Ils Approaches - Garmin GNS 480 Pilot's Manual

Basic Operation
Procedures
90

ILS Approaches

Precision approaches can be performed with the GNS 480' s built-in VLOC (VOR/localizer/glideslope) receivers.
The GPS receiver can be used for guidance prior to reaching the final approach fix, but once there, the proper
frequency must be selected on the VLOC window (left side of screen) and the CDI output set to "VLOC".
The GNS 480 can be set to automatically switch the external CDI output from GPS to VLOC as you inter-
cept the final approach course. When the ILS approach is activated (and the correct ILS frequency is active
in the VLOC window), the GNS 480 automatically switches within 1.2 nautical miles left or right of the final
approach course. The following criteria must be met for the CDI autoswitch to occur based on your present
position: 1) the aircraft must be before the FAF, 2) within 15 nm of the FAF, 3) aircraft and ground track is
within 90° of the final approach course, 4) within 1.2 nm of cross track error, 5) there are no
course reversals in the flight plan to be performed, and 6) the ILS frequency is valid with a
decoded ident.
The illustration shows both multiple locations along the approach path and the CDI selection that you can ex-
pect: GPS or VLOC. Within the area of the shaded box, the automatic switch from GPS to VLOC should occur.
The pilot will receive a message "SWITCHING FROM GPS TO NAV."
NOTE: If an unusual approach intercept is made, the GNS 480 may not be able to autoswitch,
based on the required criteria. In this case, press the CDI key to manually switch from GPS to
VLOC.
The automatic switch from GPS to VLOC is not immediate, but instead occurs gradually to prevent abrupt
CDI changes when coupled to an autopilot. The CDI selection can also be changed manually by pressing the
CDI key. If a missed approach is required, the GNS 480 will automatically switch back to GPS for the missed
approach. If you fly the approach again using VTF mode or with a procedure turn, autoswitch will reset and
switch again. To prevent automatic ILS CDI selection, choose the "Manual" ILS CDI setting, (the factory default
setting is "Auto", which enables the automatic switch to VLOC).