Thread: MDA
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Old 27th Jul 2011, 12:27
  #42 (permalink)  
alphacentauri
 
Join Date: May 2006
Location: Australia
Posts: 396
Yes, but the concept of protection on an ILS is different than for an NPA. There is no such thing as a minimum obstacle clearance for an ILS, rather a set of surfaces to which obstacles are not allowed to penetrate. If they do penetrate then you derive a DA from the penetration. This is where lack of understanding from a procedure design point of view is leading people to the false conception that an MDA can be used as a DA, they are two totally different concepts, based around two different types of approach design criteria

If you go around on a CAT II, especially below 161ft it is widely accepted that your wheels may touch the ground. Would you like to do that off an NPA to an aerodrome with no HIALS?
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