Originally Posted by
ecto1
That's called irreversibility. A screw Jack is irreversible. A ball recirculation screw Jack is reversible. The steering of a truck as an example of the latter.
And to the poster who suggested to stick to what happened and not to what may have happened, I think he is right and I would try to post only probable theories, not merely possible ones. The trim drift is bugging me inmensely but it is probably irrelevant and the rocking explanation also fits.
Not sure context of your comment, whether just to illustrate the difference or suggest 737 uses recirculating ball screw.
To be clear the 737 does not use a ball recirculation screw Jack, it uses a acme nut and threaded rod hence irreversible .
I am not an aircraft mechanic (engineer across the pond) so I could be wrong but a quick search seems to confirm my understanding.