The Tachikawa Aeroplane Company, established at Tachikawa in 1924, was regarded as a comparatively small organisation before the beginning of the Pacific war. However, in 1937 it began the design of a two-seat army co-operation aircraft that was to change the company image. First flown in prototype form on 20 April 1938, the Tachikawa Ki-36 was a cantilever low-wing monoplane of all-metal basic structure, covered by a mix of light alloy and fabric. Landing gear was of fixed tailwheel type, the main units enclosed in speed fairings, and power was provided by a 450-hp (336-kW) Hitachi Ha-13 radial engine. The two-man crew was enclosed by a long 'greenhouse' canopy and both men had good fields of view, that of the observer being improved by clear-view panels in the floor. Flown in competitive trials against the Mitsubishi Ki-35, Tachikawa's design proved to be the more effective and the type was ordered into production in November 1938 as the Army Type 98 Direct Co-Operation Plane, company designation Ki-36; generally similar to the prototypes, they were armed with two 7.7-mm (0.303-in) machineguns and introduced the more powerful Hitachi Ha-13a engine. When construction ended in January 1944, a total of 1,334 had been built by Tachikawa (862) and Kawasaki (472). An advanced version of the Ki-36 was proposed under the designation Ki-72, gaining improved performance by installation of the 600-hp (447-kW) Hitachi Ha-38 engine and retractable landing gear, but no examples were built.
The handling characteristics and reliability of theKi36 made the army realise that it was ideal for use as an advanced trainer, resulting in development of the Ki55, intended specifically for this role, and having armament reduced to a single forward-firing machinegun. Following the testing of a prototype in September 1939, the army ordered this aircraft as the Army Type 99 Advanced Trainer; when production was terminated in December 1943 a total of 1,389 had been built by Tachikawa (1,078) and Kawasaki (311).
Both versions were allocated the Allied codename 'Ida', and the Ki-36 was first deployed with considerable success in China. However, when confronted by Allied fighters at the beginning of the Pacific war it was found to be too vulnerable, being re-deployed in China where it was less likely to be confronted by such aircraft. It was also considered suitable for kamikaze use in the closing stages of the war, being modified to carry internally a bomb of up to 1,1021b (500 kg).
Powerplant: one 510-hp (380-kW) Hitachi Ha-13a 9cylinder radial piston engine
Performance: maximum speed 216 mph (348 km/h) at 5,905 ft (1800 m); cruising speed 146 mph (235 km/h); service ceiling 26,740 ft (8150 m); range 767 miles (1235 km)
Weights: empty 2,749 lb (1247 kg); maximum take-off 3,660 lb (1660 kg)
Dimensions: span 38 ft 8 1/2 in (11.80 m); length 25 ft 3 in (8.00 m); height 11 ft 11 1/4 in (3.64 m); wing area 215.29 sq ft (20.00 m2)
Armament: two 7.7-mm (0.303-in) machine-guns (one forward-firing and one on a trainable mounting in the rear cockpit), plus an external bombload of up to 331 lb (150 kg)
An evolved version with a 600-hp (447-kW) Hitachi Ha-38 engine and retractable undercarriage, not built.