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Old Sep 29, 2012, 04:21 PM
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just gotta mess with it!
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North West Louisiana
Joined Nov 2009
6,152 Posts
TX vs Controller trim

I don't think that the difference of 14 points of subtrim in your TX to 20 in the FBL controller to get the arm centred means there is any sort of error. It merely means the sub trim in the controller is set slightly finer.

I am beginning to wonder exactly how the FBL controller (CX in my case) is handling trim. If I hook up my servos directly to my RX, any change in TX sub trim is reflected in the end positions of the servo arms, thus using TX sub trim won't result in differential throws. The only thing to watch out for is not exceeding the angular range of the servo - for example on a CCPM cyclic servo, where combined collective and cyclic stick inputs can drive the servo close to the end stops. Therefore as a general rule, it's sensible to limit sub trim to as small a value as possible, by playing around with different servo arms, the ideal ones being those five-lobed ones, where you can find the arm that works best and cut off the other four.

With the CX, it seems like maybe trim values only affect servo neutral, but I need to do more tests to check that. Of course you have to allow for the fact that what happens in the air may differ from what you see on the bench.
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