Why do passenger jet manufacturers design their planes with stall prevention systems?Why do passenger jets...
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Why do passenger jet manufacturers design their planes with stall prevention systems?
Why do passenger jets accept input that will cause the aircraft to perform dangerous maneuvers it was not designed for?What climb rates can the Airbus A320-200 achieve and which climb rates are commonly used for normal flight operations?How can we recover from a tailplane stall?Does the expression “stall speed” have a definition?Why does Airbus suppress stall warnings in certain situations?Why disable stall warning based only on low airspeed, rather than multiple criteria?Why are the positive points in a V-n diagram associated with pitch maneuvers?Can computer imposed inputs be overridden on the Boeing 737-MAX?How do aircraft stall warning systems handle (or not) asymmetric-stall situations?Why is the A330/A340's angle-of-attack protection disabled in alternate law, even if the AoA vanes are operating normally?
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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?
aircraft-design stall
asked Mar 14 at 17:37
rclocher3rclocher3
306210
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show 1 more comment
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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?
aircraft-design stall
asked Mar 14 at 17:37
rclocher3rclocher3
306210
$endgroup$
8
$begingroup$
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...
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– Ron Beyer
Mar 14 at 17:51
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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
Mar 14 at 19:52
17
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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.
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– reirab
Mar 14 at 20:30
6
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Because stalls are really bad?
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– David Richerby
Mar 15 at 17:57
5
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I feel "to prevent stalls" might not be the answer you're looking for, but I think it's accurate.
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– UKMonkey
Mar 16 at 9:24
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show 1 more comment
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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?
aircraft-design stall
asked Mar 14 at 17:37
rclocher3rclocher3
306210
$endgroup$
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
aircraft-design stall
asked Mar 14 at 17:37
rclocher3rclocher3
306210
asked Mar 14 at 17:37
rclocher3rclocher3
306210
asked Mar 14 at 17:37
rclocher3rclocher3
306210
asked Mar 14 at 17:37
rclocher3rclocher3
306210
asked Mar 14 at 17:37
rclocher3rclocher3
306210
306210
8
$begingroup$
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
Mar 14 at 17:51
$begingroup$
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
Mar 14 at 19:52
17
$begingroup$
@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
Mar 14 at 20:30
6
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Because stalls are really bad?
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– David Richerby
Mar 15 at 17:57
5
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I feel "to prevent stalls" might not be the answer you're looking for, but I think it's accurate.
$endgroup$
– UKMonkey
Mar 16 at 9:24
|
show 1 more comment
8
$begingroup$
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
Mar 14 at 17:51
$begingroup$
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
Mar 14 at 19:52
17
$begingroup$
@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
Mar 14 at 20:30
6
$begingroup$
Because stalls are really bad?
$endgroup$
– David Richerby
Mar 15 at 17:57
5
$begingroup$
I feel "to prevent stalls" might not be the answer you're looking for, but I think it's accurate.
$endgroup$
– UKMonkey
Mar 16 at 9:24
8
8
$begingroup$
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
Mar 14 at 17:51
$begingroup$
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
Mar 14 at 17:51
$begingroup$
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
Mar 14 at 19:52
$begingroup$
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
Mar 14 at 19:52
17
17
$begingroup$
@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
Mar 14 at 20:30
$begingroup$
@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
Mar 14 at 20:30
6
6
$begingroup$
Because stalls are really bad?
$endgroup$
– David Richerby
Mar 15 at 17:57
$begingroup$
Because stalls are really bad?
$endgroup$
– David Richerby
Mar 15 at 17:57
5
5
$begingroup$
I feel "to prevent stalls" might not be the answer you're looking for, but I think it's accurate.
$endgroup$
– UKMonkey
Mar 16 at 9:24
$begingroup$
I feel "to prevent stalls" might not be the answer you're looking for, but I think it's accurate.
$endgroup$
– UKMonkey
Mar 16 at 9:24
|
show 1 more comment
5 Answers
5
active
oldest
votes
$begingroup$
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?
