GPS Question

I thought I understood this, but maybe not. GPS systems were certified
for approaches after I got my instrument ticket, so my knowledge is
more anecdotal than from actual training.

Can an approach-certified GPS be used to substitute for NDB and DME
during an approach (or even en route)? What if the approach says ADF
Required or DME Required? My understanding of the AIM is that you can
only use the GPS as a substitute when there is a published GPS overlay
for the approach.

(My question is about the legality and not about whether you'd be close
enough.)

On 03/09/06 11:35, rps wrote:
I thought I understood this, but maybe not. GPS systems were certified
for approaches after I got my instrument ticket, so my knowledge is
more anecdotal than from actual training.

Can an approach-certified GPS be used to substitute for NDB and DME
during an approach (or even en route)? What if the approach says ADF
Required or DME Required? My understanding of the AIM is that you can
only use the GPS as a substitute when there is a published GPS overlay
for the approach.

(My question is about the legality and not about whether you'd be close
enough.)


The AIM has a section devoted to the use of GPS in lieu of ADF and DME,
which will answer your question, and much more ;-)

Go to section 1-1-19, and look for "Use of GPS in lieu of ADF and DME".

The short answer is yes, you can use GPS as a replacement for ADF and DME
unless the navigational station is the primary for the approach (which
could be true for ADF, but not DME).

So, if you're flying an NDB approach, you could not use the GPS as a
replacement for the NDB ground station.

However, if you're flying an approach that requires DME, or an NDB to
identify the OM, you can use the GPS to provide that information.


--
Mark Hansen, PP-ASEL, Instrument Airplane
Cal Aggie Flying Farmers
Sacramento, CA

Mark Hansen wrote:

So, if you're flying an NDB approach, you could not use the GPS as a
replacement for the NDB ground station.

Here in the lower 48 states, the NDB approach is fast going the way of the
Dodo bird. Every Jepp update I have received over the last 6 months seems
to require the removal of more NBD approaches than those I replace.

--
Peter

They've gotten rid of a bunch of NDB approaches, but there were still 1,283
left as of 10/27/05.



"Peter R." wrote in message
...
Mark Hansen wrote:

So, if you're flying an NDB approach, you could not use the GPS as a
replacement for the NDB ground station.

Here in the lower 48 states, the NDB approach is fast going the way of the
Dodo bird. Every Jepp update I have received over the last 6 months seems
to require the removal of more NBD approaches than those I replace.

--
Peter

unless the navigational station is the primary for the approach (which
could be true for ADF, but not DME).

Except, of course, for the famous VOR/DME OR TACAN Z RWY 15 approach at Martin
State:

http://www.naco.faa.gov/d-tpp/0602/05222VDTZ15.PDF

On 03/09/06 12:51, Barry wrote:
unless the navigational station is the primary for the approach (which
could be true for ADF, but not DME).

Except, of course, for the famous VOR/DME OR TACAN Z RWY 15 approach at Martin
State:

http://www.naco.faa.gov/d-tpp/0602/05222VDTZ15.PDF



Are you saying that you can't use the GPS in lieu of DME for that approach?
Why not?

--
Mark Hansen, PP-ASEL, Instrument Airplane
Cal Aggie Flying Farmers
Sacramento, CA

unless the navigational station is the primary for the approach (which
could be true for ADF, but not DME).

Except, of course, for the famous VOR/DME OR TACAN Z RWY 15 approach at
Martin State:

http://www.naco.faa.gov/d-tpp/0602/05222VDTZ15.PDF
Are you saying that you can't use the GPS in lieu of DME for that approach?
Why not?

Yes, because the DME is the "principal instrument approach navigation
source" - that approach is a DME arc to the runway.

"Barry" wrote in message
. ..
unless the navigational station is the primary for the approach (which
could be true for ADF, but not DME).

Except, of course, for the famous VOR/DME OR TACAN Z RWY 15 approach at
Martin State:

http://www.naco.faa.gov/d-tpp/0602/05222VDTZ15.PDF
Are you saying that you can't use the GPS in lieu of DME for that
approach?
Why not?

Yes, because the DME is the "principal instrument approach navigation
source" - that approach is a DME arc to the runway.



A subtle but important observation! Have you won any bets with that one?

On 03/09/06 18:06, Barry wrote:
unless the navigational station is the primary for the approach (which
could be true for ADF, but not DME).

Except, of course, for the famous VOR/DME OR TACAN Z RWY 15 approach at
Martin State:

http://www.naco.faa.gov/d-tpp/0602/05222VDTZ15.PDF
Are you saying that you can't use the GPS in lieu of DME for that approach?
Why not?

Yes, because the DME is the "principal instrument approach navigation
source" - that approach is a DME arc to the runway.

Oh, right! I've never seen that before. Very cool looking approach.

I knew I was going to learn something new today :-)

Thanks for pointing it out.

Best Regards,

--
Mark Hansen, PP-ASEL, Instrument Airplane
Cal Aggie Flying Farmers
Sacramento, CA

Yes, because the DME is the "principal instrument approach
navigation source" - that approach is a DME arc to the runway.


Sounds like pure speculation to me. Can you support with any FAA
material?