Data interpretation please

[kdalemathew]

Hello,
My Mavic Pro 2 showed some instability on the screen as I was flying, something I've never seen before, and then dropped from the sky while trying to bring it home. As it was falling, I brought both sticks in and down for no real reason other than panic; I think my brain was clutching at the word "emergency" in "emergency stop".
Can someone tell me what may have happened?
Thank you.

 

[dirkclod]

Welcome to the forum .Though I don’t attempt to read logs
we have many that do. @Meta4 and @sar104 come to
my mind first off. There are others and sure someone will
get to you shortly.

 

[Meta4]

Hello,
My Mavic Pro 2 showed some instability on the screen as I was flying, something I've never seen before, and then dropped from the sky while trying to bring it home. As it was falling, I brought both sticks in and down for no real reason other than panic; I think my brain was clutching at the word "emergency" in "emergency stop".
Can someone tell me what may have happened?

Here's what the recorded flight data looks like: DJI Flight Log Viewer - PhantomHelp.com
Towards the end of that flight, there are a number of error messages that indicate problems with the drone.
Particularly this one: Satellite Positioning Off. Fly with caution; IMU attitude error. Please restart the aircraft.; Other (8)
Using the CSC joystick position after the drone had shut down in the air made no difference.
This one looks like a good case to refer to DJI tech support for a warranty claim.

Synch your flight record (click the cloud icon on the flight records page in the app) to upload the record to DJI.
Then go to their support webpage and open an online chat to get things started.

 

[kdalemathew]

Here's what the recorded flight data looks like: DJI Flight Log Viewer - PhantomHelp.com
Towards the end of that flight, there are a number of error messages that indicate problems with the drone.
Particularly this one: Satellite Positioning Off. Fly with caution; IMU attitude error. Please restart the aircraft.; Other (8)
Using the CSC joystick position after the drone had shut down in the air made no difference.
This one looks like a good case to refer to DJI tech support for a warranty claim.

Synch your flight record (click the cloud icon on the flight records page in the app) to upload the record to DJI.
Then go to their support webpage and open an online chat to get things started.

Thanks for the quick response. I'll check in with DJI and see what happens.

 

[sar104]

The IMU and GPS errors were symptoms that happened after the aircraft control failed, not the cause. This looks to me like a failed motor or lost prop - probably rear right. The pitch, roll and yaw signature is pretty clear.



I'd need to see the mobile device DAT file, which contains the detailed IMU and motor data, to distinguish between those possibilities.

You did execute a CSC as the aircraft was falling, but even if you have that option enabled in the settings (which it is not by default) you didn't hold it for long enough to stop the motors.

 

[sar104]

I should have added the link to the instructions to retrieve the DAT file, which will be FLY023.DAT:

Mobile device DAT file: How to retrieve a V3.DAT from the tablet

 

[kdalemathew]

Thanks for your input!
I believe this is the correct DAT. If you could zero in on a cause, I'd at least have an answer. That you can "see" so much in these zeros and ones just amazes me.
Thanks again.

 

[sar104]

Thanks for your input!
I believe this is the correct DAT. If you could zero in on a cause, I'd at least have an answer. That you can "see" so much in these zeros and ones just amazes me.
Thanks again.

No - that's FLY024.DAT. As I mentioned above, we need FLY023.DAT.

 

[kdalemathew]

No - that's FLY024.DAT. As I mentioned above, we need FLY023.DAT.

Ok, thank you for your efforts and input!

 

[sar104]

The data are unusual - it looks like a problem with the rear right motor rather than a simple lost prop, but I haven't seen motor data like that before.



I don't think 16,000 rpm is physically possible if the prop is attached, but the oscillations also look unphysical. The event stream doesn't comment on the propulsion system until quite late into the event:

149.321 : 11141 [L-FDI]propulsion Spd-Cur fault:1

Have you contacted DJI about this? It looks like a clear warranty issue to me.

 

[kdalemathew]

Hey sar104, thanks so much for reviewing the data. I really appreciate it. I'll be starting the process with DJI shortly. And thanks to Meta4 as well for the input and advice. I'll be back in the air ASAP.

 

[kdalemathew]

Very pleased to report that DJI is covering my AC under warranty. No answer as to what happened from DJI, but I’m not going to push the issue. I appreciate the help you all have given me.

 

[sar104]

Very pleased to report that DJI is covering my AC under warranty. No answer as to what happened from DJI, but I’m not going to push the issue. I appreciate the help you all have given me.

Good - another appropriate result from DJI. Did you prime them with any of the previous analyses or was that a completely independent determination?

 

[kdalemathew]

Good - another appropriate result from DJI. Did you prime them with any of the previous analyses or was that a completely independent determination?

No, it was their own call. I uploaded the data in the app, and they took it from there.
“...appropriate result...” fits quite nicely. Glad to be able to report good customer service.