Navigation Services
Lighting Systems Group - ALSF-2
A typical ALSF-2 system (High Intensity Approach Lighting System With Sequenced Flashing Lights) consists of 247 steady burning lights: including green threshold lights (49 lights), red side row-bar lamps (9 rows, 54 lamps), and high intensity steady burning white lights (144), plus an additional 15 flashing lights commonly referred to as strobes. The strobes flash in sequence starting with the strobe farthest from the runway and ending with the strobe closer to the runway threshold. The lights are spaced at 100' intervals from the runway threshold outward to 2400'. 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) and provide visual guidance for all landing categories.
FAA Navigation Services Technical Lead: Current Status: Recent contracts have delivered 49 and 25 systems. There are 142 ALSF-2 in the NAS manufactured by Airflo (47), Godfrey (47), NBP (32), GE (6), Heavy Duty Substation (5), Westinghouse Substation (3), Hollingsworth (1), and other (1). Lack of installation funding has caused over 27 ALSF-2 systems to be placed in storage at the Logistics Center until funds are made available.
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Approach Lighting Systems (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. The ALSF-2 provides visual information on runway alignment, height perception, roll guidance, and horizontal references for Category II/III instrument approaches. 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.
