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Lost ILS on approach today

Latech15

Well Known Member
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.
 
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.
 
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?
 
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
 
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.
 
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?
 
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.
 
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.
 
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.
 
It's been a few months since I've flown an ILS with this setup, but the flow I use now is to load the approach (but not activate it) when approach control tells me to what to expect. Assuming you are then vectored for the approach on a heading, just keep the GTN in GPS mode until "cleared for the approach"...then activate it in the GTN. This should put the GTN in VLOC mode and if you have the option set in the GTN, it will send a signal through the ARINC box to the Skyview to switch the CDI to VLOC mode. Press Nav on the Skyview for the intercept. Approach should not clear you until you are within the certified and tested area for a good signal. Here's where it gets tricky with the Skyview. If the signal drops out, it then switches to TRK mode with no warning. You have to really watch it. When I get my prop back, I plan to go up and brush the rust off on these.
 
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?

Only the GPS nav portion uses the ARINC 429 so it wouldn't be in play here.
 
Only the GPS nav portion uses the ARINC 429 so it wouldn't be in play here.

Can't speak to the 650, but the 430W also sends VLOC data, in addition to GPS data, via arinc and most EFIS units use this arinc connection over the analog stuff. I can't imagine the 650 is any different.

Larry
 
Can't speak to the 650, but the 430W also sends VLOC data, in addition to GPS data, via arinc and most EFIS units use this arinc connection over the analog stuff. I can't imagine the 650 is any different.

Larry

Agreed, I have Skyview Classic and 430W, there are NO direct interconnects between them - everything goes through the ARINC 429 box.
 
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?

For the GTN-650 and SkyView install, I configure so it does not automatically shift from GPS to LOC/ILS. I keep this a manual step on the SkyView (a configuration setting). I don?t want the PFD changing without me telling it to do so.

Never had the problem as discribed by the OP.

For the other questions on antennas, my homebrew wingtip VOR antenna picks up the LOC/ILS way beyond practical range - full quieting.

Carl
 
ILS

Any chance there was another aircraft in front of you shooting an ILS? I have had this happen with another guy in front of me on the same approach. The localizer gets blanked out occasionally until I get closer to the FAF.

Not sure this is the case here, just a thought.....
 
There wasn?t anybody else flying at that airport at the time.

I tend to believe that it must be a shadow from the gear I guess. The antenna is under the middle of the plane. The missed approach requires intercepting a vor signal and tracking it a good bit further than the ils iaf and I had no issues with that with the signal coming from the rear of the plane.
 
Another possibility

Could also have been somebody on the ground. Hence the ILS Hold Short line.

But antenna is probably the best theory.

Any chance there was another aircraft in front of you shooting an ILS? I have had this happen with another guy in front of me on the same approach. The localizer gets blanked out occasionally until I get closer to the FAF.

Not sure this is the case here, just a thought.....
 
ILS on gramin

I use the Garmin 430 and I let it switch automatically to the final frequency for inbound ILS. I think you might screw it up by trying to do it manually. When you select approach whether to a fix or Vectors the Garmin loads the final approach course frequency into the standy frequency window. Then as ATC vectors you for intercept there is a point where the Garmin auto switches the frequency into active window and the CDI and autopilot start using it. DG bug has to be manually set to the inbound course and CDI course has to be set correctly. I'd re-read the process before thinking the technology is screwing up. I've seen a lot of weird results when I don't work the 430 correctly.
 
Agreed, I have Skyview Classic and 430W, there are NO direct interconnects between them - everything goes through the ARINC 429 box.

That's what I was getting to...

I and others have had occasional, momentary dropouts of the data coming from the Garmin (430W in my case) via the ARINC box...just a second or two, but enough to a) cause the display to drop the info on the HSI and b) the autopilot to switch to a different mode (HDG, IIRC).

http://dynonavionics.com/cgi-bin/yabb2/YaBB.pl?num=1534712869/8#8

I suspect that's what happened here...a Dynon logfile would help to confirm this.
 
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Yes, now that's entirely possible - I did experience a couple instances of that, it would drop out for half a second and come back, but that was long enough for the Dynon autopilot to go to TRK mode and ignore further inputs unless you restored it back to NAV.

