True, but the point is now that DH is now measuring height, not
altitude.

DH once upon a time referred to what was actually a decision altitude.

and I may be missing something, but I don't see where the charts refer
to altitudes as heights.

You may be right about Part 91. If so, it probably is the sloppiness
that Roy Smith referred to.



On Fri, 8 Apr 2005 09:02:37 -0400, "Barry" wrote:

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.