Hi everyone in DJI community,

I am new here so to say hi to everyone.
I just nearly got an heart attack when my DJI mavic mini just free falling from almost 100 ft within seconds and landed on a concrete ground.

Situation was that I trying to capture some night image with very very far distance fireworks.
Didn't really hover my MM around , but to keep it close and right on top of homepoint. And really lucky I did so.
Was somehow ok on the first few minutes but not sure what happen on the 9-10mins mark that it just dropping in altitude and suddenly "stopped" i assume and free falling.

I suspect that it might have something to do with the downward sensor , not sure if it's due to the darkness of the environment so it can't detect the ground level ?
but actually there were streets lights.

Here's the flight log :
https://www.phantomhelp.com/logviewer/4JPL1CX70UIB01HYLR6Q/#

Would be glad if anyone could comment a little on these as I am really a beginner to drones.

Thank you in advance.

Can you tell us what temperature you were flying at ?

Hello and good day GavinThin. I am sorry to read and to know what happened to your previous flight with your DJI Mavic Mini. Since this unfortunate incident happened. Kindly please contact out DJI Support Team for further assistance at https://www.dji.com/support?site=brandsite&from=nav. We would do their best to find out the reason of the incident and then the corresponding resolution would be provided. Again I am sorry for what happened and thank you for your understanding.

Hi Gavinthin, your log reads exactly as you say, but still a mystery and not a really good one, flying at night should be ok , just two things might cause problems, fog and cold, we have seen some similar landing in temperatures of 0 to minus 2 C, it seems the IMU in mini doesn’t like the cold, but other than that you might have a problem that needs to be sent for repair or replacement by dji.

Maybe some testing at lower altitude in both day and night time .

Your battery was pretty low when the AC stalled after more than 2000 ESC NotEnoughPower errors.

I think you may have:
- bad/bent out of shape propellers.
- ESC problems
- battery problems, battery chip version mismatching with AC firmware revision.

hallmark007 Posted at 2-1 10:48
Hi Gavinthin, your log reads exactly as you say, but still a mystery and not a really good one, flying at night should be ok , just two things might cause problems, fog and cold, we have seen some similar landing in temperatures of 0 to minus 2 C, it seems the IMU in mini doesn’t like the cold, but other than that you might have a problem that needs to be sent for repair or replacement by dji.

Maybe some testing at lower altitude in both day and night time .

Hi hallmark007!
Is true that quite a few drops have been cold related, however all of my drops happened between 8 and 14 degrees + Celsius.

I don't think is just one thing but could be a combination of IMU readings, a bit less power in the motors, extreme or demanding movements in sports mode, wind, altitude...

I strongly believe we will see an improvement in the next FW update.

I've also had problems with MM losing altitude, but its just from 2-4m over ground and not like freefall. And it stops if i give full throttle. DJI says it could be the cold, been flying in -10 to -2 celsius.

InspektorGadjet Posted at 2-1 12:10
Hi hallmark007!
Is true that quite a few drops have been cold related, however all of my drops happened between 8 and 14 degrees + Celsius.

I’m not sure what it is, I don’t have a problem with it, but in testing in cold conditions I can create this with mini .
I ask the question to confirm or eliminate and I asked OP to test also to eliminate.

The mini can be unpredictable in cold weather.  I've seen it fly terribly, but I have also seen it fly normally in quite cold temps.

Neither temperature nor wind seem to be the cause here:

Zelmani Posted at 2-1 15:08
Neither temperature nor wind seem to be the cause here:

[view_image]

I wonder humid would that cause sensors to fog up ?

hallmark007 Posted at 2-1 10:20
Can you tell us what temperature you were flying at ?

The OP is from Malaysia, so I don't think cold weather would have been a factor.

Tervist Posted at 2-1 15:31
The OP is from Malaysia, so I don't think cold weather would have been a factor.

Yeah I see that from post above, I did also ask if there was fog but not that either but it was extremely humid so would this cause sensors to fog up and force craft to land, I don’t know just being devil’s advocate here .

hallmark007 Posted at 2-1 10:20
Can you tell us what temperature you were flying at ?

