Analyze my mystery crash log

[lenn]

OK - that shows no indication at all of any power supply problem. The motor voltage is flat right up until the log stops. In cases where a battery disconnect occurs then the voltage record sags over 70 ms or so until it falls below the threshold for FC operation.

That strongly suggests that the cause was FC processor failure or, in other words, the FC froze/crashed and that simply shut down the aircraft.

Thank you for the thoughtful insight sar104. Your description of a voltage sag would make sense with a bad or failing battery, but would a voltage sag show in the event of a physical battery disconnect? I have very limited experience here, but saw the same - that battery and motor speed/current were within range of normal flight.

I appreciate the analysis here. In reading other posts, DJI responses are short and don't usually get down to root cause. They are a business seeing thousands of these MPs and a repair shop after all...

EDIT: @sar104 I found the lengthy discussion and components of the answer to my inquiry. Thanks. Search is my friend. If your Mavic falls out of the sky...

 

[sar104]

Thank you for the thoughtful insight sar104. Your description of a voltage sag would make sense with a bad or failing battery, but would a voltage sag show in the event of a physical battery disconnect? I have very limited experience here, but saw the same - that battery and motor speed/current were within range of normal flight.

I appreciate the analysis here. In reading other posts, DJI responses are short and don't usually get down to root cause. They are a business seeing thousands of these MPs and a repair shop after all...

EDIT: @sar104 I found the lengthy discussion and components of the answer to my inquiry. Thanks. Search is my friend. If your Mavic falls out of the sky...

That thread was potentially confusing but yes - the inductance of the system is sufficient to slow the voltage drop enough for it to be visible at the full log recording rate.

 

[lenn]

That thread was potentially confusing but yes - the inductance of the system is sufficient to slow the voltage drop enough for it to be visible at the full log recording rate.

@sar104 , mind me asking what software you are using to analyze my DAT file? I'm interested in comparing with other "fell out of the sky" logs and found the decided CSV output rather cumbersome too. Thanks!

 

[sar104]

@sar104 , mind me asking what software you are using to analyze my DAT file? I'm interested in comparing with other "fell out of the sky" logs and found the decided CSV output rather cumbersome too. Thanks!

I import the CSV data into a data analysis software package (Wavemetrics Igor Pro) and do the manipulation, analysis and visualization there.

 

[lenn]

Thanks you all for the support and analysis. I just heard back from DJI that this repair will be covered under warranty. For those who are wondering about processing time (it was killing me to find out):

9/14/2018: Malfunction and crash. I opened the case and shipped it to DJI on the same day from NY to TX.
9/19/2018: It was delivered by UPS.
9/20/2018: DJI officially unboxed, took inventory and marked it as received and began the assessment on the same day. I inform them that I had included a 64GB MicroSD card and the original retail box which was not marked on their inventory. They respond within hours with pictures saying they will take care of it
9/21/2018: DJI informs me via email that this is covered under warranty. Total damage quote is $696USD. I do not have DJI Care.

No ETA on shipment of the new unit. No idea if they will include original box or my original 64GB microSD. Very happy with the service so far as long as they make me whole with the repaired or replacement unit.

 

[CarlsbadAL]

Hello Everyone, Interesting thread.! Did anyone notice the huge bird flying over the building at about 36 seconds ? Plenty of time to climb up and attack from above. Might have been a bird strike. Looks like a great place to build a nest.
AL

 

[sar104]

Hello Everyone, Interesting thread.! Did anyone notice the huge bird flying over the building at about 36 seconds ? Plenty of time to climb up and attack from above. Might have been a bird strike. Looks like a great place to build a nest.
AL

That would have been recorded in the log.

 

[CarlsbadAL]

So Bird strikes are captured in the flight logs ? Direct hit from above that dislodged the battery isn't a possibility? Those big birds have big claws !!
I'm not trying to stir the bucket here, just another opinion.
Sar105 your analysis of the logs posted on this forum are awesome !!!
Thank you!
AL

 

[Simmo]

There is a bird strike sensor.... nahh!!
With a bird strike, the Air frame would be subjected to outside forces, causing the FC to input very different signals to the ESC's.
Flight parameters (yaw, pitch etc) would change perhaps dramatically, with no corresponding inputs on the RC sticks

 

[BudWalker]

So Bird strikes are captured in the flight logs ? Direct hit from above that dislodged the battery isn't a possibility? Those big birds have big claws !!
I'm not trying to stir the bucket here, just another opinion.
Sar105 your analysis of the logs posted on this forum are awesome !!!
Thank you!
AL

A bird strike, or any impact, would be apparent in the accelerometer and gyro data. In this incident these data do not indicate an impact.

FWIW, I've looked at several incidents over the past two years and have only seen one where a bird strike was a possibility. Take a look here
Lost Mavic Pro - gps position no match + speed error

 

[lenn]

That would have been recorded in the log.

A bird strike, or any impact, would be apparent in the accelerometer and gyro data. In this incident these data do not indicate an impact.

FWIW, I've looked at several incidents over the past two years and have only seen one where a bird strike was a possibility. Take a look here
Lost Mavic Pro - gps position no match + speed error

Yep, that was what I would expect as well. Also - I would've expected a jolt to show up on the video, and maybe even some of the video to show the MP falling too. I'd imagine a bird strike knocking out the battery on the first shot to be relatively unlikely.

 

[Turn11]

FC

?? FC = flight controller ??

 

[sar104]

?? FC = flight controller ??

Yes.

 

[lenn]

Wanted to close the loop on this one. Just received the replacement in the original box and my original SD card. Extremely happy with the service and turn around. Most of the time was spent on shipping (UPS ground).

I think I received reasonable service only because I was able to retrieve the carcass and the data was readable. I've seen similar posts from less lucky folks who's MP's dropped into water. Surprised this was still happening in a 3 year old product that regularly receives firmware updates.

Feeling less confident about flying this over water these days. Never had that feeling with the 3DR Solo.....