Garmin GFC 600H Pilot's Manual page 48

HFCS
Approach mode is selected by pressing the APR key. Approach mode acquires and
tracks the navigation source (GPS, VOR, or LOC), selected and currently selected for use
on the HSI interfaced to the GFC 600H. This mode uses roll steering for GPS approach
guidance or the selected navigation receiver deviation and selected course inputs to
fly the approach. Pressing the APR key when the CDI deflection is greater than half
scale HDG will immediately become the active lateral mode and the selected approach
mode will be armed.
If the CDI deflection is less than half scale, the approach mode immediately becomes
the active mode when the APR key is pressed.
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.
CAUTION:
capability should be configured with automatic switching disabled.
GPS APPROACH MODE
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) NAVIGATION INDICATOR: Ensure that the GPS navigation source is
selected and a valid CDI is displayed on the HSI. If the CDI is more than 1/2
scale ensure the heading bug is set as desired.
38
GMC 605H Annunciating GPS Approach Mode Armed
Navigators or PFDs with automatic CDI source switching
Garmin GFC 600H Pilot's Guide 190-02081-04 Rev. A