Originally Posted by
capngrog
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".
Not sure if any one replied. There is only one STAB motor on NG and MAX. It can be driven by thumb switches on yoke, A/P channel, MCAS, STS etc. Any movement of stab will be fed back to cockpit trim wheels by a Steel cable drive. It is purely a mechanical feed back. The same cable can be used to manually move the STAB after putting the electric trim motor off. Hope I have not confused the issue.