The Sea King has its origins in efforts by theUnited States Navy to counter the growing threat ofSoviet submarines during the 1950s. Accordingly, the helicopter was specifically developed to deliver a capable ASW platform; in particular, it combined the roles ofhunter andkiller, which had previously been carried out by two separate helicopters. The Sea King was initially designatedHSS-2, which was intended to imply a level of commonality to the earlierHSS-1; it was subsequently redesignated as theSH-3A during the early 1960s.
Introduced to service in 1961, it was operated by the United States Navy as a key ASW and utility asset for several decades prior to being replaced by the non-amphibiousSikorsky SH-60 Seahawk in the 1990s. In late 1961 and early 1962, a modified U.S. Navy HSS-2 Sea King was used to break theFAI 3 km, 100 km, 500 km, and 1000 km helicopter speed records. The Sea King also performed various other roles and missions such as search-and-rescue, transport, anti-shipping,medevac,plane guard, andairborne early warning operations.
The Sea King has also proved to be popular on the export market with foreign military customers, and has also been sold to civil operators as well. As of 2024, many examples of the type remain in service in nations around the world, although some major users have begun to retire the type. The Sea King has been built under license byAgusta in Italy,Mitsubishi in Japan, Canada byUnited Aircraft of Canada, and byWestland in the United Kingdom as theWestland Sea King. The major civil versions are theS-61L and S-61N. The S-61R was another important variant, which was the CH-3C/E Sea King, used by the U.S. Coast Guard as the HH-3F Pelican, and the Air Force's HH-3E Jolly Green Giant; this version had a ramp at the rear among other changes.
During theCold War, theSoviet Navy built up a large and varied fleet of submarines which at one point was in excess of 200 operational submarines. The US Navy countered this threat by the improvement and development of variousanti-submarine warfare (ASW) capabilities, which resulted in the development of the Sea King.[2] During the late 1950s, the US Navy took advantage of recent aerospace advances, such as theturboshaft engine, by commissioning the development of a new large naval helicopter. Sikorsky received a request from the service to design a new turbine-powered helicopter that would be capable of performing the ASW mission. The specification included a dippingsonar, mission endurance of four hours, and the ability to support a weapons load of 380 kg (840 lb).[3]
XHSS-2 Sea King prototype
In 1957, Sikorsky was awarded a contract to produce an all-weatheramphibious helicopter for the US Navy. As per the earlier specification, this new rotorcraft was to excel at ASW; specifically, it would combine the roles of hunter and killer, as these two duties had previously been carried out by two separate helicopters.[3][4] It was also the first helicopter to be procured under the US Navy's new weapon system concept, under which Sikorsky was responsible not only for the design and production of the airframe, but all major onboard systems, such as thesonar, navigational equipment, electronic devices, and support equipment. As such, the navigation suite for the rotorcraft was developed jointly by Sikorsky and the US Navy.[5]
Key features of the emerging ASW helicopter included itsamphibioushull, which enabled the rotorcraft to readily perform water landings, and its adoption of a twin-turboshaft engine arrangement that enabled it to be larger, heavier and better-equipped than had been possible with prior helicopters.[4][5][6] The designationHSS-2 was applied, allegedly to imply a level of commonality to the earlierHSS-1, should political sentiment turn against the development of an entirely new rotorcraft.[3] A total of ten prototypes were produced to support the development program.[7]
On 11 March 1959, the first prototype conducted itsmaiden flight.[4] During early 1961, a pair of prototypes were stationed on board theaircraft carrierLake Champlain to fulfill a demand for carrier suitability trials. These trials, which involved testing the folding mechanism of the mainrotor blades and a series of takeoffs performed during winds of up to 50 mph (80 km/h), were completed successfully in mid-1961.[7][8] Shortly after the completion of suitability trials, the US Navy formally accepted delivery of the first HSS-2 rotorcraft, which was subsequently re-designated as the SH-3A, in September 1961.[9]
In late 1961 and early 1962, a modified US Navy HSS-2 Sea King was used to break the FAI 3 km, 100 km, 500 km and 1000 km helicopter speed records. This series of flights culminated on 5 February 1962 with the HSS-2 setting an absolute helicopter speed record of 210.6 mph (338.9 km/h).[10][11] This record was broken by a modified FrenchSud-AviationSuper Frelon helicopter on 23 July 1963 with a speed of 217.77 mph (350.47 km/h).[12]
