Need help diagnosing a possible mid-air pixhawk reboot


My quad, with a version of Copter 3.4.5 on its Pixhawk, crashed while flying in LOITER mode. The logs show that the logging stopped mid-air without any apparent errors or erroneous data. I suspected a faulty power module or harness that cut off power but the components turned out to be functioning fine upon testing. Even the Pixhawk is powering up and sending data properly and is even logging data. I’ve run out of ideas about what else could have gone wrong so if anyone has any other ideas, it would be very helpful.

Link to the log:

How many flight hours does your system already have?
Have you ever measured the 5V supply of the power board, which may be weak?
What additional omponents did you connect with being powered by the PixHawk instead of a separated UBEC?

Around 40 hrs, or maybe slightly higher.
Yeah, I tested the power supply. It seemed pretty consistent at around 4.9-5V.
Only the two GPS modules are being powered by the Pixhawk directly.

Then I would think next about a loose connection, either within the power connectors of power board and Pixhawk or within the connection cable itself. These thin wires and sensitive mini connectors can easily break on vibration or other mechanical stress…

I had suspected something on those lines as well. But the wires and connectors are still functioning fine and I didn’t find any loose connection that would lead to a power recycle. Also, everything was connected after the crash as well. The UAV had power as the LEDs were functioning.

If one of these thin wires will break you may not see this as the cable is still held together by its coating. In worst case the two ends of a broken wire will make contact most time and just randomly disconnect for short time. I have seen this just few days ago with one of my gimbal cables. For PixHawk, GND and VCC lines between power board and PixHawk are doubled. Even if one wire will brake there is still contact but with increased resistance, so the voltage for PixHawk may drop down too much if more current is drawn. Just use a multimeter and check each of these four wires for discontinuity when applying a small amout of pull force to it.

Well I tested the wires like you mentioned but the cables seem to be fine. There is no discontinuity between the ends of the wires even when pulled on a little. Could a similar break in one of the other signal lines cause such a reboot? I doubt it though.

Then I have no further idea. The other two wires within that cable are just for monitoring voltage and amps…