Not 20's 0r 30's but did not now were to put it. Engine cooling was provided by two radiators: one mounted on each side of the rear fuselage. The radiators had a wide air inlet protruding slightly out from the fuselage. Airflow through each radiator was controlled by an actuated exit door. In addition, within the fuselage a small 60 hp turbine drove a fan to further assist cooling. The aircraft stood 10 ft 7/8 in (3.07 m) tall and weighed 4,255 lb (1,930 kg) empty. The Ki-78 first flew on December 26, 1942 and was found to be extremely difficult to fly at low speeds and had poor stall characteristics. The aircraft was heavier than the design estimates, which increased the wing loading. Even with the special flaps and drooping ailerons, take-off and landing speeds were both high at 127 mph (205 km/h) and 106 mph (170 km/h) respectively. In addition, elevator flutter was experienced at the relatively low speed of 395 mph (635 km/h) but was subsequently cured by fitting a horn-balance to the elevator.