Originally Posted by
LandIT
I also am stunned.
Do we know who or what caused the THS to go to 13 deg and stay there. Surely this extreme setting is a major contributor to the disaster. If this was HAL then surely Airbus has some explaining to do. I think this is not the first time the THS on an Airbus in trouble has gone to a high setting and the crew didn't notice, or am I wrong?
Not wrong - Perpignan crash. Autotrim put the THS high, in response to pilot input, and then autotrim dropped out - but the pilots never retrimmed manually (leaving them with no pitch autority).
However, this is not a FBW issue, nor just a Bus issue - this sequence:
- autotrim trims THS up
- a/c approaches stall
- autotrim drops out
- pilots fail to re-trim
- no pitch authority available to recover from stall
Is common to a number of incidents and fatal accidents now, and
it's happening on non-FBW (eg. 737) planes as well.
Note: I am unclear as to why THS went up in this case, first reading of latest BEA document suggests it was in response to PF nose-up inputs, not HAL It's also not clear if autotrim ever dropped out (or stopped working) in this event.