Experienced my first "fly away" today. I've logged 54 flights over the last couple months but never one like today. I was flying around a wooded area when all of a sudden my Mavic lost GPS signal and went into ATTI mode. As soon as it went into ATTI mode it was almost uncontrollable. It was a tough flight but I managed to get it back on the ground. Looking for a way to prevent this in the future becuase I was fairly confident until today.
I normally calibrate compass before flight but I did not do that today.


Flight Error Records:
Compass Error. Exit P-GPS mode. Ensure that there are no magnets or metal objects are near the compass. Note: The ground or wallas may contain metal. Change your location and try again.

GPSencouteresdata exception, please ask technical assistance for help.

Hi. What do You mean almost uncontrollable? Thanks

You should NOT calibrate every time you fly UNLESS the APP aske you to do it.

Loss of GPS is nothing new especially when you are in a wooded area.

Rule of thumb, stay in LOS., buy a cheap drone and practice in ATTI mode and again ALWAYS FLY IN LOS!

Good luck dude!

There's a DAT file stored on the Mavic for each flight that contains a great deal of information about what took place, and if you upload that we'll be in a better position to figure out what happened. The instructions for retrieving the file are here and once retrieved you'll need to upload the file to DropBox and provide a link to it in this thread. The correct file will have a timestamp that corresponds to when the flight occurred and will be at least tens of megabytes in size.

Why would a compass error disable GPS?
Orientation (compass data) and position (GPS data) are different but related.
When the Mavic is moving and getting position information from the GPS that tells the Mavic that it is travelling in a different direction from what it's getting from compass data, The Mavics programming can't work with the data conflict.
The solution is to drop data from one source and since the Mavic can't fly without a compass but can without GPS, it's the GPS data that gets dropped.

There have been some compass problems with Mavics  lately or your issue may have been related to something you did.
I'd be curious about when and where you calibrated it and where you launched from as these may be relevant factors.
You can also see the flight data to learn more and perhaps solve the mystery of your incident.

Why do you calibrate the compass of the Mavic before every flight?

If you could provide your flight data and flight log to the Support, they can submit a data analysis for this flight to check what happened. You can refer to the link below to contact the Support. http://www.dji.com/support

Im curious about this post. Earlier today i thought i learned that its good to calibrate once you firt open your brand bew mavic and also if you fly from place to place. I also saw a post that said dont mess with it unless it tells you to.

Glad i havent attempted a calibration yet. Im trusting that everythings fine since its flying fine so far.

Well having trouble getting the files out of my Mavic. I realized I did not have my SD card in at the time of flight.

Also something else I thought of....normally before I fly I manually shut down all apps, but did not do that before this flight.

I was flying at a friends house tonight, had 19 satellites and then they dropped and went into ATTI mode. Lucky there was not much wind and I was able to land safely and not in someones yard, but my heart was racing. Did a compass calibration before flight (as suggested by support)

Contacted support, they suggest refresh firmware and IMU calibration. Did that but I have to figure out this GPS problem.

DAT file: https://www.dropbox.com/s/ssirsuh8i5t4go9/FLY112.DAT?dl=0

el pelo Posted at 2017-8-10 18:34
I was flying at a friends house tonight, had 19 satellites and then they dropped and went into ATTI mode. Lucky there was not much wind and I was able to land safely and not in someones yard, but my heart was racing. Did a compass calibration before flight (as suggested by support)

Contacted support, they suggest refresh firmware and IMU calibration. Did that but I have to figure out this GPS problem.

The ATTI mode you experienced was preceded by the Mavic detecting errors with its speed (the thin strip of purple shading in the graph below) and position (pink shading). It was triggered by GPS health (the red plot) dropping from 5 to 0 and corresponded with you flying straight ahead at maximum speed (shown in green).

In a nutshell, what happened is that your Mavic determined that its GPS coordinates didn't match what it thought they should be given previous GPS data and the motion it detected / expected, and my guess is that you just need a good IMU calibration (see the video below). If the behavior persists after that then you probably should open up a case with DJI, but I suspect that won't be necessary.

As for calibrating the compass, I strongly recommend against doing that again until / unless you're prompted to by the app or you otherwise have good reason to believe it's needed. Good luck and please follow up to let us know how things turn out.

I did an IMU calibration, after it prompted for a compass calibration. Compass calibration failed twice but finally took on the third try. Flew it around the yard a bit and it encoutered a GPS error again this time going into OPTI mode. So strange that this just occurred out of nowhere 50 flights in?

I think it is fine to calibrate the compass every flight if you want to. As long as you do it correctly. Just waste a little time.

el pelo Posted at 2017-8-11 14:44
I did an IMU calibration, after it prompted for a compass calibration. Compass calibration failed twice but finally took on the third try. Flew it around the yard a bit and it encoutered a GPS error again this time going into OPTI mode. So strange that this just occurred out of nowhere 50 flights in?

it prompted for a compass calibration

Did it specifically ask you to do a compass calibration or was this the, "Magnetic interference; move aircraft or calibrate compass" message? In any case, if an IMU calibration didn't fix your original problem then I don't know what else to suggest but to open a case with DJI to get a warranty repair.

Glenn's correct that technically it's fine to calibrate the compass before each flight, but there's also no reason it should be necessary, and though it's apparently difficult to get a bad calibration there's no reason to risk it either and it isn't what DJI recommends.

el pelo Posted at 2017-8-11 14:44
I did an IMU calibration, after it prompted for a compass calibration. Compass calibration failed twice but finally took on the third try. Flew it around the yard a bit and it encoutered a GPS error again this time going into OPTI mode. So strange that this just occurred out of nowhere 50 flights in?

The one thing you can be assured of is if you calibrate a good compass it's impossible to make it better.

After I did the IMU calibration, the mavic prompted for me to do a compass calibration as well. I contacted support and they suggested a firmware refresh again.  

If it doesn't fly correctly I will have to send it in.