The base design of the Sea King had proved sound and several aspects were judged to be potentially useful for other operators, thus Sikorsky elected to pursue the further development of the rotorcraft for other markets beyond the US Navy.[7] One of the major variants of the Sea King to be produced was a model for civil operators, which was designated as theSikorsky S-61L. The first operator of the S-61L wasLos Angeles Airways, who introduced the type to service on 11 March 1962.[13][14] Another noteworthy Sea King variant, the significant change this time being the adoption of a conventional fuselage, theSikorsky S-61R, was also concurrently developed for transport andsearch and rescue (SAR) duties, this type being extensively operated by theU.S. Air Force and theU.S. Coast Guard.[15]
In US Navy service, the initial SH-3A model of the Sea King would be progressively converted into the improved SH-3D and SH-3H variants; these featured more powerful engines and improved sensors that gave the type greater operational capabilities as an ASW platform. It was also common for Sea Kings to be converted for non-ASW activities, these roles included minesweeping, combat search and rescue, and as a cargo/passenger utility transport.[4] The aircrew on ASW-tasked Sea Kings were routinely trained to carry out these secondary roles as aircraft could often be quickly adapted to perform different missions in the face of operational needs.[16]
The NH-3A prototype, which tested outfitting a Sea King with fixed wings and jet engines
The NH-3A (S-61F) was an experimental high-speedcompound helicopter based on the Sea King tested in the 1960s.[17] Later modified with a tail rotor able to rotate 90° to serve as a pusher propeller; this helicopter demonstrated "Roto-Prop" pusher propeller for Sikorsky'sS-66 design.[18]
A minesweeper version of the Sea King for the U.S. Navy was made, with nine converted from SH-3A aircraft and then called the RH-3A.[19]
In addition to those Sea Kings that were manufactured by Sikorsky, severallicense agreements were enacted with other firms to produce the type. These included the Japanese conglomerateMitsubishi and the Italian aerospace companyAgusta. Another licensee was the British helicopter manufacturerWestland Helicopters, which substantially redesigned the Sea King to produce various models of their own, collectively referred to as theWestland Sea King.[20][21][22] In contrast to the US Navy's Sea Kings, the Westland Sea King was intended for greater operational autonomy.[23] In total, Westland produced 330 Sea Kings; outside of its British-based operators, various export customers were found for the Westland Sea King. including theIndian Naval Air Arm, theGerman Navy, theRoyal Australian Navy, and theRoyal Norwegian Air Force.[24]
While Sikorsky opted to terminate its own Sea King production line during the 1970s, the type has had a lengthy service life. In September 2009, it was reported that nearly 600 Sea Kings were believed to still be operational.[25]
The Sea King was produced in the USA, and under license in the U.K. by Westland, Italy by Augusta, Canada by United Aircraft of Canada, and in Japan by Mitsubishi.[26] Total production was about 1100 to 1300.[citation needed] The S-61 family includes the S-61L and S-61N, which are commercial models. The S-61R, which is the CH-3C/E Sea King, HH-3E Jolly Green Giant, and HH-3F Pelican. The S-61 license built by Westland had different engines and is usually called the Westland Sea King. Canadian Sea Kings were called CH-124 and license made by United Aircraft of Canada. They were made in Italy by Agusta and called AS-61 and ASH-3. In Japan, the Mitsubishi version was called the HSS-2.[26]
The Sikorsky SH-3 Sea King is a twin-engine medium-sized amphibious rotorcraft. Many of the features on board the Sea King represented a considerable advancement over preceding helicopters. In addition to being fully amphibious and capable of operating under all weather conditions, it is the first operational American helicopter to be able to simultaneously hunt and destroy submarines.[5] Its twin-turboshaft powerplant layout gave the SH-3 a higher payload and greater reliability than previous anti-submarine helicopters.[4] In the event of a single engine failing, the Sea King could continue flying on a single engine.[27] The powerplant used on the Sea King was theGeneral Electric T58-GE-8B, which was initially capable of generating up to 1,250 shp (930 kW) each.[5]
In normal operations, the Sea King typically would have a four-man crew on board; these being a pilot and copilot in the cockpit, and two aircrew stationed within the main cabin area. When conducting anti-submarine missions, the rear aircrew operated the aircraft's sensors and interpreted the generated data.[28] For search-and-rescue missions, the Sea King's cabin could accommodate up to 22 survivors. In a medical layout, a maximum of nine stretchers plus two medical officers could be carried. In the troop transport role, up to 28 soldiers can be accommodated.[29]
The Sea King features many design elements to support naval-orientated operations. The main rotor blades and the tail section can be folded via fully automated systems for storage on board ships.[5] The adoption of anamphibioushull allowed a Sea King to conduct a water landing and, being completely watertight, would enable the rotorcraft to remaining floating for prolonged periods on the ocean's surface. Deployable airbags in the aircraft'ssponsons added to the rotorcraft's stability and buoyancy, resisting pitching and rolling.[6] The hull design was compatible with landing on challenging terrain, including ice, snow, swamp land, and tundra.[5] Wheels are installed in the sponsons for land operations.[5]
