Lost ILS on approach today

[Latech15]

I have a skyview touch PFD and the Dynon AP coupled to a Garmin gtn650. I was being vectored onto the final for the ILS. As soon as I tuned the ils freq in the Garmin and hit the obs button to have it pick up the ils, my cdi turned green and I saw the offset in the right direction. As I was getting close to the final ?turn to intercept? radio call, the middle section of the CDI that shows the deflection went away. I had the AP on heading > LOC mode so that it would capture the localizer and make the turn inbound, but since it went away, I blew through the final approach course. Once in the other side of it it picked it up again and turned me back inbound.

This same thing happened twice on the same approach, once while established. On that one, the AP mode switched to trk instead of LOC and I had to hit the nav button again to have it follow the LOC. Both of these instances happened between 10-15 miles out. Surely that isn?t too far for the loc to pick up. Both times I was also picking up the GS.

[rvdave]

I would be interested in knowing what kind of antennae you have for nav/ils?

[Mark Dickens]

I have the exact same setup and in flying some practice ils approaches, I've seen the same thing. I have a V antenna mounted to the bottom of my tail cone, and the signal comes and goes that far out. One second you have a good lock on and then as you make a turn, it fades and the the Skyview goes to trk mode with no annunciation or warning. If you aren't watching it, yep, you'll go blasting through the approach course. I think the thing is to use the gps for guidance until you're closer to the FAF and then go to the localizer signal.

[Latech15]

I have not played with it in the plane, but on the Garmin gtn app, it always swaps to vloc automatically. Do you know when that happens? I?d love to keep it on gps until I am close enough to know that I won?t lose it, but are you technically ?established? if you are using the GPS to steer on to the final approach course/localizer?

[Ed_Wischmeyer]

My system is G3X touch with GTN 650, so this may or may not help.

There is a "gate" about 2 miles outside the FAF, and if you don't fly through the gate, the FD / autopilot will stay in heading mode and will not track the ILS. Or something like that.

You're undoubtedly aware that when you load an ILS on the GTN, it puts the ILS frequency into the Standby position. You have to manually activate that frequency. And the GTN will show the ID of what it thinks you wanted tuned, as well as the Morse ID of what it is actually tuned to. I once got real confused when I was attempting an ILS on one runway but the GTN was tuned to the ILS on the cross runway. My checklist now has an additional ILS section with all the reminders.

Ed

[Latech15]

Didn?t know about the gate, but I don?t believe that is what is happening here. Yes, I am tuned to the right nav freq. it gets it for a long time and then loses it momentarily. If it loses it while on the approach course, it goes to track mode. If it is before turning inbound, it just blows through the localizer.

[RV7A Flyer]

When you are talking about the CDI, are you talking about the one on the Skyview? (I assume that the GTN has one, but I don't know that system...I have a 430W as my certified GPS).

I ask because if that's so, I have a possible cause for you. I further assume that the GTN is talking to the SkyView via the ARINC box from Dynon?

[gfb]

Where is your antenna? Could you be shadowing it with the airplane?

I have the G3X/GTN650 setup and have not seen this problem over a few dozen approaches. I use the flat wingtip antenna.

I have not seen the G3C/GTN auto-switch from magenta to green, that would be a really handy thing.

[Ed_Wischmeyer]

In the GTN6XX Pilot's Guide, Rev N, page 6-17, it discusses how the unit will automatically switch to the ILS if the plane is within 1.2 nm laterally of the final approach course, between 2 and 15 nm outside the FAF. Inside of 2 nm outside the FAF, you have to manually switch to ILS guidance and that's done with the CDI button on the Default Nav page.

This all gets back to one of my ideas -- the Feds will let you give transition training for the *airframe* if you have a LODA, but how is anybody supposed to learn the avionics? I'd love to be able to give dual on the G3X Touch system in my RV-9A for people who have those avionics, regardless of airframe, but it's not legal to charge for it. And the insurance would about triple...

In my case, it was trivial to learn the RV-9A, but the avionics took about 100 hours to get proficient at. I was told that was a reasonable number... Lots to figure out that's not in the manuals.

[RV10inOz]

Sounds like a shadow from the plane.

We have a GTN750 and Syview system.....it has NEVER missed a LOC/ILS or VOR signal even at great distance, funny turns.....

You seem to have an antenna location problem. I would be keen to know if not.