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 was adapted by Westland as troop transport known as the Commando.

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 Balkans conflict, the Iraq War, and the Afghanistan War, the Sea King is perhaps most well known in its capacity 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.

As of 2013, the WS-61 Sea King remains in operation in Britain, as well as multiple export customers: Germany, Norway, Egypt and India. Some operators have replaced, or are planning to replace, the Sea King with more modern helicopters, such as the NHIndustries NH90 and the AgustaWestland AW101 Merlin.


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. 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. 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”.

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 coordinating 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.

The British 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. 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. 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. 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.

Commando and further developments

One of the most extensively modified variants was the Westland Commando , operated by the Royal Navy. The Commando had capacity for up to 28 fully equipped troops and had originally been developed to meet an Egyptian Air Force requirement. A 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. First flying on 26 September 1979, due to its operational range of up to 600 nautical miles without refuelling, the Commando became an important asset for amphibious warfare and troop transport duties, in particular. 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.

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. Westland equipped later-built Sea Kings with the new composite rotors as well.

Westland has produced a total of 330 Sea Kings; 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 Queen Elizabeth-class aircraft carriers. The UK has also planned to retire the HC4 and search and rescue variants in the 2010s.

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. A 16th helicopter was ordered shortly after, and following the Falklands War of 1982, three more examples 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.  The six Sea King HAR3As featured updated systems, including a digital navigation system and more modern avionics.

Westland also manufactured SAR versions of the Sea King for the Royal Norwegian Air Force, the German Navy and the Belgian Air Force. 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. 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.

As of 2006, 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. As of 2009, they are expected to remain in service until 2018. Both Prince Andrew, Duke of York and Prince William, Duke of Cambridge have flown SAR Sea Kings in front-line roles.

  • Role: Medium lift/ Transport utility