The designation Kawasaki Ki-91 was given to a design for a four-engined heavy bomber under development in Japan between 1943 and 1945. It was to be powered by four 2,500hp Mitsubishi Ha-214 Ru engines, and have a pressurized cabin. It would have been very heavily armed, carrying twelve 20mm cannon, four in a tail turret and the remaining eight in four twin turrets - one in the nose, one dorsal turret and two ventral turrets. The Ki-91 would have been larger than the Boeing B-29 Superfortress, and with a much wider radius of action, but only half of the bomb load.
Work began on the design in May 1943, and by the end of 1944 a prototype was under construction as were the tools needed for full scale production. In February 1945 the tooling was destroyed during a B-29 raid, and work on the project was suspended.
Engine: Four Mitsubishi Ha-214 Ru engines
Power: 2,500hp each
Wing span: 157ft 5in
Length: 108ft 3in
Loaded Weight: 127,868lb
Max Speed: 360mph at 32,810ft
Range: 6,214 miles maximum, 2,796 miles radius of action
Armament: Two 20mm cannon in nose, dorsal and two ventral turrets, four 20mm cannon in tail turret.