This article is about the helicopter. For the fixed-wing aircraft, see Westland IV
The Westland Wessex was 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 large mass-produced helicopter designed around use of a gas turbine engine. Early models were powered by a single Napier Gazelle engine, while later builds used a pair of de Havilland 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. For British production, it was re-engined with a single Napier Gazelle turboshaft engine, first flying in that configuration on 17 May 1957. 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 being 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.
A pair of Royal Navy Wessex helicopters in the flight deck of the HMS Intrepid
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. The Wessex HU5 was powered by coupled de Havilland Gnome engines, which provided nearly double the power of the original HAS1 model and hugely expanded the aircraft's range. This 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 torpedoes; 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.
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. 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.
In April 1961, the Royal Australian Navy (RAN) announced that they had selected the Westland Wessex to become the standard service helicopter from their ships and its intention to purchase roughly 30 for anti-submarine patrols, casualty evacuations, and fleet communications duties. The RAN formally accepted the first two of 27 Wessex helicopters in September 1963; 817 Squadron was the first to operate the type; the Wessex and its dunking sonar array quickly proved to be the most effective anti-submarine platform as yet seen in the RAN.
The Wessex was a major operational shift for the Fleet Air Arm, enabling the RAN to proceed with the conversion of the aircraft carrier HMAS Melbourne as an anti-submarine platform. In typical carrier operations, a Wessex would be deployed during the launch and recovery of fixed-wing aircraft as a guard helicopter; during anti-submarine patrols, routine procedure was to have one Wessex airborne to actively screen the ship while a second would be fully armed and prepared for operations, such an arrangement was used during troop transport deployments to Vietnam during the 1960s. Performing Search and Rescue sorties became another valued role of the type; in 1974, multiple Wessex helicopters participated in the relief effort in Darwin in the aftermath of Cyclone Tracy.
While the Wessex proved to be too large to reasonably operate from most of the RAN's destroyers, it was found to be well suited as a troop-transport helicopter from heavy landing ships and larger vessels. By 1980, the Wessex was no longer being used for anti-submarine operations, having been replaced by the more advanced and capable Westland Sea King in this capacity. Instead, remaining Wessex helicopters were retained to perform its secondary roles as a plane guard, search and rescue platform, and as a utility transport helicopter.