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Mavic air 2 flew away in deep sea water - can you kindly review?
314 18 2020-9-9
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szlatan
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Flight distance : 329144 ft
Greece
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Dear all,

Today I had very bad experience with my Mavic air 2. The battery time was constantly changing at the way back and I didn't manage to return it back home.
What is striking is how the flight time remaining deviated over time and specifically after the indication that I should return home. You can see it here: https://youtu.be/AlWXRBocncM

You can find the log of the flight here: https://app.airdata.com/share/nkBkYL

I have already opened a ticket for this case. Your help would be greatly appreciated reviewing what went wrong.
Thank you,

S.


2020-9-9
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Labroides
Captain
Flight distance : 9991457 ft
Australia
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Today I had very bad experience with my Mavic air 2. The battery time was constantly changing at the way back and I didn't manage to return it back home.
What is striking is how the flight time remaining deviated over time and specifically after the indication that I should return home.


You'll see your flight data better here:
https://www.phantomhelp.com/LogViewer/ETKUBMSG94DKABC6V11Y/

It looks like you just continued flying way past what was safe and failed to bring the drone in when you should have.
At 17:11 your battery was down to 15% and you were flying back towards the home point at 11 metres/sec.
At 17:51 your battery reached 10% and Low Battery Autolanding commenced.
You brought the drone back to within 250 metres of the shore at 18:15  with the battery at 7%.
If you had continued to fly toward shore, you would have been there in 23 seconds.

Instead of continuing to the shore, at 18:46 you turned the drone and flew back out to sea as it continued autolanding and the drone eventuially landed in the sea at 20:48 with the battery at 0% and two cells below critical low voltage of 3.3V.

It appears that you just weren't aware of the low battery level, that the drone was landing or where you were flying it.
Your drone didn't "fly away", you flew it away when it was landing due to flying beyond a safe battery level.
I can't see anything misleading about the battery levels that were displayed.


2020-9-9
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DJI Natalia
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Hi szlatan, I'm so sorry for your loss, if the drone is still under warranty, please contact our support team www.dji.com/support to start a ticket for the data analysis, we will help to check what happened and provide the proper resolution. If there is anything else I can assist you with, please feel free to let me know.
2020-9-9
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szlatan
lvl.2
Flight distance : 329144 ft
Germany
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Labroides Posted at 9-9 17:02
Today I had very bad experience with my Mavic air 2. The battery time was constantly changing at the way back and I didn't manage to return it back home.
What is striking is how the flight time remaining deviated over time and specifically after the indication that I should return home.


Thank you for the answer, Labroides

Let me try to answer some of your points.


At 17:11 your battery was down to 15% and you were flying back towards the home point at 11 metres/sec.
At 17:51 your battery reached 10% and Low Battery Autolanding commenced.
You brought the drone back to within 250 metres of the shore at 18:15  with the battery at 7%.
If you had continued to fly toward shore, you would have been there in 23 seconds.

Between 16:27 and 17:51, when I was trying to get back to the shore, it looks like the drone didn't have enough power and therefore speed to move one.
I only got a warning of strong air during my way back after having 10 warnings of not enough force between 16:18 and 16:19, which never appeared on my screen (see also
here for my screen).

Instead of continuing to the shore, at 18:46 you turned the drone and flew back out to sea as it continued autolanding and the drone eventuially landed in the sea at 20:48 with the battery at 0% and two cells below critical low voltage of 3.3V.



This is not true. You will notice that without changing any of my controls from 17:18 onwards the speed decreased to 10-13km/h (from 30+ 2 seconds ago). I didin't turn it back, please check the controls again. It wasn't able to continue straight for reasons that I don't understand.

It appears that you just weren't aware of the low battery level, that the drone was landing or where you were flying it.
Your drone didn't "fly away", you flew it away when it was landing due to flying beyond a safe battery level.
I can't see anything misleading about the battery levels that were displayed.


This might be true about my awareness of the battery level. However bare in mind that this comes with the experience and in addition you will notice that during the way back the time remaining decreased rapidly and it was variating a lot. This gave me a false perception.



