777 with both mills turning. <S> Smaller piston twins usually cannot - one engine is not enough. <S> The crash rate for light piston twins is (or used to be) much higher than that of piston singles. <S> The reason: the asymmetric thrust made them much harder to control to the point where the occasional instructor said "if one engine goes, feather the other one too". <S> One notable example is the Cessna Skymaster - two engines, centerline thrust. <S> notable enough that the FAA created a multi-engine license category just for it. <S> Common accident mode in the Skymaster is feathering the wrong engine in-flight, and the number of takeoff failures with the back engine not running says it won't take off on just one either. <S> Maybe if you removed the prop, no passengers, minimum fuel and a really long runway. <S> Check your life insurance first.	Edit:With one engine inoperational, any twin-engined civilian aircraft would not be legal if it attempted a one-engine take-off.
What may be the cause of hot start problems in a Lycoming fuel injected engine? Cherokee Six, 32-300 1969. Lycoming engine is fuel injected with 450 SMOH. Cold starts are easy: 1/2" throttle, full rich, fuel pump on and hit starter after fuel flow starts. Runs great once running.Hot starts are hit or miss. If it sits over an hour it may start but if I miss it it has to sit for at least another hour till I try again or forget it. I've tried 1/2" throttle, full lean with and without fuel pump; full throttle, full lean with and without fuel pump and all combinations I can think of. Most of the time it spins without any cough or catch. Due for 50 hour oil change and will ask that plugs and magnetos are checked. I'm afraid to go anywhere for fear of being stranded for hours. <Q> The issue is undoubtedly vapor lock. <S> The following procedure runs cooler fuel through the plumbing while flooding the engine, then the flooded start procedure is necessary. <S> First, check your POH for the hot start procedure for your plane. <S> If not there, try this as it is for a very similar airplane: <S> Hot Starts on the Saratoga PA-32-300: <S> Intentionally flood the engine. <S> This runs cool fuel through the plumbing and "breaks" the vapor lock. <S> a) <S> Full rich b) <S> Wide open throttle c) <S> Fuel pump on, watch fuel flow gauge d) <S> When gauge registers flow, wait 3-5 seconds then red knob to ICO and pump off. <S> Crank engine with red knob still at ICO and with throttle wide open at first. <S> Gradually close throttle (at a rate that will take you about 10 seconds to close the throttle) and it should start up at some point. <S> When engine catches, do several things more or less simultaneously: <S> a) release ignition key b) throttle to idle to avoid over-revving c) mixture full rich. <A> No need to run the fuel pump as @Skip Miller says. <S> (though it may say that in the Saratoga manual) <S> I have done the following with success for hot starts on a IO-320, IO-360, and IO-540. <S> Throttle Full Open. <S> (Push in or forward) <S> Mixture Full Close. <S> (Pull out or back) <S> Crank engine. <S> Once it starts firing, put the mixture back in and pull the throttle back to idle. <S> Happy engine starts! <A> My MX shop checked the left Mag impulse coupler and coil at 360 hours all checked out <S> okay. <S> Still hard starting hot start. <S> Mx did 500 hour AD on left and right Mag still hard starting hot start. <S> Mx check the timing still hard starting. <S> Mx just put new Concord battery with a new Skytec starter in, still hard starting on cold start and hot start. <S> Final Mx check the coil cold resistance was normal no problem. <S> Mx then heated the coil up to simulate a hot engine and the coil failed no spark. <S> Mx put a new coil in it start everytime hot or cold. <S> This has been a nightmare to start <S> and I was afraid to go anywhere and shutdown knowing it would not start until the engine cooled down. <S> I hope this helps someone out there with the same problem. <S> Amen. <A> The symptoms you describe can occur when one of the injectors is not closing completely, causing flooding or an overly rich mixture.	Also have the injectors checked. In the fuel injected Lyc 540, the fuel injection plumbing is on the top of the engine which is the cold side of the engine when you are flying but when parked, heat rises! I have a 1969 PA 32 300 with 420 hours on engine, for the last 12 months it has been very hard starting after a flight.
