i will start first fly with Pixhawk on my traditional hely Trex 500, but i have some doubt for yaw control.
I have external Futaba GY401 gyro with servo.
1- if i move my radio stick all ok
2- if i move helicopter (with pixhawk in the table) the gyro work ok
3- if i move Pixhawk … the pixhawk move the tail why?
if there is a external Gyro why pixhawk try to correct tail same an gyro ???
H_TAIL_TYPE = 1
The pixhawk can affect the output to the tail gyro due to the Angle P and Rate PID settings for the yaw axis. Truthfully, I have never used this option and I have no experience to help you set this up. I would think that you would want to have the external gyro only provide rate damping and no heading hold.
Based on my experience with the ardupilot controller, ardupilot has to have control of the yaw axis to control what heading it is holding so that it matches the desired heading. So I would think that the yaw Rate PID gains can be set to zero but the Angle P gain should be left at default initially. The yaw VFF gain needs to be set to some value that causes the gyro to produce a yaw rate that matches what ardupilot is expecting. That would be my suggestions for using an external tail gyro.
Truthfully though, I think you could get rid of it and ardupilot will handle the yaw axis fine. Your call.