The Westland WS-61 Sea King is a British licence-built version of the American Sikorsky S-61 helicopter of the same name, built by Westland Helicopters. The aircraft differs considerably from the American version, with Rolls-Royce Gnome engines (derived from the US General Electric T58), British-made anti-submarine warfare systems and a fully computerised flight control system. The Sea King was primarily designed for performing anti-submarine warfare (ASW) missions. A Sea King variant known as the Commando was developed by Westland to serve as a troop transport.
In British service, the Westland Sea King provided a wide range of services in both the Royal Navy and the Royal Air Force. As well as wartime roles in the Falklands War, the Gulf War, the Bosnian War, the Iraq War and the Afghanistan War, it was used as a Royal Navy Search and Rescue (red and grey livery) and RAF Search and Rescue Force (yellow livery) helicopter. The Sea King was also adapted to meet the Royal Navy's requirement for a ship-based airborne early warning platform.
On 26 September 2018, the last remaining Sea King variant in Royal Navy service was retired. Many operators have replaced, or are planning to replace, the Sea King with new helicopters, such as the NHIndustries NH90, SH-60 Seahawk, and the AgustaWestland AW101. Germany retired the type in March 2024; however, it is still in widespread service around the globe, including India and several Middle Eastern countries.
Design and development
Origins Westland Helicopters, which had a long-standing licence agreement with Sikorsky Aircraft to allow it to build Sikorsky's helicopters, extended the agreement to cover the Sikorsky SH-3 Sea King soon after the Sea King's first flight in 1959.James 1991, pp. 377–378.Uttley 2001, p. 206. Westland proceeded to independently develop the Sea King, integrating a significant proportion of components from British suppliers; key changes include the use of a pair of Rolls-Royce Gnome turboshaft engines and the implementation of an automatic flight control system.McGowen 2005, p. 119. On this matter, authors Jim Thorn and Gerald Frawley stated that: "Despite appearances, Westland's Sea King [is a] very different aircraft from Sikorsky's".Thorn and Frawley 1998, p. 164. Many of the differences between the Westland-built Sea King and the original helicopter were as a result of differing operational doctrine. While the U.S. Navy Sea Kings were intended to be under tactical control of the carrier from which they operated, the Royal Navy intended its helicopters to be much more autonomous, capable of operating alone, or co-ordinating with other aircraft or surface vessels. This resulted in a different crew arrangement, with operations being controlled by an observer rather than the pilot, as well as fitting a search radar.Lake 1996, pp. 114–115.
The Royal Navy selected the Sea King to meet a requirement for an anti-submarine warfare (ASW) helicopter to replace the Westland Wessex, placing an order with Westland for 60 SH-3D Sea Kings in June 1966.Air International May 1981, p. 215. The prototype and three pre-production aircraft were built by Sikorsky at Stratford, Connecticut and shipped to the United Kingdom to act as trials and pattern aircraft.Howard et al. 2011, pp. 229–230. The first of the SH-3Ds was initially fitted with General Electric T58s and, after being shipped from the United States, was flown in October 1966 from the dockside at Avonmouth to Yeovil airfield. The other three were delivered from the docks, by road to Yeovil, for completion with British systems and Rolls-Royce Gnome engines. The first Westland-built helicopter, designated Sea King HAS1, flew on 7 May 1969 at Yeovil. The first two helicopters were used for trials and evaluation by Westland and the Aeroplane and Armament Experimental Establishment; subsequent production Sea Kings were delivered to the Royal Navy's 700 Naval Air Squadron from August 1969 onwards.
By 1979, the Royal Navy had ordered 56 HAS1s and 21 HAS2s to meet the anti-submarine requirements, these were also configured for the secondary anti-ship role.Hewish 1979, p. 76. The Westland Sea King was updated and adapted for numerous roles, subsequent variants include the HAS2, HAS5 and HAS6. Changes from initial production aircraft included an expansion of the cabin and upgraded engines.McGowen 2005, pp. 119–120.
Commando and further developments
One of the most extensively modified variants was the Westland Commando, operated by the Royal Navy as the HC4.McGowen 2005, p. 120.Air Forces, May 2012, p.6, Key Publishing, The Commando had capacity for up to 28 fully equipped troops and had originally been developed to meet an Egyptian Air Force requirement.McGowen 2005, pp. 120, 126. Due to the deletion of the amphibious capability, not required in the Egyptian desert, the most noticeable change from the Sea King was the deletion of the side floats, the main undercarriage being carried on stub sponsons. An improved variant of the Egyptian Commando, with changes including the fitting of folding blades common to the ASW variants, was designated as the Sea King HC4 by the Royal Navy and all the aircraft were new build. First flying on 26 September 1979, due to its operational range of up to 600 nautical miles without refuelling, the HC4 'Commando' became an important asset for amphibious warfare and troop transport duties, in particular."Westland – Sea King/Commando." Flight International, 3 August 1985, p. 42. Several Royal Naval Air Squadrons have operated the Commando variant, such as 845 Naval Air Squadron, 846 Naval Air Squadron and 848 Naval Air Squadron. In British service, the Sea King HC4 was deployed on operations in the Falklands, the Balkans, both Gulf Wars, Sierra Leone, Lebanon and Afghanistan. Towards the end of the Sea King's operational life, several HAS6s were repurposed by the removal of the ASW equipment, as troop transports. In 2010, the last of the UK's converted ASW Sea Kings to troop transports were retired.Allen, Peter. "UK RN retires final Commando Sea King Mk 6CR." Jane's Defence Weekly, Volume 47, Issue 2, 2 June 2010, p. 33.
