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)

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)

No Spam wrote:
Looking for thoughts out there...

If I have an IFR-certified GPS (terminal, not just enroute), is there any
reason to keep a DME or ADF in the panel? (Other than being able to listen
to am radio or tracking "non-offical" navaids - e.g., am radio stations!)

TIA,

- Don
History does not long entrust the care of freedom
to the weak or the timid. - Dwight D. Eisenhower


You need to be able to execute an approach at your alternate without
reliance on GPS. So, for example, if alternate only has a VOR/DME
approach, you better keep the DME.

Newps wrote:

Not required. You just need to have any fix of the approach in the
database.

Usually I agree with you, but I am confused here.

Why WOULDN'T you need the physical location of the DME in the database,
if you are using the distance from that location as the basis of
whatever decision you were using the DME for?

I know that your answers are always light on the "why" part of the
answer, but just once do you think you can throw the why in? as well as
a reference, because I am unfamiliar with the rationale for your answer.

Dave

KEFD (ellington field) has some DME arcs on its TERPS that are based on
an on-field TACAN. Once upon a time this was a VORTAC, but its been a
TACAN only for at least the past 5 years, prolly closer to 10.

the ILS 17R is one of em. The Govt charts list the TACAN/DME chan as
31.. by having the jepp charts, you can know the freq as 109.4 mhz.

I use the DME routinely just to know distance to the field in non-gps
planes.

Dave


Ron Natalie wrote:

Roy Smith wrote:

If you look hard enough, you can find the occasional NDB-DME station.
I'm not aware of any stand-alone DME ground stations, but I can't
think of any reason why such a thing couldn't exist.

There are probably some TACAN only stations around somewhere, but I'm
not sure any civil procedures would use them.

If you already OWN the equipment, and have the panel space, and it
WORKS.. then there is no reason in my mind to REMOVE IT.

Keep it in case the GPS fairy takes a giant dump on you some day...

Dave

No Spam wrote:

Looking for thoughts out there...

If I have an IFR-certified GPS (terminal, not just enroute), is there any
reason to keep a DME or ADF in the panel? (Other than being able to listen
to am radio or tracking "non-offical" navaids - e.g., am radio stations!)

TIA,

- Don
History does not long entrust the care of freedom
to the weak or the timid. - Dwight D. Eisenhower

Ron,

GPSS is way cool


It's way cool with our 430 and an S-TEC 50 plus GPSS box, too ;-)

--
Thomas Borchert (EDDH)

On Fri, 10 Jun 2005 03:06:48 GMT, Dave S
wrote:



Newps wrote:

Not required. You just need to have any fix of the approach in the
database.

Usually I agree with you, but I am confused here.

Why WOULDN'T you need the physical location of the DME in the database,
if you are using the distance from that location as the basis of
whatever decision you were using the DME for?

I would think it depends on the type of approach. For example, flying
the VOR/DME 23 into 6B6 (Stow, MA) I could either use distance from
MHT, leaving MHT as the waypoint, or I could use the 5.1 distance from
EGORE intersection instead. Either way, the MAP is 25.1 from MHT.

However, it appears that you do need the actual I-whatever ILS device
in the database if you're substituting the GPS for an actual DME on a
ILS/DME or LOC/DME approach. KLN94 manual, 6.2.13 - "Using GPS
Distance as a Substitute for DME on Localizer-Type Approaches" reads
"The FAA allows the use of GPS distance as a substitute for DME on
localizer-type approaches when the DME facility is stored in the GPS
database. The KLN 94 stores DME's associated with localizer-type
approaches using the navaid identifier of the approach. For example,
the DME facility associated with the ILS DME 33 approach for
Burlington International airport is stored in the KLN 94's database as
IVOE."

Dave S wrote:


Newps wrote:

Not required. You just need to have any fix of the approach in the
database.


Usually I agree with you, but I am confused here.

Why WOULDN'T you need the physical location of the DME in the database,
if you are using the distance from that location as the basis of
whatever decision you were using the DME for?

I know that your answers are always light on the "why" part of the
answer, but just once do you think you can throw the why in? as well as
a reference, because I am unfamiliar with the rationale for your answer.

I'm not newps, but if you have some fix that's along the approach in the
database, you can use the distance to that fix, and use mental arithmetic to
calculate the distance to the DME station.

At one time this was more common before the ILS/DME locations were included in
the databases. I don't have a cite, but believe it's all spelled out in the AIM
(assuming US).

Study Advisory Circular 90-94
BT

"No Spam" wrote in message
...
Looking for thoughts out there...

If I have an IFR-certified GPS (terminal, not just enroute), is there any
reason to keep a DME or ADF in the panel? (Other than being able to listen
to am radio or tracking "non-offical" navaids - e.g., am radio stations!)

TIA,

- Don
History does not long entrust the care of freedom
to the weak or the timid. - Dwight D. Eisenhower