Mavic Mini drifted and crashed

[gsg4748]

Hi Folks,

Hope you guys can help me out to figure what went wrong here. This is the drone that was send to me by DJI under warranty (I hope it's a brand new). I worked fine for 3 flights but yesterday:-
1. After it took off, barely 100 ft above ground it starts drifting and crashed within 10 seconds.
2. Satellites are 10 and battery was full.
3. I was trying to go up but instead it starts drifting and then nothing happens with controls.
4. I don't have enough time but I tried to turn it off (with controllers sticks) but seems don't enough time.
5. In the logs you can see below, it starts going towards left.
6. THE MOTOR BLOCKED is the message AFTER DRONE crashed on the roof.
7. NO WIFI interface message I received and I had flown mavic mini MANY MANY TIMES in front of my home. WIth this new MAVIC MINI, it's my first ti,e.
8. I think something was wrong in the drone but could some one have a look at logs and advise please!

 

[JohnLietzke]

You would need to upload the actual log files for someone on here to evaluate what happened.

 

[gsg4748]

You would need to upload the actual log files for someone on here to evaluate what happened.

You mean .txt file?

 

[JohnLietzke]

I am no expert at interpreting logs but I will take a look. It helps in the learning process. Here a link to the flight log: Flight Log

On first glance, it appears both of your control stick were being push down and to the center of the controller when the erratic behavior began. In essence, your were telling the aircraft to decent, yaw, turn and go backwards all at the same time.

The .dat file would be helpful to know what was happening on the Mini.

 

[gsg4748]

I am no expert at interpreting logs but I will take a look. It helps in the learning process. Here a link to the flight log: Flight Log

Thx, I saw the link as well. A question, if my satellites drop to some low number in MID AIR, then drone should not fell or crash, right? In my case it starts drifting right at the start and logs are not showing why!

 

[JohnLietzke]

Thx, I saw the link as well. A question, if my satellites drop to some low number in MID AIR, then drone should not fell or crash, right? In my case it starts drifting right at the start and logs are not showing why!

The .dat file will tell you what is going on the aircraft.

The GPS Position NoMatch at the end of the log maybe the result of it crashing onto the roof. But I am not certain.

 

[gsg4748]

The .dat file will tell you what is going on the aircraft.

The GPS Position NoMatch at the end of the log maybe the result of it crashing onto the roof. But I am not certain.

I was pushing both sticks to halt the drone and drop (instead hitting someone). I might hit in wrong direction but I did all after it starts drifting. Here is the .dat file

 

[JohnLietzke]

I looked at the data file. Not a lot of information to make a conclusion. Maybe some else with more experience will see something I did not. Does your Mini still work?

 

[Drone Views Media]

Did you calibrate the IMU on a flat surface? The IMU tends to cause a lot of problems with the little Mini

 

[gsg4748]

I looked at the data file. Not a lot of information to make a conclusion. Maybe some else with more experience will see something I did not. Does your Mini still work?

arm and propellers are broken...so cant fly.
and yes IMU calibration was done on flat surface.

 

[slup]

Sorry, but this isn't anything other than a yaw error coming from powering on your Mini in a magnetic interfered environment (steel reinforced concrete in your driveway?) & by that classified as a pilot error.

The yaw disagreement between the IMUYaw (red graph) & the magYaw (blue graph, compass) was nearly 160 degrees only a couple meters above ground when the Mini was away from the magnetic interference (where I've placed the marker in the chart at 4sec), the black graph shows the disagreement directly in degrees. This meant a straight flyaway, which we see here... as soon as the Mini needed to hold position due to outside forces affecting it (like wind). Due to that the Mini's IMU had the heading direction all turned around it applied trust to the wrong motors & after that the positional error just got bigger & bigger as the speed rapidly increased.

The magnetic disturbance in this case was enough to trigger a compass calibration prompt in the app ... the calibration failed in the first attempt, but succeeded in the second. If you instead had mistrusted that prompt (you always should...) & powered down, moved away to another take off spot, powered up again, the prompt most probably hadn't showed up again.

This with yaw errors due to magnetic disturbance is little written about in the DJI documentation, they just state not to start up & calibrate in magnetic interference ... But it's a better & fail safe way to prevent incidents like this ...

After powering up your drone & the live view have appeared on the screen, always check out the map view in the app & make sure that the drone icon there is pointing equal to other map objects (like houses, roads) as it does in reality. If it does all is fine for take off ... if it doesn't POWER DOWN, then move away power up & check again.

(Click on the chart to make it larger)

 

[gsg4748]

Sorry, but this isn't anything other than a yaw error coming from powering on your Mini in a magnetic interfered environment (steel reinforced concrete in your driveway?) & by that classified as a pilot error.

The yaw disagreement between the IMUYaw (red graph) & the magYaw (blue graph, compass) was nearly 160 degrees only a couple meters above ground when the Mini was away from the magnetic interference (where I've placed the marker in the chart at 4sec), the black graph shows the disagreement directly in degrees. This meant a straight flyaway, which we see here... as soon as the Mini needed to hold position due to outside forces affecting it (like wind). Due to that the Mini's IMU had the heading direction all turned around it applied trust to the wrong motors & after that the positional error just got bigger & bigger as the speed rapidly increased.

