RNAV vs IFR GPS

He did not say that right. There is VOR/DME-RNAV as well as INS RNAV, IRS RNAV,
GPS RNAV, and LORAN RNAV.

VOR/DME RNAV still has some crummy approaches in the system.

David Brooks wrote:

VOR-DME is RNAV too? Now I'm confused.

When can we get those updates, Bob? (I note that asa2fly.com is a little
sparse in the "textbook updates" department).

-- David Brooks

"Bob Gardner" wrote in message
news:nwQ%b.424998$na.813278@attbi_s04...
I feel your pain. Since the FAA lumped GPS, Loran, and VOR-DME into one
basket labelled RNAV, I have been going nuts trying to keep my books up to
date. The KNS-80 and its ilk are still around, so I have to discuss that
kind of RNAV, but because there are so many approaches labelled RNAV
(GPS),
the potential for confusion is there. It all boils down to the fact that
if
you can fly a random route using any one of the three, you have RNAV.

Bob Gardner

"PaulaJay1" wrote in message
...
Coming into CLE the other day the controller ask if I had RNAV and I
said
no,
that I was /G ,that is, IFR GPS. He said that it was the same and gave
me
direct.....
Is it the same, should I have answered yes to his question? Of course I
can
navigate direct but do I have "RNAV"?

Chuck

wrote in message ...

He did not say that right. There is VOR/DME-RNAV as well as
INS RNAV, IRS RNAV, GPS RNAV, and LORAN RNAV.


IRS RNAV?

"Steven P. McNicoll" wrote in message =
hlink.net...
=20
wrote in message =
...

He did not say that right. There is VOR/DME-RNAV as well as
INS RNAV, IRS RNAV, GPS RNAV, and LORAN RNAV.

=20
IRS RNAV?
=20
=20

Not commonly used, because of the high tax rate, maybe?

Steven P. McNicoll wrote:
wrote in message ...

He did not say that right. There is VOR/DME-RNAV as well as
INS RNAV, IRS RNAV, GPS RNAV, and LORAN RNAV.



IRS RNAV?



Yes, a straight line is the fastest way to get away from the IRS.

Matt

"Steven P. McNicoll" wrote:

wrote in message ...

He did not say that right. There is VOR/DME-RNAV as well as
INS RNAV, IRS RNAV, GPS RNAV, and LORAN RNAV.


IRS RNAV?

Not in the airplanes you fly, Steve. In the big ships, three IRUs that
provide the attitude platform and the basic inertial reference. If the GPS
failes, the DME/DME fails, the VOR/DME fails, and the VOR/VOR fails then a
slightly degraded, but noneless very good position is provided by the IRUs
via the FMS, which in combination is known as the IRS (inertial reference
system), which in turn is IRS RNAV when all external sensors are not
available.

From Chapter 7 of the current FAA Instrument Flying Handbook:

INS Components
INS is considered a stand-alone navigation system, especially when more than
one independent unit is onboard. The airborne equipment consists of an
accelerometer to measure acceleration—which, when integrated with time,
gives velocity—and gyros to measure direction.
Later versions of the INS, called IRS (inertial reference systems) utilize
laser gyros and more powerful computers; therefore, the accelerometer
mountings no longer need to be kept level and aligned with true north. The
computer system can handle the added workload of dealing with the
computations necessary to correct for gravitational and directional errors.
Consequently, these newer systems are sometimes called strapdown systems, as
the accelerometers and gyros are strapped down to the airframe, rather than
being mounted on a structure that stays fixed with respect to the horizon
and true north.
INS Errors
The principal error associated with INS is degradation of position with
time. INS computes position by starting with an accurate position input
which is changed continuously as accelerometers and gyros provide speed and
direction inputs. Both the accelerometers and the gyros are subject to very
small errors; as time passes, those errors likely will accumulate.
While the best INS/IRS display errors of 0.1 to 0.4 NM after flights across
the North Atlantic of 4 to 6 hours, smaller and less expensive systems are
being built that show errors of 1 to 2 NM per hour. This accuracy is more
than sufficient for a navigation system that can be combined with and
updated by GPS. The synergy of a navigation system consisting of an INS/IRS
unit in combination with a GPS resolves the errors and weaknesses of both
systems. The GPS is accurate all the time it is working but may be subject
to short and periodic outages. The INS is made more accurate because it is
continually updated and will continue to function with good accuracy if the
GPS has moments of lost signal.