When should GPS approach mode be armed during a GPS approach?

• A. Within 30 NM
• B. At the FAF
• C. Upon crossing final approach fix
• D. After landing

Answer: (A)

Arming GPS approach mode early gives the navigation and autopilot time to switch to the published approach path and start providing the proper guidance as you transition from en route to the final approach. The 30 NM window is the recommended lead time because it allows the system to acquire satellites, load the approach, and capture the final approach course before you reach the point where the approach guidance becomes critical. If you wait until the FAF or later, the GPS may not capture the approach path in time, and you could lose the automatic lateral/vertical guidance that keeps you on the proper descent profile. Arming after landing isn’t applicable, and arming too early isn’t risky, but the standard practice is to arm within 30 NM to ensure a smooth, automatic transition to the approach.