Originally Posted by
KenV
No. STS is not an auto trim system. Indeed it normally functions opposite to trim. And no it is not designed to "prevent a stall condition."
I do agree on the first part, but even on the NG the second part is simply wrong, as Boeing themselves write in their FCOM that approaching a stall the STS will trim forward to make it harder to get into the stall. It cannot prevent a stall if the pilot really wants to reach that of course, it just makes it a lot harder.
Try to fly it slowly into a stall and don't manually trim, and you will notice the activity of the STS trimming nearly continuously forward in the approach.