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Compass Error, EXIT P-GPS Mode Mid flight, not saved in alert log

lenabanana

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Hoping someone can enlighten me...
Just got my (replacement) mavic back from DJI after having a number of gimbal issues with the last one.

I set it up, updated it, calibrated it (including the compass) and off we went.

At some point during the flight i got a compass error warning but it disappeared and is not in the logs.
Thinking I did not do the compass calibration properly, I landed it - popped in a new battery, moved to a more open location (with apx 10m of clearance on all sides) and calibrated the compass again with no issues. *I should also mention this is mavic #3 for me, all calibrated in the same spot (my yard) and never saw this error once on either of the last 2

Off we went again, this time with screen recorder on and I saw a blip of red but so fast I didn't even catch what it said. I landed again and checked my video - scrubbing through I can stop right on it and here was again the same warning. Again, the warning is not registered in the warnings log.

Anyone have any ideas what is happening and how/if I can resolve this before I contact DJI again and raise hell for sending me a defective replacement? Maybe I'm doing something silly. Would prefer to fix myself than have to send it in again.
 

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snitchonthis

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*sigh* i don't have any clue about that but i am also on mavic #3



mag interference killed both before! Sorry about your issue. :(
 

lenabanana

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Without seeing the logs it's impossible to figure out what happened.
Alright first attempt to post a log coming right up....

Edit: OK I think I got it?
Here is the 2nd time it happend I believe? DJI Flight Log Viewer - PhantomHelp.com

I believe this is the first flight it happened during but it doesn't even show it in the log, it was towards the end of the flight - I also had a motor speed maxout during this flight @5 min 10 seconds Not sure what that is happening there or why... mavic is reporting super low speed or even 0mp at times for almost a minute.
DJI Flight Log Viewer - PhantomHelp.com
 
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Dragonfly

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It's a possibility that you have a Mavic that has one of the rear motor wires that is not twisted. This was a known issue on early Mavics and at certain motor revs that caused a frequency from the motor along those 3 wires which are close to the rear compass just happened to cause interference to the compass.
It is a slight possibility that you may be experiencing somthing similar and your rear motor wires may need more twist in them or a least checked to see if they even are twisted. Just a thought.
 
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lenabanana

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It's a possibility that you have a Mavic that has one of the rear motor wires that is not twisted. This was a known issue on early Mavics and at certain motor revs that caused a frequency from the motor along those 3 wires which are close to the rear compass just happened to cause interference to the compass.
It is a slight possibility that you may be experiencing somthing similar and your rear motor wires may need more twist in them or a least checked to see if they even are twisted. Just a thought.
Serial number looks like a March 2018 build (08QCF) so seems unlikely...
 

sar104

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Excuse me Mr. Physicist, could you physicize my logs when you have a moment? I have posted them above. :D
Yes - that's the second segment of the flight. The compass error was recorded in the logs as a non-GPS error (CompassErrorLarge) starting at 699.1 s and lasting 1.5 s, shown by the black trace in the graph below. It occurs just before a significant yaw maneuver, but appears to have been triggered by a rapid pitch change (red trace) when you went from full forward elevator to centered sticks at 698 s (red dashed trace). You might want to see if that is a consistent behavior. If it is then I'd want to see the magnetometer data from the mobile device DAT file in order to see what is actually happening.

2018-06-28_[19-00-10]_01.png
 

lenabanana

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Yes - that's the second segment of the flight. The compass error was recorded in the logs as a non-GPS error (CompassErrorLarge) starting at 699.1 s and lasting 1.5 s, shown by the black trace in the graph below. It occurs just before a significant yaw maneuver, but appears to have been triggered by a rapid pitch change (red trace) when you went from full forward elevator to centered sticks at 698 s (red dashed trace). You might want to see if that is a consistent behavior. If it is then I'd want to see the magnetometer data from the mobile device DAT file in order to see what is actually happening.

View attachment 41048
I believe I let go of the sticks when I saw the warning pop up, does that make sense compared to what you see or no?
I think this is the corresponding dat file 2018-06-28 19_20_53-08RDEB7001046K.dat

Also, any thoughts on my speed warning from the other flight?
 

sar104

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I believe I let go of the sticks when I saw the warning pop up, does that make sense compared to what you see or no?
I think this is the corresponding dat file 2018-06-28 19_20_53-08RDEB7001046K.dat

Also, any thoughts on my speed warning from the other flight?
As you can see in the graph above, you released the sticks one second before the compass error was generated. I'll take a look at the other flight.

EDIT - I don't see that you have posted the other flight - have I missed something?
 

sar104

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lenabanana

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As you can see in the graph above, you released the sticks one second before the compass error was generated. I'll take a look at the other flight.

EDIT - I don't see that you have posted the other flight - have I missed something?
Ah yes I do see, thank you for your patience - it is my first time looking at something like this and I mistook the solid line for the RC input. Very odd, I don't know why I would have done that.