A better analogy:
Why do car manufacturers install anti-lock break systems? Shouldn't drivers know that when their brakes lock up they should release brake pressure and/or pump the brakes quickly to slow the car down?*
*To be fair, I don't think this is actually taught in driver's education (at least in the US) anymore - my kids learned this from me, but never reported being taught and/or practicing when they took driver's ed. One of the many reasons flying is safer than driving.
- 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
answered Mar 14 at 17:54
FreeManFreeMan
7,6431060125
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2
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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
Mar 15 at 6:16
4
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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
Mar 15 at 7:14
1
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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
Mar 15 at 12:54
2
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@James I am quite sure that pulling all the way back on the stick at all times is not the pilots doing the right thing on AF447. Pulling back all the way on the stick is what you do when you are evil and trying to intentionally stall the airplane into the sea. It's well established that if the pilots had simply let go of the controls, the plane would have righted itself.
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– Harper
Mar 16 at 16:23
1
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@James No. When the stall warning returned, the idiot again pulled full back on the stick, (without mentioning this to the pilot flying), dooming what chance of recovery might have remained. Please explain to me how that is anything other than the stupidest, most destructive action possible? What on earth could the guy possibly have been trying to accomplish?
$endgroup$
– Harper
Mar 16 at 21:28
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show 6 more comments
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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.
answered Mar 14 at 18:25
John KJohn K
22.8k13166
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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
Mar 15 at 1:08
2
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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
Mar 15 at 1:28
2
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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.
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– John K
Mar 15 at 1:30
2
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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
Mar 15 at 7:05
2
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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.
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– John K
Mar 15 at 15:03
add a comment |
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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
answered Mar 14 at 20:00
foootfooot
53.4k17170321
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1
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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
Mar 14 at 20:37
2
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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
Mar 14 at 21:17
3
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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.
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– reirab
Mar 14 at 21:26
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I suggest to add Colgan 3407 to the list.
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– Martin Argerami
Mar 15 at 11:36
1
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I think there may also be a slight game of numbers played by some airlines. The chances of an aircraft crashing are very slim, and well-trained pilots are more expensive (at least to train). I think the entire industry is seeing the results of a couple of decades of it simply not being worth pursuing an airline career, so there aren't enough young, experienced pilots. Thus, countries with less strict airmen certification or operation standards end up with less experienced pilots operating well beyond their capabilities.
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– Shawn
Mar 16 at 3:57
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show 2 more comments
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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.
answered Mar 15 at 21:26
tiger99tiger99
311
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I agree entirely that your re-phrasing would have improved the question, but it's probably too late now :(
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– rclocher3
Mar 18 at 23:58
add a comment |
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Well, stall is a limit to flight envelope, the one exceeding which is most dangerous, so stall prevention system is one of the systems that override pilot input if it would lead to exceeding the flight envelope.
And note that stall is directly related to pilot input, because in stable aircraft¹ the angle of attack is directly controlled by elevator and stabilizer position² and stall occurs when the critical for given configuration is exceeded.
¹ All transport aircraft are longitudinally stable. Only unstable aircraft are some new fighters (and some very early experiments).
² The stability makes the aircraft always pitch so as to assume the “trimmed” angle of attack determined by the control surface position. It is a first order feedback, so no oscillations, and it takes really abrupt control input, or severe turbulence, to create a significant momentary deviation.
answered Mar 16 at 11:52
Jan HudecJan Hudec
40.2k4106196
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add a comment |
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5 Answers
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active
oldest
votes
5 Answers
5
active
oldest
votes
active
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active
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$begingroup$
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?
A better analogy:
Why do car manufacturers install anti-lock break systems? Shouldn't drivers know that when their brakes lock up they should release brake pressure and/or pump the brakes quickly to slow the car down?*
*To be fair, I don't think this is actually taught in driver's education (at least in the US) anymore - my kids learned this from me, but never reported being taught and/or practicing when they took driver's ed. One of the many reasons flying is safer than driving.
