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KCLT RW 36R, 36C, 36L, ILS Glideslope Issues


CLTFlyer

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NavDataPro, AIRAC Installed 1511.1 for XPlane 10.30 and XPlane 10 GNS 430/530

XPlane Version: 10.41

Was trying to do an ILS approach the other day to RW 36C at KCLT using the default Cessna 172. RW 36C is on 111.70 with a course of 003 and glide path of 3 degrees, according to the latest approach plates from Flightaware.

As I turned on to final about 5 miles from KCLT with NAV1 tuned 111.70, heading 003, altitude 2500, I was able to pick up the localizer (although its off slightly from the center line, which could be the scenery I have installed for KCLT) but the GS was inoperative (I had the red "GS" flag with the needle in the middle the entire approach).

I found this curious, so the first thing I did was remove the scenery I had for KCLT and tried the same approach again. Same issue. I checked the Local Map and can see the GS positioned to the left side of RW 36C almost coincident with the VASI. So, I tried the opposite ILS approach, 18C, localizer and glideslope worked as expected.

So, I decided to compare the entries in the earth_nav.dat files (default and the one installed by NavDataPro in Custom Data).

Entries (Localizer and Glideslope) in XPlane Default earth_nav.dat for KCLT RW 36R, 36C and 36L:

4  35.22602944 -080.93626861    719 10890  18     355.980 IBQC KCLT 36R ILS-cat-III

6  35.20388972 -080.93302639    725 10890  10  300355.969 IBQC KCLT 36R GS

4  35.23165278 -080.95353694    698 11170  18     355.970 IDQG KCLT 36C ILS-cat-III   (Localizer)

6  35.20254667 -080.95237306    698 11170  10  300355.969 IDQG KCLT 36C GS  (Glideslope)

4  35.22816250 -080.96767167    698 11015  18     355.970 IXUU KCLT 36L ILS-cat-I

6  35.20360722 -080.96693333    698 11015  10  300355.969 IXUU KCLT 36L GS

As expected the true heading for 36C (bold) is 355.970 (KCLT offset is 7.5 degrees west) and the GS is 3 degrees (3 x 100,000) + (355.970)

Now, Here are the Entries (Localizer and Glideslope) from the NavDataPro earth_nav.dat file:

4   35.22603056 -080.93626944    717 10890  25      -4.000 IBQC KCLT 36R ILS-cat-III

6   35.20388889 -080.93302778    717 10890  10  299996.000 IBQC KCLT 36R GS

4   35.23165278 -080.95353611    691 11170  25      -4.000 IDQG KCLT 36C ILS-cat-III

6   35.20254722 -080.95237222    691 11170  10  299996.000 IDQG KCLT 36C GS

4   35.22816389 -080.96767222    732 11015  25      -4.000 IXUU KCLT 36L ILS-cat-III

6   35.20360833 -080.96693333    732 11015  10  299996.000 IXUU KCLT 36L GS

In the Aerosoft data, the true heading for the Localizer is -4, which is I guess technically 356 degrees and the GS is 3 degrees (3 x 100,000) + (-4). For some reason, XPlane dosen't like representing the True heading as -4 because as it appears here, this GS dosen't work....however, if you change the True Heading to 356 and the GS to 300356.000 in the Aerosoft data, then it works fine.

So, I don't know if this is a bug in the Nav data or a bug in XPlane not handling the data correctly. I figured I would post it here first before taking it to XPlane devs as a possible bug. I quickly searched the rest of the ILS/LOC entries in the Aerosoft earth_nav.dat and didn't find any other negative True Headings.

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