Originally Posted by
safetypee
wheelsright,
‘But do you think that it is possible to use electric trim to counteract MCAS before using the cut-out switches?’
Overall, and biased by the accident outcome, I doubt that nose up trim would have been effective, particularly when considering time of recognition, realisation, and action.
Continued debate considers if trim would / was enabled to override MCAS.
Then, the erroneous rate / power of MCAS design would out perform trim by 9 sec down to 3 sec up.
One last time: Please look at the ET traces from 05:40:00 (first MCAS) to 05:40:45.
This shows MCAS trimming down, an inadequate pilot retrim followed by another MCAS trim 5 seconds later, this second MCAS trim was interrupted after 6 seconds by pilot trim.
This pilot trim continues until trim cutout. Had they waited 10 more seconds while continuing to apply trim the AC would likely be in trim.
Each of these trim inputs clearly show on the pitch trim trace.
All of the above is exactly as described by original MCAS 'disclosure'.
Not sure where the '3 sec up' in your post comes from, the second pilot trim in above is 8 or 9 seconds (hard to read exactly from graph).
They did re-enable electric trim at end, likely a desperate measure, unfortunately they did not provide sustained trim inputs but did re-trigger MCAS one last time.
The trim position trace at 05:43:15 show a slight upward bump after the 2 'blip' showing the electric trim working against the aero loads.
The trim inputs would not show on the trace if still cutout due to cutout switch wiring.