- 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
answered Mar 14 at 17:54
FreeManFreeMan
7,6431060125
$endgroup$
2
$begingroup$
And because even with stall prevention systems, stalls are still a reality. That's how bad it is
$endgroup$
– Hanky Panky
Mar 15 at 6:16
4
$begingroup$
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
Mar 15 at 7:14
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
Mar 15 at 12:54
2
$begingroup$
@James I am quite sure that pulling all the way back on the stick at all times is not the pilots doing the right thing on AF447. Pulling back all the way on the stick is what you do when you are evil and trying to intentionally stall the airplane into the sea. It's well established that if the pilots had simply let go of the controls, the plane would have righted itself.
$endgroup$
– Harper
Mar 16 at 16:23
1
$begingroup$
@James No. When the stall warning returned, the idiot again pulled full back on the stick, (without mentioning this to the pilot flying), dooming what chance of recovery might have remained. Please explain to me how that is anything other than the stupidest, most destructive action possible? What on earth could the guy possibly have been trying to accomplish?
$endgroup$
– Harper
Mar 16 at 21:28
|
show 6 more comments
$begingroup$
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?
A better analogy:
Why do car manufacturers install anti-lock break systems? Shouldn't drivers know that when their brakes lock up they should release brake pressure and/or pump the brakes quickly to slow the car down?*
*To be fair, I don't think this is actually taught in driver's education (at least in the US) anymore - my kids learned this from me, but never reported being taught and/or practicing when they took driver's ed. One of the many reasons flying is safer than driving.
- 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
answered Mar 14 at 17:54
FreeManFreeMan
7,6431060125
$endgroup$
2
$begingroup$
And because even with stall prevention systems, stalls are still a reality. That's how bad it is
$endgroup$
– Hanky Panky
Mar 15 at 6:16
4
$begingroup$
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
Mar 15 at 7:14
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
Mar 15 at 12:54
2
$begingroup$
@James I am quite sure that pulling all the way back on the stick at all times is not the pilots doing the right thing on AF447. Pulling back all the way on the stick is what you do when you are evil and trying to intentionally stall the airplane into the sea. It's well established that if the pilots had simply let go of the controls, the plane would have righted itself.
$endgroup$
– Harper
Mar 16 at 16:23
1
$begingroup$
@James No. When the stall warning returned, the idiot again pulled full back on the stick, (without mentioning this to the pilot flying), dooming what chance of recovery might have remained. Please explain to me how that is anything other than the stupidest, most destructive action possible? What on earth could the guy possibly have been trying to accomplish?
$endgroup$
– Harper
Mar 16 at 21:28
|
show 6 more comments
$begingroup$
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?
A better analogy:
Why do car manufacturers install anti-lock break systems? Shouldn't drivers know that when their brakes lock up they should release brake pressure and/or pump the brakes quickly to slow the car down?*
*To be fair, I don't think this is actually taught in driver's education (at least in the US) anymore - my kids learned this from me, but never reported being taught and/or practicing when they took driver's ed. One of the many reasons flying is safer than driving.
- 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
answered Mar 14 at 17:54
FreeManFreeMan
7,6431060125
$endgroup$
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?
A better analogy:
Why do car manufacturers install anti-lock break systems? Shouldn't drivers know that when their brakes lock up they should release brake pressure and/or pump the brakes quickly to slow the car down?*
*To be fair, I don't think this is actually taught in driver's education (at least in the US) anymore - my kids learned this from me, but never reported being taught and/or practicing when they took driver's ed. One of the many reasons flying is safer than driving.
- 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
answered Mar 14 at 17:54
FreeManFreeMan
7,6431060125
edited Mar 20 at 10:24
answered Mar 14 at 17:54
FreeManFreeMan
7,6431060125
answered Mar 14 at 17:54
FreeManFreeMan
7,6431060125
answered Mar 14 at 17:54
FreeManFreeMan
7,6431060125
7,6431060125
2
$begingroup$
And because even with stall prevention systems, stalls are still a reality. That's how bad it is
$endgroup$
– Hanky Panky
Mar 15 at 6:16
4
$begingroup$
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
Mar 15 at 7:14
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
Mar 15 at 12:54
2
$begingroup$
@James I am quite sure that pulling all the way back on the stick at all times is not the pilots doing the right thing on AF447. Pulling back all the way on the stick is what you do when you are evil and trying to intentionally stall the airplane into the sea. It's well established that if the pilots had simply let go of the controls, the plane would have righted itself.
