GPS Question

"kgruber" wrote in message
...
Except for flying an approach at the alternate:

Ref: AIM 1-1-19, paragraph f.1.(b)(8)
Restrictions

"For TSO-C129/129A users, any required alternate airport must still have
an approved instrument approach procedure other than GPS that is
anticipated to be operational and available at the estimated time of
arrival, and which the aircraft is equipped to fly. If the non-GPS
approaches on which the pilot must rely require DME or ADF, the aircraft
must be equipped with DME or ADF avionics as appropriate."


Not so. One can still fly a GPS approach at the alternate. You just need
the other equipment installed. If you have approved WAAS avionics, you may
plan to use any instrument approach authorized for use with WAAS avionics
at a required alternate.

Karl
"Curator" N185KG


"Not so" on which point?

The AIM clearly states that the FILED alternate must "still have an approved
instrument approach procedure other than GPS..." That's word for word out
of the book. But it doesn't SAY you can't FLY a GPS approach at said
alternate, so I agree that you can fly a GPS approach at your filed
alternate. It just can't be the ONLY approach available at that alternate.

There are several airports around that have only a GPS approach or only
approaches (such as an ILS or VOR) that require DME or NDB for position
fixing and/or executing the missed. These airports are, therefore, not
LEGAL alternates for the purpose of filing an alternate. The motivation
here is to have an executable Plan B in case of RAIM failure or GPS
interference or jamming. If GPS keeps humming, no harm, no foul but if it
lets you down for any reason, you'll need the *real* DME or ADF installed to
navigate the approach and that's the point of the AIM reference.

I also agree with your second point about WAAS equipment but your point is
outside the scope of the AIM paragraph in that it addresses TSO-C129/129A
installations, not TSO-145A which applies to WAAS augmentation of GPS.

Therefore, if your new Cirrus doesn't have bona fide NDB, DME, or WAAS, your
FILED alternate would need to have an available approach without the
requirement for any of those.

That being said, what you file and what you fly will likely be based on why
you miss the primary approach in the first place.