The AC Spec PAPI (Precision Approach Path Indicator) is a visual guidance lighting system that provides positive visual indication of an aircraft's position relative to the optimal glide slope during final approach to the runway.
FAA AC 150/5345-28 (current edition)
ICAO Annex 14
The PAPI is a visual aid that provides guidance information to help a pilot acquire and maintain the correct approach (in the vertical plane) to an airport. It is generally located beside the runway approximately 300 meters (1000 feet) beyond the landing threshold of the runway. The PAPI System consists of a three-lamp Light Housing Assembly (LHA) as the main component. Additional components include a Power and Control Unit, Series Circuit Lamp, shorting device with integral tilt switch, and an Aiming Instrument Set.
Low Power Consumption - The PAPI is low power consumption energy efficient system. Each Lamp Housing Assembly draws a nominal 300w.
Physical Size - The size and weight of the PAPI Lamp Housings is up to 30% less than other systems.
Tool-Less Maintenance - Most routine service components can be maintained without the use of hand tools.
Universal Mounting - The Lamp Housing Assembly can be mounted on wide range of 3-leg mounting patterns. Standard mounting is on a 22” across the front and 16” front to back. Four additional mounting configurations are available for retrofit on most 3-leg PAPI existing mounts.