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Flight 447 'Black Box' Decoded
fermion writes "An initial report has been released by the BEA concerning the details of the last minutes of Flight 447 en route from Rio de Janeiro to Paris. According the report, the autopilot disengaged and stall warning engaged at 2 hours 10 minutes and 5 seconds into the flight. Less than 2 minutes later the recorded speeds became invalid. At 2 hours 14 minutes and 28 seconds, the recording stopped. The final vertical speed was recorded around 10,912 ft/min."
1. Unless it's pressurization system was faulty (it wasn't) the pressure change wouldn't have been great.
2. Unless accelerating, you wouldn't know you were going down (or up, or banked or upside down...).
So the claim that the passengers probably didn't think it was anything more than turbulence is not hard to believe.
It is perhaps surprising to non-pilots that you can be in unusual attitudes and not know it, pilots however are acutely aware. VFR (Visual Flight Rules) pilots flying into IMC (Instrument Meteorological Conditions - ie, zero visability) is a big cause of crashes, not because they can't see where they are going, but because they don't know which way is up.
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To a layman like me, it is amazing that without the benefit of all the data that has been recovered from the flight data recorders, experts were able to get so close to the mark.
Airbus records remotely some telemetry data, this is how experts where able to make a sensible guess.
Surely, a species with such (magical?) technical expertise could have expended the effort into preventing such a failure?
Yes, of course. This will be taken in account in future projects and into airplane maintenance routines. But ya know, those damn birds are already very reliable. It's a disaster, my heart will be always with the families. But some times, you know, shit happens. We should always be aware of how fragile the human condition is and understand that despise all of our hard work into making things safe, some times the unexpected happens and a disaster awaits our destiny.
Yours sincerely,
Someone who deals with safety systems (not at Airbus ) and it's tired to see people blaming designers: we did our best.
I have been reading the report and there are some strange interesting passages. Here is a partial summary, focussing largely on pilot control inputs
Copilot is PF. Captain is PNF.
2 h 08 min 07: "...turbulence increased slightly and the crew decided to reduce the speed to about Mach 0.8"
2 h 10 min 05: "...the PF made a left nose-up input. The stall warning sounded twice in a row...Autopilot and auto-thrust remained disengaged for the rest of the flight."
2 h 10 min 16: "...The airplane’s angle of attack increased progressively beyond 10 degrees and the plane started to climb. The PF made nose-down control inputs and alternately left and right roll inputs... The airplane was then at an altitude of about 37,500 ft"
At 2 h 10 min 51: "...The thrust levers were positioned in the TO/GA detent and the PF maintained nose-up inputs...The trimmable horizontal stabilizer (THS) passed from 3 to 13 degrees nose-up in about 1 minute and remained in the latter position until the end of the flight...The PF continued to make nose-up inputs."
2 h 11 min 40: "...The airplane’s pitch attitude did not exceed 15 degrees and the engines’ N1’s were close to 100%..."
At 2 h 12 min 02: "...At that moment, the thrust levers were in the IDLE detent and the engines’ N1’s were at 55%. Around fifteen seconds later, the PF made pitch-down inputs..."
This much seems clear: the airplane was cleared for flight level 350 (35000 ft), and was likely at that altitude when the trouble started, assuming the altimeter was functioning. Stall warnings went off, and the airplane climbed to 38000 ft. It then descended rapidly, it seems with a monstrously high angle of attack. It also seems from the report that the nose of the plane was mostly pitched up through this, though I am not absolutely sure on this. This would imply a very bad stall...essentially the airplane was falling from the sky. One can speculate that the pilots were doing their best to recover from the stall with imperfect data on their airspeed.
To me the important period was between 2 h 08 min 07 and 2 h 10 min16. There was a decision to reduce speed, which would entail a reduction in thrust. Two minutes later, there was a stall warning, implying that the airplane's airspeed was out of the very narrow range required at that altitude (plus/minus 10 knots according to the Nova documentary, though I'm not sure it's so narrow). The question is, what caused those initial stall warnings? How did the airplane's speed get out of the proper range? Did the pilots forget to increase thrust after the autopilot reduced it? During those two minutes, was the airplane catastrophically slowing down?
This and no other is the root from which a tyrant springs; when first he appears as a protector - Plato (423 to 327 BC)
I disagree with that synopsis, my understanding is the pilot started fighting the autopilot without disengaging it. The plane might have been fine if it had totally disregarded the pilot.
My understanding of what happened here is the autopilot was automatically disengaged (because it didn't believe the airspeed reading it received) and handed control over to a human, who proceeded to stall and crash the plane. It's too bad the autopilot wasn't programmed simply to do the best it could instead of handing over to the pilot (in the errant assumption a person would do a better job coping with the situation).
It seems very scary that on an aircraft with everything working but the airspeed indicators (and I understand that those are very important), after more than 3 1/2 minutes the aircrew was unable to prevent the plane from hitting the ocean. This was a state of the art aircraft. Makes you wonder how many close calls there have been that luckily didn't result in catastrophe.
I find it highly unlikely that clogged pitot tubes would take out all the static and gyroscopic instrumentation too. That would be a phenomenally stupid design, and would rank the Airbus lower than a Cessna 150 in terms of instrument reliability.
The information in the report is preliminary, and there has to be more to this story. Even the lowliest weekend warrior pilot earning the most basic instrument certification has to demonstrate an ability to fly in IMC with multiple instrument failures.
What I want to know is why the PF pulled the stick back to the stop with the stall warning blaring in his ear. There's no way an airline pilot would make such a stupid mistake—unless there's way more to this story than what we're reading in the preliminary report.
WRONG WRONG WRONG FUCKING WRONG!!!
All Airbus cockpits have "old fashioned" analog devices, in particular the artificial horizon. Also, there is no force feedback on the sticks.
Please don't spout crap about an aircraft that you know nothing about.
If you lose the computers the aircraft flies like any other normal aircraft. You are not fucked in anyway.
This is more like a complete loss of situational awareness by the pilots - actually a very common problem that is independent of the aircraft type, manufacturer and whether is the "computer" controlled (whatever that fuck that means). Similar things happened to the Turkish 737 crew who crashed at Amsterdam a few years back, the Cali 757 accident, the Strasbourg A320 crash etc etc
ps: I fly an E170/190 for an airline that also happens to have A320s ....
It is now. It did not use to be. In the two companies I flew airbuses in, we just trained the impending stall under normal law, and normal flight under alternate law. Sure, pilots are supposed to know that alternate law does not provide stall protection, but this was never trained in the simulator. In any scenario where stall could be an issue (wind shear, terrain warning, etc...), we were always taught to pull back on the stick all the way and let the fly by wire do the rest. Let people fly like that for 10 years and what do you get?