why did this drone get blown away?

[carlinski]

Hi all,

I had flown this drone maybe a dozen times, so I recognize I'm a newbie and likely made multiple mistakes to cause this drone to leave me...
But having lived it, and having pored over the flight log, I don't understand why this thing flew so high and got blown away.

It consistently flew higher and higher despite my constantly holding the left lever down.
Clearly there was wind involved, but why wouldn't it come down?
I had 3/4 mile of woods I would have been happy to crash it in, rather than have it blown out of range over people and property.
It just wouldn't come down.
Even in RTH and Forced Landing mode it was still goin up.

Based on the logs, I can't tell if it fell out of the sky (battery failure) when I lost the connection, or if it got out of range and may have continued further.
Clearly the battery was ready to give out, and it was at the very edge of it's transmission range....I'm just not sure which came first.

Hopefully it's clear, but just in case: I had zero intention of flying higher than 400' - I'm aware that's against regulations. Honestly, I thought I remembered that when you hit 400' it would override your attempts to go higher....
Either way, it's clear by my control log that I was trying desperately to bring it down, aside from a few moments where I checked to make sure the controls hadn't reversed!

Experienced analysis appreciated. Go easy on me, please

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Carl

 

[slup]

Wow ... this was impressive, if the barometric height actually was correct your Mini reached over 4700ft above the HP ... that's way higher than the SW lock of 500m (1640ft).

Here below a cutout from the end of the flight ... the Mini was autolanding & you were applying full throttle for descending but the Mini still ascended. Meanwhile the height shows ascending, the Zspeed (vertical speed) shows a positive value which indicate that the IMU actually thought it was descending. The vertical velocity difference between the GPS & IMU also shows a large deviation which could indicate that this could be a IMU failure.

Going by Airdata.com wind calculations your Mini was blown away with over 60mph ...

@BudWalker @sar104

(Click on the chart to make it larger ... the legend below the chart says what the graphs mean & values from where the chart marker is placed)

 

[sar104]

Weird - that's the second case of this problem recently. It kept climbing because either the z-axis accelerometer failed or the IMU calculations based on that accelerometer failed. Looking at the OSD height, which is heavily weighted by the barometric pressure, the z-axis (vertical) velocity, which is primarily computed from z-axis acceleration, and the time-integral of the z-axis velocity, the problem is obvious:



The OSD height reading (red) clearly shows the aircraft climbing to over 1000 m while you were trying to make it descend. But the z-axis velocity (orange - positive is down) and its time-integral (blue), corrected for positive is up, shows that the IMU thought that the aircraft was descending even though it was actually climbing, and so it was trying to compensate for that.

This was the other case:

DJI Mini 2, Spiral out of control, 2022-02-15

Hi guys, I have (should say "had") a DJI Mini 2 that I have been using over the past 6 months. It has about 275 flights with 50 hours of flight time and 650 kilometers. Today as the drone took off, it flew forward properly for a few seconds before suddenly reporting a rotor motor error and...

mavicpilots.com

 

[sar104]

Wow ... this was impressive, if the barometric height actually was correct your Mini reached over 4700ft above the HP ... that's way higher than the SW lock of 500m (1640ft).

Here below a cutout from the end of the flight ... the Mini was autolanding & you were applying full throttle for descending but the Mini still ascended. Meanwhile the height shows ascending, the Zspeed (vertical speed) shows a positive value which indicate that the IMU actually thought it was descending. The vertical velocity difference between the GPS & IMU also shows a large deviation which could indicate that this could be a IMU failure.

Going by Airdata.com wind calculations your Mini was blown away with over 60mph ...

@BudWalker @sar104

(Click on the chart to make it larger ... the legend below the chart says what the graphs mean & values from where the chart marker is placed)
View attachment 144734

It was another z-axis accelerometer problem. The wind at altitude was most likely correct, since the horizontal IMU solution looks pretty good:

 

[Yorkshire_Pud]

WOW, impressed that it went so high.
Can I suggest you also post this over on the DJI forum.

