Not a Bus operator, what causes THS to move? Is it only pilot inputs from the trim button on the stick, or does the computer tell it to move?
Could it be that the pilot inadvertantly thumbed full nose up, while gripping the stick. I suspect that the audio of trim movement could well have been lost among other warnings sounds, and once trimmed full back, recovery would be almost impossible, unless trimmed back the other way.
Given all that was going on, white knuckles on the stick would not surprise me one little bit.
Beachbunny, it isn't what you think. The A330 is a Fly By Wire aircraft and is is designed to autotrim itself in pitch and roll. There is no trim button to accidentaly displace. If I remember PJ2's briefing correctly, the THS trim wheels move silently in response to automatic trim inputs. The THS trim is controlled by Prim computers, any one of the 3 can do it. If the Prim computers are inhibited in some way, or if certain protection features are activated, the trim doesn't move. To understand this takes familiarity with the flight control laws. You will have to break out the books, I'm afraid, to hope to understand what happened.