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DH and DA in ILS CAT II and III App

Asked by: 3271 views Instrument Rating

For ILS CAT II or III approaches, which minimum should I follow between DH (determined by RA) and DA?

For example, in this chart of KSEA ILS 16L stating "CAT II RA 176/12 100 DA 500" as the minima for S-16L (http://155.178.201.160/d-tpp/1707/00582I16LC2_3.PDF), which minimum should I follow between RA 176 and DA 500?

 

 

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1 Answers

  1. Best Answer


    Russ Roslewski on Jun 23, 2017

    I am not an expert on Cat II/II approaches.

    However, from the Instrument Procedures Handbook, “CAT II and III approach DHs are referenced to AGL and measured with a radio altimeter.”

    The DA is there as a reference to what altitude you’ll be at when the RA reads the appropriate DH. However, we’re getting into an area of flying that is heavily covered and modified by individual company OpSpecs, so if you’re asking this out of more than just curiosity, it would be best to check with your company’s training department for more information.

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