$endgroup$
– Harper
Mar 16 at 16:23
1
$begingroup$
@James No. When the stall warning returned, the idiot again pulled full back on the stick, (without mentioning this to the pilot flying), dooming what chance of recovery might have remained. Please explain to me how that is anything other than the stupidest, most destructive action possible? What on earth could the guy possibly have been trying to accomplish?
$endgroup$
– Harper
Mar 16 at 21:28
|
show 6 more comments
2
$begingroup$
And because even with stall prevention systems, stalls are still a reality. That's how bad it is
$endgroup$
– Hanky Panky
Mar 15 at 6:16
4
$begingroup$
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
Mar 15 at 7:14
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
Mar 15 at 12:54
2
$begingroup$
@James I am quite sure that pulling all the way back on the stick at all times is not the pilots doing the right thing on AF447. Pulling back all the way on the stick is what you do when you are evil and trying to intentionally stall the airplane into the sea. It's well established that if the pilots had simply let go of the controls, the plane would have righted itself.
$endgroup$
– Harper
Mar 16 at 16:23
1
$begingroup$
@James No. When the stall warning returned, the idiot again pulled full back on the stick, (without mentioning this to the pilot flying), dooming what chance of recovery might have remained. Please explain to me how that is anything other than the stupidest, most destructive action possible? What on earth could the guy possibly have been trying to accomplish?
$endgroup$
– Harper
Mar 16 at 21:28
2
2
$begingroup$
And because even with stall prevention systems, stalls are still a reality. That's how bad it is
$endgroup$
– Hanky Panky
Mar 15 at 6:16
$begingroup$
And because even with stall prevention systems, stalls are still a reality. That's how bad it is
$endgroup$
– Hanky Panky
Mar 15 at 6:16
4
4
$begingroup$
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
Mar 15 at 7:14
$begingroup$
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
Mar 15 at 7:14
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
Mar 15 at 12:54
$begingroup$
@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
Mar 15 at 12:54
2
2
$begingroup$
@James I am quite sure that pulling all the way back on the stick at all times is not the pilots doing the right thing on AF447. Pulling back all the way on the stick is what you do when you are evil and trying to intentionally stall the airplane into the sea. It's well established that if the pilots had simply let go of the controls, the plane would have righted itself.
$endgroup$
– Harper
Mar 16 at 16:23
$begingroup$
@James I am quite sure that pulling all the way back on the stick at all times is not the pilots doing the right thing on AF447. Pulling back all the way on the stick is what you do when you are evil and trying to intentionally stall the airplane into the sea. It's well established that if the pilots had simply let go of the controls, the plane would have righted itself.
$endgroup$
– Harper
Mar 16 at 16:23
1
1
$begingroup$
@James No. When the stall warning returned, the idiot again pulled full back on the stick, (without mentioning this to the pilot flying), dooming what chance of recovery might have remained. Please explain to me how that is anything other than the stupidest, most destructive action possible? What on earth could the guy possibly have been trying to accomplish?
$endgroup$
– Harper
Mar 16 at 21:28
$begingroup$
@James No. When the stall warning returned, the idiot again pulled full back on the stick, (without mentioning this to the pilot flying), dooming what chance of recovery might have remained. Please explain to me how that is anything other than the stupidest, most destructive action possible? What on earth could the guy possibly have been trying to accomplish?
$endgroup$
– Harper
Mar 16 at 21:28
|
show 6 more comments
$begingroup$
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.
answered Mar 14 at 18:25
John KJohn K
22.8k13166
$endgroup$
$begingroup$
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
Mar 15 at 1:08
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
Mar 15 at 1:28
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
Mar 15 at 1:30
2
$begingroup$
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
Mar 15 at 7:05
2
$begingroup$
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
Mar 15 at 15:03
add a comment |
$begingroup$
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.
answered Mar 14 at 18:25
John KJohn K
22.8k13166
$endgroup$
$begingroup$
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
Mar 15 at 1:08
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
Mar 15 at 1:28
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
Mar 15 at 1:30
2
$begingroup$
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
Mar 15 at 7:05
2
$begingroup$
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
Mar 15 at 15:03
add a comment |
$begingroup$
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.
