Lost MM in a wind

PiotrPL · Apr 5, 2020

Good morning Dear Users,

I have lost a Mavic Mini two days ago due to strong gusts of wind. I know you might already be fed up with this kind of threads, but I'm devasted and I'm searching for any data I can use to find the drone, as I believe it's still out there.

It was my second flight, I'm not experienced and I know it's all my fault. I've lost sight of it and I run towards the last seen location, but the drone was all gone.

I'm sending you a trail:

https://www.phantomhelp.com/LogViewer/TWBDPQKYO852OF4P95SH

Could you please predict, taking under consideration all the data listed there, where it could be? I've searched for 5 hours the area nearby and I found nothing. This area, btw, it's small gardens for people living in flats - so it's generally a mess. Yesterday I was sure it's somewhere in the gardens, however right now I'm not so sure.

Maybe with some insights from you I will find the drone eventually.

Thank you very much!

MAvic_South_Oz · Apr 5, 2020

Hey there, sorry about your mishap, and first post and all . . . that is such a common theme here for mini losses.

That's a strange flight log in some ways, the wind must have been strong or channelled / gusty in places.
At 6:51.7 you managed to get 223,119,212,347,550,000,000,000,000,000,000,000.0mph out of your mini for that split second.

From 7:40 - 7:50 it did that deviation north with no stick input, and it looked like the wind was head on in general from generally west looking at the attitude bowl.
You have almost no stick input for a great deal of the last part of the flight (RTH), but the decent headway you made towards home all of a sudden stopped after that 7:50 mark and you were getting blown (I assume) away until end of log, but still showing 47% battery.

This is a job for @slup @sar104 for sure.
With that much battery left, it could have blown a fair way form that last recorded position.

One major saving grace you did right, was not going too high, max under 60' and end of log only 36'.

Good luck, I hope it might have blown that bit further east and come down in clear open country, away from urban region.

Edit, tell us, where did you search for the drone already ?
Would be good to know what area you thought it best to look in.

slup · Apr 5, 2020

OK ... I made a try with this, @sar104 will probably correct me later on

This one isn't a straight forward prediction ... the Mini were probably equipped with propguards as the Payload mode is true in the log. This of course made the AC much more sensitive to wind as the guards act as sails & that's also an explanation to the very fluctuating heading speed. Furthermore the log shows signs in the end that the Mini have started to suffer of the "uncommanded descent" behavior with a number of descents towards the end of the log ... actually it were slowly descending there in the end.

The search area becomes pretty large ... 2 land zones & everything in between them due to the uncommanded descent behavior...

So in scenario 1 if the Mini continued the descent with 0,2-0,5m/s & a heading speed of 3,4-4,5m/s it could have touched down here, the trees in the beginning of the green zone can be a good start to look as the Mini were pretty low & maybe didn't cleared them:

But if the Mini regained the RTH height of 15m later on & the descent stopped it could have continued to fly to this zone:

But as said ... nothing in this incident were reasonable constant ... so all the yellow area between the 2 green ones is also possible depending on the uncommanded descent bahavior.

*EDIT*

Attaching the flight data that shows both the fluctuating drift speed & the uncommanded decents in the end (no stick inputs at all where made during the RTH) ... the marker in the graph corresponds to the red cross (the Mini) on the map.

Meta4 · Apr 5, 2020

PiotrPL said:
Could you please predict, taking under consideration all the data listed there, where it could be?

There are two possibilities, one is easy to calculate (and one isn't).
Looking at the simplest .... If the drone continued the RTH which was already operating:
Your drone was losing height because of the design fault that causes an uncommanded descent so the Mini will sometimes fail to hold altitude.
It was 11 metres above launch height when signal was lost and the land below it was only about 1-2 metres lower.
It's vertical speed while losing height was variable, but averaged 2.5 seconds per metre for the last 5 metres.
To lose another 13 metres would have taken approx 32 seconds.
Speed under RTH was varying between 7.5-9.5 metres/sec and it looks like the other design fault which makes the drone fail to maintain pitch angle.
It would have met the ground 240-300 metres further in the direction it was blowing (just north of east).
Distance could be less if the drone hit a tree or building.

But I've never seen a case of a drone already in RTH losing signal.
It might continue home, but I suspect it's more likely to stop, climb to your RTH height of 15 metres and start RTH again.
If it did that, it's impossible to tell whether the uncommanded descent continued or the new RTH might have interrupted it and it could have maintained height, at last for some time.
If it did maintain height, it would have been blown further backward, but if it was again descending, it would not have blown so far.
There are too many variables to calculate so I'll leave it there.

Cuttack OB · Apr 5, 2020

Wish you luck !!
Was it insured?

PiotrPL · Apr 5, 2020

Answering MAvic_South_Oz, I've searched here. Orange areas are hard to search due to dense bushes (it really doesn't look so nice like on a satellite pic) and the green area I almost know by heart. The brown path is also my "search path" and I got finally to the second orange spot, which is a little bit flooded area, which also doesn't help.

I have also asked people from couple of houses, but nobody seen it.

@Meta4 I've also thought that he could RTH again and I've left a lot of posters in the area of first red circle, so maybe somebody will help.

@slup Man, you did a great job picturing it all, thank you. Tomorrow I will continue my search and I'm full of hope.

Thank you all for answers, I will keep you updated.

PiotrPL · Apr 5, 2020

Cuttack OB said:
Wish you luck !!
Was it insured?

As far as I know the insurance which DJI offers doesn't include losing the drone in the wind.