DAT file attempt #2 *sorry if this is the wrong one, the numbers & times on the DAT files dont match the logs*
2018-06-28_19-19-43_FLY010.DAT

And yes, there are two links in my comment with the original flight logs, for two different flights.
So this is the 13 min flight with the compass error DJI Flight Log Viewer - PhantomHelp.com

And THIS is a 6 minute flight that also had a compass error that is not showing in the log (I swear) and also had a speed warning (in the log)
DJI Flight Log Viewer - PhantomHelp.com
 
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sar104

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Ah yes I do see, thank you for your patience - it is my first time looking at something like this and I mistook the solid line for the RC input. Very odd, I don't know why I would have done that.

DAT file attempt #2 *sorry if this is the wrong one, the numbers & times on the DAT files dont match the logs*
2018-06-28_19-19-43_FLY010.DAT

And yes, there are two links in my comment with the original flight logs, for two different flights.
So this is the 13 min flight with the compass error DJI Flight Log Viewer - PhantomHelp.com

And THIS is a 6 minute flight that also had a compass error that is not showing in the log (I swear) and also had a speed warning (in the log)
DJI Flight Log Viewer - PhantomHelp.com
OK - the first flight that you linked in post #5 was the second segment of a flight, starting at 2300Z, with a brief compass error as shown in the graph above. The second flight log that you linked in that post was a later flight at 2320Z and is the same flight as the DAT file FLY010.DAT. That flight has GpsPositionNonMatch and SpeedErrorLarge errors.
 

lenabanana

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OK - the first flight that you linked in post #5 was the second segment of a flight, starting at 2300Z, with a brief compass error as shown in the graph above. The second flight log that you linked in that post was a later flight at 2320Z and is the same flight as the DAT file FLY010.DAT. That flight has GpsPositionNonMatch and SpeedErrorLarge errors.
Yes I noticed those also, the speed error is what I’m wondering about. I got an on screen warning that motor was at max speed.
 

sar104

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Yes I noticed those also, the speed error is what I’m wondering about. I got an on screen warning that motor was at max speed.
You were throwing it around pretty hard in sport mode. The speed error occurred on another sudden deceleration at 318 s that caused a fairly extreme pitch excursion. I don't think that these errors are any cause for concern.

2018-06-28_[19-20-51]_01.png

I don't see any motor speed errors in this flight. The motor speeds were reasonable:

2018-06-28_[19-20-51]_02.png
 
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lenabanana

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You were throwing it around pretty hard in sport mode. The speed error occurred on another sudden deceleration at 318 s that caused a fairly extreme pitch excursion. I don't think that these errors are any cause for concern.

View attachment 41052

I don't see any motor speed errors in this flight. The motor speeds were reasonable:

View attachment 41053
Actually that causes me even more concern because I’m 100% certain that when I got the motor max warning I had the stick forward and I let go only because of the error.
I had previous issues with gimbal twitches and resets in sport mode so I was trying to test this mavic to make sure I didn’t continue to have the issue.

I’m going to continue to test this but I’d bet my right arm on it that the speed warning came and THEN I let go of the stick because of the warning and not the other way around - I suspected this for the compass error as well, but wasn’t certain. As far as the speed warning goes I’m completely certain that I stopped as a result of the warning and that it said motor speed maximum on screen when it happened.

Might need to do this with a GoPro on my head next time so I can actually show what I see on screen compared to what I’m doing with the sticks because it really seems like it is registering the onscreen warning a second later than I am seeing it pop up.
 

sar104

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Actually that causes me even more concern because I’m 100% certain that when I got the motor max warning I had the stick forward and I let go only because of the error.
I had previous issues with gimbal twitches and resets in sport mode so I was trying to test this mavic to make sure I didn’t continue to have the issue.

I’m going to continue to test this but I’d bet my right arm on it that the speed warning came and THEN I let go of the stick because of the warning and not the other way around - I suspected this for the compass error as well, but wasn’t certain. As far as the speed warning goes I’m completely certain that I stopped as a result of the warning and that it said motor speed maximum on screen when it happened.

Might need to do this with a GoPro on my head next time so I can actually show what I see on screen compared to what I’m doing with the sticks because it really seems like it is registering the onscreen warning a second later than I am seeing it pop up.
I can't comment on the motor speed warning because neither of the flights that you posted logs for had one. If you can figure out which flight and post the log then I can take a look. Either way, with that kind of flying in sport mode, the occasional motor warning is not surprising and does not necessarily indicate a problem.
 

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Reading this I'm supposing there may be some confusion about "speed warnings".

The SPEED_LARGE_ERROR seen at 319 secs is issued by the FC and is basically saying that the AC predicted and measured speeds don't match. This gets presented in the Go App as a "compass error".

A motor speed warning is unrelated to a SPEED_LARGE_ERROR. Except that, in this case, seeing the motor max speed warning caused the pilot to abruptly remove full elevator which, in turn, caused the SPEED_LARGE_ERROR.

The FC control algorithms seem to be pretty robust. I don't actually know this since I've not had any experience with other drones besides DJI. But, it's always possible to drive the algorithms to the edge where they don't do so well. @lenabanana maybe you should become a DJI test pilot:)
 
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