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The Westland Wessex is a British-built turbine-powered development of the Sikorsky H-34, it was developed and produced under license by Westland Aircraft (later Westland Helicopters). One of the main changes from Sikorsky's H-34 was the replacement of the piston-engine powerplant with a turboshaft engine; the Wessex was the first helicopter in the world to be produced in large numbers that made use of a gas turbine propulsion system.〔("The Wessex Helicopter". ) ''royalnavy.mod.uk'', Retrieved: 14 January 2014.〕 Early models were powered by a single Napier Gazelle engine, later builds used a pair of Rolls-Royce Gnome engines. The Wessex was initially produced for the Royal Navy (RN) and later for the Royal Air Force (RAF); a limited number of civilian aircraft were also produced, as well as some export sales. The Wessex operated as an anti-submarine warfare and utility helicopter; it is perhaps best recognised for its use as a search and rescue (SAR) helicopter. The type entered operational service in 1961, and had a service life in excess of 40 years before being retired in Britain. ==Design and development== In 1956, an American-built S-58 was shipped to Britain for Westland to use as a pattern aircraft. Initially assembled with its Wright Cyclone, it was demonstrated to the British armed services leading to a preliminary order for the Royal Navy.〔("Wessex" ) ''Flight'' 1957 p837〕 For British production, it was re-engined with a single Napier Gazelle turboshaft engine, first flying in that configuration on 17 May 1957.〔Taylor 1965, p.169.〕 The lighter (by 600 lb) Gazelle engine meant some redistribution of weight. The first Westland-built Wessex serial ''XL727'', designated a ''Wessex HAS.1'', first flew on 20 June 1958.〔 The first production Wessex HAS1 were delivered to Royal Navy's Fleet Air Arm (FAA) in early 1960; the Wessex was the first helicopter operated by the FAA to be purpose-designed from scratch as an anti-submarine platform.〔 In service, the Wessex was found to be a major improvement over the older Westland Whirlwind. The revolutionary turbine propulsion, in addition to giving the Wessex a larger load capacity, was quieter and generated less vibration, the latter quality was highly beneficial when treating casualties during flight; the Gazelle engine allowed for rapid starting and thus faster response times.〔 The Wessex could also operate in a wide range of weather conditions as well as at night, partly due to its use of an automatic pilot system. These same qualities that made the Wessex well-suited to the anti-submarine role also lent themselves to the search and rescue (SAR) mission, which the type would become heavily used for.〔 An improved variant, the Wessex HAS3, succeeded the HAS1 in the anti-submarine role; it featured a more capable radar and better avionics, greater engine power, improved navigational features and a more advanced weapon system; the original HAS1 were hence re-tasked for SAR duties.〔 A 'commando assault' variant, the Wessex HU5, was also developed as a battlefield transportation helicopter; it was typically deployed upon on the navy's amphibious assault ships, such as the commando carrier HMS ''Albion'', and heavily used to transport the Royal Marines.〔McGowen 2005, p. 84.〕 The Wessex HU5 was powered by twin Rolls-Royce Gnome engines, which provided nearly double the power of the original HAS1 model and hugely expanded the aircraft's range and allowed for operations in a wider range of conditions; during the 1970s, the HU5 also started to be used for the SAR mission.〔 As an anti-submarine helicopter, the Wessex could be alternatively equipped with a dipping sonar array to detect and track underwater targets or armed with either depth charges or torpedos; a single Wessex could not be equipped to simultaneously detect and attack submarines as this was beyond its carrying capacity. It was this limitation that soon led the Royal Navy to search for a more-capable helicopter that could provide this capability; which would ultimately result in Westland proceeding with the adaptation and production of another Sikorsky-designed helicopter in the form of the Westland Sea King.〔Plamondon 2010, p. 74.〕〔McGowen 2005, pp. 84-85.〕 The Wessex was also successfully employed as a general-purpose helicopter for the RAF, capable of performing troop-carrying, air ambulance and ground support roles. The Wessex was the first of the RAF's helicopters in which instrument flying, and thus night time operations, were realistically viable.〔Royal Air Force Historical Society 2000, p. 83.〕 Unlike the Navy's Wessex fleet, which was largely composed of early single-engine models, the RAF mandated that its Wessex helicopters should be all twin-engined; this was a major factor in the RAF's decision to reject the adoption of ex-FAA Wessex helicopters as the navy migrated to the newer Sea King.〔Royal Air Force Historical Society 2000, pp. 95-96.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Westland Wessex」の詳細全文を読む スポンサード リンク
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