What distance from the airport must the approach mode be activated for it to work?

• A. 5 NM
• B. 10 NM
• C. 0.5 NM
• D. 2 NM

Answer: (D)

Approach mode ties the autopilot to the final approach path, letting it automatically capture and follow the localizer and glideslope for an ILS or approved approach. You want to arm it when you’re close enough to reliably receive and track those signals, but not so close that there’s little margin for correction. About 2 nautical miles from the runway is the typical point to activate because at that distance the localizer and glideslope signals are strong enough for a clean capture and stable descent. If you wait much farther out, capture can be unstable or missed; if you activate too close, there may not be time for proper capture and adjustment. So the correct activation distance is around 2 NM.