Overshooting heading in nav mode only

Solana

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Mar 26, 2017
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Tech support,

Here is an interesting behavior. I fly an RV10 with Dynon Skyview HDX, currrent software. My autopilot is pretty well tuned and rolls out on heading pretty accurately when using heading mode. However, when in nave mode and performing a turn in the flight plan, it overshoots heading by about 5 or 6 degrees, then corrects back. This is using the Garmin 650 for navigation, and the Garmin is set to anticipate turns, which it does (but still overshoots heading). Any thoughts on why this is happening?

Thanks,

Rick Solana
 

Dynon

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So the first question - when you're seeing these behaviors is the nav mode flag in the AP top bar indicating GPSS (gps steering?)
 

Dynon

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So in that case, we're following roll guidance that the GTN is generating. In other words, the GTN is commanding the aircraft pretty directly. What are your roll limits set to?
 

kellym

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The Dynon autopilot roll limit is set to 25 degrees.

I fly an RV-10 with essentially the same setup, although older variety of screens. I would suggest lowering your roll limit to about 22 degrees. I think you will get better performance by limiting the AP to essentially a standard rate turn.
 

Solana

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Well, turning down the roll limit had no effect on the behavior. To summarize:

- when following the Garmin GTN650 navigator on a GPS flight plan, it overshoot the new heading my 5-8 degrees. It then turns back on course (probably because it is then in some heading tracking mode).
- Tracking a GPS course is flawless.
- Turning when commanded by the heading bug in heading mode (Not GPS navigation) is also perfect.

What can I check next?

Thanks!
Rick
 

Dynon

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Can you take a video that includes both the GTN and SkyView screens and send it to us at support at dynonavionics dot com?
 

Solana

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I have sent the video of the the Skyview and GTN screens as requested.
the result was a suggestion to talk with Garmin, which I am doing. They do not think it is in the 650 and are suggesting I talk with Dynon!

More importantly, I have some useful new info. I flew the plane using the Skyview GPS and the rollout behavior is perfect, just like when using the heading bug.

This leaves me thinking that the problem is either the Garmin 650 or the ARINC box. Do you think it could be the ARINC box??
 
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