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Mavic Mini Looses control and fly away crash
767 30 12-3 01:47
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gwaja
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South Africa
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Third flight of new Mavic Mini. Flight starts out fine with GPS warning, but warning clears after a few seconds. When yawing at about 0:25 drone starts to loose altitude and controls behave in reverse. Video and connection to controller cuts out at 29secs in. Drone continues on path crashing into trees. Recovered in very bad shape about 2-300m from where it lost connection. You can see from flight logs that it thinks it is flying backwards. Flight logs uploaded.

Here is the video captured from device: https://youtu.be/CNQeuAabFiI

Flight logs uploaded to DJI, here is a video of replay: https://youtu.be/r_oot5_JwCg



I have returned the unit to dealer. There is no stock in the country so I won't be playing with this toy at Christmas

12-3 01:47
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Nebuchadnezzar
Captain
Flight distance : 1812037 ft
Spain
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sad to hear that mate ....
12-3 01:50
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Nebuchadnezzar
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Spain
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12-3 01:50
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InspektorGadjet
Second Officer
Flight distance : 102835 ft
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sorry to read that, hopefully somebody can show what happened.
12-3 02:46
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UweE
Second Officer
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Germany
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InspektorGadjet Posted at 12-3 02:46
sorry to read that, hopefully somebody can show what happened.

before loss of connection, the speed was 20m/sec = 72 km/h !
There was really a problem...
12-3 02:55
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UltraONE
lvl.4
Flight distance : 337999 ft
Russia
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Did it bother you that the drone didn't see any GPS satellites?
12-3 03:06
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Bright Spark
First Officer
Flight distance : 22129 ft
United Kingdom
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Speed reported @ 72 km/h.
Could it reach that speed in still air?
I guess that since as far as I know, speed is only derived from changes in gps  readings, and with  gps intermittent/lost , it could report any speed imaginable.
12-3 04:10
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davidms
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Flight distance : 81260 ft
Canada
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How many sats did you have when you lifted off?
12-3 04:41
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JJB*
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Bright Spark Posted at 12-3 04:10
Speed reported @ 72 km/h.
Could it reach that speed in still air?
I guess that since as far as I know, speed is only derived from changes in gps  readings, and with  gps intermittent/lost , it could report any speed imaginable.

Hiya,

Afaik speed is calculated from the inertia changes in the x and y axis., not from GPS readings.
Fly in your house with no GPS reception (OPTI mode) and notice that speed is still indicating.

If IMU gets the correct data and does a good calculation the result is equal to GPS speed calculation.
GPS data is almost always available; even in a forced into ATTI mode (due to other than gps errors) .When GPS speed and XY speed differs a lot than thats`s an indication of some errors in the drone. With errors the speed indication in the GoApp is not always correct.

cheers
JJB

cheers
JJB

12-3 05:31
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Bright Spark
First Officer
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Thanks for info. I gather airliners use inertia changes as one method of determining speed nd poition . No doubt those much more knowledgable than me will know.
Could it also be found by ground mapping?
I can't remember if tello gives speed - no gps anyway.
If a mm can do say 50 km/hr in still air, then to get 70  groundspeed on the clock it would be in a 20 kh tail wind.
But if it turns round, then ground speed becomes 30kh.,
implying inertial measurement can account for ( varying) windspeed.
Not saying it can't,  but find it interesting!
12-3 05:53
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DJI Stephen
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Hello and good day gwaja. I am sorry to read and to know what happened to your DJI Mavic Mini. Since this unfortunate incident happened. I would highly recommend to contact our DJI support team at https://www.dji.com/support?site=brandsite&from=nav for us to be able to assist you further with regards to this issue and to analyze what happened on that said flight.  We have the team who would do their best to find out the reason of the said incident and then the corresponding resolution would be provided. Again I am sorry and thank for your support.
12-3 07:39
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Knapweed
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JJB* Posted at 12-3 05:31
Hiya,

Afaik speed is calculated from the inertia changes in the x and y axis., not from GPS readings.

