For precision approaches, the ALS extends from the landing threshold to what distance?

• A. 2,400-3,000 ft
• B. 1,400-1,500 ft
• C. 3,800-4,000 ft
• D. 4,000-4,500 ft

Answer: (C)

The lighting system on a precision approach is designed to give a continuous visual cue from the threshold far enough out so a pilot can transition from instrument references to visual cues and set up a stabilized descent. That visual lead is typically about 4,000 feet from the threshold, so extending the ALS to roughly 3,800–4,000 feet provides a reliable path of lights (including the sequencing lights and crossbars) that guide the final approach all the way to the runway. Shorter extents wouldn’t offer as much lead-in for a smooth, stabilized approach, and longer extents aren’t standard for most installations.