Westland Wessex HU5

The Westland Wessex is an early turbine-powered helicopter produced by the British rotorcraft specialist Westland Aircraft (later Westland Helicopters). It was an under licence development of the piston-engined Sikorsky S-58. During the mid-1950s, Westland arranged with the American helicopter manufacturer Sikorsky Aircraft to demonstrate one of its S-58s in Britain to garner sales. Having secured an order from the Royal Navy (RN), Westland implemented several modifications to the S-58 design ahead of quantity production in the UK. One major change from Sikorsky's S-58 was the replacement of the piston-engine powerplant with a turboshaft engine; while early models were powered by a single Napier Gazelle engine, later builds used a pair of de Havilland Gnome engines. The use of a turboshaft engine was credited with increasing payload capacity while reducing both vibration and noise levels. The Wessex was first introduced by the RN in 1961; it was the service's first purpose-build anti-submarine helicopter. Multiple variants of the type were introduced, including more capable anti-submarine models (enabling early Wessex HAS.1s to be reassigned to search and rescue (SAR) duties) and a dedicated battlefield transportation variant, the Wessex HU.5; the latter was equipped with two Gnome engines that provided double the power of the HAS.1's single powerplant. The Royal Air Force (RAF) also opted to procure the Wessex, using it for troop-transport, air ambulance and ground support missions; it was the first RAF helicopter that was suitable for instrument flight and thus night-time operations. Several sales also made to overseas customers; several overseas military services flew the Wessex, including the Royal Australian Navy, the Brunei Air Wing, and the Sultan of Oman's Air Force amongst others. Furthermore, a limited number of civilian rotorcraft were also produced. In British services, the Wessex had an operational service life in excess of 40 years, the last examples in Britain being withdrawn during 2003.