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Aviation History
1958
1958 - 0461.PDF
477 FLIGHT, 11 April 1958 '"ffffll "Flight" photograph Helicopter Fly-by-night B.E.A. APPROACH-LIGHTING SYSTEM INSTALLED AT GATWICK EMERGING from cloud at about 450ft on a night approachto Gatwick in a B.E.A. Sycamore two weeks ago, a Flightstaff-member was well able to appreciate the value of the helicopter approach-lighting system now installed there. Demon- strated for the first time on this occasion, it has been devised to permit night and bad weather operations in visibility as low as 100 yd; and the pattern is designed to fit into the standard I.A.T.A. heliport of 400ft x 200ft. Extensive night-flying trials have been carried out by the B.E.A. helicopter experimental unit, in combination with the airline's project and development branch, over the past few years. The night-flying installation was developed by the project and develop- ment branch, and the prototype system has been built and installed at Gatwick by the General Electric Co., Ltd. The most important requirements for such a lighting pattern, according to B.E.A., are that it should give an immediate visual indication of the altitude and flight attitude of the helicopter; and, by means of good overall lighting of the landing pad, should provide textural guidance and ground-plan illumination while landing. Other desirable features are that the pattern should clearly define the approach direction, and also define the boun- daries of the landing site. To meet these requirements a basic "Cross of Lorraine" pattern was derived from the well-known Calvert system of high-intensity runway approach lighting. The geometry of the cross is illustrated in the diagram below: all crossbar lights are flush with the ground, as the actual landing is made on top of the main intersection of the lights. Approaches can be made in either of two opposite direc- tions, with the downwind crossbar extinguished. The addition of two further rows of lights (shown dotted below) at the ends of the main crossbar would permit four different approach directions. This basic pattern enables the pilot to assess his drift, heading and roll attitude, and also provides a distinctive identification of the site. Floodlights are provided at each end of the site. The downwind floodlights are switched on for a landing approach, illuminating the ground area and giving the pilot indication of his height and relative movement. The type of approach developed by B.E.A. involves a forward speed of 20 kt and rate of descent of 750ft/min, giving a 20-degree angle of descent. The helicopter's angle of approach is indicated to the pilot by conventional three-colour angle-of-approach indi- cators located at each end of the main crossbar. Also included in the complete lighting system, but not at present installed, are blue boundary lights; a high-intensity identification beacon; and a chequerboard form of ground marking which improves the effect of floodlighting on tarmac. Facilities are included in the present installation for controlling the brightness of approach lights and floodlights. A special large-scale version of the Decca Navigator Flight Log is fitted to all B.E.A. helicopters and is used for flying (normally under I.F. conditions) the initial approach pattern. Transition from instruments to visual flying is normally made at a height of 150ft, when the machine is about 150yd from the site. WIND i| i 400 ft 8 8 b a "8 8 a O 110ft 220ft ^ -:: The heading photo- graph shows a B.E.A. Whirlwind landing at Gatwick with the aid of the new approach- lighting system. Left, the geometric layout of the light- ing pattern. Right, one of the angle- of-approach indi- cator lights. "Flight" photograph
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