Hi DJI,

I recently had a scary experience where I almost lost my drone (Mavic Pro), due to what looks like a software bug, or at minimum, lack of a warning where there should be one.

I had RTH height and max height both set to 90m. It would seem that when they're set the same, and RTH is activated because of loss of signal, the drone will rise up to that height, and then pretty much just sit there. I have video from the SD card showing the drone moving forward slightly, then backing up again, over and over, until I ran through the forest to recover signal. If I hadn't been able to recover signal, I presume it would have continued doing that until the batteries ran down and it either crashed, or landed in the water.

DJI, a warning in the app when both are set to the same would be incredibly useful. Or, fixing RTH so that it's actually able to, you know, return to home, when they are set the same.



Before anyone jumps on me:
Yes, I realize part of the fault was mine: I flew the drone around a group of trees and out of line of sight. I was trusting RTH (with a height well above anything nearby) to bring it back into signal range if anything went wrong. However, had RTH actually done what it says it does (or had it warned me about the height settings being incompatible) this wouldn't have been an issue.

Hi. I am sorry to know what happened to your previous flight with your DJI Mavic Pro. This is not the experience we want you to have with DJI. Rest assured I will forward this thread to our DJI R&D team for further development of the product. Thank you for the suggestions and for your support.

Why set them the same ? max height UK is 400ft so my RTH is set to  120 feet(40m) and my max is set to 400 feet(130m) as per the law...

Gazmg Posted at 11-5 11:16
Why set them the same ? max height UK is 400ft so my RTH is set to  120 feet(40m) and my max is set to 400 feet(130m) as per the law...

Why not set them to the same thing? I think it's beside the point. When set to the same thing, RTH does not function, and you're given no warning that it won't function. I don't think it's unreasonable to think "I want to be absolutely sure about clearing everything, so I'll just set RTH height to the max height." and expect it to work.

Was it facing directly into the sun?

hallmark007 Posted at 11-5 12:30
Was it facing directly into the sun?

Interesting question. After it climbed and turned around to return, it was. Why? Do the forward facing obstacle detection cameras glitch out in that situation? When I manually took control (after running to pick up a signal) it had no problem flying directly toward the sun. If it was the forward facing obstacle detection, wouldn't that have prevented me from flying it too?

SurprisingEdge Posted at 11-5 13:14
Interesting question. After it climbed and turned around to return, it was. Why? Do the forward facing obstacle detection cameras glitch out in that situation? When I manually took control (after running to pick up a signal) it had no problem flying directly toward the sun. If it was the forward facing obstacle detection, wouldn't that have prevented me from flying it too?

In all dji aircraft OA will halt aircraft and it doesn’t take much just a slight turn and your ok to go, while We can’t be sure this happened I would rule it out.

hallmark007 Posted at 11-5 14:00
In all dji aircraft OA will halt aircraft and it doesn’t take much just a slight turn and your ok to go, while We can’t be sure this happened I would rule it out.

That's interesting.  I've pulled the video off the drone:


I've snipped it. About 2 seconds in, you see it stop flying. That's when I lost signal, I guess. It actually seemed like I still had remote control, but no video feed any more. It prompted to RTH, so I hit OK.

At 10 seconds, you see the drone start to rise. At 15 seconds it turns around. Then I sped up the video 6x. At 30 seconds you can see it reach it's RTH altitude, facing the sun yes. That's where it starts to go forward and back repeatedly. At around 3:30 the sun gets brighter as some clouds move out of the way.  4:00 I get control of the drone back, bring it down a bit, and RTH "runs into a wall" again. 4:08 I take control and bring it down more, and start flying it back.

I think you're right about the OC being the problem. I would have never dreamed that leaving the RTH OC would result in it being unable to fly. I figured it'd be an extra safety net, in case I forgot to set an appropriate RTH height. I'll be turning it off from now on though. I'll also be doing some testing with RTH height and max height set the same.

SurprisingEdge Posted at 11-5 14:27
That's interesting.  I've pulled the video off the drone:
https://www.youtube.com/watch?v=ucBGOTs9Swk&feature=youtu.be

It does look like the sun may have been your problem, I know with all my craft none of them would fly into that Sun, just remember if turning off OA that RTH height is set to a safe height when returning directly home.

SurprisingEdge Posted at 11-5 11:18
Why not set them to the same thing? I think it's beside the point. When set to the same thing, RTH does not function, and you're given no warning that it won't function. I don't think it's unreasonable to think "I want to be absolutely sure about clearing everything, so I'll just set RTH height to the max height." and expect it to work.

Point taken...