Napa Airport (KAPC) has an ILS Z 1 approach, but no ILS Y 1. See here. Why isn't this just the ILS 1? The naming rule described in the IPH, referenced here, doesn't explain why this would happen.

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    $\begingroup$ A reason could be Y was cancelled and Z was not renamed, this is usual. But the most probable reason is the scope for numbering is not the airport but the city. See Why is there a "-D" circling-only approach at an airport that does not have corresponding -A, -B, and -C approaches?. $\endgroup$
    – mins
    Sep 28, 2021 at 15:59
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    $\begingroup$ mins, thanks for the link. I don't think there's any other "Napa" in California though. $\endgroup$ Sep 28, 2021 at 16:06
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    $\begingroup$ Yes I realized that just a few seconds ago, but I actually found a Y procedure. $\endgroup$
    – mins
    Sep 28, 2021 at 16:07
  • $\begingroup$ Ah, cool! How do you find historical plates? The faa search only allows current & next options. ETA: never mind. You can manually edit the URL query string to get older dates. $\endgroup$ Sep 28, 2021 at 16:19
  • $\begingroup$ @mins Sounds like an answer? $\endgroup$
    – StephenS
    Nov 21, 2022 at 5:14


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