I have been wrestling with a very large quad rotor, 4 of 22 x 8 propellers, 4 of 8000mAh batteries, 3.1m long, 1.3m wide, flight weight of 19.5 kg, running Pixhawk clone and Ublox Round GPS and compass. Mission Planner 1.3.57, and firmware 3.5.6.
I’ve got it all tuned for stable flight, and only recently got the Pos Hold to work, however Pos Hold causes the copter to oscillate in pitch and roll. It was crashing on Pos Hold, but reducing the Pos Hols P value back to minimum (0.5) stopped the crashes. It would appear that reducing it more would actually stop the oscillations, but its at minimum.
For the last few flights, the copter flies for a while in Pos Hold Mode then pitches left and lands heavily sidewards. I can’t prevent it with the radio controls with adding throttle or roll. I imagine if I were higher off the ground the results would be much worse.
I can’t see anything in the logs that would cause this problem, but I’m a complete beginner in trying to decipher the logs.
Any help would be much appreciated.