Mavic Mini crash help

[Caseytbell]

Hi all, wondering if someone can help me figure out what happened here? Mavic Mini is basically brand new, was only flown the previous day and everything seemed fine. Got a temp warning on bootup that promptly went away. Shortly after takeoff the mini became unresponsive and rapidly descended into the lake, crashing in about a foot of water. I'd really like to know what went wrong, but I'm not familiar with the DJI log files. I've flown cheaper 'toy' drones many times before, but never had one behave like this before... Any help would be appreciated! Thanks.

 

[lannes]

How low over the water were you flying , DJI recommends an altitude of at least 2m or 7ft over water ?
The VPS sensors get confused by waters reflective surface

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[lannes]

How to view DJI Flight logs

DJI Flight Log Viewer | Phantom Help

Upload and view flight logs from your DJI drones

www.phantomhelp.com

This is your converted log

DJI Flight Log Viewer | Phantom Help

Upload and view flight logs from your DJI drones

www.phantomhelp.com

If you were using mode 2 for the control stick configuration, it looks like at the end 58 sec (before hitting the water) you applied downwards stick to reduce the height of the drone

 

[Caseytbell]

Thanks for the feedback! Takeoff was from a deck on shore and immediately up to about 15ft, so theoretically high enough that it shouldn't have been an issue with the water surface reflection. As for the down stick, the drone become completely unresponsive around the 44 sec mark and starting reversing and then rapidly lost height. You can see from the log it started moving without any stick inputs, it seems not to have record the attempts to recover either. I'm not sure why it only shows that downstick and nothing else...

 

[Meta4]

Hi all, wondering if someone can help me figure out what happened here? Mavic Mini is basically brand new, was only flown the previous day and everything seemed fine. Got a temp warning on bootup that promptly went away. Shortly after takeoff the mini became unresponsive and rapidly descended into the lake, crashing in about a foot of water. I'd really like to know what went wrong, but I'm not familiar with the DJI log files. I've flown cheaper 'toy' drones many times before, but never had one behave like this before... Any help would be appreciated! Thanks.

You didn't give your Mini much joystick input during that short flight.
Most of the time it was hovering.
You launched and took the drone up to 10 feet and twice gave it a touch of forward movement.
From 0:53 the drone started to slowly lose altitude.
And at 0:57.9 when the VPS sensors indicated the drone was 9 feet above the water, you responded by pulling the left joystick down hard for 0.6 seconds which brought the drone down to 5.5 ft above teh water.
At 0:59.8 you pulled the left stick becak again and held it down until the data ends (when the drone splashes down).

The drone appears to have followed your joystick inputs and the data really doesn't support your description: the mini became unresponsive and rapidly descended into the lake, crashing in about a foot of water.

 

[sar104]

Hi all, wondering if someone can help me figure out what happened here? Mavic Mini is basically brand new, was only flown the previous day and everything seemed fine. Got a temp warning on bootup that promptly went away. Shortly after takeoff the mini became unresponsive and rapidly descended into the lake, crashing in about a foot of water. I'd really like to know what went wrong, but I'm not familiar with the DJI log files. I've flown cheaper 'toy' drones many times before, but never had one behave like this before... Any help would be appreciated! Thanks.

Thanks for the feedback! Takeoff was from a deck on shore and immediately up to about 15ft, so theoretically high enough that it shouldn't have been an issue with the water surface reflection. As for the down stick, the drone become completely unresponsive around the 44 sec mark and starting reversing and then rapidly lost height. You can see from the log it started moving without any stick inputs, it seems not to have record the attempts to recover either. I'm not sure why it only shows that downstick and nothing else...

It's not completely clear what happened, but it was not completely unresponsive. For example, the velocity forwards and backwards followed your elevator input precisely. It did not move backwards significantly until 58 seconds when you applied full back elevator:



Vertical motion is a different matter:



It started to descend at around 55 seconds. That was uncommanded, but it isn't accompanied by any of the pitch and roll instabilities that are characteristic of loss of thrust from the Mini's rear motors. So a bit of a mystery. Can you see if the mobile device DAT file ending FLY013.DAT is available - it will have the raw sensor data.

 

[Meta4]

As for the down stick, the drone become completely unresponsive around the 44 sec mark and starting reversing and then rapidly lost height. You can see from the log it started moving without any stick inputs

The movement noted was 4.4 feet over 13 seconds.
It may have been due to the VPS attempting to lock onto the water's surface and/or it could have just been the normal minor instability of horizontal position holding
From the Mini specs Hovering Accuracy Range: Horizontal: ±1.5 m (with GPS Positioning)

There's no record of any joystick input from 0:43.4 until 0:57.9 to show any unresponsiveness, but joystick input before and after looks to have been recorded accurately.

In the end, it was pulling the left stick down that sank the Mini.
The appropriate action would have been to push the left stick forward and/or bring the drone back to you but neither of those happened.

FYI the downward sensors have an effective range of 33 feet

 

[sar104]

The movement noted was 4.4 feet over 13 seconds.
It may have been due to the VPS attempting to lock onto the water's surface and/or it could have just been the normal minor instability of horizontal position holding
From the Mini specs Hovering Accuracy Range: Horizontal: ±1.5 m (with GPS Positioning)

There's no record of any joystick input from 0:43.4 until 0:57.9 to show any unresponsiveness, but joystick input before and after looks to have been recorded accurately.

In the end, it was pulling the left stick down that sank the Mini.
The appropriate action would have been to push the left stick forward and/or bring the drone back to you but neither of those happened.

FYI the downward sensors have an effective range of 33 feet

The descent recorded by VPS was closer to 15 ft, and it seemed to be functioning properly, so I doubt that caused the problem. The two periods of full down throttle in the last 3 seconds of the flight didn't help, but at that point it looks like it was going down anyway.

 

[Meta4]

The descent recorded by VPS was closer to 15 ft, and it seemed to be functioning properly, so I doubt that caused the problem.

The movement I described was the horizontal movement the OP mentioned when he said that the drone started reversing.

 

[Caseytbell]

Thanks again everyone for all the input. Meta4, the fact that the data doesn't match my description is exactly why I am here I have attached the DAT file, hopefully that helps.

 

[Capt KO]

Your description doesn’t match the flight but the data does. Minis descending (unaided) over water was discovered early on in mini history. The lower you are, the worse the problem. Lessons learned. Fly safe, next time. Good luck.