DJI Drone Help Forum

My drone crashed into the water. HELP please!

Dear all,
I lost my MAVIC PRO in landing process.
After flight and recording near and above the river,
I controlled the drone slowly backward to the landing point.
But suddenly the drone rushed to the forward direction very fast and then clashed into the water. And the camera also changed.
I tried to control, but useless.
I checked the log and the log shows my drone’s trace,
The log show that my drone rushed to the river by backward, but I never changed the direction and the last video also shows same as I remembered.

Please help my accident.

from 3:20 the crash is recorded

Interesting. In 3 secs the Yaw changed 180° but the MP had not changed heading. That caused the MP to fly the wrong direction when it attempted to make a small correction. It only got worse from there with each attempted correction causing a larger error.
The top plot shows the Yaw value changing without control input. The bottom plot shows the difference between the GPS derived and the IMU velocities.

We’ll need the tablet .DAT to determine the cause. Look here to see how to get that .DAT. It’ll be the .DAT labelled xxxFLY089.DAT.

Offhand I’d guess that the Z axis Gyro started reporting incorrect values.

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Something went horribly wrong here. Per the data, the aircraft speed went from 6mph to 25mph in 100ms. That is not physically possible.

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Dear BudWalker,
Thank you very much for your advice.

I linked the DAT file because the file is too big to upload.

DAT file link

Thank you very much again for your help!

Thank you very much for your advice.
I’d like to ask for sufficient support or replacement to DJI.
Thank you again!

My speculation that the incident was caused by a faulty gyro is incorrect. It’s clear that the 180° change in Yaw was done by the FC and not as a result of any sensor data. E.g., this plot shows the Yaw (red) and the integrated gyroZ values.

The eventLog stream provides some hints about why this happened. Using the eventLog stream is always problematical as it is unclear what many of the entries actually mean. Anyway, it appears that IMU(0) was the active IMU and the FC switched to IMU(1) at about the time the Yaw value started changing. I’m speculating the the switch from IMU(0) to IMU(1) didn’t go well.

831.616 : 46862 [L-NS][comm] ext ns disconnect2
831.672 : 46865 [L-FDI]NS(0) FUSION(1): fault on , disconnect
831.672 : 46865 [L-FDI]ns req:fdi,1to0,reason:imu.disconnect,result:succeed
831.672 : 46865 [L-FDI][SWITCH] req:2,1->0,result:6,serr:1000617,derr:5
831.673 : 46865 [L-IMU][heading] state: drift
831.673 : 46865 [L-FMU/DM]Busy Device Changed. Type:imu0_local, <ID:15 idx:1–>ID:7 idx:0>, change tim
831.711 : 46866 [L-NS][comm] ext ns connect2

Coincidentally, there had been several (at least 100) entries that looks like the FC was attempting to auto calibrate the compass.
830.335 : 46798 [L-COMPASS][mag auto cali(0)] init|

What does all this mean? Don’t know for sure but it seems that the cause is due to some FC error and is not a HW issue or a pilot caused error. You may have to hammer on DJI to get them to see this. Good luck.

As @BudWalker mentioned, there are many discrepancies in the log file apparently. Whatever these “exactly” mean are un-clear. These repeated “Compass Cal Init’s” show basically the same value and error code each of the numerous times reported. I have no idea.

Not sure where this came from. But, as I recall, one of the converters computes the speed in a way that is sensitive to the relatively low sample rate. Based on successive GPS coordinates. Using speedX and speedY (which is actually velocities North and East) gives more believable results.

This came from the log file, if that is what you meant.

Which converter. And, column headings would help some.

Here is the entire log extracted from motor start.

19-08-02-07-05-44_FLY089.log.txt (37.1 KB)