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Old 14th Jan 2016, 09:53
  #89 (permalink)  
khorton
 
Join Date: Jun 2006
Location: Moses Lake, WA
Age: 59
Posts: 53
There are stabilizer trim disconnect buttons on each control wheel. The red "PITCH DISC" T handle on the left, front of the centre console is for jams in the control linkages in the pitch axis - it disconnects the linkage that connects the left and right control wheel in the pitch axis. If you pull that T handle, the left control wheel is connected only to the left elevator, and the right control wheel is connected only to the right elevator, allowing for continued control by one of the pilots after a jam in the pitch control system. A similar ROLL DISC handle on the right side of the centre console is used for jams in the roll axis control linkages.

The autopilot will command pitch trim to zero out any required elevator servo commands, after a short time delay (to prevent it from commanding trim in response to short duration elevator commands). The autopilot receives elevator position information, and I believe it would disconnect if the elevator position did not match the result expected from the amount of servo current, but I'm not completely certain of this.
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