Hi,
While trying to take off with a large X8 Copter (1.4m/T-MOTOR U10 II KV100/28x8.4 propellor/Pixhawk 2 running ArduCopter v3.6.8 (ChibiOS)) we had a flip-over which we don’t understand. Attached is the log, we cannot really find a clear cause for the crash, hopefully you can help us. Motor wiring and directions have been checked thoroughly (the drone has flown correctly before), as well as the propellor orientations. The flight mode was STABILIZE. When the drone is about to take off the pilot notices the right leg coming off the ground (thus, a strong roll motion to the left), and cuts the throttle immediately. RCIN.Ch3 (throttle) is cut when roll = -16deg, we tested manually and the tipping point for the drone in the roll direction is 37 degrees. So we’d expect the drone would fall back to its feet. However, it kept rolling to the left until it finally flipped over on its side. According to the logs, no pilot input was present for roll and pitch directions. Two motors on the right side (RCOU.C[1,7]) do seem to have a non-idle PWM value (although not very high), and as far as we can see these motors are the only things that physically could have toppled the drone like this. Are we missing something here? We don’t really understand why these motors were not all at the minimum PWM (around 1200), but suspect the drone may have been trying to yaw. It is nevertheless surprising that this was powerful enough to flip over the drone.
The log: https://drive.google.com/open?id=1cQ6VyiBUCsuD23i3rzEDTbJ1sWoCJdGY