Earlier today I was flying my Mavic at a beach in Mexico. Everything was excellent, 18 GPS satellites, 54% battery, clear video transmission. I was moving it slightly horizontally, but far from any obstacles. All of a sudden, I got "Aircraft disconnected" on the display, and the prompt about initiating return to home. I said yes, and nothing happened after that. All of the numbers on the remote controller and the app remained frozen as they were. I got up from where I was and I started walking over to where it was (about a 15 minute walk and I knew the battery wouldn't last that long). The remote controller stayed with "Connecting..." for the rest of the time. At some point I turned it off and back on when I realized it wasn't going to reconnect.

It is now completely lost. It soon got dark and it was too tricky to try and get to the top of the hills that surround the beach. I'm heading back there in the morning to look for it. I don't know if it's in the sea or on the rocks. The satellite view shows it right on the border (may even depend on the tide level).

The flight record shows nothing unusual, and even confuses me more. There appears to be no issue other than the aircraft disconnected message at the final moment that it is aloft.

Does anyone know how long the lights will continue flashing if it is still alive? My girlfriend said she saw it flashing on the hill that it was flying over. Even more strangely, my friends who were conducting a ground search said after some of us left to climb, after it was dark, that they saw the drone go up in the air with the lights flashing. They swear it wasn't anything else. One said she assumed it was "trying to look" for me.

I contacted DJI support and they said they have opened a case. Time will tell.

This is my final location according to the flight log. 233.6 feet up.

Dubwilcox Posted at 2017-7-31 01:43
[view_image]

This is my final location according to the flight log. 233.6 feet up.

There's a file on your mobile device that contains a lot of information about that flight, and we may be able to suggest where to look if you upload it to PhantomHelp. The instructions for retrieving and uploading the file are here, and once it's uploaded you can provide a link to it in this thread. You'll eventually be asked for the same thing on MavicPilots where I see you've cross-posted about this.

Could you PM me your case number? We will keep follow up for you.

I had a very similar thing happen with my mavic. I'm still waiting to hear back from Dji, its been a week or so. Download the RC log files. . Mine had a file called fatal.log. I'm curious if its battery related or what.

would be interesting to see yr flight record/data - can you upload a link to view this?

Here is the log file from my phone: July 30th Log File

Dubwilcox Posted at 2017-7-31 10:45
Here is the log file from my phone: July 30th Log File

Sorry for your loss. About a minute before the weak signal message the flight mode changes to Forced Landing -- I think your VPS system might have been telling the Mavic it was too low and initiated a forced landing where it was, then started descending until the signal was lost behind that rise?

IMU height is the 4th column, followed by VPS height. Remember that IMU height is height above the launch site, whereas VPS height is detected by sonar and maybe the twin downward-facing cameras?

Could you have been over the hill instead of over the water? Shame your downlink video cut out because you ran out of cache room. Anyway, hope you find it.

10m 45.1s

P-GPS

18satellites

393.7ft

0.7ft

14.3mph

4,070.7ft

58%

11.394V

3.798V

3.798V

3.798V

0V

10m 45.2s

P-GPS

18satellites

393.7ft

0.3ft

14.1mph

4,072.5ft

58%

11.394V

3.798V

3.798V

3.798V

0V

10m 45.3s

Forced Landing

18satellites

393.7ft

0.3ft

14.1mph

4,074.3ft

58%

11.394V

3.798V

3.798V

3.798V

0V

mryeje1 Posted at 2017-7-31 03:50
I had a very similar thing happen with my mavic. I'm still waiting to hear back from Dji, its been a week or so. Download the RC log files. blackbox files. Mine had a file called fatal.log. I'm curious if its battery related or what.

Sorry to hear that, how did you contact the DJI Support, email or chat?  Do you have a case number or ticket number? Please provide me with your case number or ticket number, I'd like to escalate it for you.

Sorry for your loss, have you synced the flight records and provided your DJI account email to the Support? What is your case number? I'd like to check the status of this case for you.

Ex Machina Posted at 2017-7-31 12:39
Sorry for your loss. About a minute before the weak signal message the flight mode changes to Forced Landing -- I think your VPS system might have been telling the Mavic it was too low and initiated a forced landing where it was, then started descending until the signal was lost behind that rise?

IMU height is the 4th column, followed by VPS height. Remember that IMU height is height above the launch site, whereas VPS height is detected by sonar and maybe the twin downward-facing cameras?

I see that. I have never encountered a Forced Landing before. Should it have warned me on either the remote controller or the app? I know without a doubt that I was well above the hill because I could see the lights and the video showed a large distance between the surface and the camera.

It's difficult to make sense of any attempt to land being the reason for the loss, as the Aircraft Disconnected message appeared instantly, with no breakup of the video or signal like I've seen in the past when there are obstacles in the terrain.

