The localizer's effective range extends to how many nautical miles?

The localizer's effective range extends to how many nautical miles?

• A. 12 nm
• B. 18 nm
• C. 25 nm
• D. 40 nm

Answer: (B)

The localizer is used to provide horizontal guidance to keep you aligned with the runway centerline during approach. Its usable signal, or service range, is about 18 nautical miles from the runway threshold. Within this distance, the course information is reliable enough for tracking accurate lateral guidance. Beyond roughly 18 NM, the signal weakens and accuracy can't be guaranteed, so the localizer isn’t considered effective for precise alignment. While the glideslope provides vertical guidance over a shorter distance (about 10 NM), the localizer’s standard service range is the 18 NM figure, which is why 18 NM is the best choice.

The localizer is used to provide horizontal guidance to keep you aligned with the runway centerline during approach. Its usable signal, or service range, is about 18 nautical miles from the runway threshold. Within this distance, the course information is reliable enough for tracking accurate lateral guidance. Beyond roughly 18 NM, the signal weakens and accuracy can't be guaranteed, so the localizer isn’t considered effective for precise alignment. While the glideslope provides vertical guidance over a shorter distance (about 10 NM), the localizer’s standard service range is the 18 NM figure, which is why 18 NM is the best choice.