Hardware Failure - ESC or Motor?

Just when I thought I had finally gotten a stable copter, it decided to drive itself into the ground.

I flew today for 14 minutes, attempted a simple auto mission, and aborted it after a GPS error caused some bad headings. then in Alt Hold, the #1 motor stopped dead, the copter flipped, and crashed. Luckily it was fairly low at the time and little damage was done other than breaking my nice home made GPS stand. All of the GPS and compass functionality appear to still be accurate and intact.

When I first armed the copter, that motor stuttered similar to what I have seen in youtube videos documenting SimonK sync issues, but it quickly went away and the copter took off perfectly after that. But I was under the impression that SimonK sync issues affected flat high pole pancake motors, whereas I have NTM 28-30s 900kV’s which are low pole count and not low profile.

Has anyone seen standard shape motors have sync issues with simonk on 4S?

Unfortunately, I thought I was beyond the testing phase and didnt have motors log enabled nor IMU logs enabled, but i do have both the log and the tlog.

you can clearly see the crash here. the roll goes nuts, and so does the pitch. even the APM knew it was crashing.

when looking at the tlog, the crash happens around 85% through the flight. by looking at all the ch1-4 outputs, i can see that the APM sent low signals to the #2 motor and high to the #1 motor in an attempt to right itself.

As far as the logs I have can see, the APM is doing its job, and I had a hardware failure, but I am unsure whether this was the motor or the ESC. would anyone with more knowledge than myself mind taking a look at my logs? Is there any way to distinguish between a motor failure and an esc failure? What about a simonk sync issue? replacing both will be expensive…

The odds favor it being an ESC issue. Motors are so much more simpler and less likely to fail. Since you were well into the flight, it could be an intermittent issue that only surfaces when the ESC gets warm. Personally, if the motor “feels” OK, I’d go ahead an replace the ESC. Of course you can also tie the copter down and run it on full throttle and see if you can get it to fail again. It’s also a way of checking SimonK issues. And BTW, SimonK problems usually arise (if they do and it’s not often) when the throttle is put through abrupt, large changes. It doesn’t sound like you were doing that. So…I’d say flaky ESC.

nope, no massive stick movements.

matter of fact, it looks like i was hands off at the moment of the crash:

the dis-concerning thing is that i cannot find ANYTHING in the logs outside the norm that precedes the crash. The ‘Mechanical failure - Stab’ drop down wont even display, and shows ‘Too much bad data - failing’

anyone have any ideas where or what to look at in the logs?

  • 3.1.2 has a bug that could be a primary or secondary cause of flip crashes (probably secondary). Please update to 3.1.3.
  • ESC or connection failure is far more likely than motor failure.

In your log I can find the RC-Speed is set to 490 Hz

That gives problems with ESC which are qualified for 400hz update speed…

Make sure you do a new calibration after changing the RC-speed setting from 490 to 400.

If have two movies in which the 490 hz update gives a lot of extra twitching, which completely goes away when you reset to 400 hz update…

You can actually hear the differences…