HJD / HJH Whirlaway
The Whirlaway was a Navy experimental helicopter with laterally displaced rotors. The HJD Whirlaway was started in 1946 by Douglas Aircraft, and redesignated the HJH in 1947 following the acquisition by McDonnell. In 1944, U.S. Navy launched a competition that called for a large rescue helicopter which could carry up to 10 occupants. McDonnell was determined to win a new Navy contract as the company only had sub-contract jobs at the war time. With investment in Platt LePage Aircraft Co., McDonnell was allowed to learn helicopter techniques and developed its own design, Model 65. As early as the summer of 1944, the Navy had awarded a contract to the McDonnell Aircraft Corporation, St . Louis, Missouri, for the world's first twin-engine helicopter to operate in the 10,000-pound gross weight class and to provide "greater insight into the problems of helicopter design." Variations of rotor diameter, roto-engine gear ratio, and control sensitivity were possible in the large helicopter.
In 1945, McDonnell proposed the project to Navy and was rewarded contract for construction of one test bed, designated XHJD-1. The Navy-designated XHJD-1, which first flew in August 1944, cruised over 100 miles per hour and carried a useful load of more than 3,000 pounds. Considering a most suitable configuration for a large helicopter, it was fitted with twin side-by-side rotors mounted at the end of main wings. The two 46-foot rotors which turned in opposite directions were arranged side-by-side and were powered by two 450-horsepower engines.
It became the world's first successful twin-engines, twin rotors helicopter. From 1946 to 1951, XHJD-1 was tested for numerous flying researches peculiar to its twin-rotor configuration. Upon completion of its trails program, the XHJD-1 was then retired and was donated to the National Air and Space Museum. Though promising, the Whirlaway marked the end of the line for helicopters with two main rotors mounted on pylons.
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