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6 Answers

Approach Notations and Waypoints

Asked by: 3349 views Airspace, FAA Regulations

Reference KILM---ILS Y/LOC RWY 35: What is the purpose of the waypoint IRULE found along the localizer area?

Reference KILM---ILS Y/LOC/DME RWY 6: What is the reason for the notation "GPS Required" underneath the ILM VOR?  It looks to me that you can simply fly the feeder route from the VOR 226 radial to LURKY using VOR nav. only to cross with the localizer to identify LURKY (no GPS nav.).  Perhaps the ILM VOR 226 radial is not reliable and GPS must be used to fly this feeder route?

Any feedback appreciated.


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6 Answers

  1. Brent on Jan 09, 2014

    I don’t have any insight on the first one (unless the procedure designer was feeling particularly self-congratulatory that day?), but your guess was correct on the second one. In the AF/D for KILM, we find the following (edited for clarity):

    (H) VORTAC 117.0 ILM
    VOR portion unusable:
    186º–219º blo 2,000´
    186º–219º byd 16 NM blo 3,000´
    186º–219º byd 21 NM
    220º–273º byd 5 NM blo 17,500´
    274º–314º byd 5 NM
    315º–164º byd 5 NM blo 8,000´

    Since the feeder route requires traveling 17.2 nm on R-226, we’re not able to rely on radio navigation alone.

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  2. Dan Chitty on Jan 09, 2014

    Brent, thank you for the feedback.Very helpful.
    Lesson learned for me is to look at the AF/D more closely for such details. However, it would be helpful if the chart makers would put a note in the briefing section that reads ” ILM VOR radial 226 unusable to identify LURKY”.

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  3. Dan Chitty on Jan 09, 2014

    Correction: ILM VOR is not used as a cross radial with the localizer to locate LURKY.
    Thank you again Brent.

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  4. John D Collins on Jan 09, 2014


    For the VOR, all this is in the NOTAMS as well.

    Regarding the ILS or LOC RWY 35, it was broken into two procedures, one a Y version and the other a Z version. The Z version has an RNAV style TAA associated with it and the fix IRULE is the center IAF/IF. It is designed to be transitioned to using RNAV or GPS methods and not using ground based Navaids, particularly when the nearby VOR is next to useless. The Y version uses ground based Navaids, which is the NDB IL and so either an ADF is required or Radar may be used. IRULE is charted on both procedures, but does not have a charted purpose on the Y version. Both the Y and the Z use the same ILS for the final approach, but note that the Z has a DH of 211 feet whereas the Y has a DH of 210 feet. This anomaly has to do with the difference in the missed approach path, the Y is a left turn back to IL and the Z is a straight ahead climb to ILUXY. The latter path is 1 foot higher due to an obstacle penetrating the missed approach climb surface, forcing the DH up by the 1 foot, probably the 73 foot obstacle on the chart.

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  5. Dan Chitty on Jan 09, 2014

    Thank you John.

    By the way, any idea what the purpose is of the waypoint IRULE found along the localizer area?
    Reference KILM—ILS Y/LOC RWY 35

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  6. Dan Chitty on Jan 09, 2014


    Disregard my most recent post asking about IRULE. I see you clearly explained above. My internet is slow today and this page did not load properly earlier.

    Thanks again. Much appreciated.

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