Hi all,

I recently lost my brand new Mavic Mini.

Of course I'm quite disappointed, especially since I bought it just a couple of weeks ago. However, I'm mostly interested in what happened as I just don't understand how I lost it. I'll try to explain as best as I can.

I flew my MM in Norway on September 3th. It was a windy day, but nothing the MM couldn't handle: I had flown my MM for a total of 15 minutes on multiple flights that day (altitudes up to 22m) without any issues. In the early evening the wind died down somewhat and I decided to go for another flight. I switched to a charged battery and took off. I climbed to an altitude of about 14m and started the flight. After about half a minute though (at a distance of only 28m and an altitude of 14m), the MM seemed unresponsive and started going in the wrong direction. When I looked down at the controller, the video feed was frozen and grayed out. For some reason I had lost connection! At this moment I was completely unable to control the drone. I tried to regain control but could not. The MM started to move in the direction of the wind (away from me). I tried landing it (just anywhere would have been fine), but it did not respond to my inputs. At a certain point it dissapeared from my view and even though I tried following it by foot I could not keep up. I looked for hours but was unable to recover the drone.

I'm trying to learn from this experience, so I have some questions:

- Has anybody else seen a disconnect like this?
- Does anybody know what might have gone wrong?
- Why did the MM not maintain its position (even if the connection might have been lost)? The flight log seems to indicate the MM had locked onto 15 sattelites.
- Is it possible to upload a flight log to find out what happened?

Thanks in advance.

Hi Mobilae, I'm sorry for your loss, if the drone is still under warranty, please contact our support team www.dji.com/support to start a ticket for the data analysis, we will help to check what happened and provide the proper resolution.

Hiya,

best to get some help here is to upload your flightlog, use this link >https://www.phantomhelp.com/LogViewer/Upload/

Post the upload link on here.

cheers
JJB

Hi,

Thanks for your response. Here is the upload link:

https://www.phantomhelp.com/LogViewer/3YG90ROUZ9AZZG9LK6XD

The weird thing is that the flight just seems to stop mid-air. I guess that's when the MM disconnected.

After about half a minute though (at a distance of only 28m and an altitude of 14m), the MM seemed unresponsive and started going in the wrong direction.
Flying SE at full speed at 14 metres altitude, the Mini could only achieve up to 2.8 metres/sec.
This indicates the wind component from the SE was blowing at at least 5 m/s.

At 0:36.8 you switched to Sport Mode and tried to fly SE at full speed.
Rather than flying to the SE, the drone went backwards at up to 6 m/s.
This is puzzling as it suggests that the wind was now gusting at around 20 m/s.
The drone was responding to your joystick control inputs.

Having such a strong wind change seems unlikely, but I can't see any extra clues in the data for an alternative explanation.
Whatever happened after 0:54.6 is a mystery because without signal, the app couldn't record any more data.
On losing signal, the Mini would have climbed to your set RTH height and attempted to RTH.
If the wind was >8 m/s from the SE, the drone would have continued being blown backwards.

I’m sorry for your loss. Labroides’ explanation seems correct, but that could be as he’s much more skilled than me!

Mobilae Posted at 9-16 02:19
Hi,

Thanks for your response. Here is the upload link:

Hi Mobilae,

in the log at start with 2 compass errors ; " Compass error. Ensure there are no metal or magnetic objects near the aircraft and calibrate it before use.(Code: 30060).

Fly direction after 15 seconds heading approx 133, with full forward stick only speed of 1.6 m/s.
In N mode 8 m/s is normal, with too much wind on the nose this will reduce to....in your case 1.6.

At 34 seconds  no  speed, after that craft drifing backwards.
Now in Sport mode, but still with 100% fwd stick   backwards drifing away.

At the end yaw input but craft direction towards home was oke, now 90 degree offset.

So even at low height the wind was too much for your MM.

If you like put a link on here to your DAT file [ FLY013.DAT, on your mob device : MCDatFlightrecords map], in the DAT more info about wind and compass data.

