Sikorsky CH-37 MojaveSikorsky CH 37 Mojave helicopter model. The S 56 came into being as an assault transport for the United States Marine Corps (USMC), with a capacity of 26 fully equipped marines. An order for the aircraft was placed in 1951 using 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