I'm not sure that's correct. Inertia changes only measure changes in acceleration, not speed. Imagine being in a plane flying at a constant 600 km/h. Providing there are no changes to acceleration/deceleration, there is nothing to affect the gyro meters. You certainly wouldn't get a reading of 600 km/h.
12-3 08:12
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Bright Spark
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This is interesting.
There must have been inertia reading when it accelerated to 600. So it would know the status quo and that speed.
And a constant headwind/tailwind  on take off would, and could also be accounted for.
Any susequent change in wind would give a reading too, albeit small.
I'm more or less guessing of course.
I believe these incredibly sensitive instruments are the last resort for navigation in the air when all else has failed!
12-3 08:34
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KlooGee
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Sorry to hear of your experience.  I also had a fly away where mine got up to about 65mph (104km/h) before it eventually recovered itself.

I'd be interested in checking out your logs to see if there is anything useful in there to help understand what happened.

Can you upload the flight record from your phone to the following site?  Directions are on the page, of course substitute DJI Fly in place of Go 4 in the directions.
12-3 08:50
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gwaja
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South Africa
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UltraONE Posted at 12-3 03:06
Did it bother you that the drone didn't see any GPS satellites?

I was doing a short line of sight flight. It didn't require GPS. In any case. It said 7 sats at take off, but the error cleared before I got over the water so I assumed all was ok. I think the little thing freaked out when it could not reconcile the GPS and IMU data.
12-3 09:15
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HedgeTrimmer
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United States
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At 0:25 when controls behaved in reverse, what did flight log show the controls doing?
12-3 10:12
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MegaTesla
lvl.2
Flight distance : 1224 ft
South Africa
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Sorry to hear about your incident.

My mavic mini flew away last Friday in Cape Town. DJI is still investigating it.

https://forum.dji.com/forum.php?mod=viewthread&tid=203267

12-3 10:55
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gwaja
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South Africa
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UweE Posted at 12-3 02:55
before loss of connection, the speed was 20m/sec = 72 km/h !
There was really a problem...

Conditions were perfect and there was almost no wind. Cannot confirm 72km/h, but when it decided to fly backwards at top speed it was going very fast.
12-3 10:56
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gwaja
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HedgeTrimmer Posted at 12-3 10:12
At 0:25 when controls behaved in reverse, what did flight log show the controls doing?

There is a video showing stick position. Controls show forward and up, it is going backwards hard and loosing altitude.
12-3 10:58
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JJB*
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gwaja Posted at 12-3 10:56
Conditions were perfect and there was almost no wind. Cannot confirm 72km/h, but when it decided to fly backwards at top speed it was going very fast.

if you like just upload your flightlog using > https://www.phantomhelp.com/LogViewer/Upload/

Log will probably tell what happend and what speed it reached.

cheers
JJB


12-3 13:05
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hallmark007
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gwaja Posted at 12-3 10:58
There is a video showing stick position. Controls show forward and up, it is going backwards hard and loosing altitude.

What setting for Remote sticks ?
12-3 15:11
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BobWinNV
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Bright Spark Posted at 12-3 04:10
Speed reported @ 72 km/h.
Could it reach that speed in still air?
I guess that since as far as I know, speed is only derived from changes in gps  readings, and with  gps intermittent/lost , it could report any speed imaginable.

I concur with your reasoning. It looks like a bogus speed calculation due to an anonymous GPS data point.
12-3 17:49
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kiminx
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sorry for that....
12-3 18:04
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HedgeTrimmer
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gwaja Posted at 12-3 10:58
There is a video showing stick position. Controls show forward and up, it is going backwards hard and loosing altitude.

Wondering if there is anything in drone's Log file around 0:25 that might give a clue as to why.
Phantomhelp provides a human readable version of log file in two forms; basic and additional.
DJI has way to look at far more.
12-3 19:02
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gwaja
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South Africa
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JJB* Posted at 12-3 13:05
if you like just upload your flightlog using > https://www.phantomhelp.com/LogViewer/Upload/

Log will probably tell what happend and what speed it reached.

