Landing light for airport runway - has two prisms to control divergence of beam to suit runway

摘要

The landing light for an airport runway consists of a cast box (1) embedded in the runway with its upper surface (AB) lying flush with the runway surface. An opening in the box (1) is fitted with a glass prism (2) of sufficient thickness to withstand the loads imposed by aircraft wheels. A second prism (18b) is attached to the undersurface of the prism (2). A lamp (F) is fixed at the focus of the elliptical reflector (7) so that the light would be focussed at the second focus (F1). But the prisms (18b) and (2) are so arranged that the beam is refracted and emerges from the box (2) at a convenient angle to suit the requirements of the runway.