QuadPlane Unreliable Motor Outputs

I’m working on a VTOL concept with eight vertical motors along with forward motors. I’m trying to configure it as a QuadPlane but am having issues with getting the vertical motors to output properly. Whenever I arm the vehicle, a seemingly random arrangement of motors spool up. After repeated trials, I have seen configurations ranging from two motors to all motors spinning (rarely).

My ESC’s are calibrated and all run in sync. I can verify this with an RC3 passthru to all servo channels. The motors are on channels 5-12 (Aux channels 1-4 on the Pixhawk 2.1). The servo functions should be mapped properly. I have also disabled all the servo functions and let the autopilot map the motors, which wound up at the same mapping I had. As I said, I know that each individual motor is able to get a signal.

I’ve also flown the copter with ArduCopter firmware. Everything works fine there. Then I switched over to ArduPlane V3.9.4 and started seeing the issues. I’m wondering if it’d be a good idea to try the ‘master’ branch of ardupilot. It seems that a lot of work is being done on QuadPlane at the moment.

I would check SERVO_RATE first. Maybe a your ESC’s work better with a higher rate than with the copter code.

Also check BRD_PWM_COUNT.

Also check you SERVOn_MIN and _MAX values for each channel. MAKE SURE they are calibrated to that MIN and MAX value, not something else (like your RX’s min and max).

If checking those doesn’t help, please post a parameter or log file here.

Update: Got it working. It seems the issue was with Q_M_SAFE_DISARM. Once I disabled this parameter all motors are able to arm just fine with the rudder.