Unlike in earlier projects, the Imperial Japanese Army issued in February 1936 detailed specifications that had to be met by the new aircraft. These included a maximum speed 399 km/h (248 mph) at 3,000 m (9,840 ft); climb to altitude in under eight minutes; take-off in less than 300 m (980 ft); normal operating altitude from 2,000 m (6,560 ft) to 4,000 m (13,120 ft); and endurance of more than five hours at 299 km/h (186 mph) at 3,000 m (9,840 ft). Structural strength was specified as well, including a load factor of 6 while at high angle of attack, and 4 while in a glide. Minimum bombload for short-range missions was to be 1,500 kg (3,310 lb) with a variety of load configurations. Loaded, the bomber was to have a weight of less than 1,000 kg (2,200 lb). Other specified requirements were a crew of from four to six; engines to be either the Nakajima Ha-5 or Mitsubishi Ha-6; and three gun positions (nose, dorsal and ventral, each with one flexible 7.7 mm (0.303 in) Type 89 machine gun). The Hi-2 (Type 94) or Hi-5 radio, and other details were also specified.[2]
Performance testing by the Tachikawa Army Air Technical Research Institute with the competing Mitsubishi Ki-21 lasted from March to May 1937. Evaluation was continued at the Army's main bomber base at Hamamatsu for bombing and other operational testing beginning in June. Not completely satisfied with the combinations of airframe and engines, the Army ordered to both Ki-19 prototypes to be powered by Mitsubishi Ha-6 engines, while the two prototypes of the Mitsubishi Ki-21 also converted to be powered by Nakajima Ha-5 engines.[2]
Prototypes from the two companies were almost identical in performance, but the Army officially selected the Mitsubishi Ki-21 as the "Army Type 97 Heavy Bomber", Nakajima having lost the Army contract.[2]
The fourth[2] prototype was converted to the mail plane in April 1939 it got the new designation N-19. It was commonly referred to as the N-19 Long-Range Communications Aircraft and sold to the Domei Tsushin (Domei Press Agency), under registration J-BACN and was named Domei No.2.[2]
Variants
Ki-19 : Prototype for testing (2 units produced in 1937)
