Hello everybody !
I have a sad story about the lost of my Mavic pro platinum. DJI didn't believe me and proposed me 30% off to get a new one.

I write you today because I lost my drone and I think it's because of a bug of the RTH. I would like to find a way to prove it was not my fault to have warranty care.

So I was flying 1200m far, with 70% of the batterie, 7m high, when I suddenly lost the video signal on the app. The RC was still connected so I pushed the RTH button. At that time the drone went up fast, to reach more than 300m high and didn't succeed to come back because of the high wind due to this altitude... It lost its battery very fast and finally land on the sea after 10 or 15 minutes... I'm very surprised of this sudden altitude it took. The RTH was set at 60m, I checked it before flying.
Could it be a bug ?
Is there some informations recorded on the RC which could help ?
DJI cannot explain what ghappene because the fly records stopped of course when I lost the video signal.

Regards
Benjamin

You may upload your flightrecord (located in a DJI subfolder on your mobile device) to this site and share the link with us: http://www.phantomhelp.com/LogViewer/Upload/
Maybe we can get an idea about what might have happened.

http://www.phantomhelp.com/LogViewer/JI9FGBH1ET35E02R0QQJ/

Thanks a lot for your help

Should be a message recorded in FlightLog file that says something like this:

Home Point Recorded. RTH Altitude:  60m.

UPDATE:  Did not find Home Point Recorded. or RTH Alitude: message in FlightLog

impossible, I lost video signal before doing the RTH. The RC was still connected but not the application

Benimav Posted at 2018-8-21 09:14
http://www.phantomhelp.com/LogViewer/JI9FGBH1ET35E02R0QQJ/

Thanks a lot for your help

(http://www.phantomhelp.com/LogViewer/JI9FGBH1ET35E02R0QQJ/)

From Verbose CSV file - HOME.goHomeHeight [m] = 60
In Excel it is Column ''GW''

Benimav Posted at 2018-8-21 09:36
impossible, I lost video signal before doing the RTH. The RC was still connected but not the application

The message should appear near time of takeoff.  Not after you hit RTH.

I just see "Home Point Updated"

Sorry for your loss.

Nothing to say!

Something is strange here.  The last entry on the log shows level altitude at 9.7 MPH with 59% battery, and then nothing.  Strong GPS, IMU is steady, battery is fine, then a switch gets turned off.  No error messages near the point of communication loss.  Typically you start seeing some abnormalities, but clearly it's like someone just hacked off part of the log within a clear and steady flight.  There is no record of the RTH being triggered by the OP.

A couple of notes just based on your post.  If you are in a situation like this, where you suddenly run into head winds and cannot return, absolutely get over land ASAP, and find a somewhat flat, secluded, and safe area to set the drone down.  Then obviously hightail it over there to retrieve it before someone takes it.

On the RTH altitude setting, always set it at least as high as the tallest obstacle around, plus a little cushion to be safe.  As you mentioned, the higher you go, often the stronger the winds, so in an environment like this, it's to your disadvantage to get needlessly high.

Thank you for your help.

I lost suddenly connection with the application. Maybe the bug come from the app ? The drone was still connected to the RC

Hi Benimav,

Sorry for you loss!!
Had a look into your flight.
HP has been recorderd, setting 60 meters.

In your flightlog there is no sign of a loss, so all the time you had or could have had control of your MP. Video loss as you said is not written in the log file, but ofcourse you had that loss. With a video loss the little compass in the goApp does function, possible to use this to bring the craft back home at a safe height.
RTH is not activated by you, mayby you pushed the RTH button on the controller to short. All the time your MP was in GPS mode.

Your max height was about 86 meters.

Flying that far at low altitude is always a risk, escpecially when you lost your video signal. Amazing that you could fly up and down again and stop at that low altitude.
Mayby at the end of your flight it hit something ? a boat near the coast?

At the end your MP had some compass errors.
A flightrecord keeps recording with a video loss, as you see in your log.

cheers
JJB

Yes, whatever it was, it was very abrupt but at that speed, you would think if it was above the water, it would have captured something with the motors for a split second or two.  It's as if it suddenly hit a monster wave and was just swallowed whole? Very strange.

This all just goes to show that even when things seem to be going well, and there are no obvious signs of trouble, whenever flying over water, you are taking a huge risk.  

BTW, nice program there JJB!

Yes that's very strange...

