DALLAS – Today in Aviation, the Gasuden Koken, aka the Kōken-ki, a 1930s Japanese long-range research aircraft, made its maiden flight in 1937.
The type was designed by the Tokyo Gas and Electric Industry (also known as Gasuden) to set a closed-circuit world record of 11,651 km (7,240 mi) in March 1938.
The Kōken-ki could carry a crew of three. It had a length of 15.06 m (49 ft 5 in), a height of 3.60 m (11 ft 10 in), and a wingspan of 27.93 m (91 ft 8 in) with a wing area of 87.3 m2 (940 sq ft).
The type’s maximum speed was 250 km/h (160 mph, 130 kn) and a cruise speed of 211 km/h (131 mph, 114 kn) with a range of 11,651.011 km (7,239.603 mi, 6,291.043 nmi) (record distance) and a service ceiling of 3,410 m (11,190 ft).
In 1931, the Tokyo Imperial University’s Aeronautical Research Institute began research to develop an aircraft that would break the world closed-circuit distance record, with funding provided by the Japanese Diet or parliament.
The initial design was finished in August 1934, and despite having little funding and a history of only building small quantities of wooden light aircraft, Gasuden was chosen to develop the aircraft. A single-engined low-wing cantilever monoplane with retractable undercarriage was developed by the Aeronautical Research Institute and Gasuden.
The aircraft was made entirely of aluminum and had fabric-covered outer wings and control surfaces. Although a diesel engine was originally planned, it proved impractical, so a modified version of the German BMW VIII gasoline-fueled engine, license-built by Kawasaki, was selected in the end.
The Kōken-ki took a long time to build, and it wasn’t finished until March 1937. Major Yuzo Fujita of the Imperial Japanese Army piloted the first flight on May 25, 1937.
The first two attempts to break the record, on November 13, 1937, and May 10, 1938, respectively, were unsuccessful due to undercarriage issues and an autopilot fault.
Then, on May 15, 1938, at 04:55, the Kōken-ki took off for a third time from Kisarazu, Chiba, flying a four-sided course of 402 kilometers (249 mi). It landed at Kisarazu at 19:21 on May 15, having flown a distance of 11,651.011 km (7,239 mi), setting a new world closed-circuit distance record.
This record stood until August 1939, when it was broken by an Italian Savoia-Marchetti SM.82 that flew 12,936 km. Still, the closed-circuit May 15 flight is the only aviation record ever set by Japan that has been recognized by the Fédération Aéronautique Internationale, the world governing body for aviation records (8,038 mi).
The Kōken-ki was only used for test flights on rare occasions, with the last one taking place in 1939. It survived WWII only to be destroyed at the end of the war. The Misawa Aviation & Science Museum in Misawa, Aomori, has a full-scale version of the Kōken-ki on display.