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












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I understand why passenger jets use software that overrides pilot inputs that might cause the jet to exceed the flight envelope. But why do passenger jet manufacturers design their planes with stall prevention systems? Shouldn't professional pilots be well aware that a stall is possible when the airspeed is too low, or the angle of attack is too high?










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  • 3




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    This isn't as simple as it sounds, and AF447 really set this in motion for the industry. The problem is that at differing altitudes your AoA between "flying" and "stall" can be extremely narrow. Couple that in with no visual references and a pilot may not know that the aircraft is stalling...
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    – Ron Beyer
    yesterday










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    Be aware, especially on the more advanced, larger aircraft, although the anti-stall systems do pull and act largely on their own against pilot input, 20lb's of force is roughly the industry standard (I believe from personal experience) to override this.
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    – Jihyun
    yesterday






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    @RonBeyer AF447 had such a system, but it had been disabled due to erroneous airspeed readings when the pitot tubes iced. If anything, AF447 is something of a cautionary tale of pilots becoming too reliant on such systems instead of knowing how to fly the airplane themselves.
    $endgroup$
    – reirab
    yesterday






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    Because stalls are really bad?
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    – David Richerby
    8 hours ago
















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I understand why passenger jets use software that overrides pilot inputs that might cause the jet to exceed the flight envelope. But why do passenger jet manufacturers design their planes with stall prevention systems? Shouldn't professional pilots be well aware that a stall is possible when the airspeed is too low, or the angle of attack is too high?










share|improve this question









$endgroup$








  • 3




    $begingroup$
    This isn't as simple as it sounds, and AF447 really set this in motion for the industry. The problem is that at differing altitudes your AoA between "flying" and "stall" can be extremely narrow. Couple that in with no visual references and a pilot may not know that the aircraft is stalling...
    $endgroup$
    – Ron Beyer
    yesterday










  • $begingroup$
    Be aware, especially on the more advanced, larger aircraft, although the anti-stall systems do pull and act largely on their own against pilot input, 20lb's of force is roughly the industry standard (I believe from personal experience) to override this.
    $endgroup$
    – Jihyun
    yesterday






  • 9




    $begingroup$
    @RonBeyer AF447 had such a system, but it had been disabled due to erroneous airspeed readings when the pitot tubes iced. If anything, AF447 is something of a cautionary tale of pilots becoming too reliant on such systems instead of knowing how to fly the airplane themselves.
    $endgroup$
    – reirab
    yesterday






  • 2




    $begingroup$
    Because stalls are really bad?
    $endgroup$
    – David Richerby
    8 hours ago














9












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$begingroup$


I understand why passenger jets use software that overrides pilot inputs that might cause the jet to exceed the flight envelope. But why do passenger jet manufacturers design their planes with stall prevention systems? Shouldn't professional pilots be well aware that a stall is possible when the airspeed is too low, or the angle of attack is too high?










share|improve this question









$endgroup$




I understand why passenger jets use software that overrides pilot inputs that might cause the jet to exceed the flight envelope. But why do passenger jet manufacturers design their planes with stall prevention systems? Shouldn't professional pilots be well aware that a stall is possible when the airspeed is too low, or the angle of attack is too high?







aircraft-design stall






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asked yesterday









rclocher3rclocher3

27128




27128








  • 3




    $begingroup$
    This isn't as simple as it sounds, and AF447 really set this in motion for the industry. The problem is that at differing altitudes your AoA between "flying" and "stall" can be extremely narrow. Couple that in with no visual references and a pilot may not know that the aircraft is stalling...
    $endgroup$
    – Ron Beyer
    yesterday










  • $begingroup$
    Be aware, especially on the more advanced, larger aircraft, although the anti-stall systems do pull and act largely on their own against pilot input, 20lb's of force is roughly the industry standard (I believe from personal experience) to override this.
    $endgroup$
    – Jihyun
    yesterday






  • 9




    $begingroup$
    @RonBeyer AF447 had such a system, but it had been disabled due to erroneous airspeed readings when the pitot tubes iced. If anything, AF447 is something of a cautionary tale of pilots becoming too reliant on such systems instead of knowing how to fly the airplane themselves.
    $endgroup$
    – reirab
    yesterday






  • 2




    $begingroup$
    Because stalls are really bad?
    $endgroup$
    – David Richerby
    8 hours ago














  • 3




    $begingroup$
    This isn't as simple as it sounds, and AF447 really set this in motion for the industry. The problem is that at differing altitudes your AoA between "flying" and "stall" can be extremely narrow. Couple that in with no visual references and a pilot may not know that the aircraft is stalling...
    $endgroup$
    – Ron Beyer
    yesterday










  • $begingroup$
    Be aware, especially on the more advanced, larger aircraft, although the anti-stall systems do pull and act largely on their own against pilot input, 20lb's of force is roughly the industry standard (I believe from personal experience) to override this.
    $endgroup$
    – Jihyun
    yesterday






  • 9




    $begingroup$
    @RonBeyer AF447 had such a system, but it had been disabled due to erroneous airspeed readings when the pitot tubes iced. If anything, AF447 is something of a cautionary tale of pilots becoming too reliant on such systems instead of knowing how to fly the airplane themselves.
    $endgroup$
    – reirab
    yesterday






  • 2




    $begingroup$
    Because stalls are really bad?
    $endgroup$
    – David Richerby
    8 hours ago








3




3




$begingroup$
This isn't as simple as it sounds, and AF447 really set this in motion for the industry. The problem is that at differing altitudes your AoA between "flying" and "stall" can be extremely narrow. Couple that in with no visual references and a pilot may not know that the aircraft is stalling...
$endgroup$
– Ron Beyer
yesterday




$begingroup$
This isn't as simple as it sounds, and AF447 really set this in motion for the industry. The problem is that at differing altitudes your AoA between "flying" and "stall" can be extremely narrow. Couple that in with no visual references and a pilot may not know that the aircraft is stalling...
$endgroup$
– Ron Beyer
yesterday












$begingroup$
Be aware, especially on the more advanced, larger aircraft, although the anti-stall systems do pull and act largely on their own against pilot input, 20lb's of force is roughly the industry standard (I believe from personal experience) to override this.
$endgroup$
– Jihyun
yesterday




$begingroup$
Be aware, especially on the more advanced, larger aircraft, although the anti-stall systems do pull and act largely on their own against pilot input, 20lb's of force is roughly the industry standard (I believe from personal experience) to override this.
$endgroup$
– Jihyun
yesterday




9




9




$begingroup$
@RonBeyer AF447 had such a system, but it had been disabled due to erroneous airspeed readings when the pitot tubes iced. If anything, AF447 is something of a cautionary tale of pilots becoming too reliant on such systems instead of knowing how to fly the airplane themselves.
$endgroup$
– reirab
yesterday




$begingroup$
@RonBeyer AF447 had such a system, but it had been disabled due to erroneous airspeed readings when the pitot tubes iced. If anything, AF447 is something of a cautionary tale of pilots becoming too reliant on such systems instead of knowing how to fly the airplane themselves.
$endgroup$
– reirab
yesterday




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Because stalls are really bad?
$endgroup$
– David Richerby
8 hours ago




$begingroup$
Because stalls are really bad?
$endgroup$
– David Richerby
8 hours ago










4 Answers
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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 signs?




