Imperial Japanese Army aircraft confronted by the Soviet-built Tupolev SB-2 bomber, providing support for the Chinese during 1937. were somewhat shattered by its capability, its maximum speed being such that Japanese army fighter aircraft were virtually unable to intercept except when a standing patrol found itself in a position to launch a surprise attack. Almost at once the army instructed Kawasaki to begin the design of a twin-engine light bomber of even better capability, specifying a maximum speed of about 301 mph (485 km/h). Work on what was to become known as the Kawasaki Ki-48 began in January 1938, the result being a cantilever mid-wing monoplane with conventional tail unit. retractable tail wheel landing gear and, in the type's prototype form, two 950-hp (708-kW) Nakajima Ha-25 radial engines mounted in nacelles at the wing leading edges. The fuselage provided accommodation for a crew of four (the bombardier. navigator and radio-operator each doubling as gunners) and also incorporated an internal bomb bay.
Involvement in the Ki-45 programme delayed the maiden flight of the first of four Ki-48 prototypes until July 1939, but tail flutter problems then caused further delay until the introduction of modifications. Service testing resulted in unqualified approval of the type, which was ordered into production in late 1939 under the official designation Army Type 99 Twin-engined Light Bomber Model 1A (company designation Ki-48Ia). Armament of this version comprised three 7.7-mm (0.303-in) machine-guns on flexible mounts in nose, dorsal and ventral positions, plus up to 882 lb (400 kg) of bombs, this being unchanged in the improved Ki-48-Ib that followed the Ki-48-la into production, and differed by introducing minor equipment changes and detail refinements; manufacture of these two initial versions had totalled 557 when production ended in June 1942.
Ki-48s entered service in the summer of 1940, becoming operational in China during the autumn of that year. In China their speed gave the Ki-48's almost complete immunity from enemy defences, but their deployment against Allied aircraft at the beginning of the Pacific war revealed that their superior performance was illusory. Codename 'Lily' by the Allies, this initial production version had a number of deficiencies for the different kind of operations then required, and it was fortunate for the Japanese army that an improved version was already under development. This had the company designation Ki-48-II and differed from the earlier model by introducing a slightly lengthened fuselage, protected fuel tanks, armour protection for the crew, increased bombload and more powerful Nakajima Ha-U5 engines, an advanced version of the Ha-25 which incorporated a two-stage supercharger. The first of three prototypes was completed in February 1942, and in the spring of that year the type entered production as the Army Type 99 Twin-engined Light Bomber Model 2A (company designation Ki-48-IIa). It was built also as the Ki-48-IIb which, generally similar to the Ki-48-IIa, was intended for use in a dive-bombing role, and so incorporated dive brakes in the undersurface of each outer wing panel. Final production variant was the Ki-48-IIc, also basically the same as the Ki-48-IIa, but with improved armament. A total of 1,408 Ki-48-IIs of all versions was built, to bring overall production to 1,977 including prototypes.
Unfortunately for the Japanese army, when the Ki48- II was introduced into operational service its speed was still too low and its defensive armament inadequate to provide a reasonable chance of survival against Allied fighter aircraft. Attempts to increase armament merely upped the overall weight and speed suffered proportionately: it was clear by the summer of 1944 that the day of the Ki-48 had passed, and in October it was declared obsolescent. The majority ended their days in kamikaze attacks, but some examples were used as test-beds for the experimental Ne-O turbojet engine and Kawasaki's Igo-1B radio-guided bomb.
Four prototypes with Ha-25 engines of 708 kW (950 hp), and five pre-production aircraft, with modified tail surfaces.
Army Type 99 Twin Engine Light Bomber Model 1A; as first series model. Produced from 1940, 557 built.
Similar to the Ia, with changes in defensive machine gun mountings.
* Total production of Ki-48 Ia and Ib: 557 aircraft
Three prototypes built.
Fitted with more powerful engines, a longer fuselage, additional armour, and larger bomb load. Produced from April 1942.
Dive bomber version, with reinforced fuselage and dive brakes.
Improved defensive weapons. Produced from 1943.
* Total production of Ki-48 IIa, IIb and IIc: 1,408 aircraft
Ki-48-II KAI Kamikaze (Type Tai-Atari)
Conversion with 800 kg (1,760 lb) of explosives and two or three pilots for kamikaze missions
* Total production of all versions: 1,977 aircraft
Proposed version of the Ki-48. Not built.
Single-seat special attack version. Not built.
Type: four-seat light/dive-bomber
Powerplant: two 1,150-hp (858-kW) Nakajima Ha-115 14-cylinder radial piston engines
Performance: maximum speed 314 mph (505 km/h) at 18,375 ft (5600 m); service ceiling 33,135 ft (10100 m); maximum range 1,491 miles (2400 km)
Weights: empty 10,0311b (4550 kg); maximum takeoff 14,8811b (6750 kg)
Dimensions: span 57 ft 3 in (17.45 m); length 41 ft 10 in (12.75 m); height 12 ft 5V2 in (3.80 m); wing area 430.57 sq ft (40.00 m2)
Armament: three 7.7-mm (0.303-in) machine-guns on trainable mounts in nose, dorsal and ventral positions, plus up to 1,764 lb (800 kg) of bombsOperator: Japanese Army