PAPI / APAPI Precision Approach Path Indicator (ATG Airports, distributed by Vardhman Airport Solutions)

The PAPI (Precision Approach Path Indicator) is a four-unit light array installed perpendicular to the runway edge — normally to the left, 15 m from the runway edge with units spaced 9 m apart — that gives a pilot an unambiguous colour-coded position signal relative to the designated glideslope throughout the approach phase. Each unit emits a high-intensity split beam: the lower segment red, the upper white, with the colour transition occurring within three minutes of arc for immediate pilot recognition. The four units are set to progressively increasing transition angles; the nominal glidepath (typically 3°) sits midway between the second and third units, giving the familiar two-red/two-white indication when on-slope. The ATG Airports design incorporates an ICAO 30° wide beam to exploit MLS alignment capability and provide visual guidance through to touchdown. Circulating internal airflow and lens heaters minimise condensation effects, and a frangible three-leg mounting ensures ILS critical area compliance regardless of mounting height. The system is designed for service-access via rear hatches without special tooling, making periodic lamp change straightforward for airfield teams. The APAPI (Abbreviated PAPI) variant uses two units and is suited to lower-traffic aerodromes, remote strips, heliports, or temporary/emergency deployments where the full four-unit installation is not warranted. Both variants suit CAT I, II, and III all-weather operations. They are well-matched to high-ambient environments — the beam intensity and contrast hold under bright desert sun, making them standard specification for Gulf and South Asian airport expansions.