Is your IFR GPS still legal for use?

Ron Rosenfeld wrote in
:

So far as the restriction people have been stating having to do with not
being able to use the uncertified GPS units as a substitute for ADF/DME,
that stems from the AIM (1-2-3) (and possibly a change that has not been
published) restricting this type of usage to units that are compliant
with AC90-100.

Ahh... Now I get why I didn't see it.

But the AIM is not regulatory, is it?

If it is, it's a stupid rule. One of the ILSs at my home airport actually
requires an ADF. What a pain.

On Sat, 26 May 2007 19:48:19 GMT, Judah wrote:

Ron Rosenfeld wrote in
:

So far as the restriction people have been stating having to do with not
being able to use the uncertified GPS units as a substitute for ADF/DME,
that stems from the AIM (1-2-3) (and possibly a change that has not been
published) restricting this type of usage to units that are compliant
with AC90-100.

Ahh... Now I get why I didn't see it.

But the AIM is not regulatory, is it?

If it is, it's a stupid rule. One of the ILSs at my home airport actually
requires an ADF. What a pain.

Yeah, but there isn't any regulation allowing substitution of GPS for other
NAVAID's.

I think the AIM revision was just published today on the FAA web site. I
find it pretty confusing in terms of which units are allowed to do what.
--ron

Ron Rosenfeld wrote in
:

Yeah, but there isn't any regulation allowing substitution of GPS for other
NAVAID's.

I think the AIM revision was just published today on the FAA web site. I
find it pretty confusing in terms of which units are allowed to do what.

But if the AIM is not regulatory, why does it matter?

IIRC, the Regs only say that you must have the equipment necessary for the
specific navigation being used.

On Mon, 28 May 2007 02:54:04 GMT, Judah wrote:

Ron Rosenfeld wrote in
:

Yeah, but there isn't any regulation allowing substitution of GPS for other
NAVAID's.

I think the AIM revision was just published today on the FAA web site. I
find it pretty confusing in terms of which units are allowed to do what.

But if the AIM is not regulatory, why does it matter?

IIRC, the Regs only say that you must have the equipment necessary for the
specific navigation being used.

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.

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.

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.

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

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.