Tuesday, March 3, 2015

Kawasaki Ki-48 Redux

It is a remarkable fact that the Japanese Army Air Force's first modern light twin-engined bomber, a machine produced in greater numbers monthly than any other twin-engined type by Japan's wartime aircraft industry, and one which was active throughout the Pacific War and in every area in which the JAAF was engaged, should today be one of the least-known of Nipponese operational aircraft.

Yet the Ki.48, or Type 99 Light Bomber, produced by the Kawasaki Kokuki Kogyo K.K., and known to the Allies by the singularly inappropriate code name of Lily, enjoyed such an in-auspicious career and was so completely devoid of outstanding characteristics, that it achieved neither prominence nor notoriety. Yet nearly two thousand aircraft of this type rolled off the assembly lines between mid 1939 and October, 1944.

In 1937, the JAAF issued a specification for a light bomber with longer range and greater offensive potentialities than existing single-engined aircraft. Possibly influenced in their choice of a twin-engined machine by the Bristol Blenheim, the JAAF desired increased mobility with an eye to possible operations against Russian forces on the Manchurian border. To meet the requirements of this specification, Kawasaki evolved an all-metal twin-engined mid-wing cantilever mono-plane, and the first of nine prototypes, designated Ki.48, flew in July, 1939. Initial trials indicated some instability and flutter, and early modifications were the strengthening of the rear fuselage and the raising of the horizontal tail surfaces by fifteen and a half inches. Before the end of the year quantity production of the aircraft had been initiated under the designation Type 99 Light Bomber Model 1.

The bomber was powered by two Nakajima Ha.25 fourteen-cylinder air-cooled radial engines, each rated at 1,000 h.p., for take-off, and 980 h.p. at 9,840 ft., carried four or five crew members; a defensive armament of three flexible 7.7-mm. machine guns, and an internally-housed bomb load of 660 pounds. Actual production deliveries began in July, 1940, and the Type 99 Model I (Ki.48-I) was immediately dispatched to China for operational trials. Neither the offensive potentialities nor performance of the bomber were outstanding, normal bomb load being twenty-four 33-lb. bombs or six 110-lb. bombs, and maximum and cruising speeds were 298 m.p.h. and 217 m.p.h. at 11,480 ft. respectively. Range with maximum bomb load was 1,230 miles, and with maximum fuel was 1,490 miles, an altitude of 16,400 ft. was attained in nine minutes, and empty and loaded weights were 8,929 lb. and 13,337 lb. respectively. There were minor defensive armament differences between the Ki.48-Ia and -Ib, but both stability and manoeuvrability of the bomber were poor, and improvements were obviously necessary from an early date in its career. Nevertheless, 557 Kawasaki Ki.48-I bombers were built before the first of three prototypes of the Ki.48-II made its appearance in February, 1942.

The principal differences between the Ki.48-I and -II were to be found in the engines, defensive armament and armour protection. The new model had Nakajima Ha.115 fourteen-cylinder air-cooled radials rated at 1,130 h.p. for take-off and 1,100 h;p. at 9,350 ft., the fuel tanks were protected, and 12.5-mm. and 6.5-mm. fore and aft armour protection was provided for the crew members. Initially the defensive armament remained a trio of 7.7-mm. guns, but the additional power permitted an increase in bomb load to 1,760 lb. in maximum loaded condition. Whereas the Type 99 Model 2a (Ki.48-IIa) was built as a level bomber, the Model 2b (Ki.48-IIb) was fitted with dive brakes under each wing, and was capable of dive-bombing attacks up to an angle of sixty degrees. Late production machines of this type featured a dorsal fin extension. The Model 2c (Ki.48-IIc) was essentially similar to the Model 2b apart from the addition of a single 12.7-mm. gun to the defensive armament.

Jet and Fighter variants

The Type 99 Model 2 was soon active wherever the JAAF appeared, and in 1944, four machines were modified as parent aircraft for the Kawasaki-built I-Go-lb guided missile which entered production in January, 1945, the Type 99 with bomb-bay doors removed serving as its principal carrier. One machine was modified as a flying test bed for the Ne.00, the first indigenous turbojet, and among several proposed variants which did not materialise was the Ki.81 heavy multi-seat fighter variant. Heavily armed and armoured, the Ki.81 was designed for the exclusive use of the formation leader. When production finally terminated in October, 1944, no less than 1,408 Type 99 Model 2 bombers had been built, bringing total production of all Ki.48 aircraft, including prototypes, to 1,977 machines.

The Type 99 Model 2c (Ki.48-IIc) possessed the following overall dimensions: span, 57 ft. 3 ¾ in.; length, 42 ft. 2 ¾ in.; height, 12 ft. 0 ½ in.; wing area, 430.556 sq. ft. Defensive armament comprised one 7.7-mm. machine gun with 600 rounds in the nose, two 7,7-mm. or one 12.7-mm. machine gun in the dorsal position, and one 7.7-mm. machine gun with 500 rounds in the ventral position. Alternative bomb loads comprised six 110-lb. bombs or four 220-lb. bombs, and empty and maximum loaded weights were 10,031 lb. and 14,881 lb. Performance included a maximum speed of 314 m.p.h. at 18,372 ft., the ability to climb to 16,400 ft. at maximum loaded weight in 9 min. 56 sec., a maximum ceiling of 32,800 ft., and a maximum range of 1,490 miles.

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