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102 votes

Could airline tires be deflated in mid-flight to reduce weight?

You want to reduce weight by removing a few kilos of air, and adding an equal, if not greater, amount of kilos of pumps needed to reflate the tires (see David Richerby's answer for details), not to ...
Federico's user avatar
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81 votes
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How are brakes cooled on heavy aircraft?

Summary The order of magnitude of brake energy after a rejected takeoff (RTO) for a very heavy aircraft is 1 GJ, or 100 MJ per wheel brake. Aircraft brakes are cooled with ambient air, either ...
bogl's user avatar
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75 votes
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What is the purpose of the extra wheel on the XB-70 main gear?

It is a sensing wheel that is part of the antiskid braking system. It contains an electronic sensor to measure the true groundspeed of the airplane. See NASA Technical Note D-4836, Landing Loads and ...
Fred Larson's user avatar
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66 votes
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What operation is this aircraft performing?

The flight in question is most probably an evaluation/calibration flight for radio navigation systems at Ust-Kut. The aircraft is a Yak-40 special version designated for such tasks: Aviamuseum - Yak-...
Jpe61's user avatar
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60 votes
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Why does the 767’s main landing gear appear spaced considerably farther apart than airplanes of a comparable size?

The Boeing 767 main landing gear is not actually spaced further apart than other twin-engine wide-bodies: Aircraft Wingspan Gear Spacing Fuselage Width Gear Spacing:Fuselage Width B767 48 - 52 m 9.3 ...
Bianfable's user avatar
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55 votes
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Why would one plane in this picture not have gear down yet?

Why does the 747 not have its gear down yet? Based on the image it is hard to say how far these aircraft are from the runway. The 747 could still be be quite far from the runway and thus does not ...
Bianfable's user avatar
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53 votes

How are brakes cooled on heavy aircraft?

Hot brakes are normally cooled by natural convection, but in extreme cases the fire fighters will cool overheated brakes. Some designs use brake fans. From the linked page: Brake fans reduce brake ...
Peter Kämpf's user avatar
51 votes
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What is the purpose of the Dash 8’s “TOUCHED RUNWAY” warning light?

The light is a tail-strike indicator. Touched Runway system The Touched Runway system provides a warning light in the flight compartment. It illuminates when the aft fuselage ...
Transistor's user avatar
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50 votes
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Why did the space shuttle use bias-ply tyres instead of radials?

Simply put, for the weight bearing factor bias-ply is a lighter tire, and when building a spaceship weight is the top concern. The reason they were thin and single use also had to do with weight, ...
Dave's user avatar
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49 votes
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How can the landing gear fit in the small room in the engine bay on the Tupolev Tu-144?

The Tu-144 uses much smaller wheels than comparably-sized subsonic aircraft. This makes it possible to rotate the gear bogie sideways towards the middle of the aircraft, so it can be stowed vertically ...
Peter Kämpf's user avatar
48 votes

How can the landing gear fit in the small room in the engine bay on the Tupolev Tu-144?

The Tu-144 landing gear rotates 90 degrees when retracted up between the engines. Source: Tu-144 Landing Gear Retraction Source: Tu-144 Landing Gear Retraction
Mike Sowsun's user avatar
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44 votes

Why do landing gear tires smoke upon touchdown?

Because the tires are momentarily skidding on the pavement as they rapidly spin up from standstill to the jet’s touchdown speed. It’s just a puff of burnt rubber but the tire tread itself becomes ...
Romeo_4808N's user avatar
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44 votes
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Do military bases still employ wheel watchers?

No They do not continue this practice anymore. This is likely because landing gear are more reliable now than they were in the 70's. There is also the practice of Air Traffic Control prompting ...
M28's user avatar
  • 2,459
37 votes

Could airline tires be deflated in mid-flight to reduce weight?

Some military transport aircraft can indeed adjust tire pressure from the cockpit for soft field operations. The Antonov An-22 would be one example. A central tire inflation system is a standard ...
Peter Kämpf's user avatar
35 votes
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Is there a landing gear system that extends automatically to prevent belly landing?

