Heavy Drone crash cause analysis


I will need your help. I’ve new heavy custom-made drone. I did two test flights with it, it seemed to work fine, but on the thrid flight, it crashed. It crashed very unexpectedly. I were flying in the Loiter mode, and while there was no input from my side, it started changed yaw alone then he’s became difficult to maintain levelled and finallly crashed on a wall. In my opinion, it looks like ESC failure.

The firmware used is v4.0.3.

Copter type is Hexa+ frame
T-Motor MN6007 160Kv + T-Motor ESC Flame 60A HV 600Hz
Carbon prop 22x6.6
Battery 12S
weight : 8 Kg
Home Made Autopilote (FmuV5)

Logs file :

Can you help me to find the problem ?


That has to be the most annoying cloud storage service I have yet seen…

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Around the time you lose roll authority you have motors that are going to minimum output to try and maintain stability. Could have been wind that triggered the instability, but you were always “on the edge”.
Here’s a key indicator:
They’re almost the same. You’ll need to add weight to bring up that hover value, and see if you can lower the MOT_SPIN_MIN a little.

I think you need to re-evaluate your tune, some of the PIDs dont seem correct to me, especially yaw. P and I terms are usually the same for Roll and Pitch.
You’d need to go over the tuning guide again:
And use this helper spreadsheet:

Some of your params definitely need fixing:

And with those ESC’s you need:
and probably a lower MOT_THST_EXPO than normal (more linear, like 0.2)

After you fix all that other stuff, try these PIDs as a starting point, they’re probably safe and will need further tuning and Autotune.
ATC_INPUT_TC,0.2 <- adjust to suit your RC Feel preference

Hi Shawn,
Based on the “Initial parameter calculator” for 22" props. the Parameter MOT_THST_EXPO is 0.76, while I normally use for my quadcopter similar to this is about 0.72 . However in this posting you suggest to be 0.2 which is much lower than normal . Could you please clarify about this issue?
Thank you

The ESCs you have, T-Motor Flame 60A HV 600Hz, “linearize” the thrust, which normal ESCs dont do.
Once you’ve got everything else ready for testing, try a mid range value like 0.5 and test lower values from there. Let us know what you come up with.
According to the consensus on those Flame ESCs you’d expect to use somewhere from 0.0 to 0.3

There’s some good info in this discussion:

EDIT: And once you’ve tested, tuned and autotuned with the minimum flyable weight, I assume you’ll want to add some real payload further increasing the take off weight. When you do, adjust these parameters as follows (from the Tuning guide):

Many thanks for your analysis. This is very interesting to know and you have probably save my UAV for the next test. I’ll repair the drone, apply yours modifications and i’ll back to you.