Mavic Mini Signal Loss Causing Loss of Aircraft over Water

[Willc66]

I recently purchased my first drone - a refurbished Mavic Mini. However over the weekend I unfortunately lost it over a lake caused by a loss of signal.

I had taken the aircraft off on full battery with a return to home location set. After taking a short video the feed on the DJI fly app began to lag before a notification that signal had been lost between the aircraft and RC appeared 5 seconds later. In response the application informed me the aircraft would return home after 11 seconds. This did not happen and the aircraft was lost. There were no obstacles present and conditions were perfect with no wind.

I have retrieved and uploaded the flight log and retrieved the following notifications:


Any advice or insight to what caused this failure would be greatly appreciated.

 

[boblui]

Can you post the flight log ?

 

[Willc66]

Can you post the flight log ?

Updated with log

 

[Olav van Gerven]

Normally, RTH is triggered when you have a signal-loss for a certain time. The first thing I would do in your case is to check what the RTH settings were (if still possible). If it was "hovering", then your mini might have waited above the water untill the batteries almost died to get into a forced landing (which you don't see in the log because you had no signal anymore.)

 

[Willc66]

Normally, RTH is triggered when you have a signal-loss for a certain time. The first thing I would do in your case is to check what the RTH settings were (if still possible). If it was "hovering", then your mini might have waited above the water untill the batteries almost died to get into a forced landing (which you don't see in the log because you had no signal anymore.)

Thanks for the help! I don't think I can check the RTH settings now - although I had successfully used the RTH function on the flight prior. I also checked the last location on a boat to see if I see or hear it hovering.

 

[Olav van Gerven]

How long after losing the connection where you at the spot? At the time of the disconect, you had just under 90% battery, depending on the circumstances , you had some time, but not much.

 

[boblui]

I am afraid you have set the fail-safe action to "landing" so it landed when the connection was lost :



This is the setting of my Mini :

 

[iaincaradoc]

If I'm reading this correctly, your homepoint was at Rossclare Jetty, and you flew 366m NW curving slightly to the north at an altitude of 19.6m.

Which would put a *lot* of trees and foliage directly in your transmission path between your controller and your mini. RF and foliage don't mix well. And if I've got this correct, this would have been your view, with your drone disappearing from left to right behind that stand of trees on the shore.

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[Willc66]

I am afraid you have set the fail-safe action to "landing" so it landed when the connection was lost :

View attachment 111623

This is the setting of my Mini :

View attachment 111624

I had not changed this. By default I was under the impression the fail safe should be return to home. It had also given me the message it was returning to home if connection was not restablished.

 

[Willc66]

If I'm reading this correctly, your homepoint was at Rossclare Jetty, and you flew 366m NW curving slightly to the north at an altitude of 19.6m.

Which would put a *lot* of trees and foliage directly in your transmission path between your controller and your mini. RF and foliage don't mix well. And if I've got this correct, this would have been your view, with your drone disappearing from left to right behind that stand of trees on the shore.

Google Maps

Find local businesses, view maps and get driving directions in Google Maps.

goo.gl

I had walked to the end of the jetty so I had a clearer line of sight across the water

 

[Willc66]

How long after losing the connection where you at the spot? At the time of the disconect, you had just under 90% battery, depending on the circumstances , you had some time, but not much.

I would say I was at the last location with 25 minutes

 

[iaincaradoc]

I had walked to the end of the jetty so I had a clearer line of sight across the water

So you had a clear visual on the Mini when you lost signal?

 

[Willc66]

I had not changed this. By default I was under the impression the fail safe should be return to home. It had also given me the message it was returning to home if connection was not restablished.

Thanks for spotting this.
After doing some investigation into previous logs it appears the aircraft was by default set to Hover however changes to Landing during the first flight. I did not change this manually and have read a few accounts of it change without input. Here is the log of my first flight where the change occured. DJI Flight Log Viewer - PhantomHelp.com

 

[Olav van Gerven]

25 minutes after loss of signal could have been just a few minutes late. If I remember correct, the flighttime of the mini is said to be ca. 30 minutes, depending on the conditions. You lost connecton after ca. 3 minutes add 25 and you might come just in the critical battery level.