  • Because accidents happen.

  • Because pilots are human and make mistakes.

  • Because when you're flying in the clouds with no visual references, it's easy to get confused.

  • Because even with stall warning & prevention systems in place, confused pilots will fight the system. AF 447






share|improve this answer









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    And because even with stall prevention systems, stalls are still a reality. That's how bad it is
    $endgroup$
    – Hanky Panky
    19 hours ago










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    To be fair the AF 447's stall prevention were disabled because of incorrect airspeed readings. In contrast, the Lion Air 737 crash was that it didn't get disabled... die if you do, die if you don't...
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    – Nelson
    18 hours ago










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    I believe some planes have a nose wing set at a steeper angle than the main wing, causing the nose to stall first, thus bringing the nose down before a real stall is reached. (See ainonline.com/sites/default/files/uploads/2018/07/… for an example of a nose wing, though I don't know its purpose on the Piaggo.)
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    – user3070485
    13 hours ago






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    @user3070485 that "nose wing" is called a canard, and yes, I believe you're correct. I would imagine that it's still possible to stall a canard winged aircraft, though that would make a good question of its own.
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    – FreeMan
    13 hours ago










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    @FreeMan It is still possible to stall a canard aircraft but most are designed as @ user3070485 mentioned where the canard will stall first. However this becomes a more difficult situation when you introduce leading and trailing edge devices which alter the stall characteristics of the wing. You can get a situation where the canard will stall first under certain configurations and where the wing will stall first under others.
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    – DJ319
    12 hours ago



















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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 strong physical cues prior to stall, like the whole airframe shaking, and good behaviour during a stall, like a good natural pitch over tendency with immediate unstalling of the wing, can get away without stall warning and prevention systems.



Transport aircraft with highly loaded wings and high performance airfoils may have poor behaviour before the stall (no buffeting or shaking), and poor recovery performance after, and need a little help. The airfoils used for airplanes that fly at near trans-sonic speeds tend to suffer from this because they tend to stall from the leading edge, at which point the wing stops lifting all at once, and there is often no prior buffeting or shaking.



The earlier supercritical (higher critical mach#) airfoils developed in the 70s were especially bad for this because they developed a flow separation bubble just aft of the leading edge at high angles of attack, due to the profile that was used to manage the formation of shock waves (the Challenger business jet and CRJ200 Regional Jet is typical). You do not want to experience the natural stall on such an aircraft and some kind of system has to be in place as a backup for mishandling of the airplane by the pilot.



For airplanes with mechanical/hydraulic controls, to provide a tactile warning as a substitute or supplement for the airplane shaking (pre-stall buffet), stick shakers are used, which is just a motor with an eccentric weight on the control column. If the post stall behaviour (not much natural pitch over, or worse, settling into an unrecoverable deep stall) is poor, a stick pusher is installed to give the control column a shove just before the natural stall occurs. The stall protection system calculates when to do all this.



Most high performance aircraft use shakers, and some use stick pushers. With FBW, the FBW computers intervene directly within the control loop to achieve the same end without having to shake or push the controls.






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    In the Air France 447 accident, the Airbus A330 only had a sound warning, with no physical warning, and the plane was clearly built so that it can't "get away" without a warning. Why is that?
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    – gparyani
    yesterday






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    The last sentence in my post applies. It's a FBW airplane with side sticks and the computers control the airplane at the margins, only letting the pilot input go so far, with an aural warning when things are getting close, but the computers will simply not allow the pilot to go all the way into an aerodynamic stall. 447 wasn't stalled in the aerodynamic sense on its ride down, it was being held at the maximum attitude the computers would allow, not quite stalled, because the right seater was in a mental fog panic mode holding the right side stick fully aft the entire ride down.
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    – John K
    yesterday






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    And the guy in the left seat was in a similar mentally saturated state and didn't think to hit the left seater's override button to pitch the plane over. He pushed his stick forward a few times but this only gets a 50% input because the two inputs are averaged, unless he overrides, and a 50% input wasn't enough to recover from the low speed mush descent.
    $endgroup$
    – John K
    yesterday








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    The cockpit recorded did record the sound of the audible stall warning for the entire decent, so I would agree that the pilots were in a mental fog and completely did not register what they needed to do.
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    – Nelson
    19 hours ago










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    This is one of the biggest problems in the industry. Pilots go through fast track schools and end up in airliners that are AP engaged 95% of the time and have never really learned how to fly, like the guy who learned on gliders, flew in the bush, flew multi-engine s**boxes hauling crap, for a number or years, to the point where the basic fundamental instincts are burned in. They know what to do, but it's not sufficiently internalized, so when weird stuff happens and the stress level goes to 11, they freeze in confusion.
    $endgroup$
    – John K
    11 hours ago



















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You said you understand systems to prevent the airplane from exceeding the flight envelope. Stall is just another boundary of the flight envelope. The rest of the envelope limitations are listed in the flight manual as well. Shouldn't pilots know not to stall the airplane, just as they know not to over-stress it, or exceed other limitations? Of course.



But humans make mistakes, they can get distracted or disoriented. And just as there's little benefit to allowing a pilot to rip the wings off the plane by pitching too fast, there's little benefit from allowing the plane to stall.



Here is a selection of aircraft that have crashed due to stalls.



South Airlines Flight 8971



Air Algérie 5017



AirAsia QZ8501



Thai Airways International flight 261



Vladivostokavia Flight 352



N452DA



Yemenia Airways Flight 626



If stall protection systems are implemented and functioning properly, they can prevent issues. Here are just a few instances where stall protection worked as intended:



GoAir 338



Air France 7662



Jetstar 248






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    On the flip size, I'm curious what would have happened to Asiana 214 if it had had a stall prevention system. If I'm remembering correctly, they did stall (or at least very nearly stall) on very short final while trying to make the runway. If a stall prevention system had prevented them from raising the nose, would they have hit the nose on the seawall instead of the tail? That seems like it could have been a bad situation a whole lot worse.
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    – reirab
    yesterday






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    @reirab True. On the other hand, if you allow the aircraft to run into two limits simultaneously (out of room and out of speed), there is not much anyone can do. You could argue the „opposite“ safety system, too, and say an automatic terrain escape manoeuvre would be fantastic, except with Asiana 214, it could have worsened the stall...
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    – Cpt Reynolds
    yesterday






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    @CptReynolds Agreed. The root source of the problem was, of course, lack of energy on very short final, which was totally a result of pilot error. But, given that situation, they pretty much had to choose how they were going to crash rather than whether they were going to crash. In that sort of situation, I'd personally prefer a human pilot who can look out the window and make rapid judgments based on the exact situation in control. It's just not the sort of thing that's easy to account for when you're designing a computer program.
    $endgroup$
    – reirab
    yesterday










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    I suggest to add Colgan 3407 to the list.
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    – Martin Argerami
    14 hours ago



















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The relevant certification requirements, set by the FAA/JAA/CAA etc require that a "large aircraft" that is capable of stalling has an automatic stall warning and recovery system. So the simple answer is "because the rule of law says so".