Is it an overkill to request to see airplane maintenance logs at a new flight school? I'm getting a checkout at a new flight school, so I don't know anything about the maintenance records of their airplanes other than this school has been in operation for some time and so I assume everything is in order. As PIC, though, I would think I would feel better seeing for myself that this plane I have never flown before is indeed up-to-date, at least in its required inspections. I've never had an urge to do this before, I've always just trusted that the flight school is running things properly, but I guess since I have quite a bit more experience since my last checkout I felt like looking into this would be judicious. Is this overkill? Would it be taboo or send a message of distrust to the school if I asked to see the mx logs on my plane I'm getting checked out in? Does anyone make it a point to do this? Thanks in advance for your comments. <Q> I'd refer to FAR 91.3(a): <S> The pilot in command of an aircraft is directly responsible for and is the final authority as to the operation of that aircraft. <S> Therefore, I believe you have a duty to determine that the aircraft is properly maintained. <S> While that doesn't mean disassembling it and checking the work yourself, I do think that its reasonable to verify that the maintenance logs have recent entries, and appear orderly. <S> At my old flight school, I never got any grief at all (and occasional complements) <S> when I wanted to see the logs for some reason. <S> If they give you so much as an eye-roll when you ask to see the logs, that should be a cautionary sign. <S> I think it is also an easy way to meet the maintenance guys, and be introduced to them as a careful, thoughtful pilot. <S> (The Mx guys likely despise "cowboy" pilots who bring back damaged equipment, and don't report it.) <S> You'll get to know some people at the new school, and get a reputation right off the bat. <A> Is it overkill? <S> Probably. <S> Most of what you should be concerned about is stuff you should find on a thorough preflight. <S> You would need some specialist knowledge to determine if a log entry is a "problem" or not (absent something like "repaired right main gear attach point and installed new right main landing gear assembly" showing up). <S> Most of the schools/rental outfits around here keep a status sheet with the aircraft's dispatch documents so you (and they) can easily see when required time-in-service or calendar-time inspections are coming due. <S> If there isn't one I'd make a point of asking about inspections and such to be sure they've been done, but otherwise I'd be pretty trusting. <S> Bear in mind that there's nothing stopping an unscrupulous school or mechanic from "pencil-whipping" inspections. <S> An aircraft can be perfectly airworthy on paper but full of "How could they possibly have missed that ?!" <S> maintenance discrepancies when you preflight it. <S> Should they let you review the logs with an instructor or mechanic if you ask? <S> I think so. <S> If you want to do this you should let them know in advance <S> so they can have the logs available. <S> Bottom line, as PIC you need to be sure that the aircraft is in an airworthy condition (which includes compliance with required inspections, ADs, etc.) <S> and if you feel you need to see the logs to verify that it's your call. <S> Reviewing the logs probably isn't a common request for casual rentals, but particularly if you're taking flight lessons there spending some time and reviewing the maintenance records for an aircraft is a great learning experience. <A> I don't see it as overkill at all. <S> Not only is it your responsibility as a pilot to verify if an aircraft is airworthy, it may save your life. <S> For more info on why and how to perform a deeper first-review of a new aircraft you might be thinking about flying for the first time I would strongly recommend a wonderful M-Pamphlet published by the FAAST team called " Advanced Preflight ". <S> Advanced Preflight refers to conducting a preflight that goes beyond the normal preflight checklist. <S> This is accomplished by obtaining a valuable maintenance history of the aircraft and developing an additional items checklist. <S> While developing the additional items checklist requires some time, once you have developed the additional items checklist it can be used in conjunction with the aircraft’s preflight checklist for all future preflight inspections. <S> Using the additional items checklist discussed in this M-Pamphlet will guide you through an enhanced preflight inspection to help reduce your risk of undetected maintenance problems. <S> This M-Pamphlet provides information to owner/operators and AMTs on how to conduct a complete review of all maintenance-related data on the aircraft you operate and/or maintain, the steps in extracting the valuable information from this data, and how to develop an additional items checklist to be used in conjunction with the aircraft’s preflight checklist for all future preflight inspections. <S> Whether you are an AMT or a pilot who owns, rents, or borrows an aircraft, Advanced Preflight is for you! <S> For the AMT, this pamphlet will assist in conducting a records review prior to beginning an inspection on an aircraft. <S> This is vital if the aircraft to be inspected is new to the AMT. <S> For the pilot, remember to always use your preflight checklist. <S> The additional items checklist does not replace your existing preflight checklist; it only enhances its use.	Schools generally do a good job maintaining their aircraft (they're used hard, but kept airworthy because if they're out of service the school is losing money).
