Originally posted by infrequentflyer789
1. The loss of airspeed information caused a change in the FCS mode, which the pilots seemed not to notice, as they made no mention of it;
False. Mode change noted and read out. Read the CVR in the report.
I'll concede that — at 2h10min22.1 it was indeed mentioned, but the import was lost in the confusion that followed. I'll amend my post. Thank you.
False. The THS didn't wind up until they were already stalled, and there is no evidence autotrim failed - with nose down control inputs the THS would have followed allowing recovery (plenty of SIM sessions and theoretical models covering this on the tech log thread).
Stall Warning occurred at 02h10m45s – at that time the THS was already moving ANU from its cruise trim condition;
what sort of sane FCS/SW engineering logic will allow ANU movement of the THS in a stall?
Without Aural/Visual warning to the pilot?
We've seen that before — A300-600R Nagoya, A320 Perpignan.
In fact The algorithm controlling the stabilizer has accumulated a large value on a forward integrator and this value is much larger than the actual stabilizer deflection limit. Because this integrator has built up a value well past the actual stabilizer limit, the stabilizer did not come off the ANU stop when the pilot reversed his input – as happened several times – until the integrator wound back down to the limit value. The integrator never unwound over the rest of the flight (fall) to impact.
Since you appear to consider this phenomenon to be OK (Designed as required for certification.??) I don't deem it necessary to address the remainder of your comments.