My Mavic Mini's at the bottom of a river - what did I do wrong?

Col Pedersen · Mar 16, 2020

Hi all,

I'm new to the forum and "was" a Mavic Mini owner for a week!!

Decided this was a good starting drone to add to my photography hobby and DSLR camera. I head off to picturesque camp site often and a drone would add to the enjoyment of the stays.

But alas! After several practice flights in large ovals, paddocks and a few lookouts I chose to fly along a river we were camped next to. Tree lined, only 5 to 10 meters wide, lots of gentle rapids and a few water holes.

Earlier in the day I had had a flight along the river up form where I was camped - took a great video. Around 5:30 in the evening the sun was setting and the light look nice next to where we had set up the camper.

Took out the freshly charged battery, launched the drone, manoeuvred through some trees (i was getting confident and more skilled by this stage) out over the river...flew down stream 30 or 40 meters, always had a visual.....hovered 1.5mtrs ish off the water and rotated looking in the viewfinder ready to commence the video.....looked up at the drone to see that everything was clear and..... the props simply stop...the drone just fell into the water!!....once it hit the water it tried to take off again...rose slight, I had experienced 3 different emotions in 2 seconds....but...stopped again, dropped and sank!!!...emotion 4!!!

The sight of a 54yo man running to the side of the bank....stripping to the bare minimum and jumping into the water was not pretty. The river was flowing and the water was cold and mercy.....I did not find the unit.....a week old...., 800 bucks, a pissed of operator and grumpy wife!!!

I've read a few other drama's here and followed the instructions to upload the log file;

DJI Flight Log Viewer | Phantom Help

Upload and view flight logs from your DJI drones

www.phantomhelp.com

I can see I was at a negative altitude from the RTH - I took off from a bank and flew down the bank to the river level...nothing I hadn't done earlier in the day from the lookout.

I did not ask it to land....and I had flown (and filmed) similar river situations earlier in the day.....

I've logged a call with the DJI helpdesk but are there any insights from the user group?

and...can you buy the drone on it's own as a spare part?...I have the kit with extra batteries etc.

Any insight would be appreciated,

Col.

MAvic_South_Oz · Mar 16, 2020

I’m at the MEL airport on phone so can’t have a good look at the std phantomhelp flight log, but nothing too unusual there it seems in the way of warnings etc.
Hopefully this will be an uncommanded descent issue and you can get a new mini and battery under warranty.
Wait and see what some of the flight analysis people come back with, fingers crossed for you.
That’s a nice spot, the Brindabellas.

slup · Mar 16, 2020

Col Pedersen said:
Hi all,

I'm new to the forum and "was" a Mavic Mini owner for a week!!

Decided this was a good starting drone to add to my photography hobby and DSLR camera. I head off to picturesque camp site often and a drone would add to the enjoyment of the stays.

But alas! After several practice flights in large ovals, paddocks and a few lookouts I chose to fly along a river we were camped next to. Tree lined, only 5 to 10 meters wide, lots of gentle rapids and a few water holes.

Earlier in the day I had had a flight along the river up form where I was camped - took a great video. Around 5:30 in the evening the sun was setting and the light look nice next to where we had set up the camper.

Took out the freshly charged battery, launched the drone, manoeuvred through some trees (i was getting confident and more skilled by this stage) out over the river...flew down stream 30 or 40 meters, always had a visual.....hovered 1.5mtrs ish off the water and rotated looking in the viewfinder ready to commence the video.....looked up at the drone to see that everything was clear and..... the props simply stop...the drone just fell into the water!!....once it hit the water it tried to take off again...rose slight, I had experienced 3 different emotions in 2 seconds....but...stopped again, dropped and sank!!!...emotion 4!!!

The sight of a 54yo man running to the side of the bank....stripping to the bare minimum and jumping into the water was not pretty. The river was flowing and the water was cold and mercy.....I did not find the unit.....a week old...., 800 bucks, a pissed of operator and grumpy wife!!!

