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Help me understand what happened here: hard crash due to DJI NFZ causing aircraft lose of control and hit tree

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adiru

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So I was flying the other day in an area that has no other NFZ restrictions other than an altitude restriction of 150 meters. Right as I'm about to come in for a landing, the Mavic 2 seems to have a mind of its own, and basically flew a horizontal track at immense speed across the field and struck a tree at high speed before crashing to the ground causing damage to the foot and the battery completely popped out in the process.


1598834396681.png


Why did it do this instead of coming straight down or allowing me time to land it myself? I was handflying it and taking pictures and it was clear day, perfect weather, no winds, and everything was fine (got full GPS lock etc) no obstructions and wasn't flying near buildings or anything and then it started complaining about entering no fly zone, however where I'm at it was an altitude restriction and I was flying WELL UNDER the 150 meter restriction so that shouldnn't have even been a factor or point of contentionn at all...

In any case, what caused the crash was the Mavic going crazy and suddenly decided to basically track horiztonally on the ground at high speed until it struck a tree...

Later I tried to get export of the logs from the aircraft itself but I tried on Windows 7 machine, and two different Windows 10 machines, and all were brand new installs of the latest DJI Assistant app (for desktop PC) for the Mavic 2 version (I also tried the generic old DJI Assistant 2 app etc) but it will just spin and spin and not ever actually show me any logs to even allow me to export to provide to DJI.

I know these logs on the aircraft are encrypted but I should at least be able to export them to send to DJI upon request and its not even letting me do that!



1598834451333.png
 
Last edited:
Thomas B said:
Reinstall the battery and see if that helps.
Click to expand...

What do you mean reinstall? I have two batteries, I've already tried both of them.... Also the DJI Mavic is recognized by the DJI Assistant app it just won't show any logs for me to export, the Mavic is fully powered and the battery is always at near 100% whenever I connect it to my computer. Its also not a driver signing issue because I also tried in Windows 7 in addition to Windows 10 and have tried with signing check turned off etc...
 
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If you can post the .TXT and .DAT log files in the phone, more insight can be obtained. I doubt very much if the incident was caused by the drone flying inside the altitude restriction zone.
 
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boblui said:
If you can post the .TXT and .DAT log files in the phone, more insight can be obtained. I doubt very much if the incident was caused by the drone flying inside the altitude restriction zone.
Click to expand...

Okay you mean check in my android phone? I was using the DJI Go app (not litchi or anything else) at the time, and also I was handflying, not on autopilot, and then after hearing female voice about a NoFlyZone etc before I could even respond I saw the mavic tracking across the sky at rapid speed (moving horiztonally) and I wasn't giving those command inputs, it had mind of its own and then crashed into tree. It was perfect clear sky, no winds, no obstacles, and I've flow this unit for more than a year and never once crashed nor had anything wierd like this going on before.

I was also recording at the time a video, when I recovered Drone the video didn't even exists on the SD card, I think the battery fell out when it hit the tree and whatever was recorded was lost.
 
