PAPI stands for Precision Approach Path Indicator. It is a visual landing aid installed beside the runway to help pilots understand whether they are flying too high, too low or on the correct approach path.
A typical four-unit PAPI provides a simple red and white indication. Two white lights and two red lights usually mean the aircraft is on the correct glide path. More white lights indicate the aircraft is high, while more red lights indicate the aircraft is low.
Although a 3-degree approach path is common, the actual PAPI angle is defined by the runway design, obstacle environment and operational requirements. PAPI installation and calibration must therefore follow the applicable standard and authority approval.
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LED PAPI, halogen PAPI, approach lights, AGL power supply, control and monitoring systems.
