DJI Mavic Mini 1 suddenly goes forward, downward and crashes

[dji_speed03]

Hello @ all,

I have a DJI Mavic Mini that I unfortunately crashed on holidays. One leg broke and I could install a new one. At the first sight, the drone seems to work again. However, after a few minutes mostly it always starts to gain speed (without input task from remote), goes forward and downwards and crashes into the ground.

I have the log data here:

DJI Flight Log Viewer - PhantomHelp.com

I would be thankful about any help!

Cheers,
Peter

 

[slup]

Hi there & welcome to the forum

If involved in a crash... a IMU calibration can be needed in order for it to hover in place, try that to begin with... the descending is troublesome though & indicate that this will not just be solved by a calibration.

And... see to that you get a solid GPS lock when trying... the log shows ATTI mode, there you doesn't have any horizontal positional hold at all.

 

[dji_speed03]

Hi there & welcome to the forum

If involved in a crash... a IMU calibration can be needed in order for it to hover in place, try that to begin with.

Thank you for your answer! However, I just did this before the log!

 

[slup]

Added some while you answered... read that, you can't try out how well it holds position in a hover when in ATTI mode. Go outside & wait for it to announce that a home point have been recorded, then take off & try.

You also have this in the log event stream... maybe you messed something up when replacing that leg?

(click on it to make it larger)


You also have another log ending with .DAT in the screen device you flew with, the correct one is ending with FLY071.DAT & is located in the same place as the .TXT log you've shared but in a sub folder there named MCDatFlightRecords ... this log contains the motor data. Retrieve it & share it with us.

 

[Yorkshire_Pud]

Where was the flight, indoors or out doors and what was the lighting like?
Was the ground well lit?
Since there was no GPS poor lighting will prevent the VPS sensor working and result in ATTI.
But as @slup has noted the height is troubling

 

[dji_speed03]

thanks for your answer! The .DAT-content can be found here:

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[MavicAir2Marc]

Did you replace the propellers after the crash?

 

[slup]

thanks for your answer! The .DAT-content can be found here:

Quick Text

Easy, fast and secure online text sharing. You don't have to any registration it's free forever. The fastest way to share. You can create a quick text, convert an image to text and send it to your friends, or share anything else you need!

qtext.io

Can't find anything through that link unfortunately... the screen device .DAT log shouldn't be that large, around 5Mb, just attach it directly in a post with the "Attach files" button.

 

[Zbip57]

Regarding the "motor speed error" message, upon landing one of the motors will be twitching as the ESC beeps indicating which motor is affected. It will likely be one of the rear motors. Replace the propeller blades on that motor!

It'll look and sound like this. Here it was the left-rear motor on my Mini.

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Read the comments on that video and follow the links to previous MavicPilot forum posts explaining why the propeller blades become warped and lose effectiveness (even though they might "look" perfectly undamaged).

 

[slup]

...the propeller blades become warped and lose effectiveness (even though they might "look" perfectly undamaged).

Yeah... this was my thought as well, was hoping to see the .DAT with motor rpm's on max.

 

[Zbip57]

You also have this in the log event stream... maybe you messed something up when replacing that leg?
(click on it to make it larger)
View attachment 171879

DJI kept changing the message of their Motor Speed Error text. They added this completely nonsensical bit, as though hovering for 5 minutes would somehow "align the propellers" to cure the warping issue: "If any of the propellers are warped, restart the aircraft and hover in an open area for 5 minutes to align the propellers." Huh?

Motor speed data extracted from the DAT log file during a 5-minute hover test clearly indicates whether the prop blades are warped and in need of replacement, but merely hovering for 5 minutes certainly will not cure the issue.

See this thread on the DJI forum for a detailed discussion with photos and data plots.

Motor Speed or Propeller Speed Error - How to avoid.

Propeller blade deformation, causing a reduction in lift capacity, prompts the flight controller to spin the motors faster to continue generating the required lift to sustain flight. Eventually the motor speeds will hit a preset threshold limit that, ever since the latest firmware v01.00.0500...

forum.dji.com

 

[dji_speed03]

I rplaced the rotor-blöades (propellers?) with new ones! The problem is, that it goes more or less fine for a few minutes, and then - always after a feew minutes - starts going forward, downwards and crashes. I honestly think, this is either the heating or some of the core components...