Maybe you could think about re-phrasing the question to ask why the traditional stick shaker and pusher, with a long and satisfactory history, were not used? I expect that Boeing will be having to answer that question to the authorities.






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    4 Answers
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    4 Answers
    4






    active

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    24












    $begingroup$

    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 signs?




    • Because accidents happen.

    • Because pilots are human and make mistakes.

    • Because when you're flying in the clouds with no visual references, it's easy to get confused.

    • Because even with stall warning & prevention systems in place, confused pilots will fight the system. AF 447






    share|improve this answer









    $endgroup$













    • $begingroup$
      And because even with stall prevention systems, stalls are still a reality. That's how bad it is
      $endgroup$
      – Hanky Panky
      19 hours ago










    • $begingroup$
      To be fair the AF 447's stall prevention were disabled because of incorrect airspeed readings. In contrast, the Lion Air 737 crash was that it didn't get disabled... die if you do, die if you don't...
      $endgroup$
      – Nelson
      18 hours ago










    • $begingroup$
      I believe some planes have a nose wing set at a steeper angle than the main wing, causing the nose to stall first, thus bringing the nose down before a real stall is reached. (See ainonline.com/sites/default/files/uploads/2018/07/… for an example of a nose wing, though I don't know its purpose on the Piaggo.)
      $endgroup$
      – user3070485
      13 hours ago






    • 1




      $begingroup$
      @user3070485 that "nose wing" is called a canard, and yes, I believe you're correct. I would imagine that it's still possible to stall a canard winged aircraft, though that would make a good question of its own.
      $endgroup$
      – FreeMan
      13 hours ago










    • $begingroup$
      @FreeMan It is still possible to stall a canard aircraft but most are designed as @ user3070485 mentioned where the canard will stall first. However this becomes a more difficult situation when you introduce leading and trailing edge devices which alter the stall characteristics of the wing. You can get a situation where the canard will stall first under certain configurations and where the wing will stall first under others.
      $endgroup$
      – DJ319
      12 hours ago
















    24












    $begingroup$

    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 signs?




    • Because accidents happen.

    • Because pilots are human and make mistakes.

    • Because when you're flying in the clouds with no visual references, it's easy to get confused.

    • Because even with stall warning & prevention systems in place, confused pilots will fight the system. AF 447






    share|improve this answer









    $endgroup$













    • $begingroup$
      And because even with stall prevention systems, stalls are still a reality. That's how bad it is
      $endgroup$
      – Hanky Panky
      19 hours ago










    • $begingroup$
      To be fair the AF 447's stall prevention were disabled because of incorrect airspeed readings. In contrast, the Lion Air 737 crash was that it didn't get disabled... die if you do, die if you don't...
      $endgroup$
      – Nelson
      18 hours ago










    • $begingroup$
      I believe some planes have a nose wing set at a steeper angle than the main wing, causing the nose to stall first, thus bringing the nose down before a real stall is reached. (See ainonline.com/sites/default/files/uploads/2018/07/… for an example of a nose wing, though I don't know its purpose on the Piaggo.)
      $endgroup$
      – user3070485
      13 hours ago






    • 1




      $begingroup$
      @user3070485 that "nose wing" is called a canard, and yes, I believe you're correct. I would imagine that it's still possible to stall a canard winged aircraft, though that would make a good question of its own.
      $endgroup$
      – FreeMan
      13 hours ago










    • $begingroup$
      @FreeMan It is still possible to stall a canard aircraft but most are designed as @ user3070485 mentioned where the canard will stall first. However this becomes a more difficult situation when you introduce leading and trailing edge devices which alter the stall characteristics of the wing. You can get a situation where the canard will stall first under certain configurations and where the wing will stall first under others.
      $endgroup$
      – DJ319
      12 hours ago














    24












    24








    24





    $begingroup$

    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 signs?




    • Because accidents happen.

    • Because pilots are human and make mistakes.

    • Because when you're flying in the clouds with no visual references, it's easy to get confused.

    • Because even with stall warning & prevention systems in place, confused pilots will fight the system. AF 447






    share|improve this answer









    $endgroup$



    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 signs?




    • Because accidents happen.

    • Because pilots are human and make mistakes.

    • Because when you're flying in the clouds with no visual references, it's easy to get confused.

    • Because even with stall warning & prevention systems in place, confused pilots will fight the system. AF 447







    share|improve this answer












    share|improve this answer



    share|improve this answer










    answered yesterday









    FreeManFreeMan

    7,4351057125




    7,4351057125












    • $begingroup$
      And because even with stall prevention systems, stalls are still a reality. That's how bad it is
      $endgroup$
      – Hanky Panky
      19 hours ago










    • $begingroup$
      To be fair the AF 447's stall prevention were disabled because of incorrect airspeed readings. In contrast, the Lion Air 737 crash was that it didn't get disabled... die if you do, die if you don't...
      $endgroup$
      – Nelson
      18 hours ago










    • $begingroup$
      I believe some planes have a nose wing set at a steeper angle than the main wing, causing the nose to stall first, thus bringing the nose down before a real stall is reached. (See ainonline.com/sites/default/files/uploads/2018/07/… for an example of a nose wing, though I don't know its purpose on the Piaggo.)
      $endgroup$
      – user3070485
      13 hours ago






    • 1




      $begingroup$
      @user3070485 that "nose wing" is called a canard, and yes, I believe you're correct. I would imagine that it's still possible to stall a canard winged aircraft, though that would make a good question of its own.
      $endgroup$
      – FreeMan
      13 hours ago










    • $begingroup$
      @FreeMan It is still possible to stall a canard aircraft but most are designed as @ user3070485 mentioned where the canard will stall first. However this becomes a more difficult situation when you introduce leading and trailing edge devices which alter the stall characteristics of the wing. You can get a situation where the canard will stall first under certain configurations and where the wing will stall first under others.
      $endgroup$
      – DJ319
      12 hours ago


















    • $begingroup$
      And because even with stall prevention systems, stalls are still a reality. That's how bad it is
      $endgroup$
      – Hanky Panky
      19 hours ago










    • $begingroup$
      To be fair the AF 447's stall prevention were disabled because of incorrect airspeed readings. In contrast, the Lion Air 737 crash was that it didn't get disabled... die if you do, die if you don't...
      $endgroup$
      – Nelson
      18 hours ago










    • $begingroup$
      I believe some planes have a nose wing set at a steeper angle than the main wing, causing the nose to stall first, thus bringing the nose down before a real stall is reached. (See ainonline.com/sites/default/files/uploads/2018/07/… for an example of a nose wing, though I don't know its purpose on the Piaggo.)
      $endgroup$
      – user3070485
      13 hours ago






    • 1




      $begingroup$
      @user3070485 that "nose wing" is called a canard, and yes, I believe you're correct. I would imagine that it's still possible to stall a canard winged aircraft, though that would make a good question of its own.
      $endgroup$
      – FreeMan
      13 hours ago










