Originally Posted by
Speed of Sound
The fact that some crews are struggling to turn the trim wheel in some situations can be classed as partly a lube problem because some of the effort that they are putting into turning the jackscrew is being lost in overcoming frictional forces caused by less than perfect lubrication.Probably not a great deal but it is some, and if I were a Boeing engineer faced with the possibility of having to retrofit 7,500 new servo motors and clutches I would be looking at every possible way to make the existing manual trim system more efficient.
I enjoy the systems discussion as much as anyone here, however, strictly from an operator perspective, knowing how all the forces line up to create the unwelcome resistance within the manual trim system is far less important than knowing how to avoid the situation in the first place.