Visualizing Circle Holds

(If it was me, I’d click on the “watch on youtube” icon in the lower right corner and select 480p and go full screen — but that’s just me.)

Flying a continuous tight circle pattern around a fixed ground reference point is about the closest thing we can get to parking an airplane in flight. It isn’t too hard to do a lazy orbit around the point, but we want to keep the radius fixed, even if there is a wind. This means that as we fly around the perimeter of the circle we have to continually vary our bank angle and turn at different rates relative to the wind so that our ground track maintains a perfect circle of the desired radius.

Here are some things to look for in the movie:

  • I’ve turned up the turbulence to moderate levels so the small aircraft gets bounced around quite a bit.  Still in the last shot you can see that the flight controller has maintained a pretty tight circle the whole time.
  • This is a 3d model of the new ATI Resolution 3 (a small marinized UAS.)  Stay tuned for more details if you are interested in that sort of thing.
  • FlightGear offers a variety of interesting view points and visualization tools, including smoke and trajectory markers, HUD overlay, animated control surfaces, realistic environments, wind and turbulence.
  • If you look carefully, you can see how the smoke drifts relative to the red/blue trajectory markers.
  • This is all part of a demo package I am putting together that shows things like autonomous-takeoff and landings, a gyro stabilized camera simulation, circle holds around a point, route following, a cool new UAS airframe under development — all mixed in with FlightGear’s wonderful prototyping and visualization features.

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