Quadcopter starts to spin during takeoff

Hi All,

I’m sharing an observation regarding my quadcopter that I’ve faced during my testing.

I’m using an SBC connected to the FC runnning ArduCopter V3.6.2 (25f72536).
The SBC controls the drone by sending RC commands via MAVLINK protocol. I use mavproxy to create a module to control the drone.

The issue is that when the SBC orders the drone to takeoff, it starts to spin in anti-clockwise direction. The drone rapidly spins and takesoff. It would results in the drone going veritcally up while spinning contiuosly. We also have a backup radio to control the drone manually and have added a feature to switch from SBC control to radio control.

What we have observed is that this happens when I run the script and then turn on the backup radio for the drone. Could see this behavior >90% probability. Whereas if the radio is turned on and then when i execute the mavproxy module the issue doesn’t happen.

I’ve analysed the module to ensure that I’m not giving any abnormal values. Also I’ve verified from the flight logs that the RCIN are normal.
From the flight logs I could see that the RCOUT values for 2 motors are higher that the other and that could indicate the spinning.
I’ve also attached a flight logs for the issue.

Could you please help me on this issue.
Thanks in advance.

00000004 .BIN (148 KB)


Thanks for the help.
Apart from the power sequence of mavproxy control and radio my drone works perfectly. It’s only during the above scenario that spinning happens other wise it works normally.

Also when I don’t use the SBC and do a manual flight it works noramlly.