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Friends Mavic crashed into a tree

slowjohnny

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A buddy of mine new to the Mavic world had his go crazy the other day and crashed into a tree. Flight was about 2 minutes long and he was hovering a few hundred feet away when he got a compass error then it took off and he had no control over it at all. I "think" I've figured out the .dat file export and setting up a public drop box. He is looking for some help in determining what went wrong before sending it back to DJI (he does not have DJI care but it is only a few weeks old).

Thanks folks... :)

Third attempt at getting the right .dat file! Thanks for your patience.
Dropbox - DJI_ASSISTANT_EXPORT_FILE_2017-09-30_12-52-29.DAT

Dropbox - DJI_ASSISTANT_EXPORT_FILE_2017-09-30_12-54-56.DAT
 
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A buddy of mine new to the Mavic world had his go crazy the other day and crashed into a tree. Flight was about 2 minutes long and he was hovering a few hundred feet away when he got a compass error then it took off and he had no control over it at all. I "think" I've figured out the .dat file export and setting up a public drop box. He is looking for some help in determining what went wrong before sending it back to DJI (he does not have DJI care but it is only a few weeks old).

Thanks folks... :)


Dropbox - DJI_ASSISTANT_EXPORT_FILE_2017-09-29_16-20-27.DAT


Sorry to hear it!! What kind of place did he take off from? Anything metal by chance?
 
Wide open field, at our R/C field, we fly everything there for many, many years. He was a few hundred feet from power lines and a barbed wire fence but they typically haven't been a problem.
 
A buddy of mine new to the Mavic world had his go crazy the other day and crashed into a tree. Flight was about 2 minutes long and he was hovering a few hundred feet away when he got a compass error then it took off and he had no control over it at all. I "think" I've figured out the .dat file export and setting up a public drop box. He is looking for some help in determining what went wrong before sending it back to DJI (he does not have DJI care but it is only a few weeks old).

Thanks folks... :)


Dropbox - DJI_ASSISTANT_EXPORT_FILE_2017-09-29_16-20-27.DAT
I am sorry to hear of your friends experience. I am sure someone will be along to analyze the issue.
 
A buddy of mine new to the Mavic world had his go crazy the other day and crashed into a tree. Flight was about 2 minutes long and he was hovering a few hundred feet away when he got a compass error then it took off and he had no control over it at all. I "think" I've figured out the .dat file export and setting up a public drop box. He is looking for some help in determining what went wrong before sending it back to DJI (he does not have DJI care but it is only a few weeks old).

Thanks folks... :)


Dropbox - DJI_ASSISTANT_EXPORT_FILE_2017-09-29_16-20-27.DAT

That's the wrong DAT file - it's not an actual flight.
 
That's the wrong DAT file - it's not an actual flight.
Good to know, how can I find the right file, there are literately dozens here... :) I'll try another shortly...

OK, replaced link in the first message. I hope that is the right file...
 
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Good to know, how can I find the right file, there are literately dozens here... :) I'll try another shortly...

OK, replaced link in the first message. I hope that is the right file...
Here is the flight that was posted. Maybe this can help you find the right one.
upload_2017-9-30_5-57-38.png

BTW, you can include more than one flight when you direct DJI Assistant to extract. We'll just look through them to find the right one.
 
OK, thanks all. I've updated the links again with the 2 records that were near the time he gave me, hopefully one of these will be the right flight. If you look at the flight above, the flight in question basically went from "H" to "A" where it went crazy then basically flew north and crashed into a tree.

Thanks again!
 
OK, thanks all. I've updated the links again with the 2 records that were near the time he gave me, hopefully one of these will be the right flight. If you look at the flight above, the flight in question basically went from "H" to "A" where it went crazy then basically flew north and crashed into a tree.

Thanks again!

FLY013 was the one. It was pretty much as you described, but with a couple of significant differences. The first graph shows the cause of the problem, I think - a very large compass error around 80 seconds as illustrated by the sudden divergence of yaw vs. magyaw. Both compasses reported bad data at 85 seconds.