answered Mar 14 at 18:25
John KJohn K
22.8k13166
$endgroup$
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.
answered Mar 14 at 18:25
John KJohn K
22.8k13166
answered Mar 14 at 18:25
John KJohn K
22.8k13166
answered Mar 14 at 18:25
John KJohn K
22.8k13166
answered Mar 14 at 18:25
John KJohn K
22.8k13166
22.8k13166
$begingroup$
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
Mar 15 at 1:08
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
Mar 15 at 1:28
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
Mar 15 at 1:30
2
$begingroup$
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
Mar 15 at 7:05
2
$begingroup$
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
Mar 15 at 15:03
add a comment |
$begingroup$
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
Mar 15 at 1:08
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
Mar 15 at 1:28
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
Mar 15 at 1:30
2
$begingroup$
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
Mar 15 at 7:05
2
$begingroup$
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
Mar 15 at 15:03
$begingroup$
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
Mar 15 at 1:08
$begingroup$
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
Mar 15 at 1:08
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
Mar 15 at 1:28
$begingroup$
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
Mar 15 at 1:28
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
Mar 15 at 1:30
$begingroup$
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
Mar 15 at 1:30
2
2
$begingroup$
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
Mar 15 at 7:05
$begingroup$
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
Mar 15 at 7:05
2
2
$begingroup$
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
Mar 15 at 15:03
$begingroup$
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
Mar 15 at 15:03
add a comment |
$begingroup$
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
answered Mar 14 at 20:00
foootfooot
53.4k17170321
$endgroup$
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
Mar 14 at 20:37
2
$begingroup$
@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
Mar 14 at 21:17
3
$begingroup$
@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
Mar 14 at 21:26
$begingroup$
I suggest to add Colgan 3407 to the list.
$endgroup$
– Martin Argerami
Mar 15 at 11:36
1
$begingroup$
I think there may also be a slight game of numbers played by some airlines. The chances of an aircraft crashing are very slim, and well-trained pilots are more expensive (at least to train). I think the entire industry is seeing the results of a couple of decades of it simply not being worth pursuing an airline career, so there aren't enough young, experienced pilots. Thus, countries with less strict airmen certification or operation standards end up with less experienced pilots operating well beyond their capabilities.
$endgroup$
– Shawn
Mar 16 at 3:57
|
show 2 more comments
$begingroup$
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
answered Mar 14 at 20:00
foootfooot
53.4k17170321
$endgroup$
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
Mar 14 at 20:37
2
$begingroup$
@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
Mar 14 at 21:17
3
$begingroup$
@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
Mar 14 at 21:26
$begingroup$
I suggest to add Colgan 3407 to the list.
$endgroup$
– Martin Argerami
Mar 15 at 11:36
1
$begingroup$
I think there may also be a slight game of numbers played by some airlines. The chances of an aircraft crashing are very slim, and well-trained pilots are more expensive (at least to train). I think the entire industry is seeing the results of a couple of decades of it simply not being worth pursuing an airline career, so there aren't enough young, experienced pilots. Thus, countries with less strict airmen certification or operation standards end up with less experienced pilots operating well beyond their capabilities.
$endgroup$
– Shawn
Mar 16 at 3:57
|
show 2 more comments
$begingroup$
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
answered Mar 14 at 20:00
foootfooot
53.4k17170321
$endgroup$
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
answered Mar 14 at 20:00
foootfooot
53.4k17170321
answered Mar 14 at 20:00
foootfooot
53.4k17170321
answered Mar 14 at 20:00
foootfooot
53.4k17170321
answered Mar 14 at 20:00
foootfooot
53.4k17170321
53.4k17170321
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
Mar 14 at 20:37
2
$begingroup$
@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
Mar 14 at 21:17
3
$begingroup$
@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
Mar 14 at 21:26
$begingroup$
I suggest to add Colgan 3407 to the list.
$endgroup$
– Martin Argerami
Mar 15 at 11:36
1
$begingroup$
I think there may also be a slight game of numbers played by some airlines. The chances of an aircraft crashing are very slim, and well-trained pilots are more expensive (at least to train). I think the entire industry is seeing the results of a couple of decades of it simply not being worth pursuing an airline career, so there aren't enough young, experienced pilots. Thus, countries with less strict airmen certification or operation standards end up with less experienced pilots operating well beyond their capabilities.
