I LOST MY DRONE ! ?

[Meta4]

Correct me for any mistake in the following:
-No .TXT file in the DJI FlightRecord folder in my Android phone.
-Found 2021-07-31_13-23-00_FLY076.DAT log file.
-Used DatCon to process the file, and got 4 files (2 files .TXT / .KML / .CSV )
Thanks

It looks like it's going to take another week before you can follow the instructions and provide the .txt file, so I'll do something I don't normally do and make an educated guess without the data.

You lost GPS which leaves the drone in atti mode, without horizontal position holding ability.
In atti mode it will be blown around by any wind.
It cannot RTH without GPS, but it's still completely controllable.
If you don't fly it back, it will just be blown away.

That's what happened to your drone.
It sounds like you just let it be blown away.
The loss of GPS is either due to a rare hardware failure or possibly something nearby is interfering with GPS signal.
That is rare but I saw a case in Lebanon reported recently.

 

[Rashad]

It looks like it's going to take another week before you can follow the instructions and provide the .txt file, so I'll do something I don't normally do and make an educated guess without the data.

You lost GPS which leaves the drone in atti mode, without horizontal position holding ability.
In atti mode it will be blown around by any wind.
It cannot RTH without GPS, but it's still completely controllable.
If you don't fly it back, it will just be blown away.

That's what happened to your drone.
It sounds like you just let it be blown away.
The loss of GPS is either due to a rare hardware failure or possibly something nearby is interfering with GPS signal.
That is rare but I saw a case in Lebanon reported recently.

DJI Flight Log Viewer | Phantom Help

Upload and view DJI Phantom, Mavic, and Spark flight logs online

www.phantomhelp.com

 

[Meta4]

DJI Flight Log Viewer | Phantom Help

Upload and view DJI Phantom, Mavic, and Spark flight logs online

www.phantomhelp.com

That's what I needed.
It shows that my educated guess above was correct,

You started with good GPS reception and were able to record a homepoint.
At 7.5 seconds your satellite numbers started dropping rapidly.
At 7.7 sec the drone had insufficient satellites to have good location data and was now using the VPS sensors to provide horizontal position holding (Opti-Mode).
At 23 seconds you had climbed higher than the range of the VPS sensors and now the drone could not resist the wind.
But it was still completely controllable.
You flew a little but at 53.6 sec you stopped and left the drone to hover until 84.4 sec, when you started to give it more joystick input.
But unfortunately you didn't turn the drone around and fly it back to where you were.

At 159.8 seconds the drone lost signal and continued to drift with the wind until it reached low battery level (maybe 20 minutes later).
And then it would have auto landed.

 

[wardtom084]

And I would think the landing lat/long would be recorded on Air Data

 

[Meta4]

And I would think the landing lat/long would be recorded on Air Data

It isn't.
The drone lost signal and kept drifting further away so there's no way Airdata could have any record of what happened after the recorded flight data ran out 159.8 seconds.
And ... the drone had no GPS location data to tell where it was.

 

[slup]

...At 7.7 sec the drone had insufficient satellites to have good location data and was now using the VPS sensors
...At 23 seconds you had climbed higher than the range of the VPS sensors

At 159.8 seconds the drone lost signal and continued to drift with the wind until it reached low battery level (maybe 20 minutes later).
And then it would have auto landed.

The conclusion isn't entirely correct ... by having lost the satellite location & then also ascending above VPS coverage would mean that the AC goes to ATTI mode.

When a DJI drone loses the RC connection when it's in ATTI mode it auto lands immediately ... no drifting with the wind until the battery runs low will occur.

If the OP had VLOS of the AC when he lost the connection it would have touched down slightly down wind from there.

 

[Rashad]

That's what I needed.
It shows that my educated guess above was correct,

You started with good GPS reception and were able to record a homepoint.
At 7.5 seconds your satellite numbers started dropping rapidly.
At 7.7 sec the drone had insufficient satellites to have good location data and was now using the VPS sensors to provide horizontal position holding (Opti-Mode).
At 23 seconds you had climbed higher than the range of the VPS sensors and now the drone could not resist the wind.
But it was still completely controllable.
You flew a little but at 53.6 sec you stopped and left the drone to hover until 84.4 sec, when you started to give it more joystick input.
But unfortunately you didn't turn the drone around and fly it back to where you were.

At 159.8 seconds the drone lost signal and continued to drift with the wind until it reached low battery level (maybe 20 minutes later).
And then it would have auto landed.

Thank you for the explanation...much appreciated.

In fact the drone did drift with the wind, very fast, and i lost sight of it in seconds.

THEORATICALLY speaking, knowing the last altitude of the drone the moment the connection was lost, and the drifting direction, would it be possible to "simulate" the flight course ? The area there is surrounded by hills and the drifting direction should lead to a much higher altitude hill, what would happen when the drone reaches that hill ?

 

[slup]

... In fact the drone did drift with the wind, very fast, and i lost sight of it in seconds.

It only drifted for a short while ... then it started to land.
Below from the manual ...


To get some idea how long that "...for a while" could be, maybe it's around those 11sec it takes for the failsafe RTH to kick in if the RC connection is lost while having GPS lock.

