Final answer:
A Localizer approach differs from an ILS approach regarding the un-serviceability of HIAL, with different visibility requirements. The visibility requirements for a Localizer approach are specified separately and may be the same or different from an ILS approach.
Step-by-step explanation:
The question is asking about the difference between a Localizer approach and an ILS (Instrument Landing System) approach regarding the un-serviceability of HIAL (High Intensity Approach Lighting). In both approaches, the visibility requirements may vary depending on the specific conditions and restrictions imposed.
In an ILS approach, the HIAL is important for maintaining visibility during the final approach segment. If the HIAL is unserviceable, the visibility requirements may be higher, and the pilot may need to refer to alternative sources, such as runway edge lights, to maintain adequate visual contact with the runway.
On the other hand, in a Localizer approach, which relies on the localizer component of the ILS, the visibility requirements are not directly dependent on the HIAL. The visibility requirements for a Localizer approach are specified separately and may be the same or different from an ILS approach, depending on the specific regulations and operating procedures.