Precision approach path indicator: Difference between revisions

Revision as of 05:27, 17 March 2006

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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 airplane's 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 Glide 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 upperangle of segmentapproach, orthe rightlights segmentwill ifappear either red of white to the [[aviator|pilot]. Ideally the total of lights arewill change from white to half red, moving in series)succession andfrom whiteright to left side. The Dependingpilot onwill have reached the viewing,normal glidepath (usually 3%) when there is an even split in red and thuswhite lights. If an airplane is beneath the descentglidepath, angle,red a [[aviator|pilot]]lights will seeoutnumber eitherwhite; theif redan orairplane is above the glidepath, more white portionlights are visible.

A normal glidepath (usually 3%) is indicated by an even split in red and white lights. If an airplane is beneath the glidepath, more red lights are visible to the pilots; if an airplane is above the glidepath, more white lights are visible.

During aircraft [[descent_(aircraft)|descent]], this system, along with other airport lights, may be activated by the pilot by keying the airplane microphone with the airplane's communication radio tuned to the [[CTAF]].