View Single Post
  #40  
Old April 8th 05, 02:02 PM
Barry
external usenet poster
 
Posts: n/a
Default

It's above TDZE, but DA used to be called DH. There was no "DA" on
approach charts until a few years back. The use of DH is not so much
sloppiness as long term memory in a lot of cases.


It's not as clear as it should be:

- The AIM says that DA replaces DH for RNAV procedures with vertical guidance.

- The FAA's Instrument Procedures Handbook says "DA is currently used on RNAV
approach charts with vertical descent guidance. DA will replace DH for
Category I precision IAPs. MDA and DA are referenced to MSL and measured with
a barometric altimeter. CAT II and III approach DHs are referenced to AGL and
measured with a radio altimeter."

- The Terminal Procedures legend (front of the NACO approach chart books) and
FAR Part 91 still use only DH as far as I can see.