Mach2 GP011 Sikorsky S.51The Sikorsky R 5 (other designations: Sikorsky H 5, S 48 or S 51) was an American multipurpose helicopter from World War II and the post war period. The flight of the prototype took place in 1943, and the machine was put into the line in 1945. In total, it is estimated that over 300 helicopters of this type were built. The drive was provided by a single Pratt and Whitney Wasp Junior engine with 450 HP. The hull length of this machine was 17. 4 meters,