Garmin G3X Pilot's Manual page 360

AFCS
When the CDI has automatically switched from GPS to LOC during a LOC/ILS
approach, GPS Navigation Mode remains active, providing GPS steering guidance until
the localizer signal is captured. LOC Navigation Mode is armed when the automatic
navigation source switch takes place. If the APR Key or AP NAV Softkey is pressed
prior to the automatic navigation source switch, LOC Navigation Mode is armed.
If Navigation Mode is active and either of the following occur, the flight director
reverts to Roll Hold Mode (wings rolled level):
• Different VOR tuned while in VOR Navigation Mode (VOR Navigation Mode reverts
to armed)
• Navigation source manually switched (with the CDI SRC Softkey)
• During a LOC/ILS approach, the FAF is crossed while in GPS Navigation Mode
after the automatic navigation source switch from GPS to LOC
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hanging the
The Selected Course is controlled by pressing the OBS CRS Softkey, VOR
CRS Softkey, or LOC CRS Softkey, (while in OBS, VOR, LOC, or BC Mode)
and turning the FMS Joystick on the G3X PFD (or PFD Page) to select the
desired course (or press XPDR/CRS > OBS CRS / VOR CRS / LOC CRS
from the PFD (or PFD Page) if a transponder is configured).
LOC Mode is activated when the automatic navigation source switch takes
place. If the APR Key or AP APPR Softkey is pressed prior to the automatic
navigation source switch, LOC Mode is armed.
In the right circumstances, LOC and GS Modes can be armed while GPS
Mode is still active and the external navigator is set to GPS (not VLOC).
Arming LOC & GS Modes while GPS Mode is still active:
1) EXTERNAL NAVIGATOR: Tune and activate the desired localizer frequency.
2) EXTERNAL NAVIGATOR: Load the approach (LOC, ILS, LDA, SDF, etc) into
the flight plan.
3) G3X: While GPS is still the selected navigation source on the external
navigator, press the APR Key (GMC 305) or AP APPR Softkey to arm LOC
and GS (Glideslope) Modes even with GPS Mode still active. The external
navigator will switch from GPS to VLOC automatically and the G3X will
capture the localizer and then the glideslope.
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Garmin G3X Pilot's Guide 190-01115-00 Rev. K