Maybe someone has an idea why are there two separate distance values (marked in blue) for ILS and LOC approaches?
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2$\begingroup$ @DeepSpace What is a LOC DME? And how would you tune that? The ILS DME is tuned with the ILS LOC frequency!? It cannot be the VOR/DME (VNO) either because the difference to the ILS DME (IAV) is 0.9 NM according to the chart. $\endgroup$– BianfableCommented Jul 23, 2020 at 19:54
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$\begingroup$ @Bianfable That's a very good point, I'll try to dig further $\endgroup$– DeepSpaceCommented Jul 23, 2020 at 20:01
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1 Answer
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A very weird case, but each country can do things their own way.
The ILS FAF - GS intercept at 2700' - is 0.2 NM inside the LOC FAF. In the FMC database, the former is coded as FI01, and the latter is VI311. The LOC FAF is also 6.5 DME off of the LOC DME, identifier IAV, which corresponds to 7.4 DME off of VNO (the Vilnius VOR).
The key to seeing this is to consider how you get different distances from the VI312 IF point to the depicted FAF(s). Since VI312 is a single point in space, you can see where the two FAF's are relative to it... the ILS FAF is 0.2 NM farther away (which corresponds to it being 0.2 NM closer to the runway in the other set of blue-circled numbers.
Why the approach designer made the LOC FAF not quite coincident with the ILS glideslope intercept point, is its own question, and I have no insight there. (Totally mystified, in fact.)
answered Jul 23, 2020 at 20:46