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Old 05-13-2019, 08:52 AM
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airguy airguy is online now
Join Date: Oct 2006
Location: Garden City, Tx
Posts: 5,389

I'm flying with the standard autopilot settings, and what I see is also an artifact of the signal received for feeding commands to the autopilot. I'm using a 430W to feed the ARINC 429.

For instance on an RNAV coupled approach, it flies like it's on rails, as long as I manage the throttle to keep the airspeed steady. Very tight coupling to the needles. On an ILS it's a bit looser, and frequently approaches 1/4 scale before correcting on the glideslope. The localizer seems to perform a fair bit better than the glideslope and stays tight. A VOR approach, on the other hand, is just about useless and I would say is borderline dangerous to perform as a coupled approach in my airplane - it wanders all over the place. I hand-fly VOR approaches or use Heading Mode and adjust it based on the indicator rather than try to couple them.

My IFR instructor said he has seen the same thing with several other airplanes, and attributes it (rightly or wrongly, I don't know) to a less-accurate signal or slower time resolution of the signal variation on the VOR. The ILS is a little better but the GPS has them both beat.
Greg Niehues - SEL, IFR, Repairman Cert.
Garden City, TX VAF 2021 dues paid
N16GN flying 750 hrs and counting; IO360, SDS, WWRV200, Dynon HDX, IFD440
Built an off-plan RV9A with too much fuel and too much HP. Should drop dead any minute now.

Last edited by airguy : 05-13-2019 at 09:58 AM.
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