Challenge: root-cause ID of crash

Hi all,

Can you please help me ID the casue of the crash?
It is an S500 X quad frame with Pixhawk and AC 3.3.3.
I have seen a few logs but this one beats me.
188.BIN (1.9 MB)
Flying in alt hold mode with no input from RC (mode2),no wind, nothing.
It drops RCOU4 and yanks up RCOU3.
Please help me identify why it did that!

Many thanks in advance!

It looks to me like loss of thrust from motor/esc #3. (front left) It appears that pitch and roll go negative, which I believe is nose and left side down. That matches with loss of thrust at front left (ch3). The controller would saturate that signal and minimize the opposite ch4 to attempt to stabilize.

I see you had just yawed from about 130deg to 80deg, then got the rollover. That yaw seems mild and not a cause of this. Sorry, I’d start by looking at all the ch3 components.

It’s possible others will have a different interpretation.

This pixhawk crashed an FX-79 several times, an X8 copter and this S 500 copter. After all these crashes my gut is telling me that the pixhawk has a problem, I just can`t pinpoint the source. The X8 is flying with another pixhawk ever since.

From the VIBE logs , it looks at the time of crash there was sudden vibration which causes the Quad to flip over :disappointed:

Thanks Robert, I had prblems with this board earlier.
It was sitting on the table and it just went from horizontal to 45deg roll in a split second then slowly came back to level.
I should have not put this board onto the copter or should have removed it when I saw do the same thing earlyer. at higher altitudes it was able to recover.
This time it was too low so it crashed.

Anyway, many Thanks!

Be careful with mild yaw Pids .
If your Yaw pid is weak you can have sudden yaw command from the board that will rotate your copter.

If you have big props and low kv motors , sudden large yaw command can lead to a crash since two motors are almost stopped and then cannot gain rpm again fast enough to maintain attitude.