Quadcopter tuning.. Need help

Hi All,


I'm slowly working out the fine art of quadcopter building and flying but i have a few problems.


It doesnt seem very stable, I can takeoff, get it to a certain height, eg. 5m, switch it to alt hold mode, with throttle set at hovering and it just drifts up, it might go up 10-15m, then the motors die down, it comes back down to 5m or so, then drifts back up again.


I have the recommended sonar installed, not sure why its doing this.


Also a few other problems ive seen on the forums, it seems to gain a lot of altitude when flying forwards or backwards at a decent pace, maybe 7-10m gained during short flight forwards. Thats in Alt Hold mode.


And also it doesnt hover very well, tends to want to drift back to the right, have to manually try and hold it in place.


I am leveling the copter as best I can, but i dont think its probably good enough. Could that be causing much of a problem?


Quadcopter is using an x525 frame, turnigy 2217 860kv motors, apc 10x4.7 props/pusher combo.

Stock PID values


Any suggestions would be greatly appreciated.



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  • Could it possibly be interference with the esc's and the sonar?  Or possibly sonar placement?  

    As far as hovering, I would definitely try to tune it starting with Rate Roll P.  If you have a Channel 6 knob, that really helped me a lot being able to dial in a specific value.

  • If it's any benefit, mine does the same - rising slowly with Alt Hold - but only sometimes.  Most times it holds perfectly at low altitudes, even over undulating terrain.  The other day, it was working well but, later in the day and after a battery change, it just kept rising each time I switched across even after I again disconnected and reconnected the battery.

    I suspect the change as it rises (mine changes at about 5 - 6m) is due to the change from sonar to barometer height measurements.  I suspect the sonar is not giving the right height though I didn't have the telemetry running at the time.  I plan to log some data and have a look at what's happening.

    Mine also gains height when I am flying higher and go sideways and then come to a halt.  I suspect that's due to changes in air pressure in the APM housing due to air flowing past.  Tricky to solve.

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