How can I find telephone numbers for FAA ATC facilities? It is often desirable to call an FAA air traffic control (ATC) facility on the telephone: To ask a question about a " mark-the-tape " incident To request a tour To notify the facility of unregulated nearby operations like RC plane flying How can one find the non-emergency telephone number for an ARTCC, TRACON, or control tower (ATCT)? <Q> You would think the control tower phone numbers would be listed prominently and conveniently on the FAA website. <S> You would however be wrong 1 . <S> You can also get tower phone numbers from Flight Service (1-800-WX-BRIEF). <S> AC-U-KWIK also has tower phone numbers in a conveniently searchable system (punch in the airport identifier and it will be in the results you get), and the printed edition of the AOPA airport directory used to have tower numbers as an appendix <S> (I'm pretty sure it still does). <S> 1 <S> – Actually that's not strictly correct: <S> some regions publish tower numbers prominently. <S> Most don't, or my search skills aren't good enough to find them. <A> Near the end of the Chart Supplement there is a list of ARTCCs and airports with 24 hour phone numbers. <S> The Chart Supplement also has the number for the Airport Manager for every airport. <S> They should be able to get you in touch with the tower if it is not on the list. <S> You can download these pages in ForeFlight or directly from the FAA website. <A> For the U.S.: AIR TRAFFIC CONTROL TOWER (ATCT), TERMINAL RADAR APPROACH CONTROL (TRACON), AND AIR ROUTE TRAFFIC CONTROL CENTER (ARTCC)TELEPHONE NUMBERS AND LOCATIONS http://www.csobeech.com/files/ATC-Phone-Numbers.pdf	Your best bet would be to contact the Flight Standards District Office that covers your area - they can get you in touch with whatever other branches of the FAA you might need to talk to.
What measures were taken to keep Soviet airline pilots in the Soviet Union? How did the Soviet Union keep airline pilots from leaving the country? It seems like it would have been pretty easy to do since the pilots are already in the air. And I would guess at least some flew close to the borders. <Q> Civilian pilots had a quite comfortable life. <S> Flying high-tech gear has an attraction in itself, and the propaganda did what it could to strengthen patriotic spirits. <S> There were not many reasons to defect if you did not mind the nonsense in the papers but appreciated to be part of a privileged class. <S> And everybody knew that defection would have dire consequences for all relatives left behind. <S> The same is true for military pilots, and on top the Russian air defense was organized quite differently from NATO's, thus military pilots flew almost by remote control. <S> This went as far as using radios which had only a dozen of pre-set frequencies. <S> The pilots did not know the frequency, they just pushed the button with the number they were told by ground control. <A> For commercial flights, the USSR had a "Political Officer" (KGB agent) on the plane in much the same role as Air Marshals today, just the other direction - they kept the pilots from hijacking the aircraft. <S> The system would have also insured that the flight crew's family were safely at home in Mother Russia when the pilot was abroad. <S> Military aircraft were kept at home by the simple method of small fuel tanks. <S> The MIG-19 was once described as a plane that "goes nowhere, and does nothing, very quickly". <S> Sure, they had decent range with external tanks, but a good number of Soviet-era fighters could realistically declare a fuel emergency right after takeoff. <A> The premise of the question, that pilots in the Soviet Union needed somehow to be "kept in" as if they wanted to leave, is simply false. <S> Also simply false is the inference in drawn in the the answer (currently accepted as correct!) <S> about the role of "Political Officers". <S> Life in the USSR was frankly horrendous for many people: <S> certain ethnic minorities, those who belonged to national or political groups that had fought and lost battles with the ruling classes, dissidents - but funnily enough, these people didn't often get to become airline pilots (or airline staff, or diplomats, or functionaries who got to travel across international borders as part of their work). <S> People who got to travel in those ways were already part of a trusted, privileged elite. <S> Specious explanations don't need to be invented. <S> The people who wanted to leave because they were suffering dreadful privations and restrictions at the hands of the Soviet state weren't allowed to leave their towns, have telephones in their apartments or own typewriters - <S> they idea that they might be allowed to pilot airliners is just a joke. <S> The notion of that airline pilots might be seeking to defect as a matter of course is honestly risible, however nicely it might harmonise with a certain Cold War narrative. <S> You can see how bogus the reasoning is: <S> if the "Political Officers" were there to prevent defection, do you imagine they had one assigned 24 hours a day to each member of an international flight's crew on their overnight stays outside the USSR? <S> It's nonsense. <S> The system would have also insured that the flight crew's family were safely at home in Mother Russia when the pilot was abroad <S> Sure, the families of dissidents and refuseniks were effectively deployed as leverage. <S> But people like pilots?! <S> It's just not the case. <S> For the most part, Russians posted abroad were posted with their families when appropriate, just like everyone else. <S> As I said, life in the Soviet Union could be quite ghastly if you were on the wrong side of things, but there's really no need to recapitulate stale old Cold War propaganda to try to paint a picture that is worse than the reality was.	In a few words: what kept pilots from defecting from the USSR was that, on the whole, they didn't have a reason to want to .
