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."
Hey Ken,
You're correct that the STS is not associated with the Stab Trim Autoflight circuit of the Stabilizer trim system. STS is only a function of the Stab Trim Main circuit (the pilots manual flight side of the stab trim) The other side is the autopilots (Stab Trim Autoflight). Hence, the reason why there are two cutout switches under Stab Trim Cutout.
However; The STS
is designed to prevent a stall condition. Three components work together as the aircraft approach the stall - The STS, The SMYD (Stall Management Yaw Damper) and the EFS (Elevator Feel Shift). As the aircraft reaches high angles of attack they work together.
As you said, the STS is only active in manual flight, and in this case may have worked against them.
Cheers