I talk about a video loss but it's more a app loss. The screen of the app was grey. As when the MP connection is lost but the RC was connected, I was able to see the distance, speed, height, battery...

I did a RTH because for me it was the fastest option..

At the end I tried to quit the application and connect it again. I think it was too late.

That area is very quiet, far from disturbance. I saw 2 big antennas on the beach. Maybe they suddenly sent high power communications..

And I was 7m above waves which was maximum 1m. I can upload the video if it can help you.

https://drive.google.com/file/d/1XblvZJvz2rcolR3uliwrhIdQy7MrMz0m/view?usp=drivesdk

Benimav Posted at 2018-8-21 11:18
Thank you for your help.

I lost suddenly connection with the application. Maybe the bug come from the app ? The drone was still connected to the RC

The pictures you took were it cached to device?
The time you lost video signal you had 100% signal to AC from RC so you just lost signal from RC to device.
Here under Notifications you can replay your flight with all warning and RC input.
Replay flight.

Exactly, it's the cached video.
Yes the RC was connected to the MP but the DJI go 4 was in grey (as when you turn off the MP)
Very nice website thank you.

I still not understand.. do you think it's just a bug of DJI go 4 and a lack of precautions I took ?

And how is it technically possible for the drone to RTH over 300m while I set it to 60m ?

This still is not making sense.  The max altitude in this last app shows 281.5 ft  NOT 300m and this occurs at 7m 53.9s.  At that time, the drone is completely under your control and the drone is following your stick input correctly.  At approx 7m 31, you can clearly see your left stick full forward, and the drone rapidly ascending from approx 26ft to the max logged, while you have the right stick back, and the drone is going backwards.  When you get to that max altitude, you suddenly move the right stick forward, and left stick down, and you begin a rapid descend.  Again, the drone is following your exact input and no where is RTH input received.   So I just don't understand why you keep saying that the drone ascend to 300m by itself under RTH.  The drone never got that high in the first place.  There was no confirmation of the RTH being activated.  And there is ZERO doubt the rapid ascend and descend was totally and exclusively following your joystick input exactly.  Further, the flight the entire time to the very last entry, the drone followed your input exactly.  

Benimav Posted at 2018-8-22 03:42
And how is it technically possible for the drone to RTH over 300m while I set it to 60m ?

Hi Benimav,

Your drone did not flew in a RTH mode! No signs in the flightlog that RTH was engaged.

cheers
JJB

Hello everybody

Thank you for trying to help me.

Of course RTH is not recorded on flight record : I lost connection between the RC and the application... Sorry if my messages are not clear.

I lost video signal on the application but the MP was still connected to the RC. So I pushed the RTH button and AT THAT TIME the drone fly up more than 300m.

But it was set to 60m.

I would like to know how is it possible. Because now DJI don't want to apply warranty...

As the OP has said, the app disconnected.  With the app disconnected and flying via RC only, we aren't getting the rest of the log file from the device.  Using the RC RTH, it should still come back even without the app, and that would not be in the log file.  With the MP,  we would be fortunate enough to still get telemetry on the controller, where he could see altitude and speed, despite it not reporting on the log, so I'm guessing the 300 meters was from the controller telemetry and will never appear in the log.  

It would make 0 sense that it would go to 300 meters, and unfortunately, without the rest of the log file,  I don't think DJI or anyone else can know what happened to determine fault.

Sorry about the issue....

Agreed, without the App running, there is no way the controller would know what the RTH altitude was set at.  And for that matter, if the RTH was actually activated properly or not.  Frankly, here's just no way to verify anything.

If after the events documented in the log, the OP was able to still monitor the flight in some manner on the RC, that suggests this was not an abrupt catastrophic collision, at least right adjacent to the end of the log we are viewing.  There is just no way to tell if it was a device issue, a RC issue, or if there was a battle going on with the OP vs the RTH.   And, whether there was a collision or not.  My best guess is, if indeed the OP saw 300m on the RC, which is almost 1,000 ft, it might have gone up that far, hit stronger winds, couldn't make progress home, and eventually ran out of battery and simply fell into the water.

What is surprising however is, the reception was strong.  I've had the app crash a couple of times for me mid-flight and the drone stopped, held steady, and I was able to restart and reconnect within a minute or less.  Makes no sense that he could not restart the app quickly and regain control?  Unless, he did not try and simply hit RTH, and the above scenario occurred.

