Help! Random Motor surge/twitch

I completed a build of a Tarot 650 Ironman and have done two short test flights. I am experiencing random motor surge/twitch which makes the aircraft unstable. In a previous build I had the same problem. Once, during a waypoint mission, the aircraft suddenly went uncontrollable and fell out of the sky, destroying the airframe.

This quad is built with the following:

APM 2.6 loaded with Arducopter V3.2.1

APM Power Module rated for up to 10S power

Spektrum AR8010T Receiver

T-Motor MN3420 motors spinning Tarot 17" propellers

40 A OPTO ESCs installed below the chassis to minimize voltage spikes due to ESC switching action

MATEK power distribution board with onboard circuitry to supply 10V to the gimbal and 5V routed to the APM output rail to supply power to the ESC circuitry

3691379946?profile=original I have searched the internet for anyone experiencing similar problems - there were many who experienced this behavior but I found no consistent cause or solution. 

The motors run fine when running the motor test in Mission Planner as well as doing the compass/motor calibration.  Yesterday, I removed the props, armed and ran the motors in my basement with no sign of twitch/surge, so I suspect the motors have to be under load, spinning the props. 

Could I solve this problem by tweaking the PIDs? I fear trying to attempt an autotune flight due to the unstable characteristics of the aircraft. 

I would appreciate any help I can get!

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  • I think that I have fixed the problem. I replaced the ESCs I had with Tarot AIR series 40 A ESCs and made sure that the timing is set to "Intermediate".  I had two successful flights yesterday - one of them was a simple waypoint mission that lasted only 3 minutes, but the aircraft flew at a height of 40 meters and it did well  Click here.

    I haven't tried Auto Trim or Auto Tune yet because the switch on my transmitter that I use to trigger these functions is inoperable. I will have to open up the case and see if I can fix the problem. 

  • Have you performed an AutoTune or have you tuned the PIDs manually? If you haven't, the drone doesn't know how to control itself and although it might look stable in certain conditions, in windier environments for example it might lash out of control.

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