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The crash of Air France flight 447 (2021)

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131–140 of 231 posts

Re: The crash of Air France flight 447 (2021)

#131

Earlier quoted context omitted.

To be fair, it sounds like this crash caused airlines and regulators to demand much more adverse event training, including high-altitude stall recovery. But according to the article, Airbus hasn't addressed the split control issue…

There isn't a "split control issue," the split control setup is fundamental to the way the Airbus control schema works. Changing it would be a non-starter.

According to the author, the split control design mitigated communication between pilots, since one cannot feel what the other is doing.

That seems like a crucial functional omission.

Re: The crash of Air France flight 447 (2021)

#132

I fly a desk herding cats, I mean devs, for a living now. But as a Navy-trained aviator, this and the Colgan Air mishap in Buffalo always make me cringe. I can't entirely judge the crew, because the human mind is a strange thing that has ways of rationalizing truly abnormal situations and behavior. That said, an obvious Crew Resource Management failure compounded the issues here. That said, I believe aerobatics and o…

Maybe not even acrobatic flying training but glider training. Pilots with glider experience are some of the best performers in emergencies.

Sully's 'Miracle on the Hudson' is (largely?) attributed to his skill as a glider pilot.[0]

[0]https://en.wikipedia.org/wiki/US_Airways_Flight_1549

Re: The crash of Air France flight 447 (2021)

#133
I'm amazed that the autopilot kicked off just because the pitot tubes froze. The A330 has an inertial reference unit as well as (almost certainly) GPS, both of which could have provided ground speed. Air speed could be extrapolated from previous air speed and inferred from ground speed, engine thrust, and known weather. IRU and GPS could also have provided altitude and thus climb rate. And we know the plane had a barometer, although it had to be corrected for airspeed according to TFA. I'm guessing the plane also had a radar altimeter, but maybe not.

With all these sources of information, the autopilot could have said "Hey the pitot tubes are giving me weird data, but no worries. Still flying the plane. Carry on."

Why didn't that happen?

Re: The crash of Air France flight 447 (2021)

#134

The article misses the key takeaway from this incident IMHO. When the controls were pegged at full aft deflection, the stall warning would cease , because instrument readings in the deep stall were considered invalid by the computer. Whenever the pilot would start to push forward to recover, the computer stopped rejecting the readings, and started sounding the stall warning again! So every time the pilot started to d…

Not a pilot but I believe that pulling the stick back is exactly the wrong thing to do in a stall. The pilot should have instinctively known that pulling back on the stick would not recover a stall. On the other hand, pilots are taught to "trust the instruments" but IIRC the aircraft had no angle of attack indicator, and the airspeed tubes were frozen over. So lots of bad or missing information, contributing to stres…

I'm a pilot. Yes, you're correct, but there was so much else going on here... unless you're certain it's wrong, you're going to be inclined to listen to the airplane when it screams at you not to do something in an already terrifying unfamiliar situation.

Re: The crash of Air France flight 447 (2021)

#135

The article misses the key takeaway from this incident IMHO. When the controls were pegged at full aft deflection, the stall warning would cease , because instrument readings in the deep stall were considered invalid by the computer. Whenever the pilot would start to push forward to recover, the computer stopped rejecting the readings, and started sounding the stall warning again! So every time the pilot started to d…

> During flight 447’s plunge toward the sea, the flight directors disappeared every time the forward airspeed dropped below 60 knots. This was because an airspeed below 60 knots while in flight is so anomalous that the computers are programmed to reject such a reading as false. Furthermore, at an angle of attack threshold which corresponded quite closely to 60 knots, the stall warning would cease for exactly the same…

Yes. That's the only place it's mentioned, IMHO it is central to the whole thing.

