Garmin GFC 600 Pilot's Manual page 57

Some navigators that combine both GPS and VHF Nav functions are capable of
automatically switching the CDI source from GPS to VOR/LOC when programmed to
transition from a GPS flight plan to an ILS approach. The AFCS does not support
automatic transition from a Navigation mode to an Approach mode and will revert to
ROL mode if it senses that the navigation source has changed.
CAUTION:
capability should be configured with automatic switching disabled.
When GPS Approach mode is armed, Glidepath mode is also armed.
Selecting GPS Approach Mode:
1) EXTERNAL NAVIGATOR: Ensure a GPS approach is loaded into the active
flight plan. The active waypoint must be part of the flight plan (cannot be a
direct-to a waypoint not in the flight plan).
2) EXTERNAL NAVIGATOR: Ensure that GPS is the selected navigation source.
3) GMC 605: Press the APR key.
VOR Approach mode (VAPP) provides greater sensitivity for signal tracking than VOR
Navigation mode.
Selecting VOR Approach Mode:
1) EXTERNAL NAVIGATOR: Ensure a valid VOR frequency is tuned
2) EXTERNAL NAVIGATOR: Ensure that VOR is the selected navigation source.
3) GMC 605: Press the APR key.
LOC Approach mode allows the autopilot to fly an ILS approach with a glideslope.
When LOC Approach mode is armed, Glideslope mode is also armed automatically.
LOC captures are inhibited if the difference between aircraft heading and localizer
course exceeds 105°.
Selecting LOC Approach Mode:
1) EXTERNAL NAVIGATOR: Ensure a valid localizer frequency is tuned.
2) EXTERNAL NAVIGATOR: Ensure that LOC is the selected navigation source.
3) GMC 605: Press the APR key.
190-01488-00 Rev. B
Navigators or PFDs with automatic CDI source switching
Garmin GFC 600 Pilot's Guide
AFCS
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