AIR FRANCE 447: New details suggest the Airbus design contributed to the crash.

[mgh 89]

I'm more interested in what caused the stall.

 

In both cases the stall was caused by a pilot applying nose-up elevator in response to a stall warning - stick pusher in the case of Colgan,; audible in the case of Air France.

[TurboTomato 90]

How many times do I have to say this - they weren't pulling back in direct response to the stall warning sounding, and after the AoA had reached a certain amount the stall warning was sounding when the nose was pointed down and stopped when it was pulled back up.

 

Other than both crashes involving a plane and a stall there is very little to compare between Colgan and AF447.

[KevinAu 441]

Stick pusher activates when the AoA is increased over the AoA that caused the stall alarm to activate. It does not know the difference between a tail and airfoil stall. The Dash-8 is not FBW. It is a conventional setup of pulleys and cables. And just a FYI, a stall (especially a tail stall) can happen at any speed.

 

A tail stall is not due to excessive aircraft aoa. It is caused by the loss of the tailplane's ability to provide downward 'lift'. When the tailplane cannot push the tail downwards anymore, the aircraft will drop its nose. It can happen at any actual aoa of the aircraft. It is not related to the actual aoa of the aircraft, as measured relative to the main wing and motion of the aircraft by the aoa sensors. Therefore, there will not be a stall warning since the event can occur well shy of the stalling setpoint. The nose of the aircraft will drop, sans any kind of stall shaker or pusher activation. Without those cues, the pilot, as a basic student pilot, is trained to perform what we call a nose low unusual attitude recovery, which is simply to pull back on the stick and reduce power. Which coincidentally, are also the exact actions required to recover from a tail stall.

 

If you want to focus on what happened before the stall event to cause all this grief, you should look back to each of those pilot's initial training days and ascertain what kind of basics of aviating their flight instructors had tried to instill into them. Because the actions required to avert tragedy here were actions that all aviators should be capable of as you are capable of inhaling air into your lungs on a daily basis. That they were not capable of them speaks more about their initial training than it does anything else about equipment or procedures at this level.

[KevinAu 441]

How many times do I have to say this - they weren't pulling back in direct response to the stall warning sounding, and after the AoA had reached a certain amount the stall warning was sounding when the nose was pointed down and stopped when it was pulled back up.

 

Other than both crashes involving a plane and a stall there is very little to compare between Colgan and AF447.

 

Those two accidents are going to be spoken of in the same discussion because they both point to an identical problem. Pilots who were unable to perform a stall recovery.

[Airbrakes 0]

I agree that they weren't able to perform a stall recovery, however I do not think requiring more TT is the solution to the problem.

[TurboTomato 90]

I'd argue that point. The AF pilots were perfectly capable of recovering from a stall, they were simply put in a situation of massively conflicting information, mostly likely total loss of spatial awareness. They couldn't confirm the aircraft was stalled let alone what the IAS was. Colgan was a result of fatigue and the wrong reaction much closer to the ground. Much more simple.

[mgh 89]

How many times do I have to say this - they weren't pulling back in direct response to the stall warning sounding,

 

Look at the FDR traces in post #156. While the stall warning is sounding continuously the pilot takes the aircraft from about 5 deg AoA to over 30 deg and ends up with the elevator on the full nose-up stop, Isn't that "pulling back in direct response to the stall warning sounding"?

[FLEX1978 373]

I'd argue that point. The AF pilots were perfectly capable of recovering from a stall, they were simply put in a situation of massively conflicting information, mostly likely total loss of spatial awareness. They couldn't confirm the aircraft was stalled let alone what the IAS was. Colgan was a result of fatigue and the wrong reaction much closer to the ground. Much more simple.

 

You are one a few people that actually post some sense around here.

 

Regard

[KevinAu 441]

I'd argue that point. The AF pilots were perfectly capable of recovering from a stall, they were simply put in a situation of massively conflicting information, mostly likely total loss of spatial awareness. They couldn't confirm the aircraft was stalled let alone what the IAS was. Colgan was a result of fatigue and the wrong reaction much closer to the ground. Much more simple.

 

The most important things a pilot's first flight instructor is supposed to give him are the simple and basic rules to live by that can come back to him as a tiny voice in the head when they are out there on a dark night, with surprise warning bells, massively conflicting information, and complete loss of situational awareness, that if they had just remembered, would have saved their lives when they are reduced down to a thumb sucking baby who has no idea about what is going on. Rules such as 'pitch for speed', or 'speed is life', or 'when in doubt, roll inverted and pull.'

 

Colgan had little to do with fatigue, although it is nice to try and play that up and I guess we got some miles out of it. But honestly, if you look at what he did, he moved those controls like a student pilot on his first stall lesson after not paying much attention to his instructor's ground lesson. That is all there is to that. And if you looked at his record, you'd see that he never did very well learning to fly.

[TurboTomato 90]

FLEX, cheers I appreciate that.

 

Re the data, simply mapping the initial stall warning to a pitch up response is missing huge amounts of a much bigger picture. Here is my (crazy!) idea on what might have happened: initial stall warning sounds at 2h10m10s; this is identified as potentially false as they've realised that the IAS may not be correct. IAS gives essentially worthless information from that point on. Nothing out of the ordinary so far; the throttles are still at CLB until they realise they will end up too high at which point they throttle back. 2h10m51s stall warning sound starts continuously - within 5s TOGA power is selected. 2h11m07s (11s after TOGA selected) CAS ISIS changes from 129kt to 183kt. Potentially this is showing that the TOGA is working and bringing the speed back to a safe value. If you look at the data on p111 you see that the nose is pitched up but the captain's input is mainly down with spikes back up. The sidestick is then held down until the stall warning stops and the pitch ends up down at about -10. But then the stall warning sounds again at 2h11m53, 8s after it had stopped. Then at 2h11m58s 'I have a problem it’s that I don’t have vertical speed indication' and 'I have no more displays'. So no idea how fast they are dropping and no visual references outside to confirm anything. The most telling thing from then on is that the pitch value graph is an almost perfect inversion of the stall warning alert. At no time was the word 'stall' mentioned by any of the pilots.

 

If it was such a simple case of these stupid pilots pulling back all the way into the Atlantic then why hasn't the BEA concluded such and why is the investigation still ongoing?

[KevinAu 441]

Because the conclusion needs to be politically acceptable.

[TurboTomato 90]

Right, now we see the agenda...

[KevinAu 441]

Btw, are you sure about how you are reading the graph? Notice that the negative values are pitch up. The right side stick was entirely in the nose up position through the last half. So he did hold that stick back all the way to the ocean.

[TurboTomato 90]

My mistake. He held it back and the response he got was that the stall warning stopped during the initial continuous stall warning. Everything else still stands particularly the last part where the pitch and stall warnings are related.

[ZachLW 37]

Look at the FDR traces in post #156. While the stall warning is sounding continuously the pilot takes the aircraft from about 5 deg AoA to over 30 deg and ends up with the elevator on the full nose-up stop, Isn't that "pulling back in direct response to the stall warning sounding"?

 

No, it's not. It is complete disregard to the stall warning.