Hi All - Yesterday I few my mavic over a large marsh and then along the coast of a beach next to it.  I took off in high precision landing GPS mode (I think thats what it's called), and then flew fine for about 20 minutes.  I did get a high-wind warning, but my Mavic has always handled these fine.  At about 2700 ft away from take off point and at about 300ft alltitude, I had it to stop and hover.  Then it started moving backwards over the ocean.  I wasn't hitting the controller at all and attempts to move it forward to get back to land did not work at all.  It just started to fly itself out to sea.  After hitting RTH, it still kept on going on its own.  The only way I could regain control was to quickly dive down to lower altitude.  Then hit RTH and it started to come back.  It was sunset and the mavic was pointed directly into the sun.  Battery was getting low and it slowly limped back, abnormally slow.  But then it tried to land about 20 yards in front of me, which would of been in the water.  I then manually flew it back to myself and it got back with about 3% battery.  Any delay and it would of ended up under water.  I never got any error messages or lost the connection with the app.  I compass calibrated it before taking off.

Thoughts on what went wrong?

Two things might be happening here: either the forward vision sensors were confused by the sun (did you get the obstacle warnings?) or there was a way stronger wind. If it tried to move forward but it kept going backwards and by changing your altitude you could go back, I'd bet on the wind. In this situations you can always switch to sport mode to be able to push more power.

CuaC Posted at 2017-9-5 04:24
Two things might be happening here: either the forward vision sensors were confused by the sun (did you get the obstacle warnings?) or there was a way stronger wind. If it tried to move forward but it kept going backwards and by changing your altitude you could go back, I'd bet on the wind. In this situations you can always switch to sport mode to be able to push more power.

I would bet on this two points CuaC said, plus any issue with the positioning system , as you are flying over a water and it can cheat MAVIC!
Fotunately you were able to bring it back.
Cheers.

CuaC Posted at 2017-9-5 04:24
Two things might be happening here: either the forward vision sensors were confused by the sun (did you get the obstacle warnings?) or there was a way stronger wind. If it tried to move forward but it kept going backwards and by changing your altitude you could go back, I'd bet on the wind. In this situations you can always switch to sport mode to be able to push more power.

I never did get a forward collision warning.

Upload the logs.

Im thinking headwind.

Why did you calibrate the Mavic's compass?

Thoughts on what went wrong?

As gnirtS mentioned, wind is the simplest and most likely explanation but the only way we're going to be able to do more than speculate is for you to upload the log data. At a minimum you should be able to upload the TXT file from your mobile device to PhantomHelp using these instructions and then post a link to the log in this thread.

If you're running a version of firmware older than .1000 then the DAT file on the Mavic itself will have even more information, so if you want a more in-depth analysis please retrieve it using these instructions, upload it to DropBox, and provide a link here. The correct file will have a timestamp that corresponds to when the flight occurred and will be at least tens of megabytes in size.

Could you refer the below and export the main control data for analysis? It is similar with Phantom 4.

DroneFlying Posted at 2017-9-5 15:51
Thoughts on what went wrong?

As gnirtS mentioned, wind is the simplest and most likely explanation but the only way we're going to be able to do more than speculate is for you to upload the log data. At a minimum you should be able to upload the TXT file from your mobile device to PhantomHelp using these instructions and then post a link to the log in this thread.

If I still care when I get home, I'll upload the logs.  

Here are logs from my phone:  http://www.phantomhelp.com/LogViewer/1AXFY350XLQ4XTPRIIEJ/

I tried to find the .DAT file by connecting my mavic to my pc.  I couldn't find anything when I go into Flight Data.  I have the .1000 firmware release on the drone.  
As for logging, is it all on the phone?  Do I have to enable logging somewhere in the app to record flight data to the mavic itself?

I just found a DAT file in the folder on my phone where the logs are stored.  It corresponds to the time of the flight where I had the problem.  I put it up on google drive here:  DAT FILE from flight  Maybe this is the dat file with the fuller data you are looking for?

zoutv1 Posted at 2017-9-6 19:37
I just found a DAT file in the folder on my phone where the logs are stored.  It corresponds to the time of the flight where I had the problem.  I put it up on google drive here:  DAT FILE from flight  Maybe this is the dat file with the fuller data you are looking for?

It looks like you uploaded the TXT file rather than the DAT but that's fine, because it has enough information to figure out what happened.

The Cape Cod Coast Guard Air Station recorded winds winds out of the southwest at around 10 MPH at that time. However, that was a bit to your west and farther inland, and 10 MPH would have been the wind near ground level. Being so close to the water and at around 340 feet it's not surprising that the wind might have been too strong for your Mavic and would push it towards the ocean; winds at higher altitudes are often very different (usually stronger) than what you experience on the ground.

If at all possible you should plan your flight so that you have a tail wind on the return trip, but if you find yourself in that situation anyway the best thing to do is fly it back manually (without RTH) using Sport mode. Also keep in mind that winds are often stronger at higher altitudes, so if it's safe to do so you may be able to get it back without sport mode simply by reducing the drone's altitude. Anyway, I'm glad your Mavic survived the flight and hopefully now that you know why it happened it's something you won't have to experience again.