85.492 : 395039785 : 4132 [L-FDI][FDI][COMPASS(0)] is outlier(fault)
85.492 : 395039950 : 4132 [L-FDI][FDI][COMPASS(1)] is outlier(fault)
87.074 : 402161265 : 4211 [L-FMU/LED]action changed. compass out of range:(0)
88.475 : 408463710 : 4281 [L-FDI]NS(0) FUSION(0): fault on , magn_heading_err_large​

The GPS lock was fine and interestingly, it reports not flipping into ATTI mode (until after impact). Also, it appears to have continued to hover for another 20 seconds or so befoer starting to move north and east (which looks like ATTI drift even though it was still reporting P-GPS), causing the collision with the tree at around 113 seconds. That loss of horizontal control was reported at 106 seconds followed by a bunch of other problems in quick succession:

106.774 : 490811221 : 5196 [L-FDI][CTRL]: fault on , horiz_ctrl_fail
107.574 : 494411776 : 5236 [L-FDI]NS(0) FUSION(0): fault off, magn_heading_err_large
109.930 : 505011057 : 5354 [L-FDI]ns req:fdi,0to0,reason:fusion.gps_yaw_err,result:fail for same index
111.074 : 510162261 : 5411 [L-FMU/LED]action changed. imu error:ns_abnormal(3)
111.134 : 510429569 : 5414 [L-FLYMODE][Ctrl<1>] REQ_RC_NORMAL ATTI ctrl_atti
111.154 : 510520807 : 5415 [L-FDI][CTRL]: fault off, horiz_ctrl_fail
113.534 : 521232526 : 5534 [L-FDI][CTRL]: fault on , impact_in_air
113.552 : 521312818 : 5535 [L-RC]craft ctrl failed!!!
113.588 : 521474004 : 5536 [L-FDI]NS(0) GYRO(0): fault on , stuck​

FLY013_01.png
But there is nothing to indicate that control was actually lost. The second graph shows stick inputs and aircraft response. Apart from the rudder input at 80 seconds that triggered the compass error, there were no elevator or aileron stick inputs after that to attempt to control it. There was a brief throttle down at 87 seconds that did produce a slight altitude drop, and a rudder input at 99 seconds that the aircraft responded to appropriately.

FLY013_02.png

In summary - that looks like a significant sensor failure, and I'd hope that DJI would replace it.
 
SAR - thank you very much for the analysis. I'll share this with my friend and get the Mavic packed up to send back to DJI. Your help is very much appreciated!
 
SAR - thank you very much for the analysis. I'll share this with my friend and get the Mavic packed up to send back to DJI. Your help is very much appreciated!

You might just want to wait until @BudWalker has taken a look - magnetic anomalies are definitely his speciality.
 
I'll just add a few things. But, first a question. Was some type of external equipment, such as a tracker, added since the previous flight (FLY012.DAT)?

At time 35 secs the heading was 39 degrees and then the AC rotated CW to a heading of 149 degrees. (35 seconds corresponds to @sar104 's 85 secs) As a result the X magnetometer should have gone from positive to negative. The #2 (front) compass responded correctly. However, the #1 (back) compass was the one being used and it did not respond correctly.
upload_2017-9-30_13-6-43.png
If the culprit is some attached external equipment then it's likely it's attached in the rear of the AC

Were there any warnings issued by the Go App about 42 secs prior to launch? The eventLog stream showed this
-42.762 : 20531827 : 1 [L-COMPASS][frame cali data] version invalid
-42.762 : 20532089 : 1 [L-COMPASS][cur cali data]fmu:0,user:0,current cali data invalid
-42.762 : 20532219 : 1 [L-COMPASS][cur cali data]fmu:1,user:1,current cali data invalid


The previous flight (FLY012) didn't exhibit any of the problems found in the incident flight. There was no compass calibration between flights.Both flights were launched from the same location.
 
Bud - thanks for weighing in. I wasn't there but understand that no external equipment was used, setup was stock and the same as previous flights. Additionally I don't know of any warnings before the flight although there was a compass error during the flight as previously stated. He did tell me that he did not have control after it took off towards the trees.
 
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Bud - thanks for weighing in. I wasn't there but understand that no external equipment was used, setup was stock and the same as previous flights. Additionally I don't know of any warnings before the flight although there was a compass error during the flight as previously stated. He did tell me that he did not have control after it took off towards the trees.

That's good information, but note what I mentioned previously - there is no record of him attempting to take control after it headed for the trees - elevator and aileron sticks were centered.
 
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SAR - yes, good point but not being there when it happened I can't answer that. I did look at the flight record and saw some stick inputs (pulled back on pitch) for a brief moment but you are right, basically neutral sticks. Will send it back and see what DJI does, will be interesting. At least with the analysis here we have a fairly good understanding of what happened, just don't know why. Basically matches what my friend said.

Thanks all for your help! Now, I need to learn how to do this kind of analysis, very interesting and helpful.

:)
 
Folks, want to give a big THANK YOU to everyone for helping analyze the data and determine what happened to my friend’s Mavic. We got it sent back to DJI and they are replacing/repairing (not sure which) his Mavic. Good on DJI, their directions for return were clear and direct and they reviewed and provided a response in just a few days.

Now, I need to learn how to analyze the data, very helpful!!
 
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