$endgroup$
– Shawn
Mar 16 at 3:57
|
show 2 more comments
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
Mar 14 at 20:37
2
$begingroup$
@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
Mar 14 at 21:17
3
$begingroup$
@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
Mar 14 at 21:26
$begingroup$
I suggest to add Colgan 3407 to the list.
$endgroup$
– Martin Argerami
Mar 15 at 11:36
1
$begingroup$
I think there may also be a slight game of numbers played by some airlines. The chances of an aircraft crashing are very slim, and well-trained pilots are more expensive (at least to train). I think the entire industry is seeing the results of a couple of decades of it simply not being worth pursuing an airline career, so there aren't enough young, experienced pilots. Thus, countries with less strict airmen certification or operation standards end up with less experienced pilots operating well beyond their capabilities.
$endgroup$
– Shawn
Mar 16 at 3:57
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
Mar 14 at 20:37
$begingroup$
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
Mar 14 at 20:37
2
2
$begingroup$
@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
Mar 14 at 21:17
$begingroup$
@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
Mar 14 at 21:17
3
3
$begingroup$
@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
Mar 14 at 21:26
$begingroup$
@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
Mar 14 at 21:26
$begingroup$
I suggest to add Colgan 3407 to the list.
$endgroup$
– Martin Argerami
Mar 15 at 11:36
$begingroup$
I suggest to add Colgan 3407 to the list.
$endgroup$
– Martin Argerami
Mar 15 at 11:36
1
1
$begingroup$
I think there may also be a slight game of numbers played by some airlines. The chances of an aircraft crashing are very slim, and well-trained pilots are more expensive (at least to train). I think the entire industry is seeing the results of a couple of decades of it simply not being worth pursuing an airline career, so there aren't enough young, experienced pilots. Thus, countries with less strict airmen certification or operation standards end up with less experienced pilots operating well beyond their capabilities.
$endgroup$
– Shawn
Mar 16 at 3:57
$begingroup$
I think there may also be a slight game of numbers played by some airlines. The chances of an aircraft crashing are very slim, and well-trained pilots are more expensive (at least to train). I think the entire industry is seeing the results of a couple of decades of it simply not being worth pursuing an airline career, so there aren't enough young, experienced pilots. Thus, countries with less strict airmen certification or operation standards end up with less experienced pilots operating well beyond their capabilities.
$endgroup$
– Shawn
Mar 16 at 3:57
|
show 2 more comments
$begingroup$
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.
answered Mar 15 at 21:26
tiger99tiger99
311
$endgroup$
$begingroup$
I agree entirely that your re-phrasing would have improved the question, but it's probably too late now :(
$endgroup$
– rclocher3
Mar 18 at 23:58
add a comment |
$begingroup$
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.
answered Mar 15 at 21:26
tiger99tiger99
311
$endgroup$
$begingroup$
I agree entirely that your re-phrasing would have improved the question, but it's probably too late now :(
$endgroup$
– rclocher3
Mar 18 at 23:58
add a comment |
$begingroup$
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.
answered Mar 15 at 21:26
tiger99tiger99
311
$endgroup$
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.
answered Mar 15 at 21:26
tiger99tiger99
311
answered Mar 15 at 21:26
tiger99tiger99
311
answered Mar 15 at 21:26
tiger99tiger99
311
answered Mar 15 at 21:26
tiger99tiger99
311
311
$begingroup$
I agree entirely that your re-phrasing would have improved the question, but it's probably too late now :(
$endgroup$
– rclocher3
Mar 18 at 23:58
add a comment |
$begingroup$
I agree entirely that your re-phrasing would have improved the question, but it's probably too late now :(
$endgroup$
– rclocher3
Mar 18 at 23:58
$begingroup$
I agree entirely that your re-phrasing would have improved the question, but it's probably too late now :(
$endgroup$
– rclocher3
Mar 18 at 23:58
$begingroup$
I agree entirely that your re-phrasing would have improved the question, but it's probably too late now :(
$endgroup$
– rclocher3
Mar 18 at 23:58
add a comment |
$begingroup$
Well, stall is a limit to flight envelope, the one exceeding which is most dangerous, so stall prevention system is one of the systems that override pilot input if it would lead to exceeding the flight envelope.
