Altimeter accuracy

On Tue, 08 May 2007 03:38:30 GMT, "Jim Carter"
wrote:

Isn't a radar altimeter required equipment for CAT II and CAT III work? We
were trying to get an aircraft and aircrew certified for CAT II in Seattle
many years ago and I thought that was the reason they had the RA installed.

It is definitely not required for Category A aircraft flying under Part 91
for CAT II. I don't know about other categories.

There was a period of time when I and my Mooney were CAT II qualified and
certified.

The inner marker can substitute for a radio altimeter for 100' DH. The RA
is not necessary at all for the 150 DH. The altimeter and static system
has to have had the IFR check within the past 12 months; and altimeter
correction data must be available to the pilot, including both the scale
error and, wheel height correction if the wheel to instrument height is
greater than 10 feet.

There are a very few CAT II approaches that require a RA for use of the
100' DH, because of absent or siting problems with the IM.

I don't know of any guidance for Category A Part 91 a/c under CAT III, or
if any authorizations have ever been issued for that.
--ron