Definition
A configuration of high-intensity lights arranged in a specific pattern extending outward from the runway threshold along the extended runway centerline. The system provides visual guidance during the final segment of an instrument approach, helping the pilot transition from instrument references to visual references in order to land.
Plain English
A line of bright lights leading up to the runway, designed to help pilots find the runway and line up with it when visibility is poor.
Context Anchor
Seen during final approach, on airport lighting information, and in instrument approach procedures for runways that have approach lighting installed.
Why Pilots Care
Provides critical alignment cues before the runway itself becomes visible, reducing the chance of runway misalignment or controlled flight into terrain.
Intuition Check
Do not think of the ALS as just ordinary runway edge lights. It is a separate light pattern before the runway that leads your eyes toward the landing end.
Example Sentence 1
Breaking out of the clouds at minimums, the captain identified the approach light system and continued the descent toward the runway.
Example Sentence 2
In low visibility the approach light system helped the pilot locate the runway early and make a smooth landing.