- US Army CH-37 with day-glo orange markings, circa 1950s . | Photo: US Army

Flightline: 131 - Sikorsky CH-37 Mojave

The Mojave was a transport helicopter used by the US Navy, Marine Corps and Army from the early 1950s through the late Sixties.

Ordered by the USMC in 1951 under the designation HR2S, the Sikorsky Mojave helo was the largest helicopter in the Western world at the time, and was the last large helicopter powered by piston engines. The Marines wanted a helicopter capable of carrying 3 M422 Mighty Mites or 26 fully equipped troops, and Sikorsky responded with the S-56, which housed two Pratt & Whitney R-2800 Double Wasps in pods (which also contained the retractable main landing gear), which left the fuselage free to carry the maximum amount of cargo. The nose featured clamshell doors, which allowed rapid loading and unloading of men and cargo. Considerations were made for ship-board service, as the main rotor and tail could be folded.

A retired CH-37B on display at Pima Air & Space Museum. Note the folded rotor blades. | Photo: aeroprints.com

A retired CH-37B on display at Pima Air & Space Museum. Note the folded rotor blades. | Photo: aeroprints.com

Marines debarking from a Sikorsky HR2S-1 helicopter. | Photo: USN/USMC

Marines debarking from a Sikorsky HR2S-1 helicopter. | Photo: USN/USMC

U.S. Marines offload a M101 105 mm howitzer from a Sikorsky HR2S-1 . | Photo: USN/USMC

U.S. Marines offload a M101 105 mm howitzer from a Sikorsky HR2S-1 . | Photo: USN/USMC

Fifty-five production HR2S-1 were produced for the Marines, along with two HR2S-1W AEW choppers, equipped with AN/APS-20E search radar, for the Navy. Vibration in the airframe disrupted the radar enough that the Navy later abandoned the program.

Composite image of the HR2S-1W. | Photo: US Navy

Composite image of the HR2S-1W. | Photo: US Navy

Orthograph of the AEW variant of the Mojave. | Illustration: G.Apostolo "The Illustrated Encyclopedia of Helicopters"

Orthograph of the AEW variant of the Mojave. | Illustration: G.Apostolo "The Illustrated Encyclopedia of Helicopters"

In 1954, one HR2S was evaluated by the Army as a YH-37, with 94 more H-37As beginning in 1956. In the early 1960s, the Army Mojaves were upgraded as H-37B, adding a Lear auto-stabilization system which allowed the helo to be loaded and unloaded while in a hover, as well as a redesigned nose door and crashproof fuel cells. With the 1962 Tri Service designation arrangement, the US Army choppers were redesignated CH-47A and B, while the USMC variant was now called the CH-37C.

In addition to transporting men and cargo, the Mojave was also used to retrieve film capsules returning from reconnaissance satellites and to cart around space capsules for the Mercury program.

A U.S. Marine Corps Sikorsky HR2S-1 helicopter lifting a Mercury program space capsule. | Photo: USN

A U.S. Marine Corps Sikorsky HR2S-1 helicopter lifting a Mercury program space capsule. | Photo: USN

Four US Army CH-37Bs were deployed to Vietnam in September 1965 to assist in the recovery of downed U.S. aircraft, operating from Marble Mountain Air Facility until May 1967. Over US$7.5 million worth of equipment was recovered by the quartet, some from behind enemy lines. Some Marine CH-37Cs were also pressed into service as retrieval aircraft

A CH-37C removes a battle damaged UH-34, 1966 . | Photo: USMC

A CH-37C removes a battle damaged UH-34, 1966 . | Photo: USMC

US Army CH-37 Helicopter with downed Piasecki H-21 . | Photo: US Army

US Army CH-37 Helicopter with downed Piasecki H-21 . | Photo: US Army

Despite serving admirably, the CH-47s piston engines were underpowered, and the choppers were eclipsed by more modern turbine-powered heavy lift helos like the CH-53 and CH-47, and they were retired from service by the late 1960s. Six B and C model Mojaves are on display around the country.

A Marine Corps CH-47C. missing its rotor blades. on display at the National Naval Aviation Museum . | Photo: Tomás Del Coro

A Marine Corps CH-47C. missing its rotor blades. on display at the National Naval Aviation Museum . | Photo: Tomás Del Coro

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