Originally Posted by
HighWind
The question is if Boeing knew that the manual trim forces were too high for an average pilot..
Yes they did. The information below is apparently NOT in the current release of the pilot's documentation.
"One possible explanation is that the loads on the jackscrew due to the severe stabilizer nose down out-of-trim situation were too great for the pilot to overcome using the trim wheel with folding handle. The pilots restored electric trim as a means to trim.
Boeing published a technique in the past that discussed this issue and the need to release the column briefly in a series of "roller coaster" or "yo yo" maneuvers, by cranking in stabilizer trim alternatively with large column commands."
"This is in the 737NG training manual:
Manual Stabilizer TrimIf manual stabilizer trim is necessary, ensure both stabilizer trim cutout switches are in CUTOUT prior to extending the manual trim wheel handles.Excessive airloads on the stabilizer may require effort by both pilots to correct the mis-trim. In extreme cases it may be necessary to aerodynamically relieve the airloads to allow manual trimming. Accelerate or decelerate towards the in-trim speed while attempting to trim manually.Anticipate the trim changes required for the approach. Configure the airplane early in the approach. When reaching the landing configuration, maintain as constant a trim setting as possible. If a go-around is required, anticipate the trim changes as airspeed increase."
https://www.satcom.guru/2019/04/stab...and-range.html