The visual approach slope indicator (VASI) is a system of lights on the side of an airport runway threshold that provides visual descent guidance information during final approach. These lights may be visible from up to 8 kilometres (5.0 mi) during the day and up to 32 kilometres (20 mi) or more at night.
Standard visual approach slope indicator (circled in red)Working VASIComparison of PAPI, VASI, and OLS meatball and datum lights (not to scale)
Basic visual approach slope indicators consist of one set of lights set up 7 metres (23 ft) from the start of the runway. Each light is designed so that it appears as either white or red, depending on the angle at which it is viewed. When the pilot is approaching the lights at the proper angle, meaning the pilot is on the glide slope, the first set of lights appears white and the second set appears red. When both sets appear white, the aircraft is too high, and when both appear red it is too low. This used to be the most common type of visual approach slope indicator system; however, it is being phased out and replaced by precision approach path indicators (PAPIs), which are closer together and therefore more efficient to sight and maintain.
A mnemonic to remember the colors and their meaning is:
White over White, you're high as a kite / you'll fly all night / check your height / you're out of sight / too much height.
Red over White, you're alright / height's alright.
Simple VASIs are obsolete, having been deleted from ICAO Annex 14 in 1995, however T-VASIS and AT-VASIS are still specified. T-VASIS is defined as twenty light units symmetrically disposed about the runway centre line in the form of two wing bars of four light units each, with bisecting longitudinal lines of six lights". AT-VASIS is an abbreviated form of T-VASIS, defined as "ten light units arranged on one side of the runway in the form of a single wing bar of four light units with a bisecting longitudinal line of six lights."[2]
Tri-color VASIedit
Tri-color VASI
A tri-color system consists of a single-light unit projecting a three-color visual approach path. Below the glide path is indicated by red, on the glide path is indicated by green, and above the glide path is indicated by amber. When descending below the glide path, there is a small area of dark amber. Pilots should not mistake this area for an “above the glide path” indication.[3]
Pulsating VASIedit
Pulsating VASI
The pulsating visual approach slope indicator (PVASI) is a system similar in purpose to a VASI, but only consists of one piece of equipment. It indicates the pilot's height on approach with a mix of red and white, steady and pulsating light. Pulsating white light indicates that the aircraft is too high, whereas steady white indicates being on the glide path. Steady red light is meant to show a position only slightly below glide path, with pulsating red light being indicative of a position well below glide path.[4] This type of system is less prevalent than other visual glide slope indicators like regular VASIs or PAPIs, as of May 2022 there were only 84 PVASIs installed at 51 airports and heliports in the United States and its territories according to Federal Aviation Administration data, compared to 6730 PAPIs and 623 VASIs.[5]
^"Annex 14 to the Convention on International Civil Aviation. Aerodromes. Volume 1, Aerodrome Design and Operations" (PDF). ICAO. Retrieved 1 March 2023. deletion of specifications on VASIS (AVASIS) and 3-BAR VASIS (3-BAR AVASIS)
^"Chapter 14: Airport Operations". Pilot's Handbook of Aeronautical Knowledge (FAA-H-8083-25C ed.). Federal Aviation Administration. 2023-07-17. p. 17.
^DoD Flight Information Publication (Enroute) - Flight Information Handbook(PDF). St. Louis, Missouri: National Geospatial-Intelligence Agency. 2018. pp. B-34. (PDF) from the original on 2021-08-29.
