Originally Posted by
FCeng84
The 737 stabilizer trim wheel (actually two, one on each side of the aislestand with mechanical connection between) is a basic part of all 737 flight decks. As it is mechanically linked to the stabilizer jack screw nut, it moves to reflect any motion of the jack screw nut. Any extension or retraction of the jack screw requires that the jack screw nut rotate thus will be observable on the flight deck in the form or trim wheel rotation. The flight deck also has a readout showing the position of the horizontal stabilizer.
I may be "picking nits" here, but my (limited) understanding of the 737 NG trim system is that the manual trim wheels are mechanically connected to the jack screw gearbox which rotates the jackscrew, resulting in linear (vertical in this case) movement of the jack screw nut. I guess it could be said that the trim wheels are linked to the jack screw nut, but that link is via the jackscrew itself (that's sorta nit-picking on my part right there). Anyway, my understanding (again limited) of the process is that the jack screw nut is attached to the structure of the horizontal stabilizer resulting in up/down movement of the stabilizer leading edge. Am I correct in my understanding that an electric motor(s) can drive the jackscrew gearbox via yoke-mounted trim switches?
I tried to attach, for comment, a diagram of the 737 NG trim system I had found on line, but was unable to do so, and when I attempted to post a link to the diagram I was informed that I don't yet have the required 10 posts to allow me to post links. Anyway, the name of the site with the diagram is "Satcom Guru".