Well, partially correct. It doesn't matter what kind of GPS you have. On an IFR flight plan(in controlled airspace) you cannot be on a direct route in any non radar environment unless you are going directly to or From a VOR and are within navaid limitations. The ONLY exception is if you are on a VFR on top flight plan (OTP). You may meet the FAR's for direct routing, but ATC has a little different rules. You don't have to worry too much about filing the correct routes because if you are going into a known non radar area at your altitude, ATC will clear you via Victor airways no matter what equipment qualifier you have. Knowing this information might help you at some point where you can just tell them you will go VFR on top and stay on your route, or ask for a higher altitude to stay in radar coverage. Unfortunately, there are areas here in CO where the minimum altitude for direct routes would be FL200, but the minimum IFR altitudes are common to be 170 too. Basically the ATC rules state that you can only be on a direct route if you are being radar monitored. There are some more ATC rules that deal with GPS approaches too that might seem to be different than the FAR's are telling you. If you want to look up the ATC bible, just search for the 7110.65 faa manual. It covers everything in terminal, enroute, military, you name it, it's what the ATC guys have to use. Oh, and dont forget you can't go VFR on top above FL180.
Ron Galbraith
HPAT instructor - retired ATC
Yes. Even though one could file /G with a GPS with RAIM, one still
had to obey Far 91.205(d)(2) - to paraphrase: 2-way radio and navigation
equipment appropriate to the ground facilities to be used. What
that means is TSO'd GPS is usable as for navigation in a radar environment
(appropriate ground equipment), but not as a primary in non radar environments -
in the mountains - thus, one must have had VOR nav capabilities.
TSO'd GPS with WAAS is sufficient as a stand-alone navigation system so
that it may be used as a primary navigation system in any environment.