Why are gate numbers also marked on the outside of a terminal? As per this question. What are these numbers visible from the runway at Narita airport? A UK document is linked in the accepted answer but it doesn't list big number marking on the outside of the terminal. Surely such numbering is of little value to pilots- too coarse of location information. So who use such a gate number and how? <Q> Of course it's helpful to the pilots, and the ground crew, too. <S> Even if you know the airport layout in detail, it's easier to go to the gate signposted as C27, say, than to go to the seventh gate on the left. <S> Now remember that everybody who has ever flown a plane into that airport has flown there for a first time, and everybody who's ever worked ground crew there had a first week. <S> Just imagine the corresponding situation of a car park with somewhere between a few tens and a couple of hundred bays, where it's very important that you park in your assigned bay. <S> Would each bay's number be written on it? <S> Of course it would. <A> Without these signs it would be easy to misidentify a neighboring gate if it also had a ground crew ready to accept an airplane. <S> They are also useful for keeping an eye on an occupied gate from a distance while you wait for an aircraft to leave. <S> They are also illuminated which helps locating the right gate at night or in low light. <S> The electronic signs high on the terminal building are helpful to aircrew and ground crews. <S> They often list aircraft info, departure/arrival airports and time to scheduled pushback. <S> The on ground painted lines are useful for initially lining up for a gate and in making the elaborate maneuvers required getting into certain tightly spaced gates. <S> Once you get this close you are being guided by ground crew and have wing walkers watching your clearances. <S> The final painted ground positions for nosewheel position (by aircraft type) are only useful to the ground staff guy with the wands <S> -- you can't see them yourself when needed. <A> Gate designation that are visible to the outside are important for a number of reasons. <S> Mainly for Ground Support teams that service aircraft, fuel the planes, mechanics, baggage, and yes even pilots to use to find the correct gate to park upon arrival.	The signs on top of the jet bridges are useful in identifying your assigned gate.
Is a smartphone required to control a DJI Phantom 2 Vision+? Not sure if this is on-topic here, as the official guidance seems a bit vague. Anyways, I've got a relatively simple question. I'm considering purchasing a Phantom 2 Vision+, but am a little unclear about what options there are in terms of controlling it. Their website makes a big deal about being able to set waypoints (using an iPad/mobile app) and have the quadcopter operate as an autonomous drone. And that's useful for certain things, but it seems like it would be more fun to control it directly by remote. Judging from the video here , it does appear that the quadcopter ships with a remote. But it also looks like you're expected to stick an iPhone/smartphone onto the remote? Is that a requirement or just an optional extra? Is it possible to fly the quadcopter without using a smartphone/mobile app (using just what's included in the box)? <Q> I'm pretty sure it works without the smart phone. <S> If I understand correctly, the smart phone app simply relays the imagery from the camera, which can be useful for navigating especially if you do not have a clear line of sight. <S> Ars Technica ran a piece on this very model, which might interest you. <A> Here are your answers: You can <S> To see what you are filming and to start and stop recording among many other features, you will want to have the app on a smartphone connected. <S> Everything you need to do this is included when you buy. <S> You don't have to use the app, but I dont see why not. <S> Please check out my video for a full review of its features. <A> The phone/ipad is used to relay video only and other wise control the camera. <S> You also get some flight information such as distance, elevation, speed relayed to your display. <S> but if you are never going to use it, why not get a straight Phantom 2, which doesn't have a camera on it. <S> It's much cheaper. <S> The camera system on the Phantom 2 vision+ is very impressive though!	It is not a requirement to use it standard control for the P2V+ is via the physical remote it comes with, you can also set waypoints via the app (You may take over control at any time)
