Mr. Hisao Hagiwara of Tokyo formed the Jiyu Koku Kenkyusho (Liberty Aeronautical Research Institute) in 1952 in order to develop a helicopter with a jet-driven main rotor.
The JKK completed the design and construction of its first prototype in August, 1952. It was a light single-seat aircraft with a two-blade rotor of 7.3m diameter. Troubles with the transmission system and jet-nozzles led to its abandonment before the end of the year. No greater success was achieved with the original 100mm pulse-jet engine, designed by Mr. Takeo Kimura to power the helicopter, because it proved difficult to ignite and its noise level was unacceptable. Subsequent prototypes have had ramjet engines.
Two of these prototypes, designated the JHX-2 and JHX-3, were completed in March and September, 1955 respectively. Two years later the JKK was disbanded, but Mr. Hagiwara has continued his work with technical assistance from the Civil Aeronautics Agency and the Tokyo Metropolitan Aeronautical Engineering School. The first result of this collaboration is the JHX-4 helicopter, described hereafter.
THE HAGIWARA JHX-4
First flown in late September, 1958, the JHX-4 is a single-seat light helicopter with a two-blade main rotor which is driven by tip-mounted ramjet engines.
The rotor turns at 600 rpm. No weight and performance details are available, except that the JHX-4 has an endurance of 30 minutes.
Jane's All the World's Aircraft, 1959-60