Mavic Mini doesn't take off straight up after arm replacement

[restlesswind]

My Mavic Mini doesn't take off straight up anymore after I replaced the broken right front arm. It always drifted towards the replaced arm for a few feet when taking off. Once it is a couple feet in the air, it is stable (I guess by this time, the vision sensor/GPS takes over). I tried all calibrations (IMU, RC, compass) and replaced all props but nothing helped. I wonder if anyone knows how to resolve this? I suspect the motor controller? for the replacement arm motor might need to be calibrated/tuned? but not sure if it is even possible and how? Thanks.

 

[Thomas B]

If it lands in the actual TO area, +/- 6-12”, I’d just fly it.

 

[FlyoverDRN]

But it does have an issue you can witness at take off. It needs to be resolve, as of now, it will use a lot more battery power to keep itself flying strait and level.

 

[boblui]

Can you post the .DAT flight log file in the phone ? It may give some clues. Follow this thread to get it : Mavic Flight Log Retrieval and Analysis Guide

 

[restlesswind]

flight data attached. Thanks a lot. @boblui

 

[boblui]

I got the "unrecognized log file" errror message upon opening the .DAT file with CsvView. Hope @BudWalker can lend some help .....

 

[BudWalker]

I got the "unrecognized log file" errror message upon opening the .DAT file with CsvView. Hope @BudWalker can lend some help .....

Try changing file name extension to capital D-A-T. This is an attempt by CsvView to reject the several lower case .dat files.

 

[boblui]

I thought this is an easy case but it turns out that it's not .....

The drift in position during take off is usually due to bad props but this cause can be ruled out as the speed of the four motors are very close to each other :



This is my Mini with bad front props which were intentionally flattened for test purpose. The reduced pitch means that higher speed at the front motors is required to generate the same thrust :



The OP mentioned that the craft was stable after takeoff but the log file tells a different story. There was a postion shift of 0.6 units ( meters ? ) during takeoff but after that the craft would abruptly pitch forward and backward causing constant jumps in horizontal position. Throughout the flight no elevator control has been applied so this is abnormal. When flying outdoor, this could be due to strong gust but I can't imagine any reasons for indoor environment ( no GPS satellites seen in the entire flight ). I believe that the position drift during takeoff is due to the same reason.



My Mini equipped with deformed front props also exhibited position shift during takeoff but once the craft was hovering, the position and attitude were very stable :



In short I don't know what's wrong with the craft. Hope other more experienced analysts can chime in.

 

[restlesswind]

Thanks a lot for the analysis @bobliu. Yes, the data was collected indoor. Surprised (but good) to know that the drift was not related to the motor speed. Besides the drift during taking off, another thing I noticed is that when rotating (turning) the craft, it makes a small circle instead of around the centre of the craft. Other than that, everything else seems to be normal. RTH also works reasonably well.

 

[boblui]

You may consider checking the mounting of the GPS/IMU board inside the craft. May be it's dislocated in the crash. Just a wild guess.

The GPS/IMU board is shown at 6:23 of this video :

 

[restlesswind]

excellent call @boblui ! this indeed the problem. BTW, the dislocation did not happen during the crash but when I installed the new arm (probably when I pushed the wires) Thanks everyone. this forum has been great!

 

[gemniii]

Could you circle the differences in the two photos please.

 

[restlesswind]

sorry. for some reason two pictures were shown. Just one picture with the disjointed mount.

 

[gemniii]

Well, there goes 5 minutes of my life