Interial Nav Systems

Robert Moore wrote in message .6...
(Duck Dog) wrote

I was reading some of the ICAO findings of the Korean Air 007
shootdown, and I was struck by the fact that an intertial
^^^^^^^^^
Well, no one caught my spelling error, so I guess I'll just flame
myself ;-)


navigation system on the 747 was used for much of the overseas
flight. Of course, this was 1983 and GPS was probably not used
in civilian aircraft yet, so I really shouldn't be surprised.
Does anyone know if INS is still used on civilian airliners,
particularly on overseas flights?

What would you have used??? :-)

Rand McNally? ;-)

When I first started flying,
we were still using the Nantucket CONSOLAN for oceanic flying.

During the B-707 and DC-8 days, INS was a very expensive method
of navigation. In addition to the initial cost, the routine
maintenance on the gyros was very costly. American Airlines
actually prohibited the use of the INS on domestic flight legs.
With the introduction of the B-747, the gyros were put to a dual
use, INS and AHRS (attitude heading reference system) and with
the introduction of the ring-laser gyro, maintenance cost have
gone way down.
Boeing's latest jetliners are still equipped with a ring-laser
gyro based IRS (inerial reference system). Since INS is a DR
(dead reckoning) system, some method must be provided to update
and correct the IRS position. Previously, this was accomplished
with VOR/DME and now, GPS has been added to the mix.

As an aside, my understanding of military aircraft, particularly
combat aircraft, is that they rely much more on INS than GPS. I'm
just guessing, but I'd bet that stems from the assumption that in
full-scale conflict the GPS constellation will be unavailable for
whatever reason, and that INS (which doesn't rely on external
navigation facilities) can continue to provide very accurate
positioning data.

BTW, the full constellation of 24 GPS satellites was not achieved
until 1994.

OK, but I remember that GPS was highly touted in the first Gulf War,
so it's been operational for at least a while longer than that.

Flight crew failure was the cause of the KA 007 incident, not a
problem with the INS.

I understand that. I was just struck by the references to INS. BTW,
do you know whether any INS systems are used in GA aircraft?

Bob Moore
PanAm (retired)