The simple fact is that an unintended gear deployment could be catastrophic, as it has a profound impact on the flight dynamics of the aircraft (one of the reasons there are warnings for both ...
Burhan Khalid's user avatar
34 votes

Could airline tires be deflated in mid-flight to reduce weight?

Along with the pump (and such) involved, it should be noted that inflating the tires of a large aircraft is a fairly non-trivial undertaking from a safety point of view. In particular, when you're ...
Jerry Coffin's user avatar
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34 votes
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Why was the nose gear of Concorde located so far aft?

In a conventional "tricycle arrangement", placement of the nose landing gears is normally chosen to respect three basic requirements: nose landing gear should carry 10 to 15% of the total ...
sophit's user avatar
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33 votes

Why use an airplane with non-retractable landing gear for aerobatics?

As you mentioned, drag is one of the reasons why retractable landing gears are used in the first place. But in order to use it, there are way more considerations than just drag. Scale: Size of the ...
tegginamaniss's user avatar
33 votes
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Why do aircraft sometimes bounce while landing?

The FAA covers this in the airplane flying manual quite nicely: Bouncing During Touchdown When the airplane contacts the ground with a sharp impact as the result of an improper attitude or an ...
Dave's user avatar
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32 votes
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Why should an overheated wheel be approached from the front/back and not in line with the axle?

Besides staying clear of the fuse plug in the rim, it's partly because the sidewall of the tire is the weakest part of the carcass, so that a rupture from overpressure from overheating means most of ...
John K's user avatar
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31 votes

Is there a landing gear system that extends automatically to prevent belly landing?

It has been tried before. Piper's PA-28R and PA-32R aircraft were equipped with an automatic landing gear extension system which would automatically extend the landing gear below 85kts regardless of ...
Romeo_4808N's user avatar
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31 votes
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Why complex landing gears are used instead of simple, reliable and light weight muscle wire or shape memory alloys?

Shape-memory alloys change their shape with temperature, with control usually achieved with electric heating in one direction, and back with convective heat transfer to the environment. There is one ...
Jan Hudec's user avatar
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30 votes

Are there any aircraft with a 4-wheel nose landing gear and a 16-wheel main landing gear?

The Il-76: 4 main bogies with 4 wheels each, nose gear with 4 wheels. this one has a better view of the wheels, but it's a CGI: 4-wheel nose gear is rare, 16-wheel mains are more common: Boeing ...
Hobbes's user avatar
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30 votes
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What causes a Cessna 172 and its gear to shake violently after landing and braking?

I'm pretty sure you have encountered "nose wheel shimmy". For reference, see this video on Youtube: c172 M Nose wheel shimmy [sic]. The shimmy can occur for a variety of reason, most likely ...
Jpe61's user avatar
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28 votes

Could airline tires be deflated in mid-flight to reduce weight?

You simply wouldn't save any weight. One of Goodyear's largest commercial aviation tyres is the 54x21.0–23 Flight Leader,* used on Airbus A330s and A340s. That is, outside diameter 54 in, ...
David Richerby's user avatar
26 votes
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Are there any aircraft with powered landing gear?

WheelTug makes an addon motor for a nose wheel. This is a demo of the unit being developed for a B737. They intend to lease it to airlines. It works well under most circumstances, but has difficulty ...
Pilothead's user avatar
  • 20.6k
26 votes

Are there any aircraft with a 4-wheel nose landing gear and a 16-wheel main landing gear?

The Antonov AN-124 has 4 nose wheels and 20 mains which is close to that configuration. The Antonov AN-225 is also close to being configured this way. It has 4 nose wheels but has 32 mains. (source)...
Dave's user avatar
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25 votes
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Is it better to shut down the engine(s) or leave it (them) running when a gear up landing is imminent?

There's two schools of thought. First is the keep the engine on school because keeping the engine on: Gives you more control of the airplane Gives you the option to go around Keeps the procedure ...
GdD's user avatar
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