Hi hallmark007, Thanks for the reply and concern.

I am guessing about 28 - 30 degree ?
Wasn't a cold place on my side.

DJI Stephen Posted at 2-1 10:23
Hello and good day GavinThin. I am sorry to read and to know what happened to your previous flight with your DJI Mavic Mini. Since this unfortunate incident happened. Kindly please contact out DJI Support Team for further assistance at https://www.dji.com/support?site=brandsite&from=nav. We would do their best to find out the reason of the incident and then the corresponding resolution would be provided. Again I am sorry for what happened and thank you for your understanding.

Hi DJI Stephen, Thanks for the reply and concern.

Yes, will do as suggested.
I updated my firmware everytime before my flight and this is the only time this happen.
Updated firmware of the version at 1st of Feb 2020.

hallmark007 Posted at 2-1 10:48
Hi Gavinthin, your log reads exactly as you say, but still a mystery and not a really good one, flying at night should be ok , just two things might cause problems, fog and cold, we have seen some similar landing in temperatures of 0 to minus 2 C, it seems the IMU in mini doesn’t like the cold, but other than that you might have a problem that needs to be sent for repair or replacement by dji.

Maybe some testing at lower altitude in both day and night time .

Hi hallmark007, thanks again for the prediction.
My place wasn't a cold place and don't think there's any fog around at that time.
So I think it might be caused by other reason.
sadly.

m80116 Posted at 2-1 11:24
Your battery was pretty low when the AC stalled after more than 2000 ESC NotEnoughPower errors.

I think you may have:

Hi m80116, Thanks for the reply and concern.

I have experience previously return my drones at power level of 12-15% .
not sure if this time it just free falling at the battery level of 20-25%. seems not right.

Regarding the propellers shape, they are in good condition before take off.
but some of them have minor cracks after the drop. =(

What is an ESC problem ?

And how do i solve this battery chip problem ?
As I do update firmware before take off.

InspektorGadjet Posted at 2-1 12:10
Hi hallmark007!
Is true that quite a few drops have been cold related, however all of my drops happened between 8 and 14 degrees + Celsius.

Hi InspektorGadjet, Thanks for the reply and concern.

I am not sure about if these arethe causes as well,
but I just keep my drone on top of me, while rotating left and right.
doesn't windy as well...

Things that I did before the flight was update the firmware..

Zelmani Posted at 2-1 15:08
Neither temperature nor wind seem to be the cause here:

[view_image]

Hi Zelmani, Thanks for the information.

How do you get these information?
From the link of my flight log able to extract these?
Sorry I am still a beginner.

Tervist Posted at 2-1 15:31
The OP is from Malaysia, so I don't think cold weather would have been a factor.

Hi Tervist,

Yes I am flying my drone in Malaysia.
So it's not a cold place definately.
Sky are clear and doesn't really have fog from what I see.

hallmark007 Posted at 2-1 15:39
Yeah I see that from post above, I did also ask if there was fog but not that either but it was extremely humid so would this cause sensors to fog up and force craft to land, I don’t know just being devil’s advocate here .

Hi hallmark007, Thanks for following my cases.

I not sure if my place is humid, doesn't rain for days.
Temperature was around 25-30 degree Celsius.

I am assuming as well that something wrong with the down sensor and force it to stop and free falling.
Not sure what type of sensor it's using, whether by light intensity or infrared to detect the distant.

Really scare ... out of me to have the drone just fall like that.
luckily i didn't fly my drone far from me.

fog and cold yeah, oh you mean Malaysia City which is a suburb of San Francisco?

If this drone cannot tolerate any other weather conditions outside San Diego, I know it's January all over but c'mon, is that the only place DJI tested (if they field tested this drone at all)?

