Led light sources in the approach slope indicators and their visibility in inhomogeneous atmosphere

The PAPI (Precision Approach Path Indicator) optical system with incandescent light sources (halogen airport lamps) is already an integral part of the airport lighting system (ALS), both stationary and mobile airfields of The Czech Air Force. The development unambiguously directs to the replacement of the incandescent light sources in the APAPI (Abbreviated PAPI) an optical unit with LED (Light-Emitting Diodes) light source with the high luminous efficacy. Considerable technological and light differences among the LED light sources and the halogen airport lamps lead to high difficulties of the theoretical design, development and construction of the new LED APAPI optical system assembly. This article illustrates the shape, light efficiency and spectral characteristics, differences among the LED light sources and the halogen airport lamps and a possible way of APAPI optical system design with LED light sources.