Lpbri wrote:I have a good schematic but I don't know how to post it
planecane wrote:While researching documents and watching videos about runaway stabilizer on the 737, I came across the information that the manual wheel has the highest priority and will override any electric trim (automatic or manual). I even saw a video of a pilot in a real 737NG cockpit hold the thumb switch and grab the trim wheel and the trim stopped moving.
I am curious how this is actually implemented in the design of the motor and cable interface with the jack screw. I don't think they can be connected in parallel with each other because I can't imagine a human grip is strong enough to stop an electric motor which is powerful enough to easily move the stabilizer under flight loads. Does anybody have a picture or diagram showing the actual interface of the cable from the manual wheel and the electric motor with the jackscrew?
Please do not turn this into a discussion of MCAS or runaway
CALTECH wrote:planecane wrote:If the manual wheels are moving in main trim, they'll break your wrists. Nothing to really grab on to, as the handles are usually stowed. Autopilot Stab Trim, is a slower rate, one might be able to grab the wheel but stab trim should be stopped electrically, then pop the handles out and adjust stab trim manually.
planecane wrote:CALTECH wrote:planecane wrote:If the manual wheels are moving in main trim, they'll break your wrists. Nothing to really grab on to, as the handles are usually stowed. Autopilot Stab Trim, is a slower rate, one might be able to grab the wheel but stab trim should be stopped electrically, then pop the handles out and adjust stab trim manually.
I will try to find the video but a pilot in a real cockpit of a 737 (not a simulator) held down the thumb switch with his left hand and grabbed the wheel between his thumb and fingers of his right hand and the wheel stopped. As soon as he let go it started spinning again. There is some mechanism that allows the manual wheel to override the electric motor. I can't remember which manual but I read in a Boeing published manual that the trim wheel overrides all other trim.
milhaus wrote:I tried it some time ago. I had extended trim wheel handle, held it and then momentarily applied trim command. It is possible to hold it but force is very high and I think it is possible to catch it and hold when it turns.
GalaxyFlyer wrote:Is it really a single drive motor assembly with a single channel electrical actuator path?
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