It’s all normal until suddenly it isn’t. In terms of acceleration, +2,500fpm to -18,500fpm in seconds is substantial. That’s a change in velocity of >100m/s in the vertical plane in a very short time which would imply considerable negative ‘g’, most likely outside the aircraft limitations and possibly enough to cause structural failure...
The egg or the chicken?
What caused what?
Did a hard negative G manouver cause the elevator (Hor. Trim,...) to fail, or did it fail by unknown reasons and cause the plane to dive?
Today it has been 1 year exactly since the Germanwings accident.
Is something like that thinkable? I doubt it.
The most probable scenario to me is some kind of failure on the tail, that caused the nose over, and the inability to roll it back to wings level.
Maybe ice, or the combination of ice and an A/P disconnecting. I always hand fly in heavy ice...
Nic