Profile Publications No. 105 The Kawasaki Ki-45 Toryu

Second prototype, with closer-fitting cowlings and spinners added. The exhaust collector ring around the cowling leading edge characterises Ha-20h-powered aircraft. still failed to give satisfaction a ducted spinner fairing neatly with the cowling was selected for the third prototype (c/n 4503) completed in May 1939. Cooling air was forced through the centre of the ducted spinners and exhausted through slots in the wings ahead of the aileron/flap lines. In addition c/n 4503 was fitted with an electrically operated undercarriage retraction mechanism. The undercarriage problem was thus solved but flight trials were still disappointing due to nacelle stall and engine drag. By the end of 1939 the maximum speed attained by the three Ki-45 prototypes was 480 km/h. (298 m.p.h.) at 4,000 m. (13,125 ft.). At that time six additional prototypes were in various stages of manu­facturing: c/n 4504 through 4506 had already been fitted with a pair of Nakajima Ha-20b whilst c/n 4507 through 4509 were yet without powerplant. To eradicate the nacelle stall Kawasaki suggested the use of opposite-rotating airscrews to replace the right-hand rotating airscrews fitted to the first three prototypes. Although this modification appeared promising at the time as regards the stall problem the aircraft would still have been underpowered and unable to meet the speed requirement. Consequently this modification was not realized and flight trials were curtailed pending review of the project by the J.A.A.F. IMPROVED PROTOTYPES In April 1940 the Koku Hombu (Air Headquarters) of the Imperial Japanese Army instructed Kawasaki to install a pair of 14-cylinder radial Nakajima Ha-25 on one of the uncompleted airframes. Not only was the Ha-25 more powerful (1,050 h.p. at 8,340 ft. and 970 h.p. at take-off) than the Ha-20b but it had a smaller diameter. Kawasaki, which had cause to fear the cancellation of the project, gladly accepted and mounted the new engines in N.A.C.A.-type cowlings with small spinners on the seventh airframe (c/n 4507). The intake for the single-stage supercharger was mounted on the wing leading edge outboard of the engine nacelles and the oil cooler intake was located under the cowling. The main undercarriage was electrically operated and the wheels were now entirely enclosed within the engine nacelles. In all other respects the new aircraft was identical to the first three prototypes and it was known as the Experimental Improved Type 1 Ki-45. Unfortunately for its manufacturer the aircraft was still bedeviled by bad luck and on its first take-off, in July 1940, a cowling flap was torn away forcing the pilot to make an emergency landing in which damage to the under­carriage, the propellers and a wingtip was incurred. A month later the aircraft was repaired and was soon joined by seven additional test aircraft including the re-engined fourth, fifth, sixth, eighth and ninth prototypes (c/n 4504,4505,4506,4508 and 4509). By then the undercarriage was reliable, the nacelle stall and drag had been eradicated, and the Experi­mental Improved Type 1 Ki-45 almost met the speed requirement when one of these aircraft was clocked at 520 km/h (323 m.p.h.) at 3,500 m. (11,480 ft.). Ki-45 K aizo (Modified) Whilst flight trials of the Experimental Improved Type 1 Ki-45 was getting underway, Takeo Doi and his team initiated a complete redesign of the aircraft to correct the last deficiencies, to improve the per­formances and to simplify quantity production. Kawasaki suggested that the elliptical wing used on the 1 1 prototypes be replaced by straight tapered surfaces increasing span by 0-5 m. (1,640 ft.) and An improved Type I Ki-45 prototype with Ha-25 powerplants. Note the supercharger intake on the wing leading edge just out hoard o f the nacelles. 5
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