Will Fraser:
Respectfully, a trim function would have more relevance to "upset".
At 2 +/- degrees, a down trim to "zero" would have a steady and insidious
effect on stability relative to airspeeds. With a fault as addressed in the pre-AD testing, trim wouldn't be correctable, and/or noticeable to pilots or computers wrestling with Unreliable a/s data to begin with. Only a few hundred feet (Qantas) can produce a substantial increase in speed. Any established descent, left alone, could be disastrous at flight limits experienced by 447: high, hot, and heavy.
As I said before, this is going to be very stretched to fit this hypothesis:
- we don't know whilch system would act "by itself" to do that in Alternate 2;
- we don't know why trim and elevators control "wouldn't be correctable", why wouldn't they?
- we don't know why the pilots, trying to fly "pitch and thrust" wouldn't notice any pitch issue, being due to some weirdo computer trim settings?
- it doesn't look like F-GZCP was so "high, hot or heavy"; she still had a good margin in all her flight parameters at this point;
- everything (beside the technical root which is very undetermined) may be assumed only if the crew would be totally panicked.
It makes a lot of assumptions and a lot of unadressed root causes in a system already proven by more than 13 millions flight hours...
S~
Olivier