What's the name and purpose of a barrier raised behind a carrier based jet? I saw this picture in Wikipedia with a Su-33 jet on carrier deck with some barrier raised from the deck behind the jet tail: What is this barrier for and what's the official term for it? <Q> The official name is a Jet Blast Deflector . <S> As the name suggests, they direct the fast-moving and hot air from the jet engines upwards. <S> This protects the personnel and equipment behind the departing aircraft from getting blown around or damaged from the jet blast. <S> Because of the high temperature of the jet blast, they may have active cooling systems, and must be allowed to cool sufficiently before being used as regular deck again. <S> To illustrate the risks, see this video , which shows a vehicle being blown away by a 747. <S> There was also a recent event in Pakistan where a 737 damaged the tarmac (and, as a result, itself) during an engine run-up. <S> To make a comparison, each engine on a 737-400 can produce up to 22,000 lbf (98 kN) of thrust. <S> The Su-33 in your picture has two engines close together which can each produce 16,750 lbf (74.5 kN) of thrust, or 28,214 lbf (125.5 kN) with afterburner. <S> That's a total of 56,248 lbf of thrust in afterburner, or 2.5 times the force of one engine on the 737-400. <S> Of course, this does not directly equate to jet blast or temperatures, but it is a good indicator of the forces involved. <S> To provide a better idea of the jet blast, see this chart (based on the 737-800). <S> At 20 m behind the tail (which is about 20 m behind the engines), the jet blast can reach 300 km/hr at takeoff thrust. <S> For more details about jet blast on the 737 series, see the Boeing documentation . <S> The CFM56-3 (used on the 737-400) can produce exhaust gas temperature (EGT) of up to 930 C at takeoff. <S> This will mix with the cooler bypass air (and ambient air) to reach cooler temperatures further behind the engine. <S> Military jet engines have a smaller bypass ratio, which means there is less of the cool bypass air in the exhaust to mix with the hot core exhaust. <A> <A> It is a blast fence to protect the planes behind it from the destructive force of the jet blast of the plane in front of the fence. <S> The plane in position for takoff will go to full power for takeoff. <S> Check out this video of a pickup truck being towed through the full power exhaust behind a jet. <S> https://www.youtube.com/watch?v=DFP4xl0V0mk	It's a blast fence to prevent that the groundcrew walking behind the jet get blown away by the jet blast.
What are the length requirement for US aircraft N-Numbers / registrations? Many small aircraft registered in the US seem to have a registration that follows the pattern of N, 4 numbers, and ending in a letter. Sometimes they only have 4 characters, or less. And then there's the FAA Gulfstream N1 . Who decides on what the N-Number will be, and are there requirements for how long it should be? <Q> It's not just small aircraft in the US - all aircraft with US registration follow the same rules. <S> The FAA has guidelines on how an N number must be formed . <S> Basically, there are relatively few limits - you can have N + up to 5 characters, up to 2 of which can be letters (at the end). <S> These characters may be: One to five numbers (N12345) One to four numbers followed by one letter (N1234Z) One to three numbers followed by two letters (N123AZ) <S> To avoid confusion with the numbers one and zero, the letters I and O are not to be used. <S> Other Requirements <S> An N-Number may not begin with zero. <S> You must precede the first zero in an N-Number with any number 1 through 9. <S> For example, N01Z is not valid. <S> Registration numbers N1 through N99 are strictly reserved for FAA internal use. <S> When an owner registers an aircraft, they can request an N number, <S> provided it's not already registered. <A> Two other answers specify the algorithm for generating valid U.S. aviation IDs. <S> Many who view this question might also be interested to learn that the aviation scheme is part of the entire U.S. radio station identifier scheme. <S> IDs beginning with AA-AL, K, N, and W are allocated to the U.S. ( by ITU ). <S> CF-CK are used in Canada, DA-DR in Germany, etc. <S> Commercial broadcast stations have all letters (no digits) beginning with W, K, and N; W <S> as the first letter is used for almost all transmitters east of the Mississippi River and (mostly) K to the west. <S> U.S. amateur radio operators are assigned IDs with mostly letters with one digit near the front. <S> They are of the form L[L]DLL[L] <S> where L is a letter and D is a digit (or occasional two digits). <S> [L] means an optional letter. <S> The whole ID is 4 or 5 characters. <S> The digit is assigned by class of license and region according the this scheme . <S> Government, scientific, civil, and other users are assigned by other unique schemes. <S> For example, the Oregon NOAA weather radio stations (see table of stations ) all begin with 2 or 3 letters and end with 2 to 4 digits. <A> Per FAA.gov: An N-number can be in any of these formats One to five numbers (N12345) One to four numbers followed by one letter (N1234Z) One to three numbers followed by two letters (N123AZ) <S> N-numbers do not have A zero (0) as the first number <S> The letters "I" or "O"" <S> N1-N99 are reserved for the FAA/govt. <S> Someone who wants to register an aircraft, can either request a specific N number, if it's available, or they can just ask the FAA for a random one.	Here's what the FAA has to say: U.S. registration numbers may not exceed five characters in addition to the standard U.S. registration prefix letter N .
