Garmin GFC 600 Pilot's Manual page 58

AFCS
If Approach mode is active and any of the following occur, the AFCS reverts to Roll
Hold mode (wings rolled level):
• Different VHF Nav frequency tuned while in VOR or LOC Approach mode (note
that in some installations Approach mode may remain engaged if there is still
valid deviation after the frequency changes from VOR to VOR, or from LOC to LOC)
• Navigation source switched (e.g. GPS to VOR/LOC, or VOR to LOC)
Pressing the CWS button and hand-flying the aircraft does not change the selected
course while in Approach mode. Upon release of the CWS button the autopilot will
guide the aircraft back to the selected course (or GPS flight plan).
GMC 605 AND GI 285 ANNUNCIATIONS
The GMC 605 will annunciate VOR Approach mode as VAPP, LOC Approach mode as
LOC and GS, and GPS Approach mode as GPS and GP. The annunciation displayed is
based on the selected navigation source when the APR key is pressed.
The GI 285 provides the same annunciations as the GMC 605 with the exception of
VOR Approach mode which is annunciated VOR instead of VAPP.
50
GMC 605 Annunciating Various Approach Modes
Garmin GFC 600 Pilot's Guide 190-01488-00 Rev. B