Originally Posted by
ecto1
Another possible actor in this drama.
When boeing says to hold the trim wheel, when one study how the system is build and when one studies the data trace (and the misterious ND changes during multiple periods with no ND input).
I believe with sufficient pull and sufficient speed the trim motor clutch will slip and the trim wheels will creep ND.
If you blip the yoke switch and see the trim wheel not moving at a good pace and then you release and you see it slowly moving BACKWARDS, the whiskey tango foxtrot moment may be enough to make you forget about the pedestal switches.
Just another disturbing thought.
A better explanation for the slight drift down while the electrical trim was disabled is that the pilots were attempting to move the wheel by rocking it but were not able to.
The deleted video clearly show how this might happen.
Just because the prelim report has no mention of activity during this time does not mean it was absent, we do not have a CVR transcript just a few excerpts.
The jackscrew cannot back drive the manual trim wheel for the same reason a screw jack holding a car will not slowly lower the car.
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