Best,

S.

2020-9-9
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szlatan
lvl.2
Flight distance : 329144 ft
Germany
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DJI Natalia Posted at 9-9 19:29
Hi szlatan, I'm so sorry for your loss, if the drone is still under warranty, please contact our support team www.dji.com/support to start a ticket for the data analysis, we will help to check what happened and provide the proper resolution. If there is anything else I can assist you with, please feel free to let me know.

Thank you, Natalia. I have opened a ticket for this matter.
2020-9-9
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Suren
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Labroides Posted at 9-9 17:02
Today I had very bad experience with my Mavic air 2. The battery time was constantly changing at the way back and I didn't manage to return it back home.
What is striking is how the flight time remaining deviated over time and specifically after the indication that I should return home.

Good analysis Labroides
2020-9-9
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Labroides
Captain
Flight distance : 9991457 ft
Australia
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szlatan Posted at 9-9 22:21
Thank you for the answer, Labroides

Let me try to answer some of your points.

This is not true. You will notice that without changing any of my controls from 17:18 onwards the speed decreased to 10-13km/h (from 30+ 2 seconds ago). I didin't turn it back, please check the controls again. It wasn't able to continue straight for reasons that I don't understand.
Sorry but it is true.
You were flying with a non-standard joystick mode so the joystick display you are seeing is false.
I looked at the actual numbers and you steered the drone away from the shore and out to sea.
The drone's speed was reduced because the abttery was so low.
I suspect that it what made you think it wasn't responding normally.
If the speed wasn't reduced, the drone would have fallen from the sky earlier.
2020-9-9
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Eralp SAYGIN
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Flight distance : 668734 ft
Turkey
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Labroides Posted at 9-9 17:02
Today I had very bad experience with my Mavic air 2. The battery time was constantly changing at the way back and I didn't manage to return it back home.
What is striking is how the flight time remaining deviated over time and specifically after the indication that I should return home.

I have the same idea with you, very good analyse
2020-9-9
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szlatan
lvl.2
Flight distance : 329144 ft
Germany
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Labroides Posted at 9-9 23:19
This is not true. You will notice that without changing any of my controls from 17:18 onwards the speed decreased to 10-13km/h (from 30+ 2 seconds ago). I didin't turn it back, please check the controls again. It wasn't able to continue straight for reasons that I don't understand.
Sorry but it is true.
You were flying with a non-standard joystick mode so the joystick display you are seeing is false.

You were flying with a non-standard joystick mode so the joystick display you are seeing is false.
I looked at the actual numbers and you steered the drone away from the shore and out to sea.


Thank you for your answer. How can I check that? I still have a different perception, but again I am not experienced. The link you shared in the beginning doesn't work for me, I get an error.

Also, what do you mean by non-standard joystick mode?
2020-9-9
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JJB*
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szlatan Posted at 9-9 22:21
Thank you for the answer, Labroides

Let me try to answer some of your points.

Hi szlatan,

In addition to the good analysis already given, MA2 with low battery (<20%) will reduce power output to keep craft safely in the air.....with as result that the it will not fly max speed with 100% forward stick.

The autolanding started at 10% batt level, distance to HP 500 meters.
It landed in sea at a distance out of 968 meters!

Even with 100% forward stick (and after that + 100% up stick to stop the down motion) the distance out did not go less but increased!  Why?  beacuse of the maximum pitch down was reduced only to 8 to 10 degrees down at the end of he flight. Too much wind there, so it was flying backwards. see my chart.
to compare ; In N mode with full stick down your MA2 had a speed of 8 - 9 m/s while picthing down to 31 degrees! (batt% > 30%)
About your remark yaw or not ;
At 18m45 MA heads 038.7 degree (=HP heading),  for 1 second yaw left input, MA2 now heads 314.At 18m47.6 you applied right yaw input to 18m52.9, MA2 yawed from 314 to 322, so it made a full turn.

Guess we all know that flying with low battery cell values is not wise to do, but myself did not realize that it has so much effect on the power output, resulting is loosing so much forward speed.

