Mavic Mini Crashed into the water (video and flight log included)

[SalvaCG]

Hello,

I bought a Mavic Mini one year ago, and until now I had no issues and was so happy with its performance, but the other day I just lost control of it while flying and it crashed into the water.

I don't know what happened, it was flying like always and then suddenly it started losing altitude, and I couldn't do anything, the controls were unresponsive, and it just fell in the water. I was lucky enough to be able to recover it, and to my surprise it still works! After that I have been using it and it seems fine, but I am worried that that could happen again, and instead of crashing into the water could just crash into a person or a car or cause an accident... Any ideas of what could have happened??

Here's a video of the exact moment it crashed, and also the flight record:

DJI Flight Log Viewer | Phantom Help

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Thank you!

 

[AZDave]

The video is interesting. The drone stops, turns, and descends exactly as if it thought the home point had been updated over the water and it had been told to land (or RTH).

I have a Mavic Air 2 and on a recent occasion was flying normally (and manually) about 30 feet above the ground with no nearby obstructions when all of a sudden the DJI Fly app announced "landing" and it started to descend. The drone was less than 200 feet from where I was standing with the controller. I quickly pushed the left stick forward to override and gain altitude, and the rest of the flight was fine. I was just cruising in Tripod mode and holding the sticks in a fixed position ... no turns, no altitude changes, and a slow steady speed. I've seen a couple of other reports about the latest DJI Fly app randomly initiating a landing on its own, but I honestly don't know whether that is actually true even in my case.

 

[Meta4]

I don't know what happened, it was flying like always and then suddenly it started losing altitude, and I couldn't do anything, the controls were unresponsive, and it just fell in the water.

Here's what that flight data looks like:

DJI Flight Log Viewer | Phantom Help

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The first thing I noticed in the data was that the file date in the flight data is 2nd February ??
I'm not sure how that happened.

Your Mini was behaving normally until 3:39.3 when it was hovering and started to descend without any corresponding joystick input.
It was at an indicated height of 17 ft and when it dropped to 9 ft, you pushed the right joystick forward to make it go forward, but there is no record to show you doing anything to make it climb.

The drone was 10 ft above the water at this time.
It picked up forward speed, but kept descending into the water.

Early in the life of the Mavic Mini, they had a problem with uncommanded descending.
This was fixed with firmware update 1.0.5.
I can't tell if yours was using later firmware, but if it was earlier firmware, that could be the cause of the incident.

 

[slup]

Yeah ... this have most of the typical ingredients from a "Uncommanded descent" incident.

The Mini shows a very slow & unstable behavior ... it really never reaches the specified spec for max tilt angle of 20 degrees (P mode) ... meaning that top speed for that mode only is reached occasionally & that only after applying full right stick forward for a very long time.

Here below a only full right stick forward command (the purple graph) that lasts for 13sec. Note how bad the tilt angle (green graph) is ... on average around 11 degrees. The tilt consists of only pitch (blue graph). A top heading speed in line with the spec for a Mini is barely reached just in the end of the command. And don't think the mediocre pitch have any thing to do with flying with the wind... the logged wind direction, wind speed & the fact that the Mini have a hard time to reach heading speed talk against that (wind info in the end of the post).



This bad behavior most probably originate from that the rear props can't produce enough thrust ... as they have been deformed (flattened) during storage. The flight controller tries to rise the RPM for the bad performing props to compensate ... but once on max RPM the Mini can't tilt or reach specified speeds anymore & if this prop thrust problem grows during flight the thrust generated can't keep the Mini in the air anymore.

Locking at the height stability during this flight also shows a lot of smaller uncommanded ascents/descents ... have in below chart circled them in red. The green graph is the vertical speed (0 is neutral & positive = descent, negative = ascent) and the purple is your throttle commands. If all healthy ... the two graphs should go in opposite direction or stay neutral (value 0 for the speed & 1024 for the throttle).

In the end of the chart you can see the big uncommanded vertical speed increase in positive direction with neutral throttle ... and the result is shown by the red height graph.



