Plain English Meaning
Two bright strobe lights, one on each side of the start of the runway, that flash together to help a pilot quickly spot exactly where the runway begins.
Full Definition
A pair of synchronized flashing white lights installed on each side of the runway threshold, used to provide rapid and positive identification of the approach end of a runway. They are particularly useful where the runway is surrounded by a large number of other lights, where it lacks contrast with the surrounding terrain, or during reduced visibility.
Context Anchor
Seen during airport lighting discussions and when approaching a runway at night, in haze, or at an unfamiliar airport.
Why Pilots Care
They allow quick positive identification of the runway end, reducing the chance of landing short or on the wrong .