Crash after Autotune: could someone please take a look at the logfile?

ArduCopter Copter 3.5
1

Hello,
I have a guess, but would like to have a second opinion, maybe someone can help me. After 3 successful autotune flights (one for each axis) I wanted to test the new parameters with a new battery and did some pitch and roll maneuvers. As you can see in the last seconds of the attached video, i rolled to the left and slowed down roll to the right, in this moment the cube losed control and just fell off (only minor damage)
One thing I noticed after auto tune: roll was too sensitive on take off there where vibrations in the ground effect, but disappeared from 1.50m height. Another thing was that while waiting for IMU temperature the safety button changed its status to “safe”. Could this also happened in flight?
I replayed also TLog and one thing I’m suspicious of is the message (SAFE) in the HUD a few seconds before the crash …
Thank you very much for your attention!

FW is Copter 3.5.5, ESCs and Motors are DJI E1200, 2x 10.000 mah 6S batteries.

Logfile:

Video:

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2

Roll and Pitch are very good compared to Des_Roll and Des_Pitch so It looks to me that you had a hardware failure, probably the Esc so nothing related to Autotune.

3

In flight failure of motor4. See at the end of the log. Rcout4 max out, and RCout3 goes down, trying to compensate, but no changes in attitude.
Also no change in current when motor4 maxing out, so it was definitely stopped.

4

Question is why did the other motors not spool up for motor redundancy ?

Have been trying to get the motor redundancy to work on a hex with no success.
Would appreciate any feedback on this.

Video of Hexa redundancy testing with power shutoff to M5 motor while in hover.
Also resulted in a crash.

Arducopter Hexacopter Motor Redundancy test

5

Hmm… I agree with you, ESC 4 and motor are still working, better change it with a new one? Or reduce angel max to 40

6

I think the main rule that your hex must be able to stay in the air with 4 motors, till the flight controller start to compensate.
If you think about it, if one motor fails, then the motor at the opposite side must reduce throttle significantly.

There are lot’s of videos about hexas with AC handling motor failure very well, like this. : https://www.youtube.com/watch?v=FNQgdcImpKs

7

Defnitely replace. If it once failed there is no warranty that it will not do that again. However it can be ESC, power dstribution, bad soldering, and even a bad motor… :frowning:

8

Lose bullet connector is also a popular point of failure…

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9

Rule 237: Do not use bullet connectors, SOLDER. :smiley:

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10

The attitude can be maintained with one motor stopped if some conditions are present and you have some luck.

The copter must have a levelled attitude , in Jochen’s case it was not .

In the video you link , the copter seems quite unbalanced, motors 1,3,6 are at 44% while the others are at 58% , the battery is depleted , it went from 23,17 volts to 20,70 volts in just 15 seconds.

I suspect that , as a rule of thumb, to maintain copter attitude when a motor stops the copter should have enough power to hover with just 4 motors

I was able to recover my Hexa with one motor stopped because of a defective Esc while flying at 100 meters in 8 m/s wind.

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