I am Facing difficulties flying and tunning PID of A large quadcopter (40 inch)

first, thank in advance for help.

i have built a large quadcopter frame (40 inches) with a 165 kv motors and 27*8.8 propellers.

i am using pihawk v4 with the latest stable version of px4 1.12

the problem is as follows when we tried to fly 2 times on position mode/ stabilize mode is just take-off then it became unstable as it can’t stabilize it self and fall down twice.

the idea what can I do if it at least flies I can tune the PID (from my point of view its a tunning problem) but it just flies for a couple of seconds then it falls down so I have no time for tunning.

that’s my log files form the flights

please feel free to suggest any other problem that may cause the instability or suggest any way to solve the problem.


Hi @Shady_Zahran ,
also in the laboratory where i work wehave a big drone (a hexacopter with 1m of diameter) and we had few problems with the tuning.
But in the logs that you posted i can see only that you armed the drone but didn’t fly, moreover while the drone is on the ground i see that the roll and pitch angles changes a lot.
Do you have a flight log?


Hi @salmarc
no, i flew twice but only for a few seconds, then it fell down. i will upload the flight log and post it for you. i noticed that the vibration is too high so i am trying to design a damping mechanism, i think if i solved this one it will fly.