Lost Mavic - Flight Analysis Request

[JLane]

Hi all. A user on the DJI forums is trying to figure out what happened to his Mavic. I thought I'd post his case and flight log here, hoping some of the gurus might find a clue as to what happened. Here's a brief description of the event:

"So was out flying today and no issues at all. At about 900m from me, 200 meters and 40% battery Suddenly I get a message saying that the god signal has been lost and to fly carefully. No more than 5 seconds later the RC lost connection and I never saw my mavic again.... waited around for 20 minutes forgiving the RTH function would have worked but no luck."

The Mavic has yet to be recovered, so no .dat files for viewing. The RC log has been uploaded to here: Phantom Log Viewer - PhantomHelp.com

Any help would surely be appreciated

 

[msinger]

Please post the link to the thread here so we can check it out.

 

[Robbyg]

It does not look good.
The last piece of info says it was in ATTI mode out over the water at 660ft up with 37% battery life. It would not be able to do an RTH when it lost the signal.

Looking at it some more. Will let you know.

Rob

 

[Malavic]

ATTI but still had 19 sats? How does that happen?

 

[Eric17]

ATTI but still had 19 sats? How does that happen?

China electonics :/

 

[Robbyg]

I almost think you hit into a NFZ. Its interesting that the drone just would not pass over the line between New Jersey and New York on the map. It very accurately stayed on the Jersey side. I am not sure if you planned the flight, but it seems like a Geo Fence or it's possible that the signal was also jammed or maybe it's just the normal amount of WiFi signals that close to Manhattan. In any case you got several messages that there was strong interference followed by the craft losing GPS and going into ATTI mode and then out of it.

The big question for me is why did it go into ATTI mode in a clear area with 20 satellites. I cannot see the Sat health levels right now, but I would think at that location they would be good.

With 37% battery level and the fact that the drone did not return home from such a short distance I am getting a feeling that even if it did regain GPS at a later point, it probably headed home with inadequate power and landed in the water.

I could outline a search area from your home position going out to the shore line but it would be a fairly big area and would depend on if it got back GPS and where the wind might have blown it before it started home, if it started back home.

Rob

 

[Robbyg]

ATTI but still had 19 sats? How does that happen?

Even more interesting is how it just hugged the open water boarder between NY and New Jersey. It flew exactly on the border line! Add to that the moment he hit the border line he got a strong interference warning.

Given its proximity to the world trade center and Trump towers etc one has to wonder if Geo Fencing and some sort of Jamming system is also in place.

Rob

 

[Malavic]

Even more interesting is how it just hugged the open water boarder between NY and New Jersey. It flew exactly on the border line! Add to that the moment he hit the border line he got a strong interference warning.

Given its proximity to the world trade center and Trump towers etc one has to wonder if Geo Fencing and some sort of Jamming system is also in place.

Rob

I know they've been testing anti-drone technology at JFK, but no idea if it's been rolled out to the Port Authority. Flying at 660 feet in that airspace? That would definitely be a target for anti-drone tech. That Heliport is nearby, maybe they have it?

 

[Robbyg]

Running the Log through more detailed analysis shows something very interesting?





Almost Every 111 seconds the GPS gets hit or faults on its own.

Rob

 

[Cyberpower678]

If you ask me, the drone would be able to RTH but the constant drops in GPS Health would have interrupted the process and the drone would have just hovered. I can't do a thorough analysis, but I think it may have landed in the water. I live close to a state border myself, so I definitely will try to see if I can cross it.

 

[JLane]

Running the Log through more detailed analysis shows something very interesting?


View attachment 10422


Almost Every 111 seconds the GPS gets hit or faults on its own.

Rob

That is indeed a very interesting observation. Has anybody seen something like this before?

It's also interesting that there doesn't seem to be a corresponding drop in satellites during these regular drops in GPS health. My understanding is that the GPS health is more than just a measure of GPS signal strength, but also factors in supporting data from other sensors, is that correct? I'm thinking these 'hits' are not actually from something affecting GPS (otherwise all GPS equipment in the area would be affected) but perhaps something else causing very conflicting data, causing the Flight Controller to lower the GPS health? Eg. Could a strong pulse of magnetic interference cause the compass readings to go haywire, and therefore cause the FC to drop the GPS health rating?

A recurring 'hit' of interference could be from something like a rotating radar? Although... If the hits were about 111 seconds apart, that's almost 2 minutes between rotations. That sounds a bit slow. Perhaps this is that new anti-drone technology that @Malavic mentioned?

 

[Malavic]

That is indeed a very interesting observation. Has anybody seen something like this before?

It's also interesting that there doesn't seem to be a corresponding drop in satellites during these regular drops in GPS health. My understanding is that the GPS health is more than just a measure of GPS signal strength, but also factors in supporting data from other sensors, is that correct? I'm thinking these 'hits' are not actually from something affecting GPS (otherwise all GPS equipment in the area would be affected) but perhaps something else causing very conflicting data, causing the Flight Controller to lower the GPS health? Eg. Could a strong pulse of magnetic interference cause the compass readings to go haywire, and therefore cause the FC to drop the GPS health rating?

A recurring 'hit' of interference could be from something like a rotating radar? Although... If the hits were about 111 seconds apart, that's almost 2 minutes between rotations. That sounds a bit slow. Perhaps this is that new anti-drone technology that @Malavic mentioned?

Airport radar has a much higher refresh rate than 111 seconds. It's more like every 2 to 3 seconds that it does a full rotation. This does not preclude that something else is afoot. The military can intentionally degrade GPS signals. There's no evidence that this is happening...that said, I would be interested to see someone else just park a Mavic somewhere in the area and then reviews the GPS signal strength. I work about 12 miles from that area, maybe I'll just log the GPS signal and see what it looks like. I know they can't localize the GPS signal that much so this entire region would be affected if it came from the sats. It's more likely that it's some local interference or a problem with the Mavic itself.