Definition
High-intensity white strobe lights installed along the approach lighting system that flash in rapid sequence from the outermost light toward the runway threshold, creating a visible 'ball of light' that travels toward the runway approximately twice per second. They guide pilots to the runway during instrument approaches in low-visibility conditions.
Plain English
A line of bright strobe lights leading up to the runway that flash one after another, fast, so it looks like a ball of light is racing toward the runway. The motion points the pilot to where the runway begins.
Context Anchor
Seen in approach lighting system descriptions and during instrument approaches to runways equipped with these lights, especially at night or in reduced visibility.
Derivation
Sequenced' comes from Latin sequi, meaning 'to follow.' The lights literally follow one another in order, which produces the apparent motion toward the runway.
Why Pilots Care
They provide positive visual identification of the runway environment and help maintain alignment when transitioning from instruments to visual references.
Analogy
They work like a short line of lights that “chase” in one direction, pointing your eyes toward where you need to go.
Intuition Check
Do not read this as just “lights that flash.” In this context, sequenced means the flashes happen in a planned order, creating a direction cue toward the runway.
Example Sentence 1
Breaking out of the clouds at minimums, the pilot picked up the sequenced flashing lights pointing the way to the runway.
Example Sentence 2
During the approach briefing, the crew confirmed that the runway was equipped with sequenced flashing lights for better acquisition in fog.