Towards the end, the MA is running out of power so he lands it in an accessible place (but not his home point) so he can go and retrieve it in his car.
Apparently, as soon as he turned the remote controller off, and lost the link to the MA, it took off automatically and tried to RTH.
Is this correct? If so it’s another lesson learned for me.
It could be quite awkward if you landed it nearby and turned the RC off first and went to pick your MA up and it decides to take off on its own accord to RTH.
His RC wasn’t off (it probably “lost contact” briefly) - because he recorded the data for the take-off and flight to where the RC eventually lost contact with it.
But in essence, had he turned off the RC the same would have happened. (Without the recorded data for the last bit, obviously.)
I’m wondering if it had fully landed … complete with motors powering down … or did he just think it was fully landed but actually hovering just above the ground or with motors still running, as a result of poor/lost signal immediately before it had properly landed.
If the motors had powered down …
a) they won’t start up again on loss of signal and without the RC action to start them.
b) if it “took off again” … a new Home Point would have been set … in that field where it landed … and it wouldn’t have tried to return to the initial Home Point.
Ian’s a member here … two years later we may get his take on it with further time to think what may/may not have actually happened.
He knows his stuff, that’s for sure.
Can’t see why they both won’t do exactly the same thing - whatever that is exactly with current firmware. Phantoms too … they all use the same logic for RTH.
I agree with Dave, in that I think the Air would do the same, and important to remember that the range of the battery is less on the Air, and drops even more quickly. As I found out really loosing mine! If the battery gets too low, even with RTH on, it will start to reduced its height and land, so make sure it’s over dry land!
OK - a few tests done … within the limitations of my garden.
With Landing Precision = On. Take off and fly to other end of garden.
If it lands, the motors power down.
After motors have powered down, the RTH option greys out in Go4, and there’s no response to the RC’s RTH button.
If you re-start motors and take off, a new RTH location is created.
With Landing Precision = Off. Take off and fly to other end of garden.
You can land without the motors powering down (if you’re really quick on the control - otherwise they power down.)
The RTH option does not grey out in Go4. Pressing the RC’s RTH button did bring up the confirmation slider-button. (Too close to Home Point [within 20m] to take off, though, so it just powered down. Need longer garden. )
If you take off again (without powering down the motors), a new Home Point is not created.
(In the confines of my garden and associated overhead telephone lines - I wasn’t inclined to switch off the RC … but I’ll test this in more space.)
Conclusion - perhaps Ian had Landing Precision set to Off.
As I say - that loss of signal bit (or RC switch off) I’ll test when in more space.
It also was in my mind after seeing this old post of mine, a few days ago, and wanting to refresh my mind as to how to land and take-off again without changing Home Point.
Wow! I am always amazed at how this mistake from 2 years ago still generates so much discussion! Yeah, I have analysed it to death and have a very clear idea what happened, and why it’s such an unlikely and unlucky scenario.
First off, yes, the Mavic Pro really is crap in strong wind in the default mode (ie with collision sensors on) as I’ve proved in a YT vid called “Flying your Mavic Pro in Strong Wind”.
That was the start of my issues; I hadn’t enabled Sports Mode (I’d only had the MPro for 2 weeks!). And I stupidly flew off down wind and was trying to fly back into the wind. It slowed right down and that started the panic as it was flying over inaccessible land.
But as for the mechanics of what happened around landing:
Landing Protection was OFF as I usually hand caught the Pro. But this means instead of auto shutting down when it landed, it had to rely on receiving the 3 second ‘DOWN’ command or the CSC (sticks to 5 & 7 o’clock positions).
I always used the 3 second down command but remember I was severely panicking and was already running back to the car, away from the cliff edge as it came into land.
As the Mavic was 120 metres below me, and around 900 metres away from me, I lost connection as soon as I was away from the cliff edge. And that’s the crucial thing; I didn’t check the Props had shut down, and there’s no way they had, because otherwise the RTH wouldn’t have kicked in. As I’ve had to say so many times on the video comments, if the props had shut down, it would have stayed put. If I’d had Landing Protection enabled, it would have also stayed put as it wodul have shut down by itself.
But unstead, despite hitting the grass, the props never got that full 3 seconds down command so they never shut down.
I was recording most of the flight but obviously never got the SD card back, so the only video I got was the video that was streamed and cached to my phone. I stopped recording as I was landing. Didn’t really think about it; I figured there was nothing more to record and remember at that point I was more concerned about heading down from my cliff perch 900 metres away and retrieve the Mavic.
We spent 90 mins searching the park until it got dark. It was only when I opend up the flight logs I saw that straight yellow line showing its final flight path (shown in the video at 0:58) that told me it had taken off again and tried to head back to its RTH home point. As the RTH altitude was 30 metres and it was 120 metres below its take off point, it had risen up 150 metres and then tried to fly back the 900 metres or so towards me, whilst I was already in the car driving down to the park. And unfortunately the area it finally lost its final battery power and landed in is basicaly overgrown scrubland and cliffs.
So that’s the low down. Lost after just 3 weeks of ownership.
Lessons learned:
Fly out up wind and home with the wind.
Trust the RTH function. It disables the landing sensors and allows you to fly faster into the wind. And it works.
Leave ‘landing protection’ On. It’s useful!
Don’t push the battery.
If you’re landing remotely, make sure you use the ‘autoland’ function to ensure the props shut down.
When it’s all going wrong, don’t panic. Think straight and just try and land somewhere safe.
Use the little map in the lower left corner so you never lose track of where your drone is and use the green line to fly back towards you.
Don’t fly with the sun behind you shining on your screen making you miss half the info that’s on there. (see point 7)
Don’t push the battery (so good it needs saying twice)
Hope that hasn’t sent you all to sleep! And hopefully that answers the questions!
maybe it should be Prof. Dave! 
