GPS for NDB IAF on ILS?

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 Since then, these authorizations have been withdrawn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 Since then, these authorizations have been withdrawn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. ;-)

On Fri, 11 Feb 2005 10:26:27 -0800, wrote:

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.


I think everybody is saying that the same loss of accuracy exists with
ADF receivers, especially the older ones, all the time.

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 Since then, these authorizations have been withdrawn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.

Jose wrote:

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.

I am not their advocate; just stating the facts as established by Flight Standards.

You might want to ask the man in charge, John McGraw, Director, Technical Programs Division,
Flight Standards Service, FAA, at their DC head-shed address.