uploaded
 

Attachments

  • DJIFlightRecord_2020-08-29_[09-24-30].txt
    8 KB · Views: 26
  • DJIFlightRecord_2020-08-29_[09-18-40].txt
    217 KB · Views: 20
01m 28.8sP-GPS17301.8ft39.7ft2.8mph122.7ft93%16.20V4.051V4.053V4.058V4.039V0.012V100%
01m 29.2sP-GPS17301.5ft39.7ft1.3mph121.6ft93%16.20V4.051V4.053V4.058V4.039V0.012V100%
01m 29.6sP-GPS17301.5ft39.7ft3.8mph120.9ft93%16.20V4.051V4.053V4.058V4.039V0.012V100%
01m 30.0sP-GPS17302.2ft39.7ft5.5mph123.2ft93%15.39V3.846V3.862V3.851V3.833V0.013V100%
J01m 30.4sP-GPS17302.2ft39.7ft7.0mph127.9ft93%15.39V3.846V3.862V3.851V3.833V0.013V100%Not Enough Force/ESC ErrorView
01m 30.5sP-GPS17302.5ft39.7ft7.5mph128.1ft93%15.39V3.846V3.862V3.851V3.833V0.013V100%Not Enough Force/ESC Error
01m 30.6sP-GPS17302.2ft39.7ft8.0mph129.9ft93%15.39V3.846V3.862V3.851V3.833V0.013V100%Not Enough Force/ESC Error
01m 30.7sP-GPS17302.2ft39.7ft8.6mph130.1ft93%15.49V3.864V3.876V3.890V3.864V0100%Not Enough Force/ESC Error
01m 30.8sP-GPS17302.2ft39.7ft9.1mph131.4ft93%15.49V3.864V3.876V3.890V3.864V0100%Not Enough Force/ESC Error
01m 30.9sP-GPS17302.2ft39.7ft9.4mph131.6ft93%15.49V3.864V3.876V3.890V3.864V0100%Not Enough Force/ESC Error
01m 31.0sP-GPS17301.5ft39.7ft9.4mph132.1ft93%15.49V3.864V3.876V3.890V3.864V0100%Not Enough Force/ESC Error
01m 31.1sP-GPS17301.5ft39.7ft9.5mph132.1ft93%15.49V3.864V3.876V3.890V3.864V0100%Not Enough Force/ESC Error
01m 31.2sP-GPS17301.2ft39.7ft9.4mph132.0ft93%15.49V3.864V3.876V3.890V3.864V0100%Not Enough Force/ESC Error
01m 31.3sP-GPS17300.9ft39.7ft9.1mph131.8ft93%15.49V3.864V3.876V3.890V3.864V0100%Not Enough Force/ESC Error
01m 31.4sP-GPS17300.2ft39.7ft8.5mph131.1ft93%15.49V3.864V3.876V3.890V3.864V0100%Not Enough Force/ESC Error
01m 31.5sP-GPS17300.2ft39.7ft7.9mph130.8ft93%15.49V3.864V3.876V3.890V3.864V0100%Not Enough Force/ESC Error
01m 31.6sP-GPS17299.5ft39.7ft7.1mph129.9ft93%15.49V3.864V3.876V3.890V3.864V0100%Not Enough Force/ESC Error
01m 31.7sP-GPS17299.5ft39.7ft5.8mph129.4ft93%15.51V3.867V3.886V3.892V3.868V0.001V100%Not Enough Force/ESC Error
01m 31.8sP-GPS17298.9ft39.7ft4.9mph128.4ft93%15.51V3.867V3.886V3.892V3.868V0.001V100%Not Enough Force/ESC Error
01m 31.9sP-GPS17299.2ft39.7ft3.5mph127.9ft93%15.51V3.867V3.886V3.892V3.868V0.001V100%Not Enough Force/ESC Error
01m 32.0sP-GPS17298.9ft39.7ft2.6mph126.9ft93%15.51V3.867V3.886V3.892V3.868V0.001V100%Not Enough Force/ESC Error
01m 32.1sP-GPS17299.5ft39.7ft1.6mph126.3ft93%15.51V3.867V3.886V3.892V3.868V0.001V100%Not Enough Force/ESC Error
01m 32.2sP-GPS17299.5ft39.7ft1.6mph125.0ft93%15.51V3.867V3.886V3.892V3.868V0.001V100%Not Enough Force/ESC Error
01m 32.3sP-GPS17300.2ft39.7ft1.2mph124.3ft93%15.51V3.867V3.886V3.892V3.868V0.001V100%Not Enough Force/ESC Error
01m 32.4sP-GPS17300.2ft39.7ft1.1mph122.8ft93%15.51V3.867V3.886V3.892V3.868V0.001V100%Not Enough Force/ESC Error
01m 32.5sP-GPS17300.9ft39.7ft0.8mph122.0ft93%15.51V3.867V3.886V3.892V3.868V0.001V100%Not Enough Force/ESC Error
01m 32.6sP-GPS17301.2ft39.7ft1.2mph120.6ft93%15.51V3.867V3.886V3.892V3.868V0.001V100%Not Enough Force/ESC Error
