Almost lost my Drone

[JamesieBhoy]

Hi Everyone,

New here and not long got my first drone a Mini 2 SE. I have been flying it pretty regularly, almost every day the weather allows here in Scotland.
Had my first scare as I almost lost my drone on it's way home.

I had reached quite a good distance which I normally do but this day I almost had a heart attack. It ran out of battery on it's way home and it was a mission to get it back because of where it landed.

It initiated a RTH at 66% battery. Warm day for here 27c little to no wind but battery just kept depeleting on the way back. It was going down 1% a second.



It got back this far and landed in a very awkward place to retrieve.
My question is why did the battery start going down so rapidly and or why did it say 66% when initiating a RTH. Faulty battery readings?



Quite paranoid now about flying it any distance.

 

[rjwmorrell]

Respectfully, you flew your drone well beyond visual line of sight (15,000 feet? Seriously?) in flagrant violation of The Drone and Model Aircraft Code, and so I'm not sure what you're expecting from comments here but... maybe don't do that and you wont risk losing your drone (or worse)?

Your drone initiated a Smart RTH because at that distance, it calculated that it needed to return home otherwise it would not be able to.

 

[mobilehomer]

Even though the wind might be nonexistant at ground level, at 400' it could be very strong and gusty. You were almost three miles away, it would normally have enough battery for a low battery RTH. The wind was probably a lot stronger than you thought at altitude. If the drone starts low battery landing, you can keep giving it left stick up to maintain altitude and bring it home from the 1700' distance where it did land. Plus, I wouldn't fly that far. I'm sure the VLOS police will be along any minute. Glad you retrieved it.

 

[JamesieBhoy]

Even though the wind might be nonexistant at ground level, at 400' it could be very strong and gusty. You were almost three miles away, it would normally have enough battery for a low battery RTH. The wind was probably a lot stronger than you thought at altitude. If the drone starts low battery landing, you can keep giving it left stick up to maintain altitude and bring it home from the 1700' distance where it did land. Plus, I wouldn't fly that far. I'm sure the VLOS police will be along any minute. Glad you retrieved it.

Yeah you're right. I was just being over zealous and wanting to see how far I could push it. Lesson learned I guess.

 

[Meta4]

My question is why did the battery start going down so rapidly and or why did it say 66% when initiating a RTH. Faulty battery readings?

The only way we can solve that mystery is to investigate the recorded flight data, which will have the information needed to work it out.
The information might help you prevent similar situations.

There are a couple of options ...

1. Go to DJI Flight Log Viewer | Phantom Help
Follow the instructions there to upload your flight record from your phone or tablet.
That will give you a detailed report on the flight data.
Come back and post a link to the report it provides and someone might be able to analyse it and give you an understanding of the cause of the incident.
or
2. Just post the .txt file here
or
3. If you use Airdata, you can view the flight data on Airdata and post a link for the Airdata report

 

[Yorkshire_Pud]

Go to
DJI Flight Log Viewer | Phantom Help
and read the instructions there.
Retrieve the .txt flight log from your phone and up load it to that site then replay the log there.
I suppose you might as well post the resulting URL here as well.
There is an artificial horizon on the replay, watch it and compare the tilt of the drone on the outbound flight with the tilt of the drone on the return flight.
I am pretty sure there will be significant differences.

 

[Meta4]

Your drone initiated a Smart RTH because at that distance, it calculated that it needed to return home otherwise it would not be able to.

That's Low Battery RTH.
Smart RTH is initiated by pressing the RTH button.

 

[Yorkshire_Pud]

If the drone starts low battery landing, you can keep giving it left stick up to maintain altitude and bring it home from the 1700' distance where it did land.

Sorry but I doubt that the OP could have got the drone home if the forced landing triggered a 1700ft from the home point.
The trigger percentage is height dependant, if it triggered at 'only' 400ft the battery must have been fairly well discharged and the available airspeed would have consequently quickly decreased. If it was also fighting a headwind I doubt there would have been the charge left to get it home. In fact I doubt they could have got the drone home even if there was no wind.

 

[JamesieBhoy]

Go to
DJI Flight Log Viewer | Phantom Help
and read the instructions there.
Retrieve the .txt flight log from your phone and up load it to that site then replay the log there.
I suppose you might as well post the resulting URL here as well.
There is an artificial horizon on the replay, watch it and compare the tilt of the drone on the outbound flight with the tilt of the drone on the return flight.
I am pretty sure there will be significant differences.

