447 - still speculation

as someone has pointed out, under alternate law g-force remain within limits - the +5g in the simulation is therefore wrong (i don't know the g-limits on the 33o, but under direct law i can do +6 in EY (no, i haven't ever tried it)


Mandala499 writes on airliner.net:

"1. This isn't the case of them not trusting their instruments. They lost airspeed data and the autothrottle (and autopilot) switched off. They would execute the "unrealiable speed indication" procedure which was to set a target pitch and put the thrust to climb. After determining they can start trouble shooting, they would look up the QRH for what pitch and engine power they need for a reasonably level flight (they did as it seems, have altitude data). The problem is, no airspeed data, the QRH warns of stall warnings, which may come from the lack of airspeed data, or a true stall from the AoA vane. They wouldn't know which stall warning was real, and which one was fake. Whilst the Air Caraibes case went through the same thing, they already had manual thrust before the airspeed data was lost, in that case, they knew they had the right speed based on the right thrust and pitch. The crew of AF447 didn't have that luxury (which is the irony of it all!)... they needed to carry out the full "unreliable airspeed" procedure, not knowing if they had the right speed to begin with... Get a stall warning... is it real? or not? Very hard call to make!
2. All this does not mean that this accident is caused by only one factor. It needs to be a chain of factors... otherwise, unless a catastrophic failure, the accident should not have happened. My take on this is:
- Heightened stress and fatigue due to previous bad weather. (Human Factors)
- Alertness obscured by relief that the aircraft seems to have left the storm. (Human Factors)
- Icing (Weather)
- Pitot Tubes blocked (Technical)- Reversion to stress causing higher risk of poorer performance (Human Factors)
- Loss of airspeed data (Technical) and possibility of loosing the mental picture of thrust/pitch relationship/trajectory/condition prior to loss of airspeed data (Human Factors)
- Multiple ECAM messages leading to heightened stress and task saturation (Technical and Human Factors)
- Possibility of stall warnings adding to a confusing situation (technical & human factors).- Further degradation of human performance caused by all the above, leading to degraded analytical capability leading to high risks of error in judgement regarding required action (Human Factors).Beyond this..."
EY