Wednesday, April 15, 2015
While the Navy struggled with the Nakajima G8M Renzan ( Mountain Range ) four engined bomber ( which was hampered by allied air attacks and material shortages ), Kawasaki undertook a four engined design for the Army and this was the Ki-91.
Kawasaki began investigating this design in May of 1943 but progress was slow. The Ki-91 featured a fully pressurized cabin and had a radius of action of 2,796 miles with a 8,818lb. bomb load. While this range was 436 miles more than the Ki-67 Hiryu, the bomb load able to be carried by the Ki-91 was 7,053lbs. more than the Ki-67, a substantial payload improvement. If the bomb load was less, a maximum range of 6,214 miles could have been reached. The estimated speed of 360mph for the Ki-91 was 26mph faster than the Ki-67. All around, the Ki-91 was proving to be a superior airplane to the best of the bombers then in service.
The defensive armaments for the Ki-91 were heavy, easily outgunning the weapon fits of the Ki-67. There were five power-operated turrets, all but one of them mounting two 20mm cannon. The remaining turret, mounted in the tail, was equipped with four 20mm cannon. There was a turret in the nose, one on the top of the fuselage, and two beneath the fuselage along with the tail position.
The engine array consisted of four Mitsubishi Ha-214 Ru engines, each developing 2,500hp which would drive the plane at its maximum speed of 360mph. Two engines were mounted in each wing in streamlined cowling/nacelles.
Overall, the Ki-91 would have been 108ft . and 3in. long, have a span of 157ft. and 5in., and have a loaded weight of 127,868lbs.
As mentioned, for one reason or another, progress on getting the Ki-91 from the drafting table to flying prototype lagged. The prototype was partially complete by 1945 but a bombing raid by U.S. B-29s in February of 1945 destroyed the tools and jigs needed to complete the Ki-91 and prepare the design for production. With the required materials gone, work on the Ki-91 ceased.