Editing Precision approach path indicator (section)

==History==
The precision approach path indicator system was first devised in 1974 by Tony Smith and David Johnson at the [[Royal Aircraft Establishment]] in Bedford, England. It took them a further two years to fully develop the technology. Engineering firm Research Engineers (RE) were also heavily involved in the project, having produced and supplied PAPI units for the first trials that were conducted. The same design is still in use today.<ref>{{cite web |url=http://www.research-engineers.com/about_papi.html |title=Research Engineers PAPI |access-date=2017-05-14 |url-status=dead |archive-url=https://web.archive.org/web/20140125163859/http://research-engineers.com/about_papi.html |archive-date=2014-01-25 }}</ref>

Smith and Johnson's work was honoured by a commendation from the RAE, a Fellowship from the Aeronautical Society, an award from the American Flight Safety Foundation, and a Gold Medal from the British Guild of Air Pilots.{{citation needed|date=March 2023}}

PAPIs were used by NASA's Space Shuttle for its safe landing, for which Johnson was interviewed by UK local news media and TV.{{citation needed|date=March 2023}}

An earlier glideslope indicator system, the [[visual approach slope indicator]] (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 }}).{{citation needed|date=February 2023}}

2008 saw the advent of new PAPI devices manufactured using solid state [[LED lamp]]s instead of [[incandescent lamp]]s. The LEDs produce sufficient brightness to satisfy ICAO light intensity and beamspread standards, and average lifetime with the LED based systems is 50,000 hours or more. By using LEDs, the device's power consumption is lowered considerably. The LED systems run internally on DC voltage, so the DC voltage requirements, along with the LEDs' inherently low power consumption, now allow for solar-powered PAPIs, enabling them to function completely independently of a power grid.<ref>{{cite web |url=http://www.flightlight.com/airportlighting/4.0.1/4.0.1.html |title=Solar PAPI & APAPI (Precision Approach Path Indicator) |access-date=2012-04-10 |url-status=dead |archive-url=https://web.archive.org/web/20111230132434/http://www.flightlight.com/airportlighting/4.0.1/4.0.1.html |archive-date=2011-12-30 }}</ref>

The PAPI system is co-opted for use by the [[final approach (aviation)|Final Approach]] Runway Occupancy Signal (FAROS) system being introduced<ref>{{Cite web|url=http://www.faraim.org/aim/aim-4-03-14-87.html|title=Aeronautical Information Manual (AIM) - Page 87|website=www.faraim.org|access-date=2019-12-24}}</ref> by several major airports in the United States for the purpose of allowing pilots to resolve a [[runway incursion]] without requiring ''a priori'' notice of an occupied runway from the [[control tower]]. In FAROS, automated line-of-sight runway sensors detect if a vehicle has committed a runway incursion, and if so, will flash the PAPI lights to alert the pilot of an aircraft on final approach that the runway is currently occupied. The pilot then becomes responsible for resolving the conflict by notifying the [[air traffic controller]] and executing a [[go-around]]. Once the tower has ascertained that the runway has been cleared, the ground controller resets the PAPI so that landing operations may resume normally.<ref>{{cite web |url=https://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/operations/td/projects/faros/solution/animation.cfm |title=Final Approach Runway Occupancy Signal (FAROS) - Animation |access-date=2010-06-07 |url-status=dead |archive-url=https://web.archive.org/web/20100209024258/https://www.faa.gov/about/office_org/headquarters_offices/ato/service_units/operations/td/projects/faros/solution/animation.cfm |archive-date=2010-02-09 }}</ref><ref>{{cite web |url=https://www.faa.gov/air_traffic/publications/atpubs/aim_html/chap2_section_1.html |title=Section 1. Airport Lighting Aids |access-date=2019-09-19 }}</ref>