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Date:  3-10-2011
Number of Hours:  1.50
Manual Reference:  
Brief Description:  Pitch Servo Change

The Model C pitch servo, originally recommended by TruTrak, isn't strong enough, IMHO. It was incapable of moving the elevator on the ground (there is about 6 lbs of friction in the elevator system). In flight, it was capable of maintaining altitude in smooth air, but not so in turbulence, requiring frequent trim changes. The Bearhawk trim system is very sensitive anyway, and it was easy to get into an oscillatory profile. I obtained a Hi-Torque servo upgrade from TruTrak for $750 and installed it. A shorter pushrod was needed and trimmed and tapped. Care was taken to avoid binding and an over-center condition, which could lock up the pitch system. Because the Hi-Torque servo uses a 4:1 gear reduction servo but the same motor, it was necessary to remove a motor control jumper on pins 1 & 2 of the Sorcerer panel connector and to increase the pitch activity. In flight, I was able to initiate an autopilot driven 600 fpm descent with only a power reduction to avoid Vne. No trim change was needed, and altitude control was much more precise in turbulence. Previously, when the Model C pitch torque was exceeded, the servo started clanking, and that didn't happen with the new servo. The weight change was .23 lbs, or negligible.
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Overall view.

Overall view.

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Stick aft, no binding.

Stick aft, no binding.

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Fwd stick, no over-center.

Fwd stick, no over-center.

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