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Good moaning
[[Image:Jersey Airport.JPG|thumb|250px|The PAPI can be seen to the right of the runway. The greater number of red lights visible means that the aircraft is below the glideslope.]]
[[Image:PAPI M39.jpg|thumb|250px|Individual Precision Approach Path Indicator]]
The '''Precision Approach Path Indicator (PAPI)''' is a light system positioned beside the [[runway]] that consists of two, three, or four boxes of lights that provide a visual indication of an aircraft's (fixed wing or rotor wing) position on the [[glidepath]] for the associated runway. The [[Federal Aviation Administration|FAA]] standard for the PAPI is the same as the [[ICAO]]'s standard [[VASI|Visual Approach Slope Indicator]].
The PAPI is usually located on the left side of the runway and can be seen up to five miles during the day and twenty miles at night. It has two or four lights installed in a single row instead of far and near bars that would be characteristic of Visual Approach Slope Indicator (VASI).
Each box of lights is equipped with an optical apparatus that splits light output into two segments, red and white. Depending on the angle of approach, the lights will appear either red or white to the [[aviator|pilot]]. Ideally the total of lights will change from white to half red, moving in succession from left to right side. The pilot will have reached the normal glidepath (usually 3 degrees) when there is an even split in red and white lights. If an aircraft is beneath the glidepath, red lights will outnumber white; if an aircraft is above the glidepath, more white lights are visible.
During aircraft [[descent (aircraft)|descent]], this system, along with other airport lights, may be [[Pilot Controlled Lighting|activated by the pilot]] by keying the aircraft microphone with the aircraft's communication radio tuned to the [[CTAF]].
==See also==
* [[Approach Lighting System]]
* [[Pilot Controlled Lighting]] (PCL)
* [[Visual Approach Slope Indicator]] (VASI)
* [[Instrument Landing System]]
* [[Runway End Identification Lights]] (REIL)
* [[Runway Edge Lights]] (HIRL, MIRL, LIRL)
[[Category:Aviation terminology]]
[[Category:Airport terminology]]
[[da:Precision Approach Path Indicator]]
[[es:Indicador de Trayectoria de Aproximación de Precisión]]
[[fr:Precision Approach Path Indicator]]
[[it:Precision Approach Path Indicator]]
[[nl:Precision Approach Path Indicator]]
[[ja:PAPI]]
[[pt:PAPI]]
[[sv:PAPI]]
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