    • $begingroup$
      @FreeMan It is still possible to stall a canard aircraft but most are designed as @ user3070485 mentioned where the canard will stall first. However this becomes a more difficult situation when you introduce leading and trailing edge devices which alter the stall characteristics of the wing. You can get a situation where the canard will stall first under certain configurations and where the wing will stall first under others.
      $endgroup$
      – DJ319
      12 hours ago
















    $begingroup$
    And because even with stall prevention systems, stalls are still a reality. That's how bad it is
    $endgroup$
    – Hanky Panky
    19 hours ago




    $begingroup$
    And because even with stall prevention systems, stalls are still a reality. That's how bad it is
    $endgroup$
    – Hanky Panky
    19 hours ago












    $begingroup$
    To be fair the AF 447's stall prevention were disabled because of incorrect airspeed readings. In contrast, the Lion Air 737 crash was that it didn't get disabled... die if you do, die if you don't...
    $endgroup$
    – Nelson
    18 hours ago




    $begingroup$
    To be fair the AF 447's stall prevention were disabled because of incorrect airspeed readings. In contrast, the Lion Air 737 crash was that it didn't get disabled... die if you do, die if you don't...
    $endgroup$
    – Nelson
    18 hours ago












    $begingroup$
    I believe some planes have a nose wing set at a steeper angle than the main wing, causing the nose to stall first, thus bringing the nose down before a real stall is reached. (See ainonline.com/sites/default/files/uploads/2018/07/… for an example of a nose wing, though I don't know its purpose on the Piaggo.)
    $endgroup$
    – user3070485
    13 hours ago




    $begingroup$
    I believe some planes have a nose wing set at a steeper angle than the main wing, causing the nose to stall first, thus bringing the nose down before a real stall is reached. (See ainonline.com/sites/default/files/uploads/2018/07/… for an example of a nose wing, though I don't know its purpose on the Piaggo.)
    $endgroup$
    – user3070485
    13 hours ago




    1




    1




    $begingroup$
    @user3070485 that "nose wing" is called a canard, and yes, I believe you're correct. I would imagine that it's still possible to stall a canard winged aircraft, though that would make a good question of its own.
    $endgroup$
    – FreeMan
    13 hours ago




    $begingroup$
    @user3070485 that "nose wing" is called a canard, and yes, I believe you're correct. I would imagine that it's still possible to stall a canard winged aircraft, though that would make a good question of its own.
    $endgroup$
    – FreeMan
    13 hours ago












    $begingroup$
    @FreeMan It is still possible to stall a canard aircraft but most are designed as @ user3070485 mentioned where the canard will stall first. However this becomes a more difficult situation when you introduce leading and trailing edge devices which alter the stall characteristics of the wing. You can get a situation where the canard will stall first under certain configurations and where the wing will stall first under others.
    $endgroup$
    – DJ319
    12 hours ago




    $begingroup$
    @FreeMan It is still possible to stall a canard aircraft but most are designed as @ user3070485 mentioned where the canard will stall first. However this becomes a more difficult situation when you introduce leading and trailing edge devices which alter the stall characteristics of the wing. You can get a situation where the canard will stall first under certain configurations and where the wing will stall first under others.
    $endgroup$
    – DJ319
    12 hours ago











    21












    $begingroup$

    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 strong physical cues prior to stall, like the whole airframe shaking, and good behaviour during a stall, like a good natural pitch over tendency with immediate unstalling of the wing, can get away without stall warning and prevention systems.



    Transport aircraft with highly loaded wings and high performance airfoils may have poor behaviour before the stall (no buffeting or shaking), and poor recovery performance after, and need a little help. The airfoils used for airplanes that fly at near trans-sonic speeds tend to suffer from this because they tend to stall from the leading edge, at which point the wing stops lifting all at once, and there is often no prior buffeting or shaking.



    The earlier supercritical (higher critical mach#) airfoils developed in the 70s were especially bad for this because they developed a flow separation bubble just aft of the leading edge at high angles of attack, due to the profile that was used to manage the formation of shock waves (the Challenger business jet and CRJ200 Regional Jet is typical). You do not want to experience the natural stall on such an aircraft and some kind of system has to be in place as a backup for mishandling of the airplane by the pilot.



    For airplanes with mechanical/hydraulic controls, to provide a tactile warning as a substitute or supplement for the airplane shaking (pre-stall buffet), stick shakers are used, which is just a motor with an eccentric weight on the control column. If the post stall behaviour (not much natural pitch over, or worse, settling into an unrecoverable deep stall) is poor, a stick pusher is installed to give the control column a shove just before the natural stall occurs. The stall protection system calculates when to do all this.



    Most high performance aircraft use shakers, and some use stick pushers. With FBW, the FBW computers intervene directly within the control loop to achieve the same end without having to shake or push the controls.






    share|improve this answer









    $endgroup$













    • $begingroup$
      In the Air France 447 accident, the Airbus A330 only had a sound warning, with no physical warning, and the plane was clearly built so that it can't "get away" without a warning. Why is that?
      $endgroup$
      – gparyani
      yesterday






    • 2




      $begingroup$
      The last sentence in my post applies. It's a FBW airplane with side sticks and the computers control the airplane at the margins, only letting the pilot input go so far, with an aural warning when things are getting close, but the computers will simply not allow the pilot to go all the way into an aerodynamic stall. 447 wasn't stalled in the aerodynamic sense on its ride down, it was being held at the maximum attitude the computers would allow, not quite stalled, because the right seater was in a mental fog panic mode holding the right side stick fully aft the entire ride down.
      $endgroup$
      – John K
      yesterday






    • 2




      $begingroup$
      And the guy in the left seat was in a similar mentally saturated state and didn't think to hit the left seater's override button to pitch the plane over. He pushed his stick forward a few times but this only gets a 50% input because the two inputs are averaged, unless he overrides, and a 50% input wasn't enough to recover from the low speed mush descent.
      $endgroup$
      – John K
      yesterday








    • 1




      $begingroup$
      The cockpit recorded did record the sound of the audible stall warning for the entire decent, so I would agree that the pilots were in a mental fog and completely did not register what they needed to do.
      $endgroup$
      – Nelson
      19 hours ago










    • $begingroup$
      This is one of the biggest problems in the industry. Pilots go through fast track schools and end up in airliners that are AP engaged 95% of the time and have never really learned how to fly, like the guy who learned on gliders, flew in the bush, flew multi-engine s**boxes hauling crap, for a number or years, to the point where the basic fundamental instincts are burned in. They know what to do, but it's not sufficiently internalized, so when weird stuff happens and the stress level goes to 11, they freeze in confusion.
      $endgroup$
      – John K
      11 hours ago
















    21












    $begingroup$

    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 strong physical cues prior to stall, like the whole airframe shaking, and good behaviour during a stall, like a good natural pitch over tendency with immediate unstalling of the wing, can get away without stall warning and prevention systems.



    Transport aircraft with highly loaded wings and high performance airfoils may have poor behaviour before the stall (no buffeting or shaking), and poor recovery performance after, and need a little help. The airfoils used for airplanes that fly at near trans-sonic speeds tend to suffer from this because they tend to stall from the leading edge, at which point the wing stops lifting all at once, and there is often no prior buffeting or shaking.



