US Navy Helicopters -- A History
by
Peter Dancey
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US Navy Helicopters -- A History
Copyright © 2010 by Peter Dancey
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US Navy Helicopters -- A History
US NAVY HELICOPTERS
Although more than 400 Sikorsky R-4 helicopters and its variants were used by American and British forces during and after WW II mainly for utility and rescue work, it was not until the Korean War (1950-1953) that the flexibility of the helicopter was appreciated and its real military career started. The US Navy's first helicopter squadron was formed in 1946 and the first helicopters to see action in Korea were Bell HTLs (Bell 47) attached to US Marine Corps Observation Squadron VMO-6. Based at Camp Pendleton, California, the squadron was originally equipped with Stinson OY-2 Sentinel light observation airplanes. In July 1950 it received 4 Sikorsky HO3S-1 the US Marine Corps designation for the Sikorsky S-51 that was also licence-produced in Britain by Westland as the Dragonfly. VMO-6 arrived in Pusan South Korea on 2 August 1950, and within hours was making history as the world's first military helicopter to undertake heli-borne C3 (Command, Control and Communications) pressed into service by Brig-General Edward Graig, USMC to fly low over the forward battle area with the North giving the commander previously unheard of communications and control of his front-line troops. 2 days later on the 4 August another VMO-6 HO3S-1 performed one of the earliest helicopter operations in Korea when it evacuated a number of casualties from a battle raging around the town of Chindongni. Rather surprisingly it was the USMC rather than the US Army that pioneered the use of the helicopter as a means of transport and reinforcement. On 13 September 1951 in a series of 28 flights over 14hrs a Company of Sikorsky HRS-1 (S-55) transport helicopters each capable of lifting 10 men, air-lifted a battalion of Marines and their supplies on to an otherwise inaccessible series of ridges in the rugged mountains of Central Korea at the same time evacuating 75 wounded men.
At first naval helicopters were used for the usual duties of air/sea rescue ambulance and casevac work, communications, transport and photography, but both American and British aircraft carriers operated with helicopters on board in the Korean War flying in commando and Marine Corps troops. Ironically it was the Navy that made the first use of a helicopter in Korea as an offensive weapon unofficially when Lt Thornton and Petty Officer Whitaker 'bombed' enemy positions with fragmentation grenades and home-made nail bombs in December 1950. The following year while their formal missions remained those of SAR and reconnaissance, Thornton and Whitaker continued to use their Sikorsky HO3S-1 as an impromptu gun-ship at times bringing retaliation from the Chinese and North Korea MiG-15 jet fighters. Luckily, most of the attacks were unsuccessful due to the inability of the much faster jets to accurately aim their guns and rockets at the constantly manoeuvring helicopters.
The military helicopter came of age in Korea as a means of transport as a reconnaissance aircraft but above all for evacuation and in particular casualty evacuation (casevac). Transport and troop-carrying operations were first carried out regularly by US Marine Corps Squadron HMR-161 operating twin-rotor Piasecki HRP-1s. Though it was not long before the Navy realised the potential of the helicopter in other directions and one of the most successful and important roles since the 1950's has been in the anti-submarine warfare role (ASW).
On 3 October 1951 the US Navy formed its first helicopter ASW squadron at Key West, Florida. HS-1 'Sea Horses' was equipped with Piasecki HUP-1 incorporating personnel from its trials unit VX-1. The unit had been formed following years of trials and development work during and after WW II with Sikorsky R4 on anti-submarine warfare duties, not to attack them, but to 'scare' them to below attack depth for the naval escorts to deal with. Tactics used by the slow-flying Britsh Royal Navy Fairey Swordfish biplane torpedo-bombers in WW II. By the end of the war, the USN was testing dipping sonar (SOund Navigation And Ranging) from helicopters initially using a XHOS-1 of trials squadron VX-1 and in 1946 in a military version of the Sikorsky S-51 designated HO2S-1. The problems of using these rather fragile early machines in the ASW role were brought to the fore with the loss of this machine later in the hot- and-humid conditions at Key West, Florida. Nevertheless, as the Soviet submarine threat continued to cause concern it was not long before the trials work was given new impetus with a AN/AQS-4 sonar installed in a Piasecki XHRP-1 'Flying Banana'. Although this helicopter was not well-suited for ASW it proved a better platform than the somewhat under-powered Sikorsky H-19 (S-55) and as such the Navy selected Piasecki's twin- rotor HUP-2S 'Retriever' as its future ASW airplane. But, in September 1952 following a series of engine failures it was modified and relegated to plane-guard and utility work to which it was better suited. With 4 squadrons formed for ASW work in desperation the USN transferred 24 former US Marine Corps HRS-1 (S-55) to equip HS-1 and HS-3 on the East coast and HS-2 and HS-4 on the West Coast. Fitted with higher- powered engines the re-designated HRS-3 (CH-19E) were received by HS-1 at Key West in March 1953 the type now able to competently undertake the basic task of detecting submarines with its AQS-4 sonar but unable to carry any weaponry the attack mission remained the premise of the surface fleet.
