GPS for NDB IAF on ILS?

I don't have my AIM here at work, and I'm on dial up, so I won't attempt to
download it, but I'm looking at the ILS 32 into KMQY Smyrna TN. It says ADF
REQUIRED which I understand is to identify the IAF which is the SWZ NDB not
associated with a marker beacon, inside the outer marker. This is the only
IAF charted, it is also the missed approach holding location.

My question is: In this situation is it legal to use a IFR Term Certified
GPS to substitute for an ADF.

Thanks
Jim

Jim Burns wrote:

My question is: In this situation is it legal to use a IFR Term Certified
GPS to substitute for an ADF.

In the US, my understanding is yes, the GPS is legal to use as a substitute
in this case. See the AIM 1-1-19, subsection F (Use of GPS in lieu of ADF
and DME)


--
Peter













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Yes. The only time you can't use it is to substitute for an ADF on an
NDB approach.





Jim Burns wrote:

I don't have my AIM here at work, and I'm on dial up, so I won't attempt to
download it, but I'm looking at the ILS 32 into KMQY Smyrna TN. It says ADF
REQUIRED which I understand is to identify the IAF which is the SWZ NDB not
associated with a marker beacon, inside the outer marker. This is the only
IAF charted, it is also the missed approach holding location.

My question is: In this situation is it legal to use a IFR Term Certified
GPS to substitute for an ADF.

Thanks
Jim

The only time you can't use [GPS] is to substitute for an ADF on an NDB approach.

Any idea why that is?

Jose
--
Nothing is more powerful than a commercial interest.
for Email, make the obvious change in the address.

In article ,
Jose wrote:

The only time you can't use [GPS] is to substitute for an ADF on an NDB
approach.

Any idea why that is?

Jose

Because the FAA has a bad case of recto-cranial inversion?

Jose wrote:

The only time you can't use [GPS] is to substitute for an ADF on an NDB approach.

Any idea why that is?

Every NDB approach in the country was authorized as a GPS overlay approach when the
overlay program came into being. Since then, these authorizations have been withdrawn
for any particular runway end when a stand-alone RNAV (GPS) approach was published for
that runway end.

You cannot use GPS for any final approach segment that is not retreivable from the
database, and for good reason: no approach RAIM and no approach sensitivity.

wrote:


Jose wrote:


The only time you can't use [GPS] is to substitute for an ADF on an NDB approach.

Any idea why that is?


Every NDB approach in the country was authorized as a GPS overlay approach when the
overlay program came into being. Since then, these authorizations have been withdrawn
for any particular runway end when a stand-alone RNAV (GPS) approach was published for
that runway end.

You cannot use GPS for any final approach segment that is not retreivable from the
database, and for good reason: no approach RAIM and no approach sensitivity.

Yeah and that's crucial condisering we're substituting for an ADF.

Newps wrote in
:

Yeah and that's crucial condisering we're substituting for an ADF.

And all the precision implied by an NDB approach. Bureaucracy lives!

--
Regards,

Stan

"They that can give up essential liberty to obtain a little temporary
safety deserve neither liberty nor safety." B. Franklin

Newps wrote:

Yeah and that's crucial condisering we're substituting for an ADF.

I guess that you mean that sarcastically. Without RAIM is is possible to have a sudden loss
of accuracy that would exceed the widths of an NDB final approach segment.

How likely? No more or less likely than having such a failure on a stand-alone RNAV IAP.

In any case, the criteria and conditions are set forth by Flight Standards, not me, not you,
and not ATC. ;-)

Every NDB approach in the country was authorized as a GPS overlay approach when the
overlay program came into being. Since then, these authorizations have been withdrawn
for any particular runway end when a stand-alone RNAV (GPS) approach was published for
that runway end.

You cannot use GPS for any final approach segment that is not retreivable from the
database, and for good reason: no approach RAIM and no approach sensitivity.

I can see that for GPS approaches, where you are relying on all the
gee-whiz stuff (sequencing and such), but when the GPS is substituting
for a dumb radio needle, the approach segment doesn't have to be
anywhere to give good course guidance (which is all the NDB does anyway,
and it can be argued how good it is).

I still don't see the safety issue which would prompt the FAA to balk at
this substitution.

Jose
--
Nothing is more powerful than a commercial interest.
for Email, make the obvious change in the address.