Understanding PAPI: The Precision Approach Path Indicator

Image Source: Tswgb, Public domain, via Wikimedia Commons

For aviation enthusiasts, there’s nothing quite like the precision and skill involved in a perfect landing. One of the key tools pilots rely on to achieve this is the Precision Approach Path Indicator, commonly known as PAPI.

What is PAPI?

PAPI is a visual aid located alongside an airport runway that helps pilots maintain the correct glide slope during their approach. It consists of a row of four light boxes, typically positioned to the left of the runway. By observing the combination of red and white lights, pilots can determine whether they are too high, too low, or on the correct approach path.

Image Source: Pilot Mall

• All White Lights: Too high – the aircraft is above the glide path.

• Three White, One Red: Slightly high.

• Two White, Two Red: On the correct glide path.

• One White, Three Red: Slightly low.

• All Red: Too low – immediate correction required.

This simple but effective system has become an essential tool at airports worldwide, especially for smaller airports without advanced instrument landing systems.

Why Avgeeks Should Care

PAPI lights are not just a technical necessity—they’re a fascinating part of aviation infrastructure. Watching an aircraft adjust its glide path based on the PAPI lights is a small but critical piece of the landing puzzle, and it’s something every avgeek can appreciate.

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