I had it occur once on the RNAV as well, which points to the ARINC rather than the 430W.
 
GNS430/650 When To Switch VLOC

I use the Garmin 430 and I let it switch automatically to the final frequency for inbound ILS. I think you might screw it up by trying to do it manually. When you select approach whether to a fix or Vectors the Garmin loads the final approach course frequency into the standy frequency window. Then as ATC vectors you for intercept there is a point where the Garmin auto switches the frequency into active window and the CDI and autopilot start using it. DG bug has to be manually set to the inbound course and CDI course has to be set correctly. I'd re-read the process before thinking the technology is screwing up. I've seen a lot of weird results when I don't work the 430 correctly.

Regarding the subject of when to switch from GPS to ILS (or VOR) and whether or not to rely on automatic swithcing, here is a pretty good explanation:

https://blog.aopa.org/aopa/2014/05/05/when-to-switch-to-vloc-on-an-ils-or-vor-approach/

Skylor
 
Can't speak to the 650, but the 430W also sends VLOC data, in addition to GPS data, via arinc and most EFIS units use this arinc connection over the analog stuff. I can't imagine the 650 is any different.

Larry

Thanks for the info. I thought all VOR / ILS was over serial.
 
Regarding the subject of when to switch from GPS to ILS (or VOR) and whether or not to rely on automatic swithcing, here is a pretty good explanation:

https://blog.aopa.org/aopa/2014/05/05/when-to-switch-to-vloc-on-an-ils-or-vor-approach/

Skylor

Excellent reference and read. Thanks for posting. In reality, trying to follow a localizer 20 or more miles away can result in a wandering path over the ground until you get closer. I've experienced this many times on the FXE 09 LOC/ILS when turned inbound way out on V511. It's a great way to do some sightseeing over the Everglades.
 
Thanks for the info. I thought all VOR / ILS was over serial.

Always good to spend a little time with the installation manuals. From the Skyview Installation Manual, ARINC section

The SV-ARINC-429 also has a serial input that is designed to provide auxiliary information that ARINC-429 GPS outputs do not provide (such as altitude). SkyView needs this data to consider the input a valid and complete GPS position source.

For a 430/530:

The following are the typical Garmin and SkyView configuration settings when this combination of products is used:
Garmin Settings

"Main ARINC 429 Config" page
In 1: High | EFIS / Airdata
In 2: Unused by SkyView, configure as needed for other equipment
Out: High | GAMA GRAPHICS 429
SDI: Common
VNAV: Enable Labels

"VOR / LOC / GS ARINC 429 Config" Page
TX: High
RX: High
SDI: Common
DME: Unused by SkyView
?MAIN RS232 CONFIG? Page

Chan X (where X is the physically connected port) Output: Aviation
 
Regarding the subject of when to switch from GPS to ILS (or VOR) and whether or not to rely on automatic swithcing, here is a pretty good explanation:

https://blog.aopa.org/aopa/2014/05/05/when-to-switch-to-vloc-on-an-ils-or-vor-approach/

Skylor

There's also a setting *on the Skyview side*

Setting ALLOW AUTO SWITCH: to YES (LABEL 100P) (which is the default, including after upgrading Software to v10.0 or later) allows the 430/530 to tell SkyView to switch from GPS to ILS or back when on an ILS overlay approach - SkyView will display whatever mode the 430/530 tells SkyView to be in. When in this mode and not on an approach, switching between the NAV function and GPS function must be performed from the 430/530.
If you want to manually select GPS and NAV from the 430/530, as you have done prior to v10.0, SETUP MENU > SYSTEM SETUP > ARINC-429 > ALLOW AUTO SWITCH: NO.
 
The antenna is under the middle of the plane. .

Am I picturing this correctly? You have two V configured horizontal wires/tubing running a few inches under the metal bottom of the airframe? Between the two MLG?
I cannot think of a worse location from an RF perspective.
 
It is one wire antenna, not two. But yes, unless I am looking at the wrong antenna. I am not the original builder.

I am going to try this approach again this weekend and watch the gtn 650 while in the default nav page and see if the obs needle shows up there and gives an accurate portrayal of the loc course.
 
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