What is this molten metal coming from the engine of an Avro RJ 100? Yesterday I flew in an Swiss Avro RJ100. As soon as we landed I was shocked to see some sort of molten metal which was incandescent and glowing red dripping down from the vent as indicated in the picture. It was almost catching fire! I was suprised to see immediately the maintenance van pitch up to the plane when we didn't even get to a stop. Is this normal? This image isn't of the problem flight, but shows where the problem was. <Q> I do not see anything in your photo, apart the engine that looks perfectly normal. <S> Anyway here <S> it is written that the fuel burns at up to 2000 degrees Celsius and the temperature at which metals in this part of the engine <S> start to melt is 1300 degrees Celsius. <S> Hence the metal may melt if something goes wrong. <S> Avro RJ100 has four engines so should be able to land with one inoperative. <S> From the question I have just asked myself , it will not be qualified as accident so may not get widely known. <A> Looking at your photo, it seems the sun is shining roughly from your two o'clock. <A> it seems that what you were looking is one of the reverse thrust latches that wasn't properly secured.	What you saw may not have been metal, but simply some other fluid (fuel, lubricant, hydraulic) leaking out of the engine, reflecting the sunlight.
Why does a T-tail produce a pitch-down moment in sideslip? Here is something which I did not find in any book, but confirmed in several wind tunnel and flight tests: A T-tail causes a strong nose-down moment in sideslip. This can even be observed in a potential flow analysis, so no fancy viscous effects should be required for an explanation. But I have never understood why it happens. I would even have an explanation for a pitch-up, but the pitch-down really has me puzzled. Does someone here know more? <Q> I've found some useful research here: E.C. Polhamus. <S> Some factors affecting the variation of pitching moment with sideslip ofaircraft configurations. <S> Technical report, NACA T.N. 4016, 1958. <S> The image shows the situation for high angles of $\beta$: <S> At large angles of sideslip with swept horizontal tails, the loading will probably not be antisymmetrical mainly because of the difference in lift effectiveness of the leading and trailing portions of the horizontal tail caused by the difference in their effective sweep angles. <S> This would result in a net lift induced on the horizontal tail which is a function of sideslip and tail height. <S> This possible effect of tail height is illustrated in sketch 9 for large positive sideslip <S> angles <S> : Interesting to see is that the model has no wings, so we can rule out any causes related to wings, in case people were thinking in this direction. <S> I putsome more thought into it, and I drew these diagrams, which helped me understand the things being said in the paper. <S> The blue pluses and minuses are the resulting velocities caused by the horizontal velocity as a function of the sideslip ($V_{\beta}$).The red distributions are the forces on the elevator as consequence of this $V_{\beta}$. <S> This component creates an increased velocity over the left side of the rudder, and a decreased velocity over the right side of the rudder. <S> If there's no sweep, the effects are equally strong, and no effect on the lift is present (denoted by the top two images) <S> However, if there's sweep, the effect on the left side is less strong, whereas it is stronger on the right side (indicated by the two tails in the bottom row). <S> In a T-tail, this stronger influence is acting on the lower side of the tail. <S> As it is a minus (meaning a relative reduction in velocity), it will lead to a reduction in suction on the lower side, or an upward force, causing a pitch down. <S> In a normal tail, the minus will act over the upper surface. <S> It causes a deceleration of the flow over the elevator, thereby reducing the lift it generates. <S> This causes a pitch up movement. <A> Loss of aerodynamic lift of the horizontal tailplane (downward force) causes the aircraft to pitch down. <S> A disruption of airflow over the low pressure side of an airfoil has a greater effect on the airfoil's ability to create lift than a similar air flow disruption to the high pressure side of an airfoil. <S> On a conventional tail, the wind shadow of the vertical stab affects the high pressure side of the horizontal tailplane (the top surface) which is not as aerodynamically sensitive. <A> From the test pilot notes of the F-104: the centre of pressure changes with vertical position of the tail. <S> One of the reasons for implementing the T-tail on the F-104 was to create a more desirable sideslip-roll coupling, however the upward shift in centre of pressure also creates a nose-down pitching moment with sideslip.	On a t-tail, the wind shadow of the vertical stab affects the low pressure side (lower surface) of the horizontal tailplane which is the aerodynamically sensitive side causing a greater loss of effectivity of the tailplane.
