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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."
“So, we think that until impact they did not realize the situation, which for the family is what they want to hear — they did not suffer.”
A three minute decent at 10,000 ft/min over the middle of the ocean?
I'm pretty sure everyone onboard knew exactly how that was going to end about half way in.
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.
There is, it's called heated pitot tubes, and the FAA requires them for US carriers.
Your hair look like poop, Bob! - Wanker.
Airbus is run by software. Boeing by pilots.
This is a delusion. Read up on Turkish Airlines Flight 1951. I mean, they programmed 737 to do what? Trust a single radio altimeter known to fail in the worst possible mode, producing false readings? Actually use these readings to automatically enter the landing flare mode with rather subtle indication to the pilots? Autothrottle reverting pilot's inputs? Sounds like scary automation to me.
The reality is, all modern commercial airliners are run by software. If you want an airliner run by pilots, go to Russia and fly some Tupolevs, there are still quite a few left (ehhehe).
My exception safety is -fno-exceptions.
What's most interesting in this case is that the systems warned the pilots of an impending stall, but then once they were in a stall, there was no warning at all, as if they had recovered from the stall. That's really unfortunate.
That's because once the airspeed drops below 60 knots, the input from the angle of attack vane is ignored by the flight computer. The computed angle of attack is how the flight computer determines the airplane is approaching a stall, so without a valid input from the AOA vane, the computer can't sound the stall warning. The AOA vane is just a triangle-shaped piece of metal sticking off the side of the airplane on a little lever, so the airflow naturally positions it, just like a weather vane. As the angle of attack changes, the vane moves, providing an input to the computer. Below about 60 knots, though, there isn't enough airflow to move the AOA vane to a reliable, steady position, so the information is discarded by the computer.
In this case, you're right, it was unfortunate because it provided a confusing result to the crew. They had pulled the airplane's nose up into a stall, and when the airspeed dropped below 60 knots, the stall warning stopped. At one point, the crew did lower the nose of the airplane, which caused an increase of airspeed, which is of course precisely what they needed, but as the airspeed increased beyond 60 knots, the stall warning suddenly started back up. That made them think that what they were doing was making the situation worse, not better, when in fact they were doing the right thing. They pulled the nose back up and then never got it back down until they hit the water. Even when valid, the AOA vane never indicated an angle of attack of less than 35 degrees - generally speaking, almost any general or commercial aviation wing will be well into a stall by about 15 or 16 degrees AOA.
It's randomly on a car forum, but its worth a read. Some guys that know what they're talking about talk about what they think happened. They also include pics of various airbus cockpits for reference.
http://www.mye28.com/viewtopic.php?t=64381&postdays=0&postorder=asc&start=25
Here's the basic story, as I understand it:
- the pilots flew into a thunderstorm
- they were 100% blind, relying entirely on the glass-screen instruments
- once all 3 pitots froze, the redundant computers started disagreeing and then finally agreed that things were ugly
the effect in the cockpit is that a serious of cascading failures were unfolding, likely overwhelming the pilots.
additionally, there would be NO functional indicators for alt, speed, horizon, etc. Once the computers have faulted, they no longer share that information.
Also, as the computers degrade authority, in an Airbus the pilots get MORE control of the aircraft. This means that controls move through larger ranges.
As flight control reverts to failsafe mode, the controls in the cockpit do not "auto-zero". And the forcefeedback goes off line.
Effectively, the pilots are 100% blind, and the inputs they make have no feedback whatsoever. They cannot even tell if they have _stopped trying_ to turn.
Imagine being blindfolded. Your job is to put the end of a 4 ft long stick inside of a 1" circular hole in the floor. Except the stick is a peice of yarn.
That's what their instruments and control apparatus were like.
Now imagine that everything is beeping at you and you are in a plane in a thunderstorm, over the ocean, at night, and everything outside is total blackness.
You're fucked. Thoroughly and completely fucked.
My opinions are my own, and do not necessarily represent those of my employer.
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.
Alt. must have worked it is recorded correctly by the black box, I see no reason to believe horizon shouldn't have been working, so only visual and speed was impaired. That is still a difficult situation, so no reason to exaggerate it.