What must be identifiable for radar use if the inner marker is not available during approach?

For radar use during an approach, the Ident Outer Marker (OM) must be identifiable if the inner marker is not available. The Outer Marker serves as a significant point in the approach path where the aircraft can confirm its position and establish its approach settings. When the inner marker is not available, relying on the Ident OM enhances safety by providing guidance and ensuring that the aircraft is correctly tracking towards the runway.

While visual approach lights, surrounding landmarks, and controller clearances can assist in navigation and situational awareness, they do not provide the precise technical reference necessary for radar navigation that the Ident OM offers. Thus, having the Ident OM identifiable is critical for maintaining safe and accurate approach procedures when the inner marker is unavailable.