Plain English Meaning

A pair of light bars next to the runway that tell you, by their colors, if your descent angle to the runway is correct, too steep, or too shallow.

Full Definition

A Visual Approach Slope Indicator system that uses two sets (bars) of light units, one near and one far, beside the runway to show the pilot whether the aircraft is on, above, or below the proper visual glide path to the runway. The pilot reads the two bars as a pair: red over white means on the glide path, white over white means too high, and red over red means too low.

Context Anchor

Seen during the visual part of an instrument approach or during any runway approach where lights are installed.