Serious crash during QHOVER landing after mission

All went well for this mission until landing. We switched to QHOVER, transition took place and suddenly all multirotors stopped working. It was at 15 meter altitude and of course had a serious crash.

Strangly, after looking at the logfile, it looks like there was a total loss of power. However, nosecam video showed the plane going down and crashing. So the power was still there.

I need some help to find the root cause of the problem.

Logfile is here:

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Did you have the power module connect to the quad part too? Witch one? Wires and connectors are enought for transition big cosumption?

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We operate with 2 separate batteries. 1 big li-ion for forward flight and another lipo for multirotor. The forward flight battery also powers the equipment. The multirotor battary is only for powering the multirotor and doesn’t have a power module.


Dear Tridge, can you please help? I’m really lost here.

Log ends abruptly, no data from the crash, which indicates a total loss of power of the flight controller.
No indication of any error in the log, so this is the most likely cause.

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That was also my first opinion. But actually video kept on going. And that’s from the same power source. Very, very strange. Anyway, thanks for looking and your help.

Are you sure that video is powered from the same 5.3V that the power module creates?

You say that video was powering by forward flight batt and quad separate by lipo and fails quad power, that have sense. what lipo and consumption quad motors you had?

Hi Andras,

Our system is devided into 2 main systems:

  1. forward flight
  2. multi rotor flight

The forward flight system is a 30a/h 5S li-ion battery that also power all electronics.

The electronics are devided into 3 sections:

  1. flight critical
  2. mission critical
  3. non critical

The pixhawk gets his power from the power brick that goes from the battery to the forward flight motor AND from the servo rail. The servo rail gets power from a regulator connected directly to the battery. This would normally provide the redundancy for powering the pixhawk.

So in case of a battery failure, both the power from the power brick as well as the servo power would fail.

However, the nosecam video and video transmitter are also getting the power from the battery but through a different regulator (non critical equipment).

Since nosecam video kept on, this indicates it wasn’t a major battery failure as the video would also have stopped working.

In my opinion, a simultaneous failure of both the power brick as well as the servo rail power is very unlikely.

The servo power regulator is only supplying the pixhawk servo rail side. The servos get their power directly from yet another, dedicated regulator regulator (flight critical)

Since I took all precautions to make almost everything redundant and dividing it into the 3 sections, I have a hard time finding out what caused this crash.

I’m not monitoring the multirotor power system as the power requirements are very high and I go directly from battery to the esc’s from the multirotors. A power brick could not handle the maximum power requirements. These are over 120A peak.

It looks as if the pixhawk was somehow being reset, or got disarmt, or indeed had both power sources cut simultaneously.

I’m totally flabbergasted…

Thanks for that info. Very helpful. I seriously hope it was the quad battery. But that still doesn’t explain why the pixhawk stops…

Is it a Pixhawk or a Cube ?

Cube. Original, no copy.

Cube does not got power from the servo rail. So there were no backup power only one source.

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Please have a look here:

It says:

"Voltage Ratings

Pixhawk can be triple-redundant on the power supply if three power sources are supplied. The three rails are: Power module input, servo rail input, USB input."

So I think I was redundant

That description is definitely wrong (copied from the description of PixHawk 1)

The definitive guide is this :

" FMU and peripherals will NO LONGERaccept power from the servo connector"

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Well, that explains. Thanks a million.

Conflicting information all over the place. And that is information for the Cube.

Me thinking I’m redundant, on the contrary… a small dip in the power brick and a few thousand dollars are gone.

Well, you live and you learn. Makes me a bit sad though.

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I have created a warning on “Hardware” to warn others from expecting the same.