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4 Answers

LDA MAP

Asked by: 4443 views Instrument Rating

Looking at a sample LDA approach (KROA), there is a FAF to MAP time table, but also a MM that appears to coincide with the MAP. Which one should be used to identify the MAP when flying the approach?

4 Answers



  1. John D Collins on Mar 28, 2015

    There is a step down waypoint that is part of the procedure if you are not using the GS. It is not located at the MAP. It may be identified according to the approach chart by the I-SZK 4.9 DME, or by RADAR, or by the OM. A GPS may be used in lieu of the DME and identify its position by the waypoint name SKIRT. Regardless, the MAP is located according to the approach chart at JOKNI (GPS) or I-SZK 1.4 DME or by time using the timing table based on GS estimate and 8.3 NM distance from the FAF to the MAP. If one can’t identify SKIRT, then the MDA is 940 feet higher.

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  2. Mark Kolber on Mar 29, 2015

    John, I think he’s specifically asking about JOKNI not the SKIRT step-down.

    David, either way, JOKNI is not a MM. As John said during his answer, it’s an alternate way of identifying the MAP using GPS or DME for those who have neither.

    Which to use if you have a choice? I’ll let you answer that one. Do you use (a) DME or GPS which gives you the precise location or (b) keeping an exact airspeed and constantly estimating your ground speed while you watch the clock which you started the exact second you crossed RAMKE?

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  3. John D Collins on Mar 29, 2015

    Mark,

    He may have meant to ask about JONKI, but he noted: ” also a MM that appears to coincide with the MAP. Which one should be used to identify the MAP when flying the approach?”

    It is an OM and does not coincide with the MAP. I wanted to make that clear and that it was not how to determine the MAP. The MAP point is determined by the methods I listed.

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  4. Mark Kolber on Mar 29, 2015

    I figured he was referring to JONKI as the MM because of it’s location and his description as coinciding with the MAP.

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