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The difference between the Boeing problem, where the computer would do un-intuitive things that caused the planes to dive, and the AF447 A330 situation, where t
by harshreality 6y ago
The difference between the Boeing problem, where the computer would do un-intuitive things that caused the planes to dive, and the AF447 A330 situation, where the pitot tubes froze over (they shouldn't have) but the aircraft wouldn't try to crash itself, is significant.
Of course the pitots shouldn't have frozen over, and of course the stall warnings were poorly thought out, and of course the lack of direct awareness by the other pilot of Bonin's inputs leads to misunderstanding of the situation, but there's one big problem in the AF447 case that has nothing to do with bugs in the A330.
Bonin (who flew the plane into the ocean) had no awareness of the Airbus's different flight modes or that the autopilot disconnect meant the plane was in Alternate Law, and as a result blissfully kept pulling back on the joystick thinking the computer would save him from ever stalling. The different flight modes are like the most basic part of operating an Airbus in an emergency, and the idea that any trained pilot wouldn't first consider which mode they're in is staggering.
Read the transcript. You have Bonin pulling back on the stick almost continuously without saying so, you have Robert advising him to descend, and Bonin replying that he was descending, when he never did. He let the controls go back to neutral, the plane was still ascending with a wildly high AOA for the conditions, and he quickly reverted to pulling back on the joystick.
Only less than a minute before impact, when the rapid descent and confusion lead to Robert advising Bonin to climb, does Bonin reveal the critical information, at which point both Robert and the Captain must have been shocked and horrified, both realizing they had to dive and also realizing they didn't have enough altitude and were going to crash:
02:13:40 (Robert) Climb... climb... climb... climb...
02:13:40 (Bonin) But I've had the stick back the whole time!
[At last, Bonin tells the others the crucial fact whose import he has so grievously failed to understand himself.]
02:13:42 (Captain) No, no, no… Don’t climb… no, no.
02:13:43 (Robert) Descend, then… Give me the controls… Give me the controls!
[Bonin yields the controls, and Robert finally puts the nose down. The plane begins to regain speed. But it is still descending at a precipitous angle. As they near 2000 feet, the aircraft's sensors detect the fast-approaching surface and trigger a new alarm. There is no time left to build up speed by pushing the plane's nose forward into a dive. At any rate, without warning his colleagues, Bonin once again takes back the controls and pulls his side stick all the way back.]
02:14:23 (Robert) Damn it, we’re going to crash… This can’t be happening!
02:14:25 (Bonin) But what’s happening?
02:14:27 (Captain) Ten degrees of pitch…
Exactly 1.4 seconds later, the cockpit voice recorder stops.
Transcript with notes: https://www.tailstrike.com/010609.html https://www.tailstrike.com/010609.html
Bonin may have passed training but he clearly wasn't competent to fly an Airbus. Air France crew resource management (communication between pilots) sucked, and a bunch of Airbus quirks led to the other pilots not discovering that Bonin was doing the wrong thing until it was too late. However, virtually any other pilot wouldn't have stalled the plane.
- wahern 6y agoIt seems like the difference here is that in the Boeing incidents the flight computer was Bonin, inputting the grossly wrong control[1] based on a tragically flawed model of the current angle of attack. Among all Airbus pilots, there are probably only a small number of Bonins. On the Boeing 737-MAX, every plane has a Bonin. [1] Not just the wrong command, but of a magnitude that greatly exacerbated the situation, based on an unwarranted level of certitude.