I'm just a beginner here, but in the interest of educating myself, I took a look at the verbose csv data file created by phantomhelp using Excel. I compared it with one created for my drone while landing to see what differences I could find. It appears that the OP's drone was in "Go Home" mode at about 20% of the way through the flight if I am reading the file right; and then went into something called "Drop landing" mode about 25% of the way through the flight and stays that way for the rest of the flight. Does any of this make sense to the experienced users here? Just trying to learn.

Is it possible that the drone entered RTH mode somehow and did not show a notification? Then the operator used controls that interrupted the RTH mode including raising it to 90 feet altitude, then stopped using any controls and the drone resumed RTH mode and crashed because of the low light or fogged sensor(s)? Again, just a wild uneducated guess.

I can reproduce this issue with flying at 6° 12min in sport mode.
What if we have this issue all in summer with flying 5mins at 25°?


Edit: i had never ESC Errors, so i think its an different issue.

GaryDoug Posted at 2-1 19:54
I'm just a beginner here, but in the interest of educating myself, I took a look at the verbose csv data file created by phantomhelp using Excel. I compared it with one created for my drone while landing to see what differences I could find. It appears that the OP's drone was in "Go Home" mode at about 20% of the way through the flight if I am reading the file right; and then went into something called "Drop landing" mode about 25% of the way through the flight and stays that way for the rest of the flight. Does any of this make sense to the experienced users here? Just trying to learn.

Is it possible that the drone entered RTH mode somehow and did not show a notification? Then the operator used controls that interrupted the RTH mode including raising it to 90 feet altitude, then stopped using any controls and the drone resumed RTH mode and crashed because of the low light or fogged sensor(s)? Again, just a wild uneducated guess.

Hi Gary,

Great to have interest in logs.

User pressed RTH but because craft was within 20 meters from HP is did an autolanding.
So it was never in a GoHome mode, "DropLanding" means users did cancel the autolanding, as "DropGoHome" (btw: not in this file) means user cancel the RTH mode.

cheers
JJB

Thanks Gavin, at least we have eliminated most of what I asked, my advice is to first sync your flight, try contacting a moderator here to ask if they can get an engineer to look at your log, in the meantime do some checks there are some other cases here and while some are common to the cold weather there seems to be no common denominator for all unless a bug in FW, I myself have had no noticeable problems .
It has also been recommended that you be on latest FW and calibrate IMU and gimbal .

GavinThin Posted at 2-1 18:55
Hi Zelmani, Thanks for the information.

How do you get these information?

I downloaded your flight log from Phantomhelp and uploaded it to airdata.com. You can open a free account at their site to upload your flight logs. With the free account, you get basic information on errors during flight, signal quality and ground weather condition. With a paid account, you will have additional information, e.g. on winds during flight and battery statistics.

I have one question: Did you eventually have the propguards mounted when the drop occurred?

The Saint Posted at 2-1 19:17
fog and cold yeah, oh you mean Malaysia City which is a suburb of San Francisco?

If this drone cannot tolerate any other weather conditions outside San Diego, I know it's January all over but c'mon, is that the only place DJI tested (if they field tested this drone at all)?

Hi, The Saint.

I am not sure which place you talking about but it happened in Malaysia.
Which is not cold at all.

GaryDoug Posted at 2-1 19:54
I'm just a beginner here, but in the interest of educating myself, I took a look at the verbose csv data file created by phantomhelp using Excel. I compared it with one created for my drone while landing to see what differences I could find. It appears that the OP's drone was in "Go Home" mode at about 20% of the way through the flight if I am reading the file right; and then went into something called "Drop landing" mode about 25% of the way through the flight and stays that way for the rest of the flight. Does any of this make sense to the experienced users here? Just trying to learn.

Is it possible that the drone entered RTH mode somehow and did not show a notification? Then the operator used controls that interrupted the RTH mode including raising it to 90 feet altitude, then stopped using any controls and the drone resumed RTH mode and crashed because of the low light or fogged sensor(s)? Again, just a wild uneducated guess.

