There are lots of Rumors going round in Africa ( the mother of rumors ..) about the Capt having done all the works as trained, incl STAB TRIM cut out and all, but could not overcome the final dive manually .
I do not believe in rumors, especially not in Africa, but a question for those here with experience on the 737.
Is there a speed above which the air pressure on the control surface of the horizontal stab would start to prevent a standard human to activate normally the manual trim wheel ? and btw is this force accurately duplicated in a sim as speed builds up ?
I have flown some ( old) GA aircraft where above a certain speed the cables would just spin around the pulley not moving the stab ( e.g the Super Cub in a steep dive, where lever will turns with difficulty , but does not move the Stabilizer , and before you ask, this happens well below VNe )
I do not believe this would be possible in a modern airliner, but ask the question just in case. .