I was maidening a mini H-quad with a Pixhawk running AC3.1.  On my first hover in stabilize mode, it worked beautifully. It was hovering perfectly still without any trimming needed. About 4 minutes into the hover, with the quad at about 2 meters high, all the motors suddenly cut off, and the quad just fell to the ground. I have attached the Pixhawk log file and hope some knowledgeable kind soul can help me decipher what went wrong.

Thanks for any help rendered!

Staq

PS: The quad suffered no damage, only 2 broken props. Really wish to know what really happened up there. Dare not fly it at the moment.

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I had exactly the same thing, except mine stopped at 11m high and the damage was fairly substantial, I still have no explanation but what I do have now is a lack of trust.

http://ardupilot.com/forum/viewtopic.php?f=25&t=8769

This is scary, Graham. I am also using Tiger motors, and all original 3DR components. But I am not even doing any flying, just hovering on the spot, and yet this happens. Sad. My faith is shaken now.

I'm not an expert on logs, but it looks like you had a motor or ESC failure, or burp. The following throttle in/out picture shows that Pixhawk suddenly increased throttle out in response to trying to keep the copter stable (while throttle in was steady). The roll/pitch graph shows the tumbling of the copter. The final picture shows RCOut for the 4 motors and it's clear that all of a sudden one motor (channel 4) gets maxed out, presumably because it or its ESC has failed and APM is trying to compensate by boosting its power. Your battery volts and current look okay and there was no brownout of the PIxhawk.

I had the same problem and the only thing that I can suggest is to reload the Arudpilot to the autopilot. 

Looks like a hardware problem, like sync loss. What combination of ESC/motor/prop are you using?

Hi.

Just an idea.
Could it be a Hard Cut off by the own ESC due to low battery?
It sounds like ESC problem

ESC or power delivery problem suspected, could you explain the rest of the setup as I would be happy to try and diagnose

Thanks Tim for the analysis. I thought the current graph showed that the voltage and current reading got cut off abruptly in mid flight while the other data is still being recorded. Just like what Andre was pondering (see below), if in fact a brownout did occur, why did other sensors continue to record the final moments while volt and current recording has already stopped. I do not have my logs with me now but I'll try to post pictures of the volt and current reading vs other data once I have the logs.
Andre, that puzzles me too. Your reasoning sounds plausible. The voltage shouldn't go that low as my batt still has more than 60% charge left after the crash and the no-load voltage of my 3s batt is more than 11.3V.
Thanks Tearig.

Quad is a 250 size H-frame mini quad.
Motor: Tiger Motor MN2204 2300kV (brand new)
Props: Gemfan 5030
ESC: Afro 12A pre-flashed with the latest SimonK firmware
Batt: 2x Turnigy nano-tech 1300 mAh connected in parallel

Just a thought, what if the 3DR power module is faulty? Will it give the kind of problem I am experiencing?
Hi Kabir, see below. Thanks.
Andre, what if the power module is faulty? Somehow it prevented enough power from reaching the ESC but just enough for the Pixhawk to record it's final death plunge. Just a speculating.

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