Can I land a plane in a field? If I had a plane that could take off and land in a short distance (eg., the SD-1 Minisport ), do I have to use a recognized airport in order to land in the US? Or can I just land anywhere so long as it's class G airspace? FYI, this question is for non-emergencies. IE., if I just wanted to land there because it was convenient. <Q> Landowner's permission is always required. <S> Then check the municipal zoning regulations and the like - city, state regs etc. <S> Then your insurance company. <S> If all these points come up green, go do it. <A> The airspace is irrelevant. <S> You may, however, be breaking a range of different state laws. <S> Generally speaking, the things to watch out for: <S> (1) Landing on private property without express permission is trespassing (2) <S> Landing anywhere a person would be likely to be may be reckless endangerment (3) <S> Landing in such a way that would cause an unnecessary emergency response can result in a charge for intentional or careless use of emergency services (you can avoid this by calling them ahead of time and telling them you do not need emergency services) <S> In general, you can land on any public land that is not a place someone else would be (like a road). <S> If you land on a road without good reason, it could be construed as reckless. <S> In remote areas like Alaska landing off field is routine and occurs as a matter of course. <S> Pilots that fly in back woods areas and land off field all the time are called "bush pilots". <A> I land in my backyard regularly. <S> It used to be that we could land on town roads years ago, but the laws changed. <S> Without a ground crew it wasn't really safe. <S> There are three farms within a mile of me who have 2000+ foot grass strips, and they get regular visitors. <S> My yard isn't groomed as much so thankfully few people drop in. <S> Some municipalities have created local ordinances against landing on site not approved by the town. <S> The legality of those ordinances is not clear. <S> My homeowner's insurance does not care, as I do not advertise and encourage the public. <S> My aircraft insurance does not have a restriction about uncharted or sod/dirt strips. <S> If you are new at the game, I suggest that you walk the field before hand, and already have experience landing on rougher grass or dirt. <S> The FAA is aware of my landing area, but I chose to not have it charted. <S> Just adds to map clutter, and anyone in the area with an emergency has a ton of alternatives, most of which are better.	You can land wherever you want as far as the aviation regulations are concerned.
Why don't planes have a reverse propeller as air brakes? When I first heard the word air brakes it came to me that maybe the engine start rotating in the opposite direction for that, but since that's not possible, why can't we have an extra engine for air braking? Did I just invent a new braking paradigm? <Q> Planes with a variable pitch propeller can have a pitch range which twists the blades such that they provide reverse thrust. <S> This started to become a common feature on high-performance airplanes in the 1930s. <S> Not all variable-pitch propellers can produce reverse thrust, however. <S> The constant speed props on small propeller aircraft usually don't, because the energy of the plane after touchdown would be too small to justify the added complexity. <S> On big airplanes which need short landing distances (the C-130 , for example), they are a standard feature. <S> In 1936, Heinkel produced a sleek dive-bomber, complete with retractable landing gear and a reversible pitch propeller which could be used as a dive brake. <S> The He-118 <S> was test-flown by Ernst Udet , who did not pay attention at the briefing and went on to overspeed the airplane in a dive, destroying the prototype in the process. <S> Thus, the clumsy, fixed-gear Ju-87 was chosen to be the "Stuka" and the He-118 would end as an inspiration for Japanese aircraft designers. <S> The Pilatus PC-6 Turbo Porter is a favorite with skydivers because it can put the propeller into reverse even in flight. <S> This allows for spectacular descents and enables it to be safely back on the ground before the skydivers it dropped a moment before have landed. <S> As usual, Wikipedia covers the topic well, so here ist the link . <A> Peter Kämpf's answer covers the systems that prop planes actually use for reverse thrust. <S> The alternative presented in the question is a total non-starter for several reasons. <S> It's a complex and very heavy system. <S> Unless there was somewhere on the centreline you could mount this engine and prop, you'd need not just one of these things but two, for balance. <S> It causes drag while it isn't being used, which is all the time except immediately after landing. <S> For certification, aircraft have to be able to stop using just the wheel brakes, anyway, since the complexity of reverse thrust systems makes them likely to fail. <A> Jet aircraft (especially large transports) are often equipped with thrust reversers. <S> Not a requirement for landing, but takes some of the load and wear off the wheel brakes and tires. <S> They have them because of the high landing speeds and large masses they have to bring to a stop in a limited amount of space. <S> Propeller aircraft don't fly as fast, so landing speeds are not as high; for the most part, braking requirements are easily met with wheel brakes. <S> Engines are a significant part of the total weight and cost of an airplane. <S> Carrying around an extra just for reverse thrust would be impractical for cost/weight reasons. <S> Many propeller-driven aircraft are equipped with variable-pitch propellers, including many light aircraft; in theory, any of them could have a "reverse" setting, but (as described in one of the other answers) <S> you would only see it on larger aircraft designed for operation on short runways. <A> There is no need for an extra engine for this purpose, which if fitted would be a weight problem and a maintenance nightmare. <S> The thrust reversers on jet airliners are pairs of ducts which, when deployed, intercept the normal jet exhaust and redirect it forwards . <S> The reverse thrust produced is somewhat less than the forward thrust available, but it's plenty to permit a powerful deceleration, and it's particularly valuable on wet and icy runways where wheel brakes aren't very effective. <S> The Harrier "jump jet" fighter is nearly unique in its ability to take off and land vertically, and is capable of using the same thrust-vectoring control in combat. <S> By suddenly turning the thrust backwards, the aircraft can decelerate very sharply in midair , potentially moving it from a defensive position in front of an enemy to an offensive position behind it. <S> The Piaggio Avanti is a particularly interesting civilian turboprop, with an unusual "three surface" wing layout, pusher propellers, and very clean aerodynamics. <S> It can also land and come to a halt within 500m of runway , <S> thanks in part to reversible-pitch propellers. <S> This short-field capability contributes to its lower operating costs versus corporate jets of similar size and performance.	Most jet airliners and some propeller-driven aircraft (chiefly those designed for short-field operations) do in fact have some sort of thrust reversal system already. Even if reverse thrust was beneficial, reversing the engine's rotation would be totally infeasible; engines are simply not designed to run either way round, and any system which would decouple the engine from the propeller (as would be needed if you wanted to implement a "reverse gear") would be a safety/reliability nightmare, not to mention heavy and expensive.
