General

APAPI consists of two light units situated on the left side of the runway in the form of a wing bar. When the pilot is:

  • Above the approach slope, both units show white. Slightly above the approach slope, the one unit nearest the runway edge shows red and the other three show white
  • On or close to the approach slope, the unit nearer to the runway edge shows red and the unit farther from the runway edge shows white. Slightly below the approach slope, the three units nearest the runway edge show red and the other shows white
  • Below the approach slope, all units show red.

A VASIS consists of a series of lights visible from approximately 4 NM and designed to provide visual indications of the desired approach slope to a runway (usually 3°). At a certified airport, aircraft following the on-slope signal are provided with safe obstruction clearance to a minimum of 6° on either side of the extended runway centreline out to 7.5 km (4.1 NM) from the runway threshold. Newly certified airports are commonly protected out to 8° on each side of the extended runway centreline. Exceptions will be noted in the CFS. Descent using VASIS should not be initiated until the aircraft is visually aligned with the runway centreline.

The VASI and PAPI have lights normally situated on the left side of the runway only. When available strip widths preclude the use of a full system, an abbreviated approach slope indicator, AV or AP, consisting of only two light units, may be installed.

Where a PAPI or VASI is provided on a precision approach runway and has not been harmonized with a vertical guidance signal, it will be turned off in weather conditions involving a ceiling of less than 500 ft (150 m) and/or visibility less than 1 mi., unless specifically requested by the pilot. This is to avoid possible contradiction between the electronic precision approach vertical guidance and visual (VASI/PAPI) glide slope signal.

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