    The earlier supercritical (higher critical mach#) airfoils developed in the 70s were especially bad for this because they developed a flow separation bubble just aft of the leading edge at high angles of attack, due to the profile that was used to manage the formation of shock waves (the Challenger business jet and CRJ200 Regional Jet is typical). You do not want to experience the natural stall on such an aircraft and some kind of system has to be in place as a backup for mishandling of the airplane by the pilot.



    For airplanes with mechanical/hydraulic controls, to provide a tactile warning as a substitute or supplement for the airplane shaking (pre-stall buffet), stick shakers are used, which is just a motor with an eccentric weight on the control column. If the post stall behaviour (not much natural pitch over, or worse, settling into an unrecoverable deep stall) is poor, a stick pusher is installed to give the control column a shove just before the natural stall occurs. The stall protection system calculates when to do all this.



    Most high performance aircraft use shakers, and some use stick pushers. With FBW, the FBW computers intervene directly within the control loop to achieve the same end without having to shake or push the controls.






    share|improve this answer









    $endgroup$













    • $begingroup$
      In the Air France 447 accident, the Airbus A330 only had a sound warning, with no physical warning, and the plane was clearly built so that it can't "get away" without a warning. Why is that?
      $endgroup$
      – gparyani
      yesterday






    • 2




      $begingroup$
      The last sentence in my post applies. It's a FBW airplane with side sticks and the computers control the airplane at the margins, only letting the pilot input go so far, with an aural warning when things are getting close, but the computers will simply not allow the pilot to go all the way into an aerodynamic stall. 447 wasn't stalled in the aerodynamic sense on its ride down, it was being held at the maximum attitude the computers would allow, not quite stalled, because the right seater was in a mental fog panic mode holding the right side stick fully aft the entire ride down.
      $endgroup$
      – John K
      yesterday






    • 2




      $begingroup$
      And the guy in the left seat was in a similar mentally saturated state and didn't think to hit the left seater's override button to pitch the plane over. He pushed his stick forward a few times but this only gets a 50% input because the two inputs are averaged, unless he overrides, and a 50% input wasn't enough to recover from the low speed mush descent.
      $endgroup$
      – John K
      yesterday








    • 1




      $begingroup$
      The cockpit recorded did record the sound of the audible stall warning for the entire decent, so I would agree that the pilots were in a mental fog and completely did not register what they needed to do.
      $endgroup$
      – Nelson
      19 hours ago










    • $begingroup$
      This is one of the biggest problems in the industry. Pilots go through fast track schools and end up in airliners that are AP engaged 95% of the time and have never really learned how to fly, like the guy who learned on gliders, flew in the bush, flew multi-engine s**boxes hauling crap, for a number or years, to the point where the basic fundamental instincts are burned in. They know what to do, but it's not sufficiently internalized, so when weird stuff happens and the stress level goes to 11, they freeze in confusion.
      $endgroup$
      – John K
      11 hours ago














    21












    21








    21





    $begingroup$

    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 strong physical cues prior to stall, like the whole airframe shaking, and good behaviour during a stall, like a good natural pitch over tendency with immediate unstalling of the wing, can get away without stall warning and prevention systems.



    Transport aircraft with highly loaded wings and high performance airfoils may have poor behaviour before the stall (no buffeting or shaking), and poor recovery performance after, and need a little help. The airfoils used for airplanes that fly at near trans-sonic speeds tend to suffer from this because they tend to stall from the leading edge, at which point the wing stops lifting all at once, and there is often no prior buffeting or shaking.



    The earlier supercritical (higher critical mach#) airfoils developed in the 70s were especially bad for this because they developed a flow separation bubble just aft of the leading edge at high angles of attack, due to the profile that was used to manage the formation of shock waves (the Challenger business jet and CRJ200 Regional Jet is typical). You do not want to experience the natural stall on such an aircraft and some kind of system has to be in place as a backup for mishandling of the airplane by the pilot.



    For airplanes with mechanical/hydraulic controls, to provide a tactile warning as a substitute or supplement for the airplane shaking (pre-stall buffet), stick shakers are used, which is just a motor with an eccentric weight on the control column. If the post stall behaviour (not much natural pitch over, or worse, settling into an unrecoverable deep stall) is poor, a stick pusher is installed to give the control column a shove just before the natural stall occurs. The stall protection system calculates when to do all this.



    Most high performance aircraft use shakers, and some use stick pushers. With FBW, the FBW computers intervene directly within the control loop to achieve the same end without having to shake or push the controls.






    share|improve this answer









    $endgroup$



    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 strong physical cues prior to stall, like the whole airframe shaking, and good behaviour during a stall, like a good natural pitch over tendency with immediate unstalling of the wing, can get away without stall warning and prevention systems.



    Transport aircraft with highly loaded wings and high performance airfoils may have poor behaviour before the stall (no buffeting or shaking), and poor recovery performance after, and need a little help. The airfoils used for airplanes that fly at near trans-sonic speeds tend to suffer from this because they tend to stall from the leading edge, at which point the wing stops lifting all at once, and there is often no prior buffeting or shaking.



    The earlier supercritical (higher critical mach#) airfoils developed in the 70s were especially bad for this because they developed a flow separation bubble just aft of the leading edge at high angles of attack, due to the profile that was used to manage the formation of shock waves (the Challenger business jet and CRJ200 Regional Jet is typical). You do not want to experience the natural stall on such an aircraft and some kind of system has to be in place as a backup for mishandling of the airplane by the pilot.



    For airplanes with mechanical/hydraulic controls, to provide a tactile warning as a substitute or supplement for the airplane shaking (pre-stall buffet), stick shakers are used, which is just a motor with an eccentric weight on the control column. If the post stall behaviour (not much natural pitch over, or worse, settling into an unrecoverable deep stall) is poor, a stick pusher is installed to give the control column a shove just before the natural stall occurs. The stall protection system calculates when to do all this.



    Most high performance aircraft use shakers, and some use stick pushers. With FBW, the FBW computers intervene directly within the control loop to achieve the same end without having to shake or push the controls.







    share|improve this answer












    share|improve this answer



    share|improve this answer










    answered yesterday









    John KJohn K

    21.5k13064




    21.5k13064












    • $begingroup$
      In the Air France 447 accident, the Airbus A330 only had a sound warning, with no physical warning, and the plane was clearly built so that it can't "get away" without a warning. Why is that?
      $endgroup$
      – gparyani
      yesterday






    • 2




      $begingroup$
      The last sentence in my post applies. It's a FBW airplane with side sticks and the computers control the airplane at the margins, only letting the pilot input go so far, with an aural warning when things are getting close, but the computers will simply not allow the pilot to go all the way into an aerodynamic stall. 447 wasn't stalled in the aerodynamic sense on its ride down, it was being held at the maximum attitude the computers would allow, not quite stalled, because the right seater was in a mental fog panic mode holding the right side stick fully aft the entire ride down.
      $endgroup$
      – John K
      yesterday






    • 2




      $begingroup$
      And the guy in the left seat was in a similar mentally saturated state and didn't think to hit the left seater's override button to pitch the plane over. He pushed his stick forward a few times but this only gets a 50% input because the two inputs are averaged, unless he overrides, and a 50% input wasn't enough to recover from the low speed mush descent.
      $endgroup$
      – John K
      yesterday








