I am using APM 1 (firmware 2.33) in a HIL setup with X-Plane 10. Everything works well so far but one thing is strange...

When I set up a waypoint with the LOITER_UNLIM command the plane does as it should and settles into pretty much a perfect circle around the waypoint. However, when I use the FLY TO HERE feature (Flight Data tab, right-click on the map -> Fly To Here) the plane follows more of an oval (sharp turns at either end farther away from the center and almost straight sections closer to the center). Interestingly, when I switch to RTL mode the plane flies home and sometimes settles into a nice circle but other times does the oval. It does not randomly do a circle for one turn and an oval the next, if it is a circle it will do the circle forever and if it is an oval it will do the oval forever. Wether in RTL mode it does a circle or not may be connected with using the FLY TO HERE feature at some point before within the same session/mission.

Any ideas what the problem could be?

Oval vs circle.png

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  • I get a similar thing happening with different modes, Xplane 10, APM Planner 1.1.75. When flying to a waypoint, the track is very windy. However when activating RTL (Set at same altitude as Waypoint). the plane flies in a dead straight line! I can only think that the PIDs are different depending on the type of mode the plane is in. Weird

  • I dont see it consistently. 

    What bothers me most is that I never saw it prior to a week ago.  Every loiter/fly to execution prior was always circular.

    I guess thats the nature of the beast here, the SW is constantly changing with very little indication of what is changing or why, uless you dig for it...

  • Hello Daniel,

    I have been running HIL with X-Plane 9 and I have seen the very same effect.  I have noticed that the oval tracks seem to coincide with altitude gains.  If I send a "Fly to Here" command, with a significantly higher altitude, I see the oval pattern.  Unfortunately, it doesn't happen consistently.  I'm still trying to identify exactly why this is happening.

    This is a critical effect for me, as I have installed a side looking camera on the right side of my (yet to be flown)Skywalker.  My intent is to add code that will send an appropriate PWM to a video switch, chaning the video feed from front to side mounted camera when the aircraft has reached it's commanded "Fly to" point, to observe the area of interest.  With an oval shaped pattern, this technique wont work without pan/tilt, and I really dont want to add that kind of complexity/weight/power draw. 

    I hope someone more knowledgeable chime sin here...

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