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Approach Chart Comparison

Asked by: 3471 views Airspace, FAA Regulations

Reference KMGM RWY 28 ILS Z (requires GPS) and RWY 28 ILS Y

 

1. The Y version and Z version have the same minimums. Question:

Why are there two different ILS approaches to runway 28 yet both have the same mins.?

2. The Y version offers three options:  S-ILS, S-LOC, and circling. The Z version only allows one option which is the S-ILS.

Question:  Why is the Z version only restricted to one option?

3. The Z version PT has a 7 mile restriction on the outbound leg.

Question: Must you fly the entire 7 miles or can you turn inbound less than 7 miles (example----perhaps only the outbound leg for 4 miles)?

4. Overall,  what advantage does GPS provide for the Z version?

Thank you for the feedback.

5 Answers



  1. John D Collins on Nov 17, 2014

    1. The final approach course is identical for both. The Y uses ground based Navaids to transition from the airway system to the approach. It has an MSA based on the location of MGM. The Z use a GPS and TAA for transitioning to the approach. A TAA and an MSA may not be charted on the same procedure.

    2. Not sure why the Z doesn’t provide a localizer option, but it doesn’t specify the step down fix and doesn’t have a timing table. Without a localizer option, circling to land is not permitted and the approach may not be used for the purpose of filing for an alternate.

    3. The 7 NM is a maximum and the entire distance need not be flown unless the controller specifically clears you to fly to the 7 NM hold. So if you are cleared for the approach from within the 4500 airport side TAA segment “cleared direct ICOTE, cleared ILS Z RWY 28 approach”, you fly the hold with any distance outbound not to exceed 7 NM. If instead the clearance was “cleared direct ICOTE, fly 7 NM outbound leg, cleared ILS Z RWY 28 approach” then you would fly the full 7 NM length.

    4. If you have a GPS, using it to join the approach is simpler than using the ground based Navaids, also the missed approach is simpler.

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  2. Dan Chitty on Nov 18, 2014

    Thank you John for the feedback.

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  3. John D Collins on Nov 18, 2014

    Dan,

    You are seeing more and more ILS procedures being broken into pairs with a Y and a Z. One using conventional navaids to join the approach and the other with a TAA and requiring a GPS. Over time, the number of VOR’s will be reduced and GPS will be the only way to join these procedures. It will get real inconvenient in the future for a /A or /U aircraft as airways and VORs disappear. The FAA is sending a not so subtle message to aircraft that are not equipped with a GPS.

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  4. Dan Chitty on Nov 18, 2014

    John,

    Great point.

    I guess it is no longer more economical for the FAA to no longer maintain VOR stations and marker beacons and more cost effictive to utilize GPS for ILS procedures. I wonder how long it will be when ILS gound equipment is longer supported by the FAA and all that is available are GPS/RVAN approaches.

    Thanks again.

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  5. John D Collins on Nov 18, 2014

    ILS approaches are not in jeopardy. The FAA plans to keep them.

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