S-53 (U.S.Navy (XHJS-1)
. During the period 1945 to mid-1951 Sikorsky received only one experimental contract from the combined military services; the U.S .Navy experimental order for three XHJS-1 (S-53) helicopters, a four-place light utility and rescue aircraft. The Navy sponsored XHJS-1 (1946) was in competition with Piasecki’s XHJP-1. . Sikorsky’s initial entry into this emerging utility market was anything but a success. In fact it was a total failure. That failure was especially serious because it was caused by the company’s basic helicopter configuration as it existed in that era. The company found that it could not produce a successful large helicopter simply by scaling up the configuration that proved to be so successful for small helicopters. The configuration on which the S-53 was based relates to the location of the engine in a compartment directly below the main rotor. This engine location simplified the transmission gearing however it forced the cabin, and therefore the helicopter's payload, to be located forward of the rotor rotational axis. As the payload changes, as with the addition of personnel or cargo, the helicopter's center of gravity moved away from the rotor's rotational axis which in turn adversely affected the helicopter's pitch attitude and flying qualities. This engine location is clearly seen in the inboard profile drawing shown below. Sikorsky recognized this problem after losing the very first competition that it entered for a utility size helicopter. This competition, begun in 1945, was for a US Navy search and rescue helicopter whose required payload and range far exceeded the capabilities of Sikorsky’s existing models.
Sikorsky entered this competition with a new design that it called the S-53 which the Navy identified as the XHJS-1, shown in photo collage below. The S-53 was a relatively large helicopter at the time with a gross weight of 5500 pounds and powered by a Continental R-975-34 engine rated at 525 HP. But the basic problem of the S-53 was that it was patterned after earlier configurations and its larger size simply magnified the shortcomings inherent in those earlier models. The final competitors for this new Navy mission were Sikorsky and Piasecki, who proposed a tandem rotor design. Both companies were awarded contracts to build prototypes for the Navy’s competitive fly-off evaluation. Three of the XHJS-1 models were built by Sikorsky and three XHJP-1 models were built by Piasecki. Both models were designed to the same mission requirement and used the same engine. That was the first direct competition between Sikorsky Aircraft and the predecessor company of Boeing Vertol for a new utility helicopter.
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.INBOARD PROFILE - SINGLE ENGINE HELICOPTER - drawn by Nicholas Glad . Related Models: None . . Prepared by Dan Libertino, December 2011. Summary of Technical Sources:
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