Originally posted by A33Zab ...
The PF slight but consistent nose up command is a +G request to the PRIMs, the A/C feedback by means of accelerometers however results in a -G.
PRIM deflects elevator and due to negative result drives the THS all the way ANU.
Unfortunate left unnoticed because any hand on the trim wheel had cancelled the PRIM THS orders.
A very enlightening post.
Manual inputs to the trim wheel override PRIM THS orders and the actuals are recalculated. That is how I understand it, and by implication, the PF could have braced himself using the trim wheel?