    • 1




      $begingroup$
      The cockpit recorded did record the sound of the audible stall warning for the entire decent, so I would agree that the pilots were in a mental fog and completely did not register what they needed to do.
      $endgroup$
      – Nelson
      19 hours ago










    • $begingroup$
      This is one of the biggest problems in the industry. Pilots go through fast track schools and end up in airliners that are AP engaged 95% of the time and have never really learned how to fly, like the guy who learned on gliders, flew in the bush, flew multi-engine s**boxes hauling crap, for a number or years, to the point where the basic fundamental instincts are burned in. They know what to do, but it's not sufficiently internalized, so when weird stuff happens and the stress level goes to 11, they freeze in confusion.
      $endgroup$
      – John K
      11 hours ago


















    • $begingroup$
      In the Air France 447 accident, the Airbus A330 only had a sound warning, with no physical warning, and the plane was clearly built so that it can't "get away" without a warning. Why is that?
      $endgroup$
      – gparyani
      yesterday






    • 2




      $begingroup$
      The last sentence in my post applies. It's a FBW airplane with side sticks and the computers control the airplane at the margins, only letting the pilot input go so far, with an aural warning when things are getting close, but the computers will simply not allow the pilot to go all the way into an aerodynamic stall. 447 wasn't stalled in the aerodynamic sense on its ride down, it was being held at the maximum attitude the computers would allow, not quite stalled, because the right seater was in a mental fog panic mode holding the right side stick fully aft the entire ride down.
      $endgroup$
      – John K
      yesterday






    • 2




      $begingroup$
      And the guy in the left seat was in a similar mentally saturated state and didn't think to hit the left seater's override button to pitch the plane over. He pushed his stick forward a few times but this only gets a 50% input because the two inputs are averaged, unless he overrides, and a 50% input wasn't enough to recover from the low speed mush descent.
      $endgroup$
      – John K
      yesterday








    • 1




      $begingroup$
      The cockpit recorded did record the sound of the audible stall warning for the entire decent, so I would agree that the pilots were in a mental fog and completely did not register what they needed to do.
      $endgroup$
      – Nelson
      19 hours ago










    • $begingroup$
      This is one of the biggest problems in the industry. Pilots go through fast track schools and end up in airliners that are AP engaged 95% of the time and have never really learned how to fly, like the guy who learned on gliders, flew in the bush, flew multi-engine s**boxes hauling crap, for a number or years, to the point where the basic fundamental instincts are burned in. They know what to do, but it's not sufficiently internalized, so when weird stuff happens and the stress level goes to 11, they freeze in confusion.
      $endgroup$
      – John K
      11 hours ago
















    $begingroup$
    In the Air France 447 accident, the Airbus A330 only had a sound warning, with no physical warning, and the plane was clearly built so that it can't "get away" without a warning. Why is that?
    $endgroup$
    – gparyani
    yesterday




    $begingroup$
    In the Air France 447 accident, the Airbus A330 only had a sound warning, with no physical warning, and the plane was clearly built so that it can't "get away" without a warning. Why is that?
    $endgroup$
    – gparyani
    yesterday




    2




    2




    $begingroup$
    The last sentence in my post applies. It's a FBW airplane with side sticks and the computers control the airplane at the margins, only letting the pilot input go so far, with an aural warning when things are getting close, but the computers will simply not allow the pilot to go all the way into an aerodynamic stall. 447 wasn't stalled in the aerodynamic sense on its ride down, it was being held at the maximum attitude the computers would allow, not quite stalled, because the right seater was in a mental fog panic mode holding the right side stick fully aft the entire ride down.
    $endgroup$
    – John K
    yesterday




    $begingroup$
    The last sentence in my post applies. It's a FBW airplane with side sticks and the computers control the airplane at the margins, only letting the pilot input go so far, with an aural warning when things are getting close, but the computers will simply not allow the pilot to go all the way into an aerodynamic stall. 447 wasn't stalled in the aerodynamic sense on its ride down, it was being held at the maximum attitude the computers would allow, not quite stalled, because the right seater was in a mental fog panic mode holding the right side stick fully aft the entire ride down.
    $endgroup$
    – John K
    yesterday




    2




    2




    $begingroup$
    And the guy in the left seat was in a similar mentally saturated state and didn't think to hit the left seater's override button to pitch the plane over. He pushed his stick forward a few times but this only gets a 50% input because the two inputs are averaged, unless he overrides, and a 50% input wasn't enough to recover from the low speed mush descent.
    $endgroup$
    – John K
    yesterday






    $begingroup$
    And the guy in the left seat was in a similar mentally saturated state and didn't think to hit the left seater's override button to pitch the plane over. He pushed his stick forward a few times but this only gets a 50% input because the two inputs are averaged, unless he overrides, and a 50% input wasn't enough to recover from the low speed mush descent.
    $endgroup$
    – John K
    yesterday






    1




    1




    $begingroup$
    The cockpit recorded did record the sound of the audible stall warning for the entire decent, so I would agree that the pilots were in a mental fog and completely did not register what they needed to do.
    $endgroup$
    – Nelson
    19 hours ago




    $begingroup$
    The cockpit recorded did record the sound of the audible stall warning for the entire decent, so I would agree that the pilots were in a mental fog and completely did not register what they needed to do.
    $endgroup$
    – Nelson
    19 hours ago












    $begingroup$
    This is one of the biggest problems in the industry. Pilots go through fast track schools and end up in airliners that are AP engaged 95% of the time and have never really learned how to fly, like the guy who learned on gliders, flew in the bush, flew multi-engine s**boxes hauling crap, for a number or years, to the point where the basic fundamental instincts are burned in. They know what to do, but it's not sufficiently internalized, so when weird stuff happens and the stress level goes to 11, they freeze in confusion.
    $endgroup$
    – John K
    11 hours ago




    $begingroup$
    This is one of the biggest problems in the industry. Pilots go through fast track schools and end up in airliners that are AP engaged 95% of the time and have never really learned how to fly, like the guy who learned on gliders, flew in the bush, flew multi-engine s**boxes hauling crap, for a number or years, to the point where the basic fundamental instincts are burned in. They know what to do, but it's not sufficiently internalized, so when weird stuff happens and the stress level goes to 11, they freeze in confusion.
    $endgroup$
    – John K
    11 hours ago











    11












    $begingroup$

    You said you understand systems to prevent the airplane from exceeding the flight envelope. Stall is just another boundary of the flight envelope. The rest of the envelope limitations are listed in the flight manual as well. Shouldn't pilots know not to stall the airplane, just as they know not to over-stress it, or exceed other limitations? Of course.



    But humans make mistakes, they can get distracted or disoriented. And just as there's little benefit to allowing a pilot to rip the wings off the plane by pitching too fast, there's little benefit from allowing the plane to stall.



    Here is a selection of aircraft that have crashed due to stalls.



