Dave Butler wrote:


You are not allowed to use an IFR-certified GPS for en route (domestic
airspace) in a non-radar environment except with the special Alaska
provisions.


Perhaps you meant to say you're not allowed to fly off-airway?

If you really meant what you said, please explain / cite the rule.

Part 95, IFR Altitudes establishes MEAs and is the authority for airways
and Jet Routes. Those airways are rules, just like an instrument
approach procedure is a rule.

With instrument approach procedures (in addition to RNAV/GPS IAPs) you
have VOR and NBD IAPs that are approved for overlay flight with GPS.
That is the authorization to substitute GPS for VOR, where authorized on
the chart.

You don't have any overlay (i.e., standalone, non-radar) authorization
fo Victor Airways or Jet Routes. Thus, if you are not in a radar
environment you cannot use RNAV as primary for Victor airways or Jet Routes.

Does anyone care? Only if something goes wrong.

There are a few Q Routes, which are predicated solely on RNAV, but thus
far they have been established where traffic volumne is high and radar
is available. They are pretty much for the airlines in the lower 48,
thus far. And, I believe they are all in the high altitude stratum.

As I said before, Alaska has a special authorization that specifically
permits GPS/RNAV overlay of Victor airways.