PWM output of PixHawk 2 servo rail with ArduPlane firmware

Hello, everyone.
I’m trying to get my typical 4 control surfaces fixed wing flying for the first time using PixHawk 2 and ArduPlane firmware installed on board.

I’m using a Taranis X9D RC bound with L9R receiver with 5 channels set for control (2 servos for ailerons). The servos are Hextronik HXT500.

However, there is a slight problem with the movement of my servos attached to the PixHawk Main Out servo rails. The servos don’t seem to move beyond 30-40 degrees. I checked the PWM outputs of PixHawk on an oscilloscope and the ON time pulses are within the range of 1 ms to 2 ms.

I then tried to run the servos using Arduino to check if they were working fine, which I figured they do. I also figured that the servos only turn a full 180 degrees when supplied with a PWM signal with ON time pulses in range 700 us to 2200 us.

I then configured my Taranis to work in the extended range of PWM and successfully got outputs in the range 700 us to 2200 us on the L9R receiver. I also calibrated my radio with Mission Planner in the mentioned range.

The problem here is that, PixHawk is somehow still limiting the values of the signal to the 1 ms to 2 ms range, which is not giving me a full 180 degree sweep of the servos.

For my fixed wing to fly, I need a sweep of at least 110 degrees from my servos. How can I configure PixHawk/Taranis to give a signal which will enable the servo to travel that amount?

Thanks in advance for the help. :slight_smile:

Have you tried changing the SERVOn_MAX and MIN parameters, per the documentation?