    South Airlines Flight 8971



    Air Algérie 5017



    AirAsia QZ8501



    Thai Airways International flight 261



    Vladivostokavia Flight 352



    N452DA



    Yemenia Airways Flight 626



    If stall protection systems are implemented and functioning properly, they can prevent issues. Here are just a few instances where stall protection worked as intended:



    GoAir 338



    Air France 7662



    Jetstar 248






    share|improve this answer









    $endgroup$









    • 1




      $begingroup$
      On the flip size, I'm curious what would have happened to Asiana 214 if it had had a stall prevention system. If I'm remembering correctly, they did stall (or at least very nearly stall) on very short final while trying to make the runway. If a stall prevention system had prevented them from raising the nose, would they have hit the nose on the seawall instead of the tail? That seems like it could have been a bad situation a whole lot worse.
      $endgroup$
      – reirab
      yesterday






    • 1




      $begingroup$
      @reirab True. On the other hand, if you allow the aircraft to run into two limits simultaneously (out of room and out of speed), there is not much anyone can do. You could argue the „opposite“ safety system, too, and say an automatic terrain escape manoeuvre would be fantastic, except with Asiana 214, it could have worsened the stall...
      $endgroup$
      – Cpt Reynolds
      yesterday






    • 2




      $begingroup$
      @CptReynolds Agreed. The root source of the problem was, of course, lack of energy on very short final, which was totally a result of pilot error. But, given that situation, they pretty much had to choose how they were going to crash rather than whether they were going to crash. In that sort of situation, I'd personally prefer a human pilot who can look out the window and make rapid judgments based on the exact situation in control. It's just not the sort of thing that's easy to account for when you're designing a computer program.
      $endgroup$
      – reirab
      yesterday










    • $begingroup$
      I suggest to add Colgan 3407 to the list.
      $endgroup$
      – Martin Argerami
      14 hours ago
















    11












    $begingroup$

    You said you understand systems to prevent the airplane from exceeding the flight envelope. Stall is just another boundary of the flight envelope. The rest of the envelope limitations are listed in the flight manual as well. Shouldn't pilots know not to stall the airplane, just as they know not to over-stress it, or exceed other limitations? Of course.



    But humans make mistakes, they can get distracted or disoriented. And just as there's little benefit to allowing a pilot to rip the wings off the plane by pitching too fast, there's little benefit from allowing the plane to stall.



    Here is a selection of aircraft that have crashed due to stalls.



    South Airlines Flight 8971



    Air Algérie 5017



    AirAsia QZ8501



    Thai Airways International flight 261



    Vladivostokavia Flight 352



    N452DA



    Yemenia Airways Flight 626



    If stall protection systems are implemented and functioning properly, they can prevent issues. Here are just a few instances where stall protection worked as intended:



    GoAir 338



    Air France 7662



    Jetstar 248






    share|improve this answer









    $endgroup$









    • 1




      $begingroup$
      On the flip size, I'm curious what would have happened to Asiana 214 if it had had a stall prevention system. If I'm remembering correctly, they did stall (or at least very nearly stall) on very short final while trying to make the runway. If a stall prevention system had prevented them from raising the nose, would they have hit the nose on the seawall instead of the tail? That seems like it could have been a bad situation a whole lot worse.
      $endgroup$
      – reirab
      yesterday






    • 1




      $begingroup$
      @reirab True. On the other hand, if you allow the aircraft to run into two limits simultaneously (out of room and out of speed), there is not much anyone can do. You could argue the „opposite“ safety system, too, and say an automatic terrain escape manoeuvre would be fantastic, except with Asiana 214, it could have worsened the stall...
      $endgroup$
      – Cpt Reynolds
      yesterday






    • 2




      $begingroup$
      @CptReynolds Agreed. The root source of the problem was, of course, lack of energy on very short final, which was totally a result of pilot error. But, given that situation, they pretty much had to choose how they were going to crash rather than whether they were going to crash. In that sort of situation, I'd personally prefer a human pilot who can look out the window and make rapid judgments based on the exact situation in control. It's just not the sort of thing that's easy to account for when you're designing a computer program.
      $endgroup$
      – reirab
      yesterday










    • $begingroup$
      I suggest to add Colgan 3407 to the list.
      $endgroup$
      – Martin Argerami
      14 hours ago














    11












    11








    11





    $begingroup$

    You said you understand systems to prevent the airplane from exceeding the flight envelope. Stall is just another boundary of the flight envelope. The rest of the envelope limitations are listed in the flight manual as well. Shouldn't pilots know not to stall the airplane, just as they know not to over-stress it, or exceed other limitations? Of course.



    But humans make mistakes, they can get distracted or disoriented. And just as there's little benefit to allowing a pilot to rip the wings off the plane by pitching too fast, there's little benefit from allowing the plane to stall.



    Here is a selection of aircraft that have crashed due to stalls.



    South Airlines Flight 8971



    Air Algérie 5017



    AirAsia QZ8501



    Thai Airways International flight 261



    Vladivostokavia Flight 352



    N452DA



    Yemenia Airways Flight 626



    If stall protection systems are implemented and functioning properly, they can prevent issues. Here are just a few instances where stall protection worked as intended:



    GoAir 338



    Air France 7662



    Jetstar 248






    share|improve this answer









    $endgroup$



    You said you understand systems to prevent the airplane from exceeding the flight envelope. Stall is just another boundary of the flight envelope. The rest of the envelope limitations are listed in the flight manual as well. Shouldn't pilots know not to stall the airplane, just as they know not to over-stress it, or exceed other limitations? Of course.



    But humans make mistakes, they can get distracted or disoriented. And just as there's little benefit to allowing a pilot to rip the wings off the plane by pitching too fast, there's little benefit from allowing the plane to stall.



    Here is a selection of aircraft that have crashed due to stalls.



    South Airlines Flight 8971



    Air Algérie 5017



    AirAsia QZ8501



    Thai Airways International flight 261



    Vladivostokavia Flight 352



    N452DA



    Yemenia Airways Flight 626



    If stall protection systems are implemented and functioning properly, they can prevent issues. Here are just a few instances where stall protection worked as intended:



    GoAir 338



    Air France 7662



    Jetstar 248







    share|improve this answer












    share|improve this answer



    share|improve this answer










    answered yesterday









    foootfooot

    53.1k17168321




    53.1k17168321








    • 1




      $begingroup$
      On the flip size, I'm curious what would have happened to Asiana 214 if it had had a stall prevention system. If I'm remembering correctly, they did stall (or at least very nearly stall) on very short final while trying to make the runway. If a stall prevention system had prevented them from raising the nose, would they have hit the nose on the seawall instead of the tail? That seems like it could have been a bad situation a whole lot worse.
      $endgroup$
      – reirab
      yesterday






    • 1




      $begingroup$
      @reirab True. On the other hand, if you allow the aircraft to run into two limits simultaneously (out of room and out of speed), there is not much anyone can do. You could argue the „opposite“ safety system, too, and say an automatic terrain escape manoeuvre would be fantastic, except with Asiana 214, it could have worsened the stall...
      $endgroup$
      – Cpt Reynolds
      yesterday






