What went wrong? Almost lost it but it ended up in the hedge!

Gkinghrn · Nov 23, 2020

Flight data here ->
Sent drone off to get some video/photos of a liner anchored a couple of miles offshore.

Started with 100% battery ..ended up with a 21 minute flight time before the battery gave out.

I am pretty sure I was bringing it back along the 'red line' to home but looking at the fuller map its clear it was drifting (or i was pushing it) ...

Anyway there still ought to have been enough battery to get this home (began rth at 60% but it dropped quickly).... i eventually took a decision to land it at the closest bit of land and go looking for it ..sadly it lost RC signal before I landed it and it auto landed in a bush ....

Things I think I got wrong were maybe that I didnt open the map view fully to ensure it was coming back efficiently to me and instead relied on VLS and the little map in the corner but I am sure I must had the thing flying sideways maybe and that accounts for it pointing to the home point but not actually going there... anyone advise?

i did get afew nice picture though ....

pilotstever · Nov 23, 2020

What you did not mention was the prevailing winds at the time of the flight. I've seen pilots lose their drones in the ocean by not considering the impact of a headwind on the return.

Tony McDrone · Nov 23, 2020

If you go to the weather part of the report, it shows the direction and speed of the wind. Also, if you look at the battery report, specifically the volt/amps, it shows the battery power lowering immediately when you start the return flight. It appears that you flew out with the wind at your back, and you were flying against the wind on your return flight. You were flying into a 10 mph wind. Flying against the wind consumes more of the drones power. If I am wrong, someone will be along to correct me.

Nice photo of the cruise ship!

pilotstever · Nov 23, 2020

Tony McDrone said:
If you go to the weather part of the report, it shows the direction and speed of the wind. Also, if you look at the battery report, specifically the volt/amps, it shows the battery power lowering immediately when you start the return flight. It appears that you flew out with the wind at your back, and you were flying against the wind on your return flight. You were flying into a 10 mph wind. Flying against the wind consumes more of the drones power. If I am wrong, someone will be along to correct me.

Nice photo of the cruise ship!

I agree but what is missing is the marine wind information. It looks like the deviation began far out to sea.

Gkinghrn · Nov 23, 2020

I agree it'd have been ideal to have flown out against the wind and back with it but in my defence the wind speeds were very low offshore according to Windy and UAV Forecast at the time and standing up on the rocks (120 foot up the wind was negligible) ..... There was no strong wind warning either on the display. MA2 should easily cope with 10mph wind in Sports mode ..

I have a feeling I just got the drones orientation wrong back to me and it was going crabbing home sideways rather than forward ...

I am expecting it to be pilot error but the battery only lasting for 20 mins was a surprise... i began to return about 60% battery which should have been neough to my way of thinking...

Gkinghrn · Nov 23, 2020

pilotstever said:
What you did not mention was the prevailing winds at the time of the flight. I've seen pilots lose their drones in the ocean by not considering the impact of a headwind on the return.

i did but it was low enough for the flight to go on - had I got 30 minutes out of the battery it would have come home fine but if you look at the route it was going parallel to me rather than direct to me for quite a while...

old man mavic · Nov 23, 2020

unfortunately the quoted flight times are in perfect conditions not real world times ,another thing to remember is that Lipo batteries remaining charge drops off a lot quicker as the voltage drops
and you also seemed to be taking a longer route back glad you got it back ok

Gkinghrn · Nov 23, 2020

The longer route back wasnt deliberate

but thankfully i managed to send it to the nearest bit of dry land that I could reach - if nothing else it is a learning experience ...

had to over-ride all the auto stuff otherwise it would have landed a few hundred yards out (or crashed into the cliff edge as it was dropping altitude all the time on auto mode...

Gkinghrn · Nov 23, 2020

For Anyone wanting to see the flight (I stopped recording when I realised power was an issue in an attempt to keep her going as long as possible) here it is ... it wont win any oscars

slup · Nov 23, 2020

Gkinghrn said:
...there still ought to have been enough battery to get this home (began rth at 60% but it dropped quickly)...

...I am sure I must had the thing flying sideways...

Well ... you made 3 mistakes.

The first was that you flew out directly with the wind which is the most common mistake when trying to estimate when it's time to turn around, average wind speeds & direction below.

The second was that you maneuvered the AC in a very odd way on the return leg ... in the beginning of the return you yawed slightly CCW but instead of correct the AC heading back you started to apply right roll together with full pitch forward ... meaning flying sideways to the right ... this applying with additional roll to the right together with max forward pitch became even more towards the end. Here below 3 places on the return leg starting with the yaw input which you countered with applying roll. In the last location you traveled in a 45 degree direction comparing with the AC heading.

And the third mistake was to switch to Sport mode on the return leg ... that mode consume amps to a much higher degree than ordinary P mode. Here below you can see how amp draw (red graph) & battery percentage (blue graph) change when going in Sport mode (blue background color).

You were extremely lucky this time ...

Gkinghrn · Nov 23, 2020

Thank you - yep I was pretty sure I made a few mistakes in the return so this helps me to learn from that .... I think the odd yaw's were trying to get back on the direct line home (from memory) ...

Agree that going out with wind and coming back against not optimal but looking at wind speeds etc and had my control been better it would have come back ok I think so its all down to the other mistakes but the wind against didnt help!

I quite often use Sports mode to bring the drone back quickly are you saying it would cover more ground in P/N mode but just take longer to do so and leave more battery?

TBH at 3 minutes out I was expecting to lose it as i couldnt see how it would come back to my RTH spot in time and hence headed for the nearest bit of land .... it landed about 20 yards from the cliff edge - very very lucky as you say ..

Many thanks for taking the time to look at this for me ..appreciated ..

slup · Nov 23, 2020

Gkinghrn said:
... are you saying it would cover more ground in P/N mode but just take longer to do so and leave more battery?

The most "fuel saving" vs covered ground usually is a speed just a tad faster than P-mode for most of the DJI models ... so finding yourself in distress with a fast draining battery it's much wiser to go full in P-mode if the AC still makes full speed into the wind.

boblui · Nov 23, 2020

Gkinghrn said:
.... I think the odd yaw's were trying to get back on the direct line home (from memory) ...

The best way is zoom out so that both the craft and the home point can be seen on the map, point the craft towards the home point and then apply nothing but just forward stick to bring the craft home. I prefer to use the orientation indicator, the radar-like thing at the bottom center of the screen for the purpose as there is no need to operate on with the map

Gkinghrn said:
I quite often use Sports mode to bring the drone back quickly are you saying it would cover more ground in P/N mode but just take longer to do so and leave more battery?

It depends on the wind speed.

If there is no wind, flying in normal mode does consume less battery per km. E.g. my M2P consumes about 5% in normal mode and 6.2 % in sport mode. However, if the wind speed is over a certain threshold, sport mode will be more efficient. I am doing some test to find out that threshold so I can't tell at the moment.

It's easy to understand why it is so. E.g my M2P can do a maximum air speed ( not ground speed ) of about 68 km/hr in normal mode and may be something like 85 km/hr in sport mode. If there is a head wind of 68 km/hr then it wont be able to move forward at all in normal mode so the % battery per km will be infinite whereas in sport mode, it will still be able to achieve a ground speed of 85-68 = 17 km/hr. The % battery per km will be very high for sure but definitely not infinite so the efficiency will be better.