..
If you consider the equipment required to maintain RNP 10 across
the Pacific a luxury, then you must not run an airline.
Aircraft dependant. Basic VFR requires no more than a magnetic compass, T&B,
airspeed, altimeter and a clock.
Very few, if any, airlines are authorized to operate VFR.
A 'decently' equipped IFR single engine aircraft would have 1 ADF, 2 VOR's, 1 GS
receiver, MB RX and hopefully a DME. that would get you about very handilly for
CAT I approaches.
Many airports in the world (including the USA) don't have ILS or
VOR approaches.
There is serious talk about decomissioning the ILS and VOR/DME
system in the not too distant future.
There's no sense maintaining all that expensive ground equipment
if GPS is sufficiently reliable.
The NDBs are already being decommissioned in the USA.
Most widebodies (and most recent narrow bodies) have everything above plus dual
or triple INS. These systems is integrated via nav management systems for
guidance. The pilot can select the nav guidance combinations
of choice.
To maintain RNP 10 tracks over the oceans, an INS needs an
update every six hours.
Currently, the only way to do that is with GPS.
Gee, I haven't meantioned GPS. Don't have too. KLM's MD-11's for example are
still GPS free and cert. for at least CAT III.
IF, and only if, there's a CAT III certified ILS at the
destination.
Lots and lots of destinations don't have that now, and there
likely won't be any at all in the future.
ILSs are very expensive to build and maintain.
RNP 5 is required in Europe already; RNP 10 is required in the
Pacific.
I don't know how that's being done on 20 hour over-ocean legs
right now; perhaps they have to detour to get within range of
Alaska or Hawaii to get their six-hour fix.
But it won't be possible at all in the not too distant future.
B-777 was the first airliner built that had GPS designed in from the intitial
design stage ... but can of course navigate on its INS, VOR, DME, ADF systems
quite well including CAT III approach (ILS+INS) if the GPS is Tango-Uniform.
It's generally possible for ATC to handle ONE airplane with
navigational problems - they simply give it more space.
That won't work if EVERYBODY's GPS is inoperative.
The days of Charles Lindbergh being the only person aloft over
the Atlantic are long gone.
