Patent GB-644512-A (GB)
Title: Improvements in or relating to landing approach light systems for airports
IPC: B64F1/20
Filed: 1948-03-16
Abstract: 644,512. Visual landing aids for aircraft. WESTINGHOUSE ELECTRIC INTERNATIONAL CO. March 16, 1948. No. 7870. Convention date. Aug. 7, 1947. [Class 118 (ii)] A landing approach light system to facilitate the landing of aircraft under varying weather conditions comprises a plurality of light units spaced along a line parallel to the extended centre line of the runway and extending outwardly from the end of the runway, the lighting units being of two different types, one of which produces a flashing beam and the other either a flashing or a steady beam of light. The second type of light units may radiate coloured light and are arranged alternately with the first, as shown by the different forms of representation in Fig. 1. The line of lights may extend over a distance of about ¥ of a mile, the spacing being graduated, for example as indicated, and the light beams be directed at a predetermined area beyond the outer end of the line. A line of lights 15 about 200 feet apart may be placed down each side of the runway and other light units grouped round the end of the runway 11. For example, a row of threshold lights 16 arranged with a gap at the runway centre may be provided and angle of approach indicators 17 which project a three-coloured beam showing green if the plane from which they are viewed is on the correct glide path, yellow if it is too high, and red if it is too low. The lights 17 are switched on for a second and off for half a second to avoid confusion with the other lights of the system. Luminous tubes arranged to form a green arrow 21 and a large red cross 19 may be switched on alternatively to show that the runway is or is not available for landing. The flashing light units may consist of single Kryptron discharge lamps arranged with a reflector and power supply unit in a suitable housing adjustably supported on a base (Figs. 3 and 4, not shown). The flash or continuous light units may likewise consist of a number of parallel red neon tubular lamps arranged in the depressions of a corrugated reflector in a similar housing (Figs. 5 and 6, not shown). Control of the lighting system may be from a central position and the flashing may be arranged to be at either of two intensities. The units operable continuously may also operate at any of three different continuous intensities. Such a central control system is described with reference to Figs. 7, 8 and 9 (not shown), which show both the power supply arrangements and the switch and relay circuits necessary. Each lamp unit power supply is fed with alternating current and includes a step-up transformer and rectifier. For flashing operation a condenser bank of a size adjustable for high or low flash intensity is charged from the rectifier and the discharge in the lamp across which the condensers are connected initiated by a separate triggering circuit. All the triggering circuits are controlled by a motor-driven time control device and in a preferred form the light units are flashed in sequence so as to simulate a flash of lightning travelling towards the end of the runway, the operation may be cyclic at a periodicity dependent on the motor drive. Indicator lights dependent for their operation on the current flow in the power supply feeders may be provided at the control position.