Plain English Meaning

A small set of lights next to the runway that tells you, by changing colour, if you are coming in too high, too low, or just right.

Full Definition

A visual landing aid located beside the runway that uses a row of light units to show the pilot whether the aircraft is on, above, or below the correct glide path on final approach. Each light appears either white or red depending on the angle from which it is viewed, and the combination seen by the pilot indicates the approach angle relative to the ideal descent path to the runway.

Context Anchor

Seen during landing, especially on final approach when aligning with the runway and checking descent path.

Derivation

Named for what it does: it precisely indicates the . The word 'precision' signals that it gives finer information than older two- , with four light units producing a clearer picture of how the glide path the pilot is.