With all these questions about how to integrate GPS into our everyday
operations, I'm tempted to believe we have allowed the advent of this
wonderful new technology to send our thinking back to the dark ages!

We want GPS to simply replace everything else - then all that "legacy"
stuff just becomes a backup, in case the GPS signal or on-board equipment
should become unreliable. This presents problems - as has been pointed
out in the above threads - as we are not usually flying airways and
overlays (at least that's the idea) so transitioning to the "legacy"
stuff is not always that quick and easy, especially in high workload
moments like approaches or missed approach procedures. I don't know why
we don't simply weave GPS into the RNAV web that was already part of our
mentality before GPS came along. With one integrator box, receiving
signals from VOR/DME/ILS/eLORAN and GPS we could fly random routes, RNAV
waypoints and approaches even with one primary system (GPS for example)
inoperative or unreliable. An in-flight failure of one such system would
still leave us with full RNAV capability, but might be our clue to fly an
overlay, such that the (unlikely) failure of a second system would make
transitioning easier.

We consider the old KNS-80 style RNAV boxes to be obsolete today - but in
a way they were more forward-looking than the way we're going about GPS
today.

G Faris