Mayby, if the compass data is wrong then it is difficult to analyse data in the log .  Do you remember wich heading you started to fly away from the homepoint?According to the data ; 280 heading after takeoff, after 15 secs 133.   correct?

cheersJJB

Thank you for your replies.

So did I just miss those calibration errors? They don't show up when I replay the flight in the DJI app. Also, could they have caused the strange behavior?

I just don't understand why it disconnected so suddenly. Could this have anything to do with the above?

As Labroides states, a sudden wind change of that magnitude seems somewhat unlikely. Yes, there was wind. But not THAT much wind. Also, wouldn't it have shown a wind warning?

@JJB: Yes, those initial headings are correct. I had full control until about 30 seconds into the flight.

I'll try to get the DAT file up as soon as I can.

Did you ever calibrate your compassions when you first flew it?
I have seen these flyaway reports before with the compass doing a 180 degree flip.

Mobilae Posted at 9-16 05:23
Thank you for your replies.

So did I just miss those calibration errors? They don't show up when I replay the flight in the DJI app. Also, could they have caused the strange behavior?

I had full control until about 30 seconds into the flight.
The data suggests that you had full control for as long as there was data.
You pulled the left stick down and the drone descended, you pushed the left stick to the side and the drone rotated.
The only control problem was that the drone wouldn't make headway against the wind.

Yes, I had calibrated the compass(es) multiple times before.

@Labroides: If that's the case, the 'loss of control' is completely my own fault (for not taking into account the wind well enough). Again, I'm trying to learn from this event so something like this will not happen to me again.

What I just don't understand is, if I was indeed flying into the wind at full power (and still going backwards), why there was there no wind warning?

And why did it disconnect so abruptly?

Mobilae Posted at 9-16 05:23
Thank you for your replies.

So did I just miss those calibration errors? They don't show up when I replay the flight in the DJI app. Also, could they have caused the strange behavior?

Oke, compass values oke at the beginning of the flight, but through the whole flight??
Looking forward to see the DAT and compass data.

But your log shows weird data;
if you drone was fighting the wind on the nose, with 100 forward stick, and it did drift backwards, as seen in the log.
But at some point 100% fwd stick was reduced to zero, effect should be more drifing backwards!
Uh, not in your flightlog.  see my chart.  #3 shows forward stick, top red show speed.
stick to zero and speed reduces....cannot be true.

If compass is flipped 180 degrees than it would make more sense what happend...

You must have missed the 2 compass errors, that`s why i alway fly with a screen recorder active.
So i can see what i have missed watching the drone and not the app screen.

All flight heading was SE, only the last right yaw input turned the hdg to 210  (approx), well if compass data is oke....
cheers
JJB

JJB* Posted at 9-16 06:51
Oke, compass values oke at the beginning of the flight, but through the whole flight??
Looking forward to see the DAT and compass data.

[Image]

Again and again and again:
your analyzes are so detailed and informative, it couldn't be better!  
Thank you!

frankymusik Posted at 9-16 09:19
Again and again and again:
your analyzes are so detailed and informative, it couldn't be better!  
Thank you!

Spot on!!!

JJB* Posted at 9-16 06:51
Oke, compass values oke at the beginning of the flight, but through the whole flight??
Looking forward to see the DAT and compass data.

Thank you for your detailed analysis! Very helpful.

Strangely enough, there are only 4 DAT files in the MCDatFlightRecords folder. FLY008, FLY009, FLY010 and FLY012. There are however 22 flight records in the FlightRecord folder. Is that normal?

Mobilae Posted at 9-18 03:22
Thank you for your detailed analysis! Very helpful.

Strangely enough, there are only 4 DAT files in the MCDatFlightRecords folder. FLY008, FLY009, FLY010 and FLY012. There are however 22 flight records in the FlightRecord folder. Is that normal?

Hi,

Not sure, but sometimes DAT files are removed when sycing with DJI.
Plus; flights start and stopped by stopping rotors and starting again (without powering down) are saved in the same DAT file.
I always download my logs and dats after day flying on my pc, before sync with DJI.

So no FLY013.DAT, too bad.

cheers
JJB