MAvic_South_Oz · Apr 5, 2020

PiotrPL said:
As far as I know the insurance which DJI offers doesn't include losing the drone in the wind.

From @slup comments in his analysis, there might be a good case for a warranty claim, even without the drone body.

slup said:
Furthermore the log shows signs in the end that the Mini have started to suffer of the "uncommanded descent" behavior with a number of descents towards the end of the log ... actually it were slowly descending there in the end.

Attaching the flight data that shows both the fluctuating drift speed & the uncommanded decents in the end

Maybe @sar104 can get to double check both location analysis, and if it does look like uncontrolled descent.
Then you can be relatively confident to start a conversation with DJI and pursue a replacement.
They have been very good in immediately taking responsibility for minis lost to this fault.

sar104 · Apr 5, 2020

MAvic_South_Oz said:
From @slup comments in his analysis, there might be a good case for a warranty claim, even without the drone body.

Maybe @sar104 can get to double check both location analysis, and if it does look like uncontrolled descent.
Then you can be relatively confident to start a conversation with DJI and pursue a replacement.
They have been very good in immediately taking responsibility for minis lost to this fault.

As pointed out previously, at the end of the recorded flight the aircraft was in slow, uncommanded descent:

If that continued then it will have been on the ground pretty fast, and in the area indicated earlier by @slup. However, it had been descending even faster around 30 seconds previously, and then it recovered and climbed again, and so that may have happened again, in which case it could be anywhere downwind.

PiotrPL · Apr 9, 2020

So,
I searched continuously for another 3 days, couple of hours each, and I still didn't find it. I throughly searched both green zones and put posters all over inhabitatet areas around. For now no news.
I've also contacted guys who fly on powered hang glider and paragliding, but they can't fly because of the pandemic. The sun is shinning over a week now and any prognosis doesn't predict rain, so there's still a chance to find it somewhere.

MAvic_South_Oz · Apr 9, 2020

PiotrPL said:
So,
I searched continuously for another 3 days, couple of hours each, and I still didn't find it. I throughly searched both green zones and put posters all over inhabitatet areas around. For now no news.
I've also contacted guys who fly on powered hang glider and paragliding, but they can't fly because of the pandemic. The sun is shinning over a week now and any prognosis doesn't predict rain, so there's still a chance to find it somewhere.

Have you contacted DJI ?
You should get this replaced under warranty, even without the drone.

PiotrPL · Apr 9, 2020

MAvic_South_Oz said:
Have you contacted DJI ?
You should get this replaced under warranty, even without the drone.

Yes, I've sent them a message. Waiting for answer.

PiotrPL · Apr 16, 2020

Hello again Guys,
DJI has finally replied. Apparentlly it was all wind. And I still didn't find it anywhere.

"
1. The aircraft worked under GPS mode, and it could not respond well to the pilot’s commands due to the strong westerly wind;
2. Flight Time T=01:51, Relative Height H=18.7 m, Distance to Home Point D=91.6 m, the warning of “Strong wind warning. Aircraft unable to return to home automatically. Lower altitude immediately and return to home manually” appeared;
3. T=03:39, H=11 m, D=279 m, there was no pilot’s input, the aircraft tilted 16.4 degrees forward to resist the wind, but it was still blown away at 0.8 m/s, which indicates that there was strong wind affecting the aircraft;
4. T=06:07, H=16.9 m, D=268.4 m, RTH was triggered due to the previous remote signal loss, but the aircraft couldn’t return home normally due to the strong wind;
5. T=08:25, H=10.9 m, D=241.1 m, Battery=47%, the flight record ended when the aircraft was blown away at 3.4 m/s;
6. The take-off position: 50.8640689 20.6594790 and the last coordinate: 50.8640838 20.6629138.

We deeply regret this incident. If you still cannot find the lost device, we offer you a 15% discount on the Mavic Mini device (without remote control and charger). The offer is valid for one month. Please let us know if you want to take advantage of this offer. "

Btw, I still think you did much better job with analisis then DJI. Thank you all for help!

MAvic_South_Oz · Apr 16, 2020

See if an of the flight analysis people can state for you if the uncommanded descent part of the info above warrants you chasing up further.
I think if you can collate the info correctly, save a couple of the charts etc in the flight analysis, and ask them ti reconsider, it might be worth a shot.
Await further reply, perhaps @slup and @sar104 could confirm.

sar104 · Apr 16, 2020

MAvic_South_Oz said:
See if an of the flight analysis people can state for you if the uncommanded descent part of the info above warrants you chasing up further.
I think if you can collate the info correctly, save a couple of the charts etc in the flight analysis, and ask them ti reconsider, it might be worth a shot.
Await further reply, perhaps @slup and @sar104 could confirm.

The uncommanded descent didn't cause the problem, and had it not descended that would not have helped, but it is still an aircraft problem that occurred during this flight, so yes - it might at least be worth a shot at arguing for a larger discount.

PiotrPL · May 7, 2020

Hey Guys! So DJI gave me 15% discount and said it was all my faul, because it's the wind, not the aircraft problem. And, all in all, 15% discount for just the drone+battery was almost the same price as all new basic set in the shop in Poland, so I didn't take it.
Sometimes I'm still going to search for a drone, but no results.
Good day to Y'all!

droneloverair · May 8, 2020

Next time, use the sports mode when you feel that its drifting away to combat gusty winds.

Never use the slow RTH mode. You will drift because of its slow flight home.