01m 32.7sP-GPS17301.8ft39.7ft0.8mph119.9ft93%15.35V3.831V3.839V3.847V3.837V0.006V100%Not Enough Force/ESC Error
01m 32.8sP-GPS17302.5ft39.7ft1.8mph119.0ft93%15.35V3.831V3.839V3.847V3.837V0.006V100%Not Enough Force/ESC Error
01m 32.9sP-GPS17302.8ft39.7ft2.3mph118.6ft93%15.35V3.831V3.839V3.847V3.837V0.006V100%Not Enough Force/ESC Error
01m 33.0sP-GPS17303.5ft39.7ft4.3mph118.1ft93%15.35V3.831V3.839V3.847V3.837V0.006V100%Not Enough Force/ESC Error
01m 33.1sP-GPS17303.8ft39.7ft5.8mph118.2ft93%15.35V3.831V3.839V3.847V3.837V0.006V100%Not Enough Force/ESC Error
01m 33.5sP-GPS17302.2ft39.7ft9.2mph118.5ft93%15.35V3.831V3.839V3.847V3.837V0.006V100%
01m 33.9sP-GPS17299.5ft39.7ft14.8mph113.9ft93%16.06V4.001V4.017V4.025V4.020V0.016V100%
K01m 34.2sAutoLanding17297.9ft39.7ft18.6mph110.1ft93%16.06V4.001V4.017V4.025V4.020V0.016V100%Obstacle Avoidance will be disabled in landing. Mode changed to AutoLanding.View
01m 34.6sAutoLanding17294.9ft39.7ft24.6mph110.6ft93%16.06V4.001V4.017V4.025V4.020V0.016V100%
01m 35.0sAutoLanding17289.7ft39.7ft21.6mph113.8ft93%16.24V4.043V4.060V4.073V4.066V0.017V100%
01m 35.4sAutoLanding17282.5ft39.7ft20.0mph116.3ft93%16.24V4.043V4.060V4.073V4.066V0.017V100%
01m 35.8sAutoLanding17274.0ft39.7ft18.1mph115.3ft93%16.12V4.013V4.030V4.038V4.035V0.017V100%
01m 36.2sAutoLanding17264.4ft39.7ft15.0mph108.5ft93%16.12V4.013V4.030V4.038V4.035V0.017V100%
01m 36.6sAutoLanding17254.6ft39.7ft16.3mph99.0ft93%16.12V4.013V4.030V4.038V4.035V0.017V100%
01m 37.0sAutoLanding17242.8ft39.7ft20.9mph89.3ft93%16.11V3.998V3.997V4.047V4.070V0.001V100%
01m 37.4sAutoLanding17228.3ft39.7ft27.4mph81.8ft93%16.11V3.998V3.997V4.047V4.070V0.001V100%
01m 37.8sAutoLanding17215.6ft39.7ft26.2mph76.7ft93%16.32V4.090V4.092V4.089V4.054V0.035V100%
01m 38.2sAutoLanding17199.5ft39.7ft30.8mph77.3ft92%16.32V4.090V4.092V4.089V4.054V0.035V100%
01m 38.6sAutoLanding17182.7ft39.7ft36.8mph85.4ft92%16.32V4.090V4.092V4.089V4.054V0.035V100%
01m 39.0sAutoLanding17165.7ft39.7ft46.3mph97.9ft92%16.27V4.034V4.075V4.084V4.081V0.041V100%
01m 39.4sAutoLanding17150.9ft39.7ft51.7mph112.4ft92%16.27V4.034V4.075V4.084V4.081V0.041V100%
01m 39.8sAutoLanding17136.2ft39.7ft53.1mph126.8ft92%16.30V4.057V4.078V4.090V4.079V0.021V100%
01m 40.2sAutoLanding17120.4ft39.7ft53.2mph142.4ft92%16.30V4.057V4.078V4.090V4.079V0.021V100%
01m 40.6sAutoLanding17104.3ft39.7ft56.0mph161.3ft92%16.30V4.057V4.078V4.090V4.079V0.021V100%
01m 41.0sAutoLanding1789.2ft39.7ft55.8mph182.6ft92%16.35V4.100V4.114V4.090V4.042V0.048V100%
01m 41.4sAutoLanding1774.8ft39.7ft56.5mph204.7ft92%16.35V4.100V4.114V4.090V4.042V0.048V100%
01m 41.8sAutoLanding1759.1ft39.7ft55.9mph228.7ft92%16.35V4.108V4.121V4.094V4.025V0.069V100%
01m 42.0sAutoLanding1752.2ft39.7ft56.8mph241.1ft92%16.35V4.108V4.121V4.094V4.025V0.069V100%Reached maximum speed of 56.8 mph.
01m 42.4sAutoLanding1740.0ft39.7ft54.4mph264.7ft92%16.35V4.108V4.121V4.094V4.025V0.069V100%
01m 42.8sAutoLanding1727.6ft39.7ft54.3mph288.2ft92%16.35V4.108V4.121V4.094V4.025V0.069V100%
01m 43.2sAutoLanding1617.1ft9.8ft52.6mph311.1ft92%16.02V3.990V3.986V4.008V4.031V0.004V100%92% Battery at maximum distance.
 
