In 1959 Westland acquired the license to build the Sikorsky S-61B, to replace the Wessex in the antisubmarine role. The Royal Navy specification called for a British powerplant with different characteristics from the original one, different electronics and a wide range of mission capabilities. Westland adopted a pair of Rolls-Royce Bristol Gnome turbines for their version of the Sea King, with fully computerized controls and largely British-made ASW equipment. The resultant helicopter is readily identifiable by the dorsal radome of the all-weather search radar. Other avionics systems include Plessey dipping sonar, Marconi Doppler navigation radar and Sperry & New-mark instrumentation. With the two Gnome turbines and these avionics, the first HAS Mk.1 production Sea King flew on 7 May 1969 and the first Royal Naval Squadron was formed the following August.

The Sea King is an antisubmarine helicopter with genuine all-weather capability and a fully-proven navigational and attack system. But it is not a truly amphibious vehicle, in that any length of time spent in water would irrevocably damage some items of equipment on the hull. It is therefore only designed to land on water in an emergency, the boat-type hull being guaranteed watertight for 15 minutes. The two lateral sponsons contain flotation bags to improve buoyancy. Standard ASW equipment includes two marker buoys, four smoke floats, four Mk.44 homing torpedoes or four depth charges. The Sea King can also carry out missions against surface vessels with one or two antiship missiles.

The following versions of the Sea King have been produced: Sea King HAS Mk.1, Mk.2 and Mk.5 for the Royal Navy; HAR Mk.3 (16 of the SAR version for the RAF); Sea King Mk.42 (24 for the Indian Navy), which was based on the RN version except for the communications equipment; Mk.41 for the German Navy (22); Mk.43 for the Norwegian Navy (11); Mk.45 for the Pakistani Navy (6); Mk.48 for the Belgian Air Force (5 of the SAR version); Mk.50 for the Australian Navy (12). A commando version has also been produced, of which 17 were initially delivered to the Royal Navy and at least another 30 to Egypt and Qatar.

G.Apostolo "The Illustrated Encyclopedia of Helicopters", 1984

A licence agreement finalised with Sikorsky in 1959 allowed Westland to use the airframe and rotor system of the Sikorsky SH-3 Sea King as the basis for a new ASW helicopter for the Royal Navy. Following test and evaluation of prototype and pre-production aircraft assembled from Sikorsky-built components, the first production Westland Sea King HAS.Mk 1 for the navy was flown on 7 May 1969, the type entering service the same year. At that time, the Sea King HAS.Mk 1 was similar to the Sikorsky Sea King, but powerplant comprised two Rolls-Royce Gnome H.1400 turboshaft engines. More significantly, Westland had adapted the large cabin as a tactical compartment for ASW operations, this meaning that the British Sea King was able to operate as an independent unit in an ASW role. Subsequent development has changed this helicopter very considerably.

Westland also built a tactical version known as the Commando, which is suitable for such roles as cargo transport, casualty evacuation, logistic support and troop transport (28 men can be carried). Further variants are detailed in the table below. Deliveries for the Sea King and Commando totalled 326 by the end of 1993.

VARIANTS

Sea King HAS.Mk 1: initial ASW version for Royal Navy; since updated to Sea King HAS.Mk 2 by Royal Navy; 56 completed

Sea King HAS.Mk 2: ASW/SAR version for Royal Navy with uprated Gnome H.1400-1 turboshafts; 21 completed

Sea King HAR.Mk 3: SAR version for Royal Air Force with Gnome H.1400-1 turboshafts; 16 delivered in 1979 plus three in 1985; upgraded to

HAR.Mk 3A standard through addition of greatly improved avionics, navigation and communications gear

Sea King HC.Mk 4: version of Commando Mk 2 for Royal Navy; combines folding rotor and tail of Sea King, non-retractable landing gear of Commando and Gnome H.1400-1 turboshafts; last aircraft delivered in 1990, total production 89; some aircraft modified with RWR, missile approach warning system, chaff/flare dispensers, tactical navigation equipment, and NVG cockpit for Gulf War operations