The armament fitted upon a Sea King could vary considerably. For anti-submarine missions, the aircraft could carry up to four torpedoes or four depth charges. For anti-ship duties, some models were outfitted to carry one or two missiles, typicallySea Eagles orExocets.[30] The Sea King could also be fitted to deploy theB57 nuclear bomb.[31] ASW equipment used on Sea Kings has included theAQS-13A/B/E dippingsonar which included specialized computers for processing sonar and sonobuoy data, various models ofsonobuoys, ARR-75 Sonobuoy Receivers, and the ASQ-81magnetic anomaly detector. The commonly fitted AKT-22data link enabled the rapid dissemination of sonar information to other friendly elements.[32] Some later Sea King models featured the TACNAV digital navigation system (first generation GPS) and overhauled cockpit instrumentation fornight vision compatibility.[33]
Helicopter Anti-Submarine Squadron HS-12 "Wyverns" flying SH-3H Sea Kings in formation, 1985Several UH-3H Sea Kings taking flight to fight theCedar Fire inSan Diego, California, in 2003
During June 1961, the Sea King became operational with the US Navy as theHSS-2; at the time, it was not only the largest amphibious helicopter in the world, but was also the first all-weather rotorcraft to reach production status for the US Navy.[5] When the unified aircraft designation system was introduced, the rotorcraft's designation was changed to SH-3A. It was used primarily foranti-submarine warfare: the largely involved the detection and tracking of Soviet submarines. In the event of open warfare breaking out between the two powers, Sea Kings would have been used to attack these submarines with the intent to sink them.[34]
The Sea King was able to operate from the flight decks of many of the US Navy's vessels as well as shore bases. It could also operate from offshore platforms to extend their surveillance and strike ranges. The type was capable of conducting nighttime ASW operations, albeit these usually posed considerable difficulty for the flight crew.[35][36]
The Sea King also performed various other roles and missions such as search-and-rescue, transport, anti-shipping andairborne early warning operations.Aircraft carriers would typically deploy Sea Kings to operate near the carrier as aplane guard, ready to rescue air crew who crashed during takeoff or landing.[37] They were routinely used in a logistical capacity at sea, transferring personnel, mail, and other lighter cargoes between vessels.[35]
TheRoyal Canadian Navy (RCN) became a major operator of theSikorsky CH-124 Sea King following its introduction to service in 1963. It remained Canada's dominant maritime helicopter for over 50 years, finally being withdrawn in 2018.[38] One notable innovation in Canadian operations, which was subsequently adopted by several other nations, was the use of a winch 'hauldown' landing and securing method, referred to as a 'Beartrap'. This device considerably increased the ability of Sea Kings to land in difficult conditions, such as on small flight decks or during poor weather conditions.[38][39]
The Sea King was exported in large numbers to various nations, such asBrazil,Italy,Japan and theUnited Kingdom.[40] Several operators have kept their Sea Kings in use for more than 50 years.[41][42]
During theVietnam War, SH-3s rescued the crews of downed aircraft at sea and over land, typically being equipped withself-sealing fuel tanks, multiple machine guns and heavy armor when performing such missions.[43] Due to the type's greater range and the safety of having two engines, it was often used during rescue sorties intoNorth Vietnam to retrieve downed aircrew.[7] The Sea King was also used for medical evacuations and disaster relief efforts.[35]
U.S. Marine Corps VH-3 Sea King, operating asMarine One, landing on the south lawn of theWhite House
Several Sea Kings, operated by theUnited States Marine Corps'sHMX-1 unit, are used as the official helicopters of thePresident of the United States; in this capacity, the call sign 'Marine One' is used by the helicopter currently occupied by the President. As of 2012, a replacement helicopter fleet for the Sea King was pending under theVXX program.[47][48] In 1992, the USJustice Department sued Sikorsky over allegations of overcharged component pricing and deliberately misleading US Navy negotiators.[49] In 1997, the Justice Department issued further accusations against Sikorsky of willful overcharging on a contract to upgrade the Navy's Sea Kings.[50] In 2024, the VH-3D was replaced by theVH-92 Patriot as the Marine One helicopter.[51]
