If the ILS approach is not authorized, which component is considered out of service?

The localizer is a crucial component of an Instrument Landing System (ILS) that provides lateral guidance to the runway centerline. If the ILS approach is not authorized, it indicates that the localizer is not functioning properly or is unavailable, rendering the entire ILS approach unusable. The localizer emits a radio signal that allows aircraft to align themselves accurately with the runway. If this signal is out of service, pilots cannot determine their correct approach path to the runway, which is essential for a safe landing.

The other components, like the glideslope, outer marker, and inner marker, might also contribute to the overall ILS system; however, the localizer is primarily responsible for lateral guidance. Without this guidance, the ILS approach cannot be safely completed, thus making it the component considered out of service in such scenarios.