Re: Boeing landing procedures

From: (FMCDave)
Organization: America Online, Inc. (1-800-827-6364)
Date:         27 Apr 95 03:00:25 
References:   1 2
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In article <airliners.1995.437@ohare.Chicago.COM> "Steven J. Leighton"
<> writes:

>I have been led to believe that for the final 200 feet before
>touchdown Boeing aircraft use the INS system for landing as opposed
>to ILS alone. Could someone please clarify if this is truly the case.

:On the latest systems, the autopilot/autothrottle and INS are integrated to
:such an extent that when you are using one you can be considered to be using
:both. However, the autopilots (all 3 of them) would be engaged and locked on
:to the ILS if an autoland was being considered.

In the "autoland" sense, the 767 does not operate using the Navigator.
The 767 uses a mulitsensor RNAV system called the Flight Management System
which uses a triple-mix Inertial Reference System as one of the inputs.
Basically, the FMC (with LNAV/VNAV engaged) will provide steering to the
autopilot during the approach.  If the crew has armed the autoland system,
the autopilot will take over when the ILS Glideslope has been captured.
Then the FMC/IRS is really out of the loop.  The autopilot caculates the
deviation from the ILS glideslope and provides its own steering.