So how come I can't just use the gps alone? It seems like it is much more
flexible, and then I wouldn't be as dependent on what ground based stuff was
available.
tom

Basically, what this all boils down to, is this: If you have a
IFR-certified GPS system (TSO-129 certified), like the Garmin
GNS 430, you can use it for IFR operations, but the plane needs
to be equipped with the typical IFR navigation radios anyway.