Sunday, September 29, 2013

Trim Servo Needs Polarity Change

When I was looking at the PAP to verify the trim tab is doing the right thing, the measurements that I was supposed to get were completely off. In what I thought was full up trim, I measured more than 3" of distance between the AST trailing edge and the TE of the stabilator when the stick was full aft.
A check on the forum confirmed that my trim tab is moving the opposite way: Forum Thread

So, the trim tab TE should go UP when you trim all the way down and the TE should go DOWN when you trim the nose all the way up. Mine is following the trim direction and so I will have to change the polarity.
As the spade connectors were hooked up in a way that this would not be possible by accident, I will swap the wires at the control box.
One possibility to swap them is at the Fuselage connector and swap pins 31 and 32 which provide the pulsed power with changing polarity for the direction.

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