This has allso been posted on facebook in the "DJI S1000 Owners" group.
https://www.facebook.com/groups/DJIs1000/permalink/1750400455194692/


Link to MKII log file [FLY039.DAT] 35.776KB
https://www.dropbox.com/sh/vbww8qsf1li8642/AAAHl7dAf3MCq8TQu9114W-ea?dl=0


Flew 2 good hours last night with our S1000+/A2/FLIR setup. After initializing flightroute from GS software, the UAV changed direction, got back on track, turned around itself and continued. A couple seconds after it happend again. I took control in GPS mode. I didnt have 100% control, better response to pitch/roll to one side, and sluggish to the other side. Went to Atti mode and landed, and before it touched ground i could see the LED under M6 was off, and the motor was spinning slow and random.
After landing and a visual and nose (smell) inspection, we tried to arm again, and M6 did not spin up correct. After 2-3 tries, it came alive, and the LED was back in action. Arming it 5 times, all was well. We did not fly again all though the job was not done, but went home to the office and are about the review log data and do a more thorough visual inspection.
No loose connections, no visual dmg, logs are yet to be reviewed.
Any thoughts on what might cause this?
We are ordering a new arm, but would like to pinpoint the cause of the problem before we fly again with this setup over water.


##Update##

A bit more details….

  

Firstly, I do not mind replacing the entire M6 arm, but I would like to know the cause of the failure, since from my perspective the cause can originate from several sources. It would be useless to replace the arm if the cause came from somewhere else.

  

As I see it, the following could be the source (in order of what I consider most likely):

  

1)      Something in the M6 arm itself (wiring/connectors, ESC, motor)

  

2)      General system wiring

  

3)      Power related issue

  

4)      A2 fault

  

5)      Short circuit/noise or similar induced from gimbal payload system

  

What I would like input in regards to (besides concrete suggestions to causes) is what can be excluded from the list above.

  

The first clues: The M6 engine failed in flight, came back in operation, failed again. When landing I noticed the LED for M6 was out and that the engine was spinning slowly and irregular. Could this behavior exclude anything/favor something specific as the cause?

  

I have gone through the logs but have not been able to conclude anything specific (it would have been nice of DJI to include an actual error log…. Oh well…):

  First, I checked the flight modes:

#1

It started navigation mode at time=146 and stayed in this mode until time=235.

  

Next, I looked at the M6 motor out:

#2

Above, it can clearly be seen that the motor out has spikes to max. The First spike correlates with the first observed spin in the air, then it came back, and later it went out again.

  

Looking at the close-up of the first spike it seems to start at around time=160.8 (before 161, in any case):

#3

I have also looked at the other motors, but have not included graphs here. In general, they show what one would expect. The adjacent motors increase output and the opposite motor decreases output (probably to compensate for M6 being out). Then there is also indication of some motors doing something to compensate for yaw spin.

Finally, and this is peculiar, I looked at the main voltage and BEC voltage:

#4

It clearly shows a drop in voltage at the same time as the observed behavior. Seen in close up here:

#5

It seems that the main voltage drop started at time = 162. This seems to indicate that the main voltage power drop was not the cause, but rather a side effect of the M6 motor being out. Can anyone confirm or explain this?

Then the BEC voltage:

#6

There is a very small power drop. Seen here in close up:

#7

The small BEC power drop also appears at time = 162.

It is worth to note, that the power drops only appears the first time the M6 motor went out. It does not show at the later times the M6 motor went out.

Does the above mean that one can exclude the following:

2)      General system wiring

3)      Power related issue

4)      A2 fault

5)      Short circuit/noise or similar induced from gimbal payload system

And therefore conclude that the problem is with:

1)      Something in the M6 arm itself (wiring/connectors, ESC, motor)

Or, would that be too hasty a conclusion?

Any feedback/thoughts/experience with similar issues will be much appreciated.

Thanks.

##UPDATE##

Video showing yaw behavior and time between fails here

https://vimeo.com/159689604

have you tried to spin the prop by hand to check if there is any resistance?  also try to check if there are any grinding noise.   Maybe dust or dirt could be causing the motor to not spin properly?