What is the purpose of an Approach Lighting System (ALS), and how long does it extend?
Answer
ALS provides the basic means to transition from instrument flight to visual flight for landing. For precision instrument runways, the system extends 2,400–3,000 feet into the approach area. For nonprecision instrument runways, it extends 1,400–1,500 feet. Some systems include sequenced flashing lights that appear to travel toward the runway twice per second.
AIM 2-1-1
Read the full regulation — AIM 2-1-1
2-1-1. Approach Light Systems (ALS) a. ALS provide the basic means to transition from instrument flight to visual flight for landing. Operational requirements dictate the sophistication and configuration of the approach light system for a particular runway. b. ALS are a configuration of signal lights starting at the landing threshold and extending into the approach area a distance of 2400 -3000 feet for precision instrument runways and 1400 -1500 feet for nonprecision instrument runways. Some systems include sequenced flashing lights which appear to the pilot as a ball of light traveling towards the runway at high speed (twice a second). (See FIG 2-1-1.)
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