Hello guys,

I just had a remote controller error lead to a RTH Flyaway yesterday with a Mavic 2 Pro and I am trying to find out what is going on. I have spoken with my colleague and he had a similar encounter with the same drone a couple months ago, so I am concerned that this is a recurring issue now.

On this particular flight, I had two remote controller disconnections. The first one was very brief and I was able to reconnect very quickly by cycling the controller power off/on. The second disconnect caused the controller to display something along the lines of "Remote Controller Error", was beeping, and I could not see any display from the DJI application. I watched the drone rapidly rise to ~150 ft (this is my RTH altitude setting), and then proceed to pitch and fly away from me while the controller was disconnected. I then regained connection, the drone stopped drifting away from me, and was able to proceed with my flight as normal.

A couple more things of note:

-The wind speed was 5mph and in a North North-Easterly direction, but the drone took off in an East North-Easterly direction. A quick calculation of average speed given the reported distance from home and time associated with it, gives me an average speed of around 6.5 mph. This doesn't account for the rise in altitude time, and doesn't comport with a drift due to wind.

-"Setting new Return-To-Home altitude to 45m (148ft), Data Recorder File Index is 78. Setting new Maximum Flight Altitude to 120m (394 ft)" was given as a Tip uder the Flight Logs.

I have also downloaded the .DAT files from DJI Flight Assistant for Mavic, but I am unaware of how to view these logs. I am assuming these are the raw log files from the drone, and the flight files I have linked are from the controller, not the drone. I would be very interested to review the logs for the drone.


The flight log was split into two files. Here are my flight logs from both disconnects:

-Disconnect 1 Log 1/2: [backcolor=rgba(249, 249, 249, 0.3)]https://app.airdata.com/share/GQSqXn
-Disconnect 1 Log 2/2: [backcolor=rgba(249, 249, 249, 0.3)]https://app.airdata.com/share/ljNPYA

-Disconnect 2 Log 1/2 - [backcolor=rgba(249, 249, 249, 0.3)]https://app.airdata.com/share/UCSBql
-Disconnect 2 Log 2/2 - [backcolor=rgba(249, 249, 249, 0.3)]https://app.airdata.com/share/WWXHfi

In your second set of files, the flight starts on the ground with a fully charged battery, you went straight up to 143 ft and then started flying NE.
About 750 ft away, you stopped and descended to 73 ft and flew slowly towards home until losing downlink at 2:29.5 and 400 ft from home.
When the downlink was restored after 32 seconds, the drone was at 148 ft altitude and coming home, but it was 700 ft from home.

Looking deeper into the data, there is a block of time from 2:29.4 until 3:10.9, when the controller is reporting the right stick being pushed halfway forward.
This is from just before losing downlink until well after signal is regained.

The joystick data value is exactly 1221 for the whole 40 seconds which suggests this is not  due to a human pushing the stick forward.
This might account for the drone continuing to fly after downlink was lost as the uplink was still working.
What caused the drone to turn around is not shown in the data, but would have happened during the 32 seconds that the downlink was lost.

The second file shows that you closed and reopened the controller which caused the drone to lose signal and initiate RTH.
It came home normally and you cancelled and resumed flying.

Your first two files are from a separate flight 20 minutes earlier.
You won't be able to read the .dat files as they are encoded.

Something was giving spurious joystick input from 2:29.4 until 3:10.9.
I'd recommend recalibrating the controller and keeping an eye on how it performs to see if it was a one-off glitch or something worse.

Thank you very much for the input!

I will follow your recommendation to re-calibrate the joystick.

I have contracted DJI Support and was informed it would cost $65 to perform a Flight Analysis because it is out of warranty. Do you think it would be beneficial to have them look into the flight logs as well? I know from personal experience and scouring the forums that DJI Support does not provide a lot of assistance, especially in matters like this. I am thinking they could access the encoded .DAT files and may (wishful thinking) provide some feedback.

My main goal is to avoid this from happening again.

Mrothart Posted at 6-4 16:20
Thank you very much for the input!

I will follow your recommendation to re-calibrate the joystick.

Personally, I think there is very little point getting DJI to 'analyse' your data. They do not share the results with you, it appears all they want to do is prove it was not the fault of the product. You will get far more meaningful analysis of your flight from experts on this forum.

Hello there Mrothart. I am sorry for the trouble this has caused and thank you for reaching out. May we know if you have managed to update the firmware of your DJI Mavic 2 Pro remote controller and can you please try to calibrate the said remote controller as well to see if the issue will still persist and for us to be able to isolate the said issue. For reference I will post an official DJI tutorial video on how to calibrate the DJI Mavic Remote Controller. Thank you.

Hiya,

In the second flight at 2m30 MP2 lost contact, it entered a RTH (did climb to 45 meter from 22) but the heading to home was 180 degrees wrong.

At the moment of disconnect drone was flying heading 245, to home was 242, so almost aligned to the RTH heading.
At connected again MP2 was heading 064....wich should be ofcourse 242.
RTH mode was in status "Standby", so it never passed the aling and cruise mode. With a weird value for forward stick drone did fly away ofcourse as the heading was incorrect.
Beacuse of this craft moved from 132 to 214 meters away from home during the disconnection, see the charts.
So imo 2 problems, mayby 3; 1) pitch input 2) RTH stayed in standby mode  (mayby because of stick input? i don`t know) 3) Compass 'error ' *
But at connected again the 30% forward stick is in the log but the distance to home remains the same! as earlier is caused the increase of distance away...
Did check the pitch angles (see the values in the chart), at connected again it show higher up values for short period, up values to stop the move away.

