Garmin G3X Pilot's Manual page 368

AFCS
BACKCOURSE APPROACH
NOTE: When making a backcourse approach, set the Selected Course to the
localizer front course.
NOTE: 'BC' will not be displayed on the G3X HSI.
Backcourse Mode captures and tracks a localizer signal in the backcourse direction.
Backcourse is indicated by 'BC' in the autopilot status box.
If GS and LOC Mode are armed, the autopilot can only capture the localizer front
course, indicated by 'LOC' in the autopilot status box. If only LOC Mode is armed (not
GS Mode), the autopilot will capture either the front course or the backcourse based
on the angle at which the aircraft intercepts the localizer.
Selecting BC Mode:
1) EXTERNAL NAVIGATOR: Tune and activate the desired LOC frequency.
2) G3X: Ensure that LOC1 is the selected navigation source on the (use
the CDI SRC Softkey on the PFD or PFD Page to cycle through external
navigation sources if necessary). The HSI should automatically slew the
needle to the correct course.
3) G3X: From the PFD or PFD Page, press the HDG/ROLL Softkey to access
the autopilot lateral modes and then press the AP NAV Softkey.
Or: Press or the NAV Key on the GMC 305
If the aircraft heading is within 75˚ of the localizer backcourse then BC
Mode will be armed. If the aircraft heading is within 105˚ of the localizer
front course, LOC Mode will be armed.
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Garmin G3X Pilot's Guide 190-01115-00 Rev. K