Again, there is no way of telling what happened after the log event ends.  The only take away is, flying over water is an enormous risk, even under the very best conditions. This was a very long and risky flight and no doubt your card came up this day.  Sorry for your loss.  There not much more that can be said I'm afraid.

Does the BlackBox data on Remote Control have flight information that can be analyzed?

JJBspark Posted at 2018-8-22 07:15
Hi Benimav,

Your drone did not flew in a RTH mode! No signs in the flightlog that RTH was engaged.

Agree there are no signs in SmartDevice's FlightLog that RTH was engaged.

However, if SmartDevice quits communicating with Remote Controller (for whatever reason), engaging RTH on Remote Controller would not be recorded in SmartDevice's FlightLog.

Dirty Bird Posted at 2018-8-22 08:14
I've used RTH many hundreds of times & never once had it fly off into the stratosphere.  It always climbs to the set altitude then proceeds home.

The issue is, after the DJI Go 4 app disconnects, and the RC no longer can read the RTH altitude setting, what is the default programmed into the RC?  Might very well be 300m?  I have not ever test that scenario nor do I plan to.  Unfortunately, there is no log to show how much of this was a RC default and how much if any was user input.  Total mystery.

MrArcher Posted at 2018-8-22 08:05
Agreed, without the App running, there is no way the controller would know what the RTH altitude was set at.  And for that matter, if the RTH was actually activated properly or not.  Frankly, here's just no way to verify anything.

If after the events documented in the log, the OP was able to still monitor the flight in some manner on the RC, that suggests this was not an abrupt catastrophic collision, at least right adjacent to the end of the log we are viewing.  There is just no way to tell if it was a device issue, a RC issue, or if there was a battle going on with the OP vs the RTH.   And, whether there was a collision or not.  My best guess is, if indeed the OP saw 300m on the RC, which is almost 1,000 ft, it might have gone up that far, hit stronger winds, couldn't make progress home, and eventually ran out of battery and simply fell into the water.

I've had the app crash a couple of times for me mid-flight and the drone stopped, held steady, and I was able to restart and reconnect within a minute or less.


I ran into a case where GO-4 App suddenly quit communcating with Remote Controller.  Remote Control was still connected to drone.   Problem was restarting GO-4 App did not work.  Finally got GO-4 App working again by powering Off and On both CrystalSky and Remote Controller.   Took more than a few minutes to go from GO-4 App quit working to finally getting GO-4 App working with Remote Controller.


Powering Off and On the Remote Controller, did trigger drone's automatic Return to Home (at least something worked as expected).  By time CrystalSky OS was ready and GO-4 App running again and connected to Remote Controller, the drone was overhead and starting to land.


?? In cases like this, it seems it is worth trying:  ??

Along push on Remote Controller's RTH, to at least start drone home.
Quick stop and start of GO-4 App.  If that does not work...

Follow up with a complete power Off of both SmartDevice and Remote Controller (which should start drone home).

Quick check for loose USB cable between SmartDevice and Remote Controller.
Power On of both SmartDevice and Remote Controller, followed by starting GO-4 App.
If GO-4 does reconnect, check to see drone is making progress or fighting wind...

If Fighting wind, switch to Sport mode - try to fly drone to nearest dry land, possibly at lower altitude.

MrArcher Posted at 2018-8-22 08:50
The issue is, after the DJI Go 4 app disconnects, and the RC no longer can read the RTH altitude setting, what is the default programmed into the RC?  Might very well be 300m?  I have not ever test that scenario nor do I plan to.  Unfortunately, there is no log to show how much of this was a RC default and how much if any was user input.  Total mystery.

From my one experience, RTH altitude is not set in Remote Controller.  RTH altitude is stored in drone itself.

MrArcher Posted at 2018-8-22 08:05
Agreed, without the App running, there is no way the controller would know what the RTH altitude was set at.  And for that matter, if the RTH was actually activated properly or not.  Frankly, here's just no way to verify anything.

If after the events documented in the log, the OP was able to still monitor the flight in some manner on the RC, that suggests this was not an abrupt catastrophic collision, at least right adjacent to the end of the log we are viewing.  There is just no way to tell if it was a device issue, a RC issue, or if there was a battle going on with the OP vs the RTH.   And, whether there was a collision or not.  My best guess is, if indeed the OP saw 300m on the RC, which is almost 1,000 ft, it might have gone up that far, hit stronger winds, couldn't make progress home, and eventually ran out of battery and simply fell into the water.

