In February 1940 Kawasaki were instructed to commence work on a heavy intercepter fighter design using the German Daimler-Benz DB 601A in-line liquid-cooled engine, for which the firm had already obtained manufacturing rights. The specification for the Ki-60 was issued at the same time as that for the Ki-61, but was given priority as it was intended to be superior in speed, climb rate and armament. At that time the army's standard fighter was the radial-engined Nakajima Ki-27 which had good manoeuvrability rather than speed and was thus the antithesis of the Ki-60 concept.
The Ki-60 was developed by a design partnership of Takeo Doi and Sin Owada, the first prototype flying in March 1941. It was a low-wing all-metal cantilever mono-plane with a short fuselage of rather humped appearance. The main wheels retracted inwards to lie entirely within the wing profile, and the tail wheel was also retractable. The wings and horizontal tailplane had straight taper. With the 1100-hp DB 601A engine a top speed of 550 km/h (342 mph) was attained, less than the designers' estimates. Armament was four 20-mm (0.79-in) cannon, two in the wings and two fuselage-mounted.
The second prototype was modified to have increased wing area, a cleaner engine cowling and a slightly lighter structure. The increase in speed of only 10 km/h (6 mph) was disappointing, but the landing speed was reduced. A third and final prototype was built, with a smoother cowling, but only another 10 km/h in top speed was gained and Ki-60 development was cancelled in favour of the Ki-61.
Engine: 1 x Deimler-Benz DB 601A, 860kW
Wingspan: 10.5 m / 34 ft 5 in
Length: 8.47 m / 27 ft 9 in
Height: 3.7 m / 12 ft 2 in
Wing area: 16.2 sq.m / 174.38 sq ft
Empty weight: 2150 kg / 4740 lb
Max take-off weight: 2750 kg / 6063 lb
Max. speed: 560 km/h / 348 mph
Ceiling: 10000 m / 32800 ft
Armament: 2 x 12.7mm machine-guns, 2 x 20mm cannons