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Old 03-27-2011, 06:25 PM   #95 (permalink)
zeeflyboy
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Join Date: Oct 2009
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Just a note as to people asking/talking about subtrims on pitch.

I too have zero-ed my pitch at mid stick as it was a bit off. I got it as close as I could mechanically which left me with a slight positive pitch, and then used 9 clicks of subtrim to back it down.

The concerns regarding subtrims with flybarless are justified, however logic suggests only in the axis that the flybarless controller actually controls.

Depending on how the system works, subtrim on the aileron/elevator/rudder will either be ignored by the flybarless as it calibrates to zero at start up, or indeed seen as a constant roll/yaw/nick rate request. I haven't experimented yet to see which is the case. The important point here is that the flybarless controller controls the servo position, not the transmitter... the transmitter makes a rate request that the flybarless controller tries to satisfy with whatever servo position is required.

Pitch however falls outside the flybarless controller's remit, as it doesn't control the pitch - this is directly dictated by the transmitter throttle stick position.

It should therefore be safe to use a small amount of subtrim on the pitch channel, and the pitch channel only. Do be aware though that larger amounts will offset the servos from centre and could lead to overdriving when inputs are summed (eg, full collective and cyclic) so the less you have to use the better.
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