In the 1970s, Westland's experience with the Sea King led the company to conduct the British Experimental Rotor Program (BERP), in coordination with the Royal Aircraft Establishment, which applied innovations in composite materials and new design principles to the helicopter rotor. Initial trials carried out with active Sea Kings found several advantages to the BERP rotor, including a longer fatigue life and improved aerodynamic characteristics. Subsequent Westland helicopters, such as the record-breaking Lynx and the AgustaWestland AW101 Merlin, took advantage of BERP rotors for greater performance.Bud and Gummett 2002, pp. 75–79. Westland equipped later-built Sea Kings with the new composite rotors as well."Westland – Sea King." Flight International, 1 August 1987, p. 34. Retrieved 19 April 2012.
Westland has produced a total of 330 Sea Kings;McGowen 2005, p. 126. export customers include the Indian Naval Air Arm, the German Navy, the Royal Australian Navy, and the Royal Norwegian Air Force. The last of the Royal Navy's Sea Kings in the ASW role was retired in 2003, being replaced by the AgustaWestland Merlin HM1. The Sea King Airborne Surveillance and Control (ASaC) variant is expected to be replaced around the introduction of the two aircraft carriers.Beedall, Richard. "Maritime Airborne Surveillance and Control (MASC) (UK MoD)." Navy Matters, 18 May 2011. Retrieved 19 April 2012. The UK has also planned to retire the HC4 and search and rescue variants in March 2016.
Search and rescue
A dedicated search and rescue (SAR) version, the HAR3, was developed for the RAF Search and Rescue Force. The type entered service in 1978 to replace the Westland Whirlwind HAR.10.Ministry of Defence 2006, p. 120. A 16th helicopter was ordered shortly after, and following the Falklands War of 1982, three more were purchased to enable operation of a SAR flight in the islands, initially from Navy Point on the north side of Stanley harbour, and later from RAF Mount Pleasant. In 1992, six further helicopters were ordered to replace the last remaining Westland Wessex helicopters in the SAR role, entering service in 1996. However, teething problems resulted in the actual operational use of the HAR3A's being delayed until mid 1997. The six Sea King HAR3As featured updated systems, including a digital navigation system and more modern avionics.Chesneau 1985, pp. 2–3.
Westland also manufactured SAR versions of the Sea King for the Royal Norwegian Air Force, the German Navy and the Belgian Air Force.Chesneau 1985, p. 2. On SAR variants, the cabin was enlarged by a stretch of the fuselage behind the door; another key feature, used for additional flotation in the unusual event of a water landing, inflatable buoyancy bags were housed inside the aircraft's sponsons.Chesneau 1985, pp. 2–4. Upgrades and changes made to SAR Sea Kings include the addition of radar warning receivers, a cargo hook for the underslung carriage of goods, and the redesigning of the cockpit for compatibility with night vision goggles.Chesneau 1985, p. 5.
, up to 12 HAR3/3As were dispersed across the UK, a further two HAR3s were attached to the Falkland Islands, providing 24-hour rescue coverage. Some Royal Navy HAS5 ASW variants were adapted for the SAR role and served with 771 Naval Air Squadron, Culdrose and HMS Gannet SAR Flight at Prestwick Airport in Scotland. They were expected to remain in service until 2016, being replaced with civilian operated SAR rotorcraft.Carrara 2009, pp. 78–82. Both Andrew Mountbatten-Windsor (formerly Prince Andrew) and William, Prince of Wales have flown SAR Sea Kings in front-line roles.Harding, Thomas. "Harry gets his wish to see action in Iraq." The Daily Telegraph, 23 February 2007. Retrieved 19 April 2012.
Airborne early warning
The Royal Navy's airborne early warning (AEW) capability had been lost when the Fairey Gannet aeroplane was withdrawn after the last of the RN's fleet carriers was decommissioned in 1978. During the Falklands War, a number of warships were lost and casualties suffered due to the lack of an AEW platform.Armistead and Armistead 2002, p. 131. The proposed fleet cover by the RAF Shackleton AEW.2 was too unresponsive and at too great a distance to be practical. Consequently, two Sea King HAS2s were modified in 1982 with the addition of the Thorn-EMI ARI 5980/3 Searchwater LAST radar attached to the fuselage on a swivel arm and protected by an inflatable dome. This allowed the radar to be lowered below the fuselage during flight and for it to be raised for landing. These prototypes, designated HAS2(AEW), were both flying within 11 weeks and deployed with 824 "D" Flight on HMS Illustrious, serving in the Falklands after the cessation of hostilities.Instant Airborne Radar Heads South. "New Scientist", 12 August 1982, 95(1318), p. 428. A further eight HAS2s were modified to a production standard, known as the AEW2. Two remained "fitted for but not with". These entered operational service in 1985, being deployed by 849 Naval Air Squadron. Three Sea King HAS5/6s were later converted as part of the ASaC Mk7 programme, bringing the Mk7 fleet to 13; still 3 below the requirement.