Kawasaki Ki-78

Begun in 1938 as a civil project for use in a high-speed research programme and for a contemplated attempt on to break the world air speed record, the KEN III (indicating Kensan III or Research III) project was taken over by the Imperial Japanese Army under the Ki-78 designation upon Japan's entry into the war.

Designed by a team from the Aeronautical Research Institute of the University of Tokyo, led by Shoroku Wada and comprising Mineo Yamamoto (fuselage design), Eichiro Tani (wing design) and Seichi Kurino and Shojiro Nomura (engine installation), the Ki-78 introduced several advanced design features not previously used by the Japanese aircraft industry. To minimize drag a fuselage of minimum cross section was designed and a laminar flow section was adopted for the wings. As the wing area was remarkably small, 11 sq m (118.404 sq ft), a combination of Fowler and split flaps and drooping ailerons was selected to reduce landing speed. An imported 1,175 hp Daimler-Benz DB 601A twelve-cylinder inverted-vee liquid-cooled engine was selected to power the aircraft and was modified to incorporate a system of water-methanol injection - the first such device used in Japan - to momentarily boost its power to 1,550 hp. Radiators of small frontal area were mounted on each side of the rear fuselage, and a fan, driven by a 60 hp turbine, was used to improve cooling.

A wooden mock-up of the KEN III was completed in May 1944 and production of two prototypes was entrusted to Kawasaki, where Isamu Imashi took charge of the project. Eventually only the first prototype, construction of which had begun at Gifu in September 1941, was completed and this aircraft first flew on 26 December, 1942. It was found extremely difficult to fly at low speeds, and take-off and landing speeds were respectively 205 km/h (127 mph) and 170 km/h (106 mph). Furthermore, loaded weight and wing loading exceeded calculated values and elevator flutter was experienced at 635 km/h (395 mph). On 27 December, 1943, during its 31st flight, the Ki-78 reached a maximum speed of 699.6 km/h (434.9 mph) at 3,527 m (11,539 ft). This was considerably less than the speed of 850 km/h (528 mph) which had been set as the ultimate goal for the programme. To achieve the calculated performance too many airframe and engine modifications were required and the flight trials of the Ki-78 were suspended after the 32nd flight, on 11 January, 1944.

Technical Data
Manufacturer: Kawasaki Kokuki Kogyo KK (Kawasaki Aircraft Engineering Co Ltd).
Type: Single-engined high-speed research aircraft.
Crew (1): Pilot in enclosed cockpit.
Powerplant: One Daimler-Benz DB 601A twelve-cylinder inverted-vee liquid-cooled inline engine, driving a three-blade metal propeller.
Dimensions: Span 8 m (26 ft 2 31/32 in); length 8.1 m (26 ft 6 29/32 in); height 3.07 m (10 ft 0 7/8 in); wing area 11 sq m (118.403 sq ft).
Weights: Empty 1,930 kg (4,255 lb); loaded 2,300 kg (5,071 lb); wing loading 209 kg/sq m (42.8 lb/sq ft); power loading 2 kg/hp (4.4 lb/hp).
Performance: Maximum speed 700 km/h (435 mph) at 3,500 m (11,485 ft); ceiling 8,000 m (26,245 ft); range 600 km (373 miles).
Production: One Ki-78 was completed by Kawasaki Kokuki Kogyo KK, at the Gifu plant in December 1942.