Unexplained crash

I really am in trouble because, according to the log and all I could see on the field, I can’t explain why this drone crash…

Do you have an idea of what is the problem there ?

link : Dropbox - log_66_2023-5-22-17-21-36.bin - Simplify your life


Failure of motor/ESC #4.

How could you be sure of that ? On the same field I had an other fail with an other drone

Log here : Dropbox - log_9_2023-5-23-19-23-44.bin - Simplify your life

#4 motor goes to maximum. The opposite motor (same direction) #3 goes to minimum to compensate. Pretty normal signature.

The other hint is in the messages:

2023-05-22 09:14:35.757 Error: Subsys THRUST_LOSS_CHECK ECode 1
2023-05-22 09:14:35.757 Potential Thrust Loss (4)

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Could we explain why ? Because motors are design to support more than 1500g each and the drone weight is only 1800g total…
Maybe wind ?

Moreover, other crash seems to be different, do you have an idea of the problem ?

What motors, props and ESCs are they?

In @Allister s graph it looks like desyncs, because Motor 4 recovers, but Motor3 loses sync, then later Motor3 again and Motor 2.

I looked at log_9_2023-5-23-19-23-44.bin
Battery voltage is starting to drop around the time of that incident, approaching the low voltage level for a 6S Lipo, and you dont have the correct voltage levels set or failsafe actions.

And it looks like definitely Motor3 gave you the big trouble. So similar issues to the other log that Allister looked at.

Motor outputs have a small oscillation in them, and attitude control also has small oscillations.
There is all default parameters for tuning, so incorrect PIDs and lack of tuning could be causing the ESCs to overheat and lose sync.

You need to connect to MissionPlanner Initial Parameters and put in your prop size, battery cell count, select “Suggested settings” and press Calculate → accept everything it offers.
It is a mistake to think you dont need some of these “just while we are testing”

Then set these:

INS_HNTCH_ENABLE,1  // set this then refresh params to see the rest

But don’t rush out to the field to try all these new settings yet!

A big problem is vibrations.
You need Y axis and Z axis down below 20 at least, preferably below 15.
Something is touching or pulling on the flight controller to make the Y axis vibrations worse than X axis, or the antivibration system is not equal in all directions.
Z axis vibrations can take a bit of work to fix - it could be prop wash over the flight controller, frame or parts vibrating and resonating, just poor antivibration mounting - there is a range of possibilities.

Once you are sure vibrations will be improved → then head out for another test flight.
Show us that log and we will move on to next steps.