I've read a few other drama's here and followed the instructions to upload the log file;

DJI Flight Log Viewer | Phantom Help

Upload and view flight logs from your DJI drones

www.phantomhelp.com

I can see I was at a negative altitude from the RTH - I took off from a bank and flew down the bank to the river level...nothing I hadn't done earlier in the day from the lookout.

I did not ask it to land....and I had flown (and filmed) similar river situations earlier in the day.....

I've logged a call with the DJI helpdesk but are there any insights from the user group?

and...can you buy the drone on it's own as a spare part?...I have the kit with extra batteries etc.

Any insight would be appreciated,

Col.

Not a fully clear "uncommanded decent" case ... I'm a bit puzzled when you write ... "- the props simply stop...the drone just fell into the water!!....once it hit the water it tried to take off again...rose slight" Did they actually stop or was that just your impression/conclusion as the Mini went down?

Would be good to take a look at the DAT log here also ... the log for this flight have FLY012.DAT in the end & can be found in a subfolder, MCDatFlightRecords, in the folder that contains the TXT logs.

Just before the Mini goes under an uncommanded increase in down speed is recorded, up to 1m/s, together with a 3m descend, just moments later the connection is lost together with MotorBlocked errors ... meaning it's there it hits the water. No real roll or pitch instability is shown earlier in the log (which usually is typical for "uncommanded descent" cases), the Mini mainly does what's commanded.

All this can also be due to tricked VPS sensors, flying so close over the water... looking at all your throttle down commands with no to little change in Waveheight can indicate that the VPS sensor had a hard time to judge height over the water ... no autoland is commanded though.

See if you can attach the DAT log in a new post here so we can verify the behavior of the motors ... & clarify what you mean by writing - the props simply stop...

Messages from the log (marked were it probably make contact with the water surface)

m80116 · Mar 16, 2020

It seems as if it gradually went down... the VPS was fooled in this case, as it is normal when flying above indistinct water.

Your MM is still at the bottom of the river, if I were you I'd ready some inflatable and a fishing net to sieve the bottom of the river.

It can be recovered, both physically and electronically.

You can buy a spare MM but the cost suggests you buy a totally brand new unit and sell the remaining parts or keep them as spares.

Col Pedersen · Mar 16, 2020

m80116 said:
It seems as if it gradually went down... the VPS was fooled in this case, as it is normal when flying above indistinct water.

Your MM is still at the bottom of the river, if I were you I'd ready some inflatable and a fishing net to sieve the bottom of the river.

It can be recovered, both physically and electronically.

You can buy a spare MM but the costs suggests you buy a totally brand new unit and sell the remaining parts or keep them as spares.

Thanks m80116...I spent 1/2 hour combing the river bed with my feet...no luck,the current was to fast and rocks, branches and debris everywhere....I continued looking into the night and morning hoping it may have washed up on the rapids down stream...no luck.

Col Pedersen · Mar 16, 2020

slup said:
Not a fully clear "uncommanded decent" case ... I'm a bit puzzled when you write ... "- the props simply stop...the drone just fell into the water!!....once it hit the water it tried to take off again...rose slight" Did they actually stop or was that just your impression/conclusion as the Mini went down?

Would be good to take a look at the DAT log here also ... the log for this flight have FLY012.DAT in the end & can be found in a subfolder, MCDatFlightRecords, in the folder that contains the TXT logs.

Just before the Mini goes under an uncommanded increase in down speed is recorded, up to 1m/s, together with a 3m descend, just moments later the connection is lost together with MotorBlocked errors ... meaning it's there it hits the water. No real roll or pitch instability is shown earlier in the log (which usually is typical for "uncommanded descent" cases), the Mini mainly does what's commanded.

All this can also be due to tricked VPS sensors, flying so close over the water... looking at all your throttle down commands with no to little change in Waveheight can indicate that the VPS sensor had a hard time to judge height over the water ... no autoland is commanded though.

See if you can attach the DAT log in a new post here so we can verify the behavior of the motors ... & clarify what you mean by writing - the props simply stop...

