The Yokosuka R2Y Keiun (Beautiful Cloud or Lucky Cloud) was a long-range land-based reconnaissance aircraft powered by two engines mounted within the fuselage and driving a single propeller.
The Japanese Navy first decided that it wanted a long range land based reconnaissance aircraft in 1942. The Naval Arsenal at Yokosuka produced the twin-engined R1Y Seiun (Blue Cloud), but this aircraft lacked the required performance.
Yokosuka already had a suitable replacement under development. In 1940 the Japanese had purchased one of the Heinkel He 119 prototypes. This aircraft was powered by two engines that were carried in the main fuselage and powered a single propeller in the nose ( a twin engined version of the system used in the Bell P-39 Airacobra).
Early in 1943 Yokosuka began work on a similar aircraft of their own, with the internal designation Y-40. The Japanese Navy decided to take advantage of this work, and issued an 18-Shi specification built around the Y-40.
The R2Y was designed by a team led by Commander Shiro Otsuki. Work was well underway when the Battle of the Philippine Sea forced the Japanese Navy to alter its priorities. Long range reconnaissance aircraft were no longer needed, and so the Yokosuka team suggested using the R2Y as an attack bomber.
The plan was to install one Ne-330 turbojet engine under each wing, replacing the fuselage mounted twin engines. The space freed up would be used for a fuel tank. The bomber version would carry a single 1,764lb bomb under the fuselage, and carry cannons in the nose. The jet powered version was expected to be significantly faster than the piston engined version.
The Japanese Navy decided to accept the modified design. Yokosuka were given permission to produce one R2Y1 piston-engined prototype to test out the aerodynamics of the design, while also working on the jet-powered R2Y2.
The R2Y had a rather chunky looking fuselage, with short low mounted wings. The crew were carried in a cockpit that was mounted well forward of the wing, with the drive shaft passing between the two seats. There was a large air scoop on the top of the fuselage behind the wings to cool the engines.
The R2Y1 prototype was ready for tests in April 1945. These didn't go well. Linked engines almost always turned out to be problematic, as seen in the Avro Manchester or the Heinkel He 177. The linked engines of the R2Y1 overheated during taxi-ing tests. The maiden flight, on 8 May, was cut short because the oil overheated. A few days later the engine caught fire while on the ground! The first prototype was then destroyed in an American bombing raid before new engines could be installed. Work on a second prototype was underway when the war ended.
The jet powered R2Y2 didn't get as far. The design was almost complete at the end of the war, but there was no prototype.
Engine: One Aichi Ha-70 10 (twin Aichi Atsuta 30) twenty-four cylinder liquid cooled engine
Power: 3,400hp at take-off, 3,100hp at 9,845ft
Crew: 2 (pilot and radio operator/ navigator)
Span: 45ft 11 3/16in
Length: 52ft 9 25/32in
Height: 13ft 10 15/16in
Empty weight: 13,261lb
Loaded weight: 17,857lb
Max speed: 447mph at 32,810ft
Climb Rate: 10min to 32,810ft
Service ceiling: 38,384ft
Range: 2,244 miles
Bomb load: None
Engine: Two Ne-330 axial-flow turbojets
Power: 2,910lb thrust each
Crew: 2 (pilot and radio operator/ navigator)Span:
Armament: Forward firing cannon
Bomb load: One 1,764lb bomb