Weir W.5/W.6 Lateral-Twin Helicopters
Although Weir’s chief designer, Cyril G. Pullin, initially proposed converting the Weir W.4 autogyro into a helicopter using co-axial rotors, the Weir W.5 helicopter (also called the Cierva W.5) was a single-seat twin tandem-rotor helicopter developed by the Cierva Autogiro Company in the United Kingdom in the late 1930s. The W.5, undoubtedly influenced by the Germany’s Focke-Achgelis Fa-61 design then flying, utilized twin-outriggers constructed of Morris plywood, each having wooden two-bladed rotors made to an American aerofoil section design by Morris Furniture of Glasgow. The rotors, powered by an air-cooled 50 hp Weir engine turning at 430 rpm, had cyclic and collective pitch control. The W.5 made its first public flight on June 7, 1938, with pilot Raymond A. Pullin, son of C.G. Pullin, at Dalrymple, Ayrshire in Scotland. Each rotor had a 4.57 m (15 ft) diameter. The W.5 gross weight was 381 kg (840 lbs); it had a maximum rate of climb of 122 m/min (400 ft/m) and maximum speed of 122 km/h (75.7 mph). By the beginning of WWII, the helicopter had flown 80 hours and is considered to have been the world’s second fully practicable helicopter.
The Weir W.6 two-seater helicopter, like its smaller Weir W.5 single-seat predecessor, was a twin-boom outrigger construction but of a more sophisticated design. It was constructed at Thornliebank, Glasgow in the Weir factory. Powered by a fan-cooled de Havilland Gipsy Queen 205 hp motor in a tractor configuration (in the nose of the aircraft), each wooden 3-bladed rotor (with a metal leading edge) turned at 275 rpm with cyclic and collective control enclosed within the rotor hub (with a rachet-type freewheeling device to allow for autorotation). The initial flight took place at Dalrymple, Ayrshire in Scotland in October 1939 with Raymond Pullin at the controls, but the German invasion of Poland on September 1st and the United Kingdom’s entry into WWII caused all work to cease by the middle of 1940. Each rotor had a diameter of 7.62 m (25 ft) and the maximum gross weight was 1070 kg (2,359 lb). Disc area totaled 45.60 sq. m (490.9 sq. ft) with a disc loading of 11.73 kg/sq. m (2.403 lb/sq. ft.). Its cruising speed was 128 km/h (79.5 mph) with a rate of climb of 198 m/min (650 ft/min) to an absolute ceiling of 3810 m (12,500 ft). It flew with two passengers, Air Vice Marshall Arthur William Tedder (later 1st Baron Tedder, GCB) and Ken Watson, thus becoming the first helicopter to carry a passenger. The Weir W.6 last flew in June 1940. Its engine was later used in the 1944 Cierva W.9 (assigned serial number PX203), the first flight of which was delayed until 1945 due to damage incurred during ground-running and which was destroyed in an accident in 1946.
References:
- Pullin, C. G. “Helicopter Research and Development,” The Journal of the Helicopter Association of Great Britain – Bulletin, March 1947, pp. 21 – 80
- Pullin, R. A. “A Rotary-Wing Enterprise,” Aeronautics, November 1946
- Leishman, J. Gordon, Principles of Helicopter Aerodynamicsz (Second Edition), Cambridge University Press, 2006.
Text by Bruce H. Charnov
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