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Old 8th Jul 2011, 12:00
  #1005 (permalink)  
Mr Optimistic
 
Join Date: Jun 2009
Location: Bedford, UK
Age: 70
Posts: 1,319
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A33Zab, presume those conditions for abnormal law are all 'or's'. However, if the a/c already knew that speed was less than necessary for valid AoA would the logic still take the value and change law ?

Took your earlier post on 'locked THS' ie a THS fault not applicable here, to be trying to answer the question asked of how much authority the elevators had v the THS which at >8 degrees and in wrong speed regime was 'not enough'. Mind you, I wasn't clear the instructions following that would be very helpful in such a case.

I have lost track of when auto-trim kicked out but as the more knowledgable have said, unless there is evidence that nose down was wanted it is all largely irrelevant (but mightn't have been had the events followed a different path).

From an outsider's point of view, it does seem a great pity that the system 'knew' or was in a position to know that the a/c had been in cruise at altitude, that it was now descending at an emergency rate, that there was, or had been a UAS event, that the control law had degraded, that the apparent airspeed was insufficient to even motivate the aoa vanes, that THS trim was maxed out.......and still present the information to the crew in a way that allowed them to be misled.

If the Capt. wasn't briefed about the initial climb, he may have started thinking in the wrong direction and never come to realisation.

Given the innumerable paths to failure, I wonder if they will decide this will never happen again now we have changed the pitots.
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