* RTH aligns to craft towards home direction, using craft compass data. If craft turns 180 degrees wrong towards home than it can be a compass / imu problem.

Totally puzzled now, in the second part of the log (don`t know why they are split into 2) the heading to home is oke !  why ? see chart 4 and 5Or did the pilot yawed the craft back home?? Plus in the second part the RTH setting is changed from Hover to GoHome.

Would love to see the DAT file for this flight.



cheers
JJB

I believe I will re-calibrate my remote controller as well.  I had one flight recently where it lost connection to my drone.  Needless to say, I wasn't too pleased with that brief experience.  It did initiate RTH soon after and I was able to regain control, though, I'm not in an area with open fields, should the drone do a fly away or cease flight, so retrieving it may be a challenge at times.

Neo Supreme Posted at 6-5 02:43
I believe I will re-calibrate my remote controller as well.  I had one flight recently where it lost connection to my drone.  Needless to say, I wasn't too pleased with that brief experience.  It did initiate RTH soon after and I was able to regain control, though, I'm not in an area with open fields, should the drone do a fly away or cease flight, so retrieving it may be a challenge at times.

I believe I will re-calibrate my remote controller as well.  
I had one flight recently where it lost connection to my drone.
Losing connection is common and caused by a number of factors.
None of them would be "fixed" by calibrating the controller.
Recalibrating the controller will only reset the joystick response (which is most likely perfect anyway).

JJB, thank you so much for taking the time to look into this! It is really puzzling me. Considering the anomolies in the data and what I witnessed the drone doing, I am wondering if the drone was not using the correct Home Location and went in RTH mode to another location while disconnected.

I was under the impression that only DJI is able to view these encrypted .DAT files from the newer drones. Is there a way to view them that I am unaware of?

Here is a link to the .DAT files from the drone:

File 1/3:   https://www.dropbox.com/s/xz9ru4 ... 4_14-56-23.DAT?dl=0
File 2/3:   https://www.dropbox.com/s/1xspko ... 4_14-58-30.DAT?dl=0
File 3/3:   https://www.dropbox.com/s/nra12z ... 4_15-02-52.DAT?dl=0

Mrothart Posted at 6-5 11:51
JJB, thank you so much for taking the time to look into this! It is really puzzling me. Considering the anomolies in the data and what I witnessed the drone doing, I am wondering if the drone was not using the correct Home Location and went in RTH mode to another location while disconnected.

I was under the impression that only DJI is able to view these encrypted .DAT files from the newer drones. Is there a way to view them that I am unaware of?

Your HP was recorded in good order at 2.3 seconds in flight.

On the mobile device are DAT files too, they can be read.
If yiou can find them, in a folder same level as FlightRecords, like MCDatflight   or something like that.

Did you yawed your craft 180 degrees to get it back ??  if not that for 90% sure a compass/imu error.

if you like upload the DAT files with the same date.

cheers
JJB

JJB* Posted at 6-5 12:24
Your HP was recorded in good order at 2.3 seconds in flight.

On the mobile device are DAT files too, they can be read.

JJB,

I am not sure what you are asking about the 180 degrees. If you're speaking of how the drone turned 180 degrees and started traveling away from me while the controller was disconnected, then I did not have control over the drone at all. I watched the drone autonomously rotate 180 degrees on its' own and fly away .

Here is the only DAT file I have from my mobile device:

https://www.dropbox.com/s/x4y9d3 ... 029%5B1%5D.DAT?dl=0

Is this different than the three previous DAT files from the drone I uploaded? And how would I view this DAT file from my mobile device?

Mrothart Posted at 6-5 13:44
JJB,

I am not sure what you are asking about the 180 degrees. If you're speaking of how the drone turned 180 degrees and started traveling away from me while the controller was disconnected, then I did not have control over the drone at all. I watched the drone autonomously rotate 180 degrees on its' own and fly away .

Hi,

The DAT file  with the same data as the log = FLY026.DAT

in this log a continue of/off minor  error on a acc meter
[L-FDI]NS(0) ACC(1): FAULT ON . BIAS_MINOR
[L-FDI]NS(0) ACC(1): FAULT OFF. BIAS_MINOR

About my question, when you lost connection your drone turned away 180 from the homepoint.
Craft turned to hdg 064. (hp = 242). This log stops at 3m17.6.

Next log starts at 3m28.5, in the log the craft is heading 242.5. So what happend in these 11 seconds?
Did you turned the craft to the home heading; assuming that the upload connection was not disturbed   or did the craft turned towards hp itself?  ( see analysis4 and 5 in post #6)

cheers
JJB

JJB* Posted at 6-6 01:02
Hi,

The DAT file  with the same data as the log = FLY026.DAT

JBB,

The drone had turned on its own during those 11 seconds. Again, thank you very much for taking your time looking into this.

It seems like these log files only prove that something unusual was going on with the drone when the controller lost connection, but it can't be pinpointed and corrected. I will calibrate the controller, see if this issue occurs again, and follow up at that time.

Mrothart Posted at 6-8 07:17
JBB,

The drone had turned on its own during those 11 seconds. Again, thank you very much for taking your time looking into this.

thanks for the update

I saw only one flightrecord before where in flight suddenly the compass switch heading 180 degrees!  on a MPZoom. In that case the pilot selected a RTH after a while in wich the compass swicthed back and flew back home....

cheers
JJB