Done: https://www.phantomhelp.com/LogViewer/FKSMCD07AWMBA3LYWS9Q
12-4 01:32
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JJB*
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Hi gwaja,

Wich RC mode do you use?

Yawing at 25 seconds is not seen in the flightlog, craft heading remains at approx. 221 degrees.
Yaw input starts at 14 secs (about 27% right max) upto 34 seconds. Guess your drone did actually yaws right but this is not seen in the log. Only the last few seconds in that period YAW heading is changing. If you flew a 180 turn right (guess you did so) than the mini still thinks that its heading 221.Ofcourse after that all goes wrong!

Flight started in OPTI mode, after 17 seconds in Cinematic mode.
There is no distance recorded in the file.
HomePoint has not been recorded, so satellite number and reception too weak for that.
Could have had impact on drone positioning too.

Not sure what happend, but start of the flight wasn`t oke. Why the heading data remains steady at 221 and not following your yawing; good question for DJI to answer.

EDIT see post #33   above is wrong as the OP did use mode2.
cheers
JJB

analysis1.png
12-4 03:12
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gwaja
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JJB* Posted at 12-4 03:12
Hi gwaja,

Wich RC mode do you use?

Mode 2. 00:25 is in the video footage (https://youtu.be/CNQeuAabFiI) where everything starts to go wrong. You can see for the first 20secs I am flying happily straight with no yaw on the sticks. Does your program tell when camera is started? I think it is somewhere around 12secs in the logs.
12-4 06:29
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JJB*
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gwaja Posted at 12-4 06:29
Mode 2. 00:25 is in the video footage () where everything starts to go wrong. You can see for the first 20secs I am flying happily straight with no yaw on the sticks. Does your program tell when camera is started? I think it is somewhere around 12secs in the logs.

Hi gwaja,

So my chart is wrong as i thought you didn`t use mode2.
Thanks to your video i spot the time in the log where is goes wrong.

Your started video at 11.4secs in flight, plus 20 seconds...i see now what imo happend; at this point VPS height stopped indicating, before that steady 3.3 meters.

Guess your were flying that low height in OPTI mode, not a GPS mode (8 sats + 3 for reception), curious to know what mode you see in the app, can you replay the flight in the FlyApp as in the GoApp ?
Once missing the VPS bottem sensor Mini cannot hold its ground reference, any RC input will speed up the Mini. (as in ATTI mode)In CineSmooth 100% fwd stick gives low speed, but 100% fwd stick in a non GPS mode gives full speed. (same for all 4 direction inputs)
Red thin line under the black flight mode line is the video recording line.

So starting to fly in OPTI mode wasn`t a good idea!

cheers
JJB
analysis1a.png
12-4 08:02
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gwaja
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JJB* Posted at 12-4 08:02
Hi gwaja,

So my chart is wrong as i thought you didn`t use mode2.

Here is the video of roughly what I saw on the controller. It started off with a GPS warning, but that cleared after getting out from under the trees and just said "In Flight". It was in cinematic mode which is effectively slow and steady mode.

Apart from the GPS warning at the start which cleared, there was no indication that anything was wrong until it started behaving badly, then comms cut off.

Also video cut off way before the crash which is weird.
12-4 13:24
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djiuser_Yf90lf4FnfaI
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This is my first drone.  My third test flight was today.  When I got above 50m it suddenly flew away and crashed into the trees.   I think it's the same error that's described here.   I have no idea how to check logs or what that data would mean anyway.  Any advice for a beginner? Thank you.
12-6 20:26
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JJB*
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djiuser_Yf90lf4FnfaI Posted at 12-6 20:26
This is my first drone.  My third test flight was today.  When I got above 50m it suddenly flew away and crashed into the trees.   I think it's the same error that's described here.   I have no idea how to check logs or what that data would mean anyway.  Any advice for a beginner? Thank you.

Hiya,

Post your flightlog here using this link > https://www.phantomhelp.com/LogViewer/Upload/

Best is to start your own new thread.

cheers
JJB
yesterday 02:38
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