And note that stall is directly related to pilot input, because in stable aircraft¹ the angle of attack is directly controlled by elevator and stabilizer position² and stall occurs when the critical for given configuration is exceeded.
¹ All transport aircraft are longitudinally stable. Only unstable aircraft are some new fighters (and some very early experiments).
² The stability makes the aircraft always pitch so as to assume the “trimmed” angle of attack determined by the control surface position. It is a first order feedback, so no oscillations, and it takes really abrupt control input, or severe turbulence, to create a significant momentary deviation.
answered Mar 16 at 11:52
Jan HudecJan Hudec
40.2k4106196
$endgroup$
add a comment |
$begingroup$
Well, stall is a limit to flight envelope, the one exceeding which is most dangerous, so stall prevention system is one of the systems that override pilot input if it would lead to exceeding the flight envelope.
And note that stall is directly related to pilot input, because in stable aircraft¹ the angle of attack is directly controlled by elevator and stabilizer position² and stall occurs when the critical for given configuration is exceeded.
¹ All transport aircraft are longitudinally stable. Only unstable aircraft are some new fighters (and some very early experiments).
² The stability makes the aircraft always pitch so as to assume the “trimmed” angle of attack determined by the control surface position. It is a first order feedback, so no oscillations, and it takes really abrupt control input, or severe turbulence, to create a significant momentary deviation.
answered Mar 16 at 11:52
Jan HudecJan Hudec
40.2k4106196
$endgroup$
add a comment |
$begingroup$
Well, stall is a limit to flight envelope, the one exceeding which is most dangerous, so stall prevention system is one of the systems that override pilot input if it would lead to exceeding the flight envelope.
And note that stall is directly related to pilot input, because in stable aircraft¹ the angle of attack is directly controlled by elevator and stabilizer position² and stall occurs when the critical for given configuration is exceeded.
¹ All transport aircraft are longitudinally stable. Only unstable aircraft are some new fighters (and some very early experiments).
² The stability makes the aircraft always pitch so as to assume the “trimmed” angle of attack determined by the control surface position. It is a first order feedback, so no oscillations, and it takes really abrupt control input, or severe turbulence, to create a significant momentary deviation.
answered Mar 16 at 11:52
Jan HudecJan Hudec
40.2k4106196
$endgroup$
Well, stall is a limit to flight envelope, the one exceeding which is most dangerous, so stall prevention system is one of the systems that override pilot input if it would lead to exceeding the flight envelope.
And note that stall is directly related to pilot input, because in stable aircraft¹ the angle of attack is directly controlled by elevator and stabilizer position² and stall occurs when the critical for given configuration is exceeded.
¹ All transport aircraft are longitudinally stable. Only unstable aircraft are some new fighters (and some very early experiments).
² The stability makes the aircraft always pitch so as to assume the “trimmed” angle of attack determined by the control surface position. It is a first order feedback, so no oscillations, and it takes really abrupt control input, or severe turbulence, to create a significant momentary deviation.
answered Mar 16 at 11:52
Jan HudecJan Hudec
40.2k4106196
answered Mar 16 at 11:52
Jan HudecJan Hudec
40.2k4106196
answered Mar 16 at 11:52
Jan HudecJan Hudec
40.2k4106196
answered Mar 16 at 11:52
Jan HudecJan Hudec
40.2k4106196
40.2k4106196
add a comment |
add a comment |
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8
$begingroup$
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
Mar 14 at 17:51
$begingroup$
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
Mar 14 at 19:52
17
$begingroup$
@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
Mar 14 at 20:30
6
$begingroup$
Because stalls are really bad?
$endgroup$
– David Richerby
Mar 15 at 17:57
5
$begingroup$
I feel "to prevent stalls" might not be the answer you're looking for, but I think it's accurate.
$endgroup$
– UKMonkey
Mar 16 at 9:24