GPS and old-fashioned thinking?

G Farris wrote:
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


The FAA, and the rest of the world as well, want to eventually shut-down
the VORs. The only remaining ground-based systems will be ILSes. This
will take a long time, but it will happen.

And, it's all about Required Navigation Performance (RNP). RNP, by
definition, is sensor independent, although that has some practical
limitations today.

The new RNAV (RNP) procedures are premised on the possibility the GPS
will fail. Without this assumption, the target level of safety required
for small RNP containment areas cannot be achieved. This is
particularly true of the missed approach segment.

Note that the first FAA RNP procedure at KDCA does not require RNP for
the missed approach, just for the approach segments. OTOH, the newer
RNP procedure at KSUN requires RNP for the missed approach because of
terrain.

The DCA procedure can be flown without a second system of RNAV. The SUN
procedure cannot. Presently, the only approved second system is two
(preferably three) IRUs feeding at least two flight management systems.

Eventually, IRUs, or something quite similar, will become affordable for
light aircraft.

These concepts are where the forward thinkers are going, and not just in
this country by any means.