If you still have the mobile device .DAT log from this flight ... it would be easy to confirm how the rear motors performed there in the end. The .DAT logs are in the same place as the .TXT log you have shared but in a sub folder called MCDatFlightRecords. The correct .DAT log ends with FLY084.DAT, retrieve it and attach it in a new post here.

Wind information from the flight ...

 

[SalvaCG]

Hello,

Thank you for the super detailed and interesting analysis of the log. Sadly I can´t find the DAT file inside the folder MCDatFlightRecords. Actually that folder is empty. I just read in the DJI forum that other users are having this same issue because they have Autosync enabled in the DJI Fly app, which deletes the DAT files from the mobile device.

So what do you think I should do? Since we can´t check how the rear motors performed, should I replace the rear props with new ones?

 

[slup]

Hello,

Thank you for the super detailed and interesting analysis of the log. Sadly I can´t find the DAT file inside the folder MCDatFlightRecords. Actually that folder is empty. I just read in the DJI forum that other users are having this same issue because they have Autosync enabled in the DJI Fly app, which deletes the DAT files from the mobile device.

So what do you think I should do? Since we can´t check how the rear motors performed, should I replace the rear props with new ones?

Yep, replace all props & update both the craft firmware & app to the latest version. Then don't longtime store your Mini in a way or into something that put pressure on the props ... preferably you put it in a book shelf fully unfolded for storage & only fold it together & put it into a bag just for the transportation to the flight location.

The latest firmware & app will warn you if the motors are revving to high & advise you to change props ... a relevant warning which should be obeyed, if not it will go down sooner or later.

 

[SalvaCG]

Yep, replace all props & update both the craft firmware & app to the latest version. Then don't longtime store your Mini in a way or into something that put pressure on the props ... preferably you put it in a book shelf fully unfolded for storage & only fold it together & put it into a bag just for the transportation to the flight location.

The latest firmware & app will warn you if the motors are revving to high & advise you to change props ... a relevant warning which should be obeyed, if not it will go down sooner or later.

Great thank you again for your answer. I always store it in the case that came with the drone (image attached) so I guess I need to stop doing that, I will follow your advice!

 

[Zbip57]

I always store it in the case that came with the drone so I guess I need to stop doing that,

Here's a post with pictures explaining how the propeller blades, especially those on the rear motors, become deformed when stored with the arms folded and blades crossed.

The problem with the original Fly More case is that it forces you to cross the blades.

See this post:

mavicpilots.com/threads/mavic-mini-crash.109111/page-2#post-1236446

 

[0Kajuna0]

I synced the data with the video to see if something else became evident, but to my eye it doesn't.

Here it is in case it's interesting:

 

[namnb]

I synced the data with the video to see if something else became evident, but to my eye it doesn't.

Here it is in case it's interesting:

Hi, how can you make this Video?

 

[0Kajuna0]

Hi, how can you make this Video?

It's my software, I sent you a PM

 

[slup]

Hi, how can you make this Video?

It's several apps that can do similar... check for instance out Dashware, several tutorials on YouTube.

Here one example based on the mobile device .txt log

 

[namnb]

It's several apps that can do similar... check for instance out Dashware, several tutorials on YouTube.

Here one example based on the mobile device .txt log

Thank for your help

 

[c64-dev]

That uncommanded landing on water is so heartbreaking to watch. SalvaCG I am very happy you managed to retrieve the drone and even more so that it seems to be working fine.

I was pleasantly surprised by that; I thought that even the slightest water ingress would render the sensitive drone electronics useless. Happy to see that our minis are sturdy little beasties.

Not wanting to highjack the thread, but Quick question on the matter of blades deforming due to storage: is this issue also affecting the Mini 2? I vary rarely have a chance to fly my mini 2 these days and I keep it stored folded in its DJI soft pouch. Do the experts think it would be better to store it unfolded?

@0Kajuna0 i would also be very interested in your software. If you could pm me too as to what it is etc, I would be grateful.