Garmin G3X Touch Pilot's Manual page 261

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 is pressed or NAV is touched
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
• During a LOC/ILS approach, the FAF is crossed while in GPS Navigation Mode
after the automatic navigation source switch from GPS to LOC
LOC Mode is activated when the automatic navigation source switch takes
place. If the APR Key is pressed or APPR is touched 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 Touch: While GPS is still the selected navigation source on the
external navigator, press the APR Key (GMC 305) or touch APPR 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
Touch will capture the localizer and then the glideslope.
190-01754-00 Rev. A Garmin G3X Touch Pilot's Guide
AFCS
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