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Odd Litchi Behavior at Landing
511 8 2018-3-12
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Jerkman
Second Officer
Flight distance : 197054 ft
United States
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I programmed a very basic (3 waypoints) Litchi waypoint mission to fly over our town.  Our town is 1000 feet above sea level.  The launch spot was on a hill about 1300 feet above sea level and the mission ended at a field (also at 1000 feet) on the other side of town.  The Litchi mission would have the drone fly the waypoints at 90 fee above its takoff point (so it was at 1,390 feet).

So, I dropped my son off at the landing field and then I went up to the launch point on the hill.  We were in communication via handheld radios.  I launch the drone (Phantom 3 Standard) and sent it on its way to complete the waypoints mission.  I had Litchi set to "land" upon mission completion and it was about a 9 minute flight.

At about 9 minutes, my son radios that he has visual on the drone.  It came to a point, stopped, started to descend (we aren't 100% sure on this, my son thinks it was starting to descend, but he's not positive), and then took off back towards the launch point.  At this point, I'm nearly having a heart attack thinking we lost the drone!   However, after about 4 minutes, I see the drone back at the takeoff point and recovered it successfully.

So, it appears that RTH kicked off before it landed.  The question is why?  I have 2 theories:
1, Because the takeoff point was so much higher than the landing point, the drone descended 90 feet, realized there wasn't any ground, and then freaked out and decided to head home.
2, The feature that kicks in when the drone realizes that it isn't going to have enough battery to RTH kicked in right as it was starting the landing and that's why it decided to RTH.  I have my doubts about this one, as the drone reported 46% battery life when it made it back to me.

Any thoughts or similar experiences?


2018-3-12
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Peterx
Captain
Flight distance : 1497290 ft
Germany
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T0o the first i can´t say anything. But to to the second,what % did you set the batterys´s low voltage ?
2018-3-12
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Jerkman
Second Officer
Flight distance : 197054 ft
United States
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Peterx Posted at 2018-3-12 04:11
T0o the first i can´t say anything. But to to the second,what % did you set the batterys´s low voltage ?

I don't see that setting anywhere, but I don't think I would have ever changed it (so it would be the default).  Forgot to mention that I did disable "Smart Return to Home" before launch.
2018-3-12
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Peterx
Captain
Flight distance : 1497290 ft
Germany
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Litchi uses the settings from the DJI Go if i remember in right way. Look in to the settings via Go app and verify it with the setting in Litchi.
2018-3-12
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FatherXmas
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Flight distance : 4058619 ft
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United States
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It should be easy to troubleshoot. Make a one waypoint mission where it takes off from a point higher than the waypoint where you expect it to land that you can easily see the entire flight.
2018-3-12
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Jerkman
Second Officer
Flight distance : 197054 ft
United States
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FatherXmas Posted at 2018-3-12 08:48
It should be easy to troubleshoot. Make a one waypoint mission where it takes off from a point higher than the waypoint where you expect it to land that you can easily see the entire flight.

Yep, that's the plan.  Fortunately there is a field directly below the hill where I launch from.  I'm hopefully going to give this a try this weekend.
2018-3-12
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solentlife
Captain
Flight distance : 1087530 ft
Latvia
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So, it appears that RTH kicked off before it landed.  The question is why?  I have 2 theories:
1, Because the takeoff point was so much higher than the landing point, the drone descended 90 feet, realized there wasn't any ground, and then freaked out and decided to head home.2, The feature that kicks in when the drone realizes that it isn't going to have enough battery to RTH kicked in right as it was starting the landing and that's why it decided to RTH.  I have my doubts about this one, as the drone reported 46% battery life when it made it back to me.
Height of landing point above / below take-off point doesn't make any difference and AC should land fine ... I regularly flew my P3S and my later P3P still does .... on significantly sloping ground and often the two points were different.
Strange - as you say you disabled RTH .... maybe this didn't get registered with the AC itself ?

Nigel

2018-3-12
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Amateur Droner
Second Officer
Flight distance : 6411 ft

United States
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If I am not mistaken, DJI GO app can and will override the Litchi app (in regards to the AC settings) if and when it loses signal.
As mentioned above by Peterx, check the DJI settings in reference to RTH.

In addition check to see if DJI app was running in the background ( I uninstalled DJI for my dedicated iPad), and I only use the DJI on my Android phone for calibrations and such.
2018-3-12
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flyhigh69
lvl.4
Flight distance : 75079 ft

United States
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Very interesting hypotheses , especially the 1st one. I want to experiment with this and I will get back at you. So let me make sure I have your info right 3 points. a difference of elevation of launch and landing is around 390 feet. Distance , signal lost? Smart RTH enabled.  Very interesting concept. Im very curious to see the outcome.
2018-3-19
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