View attachment 96699

Messages from the log (marked were it probably make contact with the water surface)

View attachment 96700

Hi Slup - I'm amazed that you have such an insight into the workings - thank you.

The DAT file attached.

In regard to my observations;

I had walked over to the bank to see what I was doing and have a good visual on the drone - probably 20 meters away at the time?

The Drone was hovering and from what I could see, the motors stopped, similar to landing with the LH controller control fully extended down. The Drone dropped like a stone 1.5 to 2 meters into the water - it was definitely not a controlled / slow decent and I was not holding the LH controller down.

Once in the water, it was momentarily floating and seemed to try and restart....the props splashed around I "think" it rose a couple of centimetres (maybe just the front) and then the motors stopped again all over in say 2 seconds.....and the drone sank.

It still brings a tear to my eye:-(

Any insight is appreciated,

ta

col.

harle83 · Mar 16, 2020

Wow I’m sorry this happened to you both as a new operator and you had a brand new drone. Water scares the daylights out of me. I’m not so much afraid of crashing as I am letting it get to far away and not having battery power to get back. I’ve only flown water 3 times in the 2&1/2 years I’ve been flying and even that was with my wife right there to be my eyes. Otherwise I woulda lost it I’m sure.

Good Luck with the crazy’s at DJI, our Drone overlords make a
great product but sometimes they get a little presnickety about Warranty claims. I’ve had tech support a couple times and it was hard for me. I have a very severe hearing loss and an almost impossible time with accents. Some southern folks I have issues with, so yeah I get called bigot a lot I just deal with it and try not to get bent over it. Sometimes I get hung up on but other times the good ones I don’t have lots of issues. I truly wish you well.

sar104 · Mar 16, 2020

Col Pedersen said:
Hi Slup - I'm amazed that you have such an insight into the workings - thank you.

The DAT file attached.

In regard to my observations;

I had walked over to the bank to see what I was doing and have a good visual on the drone - probably 20 meters away at the time?

The Drone was hovering and from what I could see, the motors stopped, similar to landing with the LH controller control fully extended down. The Drone dropped like a stone 1.5 to 2 meters into the water - it was definitely not a controlled / slow decent and I was not holding the LH controller down.

Once in the water, it was momentarily floating and seemed to try and restart....the props splashed around I "think" it rose a couple of centimetres (maybe just the front) and then the motors stopped again all over in say 2 seconds.....and the drone sank.

It still brings a tear to my eye:-(

Any insight is appreciated,

ta

col.

The aircraft did descend vertically into the water, as recorded in the IMU acceleration data - the z-axis spike on contact is clear:

Unfortunately your other observations are not confirmed by the data, which indicate that it was simply flying too close to the water, and descended into it. The descent was not commanded, but was not fast:

The motors were running normally until the rear ones made contact with the water surface, which slowed them way down and produced the motor obstruction messages:

The front motors continued to spin at higher speed, which kept them above water until it sank further and went nose up, Titanic-ish:

At that point the data end, not surprisingly.

The cause of the uncommanded descent was likely a slight spike in the VPS height at 154 seconds, leading the FC to try to correct as you see in the slight drop in motor speed at 154 seconds. The FC then corrected again when it detected the descent, but it was too late to avoid impact with the water. One could argue that was an error in the aircraft control, but it's unrealistic to rely on vertical stability of just a meter or so, even without the VPS height measurements having problems over water.

You can certainly make the argument to DJI, but with those data and no aircraft to return to them I would be a little surprised if they are willing to replace it.

MAvic_South_Oz · Mar 16, 2020

Good luck with that Col.
Open a ticket and reply as best you can explaining the TXT and DAT info as above.
Were you recording at the time, and have any cache footage to also send with your claim ?
That would help immensely show it did indeed go swimming and lost.
I'd send those files, and even copies of charts above, so they think you know what you're talking about.
Maybe explain almost word for word what sar104 typed, as it will help collate the data to how the incident went down.
DJI will see it clearer then, and depending on the person reviewing, you might get lucky.
Keep it sweet and cordial is the best bet, and see what happens.

