wrote in message ...

Not so. VOR is still the primary means of navigation in the NAS. Even
the
latest and greatest airline aircraft with dual GPS sensors, dual FMSes,
triple
IRUs, etc, cannot be dispatched without operate VOR receivers (in their
case
two).

The presumption is that the GPS system can fail at any time; at least in a
given
area. WAAS doesn't mitigate that whatsoever.


So why is it presumed that the VOR system cannot fail?