Re: GPS on airliners?

From:         ehahn@roland.mitre.org (Ed Hahn)
Organization: The MITRE Corporation, McLean, Va.
Date:         13 Apr 94 19:17:05 PDT
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In article <airliners.1994.1125@orchard.Chicago.COM> dunn_jj@gold.colorado.edu writes:

   Do any of the newer airliners (A320, 777, 747-400) have a global positioning
   system? 

   Is the GPS in any way connected to the autopilot? Does that mean the aircraft
   could take off and land automatically, without requiring pilot control?


   >Jon Dunn<
-----
There are no airliners using GPS for primary navigation out there
right now, and the only GPS receivers being used on airliners, in the
US at least, are being used for test purposes only.

For example, American Airlines B757 ship number 5DD has a Litton GPS
sensor and antenna mounted in the upper fuselage (near the L2 door
(2nd door on the left looking from above the aircraft, counting from
the nose)).  This ties into the IRUs when SPECIAL IRUs are installed.
The GPS functions of the IRUs are not active during revenue flight.
The IRU actually creates a hybrid position signal based on a
combination of the inertial position and the GPS position.

Also part of the test system is the Honeywell PIP FMC, with revised
flight management software, and a connection to the ACARS VHF datalink
system, which is being used as a channel for Differential information
during this experiment.

American, ARINC (the providers of ACARS), Litton, Honeywell, and
others (including the MITRE Corporation) are attempting to demostrate
autoland capability with this B757 using DGPS.

Now then.  Airliners since the B767 have been "able" to fly from about
50 foot altitude on takeoff to the destination, and complete an
autoland without direct human intervention on the flight controls.
Note that the pilot does have to enable certain autoflight modes,
however.  As for autoland capability, the L1011 was able to
demonstrate it as far back as the early 70s.

Since the GPS provides an accurate position source, when implemented,
it will be used by the Flight Management Systems as part of the
overall navigation autopilot functions.  As for any additional
capabilities with GPS, the only "new" operational functions would
allow CAT I instrument approaches without ground transmitters.
Autoland will require a differential ground station and datalink
transmitter.  Other uses of GPS being explored are cancellation of
"inertial drift" on long flights.

Hope this helps,
ed

////////   Ed Hahn | ehahn@mitre.org | (703) 883-5988   \\\\\\\\
The above comment reflects the opinions of the author, and does not
constitute endorsement or implied warranty by the MITRE Corporation.
Really, I wouldn't kid you about a thing like this.