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Although rare, it seems that there has been a number of cases where airliners have crashed as a result of a high altitude stall. I tend to picture this as entailing a long, uncontrolled descent where the plane never has proper flow over control surfaces to re-establish flight.

Is there any type of deployable technology that could force a plane into an attitude from which it could re-establish control? I am thinking of something like a drogue system that would force the nose down and dampen spin that could be jettisoned later.

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    $\begingroup$ I most of those cases the planes in fact did have proper flow over control surfaces, but pilots failed to apply correct recovery procedures. $\endgroup$ – Jan Hudec Jan 23 '15 at 15:00
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    $\begingroup$ Related questions: this, this and this. $\endgroup$ – Farhan♦ Jan 23 '15 at 15:00
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    $\begingroup$ elevators work pretty well $\endgroup$ – Peter Jan 23 '15 at 23:58
  • $\begingroup$ The only technologies needed: Eyeballs, brain, hand, and stick. (maybe a little rudder). $\endgroup$ – abelenky Jan 24 '15 at 0:06
  • $\begingroup$ Along the lines of what Peter said, yokes work very well for recovering from stalls. Throttles/thrust levers are also helpful. $\endgroup$ – reirab Jan 30 '15 at 6:48
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On modern airliners we have audible stall warnings (ranging in complexity from a blaring horn to a voice saying "STALL. STALL. STALL."), stick shakers, stick pushers, and in some aircraft sophisticated flight envelope protection systems (control software that simply won't allow the pilot to stall the aircraft).

When everything is working as designed these systems either make it very difficult to stall an aircraft (you would have to ignore the audible warning, ignore the stick shaker, and either override or overpower the stick pusher), or impossible to do so (flight-envelope protection).

When things are not working as designed - e.g. if the pitot (airspeed) and angle-of-attack systems malfunction these protective systems can become ineffective, however in such a scenario any other automated protection system that we would seek to implement would have similar challenges to overcome (if the flight-envelope protection system can't determine that the aircraft is in a stall how would the hypothetical "stall recovery" system know that it should do its thing?)

The idea of airframe parachutes - even a "spin recovery drogue" - for airliners has its own problems and is a largely impractical solution. (I won't rehash the reasons here, but they are well covered in the linked question.)

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  • $\begingroup$ "(if the flight-envelope protection system can't determine that the aircraft is in a stall how would the hypothetical "stall recovery" system know that it should do its thing?)" The scenario I was thinking of would be one where a pilot would make that decision. Of course, that would assume that, at some time during a long uncontrolled descent, the pilot would realize they are in a stall but could not find the means to get out of it. Your link was interesting but does not seem to apply to a system that would only be for changing the angle of attack, not slowing the descent. $\endgroup$ – Robert Holton Jan 23 '15 at 21:44
  • $\begingroup$ From my (limited) experience in human/machine interactions, I think a stick pusher is a BAD idea. When situations start to go badly, people get combative. They view the situation as "me vs. the machine". If the machine is pushing the stick forward, they try to pull the stick back. Which is, of course, the wrong response. $\endgroup$ – abelenky Jan 24 '15 at 0:08
  • $\begingroup$ @RobertHolton We already have a system which changes the angle of attack (the stick pusher literally pushes the stick forward, reducing the angle of attack). A parachute system would have to be triggered by the same logic (and there have been cases where stick pushers triggered when they really shouldn't have -- would you want a parachute deploying at the wrong moment in flight?) -- If we remove the computer from the equation and have the pilot decide when to pull the chute we're back in at "The pilot has to recognize the problem is a stall", at which point they don't need the chute… $\endgroup$ – voretaq7 Jan 24 '15 at 8:37
  • $\begingroup$ @abelenky: Airplane won't stall unless the pilot is pulling on the control column due to longitudinal stability, so the stick pusher just increases force that is already there and that the pilot should already consider a sign of loosing speed. But as the accidents show, when the pilots both lost situational awareness, the machine is not able to wake them up whatever it does. $\endgroup$ – Jan Hudec Jan 25 '15 at 11:18
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The real problem is complacency and over-reliance on technology. There is no technological fix for that.

Pilots have been made to believe that their computerized FCS will make stall impossible. When the system switches modes and the pilots do not become aware of this, they have in very few cases actively kept the aircraft in a stall, thinking they wouldn't stall, ever.

What is needed is better pilot training, and maybe less exposure to the propaganda from the aircraft manufacturers. Trusting the life of 300 people to a person who has never flown upside down, not to mention at bank angles of more than 60°, is reckless. In their race to ever lower cost the MBA types who run airlines today compare pilots to coach drivers and put as much effort in their education.

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  • $\begingroup$ With the demise of large air forces in large wars, it is probably doubtful that as many people as once did will ever get the experience in flying a large aircraft close to the edge as combat pilots have. $\endgroup$ – Robert Holton Jan 23 '15 at 21:48
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    $\begingroup$ @RobertHolton: It does not have to be a large aircraft. The point is to experience the sensory illusions, the reversed response to roll in inverted flight and learn to regain orientation in unusual attitudes. Which can be safely done in a higher-performance trainer, something like PC-9 or PC-21. $\endgroup$ – Jan Hudec Jan 25 '15 at 11:25
  • $\begingroup$ @JanHudec: Or a Zlin 226, at least in my case. Missing power can be replaced by kinetic energy if you tolerate longer climb sections in your training. $\endgroup$ – Peter Kämpf Jan 25 '15 at 13:30
  • $\begingroup$ @PeterKämpf Can you expand on why experience in inverted flight is helpful for flying an airliner? I'm not trying to be sarcastic; I'm just legitimately curious what the benefits there are, having never personally flown inverted. $\endgroup$ – reirab Jan 30 '15 at 6:58
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    $\begingroup$ @reirab: It is less about flying inverted, but getting into and out of unusual attitudes. I could as well say they need to spin - not one turn, but at least 3 or 5. It opens your mind and prepares you for unexpected situations. You know what to expect and what to do next. $\endgroup$ – Peter Kämpf Jan 30 '15 at 7:09

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