Approach lighting system

An approach lighting system, or ALS, is a lighting system installed on the approach end of an airport runway and consists of a series of lightbars, strobe lights, or a combination of the two that extends outward from the runway end. ALS usually serves a runway that has an instrument approach procedure (IAP) associated with it and allows the pilot to visually identify the runway environment once he or she has arrived at a prescribed point on an approach. Several ALS configurations are recognized by the International Civil Aviation Organization (ICAO); however, non-standard ALS configurations are installed at some airports. Typically, approach lighting systems are high-intensity. Many approach lighting systems are also complemented by various on-runway light systems, such as Runway End Identification Lights (REIL), Touchdown Zone Lighting (TDZL), and High-Intensity Runway Edge Lights (HIRL). The most common approach light system configurations include:

• MALSR: Medium-intensity approach light system with Runway Alignment Indicator Lights (RAIL)
• MALSF: Medium-intensity approach light system with Sequenced Flashers
• SALS: Short approach light system
• SSALS: Simplified Short approach light system
• SSALR: Simplified Short approach light system with Runway Alignment Indicator Lights
• SSALF: Simplified Short approach light system with Sequenced Flashers
• ODALS: Omnidirectional approach light system
• ALSF-1: Approach light system configuration 1
• ALSF-2: Approach light system configuration 2
• ICAO-1: ICAO-compliant configuration 1
• ICAO-2: ICAO-compliant configuration 2
• LDIN: Lead-in lighting