Lost Mavic 2 Pro

gerrardhr · May 4, 2019

Hi
Few days ago we were flying a waypoint mission, 5KM, 20km/h.
We did several times 4 km with landing at last position, but this was first with 5 km.
Here is the mission in litchi
Mission Hub - Litchi

At about 1.6km from first waypoint, we lost signal both video and control, pretty much all of the sudden.
We waited 15(and 30) min at the last point to came and land but nothing.
Here are the data from AirData

I walked the complete route, but can not find it. I have flied it with over with phantom,
but no luck.

Any idea, what could be gone wrong, and where could it be?

Thanks and BR

sar104 · May 4, 2019

Can you also retrieve and post the SDK txt log from Litchi » Documents » SDK_logs » FlightRecord?

sar104 · May 4, 2019

The signal quality fell off fast before connection was lost, and so it looks like it was a signal disconnect at that point, rather than an FC or power failure:

The aircraft should have had plenty of battery reserve to complete the mission, but I'm not sure whether the smart battery calculations take into account that the mission did not involve returning to the home point. The smart battery RTH level could have intervened - hence the need for the SDK txt log - it includes the smart battery calculations.

gerrardhr · May 5, 2019

Here it is

sar104 · May 5, 2019

gerrardhr said:
Here it is

OK - that shows the problem I think. The FC doesn't take into account that it is going to be a one-way trip, and it increases the calculated level SMART_BATTERY_landBattery as if it needed to return to the home point. Looking at that parameter, and extrapolating it with distance traveled, shows the following:

It will have aborted the mission and entered RTH at around 780 seconds and 3550 m from the home point.That's about 1150 m short of the last waypoint. It couldn't get back to the home point though, because it was in a wind field of 9 - 12 m/s out of the SW, and so it had a serious headwind on the attempted return. Unfortunately that makes it difficult to figure out how far it might have made it back before autolanding for low battery. I would focus on the section of the flight path back 1 km or so from the estimated RTH point - the green shaded area below:

gerrardhr · May 5, 2019

Thanks for this excellent elaborate.

Short question, when the battery RTH kicked in, Mavic would directly to Home point,
or over the rout back?

My thought's are directly.. Trying to focus on search perimeter.

twotimer · May 5, 2019

gerrardhr said:
Thanks for this excellent elaborate.

Short question, when the battery RTH kicked in, Mavic would directly to Home point,
or over the rout back?

My thought's are directly.. Trying to focus on search perimeter.

As the manual says:

"If the aircraft is further than 2 km or less than 50 m from the Home Point when RTH begins, the aircraft will not retrace the original flight route and instead flies in a straight line to the Home Point."

Peio64270 · May 6, 2019

@sar104 What do you think about this brutal change in pitch, speed and other parameters at 217" of the flight (i.e between waypoints 2 and 3 of the mission)?

sar104 · May 6, 2019

Peio64270 said:
@sar104 What do you think about this brutal change in pitch, speed and other parameters at 217" of the flight (i.e between waypoints 2 and 3 of the mission)?
View attachment 71648

That's at waypoint 2 - it stopped for there for a couple of seconds and then moved on. I had assumed that it stopped to take a photo, although the mission profile linked above doesn't show that. Either way - looks like normal behavior.

webvan · May 6, 2019

Sorry for your loss and hope you find it. Could this have been avoided ? I don't own Litchi yet but I seem to remember something about an option to ignore RTH triggers in Litchi ?

sar104 · May 6, 2019

webvan said:
Sorry for your loss and hope you find it. Could this have been avoided ? I don't own Litchi yet but I seem to remember something about an option to ignore RTH triggers in Litchi ?

Not sure about Litchi, but you can disable smart RTH in the Go 4 app, and that setting will persist unless Litchi overrides it.

gerrardhr · May 6, 2019

I have did today walked path through suggested zone but no luck.

Also did this waypoint mission to video on big screen but also no luck
Mission Hub - Litchi

Here is the video.

If someone recognizes it in the grass please let me know...

Peio64270 · May 6, 2019

sar104 said:
That's at waypoint 2 - it stopped for there for a couple of seconds and then moved on. I had assumed that it stopped to take a photo, although the mission profile linked above doesn't show that. Either way - looks like normal behavior.

Yes. It stopped completely although this was not planed in the mission. This kind of "normal behaviour" reminds me what can happen when the sun shines directly in front of the AC. The drone "thinks" that this is an obstacle and stops. In two or three occasions I had to abort the mission and to come home with Sport mode. If the connection has been lost before this happened, I am almost sure that it had hovered in place till emergency landing for low battery. I asked the OP if this mission was played early morning (which could explain an other stop for sun reason, maybe defintive, this one) but I had no answer till now.

sar104 · May 6, 2019

Peio64270 said:
Yes. It stopped completely although this was not planed in the mission. This kind of "normal behaviour" reminds me what can happen when the sun shines directly in front of the AC. The drone "thinks" that this is an obstacle and stops. In two or three occasions I had to abort the mission and to come home with Sport mode. If the connection has been lost before this happened, I am almost sure that it had hovered in place till emergency landing for low battery. I asked the OP if this mission was played early morning (which could explain an other stop for sun reason, maybe defintive, this one) but I had no answer till now.

The flight time was 6 pm local.