VOR Check question

Stan Gosnell writes:

My understanding is that WAAS has an integrety function and is able to
detect an inaccurate signal.

RAIM (Receiver Autonomous Integrity Monitoring) is available without WAAS,
and was available before WAAS was implemented.

Look up FDE "fault detection / exclusion" instead. This computation
is possible to perform without WAAS (the GNS430 does some now), but
WAAS carries satellite health flags that simplify it.


- FChE

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?

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

I would assume (and I know the etymology) that VORs fail 1000 square
miles at a time, and GPS fails 3,000,000 square miles at a time. Or,
more to the point, there is more systemic redundancy in the VOR system.

Jose
--
Nothing takes longer than a shortcut.
for Email, make the obvious change in the address.

"Jose" wrote in message
. ..

I would assume (and I know the etymology) that VORs fail 1000 square miles
at a time, and GPS fails 3,000,000 square miles at a time. Or, more to
the point, there is more systemic redundancy in the VOR system.


The question was, "So why is it presumed that the VOR system cannot fail?",
not, "So why is it presumed that a VOR cannot fail?" The loss of a GPS
satellite would not render the GPS system unusable.

The question was, "So why is it presumed that the VOR system cannot fail?",
not, "So why is it presumed that a VOR cannot fail?" The loss of a GPS
satellite would not render the GPS system unusable.

.... and my response addresses exactly that. The failure of a single VOR
(or even twenty) won't cripple the VOR system. But the (albeit
unlikely) failure of twenty satellites will cripple the GPS system.
There is more systemic redundancy in the VOR system, just by virtue of
there being more VORs, and by virtue of the fact that a single VOR
affects a relatively small area.

Jose
--
Nothing takes longer than a shortcut.
for Email, make the obvious change in the address.

"Jose" wrote in message
.. .

... and my response addresses exactly that.


No, it addresses the failure of a VOR and the failure of a GPS satellite.



The failure of a single VOR
(or even twenty) won't cripple the VOR system. But the (albeit unlikely)
failure of twenty satellites will cripple the GPS system.


You're right, but you're now comparing the failure of about 0.1 to 2% of the
VOR system to the failure of about 69% of the GPS constellation.

On Sat, 23 Jul 2005 04:41:18 -0700, wrote:

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.

Could you reconcile your statement with AIM 1-1-20 c.

"7. Unlike TSO-C129 avionics, which were certified as a supplement to other
means of navigation, WAAS avionics are evaluated without reliance on other
navigation systems. As such, installation of WAAS avionics does not require
the aircraft to have other equipment appropriate to the route to be flown."


Ron (EPM) (N5843Q, Mooney M20E) (CP, ASEL, ASES, IA)