Mavic Mini - DJI Products forum

Seize the Moment. DJI Products discussion and support.

forum.dji.com

This flight needs to be drawn to DJI's attention.

@carlinski a CSC might have brought it down but you would have to have switched the response mode to "Anytime" for that to work.

 

[MA2 317]

Hi all,

If hello from the Crossroads of America carlinski.

Looks like you're getting the help you need.

Welcome to the Forum.

 

[carlinski]

Well based on these first few comments, I'm glad to know it wasn't simple inexperience error on my part.

I am happy to post in dji's forums so they might keep a record and try to learn.

Can anyone advise me on whether I'm likely to have any chance of getting this drone replaced by dji based on this apparent malfunction? Any tips on where/how to enquire? They appear to assume every flyaway is user error and only covered if you have their refresh insurance (which I don't).

Maybe this type of flyaway is extremely rare, but they definitely don't make it easy to figure out whether it's even possible for me to petition them for a replacement.

Either way, glad it wasn't a much more expensive version, and most importantly, I don't think there was any property (aside from the drone itself - which I obviously have not recovered) or human damage based on the loss and ensuing crash.

Thanks,
Carl

 

[sar104]

Well based on these first few comments, I'm glad to know it wasn't simple inexperience error on my part.

I am happy to post in dji's forums so they might keep a record and try to learn.

Can anyone advise me on whether I'm likely to have any chance of getting this drone replaced by dji based on this apparent malfunction? Any tips on where/how to enquire? They appear to assume every flyaway is user error and only covered if you have their refresh insurance (which I don't).

Maybe this type of flyaway is extremely rare, but they definitely don't make it easy to figure out whether it's even possible for me to petition them for a replacement.

Either way, glad it wasn't a much more expensive version, and most importantly, I don't think there was any property (aside from the drone itself - which I obviously have not recovered) or human damage based on the loss and ensuing crash.

Thanks,
Carl

If it is under warranty then I would expect DJI to replace, based on the flight log data, but since it is a Mini then I would guess that it is out of warranty.

 

[Meta4]

Can I suggest you also post this over on the DJI forum.

This flight needs to be drawn to DJI's attention.

Your idea of the effectiveness of DJI's forum is unrealistic.
Posting there won't bring the issue to DJI's attention.

 

[Meta4]

Can anyone advise me on whether I'm likely to have any chance of getting this drone replaced by dji based on this apparent malfunction? Any tips on where/how to enquire?

It would have to be less than one year since purchase to be in warranty.

They appear to assume every flyaway is user error and only covered if you have their refresh insurance (which I don't).

Contrary to what some might suggest, DJI look at the flight data and make quite a lot of warranty replacements when teh data provides evidence to support this.

 

[Yorkshire_Pud]

Your idea of the effectiveness of DJI's forum is unrealistic

In some case yes but not in all.
Besides, even if it does nothing other that bring it to the attention of other users it serves a purpose.

 

[Capt KO]

Sorry for your loss. If bought new, would be worth contacting DJI, supplying the logs, and see what happens. Hope you marked your drone in case it’s found.

 

[carlinski]

Thanks, all.
I did buy it new, just a few months back, so I've initiated a repair/replace request with DJI.
I did not have the drone marked, unfortunately. If the SD card survived and was found by someone smart and curious, I think they'd have found me by now. More likely it's in a few dozen pieces somewhere in the woods or behind some industrial building. Having fallen from so high, in such strong winds, the search area would be gigantic. I spent some time in the vicinity of where the signal was lost, but I'm betting it drifted at least another 1/4" mile, and could easily have gone miles further if it remained hovering past when the signal was lost.
I'll report back what DJI engineers decide.
Carl

 

[sar104]

Thanks, all.
I did buy it new, just a few months back, so I've initiated a repair/replace request with DJI.
I did not have the drone marked, unfortunately. If the SD card survived and was found by someone smart and curious, I think they'd have found me by now. More likely it's in a few dozen pieces somewhere in the woods or behind some industrial building. Having fallen from so high, in such strong winds, the search area would be gigantic. I spent some time in the vicinity of where the signal was lost, but I'm betting it drifted at least another 1/4" mile, and could easily have gone miles further if it remained hovering past when the signal was lost.
I'll report back what DJI engineers decide.
Carl

In that case I expect that once they see the flight log they will replace it free of charge.

