On Thu, 09 Jun 2005 10:44:08 -0400, xyzzy wrote:

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.

Re reading the chart I see that the NDB's location is also identified
with a DME fix on the ILS, so maybe that means ADF is not really
required if you have DME?

No, the NDB is required to navigate to the missed approach fix. I believe
that is because you need PCG -- Positive Course Guidance.

To add a bit to my previous post, IF TTA were useable as an alternate, I'm
sure that an a/c with a GPS receiver certified to TSO146 (WAAS) could use
it without a functioning ADF receiver; but I believe (I'm not sure on this)
that an a/c with a TSO129 box could NOT legally file there as an alternate,
unless that a/c also had a functioning ADF.


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