DJI Flight Log Viewer | Phantom Help

Upload and view flight logs from your DJI drones

www.phantomhelp.com

 

[rjwmorrell]

That's Low Battery RTH.
Smart RTH is initiated by pressing the RTH button.

I stand corrected, yes the low battery RTH, which unlike it sounds, doesn't trigger at a set battery %, but rather when it thinks (correctly in this case) that it's gone too far from Home and may not be able to return.

 

[Yorkshire_Pud]

Yeah

DJI Flight Log Viewer | Phantom Help

Upload and view flight logs from your DJI drones

www.phantomhelp.com

Yeah just look at the artificial horizon, out bound flight 22mph at almost no nose down tilt, return trip, significant tilt.
Actually I am quite impressed the drone did so well.

 

[Meta4]

DJI Flight Log Viewer | Phantom Help

Upload and view flight logs from your DJI drones

www.phantomhelp.com

You flew out at full speed at 400 ft.
To achieve full speed the drone's pitch angle was 7-9 degrees.
That it didn't have to pitch far to achieve top speed is a good indication that the drone had a tailwind assisting on the way out.

Coming home the drone was also able to achieve full speed of around 22 mph, but only by pitching forward at 33-36 degrees.
This indicates that the drone was making the same effort it would in Sport Mode, but still only making Normal Mode speed because it was pushing into a headwind.

That's why the battery ran down quickly coming back and why it went out much further on 35% of the battery, but was unable to get home with the remaining 65%.

 

[mobilehomer]

Sorry but I doubt that the OP could have got the drone home if the forced landing triggered a 1700ft from the home point.
The trigger percentage is height dependant, if it triggered at 'only' 400ft the battery must have been fairly well discharged and the available airspeed would have consequently quickly decreased. If it was also fighting a headwind I doubt there would have been the charge left to get it home. In fact I doubt they could have got the drone home even if there was no wind.

Possibly. Watch this video, Dumb pilot, I know.

 

[old man mavic]

Thankyou @Meta4 ,for once again giving the OP a clear and knowledgeable report.
i hope he realises that he is very lucky, to still have a drone to fly ,and considers finding out about the safe and correct practices, of drone ownership and flight

 

[rjwmorrell]

Looked at the logs. OP is indeed lucky to have recovered the aircraft at all. It lost connection to the RC numerous times. Also, not only was it well beyond VLOS, it was above 400' agl. When it landed, it finally touched ground at -17' relative to its take off point. That means it was at least 17 feet higher than the indicated altitude in the logs at least some of that time.

 

[rjwmorrell]

Thankyou @Meta4 ,for once again giving the OP a clear and knowledgeable report.
i hope he realises that he is very lucky, to still have a drone to fly ,and considers finding out about the safe and correct practices, of drone ownership and flight

Not just lucky to have a drone to fly, but lucky no aircraft or people were harmed. Drone was flown over the 400' agl limit, and being unseen, could have caused numerous close calls with aircraft.

 

[Yorkshire_Pud]

Possibly. Watch this video, Dumb pilot, I know.

I've seen that one before, he was lucky.
In connection with the flight of this thread, even without having seen the log of this flight I stand by what I said.
Having seen the log, if you watch the PH replay the OP was giving the drone full elevator for much of the time from the start of the auto landing and auto landing kicked in a 8% and 3,222ft.
I actually think, all things considered, the OP flew the auto landing phase quite well and it looks as if he chose a safe for others landing site. The outbound flight of course is another matter.

 

[Yorkshire_Pud]

Thankyou @Meta4 ,for once again giving the OP a clear and knowledgeable report.
i hope he realises that he is very lucky, to still have a drone to fly ,and considers finding out about the safe and correct practices, of drone ownership and flight

Not that it matters but what of my post #11?

 

[Yorkshire_Pud]

Not just lucky to have a drone to fly, but lucky no aircraft or people were harmed. Drone was flown over the 400' agl limit, and being unseen, could have caused numerous close calls with aircraft.

Where did he break 400ft AGL?
I don't have google earth and the terrain map I have isn't very good so I can't judge his AGL but, relative to the launch point, the max height I can find is 395ft.

 

[Meta4]

Also, not only was it well beyond VLOS, it was above 400' agl.

Actually it wasn't.
He flew over rising ground that rose approximately 150 feet higher that the launch point.

When it landed, it finally touched ground at -17' relative to its take off point. That means it was at least 17 feet higher than the indicated altitude in the logs at least some of that time.

The landing spot was about 30 ft lower than the launch point, but it's common for the indicated height to drift +/- 20 ft or so over the duration of a flight anyway.