 

[slup]

25 minutes after loss of signal could have been just a few minutes late. If I remember correct, the flighttime of the mini is said to be ca. 30 minutes, depending on the conditions. You lost connecton after ca. 3 minutes add 25 and you might come just in the critical battery level.

No, that didn't happen unfortunately ... the failsafe action was set to "land" so 11 sec after lost connection the Mini started to land & being just 19m above the water it took only 10-11sec before it was game over.

*Edit*

It's a bit fuzzy in the manual ... landing protection is activated during SMART RTH only, & the manual says that a pilot confirmation is needed if the landing protection is off when the AC reaches 0,5m ... perhaps some Mini owner can confirm how it works during failsafe RTH landing.

 

[Deleted member 103366]

That I can see the logs say the failsafe action was landing, if you want to check it down load CsviView and give your flight log to it. Once it has processed the log click on the "empty" arrowed and then drag the'window bottom' up to allow the menus below to expand, then click on "failSafeAction" & "goHomeHeight [m]" and "update plot".
Drag the 'window bottom' down to reveal the full sized chart.
That said, and I have just tried this, the mini may reject the landing site even if in failsafe, it then seems to hover awaiting instructions.
Following from another thread I suspect it will continue to hover until the battery smart RTH trips and then it will attempt to return home.
Your RTH height seems to have been 117m.
Would that clear everthing in a straight line path shown in yellow in the attached?
From what I see there doesn't seem to have been much wind, if that is correct and if it rejected the landing site, then it probably hovered almost on the spot prior to RTH'ing.

The phantompilots view of you logs is DJI Flight Log Viewer - PhantomHelp.com
PS
I think you can NOT switch landing protection off on the mini so it is always on. I recollect it can be fooled by taping over the sensors but that is probably not applicable in this case.

 

[Willc66]

So you had a clear visual on the Mini when you lost signal?

That I can see the logs say the failsafe action was landing, if you want to check it down load CsviView and give your flight log to it. Once it has processed the log click on the "empty" arrowed and then drag the'window bottom' up to allow the menus below to expand, then click on "failSafAction" & "goHomeHeight [m]" and "update plot".
Drag the 'window bottom' down to reveal the full sized chart.
That said, and I have just tried this, the mini may reject the landing site even if in failsafe, it then seems to hover awaiting instructions.
Following from another thread I suspect it will continue to hover until the battery smart RTH trips and then it will attempt to return home.
Your RTH height seems to have been 117m.
Would that clear everthing in a straight line path shown in yellow in the attached?
From what I see there doesn't seem to have been much wind, if that is correct and if it rejected the landing site, then it probably hovered almost on the spot prior to RTH'ing.

The phantompilots view of you logs is DJI Flight Log Viewer - PhantomHelp.com

Thanks for taking the time to look into this. A height of 117m would have definitely cleared any obstacles along that path. I did have someone wait at the home point for over an hour with no luck.

 

[Deleted member 103366]

It might be worth having a look along the flight path just in case it ran out of battery whilst RTH'ing. I haven't experimented to see how well the smart RTH calculates things for a distant return.

 

[boblui]

After doing some investigation into previous logs it appears the aircraft was by default set to Hover however changes to Landing during the first flight. I did not change this manually and have read a few accounts of it change without input. Here is the log of my first flight where the change occured. DJI Flight Log Viewer - PhantomHelp.com

Interesting ......

It was not really a flight because the craft has never left the ground and the motors have run for just 1.5 sec. The log clearly shows that the fail-safe action was changed from "Hover" to "Landing" 0.5 sec after the motors were started. I have heard similar reports for Air 2 from local pilots but have never seen any evidence.




I think this is a software bug. Suggest to file a claim to DJI if the drone is still under warranty. I hope the .DAT file is still there because it should contain info. on whether the change was done manaully.

 

[Deleted member 103366]

Bobblui, where EXACTLY in the DAT file do we look for the information relating to "because it should contain info. on whether the change was done manaully." and WHAT do we look for?

I ask because when I went to do the experiment mentioned in post #16, my the failsafe response was set to hover.
I thought I had been careless as recently I was experimenting with whether or not the battery-smart-return would override a failsafe setting of hover, it does btw. I thought that maybe I had left the setting at hover.
Your post is thus somewhat alarming !