    • 2




      $begingroup$
      @CptReynolds Agreed. The root source of the problem was, of course, lack of energy on very short final, which was totally a result of pilot error. But, given that situation, they pretty much had to choose how they were going to crash rather than whether they were going to crash. In that sort of situation, I'd personally prefer a human pilot who can look out the window and make rapid judgments based on the exact situation in control. It's just not the sort of thing that's easy to account for when you're designing a computer program.
      $endgroup$
      – reirab
      yesterday










    • $begingroup$
      I suggest to add Colgan 3407 to the list.
      $endgroup$
      – Martin Argerami
      14 hours ago














    • 1




      $begingroup$
      On the flip size, I'm curious what would have happened to Asiana 214 if it had had a stall prevention system. If I'm remembering correctly, they did stall (or at least very nearly stall) on very short final while trying to make the runway. If a stall prevention system had prevented them from raising the nose, would they have hit the nose on the seawall instead of the tail? That seems like it could have been a bad situation a whole lot worse.
      $endgroup$
      – reirab
      yesterday






    • 1




      $begingroup$
      @reirab True. On the other hand, if you allow the aircraft to run into two limits simultaneously (out of room and out of speed), there is not much anyone can do. You could argue the „opposite“ safety system, too, and say an automatic terrain escape manoeuvre would be fantastic, except with Asiana 214, it could have worsened the stall...
      $endgroup$
      – Cpt Reynolds
      yesterday






    • 2




      $begingroup$
      @CptReynolds Agreed. The root source of the problem was, of course, lack of energy on very short final, which was totally a result of pilot error. But, given that situation, they pretty much had to choose how they were going to crash rather than whether they were going to crash. In that sort of situation, I'd personally prefer a human pilot who can look out the window and make rapid judgments based on the exact situation in control. It's just not the sort of thing that's easy to account for when you're designing a computer program.
      $endgroup$
      – reirab
      yesterday










    • $begingroup$
      I suggest to add Colgan 3407 to the list.
      $endgroup$
      – Martin Argerami
      14 hours ago








    1




    1




    $begingroup$
    On the flip size, I'm curious what would have happened to Asiana 214 if it had had a stall prevention system. If I'm remembering correctly, they did stall (or at least very nearly stall) on very short final while trying to make the runway. If a stall prevention system had prevented them from raising the nose, would they have hit the nose on the seawall instead of the tail? That seems like it could have been a bad situation a whole lot worse.
    $endgroup$
    – reirab
    yesterday




    $begingroup$
    On the flip size, I'm curious what would have happened to Asiana 214 if it had had a stall prevention system. If I'm remembering correctly, they did stall (or at least very nearly stall) on very short final while trying to make the runway. If a stall prevention system had prevented them from raising the nose, would they have hit the nose on the seawall instead of the tail? That seems like it could have been a bad situation a whole lot worse.
    $endgroup$
    – reirab
    yesterday




    1




    1




    $begingroup$
    @reirab True. On the other hand, if you allow the aircraft to run into two limits simultaneously (out of room and out of speed), there is not much anyone can do. You could argue the „opposite“ safety system, too, and say an automatic terrain escape manoeuvre would be fantastic, except with Asiana 214, it could have worsened the stall...
    $endgroup$
    – Cpt Reynolds
    yesterday




    $begingroup$
    @reirab True. On the other hand, if you allow the aircraft to run into two limits simultaneously (out of room and out of speed), there is not much anyone can do. You could argue the „opposite“ safety system, too, and say an automatic terrain escape manoeuvre would be fantastic, except with Asiana 214, it could have worsened the stall...
    $endgroup$
    – Cpt Reynolds
    yesterday




    2




    2




    $begingroup$
    @CptReynolds Agreed. The root source of the problem was, of course, lack of energy on very short final, which was totally a result of pilot error. But, given that situation, they pretty much had to choose how they were going to crash rather than whether they were going to crash. In that sort of situation, I'd personally prefer a human pilot who can look out the window and make rapid judgments based on the exact situation in control. It's just not the sort of thing that's easy to account for when you're designing a computer program.
    $endgroup$
    – reirab
    yesterday




    $begingroup$
    @CptReynolds Agreed. The root source of the problem was, of course, lack of energy on very short final, which was totally a result of pilot error. But, given that situation, they pretty much had to choose how they were going to crash rather than whether they were going to crash. In that sort of situation, I'd personally prefer a human pilot who can look out the window and make rapid judgments based on the exact situation in control. It's just not the sort of thing that's easy to account for when you're designing a computer program.
    $endgroup$
    – reirab
    yesterday












    $begingroup$
    I suggest to add Colgan 3407 to the list.
    $endgroup$
    – Martin Argerami
    14 hours ago




    $begingroup$
    I suggest to add Colgan 3407 to the list.
    $endgroup$
    – Martin Argerami
    14 hours ago











    0












    $begingroup$

    The relevant certification requirements, set by the FAA/JAA/CAA etc require that a "large aircraft" that is capable of stalling has an automatic stall warning and recovery system. So the simple answer is "because the rule of law says so".



    Maybe you could think about re-phrasing the question to ask why the traditional stick shaker and pusher, with a long and satisfactory history, were not used? I expect that Boeing will be having to answer that question to the authorities.






    share|improve this answer








    New contributor




    tiger99 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
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    $endgroup$


















      0












      $begingroup$

      The relevant certification requirements, set by the FAA/JAA/CAA etc require that a "large aircraft" that is capable of stalling has an automatic stall warning and recovery system. So the simple answer is "because the rule of law says so".



      Maybe you could think about re-phrasing the question to ask why the traditional stick shaker and pusher, with a long and satisfactory history, were not used? I expect that Boeing will be having to answer that question to the authorities.






      share|improve this answer








      New contributor




      tiger99 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
      Check out our Code of Conduct.






      $endgroup$
















        0












        0








        0





        $begingroup$

        The relevant certification requirements, set by the FAA/JAA/CAA etc require that a "large aircraft" that is capable of stalling has an automatic stall warning and recovery system. So the simple answer is "because the rule of law says so".



        Maybe you could think about re-phrasing the question to ask why the traditional stick shaker and pusher, with a long and satisfactory history, were not used? I expect that Boeing will be having to answer that question to the authorities.






        share|improve this answer








        New contributor




        tiger99 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
        Check out our Code of Conduct.






        $endgroup$



        The relevant certification requirements, set by the FAA/JAA/CAA etc require that a "large aircraft" that is capable of stalling has an automatic stall warning and recovery system. So the simple answer is "because the rule of law says so".



        Maybe you could think about re-phrasing the question to ask why the traditional stick shaker and pusher, with a long and satisfactory history, were not used? I expect that Boeing will be having to answer that question to the authorities.







        share|improve this answer








        New contributor




        tiger99 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
        Check out our Code of Conduct.









        share|improve this answer



        share|improve this answer






        New contributor




        tiger99 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
        Check out our Code of Conduct.









        answered 4 hours ago









        tiger99tiger99

        1




        1




        New contributor




        tiger99 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
        Check out our Code of Conduct.





        New contributor





        tiger99 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
        Check out our Code of Conduct.






        tiger99 is a new contributor to this site. Take care in asking for clarification, commenting, and answering.
        Check out our Code of Conduct.






























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