infrequentflyer
Do we know that it's THS or just speculate ?
It is simply logical considering the mechanics of the situation. The aircraft in pitch is effectively bar on a pivot (a seesaw if you will). The THS additional incidence had the effect of applying additional downforce on the tail. Without that additional downforce, the elevator by itself would have met its match long before and the nose would have fallen.
You can see a pitch oscillation as the aircraft begins to stall with PF actively countering and the THS angle continually increasing.
When the THS trim could go no higher, PF's strategy changed from some nose up, some nose down to steady nose up-he was trying to make up for the additional THS trim angle he no longer was receiving.
Dozy
...in this case it was doing exactly as it was told, as would any other aircraft.
Conventional airplanes recognize aerodyamic reality and drop their nose in the stall (assuming they are not T-tails)
FBW aircraft continue to follow their instructions and in the case of the A330 can grab additional resources (THS nose up trim) that no sensible pilot would apply in a stall.
Because Alternate Law is by definition a degraded systems status. Any and all stability protection in Alternate is "soft" and as such can be overridden by pilot input, because the design assumes that the pilot knows more than the systems at that point.
Sounds to me that they threw out the baby with the bathwater. If AOA had stopped the THS trim at 3 degrees or so, AF447 would have likely begun to bob up and down like a Cherokee or Cessna 150. Don't you think one of the guys in the front office would have gained a clue?
The one problem with AOA is that the A330 AOA envelope reduces at higher Mach.
Probably all they needed to do was use the Mach at dual ADR loss for setting autotrim upper limits as in Normal law. If you really needed more trim later, you could do it manually.
Regardless of the THS angle, all that needed to happen was for one of them to push the nose down in response to the Stall Warning alarm that was going off for nearly a minute and the result would have been a scary ride for the passengers and coffee without croissants for the flight crew after landing in Paris.
Dozy, I wasn't there to see what they were up against nor were you, but it is one thing to put a foot through the bars of the tiger's cage and another thing entirely to open the door and walk in. If the trim had stopped earlier, the probability of successful outcome would be much higher.