AIM Text
- 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.
- 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.)
Source: FAA Aeronautical Information Manual · current edition · paragraph 2-1-1.
The short answer
This AIM section is FAA advisory guidance explaining Approach Light Systems (ALS), the configurations of signal lights that help pilots transition from instrument flight to visual flight for landing. It notes that ALS start at the landing threshold and extend 2,400–3,000 feet for precision runways and 1,400–1,500 feet for nonprecision runways. It supports the visual reference requirements of 14 CFR 91.175.
Research Notes
Common Questions
How far do approach light systems extend from the runway threshold?
ALS are a configuration of signal lights starting at the landing threshold and extending into the approach area a distance of 2,400 to 3,000 feet for precision instrument runways and 1,400 to 1,500 feet for nonprecision instrument runways.
What are the sequenced flashing lights in an approach light system?
Some ALS include sequenced flashing lights that appear to the pilot as a ball of light traveling toward the runway at high speed—twice a second. They help guide the pilot toward the runway during the transition from instrument to visual flight.
What is the purpose of an approach light system?
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.