Backcourse Approach
When making a backcourse approach, set the Selected Course to the localizer front course.
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.
Backcourse Mode captures and tracks a localizer signal in the backcourse direction. Backcourse is indicated by ‘BC’ in the AFCS status box.
If GS and LOC Mode are armed, the flight director can only capture the localizer front course, indicated by ‘LOC’ in the AFCS status box. If only LOC Mode is armed (not GS Mode), the flight director will capture either the front course or the backcourse based on the angle at which the aircraft intercepts the localizer.