visual, approach, slope, indicator, vasi, redirects, here, other, uses, vasi, this, article, needs, additional, citations, verification, please, help, improve, this, article, adding, citations, reliable, sources, unsourced, material, challenged, removed, find,. VASI redirects here For other uses see Vasi This article needs additional citations for verification Please help improve this article by adding citations to reliable sources Unsourced material may be challenged and removed Find sources Visual approach slope indicator news newspapers books scholar JSTOR November 2012 Learn how and when to remove this template message The visual approach slope indicator VASI is a system of lights on the side of an airport runway threshold that provides visual descent guidance information during final approach These lights may be visible from up to 8 kilometres 5 0 mi during the day and up to 32 kilometres 20 mi or more at night Contents 1 Standard VASI 2 Tri color VASI 3 Pulsating VASI 4 See also 5 References 6 External linksStandard VASI edit nbsp Standard visual approach slope indicator circled in red nbsp Working VASI nbsp Comparison of PAPI VASI and OLS meatball and datum lights not to scale Basic visual approach slope indicators consist of one set of lights set up 7 metres 23 ft from the start of the runway Each light is designed so that it appears as either white or red depending on the angle at which it is viewed When the pilot is approaching the lights at the proper angle meaning the pilot is on the glide slope the first set of lights appears white and the second set appears red When both sets appear white the aircraft is too high and when both appear red it is too low This used to be the most common type of visual approach slope indicator system however it is being phased out and replaced by precision approach path indicators PAPIs which are closer together and therefore more efficient to sight and maintain A mnemonic to remember the colors and their meaning is White over White you re high as a kite you ll fly all night check your height you re out of sight too much height Red over White you re alright height s alright Red over Red you re dead pilot s dead 1 White over Red is not possible Simple VASIs are obsolete having been deleted from ICAO Annex 14 in 1995 however T VASIS and AT VASIS are still specified T VASIS is defined as twenty light units symmetrically disposed about the runway centre line in the form of two wing bars of four light units each with bisecting longitudinal lines of six lights AT VASIS is an abbreviated form of T VASIS defined as ten light units arranged on one side of the runway in the form of a single wing bar of four light units with a bisecting longitudinal line of six lights 2 Tri color VASI edit nbsp Tri color VASIA tri color system consists of a single light unit projecting a three color visual approach path Below the glide path is indicated by red on the glide path is indicated by green and above the glide path is indicated by amber When descending below the glide path there is a small area of dark amber Pilots should not mistake this area for an above the glide path indication 3 Pulsating VASI edit nbsp Pulsating VASIThe pulsating visual approach slope indicator PVASI is a system similar in purpose to a VASI but only consists of one piece of equipment It indicates the pilot s height on approach with a mix of red and white steady and pulsating light Pulsating white light indicates that the aircraft is too high whereas steady white indicates being on the glide path Steady red light is meant to show a position only slightly below glide path with pulsating red light being indicative of a position well below glide path 4 This type of system is less prevalent than other visual glide slope indicators like regular VASIs or PAPIs as of May 2022 there were only 84 PVASIs installed at 51 airports and heliports in the United States and its territories according to Federal Aviation Administration data compared to 6730 PAPIs and 623 VASIs 5 See also editLeading lights similar aid to navigation Pilot controlled lighting PCL Precision approach path indicator PAPI Runway end identifier lights REIL Runway edge lights HIRL MIRL LIRL Approach lighting system ALS Optical landing systemReferences edit Skybrary Annex 14 to the Convention on International Civil Aviation Aerodromes Volume 1 Aerodrome Design and Operations PDF ICAO Retrieved 1 March 2023 deletion of specifications on VASIS AVASIS and 3 BAR VASIS 3 BAR AVASIS Chapter 14 Airport Operations Pilot s Handbook of Aeronautical Knowledge FAA H 8083 25C ed Federal Aviation Administration 2023 07 17 p 17 DoD Flight Information Publication Enroute Flight Information Handbook PDF St Louis Missouri National Geospatial Intelligence Agency 2018 pp B 34 Archived PDF from the original on 2021 08 29 Airport Data and Information Portal adip faa gov Federal Aviation Administration Retrieved 2022 05 09 FAA Aeronautical Information Manual Chapter 2 Aeronautical Lighting and Other Airport Visual Aids Section 1 Airport Lighting Aids External links editFAA Aeronautical Information Manual Retrieved from https en wikipedia org w index php title Visual approach slope indicator amp oldid 1206071127, wikipedia, wiki, book, books, library,