I might add that I saw "Stick Error" appear on the remote controller when I restarted it, about 5 minutes after the disconnection.

Yes, it is a shame that the downlink video wasn't cached. There is 60+GB free on the phone, but it appears the firmware update reset the setting on me. I must have overlooked that when I checked the settings.

If for some reason it did try to land on the hill, wouldn't it continue to flash for some time with 54% battery? We climbed up and reached the top about 30 minutes after it was lost when it was beginning to get dark. I had the remote controller with me and it never reconnected. I also couldn't enable the beacon light or alert sounds in the Find My Drone menu, as it said "Drone not connected". The coordinates also show it over the water. I dove around there for 2 hours today looking for any trace of it. Never found a thing. Tomorrow I'll try another ground search up on the hill.

DJI Diana Posted at 2017-7-31 19:37
Sorry for your loss, have you synced the flight records and provided your DJI account email to the Support? What is your case number? I'd like to check the status of this case for you.

Thank you, Diana. I have sent you a PM with the case number and answers to your questions.

Ex Machina Posted at 2017-7-31 12:39
Sorry for your loss. About a minute before the weak signal message the flight mode changes to Forced Landing -- I think your VPS system might have been telling the Mavic it was too low and initiated a forced landing where it was, then started descending until the signal was lost behind that rise?

IMU height is the 4th column, followed by VPS height. Remember that IMU height is height above the launch site, whereas VPS height is detected by sonar and maybe the twin downward-facing cameras?

My understanding is that we need to turn off VPS whenever fly over the water, it also says in the manual to do so. Pretty sure reflective surfaces can mess with the VPS system.

Looks like it (force?) landed in the sea?

Did you have landing protection on? Looks like maybe the VPS sensors were confused and decided to activate auto landing?

cristianc Posted at 2017-7-31 21:50
My understanding is that we need to turn off VPS whenever fly over the water, it also says in the manual to do so. Pretty sure reflective surfaces can mess with the VPS system.

That's an interesting thought. I was a few hundred feet above the surface of the water so I didn't think the built in protections like VPS would be an issue. As for the water being a reflective surface, this was about an hour before sunset behind that hill where it was flying so the water was pretty flat and opaque in this area.

Hm, I too thought that VPS would be a problem only if you are below 10m over the water. Should VPS be disabled regardless of altitude over the surface? I fly a bit over water (a lot of water here), so I'd like to avoid a situation like this. Can VPS be disabled in-flight, and then re-enabled before landing when over ground?

Also, for the future, I ordered this https://www.loc8tor.com/ in case Mavic ever lands by itself and I need to find it (provided it happens over land).

BumblerBee Posted at 2017-8-1 00:07
Hm, I too thought that VPS would be a problem only if you are below 10m over the water. Should VPS be disabled regardless of altitude over the surface? I fly a bit over water (a lot of water here), so I'd like to avoid a situation like this. Can VPS be disabled in-flight, and then re-enabled before landing when over ground?

Also, for the future, I ordered this https://www.loc8tor.com/ in case Mavic ever lands by itself and I need to find it (provided it happens over land).

Ideally, the "Find My Drone" option in the DJI Go app should allow you to locate it, initiate light and sound alerts, and even see what can be seen from the camera, provided the Mavic still has power. In my case it didn't do anything because something terrible obviously happened to it.

Dubwilcox Posted at 2017-7-31 20:24
Thank you, Diana. I have sent you a PM with the case number and answers to your questions.

Got it, just checked your case, the support submitted a data analysis, our appropriate team is working on it now, the support will get back to you once it is finished, I'll keep an eye on it also.

I almost hit a seagull  the other day, you think it could have been a bird attack?

Dubwilcox Posted at 2017-7-31 22:54
That's an interesting thought. I was a few hundred feet above the surface of the water so I didn't think the built in protections like VPS would be an issue. As for the water being a reflective surface, this was about an hour before sunset behind that hill where it was flying so the water was pretty flat and opaque in this area.

I was a few hundred feet above the surface of the water so I didn't think the built in protections like VPS would be an issue.

They shouldn't have been, but the combination of a bad VPS reading and you pulling back on the throttle caused it to start landing. The last reported location was here, which puts it over water, and since the winds were light I doubt it would have drifted much from that location on its way down.

The important thing, though, is that incorrect VPS sensor readings appear to have been the main cause of your loss, so my guess is that you'll get a warranty replacement.

DJI Diana Posted at 2017-8-1 01:28
Got it, just checked your case, the support submitted a data analysis, our appropriate team is working on it now, the support will get back to you once it is finished, I'll keep an eye on it also.

I appreciate it, Diana. Thank you.

