Salute!
I wish to "revise and extend" my comment re: machanical failure of some type.
1) I did not count the pilot application of trim, so the real count of trim commands to the jackscrew motor is twice my estimate of 25 within 6 minutes,or less.
Did Boeing, in their wildest dreams ever test the mechanism by reversing it from full MCAS authority to manual reposiiton and then back to full MCAS authority limits 25 times in 6 minutes? Looks like the 5 second delay is clearly there after each up trim command from the pilot, then whammo! Nose down and repeat the drill. You know, "STS opposes me and I usually apply opposite trim cmd, but I do not realize this new system is fighting me and my stick shaker is telling me I am stalling but I am not."
2) From what I understand, the mechanical connection to the stab is some sort of drum requiring "x" rotations by the wheel to move the stab.
Is the "drum" connected to the jackscrew?
3) It appears that there is overlap of the STS envelope with MCAS. i.e. 10 seconds after takeoff, speed above 100 knots, 5 seconds to pause after pilot trim command, A/P off.
We see no UP trim cmds after flaps are up, but several before then. So I assume those were STS trying to provide the artifical speed stability mentioned elsewhere.
With increasing speed, STS should be commanding up trim, right? And MCAS is active with flaps up, so it sees high AoA and puts in down trim. But no up trim in the first upset at T=flaps up. Just down trim, so looks like the MCAS rules due to the high AoA, as STS should be commanding up trim as speed increases in the dive!!! I see no AoA criteria for the STS, so MCAS must rule and when/where is not in the FCOM, best I can tell.
4) If the crew is holding or moving the manual trim wheel and the "system" keeps applying trim, as the traces show, then can the trim motor overheat and jam fighting the manual command?
I'm scared, and do not unnerstan why giving "hints" to the crew that trim is required cannot be done with the exising "feel" inplementation versus moving the largest, most effective pitch control surface without notice. And then not making the new system well-known and maybe demonstrated to the crews before their first flight with the new doofer. GASP!
Gums exclaims...