Sea King Mk 4X: two aircraft, basically as HC.Mk 4; for development use by RAE Famborough

Sea King HAS.Mk 5: developed ASW/SAR version for Royal Navy with Gnome H. 1400-1 engines and advanced avionics; all Sea King HAS.Mk 2 aircraft upgraded to this standard along with 30 new-build aircraft delivered between 1980 and 1986

Sea King HAS.Mk 6: substantially improved anti-submarine warfare version for Royal Navy comprising five conversions from Mk 5 standard and 25 new aircraft

Sea King Mk 41: SAR version for Federal German navy with H.1400 turboshafts

Sea King Mk 42: ASW version for Indian navy with H.1400 turboshafts

Sea King Mk 42A: ASW version for Indian navy with H.1400-1 turboshafts

Sea King Mk 42B: anti-ship version for Indian navy, H 1400-1 turboshafts and equipped to carry Sea Eagle missiles

Sea King Mk 43: SAR version for Norwegian air force with H.1400 turboshafts

Sea King Mk 43A: SAR version for Norwegian air force with H. 1400-1 turboshafts

Sea King Mk 45: ASW version for Pakistan navy with H.1400 turboshafts

Sea King Mk 47: ASW version with H.1400-1 turboshafts, ordered by Saudi Arabia for Egyptian navy

Sea King Mk 48: SAR version for Belgian air force with H.1400-1 turboshafts

Sea King Mk 50: multi-role version for Royal Australian Navy; developed from Sea King HAS.Mk 1 but with H. 1400-1 turboshafts; two additional but similar aircraft ordered in 1983 were allocated designation Sea King Mk 50A

Commando Mk 1: version with H.1400 turboshafts ordered by Saudi Arabia for Egyptian air force

Commando Mk 2: version with H. 1400-1 turboshafts for Egyptian air force

Commando Mk 2A: version as Commando Mk 2 for Qatar Emiri air force

Commando Mk 2B: version as Commando Mk 2 with VIP interiors for Egyptian air force

Commando Mk 2C: version as Commando Mk 2B for Qatar Emiri air force

D.Donald "The Complete Encyclopedia of World Aircraft", 1997

	Advanced Sea King Mk 42B. The Indian Navy launching a BAe Sea Eagle long-range missile.
	RAF Sea King HAR.3 of No.202 Squadron.
	Westland Sea King HAS Mk 5/6 are operated in the ASW role by the Royal Navy.
	Westland Commando Sea King HC4 operated by 845 NAS in the UN role.

В 1959 году компания Westland получила право использовать планер и систему винтов вертолета Sikorsky SH-3 "Sea King" как основу для нового вертолета ВМС. 7 мая 1969 года состоялся первый полет серийного вертолета Westland "Sea King" HAS.Mk.1, построенного для ВМС Великобритании. Компания Westland устроила в кабине вертолета тактический отсек с оснащением для противолодочных операций, и "Sea King" мог самостоятельно вести боевые действия против подводных лодок.

Тактический вариант под названием "Commando" можно использовать в качестве грузового, для эвакуации раненых, вертолета снабжения и, наконец, военно-транспортного, способного перевозить 28 человек. К концу 1993г. заказчики получили 326 вертолетов вариантов "Sea King" и "Commando".

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- Westland had to fight off stiff competition from the Sikorsky Sea King to gain Royal Navy orders.

- Rolls-Royce based its Gnome turboshaft on the T58 of the Sikorsky helicopter.

- Only the airframe shape and rotorhead of the Sikorsky Sea King remained unchanged.

- British ASW and assault Sea Kings served during the Gulf War.

- The Commando Mk 1 is also known as the Sea King Mk 70 and is basically a stripped-out Sea King HAS.Mk 1.

- No customer has ever specified the Mk 2's optional underwing hardpoints. Westland flew the first commando Mk 2 on 16 January 1975.

- An idea to fit the Commando Mk 2 with 26 inflatable cabin seats was abandoned at an early stage.

- Commando Mk 2Bs have extra seats for two flight attendants.

- Qatar's Mk 3s have Sea King-like undercarriage sponsons.