Which term describes the protected airspace around the ILS localizer that must not be entered during approach to avoid interference?

• A. ILS localizer buffer zone
• B. ILS critical area
• C. Final approach sector
• D. Instrument approach corridor

Answer: (B)

Protecting the navigation signal during an ILS approach relies on a defined airspace around the localizer and its associated transmitter called the ILS critical area. This protected region is established to prevent interference from other aircraft, vehicles, or equipment that could disturb the localizer signal and distort the course guidance pilots rely on for a precise approach. Entering the critical area while the ILS is transmitting can degrade the localizer reception, leading to erroneous course indications and unsafe deviations on final approach. Keeping this area clear helps ensure the approach guidance remains accurate and dependable.

Other terms don’t describe this protected surface. The idea of a buffer zone isn’t a standard term for protecting the ILS signal, and the final approach sector or the instrument approach corridor refer to broader path concepts rather than the specific airspace that must remain free to preserve localizer integrity.