Hello Forum,

I'm a proud DJI Mavic Pro user since the middle August. I would like to share something happened today that scared me a little bit. Maybe together we could find out what happened and avoid future crashes.

Today I was flying 830m far at 10m of altitude over a little lake near Ticino river in the northern Italy. The controller signal was very good and the same was the video downlink to the controller and DJI goggles.

Suddently, at 9m5s, the gimbal turned up all the way quickly and a couple of seconds later the video downlink and controller uplink stopped. The contoller showed the message "Disconnected" and the same did DJI Go 4 and the DJI goggles. Very unusual, the signal was very good and I wasn't moving.

Luckily 10 seconds later the drone reconnected itself and it seems to be already in RTH mode.

The video recording stopped at the same moment the incident happened. And the last video file size is exactly 4GB. Strange, isn't it? I suppose that could be something related to video file rollup. Probably the thread saving video file crashed and part of the software restarted making the gimbal go up, video stopped recording and the signal to break for 10s (with consequent RTH).

Here the link of the flight log for you: http://www.phantomhelp.com/LogViewer/DX9M9QH8892C8G1ZT5QQ/#
DJI case: 758534

Looking forward for your opinions
Thank you

So the drone showed disconnected when the gimbal moved up and down, then it recovered itself, right? Could you please help to check if the video recorded the gimbal behaviour in the SD card, or it is just the transmission video. If it reserved on the SD card, could you please help to export it out, upload it to Dropbox and paste the link here? Thank you so much. Besides, if the transmission signal lost, you can also try to adjust the antennas to regain the signal.

It looks to me like the signal was blocked possibly by the trees as you were not very high when the signal was lost and the signal returned when the drone ascended to RTH.

Q: So the drone showed disconnected when the gimbal moved up and down, then it recovered itself, right? Could you please help to check if the video recorded the gimbal behaviour in the SD card, or it is just the transmission video.

Hi Thor and thank you for your help.

*  At 9m5s the gimbal suddently went itself all the way up to horizon and a second later I've lost video and control signal for 10s. At the moment of the incident the signal was full and realiable and I was perfectly still and firm.
* The aircraft stopped recording at the same moment of the incident
* The last file on the SD card size is 4GB, nothing more or less

Searching deeper in the forum I found out that at 9m5, during 4GB file rotation, sometimes a bug occurred to some users and they lost recording and video:
https://forum.dji.com/forum.php?mod=viewthread&tid=101740#pid877286

Maybe this could be the cause of what I've experienced yesterday. Do you agree?
In my case I've lost also the control of the aircraft and it switched to RTH.



Q: It looks to me like the signal was blocked possibly by the trees as you were not very high when the signal was lost and the signal returned when the drone ascended to RTH.


I can absolutely ensure you that I was still and firm with full signal to the aircraft and suddently I've lost the video downlink and control uplink. One second before the incident the gimbal turned itself all the way up.

MPV Posted at 2017-9-25 00:49
Q: So the drone showed disconnected when the gimbal moved up and down, then it recovered itself, right? Could you please help to check if the video recorded the gimbal behaviour in the SD card, or it is just the transmission video.

Hi Thor and thank you for your help.

this is what i suspect as well, you encountered a gimbal reset and it was not trees or anything.    mine does this at 3.88GB, but otherwise all the same. it can have 100% perfect signal, the video almost always stops before the reset occurs so hard to prove it without screen capturing it.  for reasons i dont understand the aircraft disconnects with gimbal resetting.  sometimes connecting then disconnecting and then reconnecting again several times even with solid signal..

if it was trees the signal would fade, not suddenly drop out..

Do you sincerely think that this could be fixed in the next firmware releases? It was quite scary...

Thank you

Analyzing the flight logs I noticed also that the aircraft started rising, but beginning "RTH: Cruise" before the RTH level (60m) was fully reached:





See the distance going down at the same time the altitude is increasing...

It's becoming more and more scary to me...