 

[carlinski]

Well,
I finally reported this to DJI warranty/tech support. They say they'll replace the aircraft.
I've asked for additional details about their analysis of the failure, as well as requested that they also replace the battery and sd card that were on board (hopefully?!). Will share further if anything interesting comes of it.
Thanks very much for your input,
carl

 

[sar104]

Well,
I finally reported this to DJI warranty/tech support. They say they'll replace the aircraft.
I've asked for additional details about their analysis of the failure, as well as requested that they also replace the battery and sd card that were on board (hopefully?!). Will share further if anything interesting comes of it.
Thanks very much for your input,
carl

Excellent. I continue to be impressed by their response to these kinds of issues. However, you are unlikely to get any details on their analysis, and they quite likely won't have done much beyond noting the obviously flawed z-axis behavior.

 

[carlinski]

So,
I did receive a new mini, battery, and the replacement sd card should be here tomorrow. Warranty people were very easy to deal with.
My inquiries about what happened, and what I could have done differently were essentially met with, "don't worry about it, this is a very rare failure."

My only remaining question is whether anyone can figure out from the data whether the drone fell from the sky at the last reported location, or if it's likely that it continued attempting to hover (and be blown away at 40mph) for any length of time...?
It was nearly at the extent of it's transmission distance ability....and the battery was also (nearly?) completely drained.
If it hovered for even another 30 seconds it wouldn't be worth any efforts to look for because it could be miles to search....but if I knew it fell from the last known location I might go poking in a few plots of trees for it, based on it's speed and a guess at the speed it would have fell/tumbled/drifted. Wouldn't mind finding the SD card, is all....
new link since apparently they delete them after a bit (which is nice).

DJI Flight Log Viewer | Phantom Help

Upload and view flight logs from your DJI drones

www.phantomhelp.com

thanks for all your help and input,
carl

 

[sar104]

So,
I did receive a new mini, battery, and the replacement sd card should be here tomorrow. Warranty people were very easy to deal with.
My inquiries about what happened, and what I could have done differently were essentially met with, "don't worry about it, this is a very rare failure."

My only remaining question is whether anyone can figure out from the data whether the drone fell from the sky at the last reported location, or if it's likely that it continued attempting to hover (and be blown away at 40mph) for any length of time...?
It was nearly at the extent of it's transmission distance ability....and the battery was also (nearly?) completely drained.
If it hovered for even another 30 seconds it wouldn't be worth any efforts to look for because it could be miles to search....but if I knew it fell from the last known location I might go poking in a few plots of trees for it, based on it's speed and a guess at the speed it would have fell/tumbled/drifted. Wouldn't mind finding the SD card, is all....
new link since apparently they delete them after a bit (which is nice).

DJI Flight Log Viewer | Phantom Help

Upload and view flight logs from your DJI drones

www.phantomhelp.com

thanks for all your help and input,
carl

No - it looks like it ran out of battery at around 5000 ft AGL while trying to descend. I could estimate the descent trajectory but the calculated wind speed was around 60 mph at that altitude and so the error bars on the crash coordinates would be hundreds of meters.

 

[Yorkshire_Pud]

Firstly, I am glad you got a drone.
Secondly it is a pity they gave the "don't worry about it, this is a very rare failure." answer, I think there was a small spate of such incidents at that time.
Sar104, do you think the 'loss of signal' was a shut down rather than a true loss of signal?

 

[Yorkshire_Pud]

@carlinski you might find this thread interesting, Restarting the Mavic Mini 2 Mid-Air after CSC