First of all, let me introduce my quad configuration and the crash details.
We have a Tarot T960 hexacopter configuration based on a APM 2.6. We have tested many times and it flies really stable.

This morning, we decided to do the first flight of a modification based on this frame, but in this case, just with 4 arms, in quad configuration. The controller in this flight test was a pixhawk with APM 3.2 version.

We were testing loiter mode in order to measure the time autonomy with a new battery ( Multistar 10000maH). It was stable and after 3 minutes of flight, something happened and drone fell free and crashed.

I have downloaded the log, but after analysing it, I can not figure what happened and which was the problem.

Please I need your help in order to determine which problems we had in order to not commit the same mistakes.

Thank you!!

* I recorded the crash, so I will update the topic with the link of the video. Probably it helps in the analysis.

*I have attached the log file.

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Thank you so much Stephen Zidek for your clarification. As you said, the region with zero current at the first minute is due to the landing of the quad, I did a first flight in order to be sure everything was OK ( with no luck).

I agree with you and I think is mechanical failure because the log doesn't show any sign of software problem. About batteries... well, I used similar batteries in a hexacopter with same ESCs and motors, but it was the first time in this configuration and I wanted to test the flight autonomy on this platform. The battery is a Multistar 10.000 mah.


I took the quad to my house and it is still like the day of falling, so tomorrow I will try to analyse connector or burn cables. I think it could be useful and after analysing the log, we are ready to find the real problem. I won't forget to take pictures of damages :S

Thank you so much for all your support, I love this community!


Battery issues

check your battery, connectors and power distribution wiring.



An instantaneous spike of accZ down to -40 does not indicate freefall.


who claimed otherwise ?

AccZ = -40  = 4 x G, so 3 xG up in the sky.

How is going up vs. landing ?

Current = ZERO failsafe is clear in case of burnout, battery issue, as reported.

This is exactly the Mission Termination Command invoked by Mission Termination Unit.

At low altitude, drone can still be nicely grounded if ESC has motor braking set off.

What was seen on video is drone's free drift with all motors unpowered (disarmed).

How to save ESC PWM value to log file for every ESC to calculate RPM for every motor ?

I opt for All RPM technology QuadPilot to stop crashes and power down in midair.

Can Pixhawk support ESC with RPM sensor ?

Freefall resets AccZ to ZERO value.

It does sound like, it could be a hardware fault. Did you check the battery itself for any lose wire? Also did you do a voltage reading of the battery after the crash?

Furthermore, what ESCs are you using?

Warning: Pre-Arming Check is not Active (0=Off & 1=Fully On)

Warning: GPS Pre-Arm checks are disabled, while GPS Failsafe are Enabled.
Warning: GPS could be unstable while the GPS failsafe requires it to be stable.
Warning: Recommend having both Enabled! Refer to Issue 1487 for more information.
Warning: https://github.com/diydrones/ardupilot/issues/1487

Warning: One or more compass offset is not set correctly (-150 to +150 recommended).

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