Garmin GFC 600H Pilot's Manual page 42

HFCS
Once the localizer has been captured (LOC is annunciated as the active lateral
mode), the glideslope can also be captured.
Once the following conditions have been met, the glideslope can be captured:
• GPS must be the active lateral mode.
• Vertical deviation is valid.
• The CDI is at less than full-scale deviation.
• Automatic sequencing of waypoints has not been suspended (no 'SUSP'
annunciation on the HSI).
• Must be captured from below the glideslope.
GMC 605H ANNUNCIATIONS
The GMC 605H annunciates 'GS' for Glideslope mode. Since Glideslope mode relies
on LOC lateral guidance, the 'LOC' lateral mode is also annunciated.
32
GMC 605H Annunciating Glideslope Mode
Garmin GFC 600H Pilot's Guide 190-02081-04 Rev. A