Why RTH was activated and one more question

[Mladen Matković]

Home point updated. Walking with mini in front of me.
About 100 meters from home point on 20% battery, RTH was triggered by reason unknown.
I was walking under the trees, RTH started to rise mini up to RTH return height which would be disaster.
Left stick down, mini stopped rising and slowly went down.
Battle with RTH continued for 18 seconds when finally came to me that it was RTH I am fighting with.
RTH cancelled, all good.
But there are few strange moments in log :
21.30.2 LEFT STICK DOWN 1.2 M
21.30.6 LEFT STICK DOWN 1.3 M
21.31.0 LEFT STICK DOWN 1.8 M
21.31.4 LEFT STICK DOWN 2.9 M
21.31.8 LEFT STICK DOWN 2.8 M (finally stopped rising)
From there to "21.33.0 TRIPOD MODE" with LEFT STICK DOWN it keeps 2.8 M height.
Log attached.
Please help me to explain why mini jumped up with stick down(under RTH procedure) and what had triggered RTH.
I believe that I didn't triggered it accidentally by RTH button.
Thanks.

 

[old man mavic]

Home point updated. Walking with mini in front of me.
About 100 meters from home point on 20% battery, RTH was triggered by reason unknown.
I was walking under the trees, RTH started to rise mini up to RTH return height which would be disaster.
Left stick down, mini stopped rising and slowly went down.
Battle with RTH continued for 18 seconds when finally came to me that it was RTH I am fighting with.
RTH cancelled, all good.
But there are few strange moments in log :
21.30.2 LEFT STICK DOWN 1.2 M
21.30.6 LEFT STICK DOWN 1.3 M
21.31.0 LEFT STICK DOWN 1.8 M
21.31.4 LEFT STICK DOWN 2.9 M
21.31.8 LEFT STICK DOWN 2.8 M (finally stopped rising)
From there to "21.33.0 TRIPOD MODE" with LEFT STICK DOWN it keeps 2.8 M height.
Log attached.
Please help me to explain why mini jumped up with stick down(under RTH procedure) and what had triggered RTH.
I believe that I didn't triggered it accidentally by RTH button.
Thanks.

20% battery should be the biggest clue have you read the manual on RTH procedure

 

[msinger]

Per the Mavic Mini manual, RTH was auto triggered due to a low battery.

 

[Mladen Matković]

Agree, but activating RTH with 20% battery 100m from home point is not situation in which safe feturn to the home point may be affected. This is at least five minutes remaining for 100m. Intelligent flight battery algorithm has a flaw.

 

[msinger]

100m from home point is not situation in which safe feturn to the home point may be affected

Unfortunately, you cannot choose when that feature is triggered. The DJI Fly app will give you 10 seconds to cancel before the drone starts returning home though. Keep your eyes on the app

 

[Olav van Gerven]

Agree, but activating RTH with 20% battery 100m from home point is not situation in which safe return to the home point may be affected.

The drone will make it's independent decision based on the data available if there is enough power left for a safe return. That decision may different from what you and I would decide.

 

[Mladen Matković]

The drone will make it's independent decision based on the data available if there is enough power left for a safe return. That decision may different from what you and I would decide.

Yes, it seems that 20% is close to absolute trigger, not something calculated from more parameters.
Manual could be more precise.

 

[Olav van Gerven]

Yes, it seems that 20% is close to absolute trigger, not something calculated from more parameters.
Manual could be more precise.

I am not sure, but assuming there is not a fixed level to trigger the RTH on low battery, I can imagine that things as distance and wind (at flight level, not at the ground) may be parameters included in the process.

 

[new2mavic]

Yes, it seems that 20% is close to absolute trigger, not something calculated from more parameters.
Manual could be more precise.

Did you see the message on DJI FLY saying that the battery was low and RTH would be triggered after 10 seconds if not intervened by you ?

I don't know about DJI FLY but in DJI GO 4, you can set the threshold for low battery and whether RTH will be performed if the threshold is dropped through. On top of that the app will compute whether the battery left is sufficient for the craft to go home and trigger RTH if not .

 

[msinger]

I can imagine that things as distance and wind (at flight level, not at the ground) may be parameters included in the process

The Mavic Mini calculates the time it needs to return home every 10th of a second. While DJI doesn't disclose the calculation they are using, it's probably not using anything but the current altitude and distance from the home point. It most certainly doesn't consider the wind speed, so one should never rely on it to get the drone home safely.

