171 votes
Accepted

Why does XKCD say that autogyros will crash if the pilot reacts to a stall as in a normal airplane?

That one thing is to unload the rotor too much (i.e. "push on the stick"): From explainxkcd: ... Unfortunately, as soon as the rotor stops spinning, the whole aircraft falls like a brick ...
Wayne Conrad's user avatar
  • 2,357
48 votes

Is it practical to intentionally stall an aircraft to execute a fast, controlled descent?

It isn't practical for a number of reasons: Intentional stalls are inherently dangerous. Stall-spin accidents are a major cause of accidents, stall recognition and recovery are taught specifically to ...
GdD's user avatar
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38 votes
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Why do passenger jet manufacturers design their planes with stall prevention systems?

Why do car manufacturers install seat belts? Shouldn't licensed drivers be well aware that they should slow down when it's raining or snowing and that they shouldn't run through red lights or stop ...
FreeMan's user avatar
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37 votes
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Why does my wind tunnel experiment give two different stall angles of attack?

This is called stall hysteresis. You have two different situations and the flow reacts differently in each of them. When increasing the AOA The flow is attached to the wing and the boundary layer is ...
MaximEck's user avatar
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34 votes
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What is the stall AoA for the space shuttle?

As far as I can tell, NASA has never given a straight-forward answer to this question. The theoretical stall AoA is likely in the 33-40° range (see reason for that guess below). However, at ...
Bret Copeland's user avatar
34 votes

Is a "stalled" aircraft free-falling?

If the cables break on an elevator (and the safety brakes fail), you won't be in true freefall. You'll still have friction from wind resistance, from the guide rollers on the rails, etc. The same is ...
HiddenWindshield's user avatar
33 votes
Accepted

Do Air Traffic Controllers have to remember stall speeds for different aircraft?

No because aircraft are categorized by their speed at the runway threshold (1.3 times stall speed). VAT —Speed at threshold used by ICAO (1.3 times stall speed in the landing configuration at maximum ...
mins's user avatar
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32 votes
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On Air France 447, what would have been the lowest altitude to initiate recovery after the stall developed?

For the stalled flight to recover, the nose needs to be pointed in the airstream, and then the aircraft pulled up with load factor below the ultimate load. From the accident report: The recordings ...
Koyovis's user avatar
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32 votes

Why do aircraft stall warning systems use angle-of-attack vanes rather than detecting airflow separation directly?

The short answer is that we want to warn the pilots about an impending stall well prior to an actual stall condition. From a safety perspective, waiting until the airflow starts to separate, or at ...
peekay's user avatar
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30 votes
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Does a sudden drop of the velocity of the headwind affect the airspeed by lowering it?

Your airspeed does not remain constant because of inertia: it takes more time for the airplane to adapt to the new relative wind, compared to the time it takes for the wind to change. Example One: ...
kevin's user avatar
  • 39.7k
30 votes

Why does XKCD say that autogyros will crash if the pilot reacts to a stall as in a normal airplane?

This is a well known problem with gyrocopters. The first answer was partially correct in that the problem was caused by pushing the stick forward and unloading the rotor. However, the problem wasn't a ...
scientious's user avatar
29 votes
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When approaching a stall, is the first priority to apply power or lower nose?

The instinct drilled into a pilot's head from the beginning as the primary response is "lower the nose" to lower AOA. If you learn in a glider, that's the only option, so it's easy to drill the ...
John K's user avatar
  • 131k
29 votes
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Why do airplanes usually pitch nose-down in a stall?

You are quite close to the answer And indeed, if the wings stalled before the tailplane, I would expect the downforce produced by the tailplane to be dominant, and the nose to pitch even further up. ...
Sanchises's user avatar
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27 votes
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Why does a stall decrease lift, rather than increasing it?

For a parcel of air to generate a lift force as it flows over the wing requires the wing to tip that air parcel's momentum vector downwards slightly; the reaction force that the wing experiences as it ...
niels nielsen's user avatar
27 votes

Could an airliner with only one functioning engine recover from a stall?

