Tumbling and crash - strange log

ArduCopter Copter 3.6
1

Hi,
Today I flew with my Pixhawk copter running V3.6.7, first everything was good, but then It started sounding a bit weird, but not too bad, so I flew about 50 meters away, and suddenly it began to tumble and the crash. luckily almost nothing got damaged, but i am trying to find the cause of the crash.

In the log, one can see that suddenly the des roll/roll seem to be mirrored… But I dont think I understand this, also, strangely des Pirch/pitch remain fairly ok.

any Ideas on this?

https://drive.google.com/file/d/11xzM4tMRhxQopBM4ebOGehVg36duxIS0/view?usp=sharing

2

Any chance you can supply the .bin log?

3

sure! :slight_smile:

https://drive.google.com/open?id=1DK-ChtezglTkzKLsLiQ1uaezsP2hkLgF

4

OK, figured it out.
one of the ESC signal wires broke and sometimes made contact, sometimes not.
damn, what type of cable should I use to avoid them breaking?

6

It’s good that you worked out what went wrong.
You can see in logs where opposing motors were commanded to maximum and minimum respectively to try and compensate for loss of thrust.
There’s actually quite a few places where different motors are commanded to minimum and maximum to try and maintain stability. And there’s a few places where Desired pitch departs quite a bit from actual pitch.
There’s lots of wild fluctuations occurring too, like the flight controller is really struggling to get the ESCs and motors to do what it wants. I’d say the motor/prop/ESC combination is struggling in some regard, and the craft is probably not well balanced. Or maybe it was just very windy ?

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This plot is from a good steady part of the flight, not even the crash zone! It could be the broken wires causing this.

Once all those wires are checked and fixed you might want to do a nice steady flight, some hovering, some straight level flight, and some smooth altitude changes and then go over the logs again.
Let us know specific details of you build if you want to.

7

Hi,
Thanks for the detailed analysis.
I think that the wire was loose from the beginning, and thats what caused the erratic behaviour. Because my quad should be fairly well balanced. But I will do another flight and post the logs. I just cant decide if I put in all new wires (different ones) or if I just resolder that esc.

Quad data:
T-Motot U3-700
Cf prop 13x4
Tarot Iron man @2.2KG AUW