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LNAV VNAV and ILS Minma

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Flight Instructor

VRMM(MLE Maldives) RW 36 ILS has DA 329 feet and RNAV(GNSS)  RW 36 LNAV/VNAV is DA 320 feet.

how can RNAV minma be lower than the ILS ??

 

2 Answers

  1. Best Answer


    John D Collins on Feb 06, 2016

    An ILS and an RNAV with LNAV/VNAV minimums are based on different specifications. I don’t have access to either of the approach charts, but the Maldives are close to sea level, so the DA and DH are likely to be within feet of each other, so for this discussion, I assume the DA is also the DH or very close to it. Normal category I ILS is a DH of 200 feet and the lowest LNAV/VNAV DH is 250 feet. When obstacles are close to the runway, the DH is increased to keep the obstacle in the visual segment and to protect for a missed approach where some sink thru the DH is permitted. The two specifications handle this using a different procedure and mathematics, so they produce slightly different results. 9 feet of difference is small and easily accountable by the differences in how the DH is adjusted.

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  2. john kumar on Feb 06, 2016

    Thanks John for your Answer appreciate it

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