Precision approach path indicator: Difference between revisions

Revision as of 20:48, 28 February 2023

Revision as of 20:50, 28 February 2023

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The PAPI is a light array positioned beside the [[runway]]. It normally consists of four equi-spaced light units color-coded to provide a visual indication of an aircraft's position relative to the designated [[glideslope]] for the runway. An abbreviated system (APAPI) consisting of two light units can be used for some categories of aircraft operations. The international standard for PAPI is published by the [[International Civil Aviation Organization]] (ICAO) in ''Aerodromes, Annex 14 to the Convention on International Civil Aviation, Volume 1, Chapter 5''. National regulations generally adopt the standards and recommended practices published by ICAO. An earlier glideslope indicator system, the [[visual approach slope indicator]] (VASI) is now obsolete and was deleted from ''Annex 14'' in 1995. The VASI only provided guidance down to heights of {{convert|60|m|ft|sigfig=1}} whereas PAPI provides guidance down to flare initiation (typically {{convert|15|m|ft|sigfig=1|disp=x|, or }}).{{cn|date=February 2023}}

PAPIs are calibrated relative to the Minimum Eye Height over Threshold (MEHT). Pilots in somecertain aircraft may see a "slightly low" indication even though they are on the ILS glideslope., <ref>https://publicapps.caa.co.uk/docs/33/CAP637%20Visual%20Aids%20Handbook.pdf</ref> when pilot eye height is above the ILS receiver antenna.<ref>https://www.airbus.com/sites/g/files/jlcbta136/files/2021-11/Airbus-Aircraft-Data-for-Visual-Aids-Calibration-v5.0.pdf</ref>

The PAPI is usually located on the left-hand side of the runway at right angles to the runway center line. The units are spaced 9 meters apart with the nearest unit 15 meters from the runway edge. A PAPI can, if required, be located on the right-hand side of the runway. The red lights are always on the side closest to the runway. If the PAPI is on the right-hand side of the runway (non-standard), the red lights will be on the left. At some locations PAPIs are installed on both sides of the runway but this level of provision is beyond the requirements of ICAO.