Hi GaryDoug,

Thanks for the analysis and detailed explanation. I am not sure if that's the problem as well.
I have submitted to DJI support and hopefully they manage to find a solution for this.
I myself are doubting might be the updated firmware.
And It's my first night flight. So I not sure if it's night flight as well...

Christian U Posted at 2-1 22:25
I can reproduce this issue with flying at 6° 12min in sport mode.
What if we have this issue all in summer with flying 5mins at 25°?

Hi Christian U, Thanks for the reply.

However I am not flying in sport mode, but in tripod mode.
And I didn't also hover my drone a lot, basically it just raise up, rotate around to take some photo.
And drop.

hallmark007 Posted at 2-2 03:13
Thanks Gavin, at least we have eliminated most of what I asked, my advice is to first sync your flight, try contacting a moderator here to ask if they can get an engineer to look at your log, in the meantime do some checks there are some other cases here and while some are common to the cold weather there seems to be no common denominator for all unless a bug in FW, I myself have had no noticeable problems .
It has also been recommended that you be on latest FW and calibrate IMU and gimbal .

Thanks hallmark007,

Yes I did submitted my case to DJI support. Hopefully they manage to come out with something.
I did also updated to latest FW and also did the calibrate process before take off.

GavinThin Posted at 2-2 05:27
Thanks hallmark007,

Yes I did submitted my case to DJI support. Hopefully they manage to come out with something.

Good luck GavinThin .

Zelmani Posted at 2-2 04:26
I downloaded your flight log from Phantomhelp and uploaded it to airdata.com. You can open a free account at their site to upload your flight logs. With the free account, you get basic information on errors during flight, signal quality and ground weather condition. With a paid account, you will have additional information, e.g. on winds during flight and battery statistics.

I have one question: Did you eventually have the propguards mounted when the drop occurred?

Thanks Zelmani,

That's very useful information.

Yes, since I am still a beginner. I do wish to protect my propeller and hopefully I didn't crash my drones in few early flight.
So I do have the proguards mounted.

hallmark007 Posted at 2-2 05:29
Good luck GavinThin .

Thank you.
I will update here if there's any new information regarding this.
Do not wanted this to happen to another other drone owner.

GavinThin Posted at 2-2 05:29
Thanks Zelmani,

That's very useful information.

Did you have payload mode enabled?

davidms Posted at 2-2 05:49
Did you have payload mode enabled?

Hi Davidms,  Thanks for reply.

Sorry, I am still very new to this.
Does the payload mode you mentioned is the maximum altitude and distance restriction ?
I did see a maximum altitude range.
And when I raise my drone , I have reach my maximum altitude level.
But later I lower its altitude before the drop.

Does this affect the flying experience?

GavinThin Posted at 2-2 05:58
Hi Davidms,  Thanks for reply.

Sorry, I am still very new to this.

While using prop guards you have to enable payload mode otherwise the drone does not have enough force to maintain a proper hover.

GavinThin Posted at 2-2 05:58
Hi Davidms,  Thanks for reply.

Sorry, I am still very new to this.

Hi Gavin,

If you reach at low altitude your max height , mayby flying in OPTI mode?

OPTI is activated when # GPS satellites are low or bad reception and there is enough light to fly.

If you like upload your flightlog (in wich this happens) using this link > https://www.phantomhelp.com/LogViewer/Upload/

cheers
JJB

davidms Posted at 2-2 06:00
While using prop guards you have to enable payload mode otherwise the drone does not have enough force to maintain a proper hover.

Hi Davidms,

Noted. From my few previous flight experience it just hover smoothly without a huge problem.
I will double check on this option again.

JJB* Posted at 2-2 06:03
Hi Gavin,

If you reach at low altitude your max height , mayby flying in OPTI mode?

Hi JJB, Thanks for the reply.

I think if it's automatically activated then I might be.
it's my first night flight. I am flying my drone outdoor, GPS should be working nice.

I did upload a flightlog and posted earlier
here's it again ::
https://www.phantomhelp.com/logviewer/4JPL1CX70UIB01HYLR6Q/#