Originally Posted by
BOAC
- it is not a 're-direction'. It is a contributary factor. Without it one hopes this deficient crew (and THY at AMS, and TOM at BOH and........and....) would have noticed the need to keep trimming?
I'm not going to say the crew were "deficient", in this particular instance some bad choices were made and, as with a lot of CRM-centric accidents, they never managed to work as a team. They were let down much earlier in the chain by their airline and the regulator, however, and yes - there are some questions about the aircraft systems behaviour.
Autotrim is a fundamental aspect of how the Airbus FBW system operates normally, and causing it to drop out in an abnormal situation when there's nothing stopping it from working is probably overkill. The way it behaved is a contributory factor in this instance, however I have trouble accepting this behaviour:
as "insidious". It is a clear and definite response to the SS input, going from -3deg to -13.5deg in around 45 seconds.
Theoretically there may be an issue with a small climb component causing the THS to trim NU in a less obviously-perceptible way, but that's not what happened here. Re-instating the limits apparent in the A320's system would probably help matters - either limiting to a smaller NU trim in Alternate or halting NU trim entirely with the stall warning (which you can see coming on just as the THS starts rolling NU).