Ron Rosenfeld wrote in
:

The lack of regulatory power of the AIM is one of those arguments that
goes on from time to time. But I believe that, regardless of how we may
want to interpret things, the FAA would have a pretty good case, if they
wanted to, if you, for example, landed out of an approach requiring an
ADF, and you did not even have a functioning ADF on board, nor an FAA
approved equivalent.

My guess is that it won't actually come up until someone has an accident
surrounding an NDB approach...

If I were the FAA lawyer arguing, I would point out the following:

-------------------------
91.205

a) General. ... no person may operate a powered civil aircraft with a
standard category U.S. airworthiness certificate in any operation
described in paragraphs (b) through (f) of this section unless that
aircraft contains the instruments and equipment specified in those
paragraphs (or FAA-approved equivalents) for that type of operation, and
those instruments and items of equipment are in operable condition.

(d) Instrument flight rules. For IFR flight, the following instruments
and
equipment are required:

(2) ... navigational equipment appropriate to the ground facilities to
be
used.
------------------------------

It is the AIM that effectively gives the FAA-approved equivalent
(specified in para (a)) for the navigational equipment specified in para
(d)(2). And the AIM specifically requires, for GPS equivalents, that
they be compliant with the AC.

And since I'm not a lawyer, I would probably respond that paragraph 1-2-3
(b)(2) specifically permits GPS units that are not fully compliant with AC
90-100, although it defines certain restrictions. However, AC 90-100
compliance is not required for equipment to be represented as "appropriate
to the ground facilities being used."

I'm sure someone will write that a GPS that has been specifically listed
as UNapproved for an approach related operation in the AIM can be used
for it because it is somehow "appropriate to the ground facility being
used" and the AIM is not regulatory. I would prefer to be on the other
side of that argument.

Compliance with AC 90-100 is only required for use "on segments of an
instrument approach, departure, or arrival procedure defined by a VOR
course" except those "which may be selected by route name or constructed by
'stringing' together two or more waypoints from an onboard navigation
database". Therefore these GPSes are not specifically UNapproved except for
a certain very specific type of operation. To say that this restriction
disqualifies the GPS from use for NDB approaches, for example, is non-
sequiter.

Hopefully, the AIM, and possibly the AC, will be changed to again
indicated that previously approved FAA-equivalents are continuing to be
approved. --ron

Yes, hopefully this whole mess will be cleared up quickly so that if
nothing else we can all go back to using our GPS without fear of being
ramp-checked.