Re: The crash of Air France flight 447 (2021)

#136

I'm amazed that the autopilot kicked off just because the pitot tubes froze. The A330 has an inertial reference unit as well as (almost certainly) GPS, both of which could have provided ground speed. Air speed could be extrapolated from previous air speed and inferred from ground speed, engine thrust, and known weather. IRU and GPS could also have provided altitude and thus climb rate. And we know the plane had a bar…

> Air speed could be extrapolated from previous air speed and inferred from ground speed, engine thrust, and known weather.

I think this is probably the main sticking point. I don't think you can do this accurately without some direct measurement. If the plane thinks its air speed is fine but it's actually approaching its stall speed because it guessed its airspeed incorrectly, that'd be really bad.

Re: The crash of Air France flight 447 (2021)

#137

The article misses the key takeaway from this incident IMHO. When the controls were pegged at full aft deflection, the stall warning would cease , because instrument readings in the deep stall were considered invalid by the computer. Whenever the pilot would start to push forward to recover, the computer stopped rejecting the readings, and started sounding the stall warning again! So every time the pilot started to d…

Nope the article goes deep into this exact issue:

> During flight 447’s plunge toward the sea, the flight directors disappeared every time the forward airspeed dropped below 60 knots. This was because an airspeed below 60 knots while in flight is so anomalous that the computers are programmed to reject such a reading as false. Furthermore, at an angle of attack threshold which corresponded quite closely to 60 knots, the stall warning would cease for exactly the same reason. This created an unfortunate correlation, wherein Bonin would pitch up, the angle of attack and airspeed would exceed the rejection thresholds, the flight director would stop telling him to fly up, and the stall warning would cease; then if he attempted to pitch down, the angle of attack data would become valid again, the flight director would tell him to pitch up, and the stall warning would return. This perverse Pavlovian relationship could have subconsciously conditioned Bonin to believe that pitching down was causing the plane to approach the stall envelope, and that by pitching up he was actually protecting the plane against stalling. This violated basic aeronautical common sense, but by this point Bonin and common sense might as well have been on different planets.

Re: The crash of Air France flight 447 (2021)

#138

Earlier quoted context omitted.

Maybe not even acrobatic flying training but glider training. Pilots with glider experience are some of the best performers in emergencies.

Sully's 'Miracle on the Hudson' is (largely?) attributed to his skill as a glider pilot.[0] [0] https://en.wikipedia.org/wiki/US_Airways_Flight_1549

Also, Air Canada Flight 143, the Gimli Glider.

https://en.wikipedia.org/wiki/Gimli_Glider

Re: The crash of Air France flight 447 (2021)

#139

Earlier quoted context omitted.

> During flight 447’s plunge toward the sea, the flight directors disappeared every time the forward airspeed dropped below 60 knots. This was because an airspeed below 60 knots while in flight is so anomalous that the computers are programmed to reject such a reading as false. Furthermore, at an angle of attack threshold which corresponded quite closely to 60 knots, the stall warning would cease for exactly the same…

Yes. That's the only place it's mentioned, IMHO it is central to the whole thing.

It's a really long and clear paragraph, what more do you expect?

The summary blames the accident on poor training and the typical EFIS "pilot out of the loop" problem, rather than very specific issues like this. Which makes very much sense IMO.

Re: The crash of Air France flight 447 (2021)

#140

The article misses the key takeaway from this incident IMHO. When the controls were pegged at full aft deflection, the stall warning would cease , because instrument readings in the deep stall were considered invalid by the computer. Whenever the pilot would start to push forward to recover, the computer stopped rejecting the readings, and started sounding the stall warning again! So every time the pilot started to d…

Nope the article goes deep into this exact issue: > During flight 447’s plunge toward the sea, the flight directors disappeared every time the forward airspeed dropped below 60 knots. This was because an airspeed below 60 knots while in flight is so anomalous that the computers are programmed to reject such a reading as false. Furthermore, at an angle of attack threshold which corresponded quite closely to 60 knots,…

Nope. One paragraph in a very long article is not "deep" at all.
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