PS1 RC stick mode3 is used (guess most 'pilots' use #2 mode)
PS2 see chart for yaw inputs and yaw heading (purple lines) , cannot make it easier to make it clear.

cheers + Grüß Gott,
JJB





analysis4.png
analysis1.png
2020-9-10
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szlatan
lvl.2
Flight distance : 329144 ft
Germany
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JJB* Posted at 9-10 00:03
Hi szlatan,

In addition to the good analysis already given, MA2 with low battery ( 30%)

Thank you very much for the interesting analysis. It's now more clear to me what went wrong during the last stage. Unfortunately I don't have much experience to realise all these.

What would you have done differently to land (somewhere) safely?

S.
2020-9-10
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Labroides
Captain
Flight distance : 9991457 ft
Australia
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szlatan Posted at 9-9 23:57
You were flying with a non-standard joystick mode so the joystick display you are seeing is false.
I looked at the actual numbers and you steered the drone away from the shore and out to sea.

The link you shared in the beginning doesn't work for me, I get an error.
There's something unusual with that file.
I had to refresh it to make it show the numbers.

How can I check that?
Click the Download CSV to get the actual data.
The joystick inputs are in the last few columns, labelled Aileron, Elevator, Rudder & Yaw.
But because you used mode 3, the column headings are wrong.
2020-9-10
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JJB*
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szlatan Posted at 9-10 00:31
Thank you very much for the interesting analysis. It's now more clear to me what went wrong during the last stage. Unfortunately I don't have much experience to realise all these.

What would you have done differently to land (somewhere) safely?

My pleasure to help,

Answering to your question ; plan your flight such that landing is always with 30% of batt power left, and always always when flying over water.

PS if you are a Window user, use this analyse program > https://forum.dji.com/forum.php?mod=viewthread&tid=203659
easy way to learn about your flight.

I always fly with a screen recorder active, so i can see what i have missed watching the sky and not at the screen app.
After each flying day ; download your flightlog.txt and DAT files on a pc before syncing with DJI servers.
Load each flight into FRAP and see the results (plus batt performance, so easy way of get rid of a faulty battery)

cheers
JJB

2020-9-10
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szlatan
lvl.2
Flight distance : 329144 ft
Germany
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Labroides Posted at 9-10 00:35
The link you shared in the beginning doesn't work for me, I get an error.
There's something unusual with that file.
I had to refresh it to make it show the numbers.

Thank you. It's now clear that have overestimated the performance and did wrong in many instances.
2020-9-10
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DJI Natalia
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szlatan Posted at 9-9 22:23
Thank you, Natalia. I have opened a ticket for this matter.

You're most welcome. Should there any further assistance needed, please feel free to let me know.
2020-9-10
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szlatan
lvl.2
Flight distance : 329144 ft
Germany
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For the record I have managed to recover the aircraft from the bottom of the water. Next time I will be extra careful! Thanks everyone for the analysis/tips.

Cheers
2020-9-10
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JJB*
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szlatan Posted at 9-10 07:57
For the record I have managed to recover the aircraft from the bottom of the water. Next time I will be extra careful! Thanks everyone for the analysis/tips.

Cheers

wow, how did you do that?   not easy to know where it has dropped into the water? or....

just curious i am   ;-)

cheers
JJB
2020-9-10
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szlatan
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JJB* Posted at 9-10 09:38
wow, how did you do that?   not easy to know where it has dropped into the water? or....

just curious i am   ;-)

Scuba diving equipment! Surface wind and water conditions were fine when the incident occurred, therefore the drone sunk only 10-15m away from the last coordinates recorded. Also the depth was only 17 meters so it was easy to locate it.
2020-9-10
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JJB*
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szlatan Posted at 9-10 09:43
Scuba diving equipment! Surface wind and water conditions were fine when the incident occurred, therefore the drone sunk only 10-15m away from the last coordinates recorded. Also the depth was only 17 meters so it was easy to locate it.

Thanks for the update!
2020-9-10
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