R&L Aerial  Posted at 2017-8-1 02:27
I almost hit a seagull  the other day, you think it could have been a bird attack?

I thought about it. But when I say the aircraft disconnected message appeared suddenly, I mean it. Not even a jitter on the camera. I didn't see any erratic movement from where I was, nor any group of birds.

DroneFlying Posted at 2017-8-1 02:33
I was a few hundred feet above the surface of the water so I didn't think the built in protections like VPS would be an issue.

They shouldn't have been, but the combination of a bad VPS reading and you pulling back on the throttle caused it to start landing. The last reported location was here, which puts it over water, and since the winds were light I doubt it would have drifted much from that location on its way down.

It did ask for return to home, which is what I told it to do, before it disconnected. It appears that it didn't take, but I expected it to return home then or at least once the battery got low (another 12 minutes or so). I immediately ran uphill toward it trying to re-establish contact with it and the controller never reconnected even for a second.

I would hope they reach the same conclusion after the data analysis. Fingers crossed.

DroneFlying Posted at 2017-8-1 02:33
I was a few hundred feet above the surface of the water so I didn't think the built in protections like VPS would be an issue.

They shouldn't have been, but the combination of a bad VPS reading and you pulling back on the throttle caused it to start landing. The last reported location was here, which puts it over water, and since the winds were light I doubt it would have drifted much from that location on its way down.

What's odd to me is that I swam around there in a criss cross pattern the following afternoon, checking the sea floor for about 2 hours total. No sign of it. There are lots of boulders around there that would prevent it from drifting with the current, unless of course it broke up on impact or hit a rock or whatever. I would like to at least have something to present to DJI support or salvage my 128GB memory card. And if the final video saved to the card, that would be invaluable.

Dubwilcox Posted at 2017-8-1 03:08
What's odd to me is that I swam around there in a criss cross pattern the following afternoon, checking the sea floor for about 2 hours total. No sign of it. There are lots of boulders around there that would prevent it from drifting with the current, unless of course it broke up on impact or hit a rock or whatever. I would like to at least have something to present to DJI support or salvage my 128GB memory card. And if the final video saved to the card, that would be invaluable.

The part about RTH doesn't really surprise me because it would make sense that you can't initiate RTH during landing and unfortunately yours was stuck in landing mode. Technically it may have been possible to recover because it was still responding to the controls (though probably sluggishly) during the descent, but once it dropped below the hills and you lost the connection there wasn't much hope.

Yes, locating it would be preferable, but personally I think the log is enough to show that the VPS sensor reading is to blame for your loss. If you spend any more time looking for it I'd recommend starting in the location I pinpointed earlier and swim around from there in a circle with a gradually increasing radius.

DroneFlying Posted at 2017-8-1 03:19
The part about RTH doesn't really surprise me because it would make sense that you can't initiate RTH during landing and unfortunately yours was stuck in landing mode. Technically it may have been possible to recover because it was still responding to the controls (though probably sluggishly) during the descent, but once it dropped below the hills and you lost the connection there wasn't much hope.

Yes, locating it would be preferable, but personally I think the log is enough to show that the VPS sensor reading is to blame for your loss. If you spend any more time looking for it I'd recommend starting in the location I pinpointed earlier and swim around from there in a circle with a gradually increasing radius.

Thank you for your insight. I'll need to adapt the patterns of a robotic vacuum cleaner for best results.

Dubwilcox Posted at 2017-8-1 03:50
Thank you for your insight. I'll need to adapt the patterns of a robotic vacuum cleaner for best results.

I didn't know they work that way, but I was once trained as a rescue diver and that's how I was taught to locate things underwater.

A few questions to the experienced users.

What could the OP have done to :
a) avoid a situation of forced landing (maybe not pulling the left stick fully downwards?)
b) cancel a forced landing while there is still available signal

jpap Posted at 2017-8-1 04:14
A few questions to the experienced users.

What could the OP have done to :

What could the OP have done to :

a) avoid a situation of forced landing (maybe not pulling the left stick fully downwards?)

Actually the log doesn't show him pulling the throttle all the way back; he did pull back on it but not all the way, and even full throttle down / back shouldn't initiate a landing when the aircraft is 120m above the ground.

b) cancel a forced landing while there is still available signal

Yes, you can abort a landing with the throttle, at least in most firmware releases. There was one (.0500 or .0550 I think) where that wouldn't work, but there were a lot of complaints about it and that firmware release wasn't available long before it was superceded by one that restored the ability to use the throttle to abort landings.

I had a few times where the RC's LCD displayed showed "Connecting..." and all the data was frozen.
From what I could tell, it had to do with a bad USB connection to the mobile device, usually the cable itself was to blame.
This causes the RC to freeze and the aircraft to disconnect and initiate RTH.
I found out that in this case a short click on the RC's power button would unfreeze it and reconnect.
Surely it's a bug in the RC.

