sebaska
Thanks for the input. There is a possibility that the THS could have become inop and the sensors not suss it. It is a long story, and I'll start by noting the PF's Nose down inputs prior to STALL STALL, at which time he evidently relented, and either held neutral, or back ss.
Nose Down. Again, Nose Down. The airplane is not dropping her nose. (This at the post apogee fall off). Again Nose Down, now the STALL WRN.
Each time the PF inputs some NOSE DOWN, the a/c does the opposite, she starts to nose up, and slows. Finally, with the STALL WARNING, PF is baffled (wouldn't anyone be?)
Under what circumstances would the nose rise with down elevator? Just a few. For one, if, instead of commanding PITCH, the elevators were trimming the THS. How is that possible? Only if the THS had lost integrity with the mount, specifically the jackscrew. Had this occurred, the THS elevator system would perform as an all flying tail, a stabilator.
For the elevators to work in PITCH, the THS must remain resistant to them, that is why it does not trim at elevator deflection speed.
Look, this is but one possibility, and I expect it to be ignored or dismissed, but since it is possible, I think it deserves a look.
See BOAC #2121 re: the climb, and consider how the climb could have been extreme due PF input of NOSE DOWN. The climb is the key. Still looking at mechanicals, and FC.