During the 1990s, the Sea King was replaced in the ASW and SAR roles by the U.S. Navy with the newerSikorsky SH-60 Sea Hawk.[52] However, the SH-3 continued to operate in reserve units in roles including logistical support, search and rescue, and transport. On 27 January 2006, the SH-3 was ceremonially retired atNAS Norfolk, Virginia, by Helicopter Combat Support Squadron 2 (HC-2).[53] They have been replaced by increasingly advanced variants of the SH-60 Sea Hawk.[35] In the early 21st century, following their drawdown in US service, there have been a number of initiatives to refurbish ex-military Sea Kings for continued operations; in addition to civil operators, nations such as Egypt and India acquired refurbished former US Sea Kings to supplement their own aging fleets.[54][55][56]
A SH-3G Sea King helps recoverApollo 17.Ticonderoga is in the backgroundHH-3A onBon Homme RichardArmy One, a VH-3A "Sea King" that served in the Presidential fleet from 1961 to 1976, on permanent display at theNixon LibrarySH-3G in 1981
Combat search and rescue helicopter for the U.S. Navy. 12 converted from SH-3A.[4]
CH-3A
Military transport version for the U.S. Air Force; three converted from SH-3As into CH-3A configuration; they later became CH-3Bs.[58]
NH-3A (S-61F)
Experimental high-speedcompound helicopter, with extensive streamlining, no floats, short wings carrying two turbojet engines for extra speed; one converted from SH-3A.[citation needed] Later modified with a tail rotor able to rotate 90° to serve as a pusher propeller; this helicopter demonstrated "Roto-Prop" pusher propeller for Sikorsky'sS-66 design.[59]
RH-3A
Minesweeper helicopter for the U.S. Navy. Nine converted from SH-3A aircraft.[19]
VH-3A
VIP transport (Better known asMarine One orArmy One 1957–76) helicopter for the U.S. Army and Marine Corps; originally designated HSS-2Z. Eight built, plus two SH-3A conversions rebuilt from damaged helicopters (one YHSS-2 and one SH-3A).[citation needed] The rest were returned to the U.S. Navy in 1975–76 and replaced by the VH-3D.
CH-3B
Military transport helicopter for the U.S. Air Force.[57]
VIP Presidential transport helicopter (better known asMarine One) for the U.S. Marine Corps, 11 built. It entered service in 1976.[60]
SH-3G
Cargo, utility transport helicopter for the U.S. Navy. 105 conversions from SH-3A and SH-3D.[4]
SH-3H
Upgrade of the SH-3G as ananti-submarine warfare (ASW) helicopter for the U.S. Navy.[4] It included SH-3G features with improvements for ASW,anti-ship missile detection and other airframe improvements. 163 SH-3A/D/Gs were upgraded to SH-3H configuration.[60]
SH-3H AEW
Airborne early warning version for the Spanish navy.
UH-3H
Cargo, utility transport version for the U.S. Navy; converted from SH-3H by removing ASW systems.[60]
Export version for theRoyal Danish Air Force. Wider pontoons without flotation bags, a 530-liter center tank instead of a dipping sonar and no automatic powered folding system.[61]
S-61A-4 Nuri
Military transport, search and rescue helicopter for theRoyal Malaysian Air Force. It can seat up to 31 combat troops. 38 built.[57]
S-61A/AH
Utility helicopter for survey work and search and rescue in the Antarctic.
S-61B
Export version of the SH-3 anti-submarine warfare helicopter for the Japanese Maritime Self Defense Force.
The Sea King Improvement Program (SKIP) added modernized avionics as well as improved safety features.[63]
CH-124B
Alternate version of the CH-124A without a dipping sonar but formerly with a MAD sensor and additional storage for deployable stores. In 2006, the five aircraft of this variant were converted to support the Standing Contingency Task Force (SCTF), and were modified with additional troop seats, and frequency agile radios. Plans to add fast-rope capability, EAPSNIPS (Engine Air Particle Separator / Snow & Ice Particle Separator) did not come to fruition.[63]
CH-124B2
Six CH-124Bs were upgraded to the CH-124B2 standard in 1991–1992. The revised CH-124B2 retained the sonobuoy processing gear to passively detect submarines but was also fitted with a towed-array sonar to supplement the ship's sonar. Since anti-submarine warfare is no longer a major priority within the Canadian Forces, the CH-124B2 were refitted again to become improvised troop carriers for the newly formed Standing Contingency Task Force.[63]
CH-124C
One CH-124 operated by the Helicopter Operational Test and Evaluation Facility located atCFB Shearwater. Used for testing new gear, and when not testing new gear, it is deployable to any Canadian Forces ship requiring a helicopter.[63]
CH-124U
Unofficial designation for four CH-124s that were modified for passenger/freight transport. One crashed in 1973, and the survivors were later refitted to become CH-124A's.[63]
Westland Sea King AEW.2A of theRoyal Navy in 1998German Navy Sea King in 1980, made by Westland
TheWestland Sea King variant wasmanufactured under license byWestland Helicopters Ltd in theUnited Kingdom, who developed a specially modified version for theRoyal Navy. It is powered by a pair ofRolls-Royce Gnome turbines (license-built T58s), and has British avionics and ASW equipment. This variant first flew in 1969, and entered service the next year. It was until 2017 also used by theRoyal Air Force in asearch and rescue capacity, and has been sold to many countries around the world.
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SH-3 at NAS Oceana Airshow, 2004