Can a commercial aircraft be detected by ATC's / Radar systems if all its engines fail? In an event of failure of all engines of a commercial aircraft in mid air and no secondary backup or generators powering the plane (plane is virtually powerless and no comp systems work on board), would the ATC still be able to detect the aircraft with accuracy and if yes how is it done ? Are there any conditions that it has to be flying in an area which is monitored or any basic stuff which HAS to be working for ATC to detect ? <Q> In an event of failure of all engines of a commercial aircraft in mid air ... <S> That would be a very rare event. <S> In the modern cases where this has happened within an ATC area, it has not prevented location of the aircraft so far as I know. <S> ... and no secondary backup or generators powering the plane <S> Even a two-engined airliner has an Auxiliary Power Unit (APU) and a Ram-Air Turbine(RAT). <S> I believe they also typically have 10-15 minutes battery power for critical systems. <S> I don't know if any airliner has ever lost all generators other than in cases where the aircraft was destroyed in flight (e.g. PanAm 103). <S> would the ATC still be able to detect the aircraft with accuracy <S> If an aircraft's transponder and secondary-radar are not operating, ATC would rely on primary radar, which is less accurate, particularly for altitude. <S> They would also ask the pilots for their position over VHF radio and ask other aircraft in the area to locate the aircraft. <S> Example: British Airways Flight 9 <S> All four engines flamed out due to ingestion of volcanic ash. <S> Despite the crew "squawking" the emergency transponder setting of 7700, the aeroplane could not be located by Air Traffic Control on their radar screens. <S> The pilot communicated with ATC over VHF radio and later restarted the engines. <S> The engines had enough electrical power to restart because one generator and the onboard batteries were still operating Example <S> Air Canada Flight 143 (the "Gimli Glider") <S> This 767 ran out of fuel mid-air and all engines stopped. <S> The 767 was one of the first airliners to include an Electronic Flight Instrument System (EFIS), which operated on the electricity generated by the aircraft's jet engines. <S> With both engines stopped, the system went dead, leaving only a few basic battery-powered emergency flight instruments. <S> The pilot communicated with ATC Winnipeg and First Officer Maurice Quintal began to calculate whether they could reach Winnipeg. <S> He used the altitude from one of the mechanical backup instruments, while the distance traveled was supplied by the air traffic controllers in Winnipeg, measuring the distance the aircraft's echo moved on their radar screens . <S> So <A> Primary radar (send out radio pulse and interpret reflections) was designed for this (detect uncooperative enemy aircraft). <S> A more complete explanation of this system can be found on the answers of this question . <S> Having said that, when all engines fail the backup is a Ram Air Turbine which gets deployed automatically and provides enough power for critical systems including controlling the craft, radio and transponder. <S> Having every backup fail is extremely unlikely. <A> RAdio Detection And Ranging do not require active participation from the airplane, so ATC will still see it. <S> However, ATC will not know of the plane's condition and will likely not be able to communicate with them. <S> Pretty much, if the craft is made out of metal and is reasonably high in the air, ATC will see it. <S> Most non-metals will show up on radar as well, such as this guy .	yes, If the aircraft with all engines out is in radar range and ATC are attentive, they can track the aircraft's location.

Subsets and Splits

No community queries yet

The top public SQL queries from the community will appear here once available.