The magnetic disturbance in this case was enough to trigger a compass calibration prompt in the app ... the calibration failed in the first attempt, but succeeded in the second. If you instead had mistrusted that prompt (you always should...) & powered down, moved away to another take off spot, powered up again, the prompt most probably hadn't showed up again.

This with yaw errors due to magnetic disturbance is little written about in the DJI documentation, they just state not to start up & calibrate in magnetic interference ... But it's a better & fail safe way to prevent incidents like this ...

After powering up your drone & the live view have appeared on the screen, always check out the map view in the app & make sure that the drone icon there is pointing equal to other map objects (like houses, roads) as it does in reality. If it does all is fine for take off ... if it doesn't POWER DOWN, then move away power up & check again.

(Click on the chart to make it larger)

View attachment 116413

Thanks for such an detailed reply and offcourse technical as well ......Thing that I don't understand here is I have taken off from the same spot many times in past.....earlier in the day as well.....2 cars were standing like on next driveway of neighbours....does that effect this? I am wondering magnetic field with cars? ....buz again I had taken off so many times with cars close by (after calibrating it though).

I hope DJI won't count this as replacement under my regular 2/year replacement, as there is nothing wrong that I did. I didn't override/ignored any warning from the DJI app as well

 

[slup]

Thanks for such an detailed reply and offcourse technical as well ......Thing that I don't understand here is I have taken off from the same spot many times in past.....earlier in the day as well.....2 cars were standing like on next driveway of neighbours....does that effect this? I am wondering magnetic field with cars? ....buz again I had taken off so many times with cars close by (after calibrating it though).

I hope DJI won't count this as replacement under my regular 2/year replacement, as there is nothing wrong that I did. I didn't override/ignored any warning from the DJI app as well

So you mean that you so far have been lucky not placing the Mini where the steel bars cross during power on ...



The cars nearby have no affect on this, it's magnetic objects much closer ... powering on on top of a wooden deck for instance, & just being unlucky & placing the drone over a nail/screw there will/can deflect the compass & making the IMUYaw initialize into the wrong direction.

Even though this is a pilot error (by starting up near magnetic objects) DJI have from time to time been taken errors like this as warranty. But you never know how they will handle it for you this time.

 

[gsg4748]

So you mean that you so far have been lucky not placing the Mini where the steel bars cross during power on ...

View attachment 116415

The cars nearby have no affect on this, it's magnetic objects much closer ... powering on on top of a wooden deck for instance, & just being unlucky & placing the drone over a nail/screw there will/can deflect the compass & making the IMUYaw initialize into the wrong direction.

Even though this is a pilot error (by starting up near magnetic objects) DJI have from time to time been taken errors like this as warranty. But you never know how they will handle it for you this time.

So you mean that you so far have been lucky not placing the Mini where the steel bars cross during power on ...

View attachment 116415

The cars nearby have no affect on this, it's magnetic objects much closer ... powering on on top of a wooden deck for instance, & just being unlucky & placing the drone over a nail/screw there will/can deflect the compass & making the IMUYaw initialize into the wrong direction.

Even though this is a pilot error (by starting up near magnetic objects) DJI have from time to time been taken errors like this as warranty. But you never know how they will handle it for you this time.

After seeing your this picture, I would say I am soooo unlucky this time ! Like I had used the same drive way to turn on and launch my mini probably 100+ times. So maybe this time the timing (in fraction of a sec) of turning on WHILE placing on the driveway ....along with the spot where steel bars cross....all come in together and hit me hard!

I will contact DJI and see what they say about this (warrenty). In my view they should not count this against my 2 free replacement /year AS as normal user (not expert) I relied on app notofications .....thanks again for your help on this. Really appreciated it

 

[DanMan32]

I'm not a fan of Having to power up the Mini while in hand and then placing on the ground quickly enough. I mainly am considering the gimbal initialization, but compass and IMU initialization also factor in.

It always should be like fireworks:
Place on ground
Light fuse (power on)
Move away

 

[slup]

I'm not a fan of Having to power up the Mini while in hand and then placing on the ground quickly enough. I mainly am considering the gimbal initialization, but compass and IMU initialization also factor in.

It always should be like fireworks:
Place on ground
Light fuse (power on)
Move away

Power it on in your hand, stretched out in front of you & not placing it on ground until the live view have appeared in the app is absolutely the best way to keep the AC out of possible magnetic sources from ground level (no watches, rings or bracelets on the hand holding it) ... then check the drone icon direction in the map & make sure it's equal to reality.

You don't have... or you shouldn't be to quick to put it on ground after power on, take your time until you see the camera view in the app, the IMUYaw is then initialized. Neither is it any problem regarding the gimbal start up, if it's properly calibrated earlier it will not show tilted horizons if you don't hold the AC absolutely leveled, don't worry about that just keep your fingers away so you don't block it's movements during startup.