A List To Learn From
Like others in this forum I suspect that no one factor will be found solely responsible for this tragic loss.
Having read (I think) every post in this thread, as well as both BEA reports, I have tried to make a list of ‘things we should learn from’ so as to avoid a repeat.
I would be interested to hear if I have missed out anything significant. Before I get flamed, I should point out that I am not a qualified Aircraft Engineer, my flying is now in the past tense, and these are my subjective opinions!
The aircraft appears to have flown into a storm. It is unknown whether the decision not to detour further away was due in part to a fuel constraint.
Airbus considered the need to upgrade to the pitots only warranted a Service Bulletin, rather than an AD. This is surprising given the number of documented previous occurrences of unreliable airspeed and their obvious safety implications.
Air France appears to have taken over a year to start to implement the SB. AF447 had not been upgraded.
A lack of visual and aural cues from the controls (no yokes moving, no throttle levers moving, no “tick, tick” from the HS trim) may have denied the crew warning of the impending AP disconnect.
The design of the stall warning system, whereby it is disabled if the apparent airspeed (i.e. as measured by the pitots) falls below 60kts is astonishing, given the known pitot icing issues. It beggars belief that such a system can get through design and certification.
The Airbus Stall Recovery procedure in force at the time, which the crew appear to have been following, started with “TOGA”, and had no mention of either getting the nose down or checking HS trim. No distinction was made in the procedure between recovery from an incipient or a developed stall.
The disabling of the HS autotrim once in Abnormal Law has apparently been a factor in other accidents; it remains to be seen if it was a factor here.