It seems that the sticks are not flying in mode 2. Can you let me know the mode used ?
 
boblui said:
It seems that the sticks are not flying in mode 2. Can you let me know the mode used ?
Click to expand...

I switched it to whatever mode the first mavic 1 pro was using out of the box, don't know if that was mode 1,2,3 etc... but I got used to that mode and go when flying the Mavic 2 I used that same mode... I have always flown in this same mode, its not a mode issue.

But if you look at the data, the crash into the tree occured when the Mavic was in autolanding mode, and autoland sent it to going 55mph! into a a tree, I wasn't making the inputs to tell it to fly 55mph! (regardless of mode, as you can see the input was basically null)

Why would autoland send it going 55mph+? doesn't make any sense...
 
adiru said:
its not a mode issue.
Click to expand...

Surely the crash is not due to the mode used but I need to know which stick controls what ( ie, the mode ) in order to interpret the data correctly.

It appears to me that it's a typical fly away due to incorrect initialization of yaw. The .DAT log file is needed in order to verify it. You may follow this thread to get the .DAT file in the phone : Mavic Flight Log Retrieval and Analysis Guide
 
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.DAT logs here, its mainly the FLY056
I think the FLY057 log is when I put the battery back and attempted a powerup after the post crash event
 

Attachments

  • 20-08-29-09-24-01_FLY057.DAT
    345.3 KB · Views: 9
  • 20-08-29-09-18-19_FLY056.DAT
    1.2 MB · Views: 13
That it happened in a warning zone is a coincidence and probably had nothing at all to do with the flight outcome.
At worst, an NFZ will cause a landing, not a runaway incident.
adiru said:
I switched it to whatever mode the first mavic 1 pro was using out of the box, don't know if that was mode 1,2,3 etc... but I got used to that mode and go when flying the Mavic 2.
Click to expand...
You were using a joystick mode that was different from the standard mode 2 which is the default for every DJI drone.
That didn't have any effect on the crash but not knowing which stick does what makes it hard to decipher the data.
adiru said:
Why would autoland send it going 55mph+? doesn't make any sense...
Click to expand...
High speed runaway issues are usually caused by yaw error situations.
Can you describe your launch spot?
What was the surface you launched from?
Did you place the drone and power up or did you move the drone after powering up?
 
Last edited:
boblui said:
It appears to me that it's a typical fly away due to incorrect initialization of yaw.
Click to expand...
There are similarities, but also significant differences.
The runaway path is straight and the issue happened long after the drone had been flown at all headings rather than running away after the drone turned away from its initial heading.
 
i'm trying to get the video from cache but just realized in mavic 2 the .dat is encrypted? so onnly DJI can make use of it?
 
By comparing the yaw values in the .TXT file and those in the .DAT file, it is found that IMU1 was used.

Things were basically OK until 90 seconds into the flight when the IMU suddenly didn't trust the compass or the gyro and came up with a yaw value that was wayyyyy off. There were moments in which the sensed orientation ( yaw angle ) of the craft was opposite to the actual direction. Fly away is ensured.

1598859709959.png

This is not the first time such odd behaviour of the M2 is reported. ie, all the sensor outputs basically agree with each other but the sensor fusion algorithm came up with a totally different value of the parameter being sensed ( tilt angle, height, yaw, etc ). I can only say this is a firmware bug. Hope other members can chime in and shed some light on the reason behind.

This was my Mini flying with similar amount of yaw error. Although the error was due to the drone being powered on under high magnetic interference ( hence pilot error ) instead of firmware bug, the result is the same.

 
Last edited:
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What triggered initial forced autoland?

Was it the brief ESC errors or the NFZ warning

If ESC, the motors were not being taxed, no winds, no fast speeds, no high altitudes, and on fresh, full, good batteries

The area I was flying under only had a NFZ altitude restriction of 150meters, I was well under that height at all times.

Even if IMU disagree, why would it go up to 56mph? during forced autoland? I recall seeing propellers in the view, so the Mavic must have tilted itself at a huge angle, this is something impossible for me to do via manual input during flight not to mention it was in autoland and not listening to mt inputs.

I had recent just updated the firmware due to DJI nagging me about it each time Im flying. Any ideas if this bug firmware specific and if so, can I revert and downgrade? Like I said been flying for a year never an issue until now.

How did you read the .DAT? Didnt DJI encrypt it for M2 or did the decryption key get released or leaked?


Thanks
 
My concern is it this bug repeats itself next time it will be a flyaway or a total crash that wrecks it beyond hope of repair.... if indeed its a firmware bug the DJI should be responsible
 
boblui said:
By comparing the yaw values in the .TXT file and those in the .DAT file, it is found that IMU1 was used.

Things were basically OK until 90 seconds into the flight when the IMU suddenly didn't trust the compass or the gyro and came up with a yaw value that was wayyyyy off. There were moments in which the sensed orientation ( yaw angle ) of the craft was opposite to the actual direction. Fly away is ensured.

View attachment 112009

This is not the first time such odd behaviour of the M2 is reported. ie, all the sensor outputs basically agree with each other but the sensor fusion algorithm came up with a totally different value of the parameter being sensed ( tilt angle, height, yaw, etc ). I can only say this is a firmware bug. Hope other members can chime in and shed some light on the reason behind.

This was my Mini flying with similar amount of yaw error. Although the error was due to the drone being powered on under high magnetic interference ( hence pilot error ) instead of firmware bug, the result is the same.

Click to expand...

Are there any clues that this bug may bite? Maybe frequent "calibrate compass" messages in prior flights; odd behavior in prior flights?
 

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