mm43
The 13° NU position of the THS will most likely have helped in stabilizing the descent - see post #1393 by PickyPerkins and post #1395 by grity.
Thanks for that picture, mm43. I tried in a previous post by numbers, but your picture is excellent and shows, that the tail was stalled as well , and that trimming the THS ND would have increased the AOA of the THS and thus probably would have had no effect in getting the nose down. Hell, at 60° AOA that THS is nothing more than a big door producing no lift but only drag.
Might be, that the NU input by the PF causing a reduction of THS AOA produced some response (also not the desired one, probably smoothing the ride down), the ND input causing negative response symptoms due to complete stalling of the THS.
I´m familiear what happens when a wing profile stalls (relative airflow from the underside of the profile), however in the case of the THS the relative wind hits the top of the profile, as the THS has the camber on the downside (producing downforce).
Could somebody explain the behavior of an airfoil like in that case? At what AOA would it loose it´s effecftiveness and could even a kind of "reversal" take place?