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Fly-By-Wire Contributed To Air France 447 Disaster
Hugh Pickens writes "The Telegraph reports that although fly-by-wire technology has huge advantages, Airbus's 'brilliant' aircraft design may have contributed to one of the world's worst aviation disasters and the deaths of all 228 passengers onboard Air France Flight 447 from Rio de Janeiro to Paris. While there is no doubt that at least one of AF447's pilots made a fatal and sustained mistake, the errors committed by the pilot doing the flying were not corrected by his more experienced colleagues because they did not know he was behaving in a manner bound to induce a stall. The reason for that fatal lack of awareness lies partly in the design of the control stick – the 'side stick' – used in all Airbus cockpits. 'Most Airbus pilots I know love it because of the reliable automation that allows you to manage situations and not be so fatigued by the mechanics of flying,' says Stephen King of the British Airline Pilots' Association. But the fact that the second pilot's stick stays in neutral whatever there is input to the other is not a good thing. 'It's not immediately apparent to one pilot what the other may be doing with the control stick, unless he makes a big effort to look across to the other side of the flight deck, which is not easy. In any case, the side stick is held back for only a few seconds, so you have to see the action being taken.'"
Yes and no –the reason they were ignoring the voice saying STALL, STALL, STALL was because they believed that the computer software made it impossible to stall the aircraft, and that all the warning meant was "if you turn off all the computer assistance now, it'll stall", not "the computer assistance is already all off, I am stalling".
A second warning that doesn't ever sound in safe scenarios (e.g. FALLING, FALLING, FALLING) might just have made them twig to "crap, it really is stalling".
yes, this was how the whole thing started - that they got an incorrect airspeed indication, and thus the autopilot disengaged. after a short while, the speed indication was correct again. unfortunately, human errors added up starting from there.
although I would argue that the first mistake that they made was to fly into the storm, which every one else navigated around at that time. in aviation, you have to have at least 3 mistakes in a row to have an accident - here, flying into the storm, the frozen airspace indicator and then human error.
in such occasions, the usual procedure is not to lower the nose & convert altitude to speed, but to simply 'power yourself out' of the stall situation - apply a lot of (available excess) power, and your speed will pick up, and you're not close to stalling anymore.
I'm not sure where you got that information, but that is not the correct course of action. Even in a low altitude situation, a stall can only be recovered by lowering the angle of attack... engine power and speed have absolutely nothing to do with it. A stall is an aerodynamic condition where the wings are not producing enough lift for flight. Pushing the nose over (to lower the angle of attack) allows the air to reattach to the wings which eliminates the stall condition.
Bill
It's my Sig and you can't have it. Mine! All Mine!
Issuing "small, well intentioned commands" is how it usually works, but in this case the flight controls had been switched into their alternate control law, due to the loss of reliable airspeed data. In alternate law the columns do what a "dumb" FBW system does, and stick displacement will reflect in contro surface deflection.
Don't blame me, I voted for Baltar.
No, that's not what happened at all. It's quite clear what happened. The one pilot was a fucking moron, and he had the stick pulled back the entire goddamn time they were stalled out and falling out of the sky. The other pilot had his stick pushed forward, trying to nose it down and gain some airspeed. The piece of shit computer system on the Airbus averaged the two inputs, finally concluding that keeping the control surfaces level was a good compromise. Only seconds before impact did the junior pilot (who should have never been behind the stick of a Cessna, let alone a commercial aircraft) release his control stick, allowing the aircraft to begin recovering, but by then it was too late.
The stupidest thing was, the whole thing was avoidable. The reason they stalled out to begin with is the junior pilot decided to begin a long climb, for absolutely no reason, losing airspeed all the while. Then they got into the storm and couldn't see anything, as the aircraft began to stall. Junior pulled back on the stick and kept it pulled back hard until 5-10 seconds before impact.
They fell out of the sky for minutes on end while the other pilot had his stick pushed forward, desperately trying to nose it down and gain some airspeed, perplexed as to what the hell was going on and why the damn thing wouldn't respond.....as the computer system averaged the two inputs, giving a neutral control surface orientation. (What kind of fucking moron designs an aircraft control system like this?)
A few times Junior let up on his stick and the aircraft corrected enough for the stall warning to begin buzzing, then in terror he yanked it back again. Only at the very end did he finally let up and the aircraft began to recover, just as they belly flopped onto the ocean at 90 MPH.
I haven't listened to the transcript, but there's a procedure for taking over controls. Was there ever a "my plane" or "my controls" yell from the captain to the fo? Did the capt confirm that the other pilot had his hand off the stick? I mean, damnit, if you're experienced and shit goes wrong, you must presume that the other people are fucking up until you confirm for yourself that they aren't.
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