THEORATICALLY speaking, knowing the last altitude of the drone the moment the connection was lost, and the drifting direction, would it be possible to "simulate" the flight course ? The area there is surrounded by hills and the drifting direction should lead to a much higher altitude hill, what would happen when the drone reaches that hill ?

It is possible to take out a drift direction you could use with an ordinary hand held compass & start out walking in that direction from a known GPS position. But as you continued to maneuver the AC after it got ATTI mode with both Aileron, Elevator & Rudder stick the final position where you lost the connection is totally different then the last GPS position recorded in the log.

The AC tilt direction was approx. -20 degrees from North where you stood and hovered just before your AC entered ATTI mode ... meaning it would have later drifted for a short while (maybe 11sec) in the compass direction +160 degrees from North before starting to land. If you had your eyes on the AC when you lost the connection you could go there & start to search in the direction mentioned above.

 

[Rashad]

It only drifted for a short while ... then it started to land.
Below from the manual ...

View attachment 133052
To get some idea how long that "...for a while" could be, maybe it's around those 11sec it takes for the failsafe RTH to kick in if the RC connection is lost while having GPS lock.

View attachment 133053


It is possible to take out a drift direction you could use with an ordinary hand held compass & start out walking in that direction from a known GPS position. But as you continued to maneuver the AC after it got ATTI mode with both Aileron, Elevator & Rudder stick the final position where you lost the connection is totally different then the last GPS position recorded in the log.

The AC tilt direction was approx. -20 degrees from North where you stood and hovered just before your AC entered ATTI mode ... meaning it would have later drifted for a short while (maybe 11sec) in the compass direction +160 degrees from North before starting to land. If you had your eyes on the AC when you lost the connection you could go there & start to search in the direction mentioned above.

Thank a lot...I guess i'm gonna have a searching / hiking day tomorrow

 

[Baron von Richthofen]

Tell us how you get on. Good luck!

 

[MS Coast]

ATTI mode (message "Signal GPS lost") together with what the OP said about losing the connection soon after ... would have initiated a forced auto landing, that's how DJI drones are programmed.

On the Air 2S (and others?) the user can specify the action after a lost signal - hover, land, RTH.

 

[slup]

On the Air 2S (and others?) the user can specify the action after a lost signal - hover, land, RTH.

Right ... but all that goes out the window if the AC is in ATTI mode.

If you think logical about it for a sec ... In ATTI no GPS position exists meaning RTH isn't possible, the AC doesn't know how it's positioned relative the HP & can't command a flight direction to go there. And letting the AC hover in a situation where no horizontal hold exist isn't the wisest strategy ... the AC would just drift away with the wind until it crashes into something or runs out of battery.

So it's only one thing that is logical in a situation where a AC in ATTI mode loses the RC connection ... that is force landing, that's why DJI have coded the SW in that way.

 

[Meta4]

On the Air 2S (and others?) the user can specify the action after a lost signal - hover, land, RTH.

And almost no-one ever changes that from the default setting which is RTH, because it's very rare that you would ever want it to be anything other than RTH.

 

[Rashad]

Good day,

Today's search for the lost drone was successful... I followed the coordinates suggested in above message (Thanks @slup for that) and quickly found the drone, but unfortunately crashed !

Attached .GPX coordinates where i found it (zipped so i can attach it), as well as photos of the damages.

I would like your advice whether the damages can be repaired (worth ?)

Is it possible (useful ?) to retrieve the flight log from the drone for analysis ?

Thank you

 

[ninja_geezer]

Good day,

Today's search for the lost drone was successful... I followed the coordinates suggested in above message (Thanks @slup for that) and quickly found the drone, but unfortunately crashed !

Attached .GPX coordinates where i found it (zipped so i can attach it), as well as photos of the damages.

I would like your advice whether the damages can be repaired (worth ?)

Is it possible (useful ?) to retrieve the flight log from the drone for analysis ?

Thank you

wow that has had some impact ,,defo did not land that's for sure .

 

[slup]

...Is it possible (useful ?) to retrieve the flight log from the drone for analysis ?

Thank you

Nice that you found it ... just a pity regarding the damage. Unfortunately the AC log can only be read by DJI staff, it's encrypted.

wow that has had some impact ,,defo did not land that's for sure .

Yes it did ... but as it was in ATTI mode it was also drifting horizontally with the wind, meaning no gentle landing.

 

[ninja_geezer]

Nice that you found it ... just a pity regarding the damage. Unfortunately the AC log can only be read by DJI staff, it's encrypted.


Yes it did ... but as it was in ATTI mode it was also drifting horizontally with the wind, meaning no gentle landing.

yes its a massive crash ......landing shame looks like its had it ..?

 

[Rashad]

wow that has had some impact ,,defo did not land that's for sure .

some impact indeed...
I wonder why the back sensor did not stop the drone when it approached the rock (found near a rock), maybe it was drifted fast by the wind

 

[ninja_geezer]

some impact indeed...
I wonder why the back sensor did not stop the drone when it approached the rock (found near a rock), maybe it was drifted fast by the wind

looks like its been hit with a baseball bat.....

 

[slup]

...I wonder why the back sensor did not stop the drone when it approached the rock...

The OD sensors will not work in ATTI mode ... and that damage is possible, try it yourself, walk/run face first into a solid rock wall with ... let's say 3m/s (light wind speed) ... it will hurt really bad.