Do I need DME or ADF in an IFR-certified GPS panel?

On Thu, 09 Jun 2005 09:55:37 -0400, xyzzy wrote:

Ron Rosenfeld wrote:

On Wed, 08 Jun 2005 14:55:45 -0400, xyzzy wrote:


Doug wrote:


There is, in fact, a requirement to be able to fly the approach at your
alternate without the use of GPS. So having DME will assist you in
finding legal alternates that have VOR/DME approaches. This will allow
you to carry less fuel and more payload. Without DME or ADF, all you
can fly is a VOR approach, and if you have radar, an ILS or LOC (maybe
a few obscure others). Even then some ILS's require DME or ADF.

My home airport has an ILS approach with ADF required, but I just
figured I could use the GPS to substitute for the ADF. From what I
understand of the above, that's true but that also means my airport's
ILS approach is not a legal alternate for someone planning a GPS
somewhere else, do I understand that right? (I'm an instrument
student, still learning this stuff and have found this thread fascinating).


What is your home airport?


TTA, ILS RWY 3.


Some GPS units (GNS480) do NOT require that the the alternate have
something other than a GPS approach. But I'd like to look at your specific
approach to see if it would be legal to fly the ILS ADF approach there.

The other aproaches at TTA are GPS on both 3 and 21 and NDB on 3. So
basically an ADF is kinda important there. If you don't have an
approach certified GPS, you need one.

Well, according to my Jepp chart, TTA is NA for filing as an alternate, so
the ILS (or any other approach) would not be a legal alternate anyway.

For actually flying the ILS, an approach-approved GPS can substitute for
the NDB on that ILS approach.

Since the NDB Rwy 3 approach is not an overlay, an approach-approved GPS
could not fly it legally. This is not a loss as there is an RNAV(GPS) Rwy
3 approach which has lower minimums!

Best,

Ron (EPM) (N5843Q, Mooney M20E) (CP, ASEL, ASES, IA)