AF447 Thread No. 3

[DozyWannabe]

@Chris Scott

I think we're more-or-less on the same page, though it looks like I oversimplified my description of autotrim function in Alt 2 to make my point, if so - my bad.

Now, for the duration of this thread I've been trying to keep speculation to a minimum in the hope that others would do the same. To be clear, as an engineer I have no desire to defend a systems design or implementation that is seriously broken, likewise as someone who has had a love of aviation since primary school and a commeasurate respect for pilots I have no interest in blaming them. However to make a call we need more evidence, and the amount of pontificating that's been going on regarding what the computers might have done based on nothing more than anti-Airbus prejudice has been as frequent as it has been sadly predictable.

So, to make things clear:

- With autoflight out, the only thing that the autotrim could respond to (if the system was indeed behaving as designed) was pilot input
- If a hypothetical pilot is unsure of what the autotrim system is doing, he or she can check the position of the THS on the wheel indicator inboard of their seat
- If that hypothetical pilot (either PF or PNF) doesn't like what they see, they can disable autotrim by moving that wheel, which will engage mechanically-driven manual trim for the duration of the flight

How relevant these factors are to this incident is as yet unknown, because the BEA are still sifting through the data and working on the report. Trying to blame either the aircraft and it's systems or the pilot at this juncture is as pointless as it is frustrating, so why are people doing it?

@RR_NDB

At this point, BEA and Airbus know what was being displayed on at least one set of instruments, they know which versions of the software was installed on the aircraft's computers and they know what the timestamped ACARS messages were. That's enough to gain a reasonable idea of what that particular aircraft did in terms of systems behaviour, over and above what control inputs were from the pilots. This should be enough to run simulator tests with crews to gauge their responses to the situation that presented itself, in much the same manner as the Birgenair investigation did. The systems are not so complex that recreation of the incident is impossible.