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Aviation History
1953
1953 - 0105.PDF
FLIGHT, 23 January 1953 103 BRITISH PORTFOLIO WESTLAND AIRCRAFT, LTD., of Yeovil, Somerset, hold the licence for the manufacture in Britain of the Sikorsky helicopters. Perhaps more than any other man, Igor Sikorsky has been responsible for making the helicopter a practical and reliable proposition, and in consequence Westlands were able to secure an early lead in the production of rotating wing aircraft in this country. Two entirely different models, designated S-51 and S-55, are in production at the present time. The S-51 has accommodation for a pilot, seated centrally in the nose, and three passengers behind. Large numbers are already in operation, and have been used for a multitude of different purposes, including crop-spraying, air-sea rescue, casualty evacuation, traffic - control, city-centre trials, experimental air-mail work and a period of scheduled London-Birmingham services. Night-flying equip ment can be provided and the still-air range is approximately 250 miles. The airframe comprises three main assemblies—cabin, centre- section and tail cone (as Westlands style the "boom"). The centre-section, which houses the engine and fuel tanks and supports the rotor-head structure and the undercarriage, is of welded-steel tube construction, whereas the remainder is a light- alloy monocoque. The undercarriage is of sufficient height to permit loading operations to be carried out whilst the rotor is in motion, though precautions must be taken to avoid the tail-rotor. An Alvis Leonides is mounted horizontally immediately behind the passenger compartment, and transmits power to the main rotor via a centrifugal clutch, free-wheel and gearbox, and to the tail- Westland-Sikorsky S-55 Westland-Sikorsky S-51 rotor by shafting lying along the top of the tail cone. The main rotor blades are of all-metal construction : they can be folded for storage, and are now servo-controlled—a modification which has reduced pilot-fatigue to a low level. The S-55 is a considerably larger and more ambitious machine which none the less operates on only slightly more power. Provision is made for two pilots on the upper deck, with full dual control, whilst the cabin, below and behind, has space for ten occupants or their equivalent. As with all helicopters, the applications of the S-55 are numerous; it has already flown over 250,000 hours on such duties as ambulance and air-sea rescue work in Korea. On the civil side, the type already holds the world's first certificate of airworthiness for a cargo-and-passenger-carrying helicopter, and the location of the cabin at the centre of gravity permits rapid changing of contents without seriously affecting balance. Still-air range is over 400 miles, and many optional items of equipment can be fitted, including a power-operated pilot-controlled winch, or amphibious undercarriage, thus further extending the scope of utilization. Power is at present supplied by a Pratt and Whitney Wasp R-1340 radial of 600 h.p., but it is intended eventually to install the new 800 h.p. 14-cylinder Alvis Leonides Major. The engine is mounted at an angle in the nose, behind large non-structural doors which facilitate servicing. A shaft-drive transmits power via a clutch, free-wheel and gearbox to the main all-metal rotor which —as in the S-51—is servo-operated and can be folded. In the roomy cockpit the pilot sits on the right in order to make use of his left hand for radio and other controls without removing the right hand from the azimuth stick. The hydraulic servo control svstem operates on both the azimuth and collective pitch control, and the pilot's comfort is further improved by the adjust able rudder pedals. Aerofoil surfaces, which can be controlled by the pilot, are located at the rear end of the tail cone to maintain an optimum attitude for trim. landing lights are positioned on the underside of the aircraft at the rear of the cabin, and each is controlled independently by the pilot or co-pilot for use either in landing or for search and rescue operations. Typical arrangements of the S-55 provide for ten troop seats, six stretchers or six passengers, luggage and freight.
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