The PAPI (Precision Approach Path Indicator) system is a vital airfield lighting aid designed to assist pilots in visually determining their aircraft’s vertical position relative to the optimal glide slope during final approach to the runway. This system provides an immediate and unmistakable color-based visual cue—white when the aircraft is above the correct glide slope and red when it is below. As the aircraft's vertical position shifts, the perceived color changes instantaneously, offering precise feedback that allows for real-time altitude correction during approach.
The L-880 PAPI system features four units arranged in a straight line, each containing either two or three high-output 200-watt lamps. These units generate a defined beam of light that is split into a white upper segment and a red lower segment. The exacting beam transition and sharp color contrast enable pilots to make accurate altitude judgments with ease.
The system is available in two versions: Style A and Style B. Style A includes a Power and Control Unit (PCU) equipped with a built-in photocell for automatic day/night intensity adjustment. This version can be triggered remotely via an L-854 radio controller, which receives signals from approaching aircraft, ensuring optimal brightness levels for varying visibility conditions. Style B, on the other hand, is powered through an L-828 constant current regulator and is designed without a PCU. It includes additional design features like a lamp bypass circuit and tilt switch indicator lights, but does not come with isolation transformers or connector kits, which must be ordered separately.
The PAPI system meets all relevant industry standards and certifications, including FAA AC 150/5345-28 (Current Edition: L-880 and L-881) and ICAO Annex 14. It is ETL certified and designed to meet ICAO recommendations for approach lighting precision, offering a sharp signal transition of 3 minutes of arc and allowing for precise alignment using a ±2 minutes of arc setting tool. Style B models are further enhanced with lamp bypass circuitry and visual indicators for tilt switches to ensure operational reliability.
Equipped with 1500-hour rated lamps and engineered for long-term service with minimal maintenance, the PAPI system remains a trusted and essential component of runway approach guidance infrastructure at airports worldwide.
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