Did you go to the last home point that was set on the drone (take-off point by default) to look for it?

Dubwilcox Posted at 2017-7-31 20:21
I see that. I have never encountered a Forced Landing before. Should it have warned me on either the remote controller or the app? I know without a doubt that I was well above the hill because I could see the lights and the video showed a large distance between the surface and the camera.

It's difficult to make sense of any attempt to land being the reason for the loss, as the Aircraft Disconnected message appeared instantly, with no breakup of the video or signal like I've seen in the past when there are obstacles in the terrain.

I think you should have received a warning, check your warnings log under Go 4's General settings. I've only experienced these when trying to fly too close to a NFZ and am pretty sure I got warnings, though they may have been paired with NFZ messaging.

The forced landing was already underway for a full minute before your disconnection, starting as you approached the hill; a hill of rock would be a pretty good radio wave blocker, and it's not like you'd have had any trees to partially obstruct the signal before going down, so I'd expect the cutoff to be pretty abrupt.

I don't know how accurate these map/course projections are, but it sure looks to me like the last location was over a beach, even using the KML in Google Earth and resetting tilt to look straight down. Of course, once your signal was blocked, you might also have lost enough GPS locks to have slipped into ATTI mode and started to drift.

Sadly, the absense of light or signal, even when within line of sight, suggests a hard or wet landing.

EranR Posted at 2017-8-1 04:50
I had a few times where the RC's LCD displayed showed "Connecting..." and all the data was frozen.
From what I could tell, it had to do with a bad USB connection to the mobile device, usually the cable itself was to blame.
This causes the RC to freeze and the aircraft to disconnect and initiate RTH.

When I disconnect a USB cable from my phone, it lets me know in a pretty audible way, almost like a PC. The cable is fairly new and fits snugly on both ends, so I don't believe this was likely in my case. But that does sound like a frightening bug for sure.

Some friends were at the home point for 20-30 minutes after it disconnected and it never came back that way. And I'd like to think I would have seen or heard it trying to return home while on my way over to it, even if it only made it part way.

Dubwilcox Posted at 2017-8-1 11:45
When I disconnect a USB cable from my phone, it lets me know in a pretty audible way, almost like a PC. The cable is fairly new and fits snugly on both ends, so I don't believe this was likely in my case. But that does sound like a frightening bug for sure.

Some friends were at the home point for 20-30 minutes after it disconnected and it never came back that way. And I'd like to think I would have seen or heard it trying to return home while on my way over to it, even if it only made it part way.

Sorry for you loss.
I just though your case seemed similar to what I had a few times. In my case it ended well - aircraft reconnected once I clicked the RC's power button and I continued flying after canceling RTH.
However, the first time it happened, while it went into RTH it almost crashed into my house. It was terrifying.

EranR Posted at 2017-8-2 04:15
Sorry for you loss.
I just though your case seemed similar to what I had a few times. In my case it ended well - aircraft reconnected once I clicked the RC's power button and I continued flying after canceling RTH.
However, the first time it happened, while it went into RTH it almost crashed into my house. It was terrifying.

Yes, it does sound very similar.  I'm glad you didn't lose yours, but that must have been nerve-wracking. I'd had "Aircraft Disconnected" messages in the past, but usually the signal came back on its own and the numbers continued to update on the controller.

DroneFlying Posted at 2017-8-1 04:45
What could the OP have done to :

a) avoid a situation of forced landing (maybe not pulling the left stick fully downwards?)

How do you use the throttle to cancel a forced landing?

Rixxie33 Posted at 2017-8-3 13:26
How do you use the throttle to cancel a forced landing?

By pushing forward on it, at least in most versions of the firmware.

    Thank you

UPDATE:

I just received the following email from DJI Support one week later:

"We would like to request you to extract directly the flight record folder from your mobile device and extract the txt files.
The extracted flight record should be in "TXT" format and is usually named in default as "DJIFLIGHTRECORD_XXXXXXX" where "XXXXXX" is the incident date.

Please include the flight record with the matching incident date from flight record folder and reply to this email with it as an attachment so we will be able to proceed with the data analysis.

Also if you have recorded video during the flight incident, Please provide video at the accident for further analysis.

PLEASE FOLLOW THE INSTRUCTIONS PROVIDE IN THE ATTACHED FILE ON HOW TO EXTRACT IT.

Thank you for understanding and cooperation. Have a great day!

Regards,
Gerald
DJI Support"

I had previously synced the flight records as requested in the first response from them, but I am sending them the flight record as requested in the latest email. We'll see what they do with this additional information.

Keep us updated, interested to see where this goes.

Sorry for your loss