Originally Posted by Loose rivets
The crew were perhaps dealing with not only vigorous turbulence
Vertical acceleration trace is not consistent with flying through turbulence. There is +1.6 G spike as the aeroplane starts its climb, after that, it remains between +1.25 and +0.7G for the remainder of the flight.
Originally Posted by Loose rivets
What I find hard to understand is the 'Deep Stall' nature of this decent.
Trimmable horizontal stabilizer went to maximum nose up deflection. For most of the upset, both elevators were at their maximum nose-up deflection, too. Twice they start moving towards nose-down, first prompted by command from RH stick, second time by LH, but they only get halfway to neutral before new pull on the sidestick sends them back to their NU stops. Seemingly FBW was in Altn law so elevators were trying to satisfy G demand from pilot controls. It goes to show that even when there's no direct stick displacement to control deflection things work out in quite conventional way.