|Sikorsky CH-37 Mojave|
|CH-37 Mojave attempting to lift a crashed Piasecki H-21.|
|Primary users||United States Army|
United States Marine Corps
The Sikorsky S-56, called the H-37 Mojave by the United States Army and HR2S by the United States Marine Corps(CH-37 under the 1962 United States Tri-Service aircraft designation system), was a large heavy-lift helicopter by the standards of the 1950s. It came into being as an assault transport for the USMC, with a capacity of 26 fully-equipped troops; the order was placed in 1951, the first prototype flew in 1953, and production deliveries began in July 1956 to Marine Corps Squadron HMX-1, sixty aircraft in total being produced.
The United States Army evaluated the prototype in 1954 and ordered 94 examples as the CH-37A, the first being delivered also in summer 1956. All Marine and Army examples were delivered by mid-1960. Army examples were all upgraded to CH-37B status in the early 1960s, being given Lear auto-stabilization equipment and the ability to load and unload while hovering. In the 1962 unification of United States military aircraft designations, USMC examples became CH-37C.
At the time of delivery, the CH-37 was the largest helicopter in the Western world, and it was Sikorsky's first twin-engined helicopter. Two Pratt & Whitney Double Wasps were mounted in outboard pods that also contained the retractable landing gear. This left the fuselage free for cargo, which could be loaded and unloaded through large clamshell doors in the nose. The single main rotor was five-bladed, and designed to function with one blade shot away in combat.
The CH-37 was one of the last heavy helicopters to use piston engines, which were larger, heavier and less powerful than the turboshafts subsequently employed. This accounted for the type's fairly short service life, all being withdrawn from service by the late 1960s, replaced in Army service by the CH-54 Tarhe.
Four CH-37Bs were deployed to Vietnam in 1963 to assist in the recovery of downed United States aircraft. They were very successful at this role, recovering over $7.5 million dollars' worth of equipment, some of which was recovered from behind enemy lines. In 1965 the Ch-37's from Marine Heavy Helicopter Squadron 462 (HMH-462)were sent to Vietnam aboard he USS Princeton, landed at Chu Lai and were subsequently attached to MAG 16 at Marble Mountain outside DaNang. At this time they became the Ch-37 Detachment.
Westland Aircraft, a manufacturer of license-built Sikorsky designs used the S-56 physics and the rotor and gearbox as the basis for their Westland Westminster. The Westminster had a tubular frame and used the Napier Eland turboshaft for power. It would have been clad for the passenger role (50 troops) or been left open-framed as a cargo aircraft (4 jeeps or equivalent). The Westminster project was terminated in favour of the Rotodyne design that had been acquired from Fairey Aviation.
- XHR2S-1 - Prototype.
- HR2S-1 - Assault transport helicopter for the US Marine Corps. Later redesignated CH-37C.
- HR2S-1W - Two helicopters converted into airborne early warning aircraft for the US Navy.
- YH-37 - One HR2S-1 helicopter evaluated by the US Army.
- H-37A Mojave - Military transport version for the US Army.
- H-37B Mojave - Upgraded transport version for the US Army. Later redesignated CH-37B.
Specifications (CH-37 Mojave)
- Crew: 3
- Capacity: 26 troops
- Length: 88 ft 0 in (26.8 m)
- Rotor diameter: 72 ft 1 in (22.0 m)
- Height: 22 ft in (m)
- Disc area: 4,080 ft² (379 m²)
- Empty weight: lb (kg)
- Max takeoff weight: 21,000 lb (9,500 kg)
- Powerplant: 2× Pratt & Whitney R-2800-54 "Double Wasp" radial engines, 2,100 hp (1,600 kW) each
- Maximum speed: 131 mph (114 knots, 211 km/h)
- Range: 247 mi (215 nm, 400 km)
- Service ceiling: 8,000 ft (m)
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