Lost Mavic

jamesCrombie said:

Hi All,

thank you for reading this. Was taking a photo tonight with the Mavic Mini and it took off and I couldn't control it. I quickly hit return to home but it kept flying further away. I went analysed the flight and the find my drone is showing me a location but i searched there and could not find it. If i have the log file is it possible to get the GPS location it eventually landed. It was very embarrassing i was photographing a local football team working as a group on community work for people who cant. Now they all want to come help me find it in the morning (mortified)

Click to expand...

Hi there & welcome to the forum ... sorry about your loss.

If the Mini still was airborne & you lost the connection to it before it hit ground the position in your app is most likely not where it touched down ...

Start with attaching the .TXT log from your mobile device you flew with in a new post here... read up here on how to retrieve the log --> Mavic Flight Log Retrieval and Analysis Guide (read under section 3.)

Looks like it got caught in the same winds that were up north here today too, blooming fierce. Have a look at DJI Flight Log Viewer - PhantomHelp.com and you can see your course.

What did you have the loss of signal action set to? Unless descend then at a guess it kept on flying until it ran out of power but others, far more able than me, may have a look at the other logs and be able to tell you.

jamesCrombie said:

Hi All,

thank you for reading this. Was taking a photo tonight with the Mavic Mini and it took off and I couldn't control it. I quickly hit return to home but it kept flying further away. I went analysed the flight and the find my drone is showing me a location but i searched there and could not find it. If i have the log file is it possible to get the GPS location it eventually landed. It was very embarrassing i was photographing a local football team working as a group on community work for people who cant. Now they all want to come help me find it in the morning (mortified)

Click to expand...

Unfortunately it's not going to be anywhere near the last recorded position, because it had 67% battery left when it lost connection for the final time. It will have drifted a considerable distance before smart battery autoland kicked in. So this is a bit of a long shot - on the plus side the drift rate and wind direction were fairly consistent, but on the minus side even small variations over that time and distance lead to a pretty big uncertainty.

Extrapolating the battery depletion rate to the autoland level and then extrapolating the aircraft position out to that time gives the following:



The RTH-mode motor thrust direction was around -111°, and the drift was at around 73°. If we narrow the drift course to around ± 1.5° to get a tractable result then the estimated landing location plots as follows:



Even with those rather generous assumptions we have an estimated uncertainty of at least 150 m, represented by the green circle.



Maybe worth a look in that area though.

EDIT: Failsafe was set to "Hover", so this calculation is completely wrong.

EDIT#2: Hover makes no difference, of course, it still drifts just the same. That location holds.

jamesCrombie said:

Thanks for the reply, i am not sure what it was set to?? i didnt change the defaults. Hopefully someone might be able to help.. it has been acting funny the last few flys... was hoping to speak to DJI support but could not get hold of them this morning

Click to expand...

Actually you had failsafe set to "Hover", so disregard my previous post. I'll redo the estimate - it will be much closer.



EDIT: Of course this makes no difference - it would only have mattered if you had it set to "Land" as the failsafe action.

I'm clearly having a bad afternoon - hover and RTH are effectively the same if it is drifting on the wind. The solution in post #8 is correct - at least as correct as I can make it.

jamesCrombie said:

Thanks again... thats going to be hard to find. Private land over there not sure if i will even get access but must try in the morning. Any idea why it would have taken off like that and not tried to return to home. Was it just the wind... it was holding over what i was trying to photograph and then it just took off!!

Click to expand...

Actually it was not just the wind - that was around 12 mph out of the west. Unfortunately it was suffering from the rear props issue that prevents it from achieving adequate forward pitch - the same issue that causes the uncommanded descent problem. As you can see from the attitude data it was unable to achieve much more than around -10° of pitch at the end as it was attempting to return - that's well below spec.



This is now a well-documented and fairly common problem - and while DJI is staying very quiet about it they have replaced a number of Minis lost due to this problem. If you pursue them you will need to make the technical case with these data.

More information in the thread below:


Also documented in a number of other threads:

sar104 said:

I'm clearly having a bad afternoon - hover and RTH are effectively the same if it is drifting on the wind. The solution in post #8 is correct - at least as correct as I can make it.

Click to expand...

Ha, ha ... ? , yeah that one nearly fooled me also but saw the truth eventually also.

I wasn't so generous as you @sar104 ... took those max & min values from both the tiltdirection & drift speed and ended up at about the same distance as you but a tad more to the north. But with those amount of battery % left & in that wind every tiny change in speed or direction make a huge area to search off.

So if nothing is found in sar104's area ... below you have another red marked area.

jamesCrombie said:

I was thinking it was acting funny, I have the DJI insurance so hopefully that will help. Will also search that area in the morning. There were wind turbines it would have to avoid on route so i am a little concerned about that. They were well away from where i was but by your map it had to navigate 6 of them. Thank you so much for all the replies... I didn't release the drone would keep going after i lost contact. I was sure it would try land as a fail safe!!!

Click to expand...

Oh yes - I didn't notice those. The predicted path is close to a couple of them and directly on line with the last one. They appear to be 80 m tall with 40 m blades, so with the aircraft at around 50 m AGL through that location that certainly brings them into play.

jamesCrombie said:

I was thinking it was acting funny, I have the DJI insurance so hopefully that will help. Will also search that area in the morning. There were wind turbines it would have to avoid on route so i am a little concerned about that. They were well away from where i was but by your map it had to navigate 6 of them. Thank you so much for all the replies... I didn't release the drone would keep going after i lost contact. I was sure it would try land as a fail safe!!!

Click to expand...

It would have tried to land as a failsafe action ... if you had set it for that, unfortunately you had it set for hover.

If it's suffering from the dreaded uncommanded descent, could it not start to loose altitude and crash landed way before the battery reached critical?

RayOZ said:

If it's suffering from the dreaded uncommanded descent, could it not start to loose altitude and crash landed way before the battery reached critical?

Click to expand...

It was struggling to hold pitch, but showing no sign of descent problems. Whether it ended up descending prematurely after the log ends is unknown, of course.

If the wind has died down do you know anyone with another drone that might be able to do an aerial search?