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No Glideslope on ILS

Postby gdtrfb58 » Tue Mar 22, 2016 10:44 pm

I have a Garmin GNS 480 (UPS CNX-80) connected via both ARINC and Analog. (Arinc is NAV 1 and Analog is Nav 2)

The ARINC is now functioning normally (reliably starting up and counting) all GPS guided AP functions work. I am able to do RNAV LPV approaches coupled and both needles (glideslope and lateral deviation) appear in the center of the screen and function correctly.

When I start the 480 and it goes through the self test, I believe I am seeing all needles displayed correctly (although I don't think I am seeing the "FLAGGED" display).

When flying the ILS, I am seeing the lateral deviation only and the AP is not taking me down the glideslope. (I do see the "boxes" for the SAP if armed). I am not seeing the Glideslope needle. (even if I "Execute" the approach).

The 480 has a built in HSI and both needles appear normally (i.e.; it is receiving the GS). I tried disabling the Analog (Nav 2) but no change. I haven't tried disabling the ARINC for NAV 1 and flying it on NAV 2.

Any other suggestions?
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Re: No Glideslope on ILS

Postby 330drvr » Wed Mar 23, 2016 2:30 am

You need to have two pair arinc 429 connections to the GRT. One for the GPS and one for VOR/ILS. I have the analog connections but don't even have them turned on. The 480 has two available 429 out connections.
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Re: No Glideslope on ILS

Postby GRT_Jeff » Wed Mar 23, 2016 5:33 am

Since both ARINC and Analog inputs are from the GNS 480, they should both be set to NAV1. The EFIS will automatically use the NAV1 analog inputs if the NAV1 ARINC input fails. The analog inputs for "ILS Tuned", "VOR/ILS Deviations", and "GPS Deviations" will override the ARINC data even if they aren't connected. If those Analog Functions are turned on and you don't have the wires connected, turn them off.

If the EFIS is configured to follow the 480, make sure the mode displayed on the EFIS changes when you change the 480's mode with the CDI button. The text by the needles/scales near the center of the PFD should say "ILS" when in ILS mode (the 480 is set to VOR/ILS mode and an ILS frequency is tuned).

You can confirm the ARINC VOR/ILS data is being received in SET MENU, Display Unit Maintenance, ARINC Status. The VOR/ILS Frequency line should show the frequency set on the 480. If it doesn't there's a communication or setting error. Make sure the rates match (Low/High) and the 480 is set to send VOR/ILS data on one of the ARINC channels.
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Re: No Glideslope on ILS

Postby gdtrfb58 » Wed Mar 23, 2016 9:22 am

Both ARINC channels are connected. They both "count off" in the SET menu. The rates are both set to "Low" (also in the 480)

I set ARINC to NAV1 and Analog to NAV 2, because that is how it is written in the set up manual. In any case, I have tried it with the Analog turned off, without a difference. I will try setting both to NAV 1.

I am not sure where I should see "ILS". I see GS in the standby column of the Vertical AP, but I don't recall seeing "ILS" near the needles. (Yes, I have confirmed changing the 480 CDI to "ILS".
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Re: No Glideslope on ILS

Postby GRT_Jeff » Thu Mar 24, 2016 2:23 am

The "ILS" would be just under the full left deviation mark. This indicates that the deviation data is coming from the ILS and not something else, such as GPS or VOR mode.
ils-needles.png
ils-needles.png (4.02 KiB) Viewed 11704 times
ils-scales.png
ils-scales.png (3.99 KiB) Viewed 11704 times
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Re: No Glideslope on ILS

Postby gdtrfb58 » Thu Mar 24, 2016 3:00 pm

I am pretty sure it still said "GPS" there (even with the 480 CDI on "loc"
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Re: No Glideslope on ILS

Postby 330drvr » Thu Mar 24, 2016 7:31 pm

Just a thought. What are the ARINC 429 outputs configured as in the 480 setup menu? If I remember one should be on GAMA and the other on VOR/ILS. Both should on Low. I can check tomorrow out at the hangar the specific readings if you like.
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Re: No Glideslope on ILS

Postby GRT_Jeff » Thu Mar 24, 2016 10:30 pm

If it still says GPS when the 480 is in LOC, then the EFIS is not programmed to follow the 480's mode. SET MENU, General Setup, "NAV Mode Source" should be External to automatically follow the 480's mode. If you don't want the EFIS to automatically follow the 480's mode, you must manually change the mode to NAV1 yourself to monitor the needles before capture. The ARM LOC or ILS will not change the mode until the capture occurs. You must also push EXECUTE in order for the capture to occur.
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