Is it possible that the warning speaker was broken? It's odd that none of the pilots would even acknowledge it. Or does the recorder record the stall warning noise too?
From what I read from the preliminary report, it's established that the stall warning sounded. If it had not been audible on the CVR, they would probably have noted it.
One problem was that the stall warning stopped due to high angle of attack even though the plane was stalled, and it started again when the nose was lowered and the AOA was in the "valid" region again. This might have confused the pilots in a situation when they already had inconsistent airspeeds etc. to deal with.
Ah, yes, I read that too. It was so frustrating that the pilot kept pulling up all the time, it makes no sense. You'd think that at some point he'd stop and reassess, but I guess he was too confused and shocked to do it...
Yes, maybe a combination of shock, confusion or distrust in the instruments was a factor. It will be interesting to see what the human factors group of the investigation comes up with.
I'm sure that the flight training will also be investigated, there has been concerns that improper stall recovery technique is being taught by some instructors: http://www.caa.co.uk/docs/33/012010.pdf
(And of course, in planes that are not certified for stalls, you can't really practice full stalls and have to train on approach to stalls instead.)
On the other hand, it's not obvious to me that the simulator would behave correctly in this regime either. Having the simulator work correctly in a deep stall is probably not high on their list of priorities. It's possible that this was even the first time ever that an Airbus had been stalled like that, so maybe no one actually knew how it would behave.
Yes, that's possible. I remember reading an article by the author of X-Plane about how stalls are mostly simulated by trying it in the real aircraft and programming something similar, because the airflow dynamics are too difficult to model in real time. (Incidentally, the Cessna 172 is nearly impossible to stall in X-Plane, but somewhat easier to stall in FlightGear. I wonder who's closer :)
> Of course, very little airliner training happens outside a simulator, which can you can stall without damaging anything.
Maybe they should apply mild taser shocks to pilots stalling in the simulator. I'm not being snarky. There should be some kind of physical consequence of making bad mistakes, otherwise it's too disconnected from reality.
The result of that would be pilots doing everything in their power to avoid entering stall and thus learning less about behaviour while in stall and exiting stall. I'm not sure that's a desirable outcome. Sometimes you have to fail to learn.
It's especially frustrating for me because i remember all the times i crashed in a simulator due to stall until i understood what was happening. I don't even remember the name of the simulator, i'm not even an amateur-pilot - but that makes that report almost unbelievable, that something like this happened in a real flight to a real pilot.
unbelievable, that something like this happened in a real flight to a real pilot
Actually, most fatal crashes are "stall-spin accidents", where pilots stall the airplane near the ground without sufficient altitude to recover. But those are not cases where you keep the airplane in a deep stall for 90s. When you stall an airplane in VFR, it's obvious what happens.
No one would persist in keeping the airplane at 20 degrees positive pitch while descending at thousands of feet per minute without realizing the airplane is stalled. But here, without outside references and with obvious confusion about the state of the airplane, it was apparently beyond these guys. (Except the captain, whose comment about "no, don't climb" seems to indicate he was on the right track, but by then it was too late.)
Actually, only the less experienced copilot, Bonin, appeared to be in favor of climbing. The other repeatedly told him to level out or dive, and apparently thought Bonin had listened (which would explain why he was so baffled). As the OP points out, neither that copilot nor the captain seemed to realize that Bonin had been futilely trying to climb the whole time until that moment at the end when the captain ordered him to stop.
One problem was that the stall warning stopped due to high angle of attack even though the plane was stalled, and it started again when the nose was lowered and the AOA was in the "valid" region again. This might have confused the pilots in a situation when they already had inconsistent airspeeds etc. to deal with.