Originally Posted by
hans brinker
Can anybody confirm/speculate the area (speed/altitude) where it is hard/impossible to use manual trim in the NG/MAX?
The simplest way to explain it is that the harder one has to push or pull on the control column, the harder it will be to use the manual trim wheel. Thus larger elevator deflections, higher speeds, and (I believe) lower altitudes will increase the dynamic pressure on the elevator which then places more pressure on the jackscrew mechanisms. That said, if the stab is kept reasonably close to a neutral trim state, there is little problem in using the manual trim wheel throughout the flight envelope.