Hi everyone,

Hexacopter Y6 has crashed from altitude of 100m, being in STAB mode.

HKPilot 2.5, ArduCopter 3.1.3
Homemade frame Y6
SunnySky X2212 980kv
Plush 18A with blheli
Props 10x4.5

Video and logs: on GoogleDrive

Look at the end of the video at 9:20.

As you can see it flew almost fine and suddenly crashed for no apparent reason.

A couple of graphs:

ThrIn vs ThrOut:

Roll vs RollIn:

I have insufficient experience to make a conclusion about the causes of the crash. :(
Would appreciate any suggestions.

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Would it be a problem for you to grab a USB cable and get a clean, non-flying tlog for me? There's a lot I can get about your current setup from the extra data mission planner provides in its log. Just pick it up, turn it upside down, 90 degrees left, etc... Thanks!

Upon inspecting your logs a bit, I'm missing the crucial data that will tell me what happened, but the video you got tells a lot :) What baffles me is the drop in throttle almost exactly when the copter starts to tilt up. Did you cut the throttle suddenly? What radio gear are you using? It could also very well be a problem with your gyros, either from vibration or a board defect. If you can, load the board up on your computer and set the logging to IMU, then pull some data and post it. Also, it seems as though something very drastic happened on the input. How are your failsafes set? I cannot think of a time where your throttlein would drop almost vertically in less than a second without somethig happening to the input. 

Also, the Stabilizing upside down happens when you roll past vertical. Keep me updated!

Austin, thanks for your analysis!
Yes throttle was cut-off at the moment of flip by a fixed-wing habit :(
But it was restored instantly. Receiver FS (not APM) was set to center sticks and LAND.
I don't think it could be a gyro problem. At least the log is perfectly confirms all the moves of a copter that is seen on the video.
Vibrations... There are some, but 9 mins of stable flight makes me doubt is could be a problem.
Sure, the copter has some speciality. For example: compassmot about 60%. But that's not so critical for STAB, imho.
I will look if sensors of the controller is alive and will try to make some non-flying logs.

I had an apm 1 that would suddenly have a hardware failure at almost exactly 3:15 from boot. The gyro would physically fail to work at exactly that time. It's possible to be a hardware issue. Keep me posted!

Sure it could be a hardware fault. But I'm sure it would be clearly visible in the log.

I have uploaded a non-flying dataflash and telemetry logs on Google Drive.

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