Precision Approach Path Indicator facts for kids

Individual precision approach path indicator

The Precision Approach Path Indicator (PAPI) is a special light system at airports. It helps pilots land their planes safely. Think of it like a traffic light for planes, but instead of red, yellow, and green, it uses red and white lights. These lights tell the pilot if their plane is at the perfect height to land on the runway.

What is a PAPI System?

A PAPI system is usually found next to the runway, close to where planes touch down. Its main job is to guide pilots so they approach the airport at the correct angle. This angle is super important for a smooth and safe landing. The PAPI creates a beam of light that changes color depending on the plane's height. This way, pilots know if they are too high, too low, or just right.

How PAPI Lights Guide Pilots

The PAPI system uses a row of four special lights. The colors of these lights change based on the plane's position relative to the ideal landing path. Pilots look at these lights as they get closer to the runway.

Understanding the Light Signals

The combination of red and white lights tells the pilot exactly where their plane is on the approach path:

• Too High: If the plane is above the correct path, the pilot will see more white lights than red.
  • If the plane is a little too high, they will see three white lights and one red light.
  • If the plane is much too high, all four lights will appear white. This means the pilot needs to fly lower.

• Just Right: When the plane is on the perfect landing path, the pilot will see an equal number of white and red lights.
  • This means two white lights and two red lights. This ideal path is usually set at an angle of about 3 degrees from the airport's main axis. This is the goal for a safe and smooth landing.

• Too Low: If the plane is below the correct path, the pilot will see more red lights than white.
  • If the plane is a little too low, they will see three red lights and one white light.
  • If the plane is much too low, all four lights will appear red. This tells the pilot they need to fly higher.

PAPI Rules and Standards

The rules for how PAPI systems work, including how bright the lights should be and where they should be placed, are set by an international organization. This organization is called the International Civil Aviation Organization (ICAO). Their rules help make sure that PAPI systems are the same all over the world, which makes flying safer for everyone.

Images for kids

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  The PAPI can be seen to the right (non-standard) side of the runway. The aircraft is slightly below the glideslope.