Flip issue in AC 3.6.11

I had a quad with Cube running arducopter 3.6.11 firmware on it. The initial hover and first few minutes of flight were fine, but about 1 minute into the flight the quad flipped several times and hit the ground in pos_hold mode. I am completely clueless as to what went wrong and request someone to look into it.
PFA for the log file, any help is highly appreciated. #arducopter #development-team

https://drive.google.com/file/d/1aURVQ8NWgt4yNdSQqFob1NLhmWwnDG4X/view?usp=sharing

There was thrust loss on Motor 1 (command to max) with a typical drop in the command on the opposite arm Motor 2. Check ESC/Motor/Prop on Motor 1.

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Thank you for your quick response @dkemxr. The motor and ESC were tested after the crash and the values were agreeable with the manufacturer’s datasheet. I’m at a loss as to what else could be wrong. Any suggestions on where else there might have been a mistake?

That’s what I see. I don’t think it’s wise to use V3.6.11. There were critical fixes in V3.6.12. Or why not update to current Stable?

I had used V3.6.11 on an previous build, everything worked fine in that quad, so I replicated the same build in this quad. I will try using the latest stable version and check. But, could using V3.6.11 be the real reason of the crash? I really want to find an answer for why it crashed to avoid such future mishaps.

@dkemxr is right there was thrust loss on Motor 1

I think it’s clear why it crashed but with regards to 3.6.11 there is this . I see you have a Cube:

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I performed the usual bench tests on the motor and ESC and checked current draw, thrust, etc. Results were fine.
Is there any other test I can do to check their working?