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Sikorsky CH-37 Mojave

Heavy-Lift Cargo / Transport Helicopter (1956)

Introduced in the mid-1950s, the Sikorsky CH-37 Mojave was used by American forces for a time during the Vietnam War.

Authored By: Staff Writer | Last Edited: 06/08/2018 | Content ©www.MilitaryFactory.com | The following text is exclusive to this site.

The Sikorsky CH-37 Mojave was an early-generation, heavy-lift cargo helicopter in service with the American military and served from 1956 into the late 1960s. First flight was during 1953 as the Korean War (1950-1953) wound down and 154 examples were ultimately built by Sikorsky Aircraft. Due to its universally-acknowledged ugly appearance, the Mojave was also known by the nicknames of "Duce", "Cross-Eye", and "Cross-Eyed Monster".

Experience of World War 2 showed the need to move masses of combat-ready infantry and cargo to forward operating positions and this was done during the conflict by aircraft, half-tracks, and trucks. It was not until helicopter technology finally allowed forces to move man and machine over all manner of terrain and drop them into otherwise restricted areas. The concept pushed the idea of rotary-wing heavy-haulers for the various branches of military services around the world leading Sikorsky Aircraft - once known for its contributions to fixed wing aircraft - to become a helicopter powerhouse before the end. The Mojave became one of its many products in that industry.

The company developed its Model H-37 into the S-56 and sold the USMC on the large utility freighter in 1951. The helicopter featured a rather unappealing shape, with its bulbous nose section, but its capability to haul up to 26 infantry, 24 medical litters, or cargo (including light utility vehicles) in their place within a long, deep hold provided the needed utility functionality in a helicopter package. The hold was accessed via clamshell-style doors found under the cockpit floor and room was maximized by having the engines fitted into nacelles along the sides of the fuselage. The four-bladed main rotor mast was seated over the mass of the fuselage with a drive shaft extending through the tail section to a four-bladed tail rotor fitted to portside..The tail unit also consisted of a vertical fin capped by a horizontal stabilizer. The undercarriage was partially retractable, the main legs pulling into the underside of the engine nacelles though the tail wheel remained fixed in flight. A standard operating crew numbered three to include two pilots and a loadmaster. Dimensions included an overall length of 64 feet, 3 inches, a height of 22 feet, and a rotor diameter of 72 feet. Unloaded weight reached 20,830lbs with a Maximum Take-Off Weight nearing 31,000lbs.

Power to the Mojave line was served through 2 x Pratt & Whitney R-2800-54 "Double Wasp" radial piston engines developing 2,100 horsepower each. Maximum speeds reached 130 miles per hour while cruising speeds were typically in the 115 mile per hour range. Operational reach was out to 145 miles with a listed service ceiling of 8,700 feet. Rate-of-climb was a useful 910 feet per minute.

The prototype form became the "XHR2S-1" of which four were completed for USMC evaluation. They were powered by 2 x R-2800-54 series engines of 1,900 horsepower each and, upon completing the requisite trials, the prototypes were taken into USMC service under the designation of "HR2S-1". These differed from the prototype forms by redesigned engine nacelles and main landing gear legs sporting twin wheels for additional support. The vertical tail fin was modified some as well. USMC procurement ended at 55 examples.

A sole HR2S-1 was then modified for U.S. Army trials as the "YH-37" and ultimately accepted under the finalized "H-37" designation. These helicopters were procured in 94 examples with initial batch models designated as "H-37A". Army versions differed some from the USMC mounts at the main rotor hub and at the vertical tail fin. With new cargo doors, reinforced fuel stores, and an automatic stabilization system introduced, ninety of these original A-models were upgraded to the "H-37B" standard.

The United States Navy took on the helicopter in only two examples for the Airborne Early Warning (AEW) role and designated them as "HR2S-1W".

Following the 1962 reworking of American military aircraft designations, the Army's H-37A became the "CH-37A", the H-37B became the "CH-37B", and the USMC's HR2S-1 became the "CH-37C".

The HR2S-1 saw first deliveries in mid-1956 to both the USMC and Army and it was during this time that the United States military saw itself committed to actions centered around the Vietnam War (1955-1975). The Mojave was shuttled to the theater in limited numbers and were used primarily in the equipment recovery role. Crews were sent to pick up downed aircraft in enemy territory with regularity while other missions ranged from artillery relocation to fuel and personnel deliveries. The CH-37 was used alongside another heavy-hauler - the awkward-looking CH-54 "Flying Crane" - which succeeded CH-37s in the war. The USMC elected the CH-53 "Sea Stallion" as the official replacement for its Mojaves. Sea Stallions were introduced in 1966.

By the end of the decade, the Mojaves were all but out of frontline service. They also did not see export for they proved a limited design - large, heavy, and expensive to obtain and operate in any useful numbers. Additionally, the machine relied on a piston-driven engine arrangement at a time when the shift to more powerful turboshaft engine designs was obvious.

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