Yes, but the challenge is managing the asymmetric thrust effects when applying power during the stall recovery. Pilots are trained in the sim for two stall (actually, just stick shaker onset) ...
John K's user avatar
  • 131k
23 votes

Why does XKCD say that autogyros will crash if the pilot reacts to a stall as in a normal airplane?

I believe what the comic is referencing is Mast Bumping. Rotor blades are very flexible, and for a bunch of reasons, are free to pivot around the mast.(The shaft the blades are spinning around) In ...
Smoores02's user avatar
  • 239
23 votes

Why do passenger jet manufacturers design their planes with stall prevention systems?

To be certifiable, airplanes have to have some kind of cues to warn when you are getting close to a stall, and have decent behaviour during the stall, because nobody is perfect. Airplanes with very ...
John K's user avatar
  • 131k
23 votes

Could an airliner with only one functioning engine recover from a stall?

A stall recovery doesn't require engines (although they help, especially if altitude is an issue). To recover from a stall, you need to lower the angle of attack. You can do this by lowering the nose ...
Ron Beyer's user avatar
  • 36.2k
23 votes

What is the physical explanation for the pre-stall judder in a Spitfire?

It's because aircraft don't stall all at once. A stall occurs when the airflow over the upper surface of the wing separates from the entire upper surface, causing loss of lift. This airflow ...
Vikki's user avatar
  • 28.3k
22 votes
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Why is this video of a G36 Bonanza taking off so scary?

Because those trees will kill them If you look at this document regarding the Bonanza G36 performance you will note that the lowest stall speed written is 61 kts. 61 kts is 112 kph or 71 mph. We can ...
MichaelK's user avatar
  • 2,377
22 votes
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Is it practical to intentionally stall an aircraft to execute a fast, controlled descent?

You don’t need a new technique You don’t normally stall jetliners. And in a crisis the last thing you want to do is learn a new technique. Besides, they already have a trained practice for descending ...
Harper - Reinstate Monica's user avatar
22 votes
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Can a wing be stalled at a speed larger than its stall speed?

So when I fly in straight line how can I force flow separation at wings above stall speed? I think this is impossible. Stall is a matter of angle, not speed There is no stall speed, you can decrease ...
mins's user avatar
  • 73.3k
21 votes
Accepted

How will a prolonged series of steep turns produce a stall in subsequent level flight?

A prolonged series of steep turns will not produce a stall in subsequent straight and level flight. "after perhaps twenty turns have been completed, it will stall: stall, mark you, out of level ...
Mike Sowsun's user avatar
  • 37.8k
21 votes

Can anyone explain the reflex wings used in powered paragliding?

I'm haven't flown them but am very familiar with them and the reflex wing controversy because I was interested in getting into the sport (I normally fly power and gliders). A reflex wing when in "...
John K's user avatar
  • 131k
21 votes
Accepted

In this MD-11 stall test video, are we seeing the tail stalling first?

The entire tail is shaking (not just the horizontal stabilizer) not because it's stalling but because it is in the turbulent wake of the main wing. The tail is generating downforce as you can see ...
John K's user avatar
  • 131k
20 votes

Is it practical to intentionally stall an aircraft to execute a fast, controlled descent?

Normally, a stall and controlled flight are mutually exclusive. That AF447 would descend as it did has to do with the relaxed static stability of the A330 and its rear cg location as well as the ...
Peter Kämpf's user avatar
20 votes
Accepted

What does the autopilot do if activated in a stall condition?

In the AF447 accident, the autopilot disconnected because of inconsistent airspeed: Temporary inconsistency between the airspeed measurements, likely following the obstruction of the Pitot probes by ...
Bianfable's user avatar
  • 55.9k
20 votes

Could an airliner with only one functioning engine recover from a stall?

With enough height, any aircraft can recover from a stall without any engine power required. In fact, for under-wing engined aircraft like the 787, it is sometimes necessary to reduce the thrust, ...
Ben's user avatar
  • 14.3k
19 votes

Why is this video of a G36 Bonanza taking off so scary?

I know it's been a while since this was posted, but I'm the pilot flying this aircraft. Some interesting assertions are made here throughout the comments. Some facts: We were about half fuel 3 guys, ...
Chris Palmer's user avatar

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