Originally Posted by
MurphyWasRight
Both of them talk of 'higher control forces may be needed' they do not specifically state that the manual trim might be unusable in a significantly mistrimed state.
I don't know for sure, but I think this statement might be a reference to activation of the Elevator Feel Shift Module (EFSM). This module is one of the 737 systems that may be activated by a stall signal from the Stall Management Yaw Damper (SMYD) computer. Activation is accompanied by annunciation of the FEEL DIFF PRESS light which is one of the symptoms mentioned in the AD.
Relevant quote from the 737 Aircraft Maintenance Manual (AMM)
EFSM Operation
At stall onset, either SMYD sends a signal to energize the dual coil solenoid valve on the EFSM. The EFSM operation occurs when all of these conditions occur:
• Stick shaker is active
• AOA is 8 to 11 degrees more than thermal anti-ice (TAI) biased stick shaker AOA
• EFSM is not inhibited due to low altitude or the airplane is on the ground.
When all of these conditions occur, the SMYDs energize the dual coil solenoid valve. The solenoid valve sends 3000 psi system A pressure to the pressure-operated mode valve. The mode valve opens and sends pressure between 820 psi to 880 psi from the pressure reducer to the system A side of the dual feel actuator. This increases the control column feel forces up to four times nominal feel. The increased feel force makes sure the pilots cannot easily override automatic stabilizer movement to nose down pitch of the airplane.
The FCOM has similar (though less detailed) information, though oddly it states the control forces only double.