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I've found this ILS-Y 26 EPBY approach, where there are two LOC minimums: With D3.0 and w/o D3.0 on Jeppesen chart. On the original AIP charts it says "When stepdown fix not received", but how could we possibly not receive the stepdown fix on LOC (only) approach, if DME is required? Both stepdown fix as well as recommended altitudes table are based on BYD, and there's no reference to BYZ on the final approach?

enter image description here

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  • $\begingroup$ Can you post a link to the AIP chart you mentioned in your question? $\endgroup$
    – user22445
    Sep 18, 2022 at 17:27
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    $\begingroup$ It appears to me that DME is required for the localizer approach. It is required to identify the FAF and the MAP turn back to the VOR. It also seems to be required to correctly fly the CDFA procedure. My only thought is if the DME fails inside the FAF, we could continue and change minimums and try to get radar vectors on the miss. $\endgroup$
    – wbeard52
    Sep 18, 2022 at 19:14
  • $\begingroup$ @757toga ais.pansa.pl/aip/pliki/EP_AD_2_EPBY_6-1-3_en.pdf $\endgroup$
    – Mateusz
    Sep 18, 2022 at 20:05
  • $\begingroup$ @wbeard52 Radar vectors are unavailable at this airport, as it is procedural TWR controlled. $\endgroup$
    – Mateusz
    Sep 18, 2022 at 20:06
  • $\begingroup$ Could this have something to do with using GPS in lieu of DME? Then the with or w/o part would refer to having this point stored in the DB. $\endgroup$
    – Bianfable
    Sep 20, 2022 at 16:21

2 Answers 2

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DME is required equipment for the approach procedure, but note that the LOC DME minimums only apply to the Localizer DME functioning. The missed approach holding pattern references the VORTAC DME, and not the Localizer DME. If the Localizer DME is out you cannot identify the LOC step down fix on the FA segment, but this does not mean the approach is not flyable. The MAP can be identified by using a constant groundspeed and clock method but this method will require increased minimums for (I presume) reasons of safety.

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The approach is an ILS or LOC procedure, which means you are able to fly it if you are receiving the localizer and the glideslope (ILS) or if you are receiving the localizer only (LOC). A localizer does not have DME capability, so there are minimums published if you cannot identify I-BYD D3.0. (ILS DME information comes from the glideslope's location, generally speaking, but it is separate from the glideslope guidance—so it may still be working even if the glideslope is out, or it may not be.)

The procedure requires DME in general because the missed approach has you flying to the point BY633 before turning around and holding at BYZ VOR. The point BY633 is identified as the BYZ 255 radial at 4.7 DME. You need DME to identify it.

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    $\begingroup$ The LOC here on 109.1 does have a paired DME, as shown in the oval with course, freq, morse code, etc. I'm not seeing a way to identify the MAP without DME from the LOC, because the timing is from another LOC DME fix. Puzzling question. $\endgroup$
    – Ralph J
    Sep 18, 2022 at 12:37
  • $\begingroup$ The fact that the DME is paired with the LOC freq doesn't mean anything; the DME antenna (from what I can see of the tiny diagram) is co-located with the GS antenna, as is standard. Both the DME freq and the GS freq are paired off the LOC but they are separate units. Your point about identifying the MAP is much harder to explain away... $\endgroup$
    – randomhead
    Sep 18, 2022 at 12:58
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    $\begingroup$ Consider LOC only approach. You say, that for LOC approach itself you don't need DME , the requirement is there because it's needed for BY633. How do you identify FAP without DME then, and how do you perform the CDFA? $\endgroup$
    – Mateusz
    Sep 18, 2022 at 14:40
  • $\begingroup$ @Mateusz I agree with your comment. You would be unable to to identify the FAF and know when to start your descent from 2300 ft. if you could not identify the 6.5 DME point from BYD. $\endgroup$
    – user22445
    Sep 18, 2022 at 17:18

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