Col Pedersen · Mar 19, 2020

sar104 said:
The aircraft did descend vertically into the water, as recorded in the IMU acceleration data - the z-axis spike on contact is clear:

View attachment 96743

Unfortunately your other observations are not confirmed by the data, which indicate that it was simply flying too close to the water, and descended into it. The descent was not commanded, but was not fast:

View attachment 96742

The motors were running normally until the rear ones made contact with the water surface, which slowed them way down and produced the motor obstruction messages:

View attachment 96744

The front motors continued to spin at higher speed, which kept them above water until it sank further and went nose up, Titanic-ish:

View attachment 96745

At that point the data end, not surprisingly.

The cause of the uncommanded descent was likely a slight spike in the VPS height at 154 seconds, leading the FC to try to correct as you see in the slight drop in motor speed at 154 seconds. The FC then corrected again when it detected the descent, but it was too late to avoid impact with the water. One could argue that was an error in the aircraft control, but it's unrealistic to rely on vertical stability of just a meter or so, even without the VPS height measurements having problems over water.

You can certainly make the argument to DJI, but with those data and no aircraft to return to them I would be a little surprised if they are willing to replace it.

Thank you SAR104......I'm happy to stand corrected, from what I say was the props stop and the drone drop to the water - my interpretation of this is the drone decided to rapidly descend of it own volition....I know I didn't ask it to.

The bit around trying to take off also makes sense looking a these logs.

I'm also very impressed with the level of detail this unit and I'm assuming all DJI units provide - amazing....I wish I owned one still:-(

I have a job logged with DJI that is being investigated - I look forward to their replay.

thanks again

Col.

sar104 · Mar 19, 2020

Col Pedersen said:
Thank you SAR104......I'm happy to stand corrected, from what I say was the props stop and the drone drop to the water - my interpretation of this is the drone decided to rapidly descend of it own volition....I know I didn't ask it to.

The bit around trying to take off also makes sense looking a these logs.

I'm also very impressed with the level of detail this unit and I'm assuming all DJI units provide - amazing....I wish I owned one still:-(

I have a job logged with DJI that is being investigated - I look forward to their replay.

thanks again

Col.

Let us know how they respond.

JSM · Mar 21, 2020

Col, had my Mini for just on 6 months and flew many flights at a number of locations and in varied weather conditions. The Drone always behaved brilliantly and couldn't believe the quality of the camera footage however.............a few weeks ago I was down the Coast (Apollo Bay) out of town late afternoon wanting to get the sunset; flew out (Not over the water) approx 150mtrs, all good however, on the return journey (in RTH) around 60 - 70 mtrs; a black box appeared on the screen (have never seen this before) with a list of errors! "Calibrate the compass" / IMU error and 3 or 4 others which I had no idea what they were !!! (The Drone was calibrated successfully before the flight) whilst looking at all this and trying to get back into the app I lost site of the Drone! Long story short, got into find my drone plus checked on the map, should have landed approx 20mtrs on however very rugged area, searched for a few hours , no luck! Logged everything with DJI and they have been terrific !; will hopefully have an answer next week!

Col Pedersen · Apr 8, 2020

Hi All.....so thought I'd provide an update and resolution. I logged a call with DJI and after a few emails, logs uploaded etc my "loss was assessed and confirmed as a warranty case according to the data analysis" and deemed worthy of a replacement unit.

I've had a lot of experience in consumer and corporate electronic products and I'm running with this is a very positive thing!

I'm now happy that I invested additional $'s into a brand product who are big enough to stand behind their product. The service was reasonably painless, responsive with sufficient communication for me to know the case was progressing.

I was obviously very happy when it was identified a replacement unit was to be provided and today, this unit has arrived.

I'm not saying any other peoples loss / issue will have the same outcome but, I'm happy to call out a great job to DJI.

Now....where to get a pair of floaties for a MAVIC mini!!

Col.