App running or not don't affect RTH as that setting is stored in the AC not the RC or app.
The only time we have seen this is if RTH is direct in to low sunlight and all sensors are on.
It has happened that it think strong sunlight is obstacles and try to avoid these obstacles with more altitude .

MrArcher Posted at 2018-8-22 08:50
The issue is, after the DJI Go 4 app disconnects, and the RC no longer can read the RTH altitude setting, what is the default programmed into the RC?  Might very well be 300m?  I have not ever test that scenario nor do I plan to.  Unfortunately, there is no log to show how much of this was a RC default and how much if any was user input.  Total mystery.

Log will be recorded into black box on board aircraft, aircraft is programmed through app as to its RTH parameters.

Thank you for your work on my story ;)
I understand I took a lot of risks and I pay the price now.

But I still not understand why the RTH setting was not respected by the drone, that's still a big question. And that question is important because I am not sure to buy a new one if security like that are not efficient...

Thank you Gsig for your theory.
But if strong sun could be an obstacle I would have some notifications before, right ?

HedgeTrimmer Posted at 2018-8-22 08:30
Agree there are no signs in SmartDevice's FlightLog that RTH was engaged.

However, if SmartDevice quits communicating with Remote Controller (for whatever reason), engaging RTH on Remote Controller would not be recorded in SmartDevice's FlightLog.

Agree i think....But in this case only the video link had stopped. Drone followed All RC inputs and in the log all the Drone return values were recorded in the GoApp.

cheers
JJB

Well, seems we are starting to talk in circles.  The OP had confirmed he had the RTH set at 60m.  He also stated that after he lost the Go 4 app, and then hit RTH, the drone rocketed up to 300m.  We can see the Home Point was clearly set right after take off in very close proximity, so that entire piece is confirmed.  

Whether the default RTH is hard coded in the drone or RC, the question that's crucial to the discussion is, what is the default altitude?  If it's 300m, then what the OP is reporting makes sense. If not, then this adds another wrinkle.

That all said, if someone wants to do some tests to sort this out further, please do. Hedge, you seem to be suggesting that's a good idea.  I already opted myself out, so by all means, feel free to marshall on.  I'd love to hear what you find.  I've been able to recover from my couple of app crashes running 4.2.20 and was damn glad I did. However, I was in an open field within clear line of sight.

Imho, we've beat this to death.  This was a risky flight from the beginning, and this is exactly why it's always a bad idea to fly great distances over water, or in other wise treacherous areas. Stuff happens, and when it does, Mr. Murphy makes no exceptions.  In this case, it's impossible to tell exactly what happened, so we can post guesses for the next 6 months and not change a thing. Only value here is to extract a lesson or two.  Sad for the OP for sure.

Benimav Posted at 2018-8-22 10:12
Thank you Gsig for your theory.
But if strong sun could be an obstacle I would have some notifications before, right ?

If your app have lost connection you don't get any notifications from drone and it will turn to home.
At what time in the flight is the video taken?

Benimav Posted at 2018-8-22 07:26
Hello everybody

Thank you for trying to help me.

HI Benimav,

At 70% batt power you said you lost connection. But all data after that point is written in the file.
So or you are mistaken when it happend and the last record in the file is the moment you had your completely loss or you are wrong and only the video link was broken at 70% batt pwr.

You said you had speed, distance etc on the controller, that`s only possible if the drone is connected to the RC and able to sent data back. And as seen in the file that RC commands were followed by the MP....meaning data up and downstream were alive! So any activation for the RTH should be in the file, but no signs of that.  Did you had the RTH beeps all the time?

cheers
JJB

Benimav Posted at 2018-8-22 10:12
Thank you Gsig for your theory.
But if strong sun could be an obstacle I would have some notifications before, right ?

No.

Your app was disconnected before this so how would you be informed?

Do buy an other drone since you have 30% off but never ever fly that distance (1200 m.) at that height (9 m.)

Good luck.

I'm sorry it's a mistake, I lost application connection at the end of the record.

This is maybe more simple on my head than written...

I repeat :
I lost the application connection, the RC was still connected, I pushed RTH, the drone went up to 300m, met high wind, lost battery fast and land on the ocean.

My question is how is it possible to have a RTH so high while I set it to 60m ?

Records are useless because everything was fine until I lost application connection.