Pixhawk Tricopter Servo Drift in Tail Mech

I am working on my first tricopter using a Pixhawk Flt. Controller. The tail servo is attached to motor channel 7. When I “arm” the copter, motors spin up and I can move the servo but it drifts when I throttle up. I am fairly new to this. I believe it is a setup issue. Need help, really don’t understand how to address this issue.

I hooked a scope up to the PWM pin on motor channel 7, the pulse goes from 1.5ms on up to 1.8ms… on its own.

The servo position is scaled with throttle, with more trust the servo needs to move less to achieve the same yaw. So servo movement with throttle is expected.

In general behaviour on the ground is not representative of behaviour in flight, your cutting off the closed loop feed-back because the vehicle never moves in response to its outputs.

So long as the servo is correcting in the right direction you should just give it a test fly. Setup E-Stop on a RCx_OPTION in case its goes wrong.


Thank you for the help. I have gone and checked out the servo and my assembly. Putting things back together now.
How do I determine whether it is “correcting in the right direction”? When I power up, the servo goes to its center ( The motor position at 90 degrees )
I may be ok. Want to try now.

Again, thank you for the response and the incite. I want to learn more about this…

Hello Peter,

I have made some progress with my Tricopter. I have an Tail wagging issue now. I can power on my copter, when I throttle up the tail motor servo oscillates wildly. I know this is a tuning issue (hope it is).
Can you help me to understand what is happening. I read something about changing the Yaw Stab value from the default, 4.5 down to 1.5. Not sure where I find this.

Hope you are well. thank you for your help. Still getting use to navigating this forum.

Take care,

Steve King