What enables automatic switching between FMS and NAV modes when turning to the final approach course on an ILS?

• A. Enable Nav Preview with the inbound course set and APR mode armed.
• B. Enable APR mode only.
• C. Disable Nav Preview.
• D. Set NAV to GPS mode.

Answer: (A)

Preparing the system with the inbound final approach course and arming the approach mode allows the autopilot/flight director to hand off guidance smoothly from FMS nav tracking to the ILS final approach. Nav Preview watches for your turn onto the final approach course and, with the inbound course set, signals the system to switch to approach guidance automatically once the course is established. Having APR armed ensures the autopilot is ready to follow the localizer (and glideslope if active) as you intercept and fly the ILS approach. Without Nav Preview, or without arming APR, the handoff isn’t automatically triggered, and using GPS mode would not provide the ILS localizer guidance.