Bizarre Litchi "drift" behaviour after final waypoint

[Adrian Cable]

Hi,
I've been experimenting with Litchi creating some waypoint missions (Phantom 3 4K) and have noticed some bizarre behaviour after the final waypoint. It seems that if I set Litchi's "finish action" to fly back to the first waypoint, the drone initially starts flying in the right direction but slowly drifts off course. The drift direction seems to fit with the wind direction, so it's almost as if after reaching the final waypoint, the drone tries to fly back but in F-ATTI mode rather than F-GPS mode. (However looking at the Airdata UAV CSV log of the flight, the aircraft does stay in F-GPS mode.) Then, several hundred feet before getting back to waypoint 1, Litchi reports "mission ended" and the drone just hovers there at this off-track position. I have to manually fly it home at this point. The behaviour is consistent over multiple flights, and also setting Litchi with finish action to RTH does a similar thing. Everything looks good on the drone side: GPS reception is good throughout the whole flight. Compass and IMU are well calibrated.

I've attached screenshots of a test flight from Litchi Mission Hub (with finish action set to "Back to 1") and Airdata UAV, and the CSV of the flight from Airdata UAV, so you can see what I mean. Litchi mission is also here: Mission Hub - Litchi

The workaround is to create a 3rd waypoint near waypoint 1, and set the finish action to hover. The drone flies correctly when set up in this way, with no drift.

Has anyone experienced this? It's very odd. Any light anyone can shed on this would be much appreciated!

-Adrian

 

[gingerbloke]

I'll check this behavior out next time I fly (not great weather here atm) but when I first started using Litchi I read some advice to always make the final waypoint somewhere near your take-off.

 

[Adrian Cable]

Gingerbloke - great, much appreciated - let me know the results.

Yes, I've seen that advice too but I'm not sure it's good advice - or at least it wouldn't be if "back to 1" worked properly! Two waypoints on top of each other, covering each other up, increase the risk that something is set wrong on one of them (e.g. wrong altitude) without it being easily visible. The nice thing about "back to 1" is it means there's one less thing in a mission to set wrong by mistake. But right now it isn't usable.

-Adrian

 

[Adrian Cable]

Any updates on this?

 

[gingerbloke]

No, sorry. It's so windy here recently even the birds are walking......

 

[boykintom]

I'll set up a mission with back to 1 as the last action and see what happens. May be a day or two before I get a chance, though.

 

[Adrian Cable]

boykintom - great, I appreciate it!

-Adrian

 

[boykintom]

Tested it today. After a 2.4 mile round trip, the P4P went right back to waypoint 1 and then hovered as the tablet announced "mission ended". No problems and no drift.