This glossary is written for virtual airline and flight simulation use within Virtual Air Canada Airline. It is not intended as a real-world aviation reference.
PAPI
Precision Approach Path Indicator
A Precision Approach Path Indicator is a visual ground-based approach aid installed alongside the runway threshold that provides pilots with glidepath guidance during approach and landing. The system consists of four lights arranged in a horizontal bar on the left side of the runway. Each light unit produces either a white beam (above glidepath) or a red beam (below glidepath) depending on the viewing angle. By counting the combination of red and white lights, a pilot can instantly determine their vertical position relative to the correct approach path.
The standard PAPI indications are: four white lights (significantly above glidepath), three white and one red (slightly above), two white and two red (on glidepath), one white and three red (slightly below), and four red lights (dangerously below glidepath). Most PAPIs are calibrated to a 3-degree glidepath, matching the standard ILS glideslope angle, though some runways use different angles to clear obstacles. PAPI is used as a primary approach aid at runways without ILS and as a backup visual reference at fully-equipped instrument runways during visual approaches.