The Navy's requirement for a twin-rotor ASW helicopter remained and Bell proposed its HSL-1 powered by a single P&W R-2800 engine. Having won the contract it first flew in March 1953, and after having undergone extensive trials during which it displayed much promise, when evaluated aboard the escort carrier USS Kula Gulf in 1955 it was found to be too awkward to handle aboard ship too noisy in the cabin for the sonar operator and too big for an escort carriers flight-deck (with rotor-blades folded it was more than 49ft long). Fortunately the single-rotor Sikorsky HSS-1 (S-58) 'Sea Bat', which was being developed in parallel as insurance should the HSL-1 fail to live up to early expectations demonstrated during subsequent testing, that it was more than capable of fulfilling the Navy's ASW role. It would still need to trade weapons (two Mk 43 torpedoes) and range against hover time and fuel load. With the HSL-1 order cut back to just 50 airplanes, it was redeployed for operation in the mine-countermeasures role to which it was well-suited and the Navy decided to accept the Sikorsky design and deliveries of the HSS-1 began in August 1955 to HS-3 for ASW duties with two system operators in the main cabin. The improved HSS-1N (SH-34J) was fitted with a Doppler radar to measure ground-speed and drift, a radar-altimeter and an auto-pilot, and was delivered to HS-5 and HS-6 in 1958 and with the advanced AQS-5 sonar and a longer dunking cable (450ft as compared to 90ft) as a result submarine hunting from an automatic-hover of 50ft proved to be a much easier operation than previously experienced by the ASW helicopter crews. The cabin size of the Sikorsky S-58 made it an ideal helicopter for trooping and SAR work and major orders were placed by the Marine Corps for the HUS-1 (UH-34D) variant.
Advances in aero-engine design produced the small but powerful General Electric T 58-GE-6 turbo-shaft engine (essentially a jet engine for helicopters) to power the Sikorsky HSS-2 'Sea King' the prototype of which first flew in March 1959. Equipped with torpedoes, depth-bombs and the latest AQS-10 sonar with a 360º sweep in 1min instead of the 6mins of earlier equipment combined with automatic-hover to increase detection capability initial deliveries of the SH-3A (re-designated in October 1962) with the improved 1,250shp T58-GE-8 engine to HS-3 at NAS Norfolk and HS-10 at San Diego were made in September 1961. Already at the end of the 1960's in line with budgetary constraints the specialised but out-dated ASW carriers were being withdrawn, with the result the new ASW helicopters were integrated aboard the 'Super Carriers' USS Forrestal, Saratoga, Ranger, and Independence. HS-11 and HS-2 embarked Forrestal and Independence respectively in 1969-71 and unit integration with fixed-wing airplane operations was deemed a great success resulting in other HS units incorporated into C-V Air Groups with the Sikorsky SH-3 Sea King becoming the main-stay of carrier-based ASW operations. A total of 245 SH-3As were eventually built for the USN along with further VH-3A VIP variants ordered in 1961 for the joint US Marine/Army Executive Flight Detachment in Washington Continued development of the SH-3 led in 1966 to the 'improved' SH-3D with a 1,400shp T58-GE-10 engine with an uprated gearbox and avionics fit.