Definition
Configurations of high-intensity lights arranged in a specific pattern extending outward from the approach end of an instrument runway, providing pilots with a visual transition from instrument flight to visual flight during the final stages of an approach. Approach light systems vary in length, configuration, and capability, ranging from simple non-precision systems to full precision systems with sequenced flashing lights and threshold identification.
Plain English
A pattern of bright lights laid out in a line leading up to the start of a runway. They help a pilot see the runway and line up with it when descending through low cloud or poor visibility.
Context Anchor
Pilots encounter approach light systems during the final part of an arrival, especially at night, in haze, or when cloud cover makes the runway hard to see at first.
Derivation
Approach comes from older French and Latin roots meaning “to come near.” In aviation, it points to the part of flight where the aircraft is coming near the runway. That helps explain why these lights are placed before the runway, where the pilot is approaching it.
Why Pilots Care
They allow a pilot to confirm runway alignment and position early enough to make a safe landing decision or execute a missed approach, directly reducing the chance of runway misalignment or controlled flight into terrain.
Analogy
They work like a lighted path leading up to a doorway in the dark: the lights do not land the airplane for you, but they help you find the correct direction and entrance.
Intuition Check
Do not think of these as just any lights you see while approaching an airport. An approach light system is a specific installed pattern of lights tied to a runway and used to guide the final part of landing.
Example Sentence 1
After breaking out of the clouds at 400 feet, the pilot saw the approach light system and continued the descent toward the runway.
Example Sentence 2
The pilot used the sequenced flashing lights of the approach light systems to judge the remaining distance to the runway threshold.