[CRASH] Hexacopter suddenly crashed while auto

ArduCopter Copter 4.1
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1

Hello everyone !

My Tarot 680 Pro equiped with Pixhawk 4.1.15 suddenly crashed while reaching a waypoint in AUTO mode.
The copter was loitering very good, extremly stable after installing an anti-vibration plate on the Pixhawk.
So I tried an auto mode mission, and in the middle of the mission, it suddenly started to do weird things in mid air while having no control.
I immediatly switched to AltHold mode, retracted the landing gear, and started an emergency manoeuver but my throttle was the only thing the copter wanted to respond to.

I suspect the GPS to fall of its mast, but the copter fell upside down so maybe it’s something else.

I tried to check the GPS values but nothing crazy, I just see the IMU going crazy, no error at that moment.

I managed to almost gently land the copter but it was not really controllable.

Here is the .bin file :

https://www.dropbox.com/s/dunql28hfaatnw6/crash.BIN?dl=1

There is no physical problem everything is in place exept GPS (pretty normal after falling on it …)

Also, the auto analysis mentioned that there is a high change in mag field but the GPS is litteraly 17 cm away from the board, mounted on a carbon mast …

[quote=“HugoPx, post:1, topic:83521, full:true”]
Hello everyone !

My Tarot 680 Pro equiped with Pixhawk 4.1.15 suddenly crashed while reaching a waypoint in AUTO mode.
The copter was loitering very good, extremly stable after installing a vibration plate on the Pixhawk.
So I tried an auto mode mission, and in the middle of the mission, it suddenly started to do weird things in mid air while having no control.
I immediatly switched to AltHold mode, retracted the landing gear, and started an emergency manoeuver but my throttle was the only thing the copter wanted to respond to.

I suspect the GPS to fall of its mast, but the copter fell upside down so maybe it’s something else.

I tried to check the GPS values but nothing crazy, I just see the IMU going crazy, no error at that moment.

I managed to almost gently land the copter but it was not really controllable.

Here is the .bin file :

https://www.dropbox.com/s/dunql28hfaatnw6/crash.BIN?dl=1

There is no physical problem everything is in place exept GPS (pretty normal after falling on it …)

Compass = FAIL - Large change in mag_field (217.28%)
Max mag field length (1205.16) > recommended (550.00)

Regards
Hugo

1 Like
2

I’m not sure what caused the initial event but it’s certainly evident. But at a point after you switched to AltHold it lost thrust on Motor 3. Motor 4 dropped to minimum trying to compensate stability and down it goes.

RCout
RCout3348Ă—1026 307 KB

BTW-Log Auto Analysis is very limited in it’s usefulness not being up to date.

3

@dkemxr Hey dave, thanks for your reply !
What can cause AltHold thinking that cutting all thrust from a motor can be a good idea ?
Btw this make me realise that if I switched to Loiter instead of AltHold I I could have a successfull emergency landing -_-

Also, how can you get that level of zoom without having the curves out of the screen ?

Thanks,

4

It cut commanded output to Motor 4 due to lack of thrust on Motor 3.

Maybe but there was still a lack of thrust with essentially 2 motors not contributing.

Just apply a window. Left click and drag a box.