 

[Mladen Matković]

did you see the message on DJI FLY saying that the battery was low and RTH would be triggered after 10 seconds if not intervened by you ?

I was walking through the forrest on bad terrain with mini a few meters in front (true VLOS haha). Had to pay attention to mini. Probably mobile sound was not up and warning of RTH activation was not heard.
But it's OK. Lesson learned. In circumstances when VLOS control has proirity over mobile device control, keep mobile sound loud and try not to be around 20% anyway.

 

[new2mavic]

I was walking through the forrest on bad terrain with mini a few meters in front (true VLOS haha). Had to pay attention to mini. Probably mobile sound was not up and warning of RTH activation was not heard.
But it's OK. Lesson learned. In circumstances when VLOS control has proirity over mobile device control, keep mobile sound loud and try not to be around 20% anyway.

If you can share the .TXT and .DAT flight log files in the phone, the reason can be identified with better confidence. Follow this thread to get the files : Flight log retrieval and analysis guide

 

[msinger]

If you can share the .TXT and .DAT flight log files in the phone, the reason can be identified with better confidence

It's linked above. The log shows the low battery RTH feature was activated.

 

[Mladen Matković]

If you can share the .TXT and .DAT flight log files in the phone, the reason can be identified with better confidence. Follow this thread to get the files : Flight l

It's linked above. The log shows the low battery RTH feature was activated.

RTH problem is solved.
There is second problem when under RTH and left stick down, mini jumps up.
It can't be explained with txt log.
But unfortunatelly in my case the following is true:
"In some cases, for reasons not fully explained but possibly mobile-device hardware related, and most often under Android, DAT files are not created and that folder is empty."
DAT logs does exist on SD card but:
"Unfortunately, on recent DJI models (Mavic Air, Mavic 2 and Mavic Mini) the decryption keys are hidden, and so those are not readable except by DJI ".

I think that case can be closed although it would be nice to know reason for jump.
Thanks to all.

og retrieval and analysis guide

 

[Mladen Matković]

Did you see the message on DJI FLY saying that the battery was low and RTH would be triggered after 10 seconds if not intervened by you ?

I don't know about DJI FLY but in DJI GO 4, you can set the threshold for low battery and whether RTH will be performed if the threshold is dropped through. On top of that the app will compute whether the battery left is sufficient for the craft to go home and trigger RTH if not .

DJI Fly has not that feature.

 

[Mladen Matković]

It's linked above. The log shows the low battery RTH feature was activated.

" In some cases, for reasons not fully explained but possibly mobile-device hardware related, and most often under Android, DAT files are not created and that folder is empty "
That's my case.
"Unfortunately, on recent DJI models (Mavic Air, Mavic 2 and Mavic Mini) the decryption keys are hidden, and so those are not readable except by DJI".
DAT files are on SD card but......

Maybe had missed, but manual does not describe remote action consequences when in RTH procedure (and jump happened in RTH ).
Would be nice to know but maybe not worth of effort.
That type of flight is rare.
And in that case I will change RTH from return to home to hoover.
Thanks to everyone.



[/QUOTE]

 

[Steven So]

Mavic Mini calculate the RTH distance and decide the battery level to trigger the event. May be the calculation including the RTH height? I think someone could make a simple test for this by setting a large RTH height and walk with Mini for another fine 100m?

 

[new2mavic]

Mavic Mini calculate the RTH distance and decide the battery level to trigger the event. May be the calculation including the RTH height? I think someone could make a simple test for this by setting a large RTH height and walk with Mini for another fine 100m?

The craft was just 39 ft up when RTH was triggered ......

 

[Steven So]

The craft was just 39 ft up when RTH was triggered ......

I mean... what is the RTH height you set? For example, if the RTH height is set to 300m, the calculation may be "fly up from 39 ft to 300 m, fly to Home point for 100 m and landing from 300 m to ground level."

 

[old man mavic]

the return height would typically be 40m or 120 ft to clear any trees or pylons in the area ,and because the OP was walking close to the drone he was still more than the 20m from home point so the drone would ascend to the RTH that he had set, if he had been near to the home point it would have just tried to land