Sikorsky CH-37 Mojave

CH-37 Mojave
CH-37 Mojave attempting to lift a crashed Piasecki H-21.
Role	Cargo helicopter
Manufacturer	Sikorsky Aircraft
First flight	1953
Introduction	July 1956
Retired	Late 1960s
Primary users	United States Army United States Marine Corps
Number built	154
Developed into	Sikorsky S-60 Westland Westminster

The Sikorsky CH-37 Mojave (company designation S-56) was a large heavy-lift helicopter of the 1950s.

The S-56 came into being as an assault transport for the United States Marine Corps (USMC), with a capacity of 26 fully equipped troops. An order for the aircraft was placed in 1951 utilizing the U.S. Navy/U.S. Marine Corps designation of the time of HR2S. The first prototype, the XHR2S-1 flew in 1953 and production deliveries of the HR2S-1 began in July 1956 to Marine Helicopter Squadron ONE (HMX-1), with a total of sixty aircraft 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 Corps 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, the USMC examples were redesignated from HR2S-1 to 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 R-2800 Double Wasp radial engines 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 early models could carry a payload of either three M422 Mighty Mite (a lightweight jeep-like vehicle) or 26 troops. For storage, the main rotor blades folded back on the fuselage and the tail rotor mast folded forward on the fuselage.

The CH-37 was one of the last heavy helicopters to use piston engines, which were larger, heavier and less powerful than the turboshaft engines subsequently employed in later military helicopters. This accounted for the type's fairly short service life, all being withdrawn from service by the late 1960s, replaced in Army service by the distantly related CH-54 Tarhe and in the Marine Corps by the CH-53 Sea Stallion.

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