The Nakajima C6N Saiun (Painted Cloud) 'Myrt' was a fast long-range reconnaissance aircraft that entered service in the summer of 1944 and was almost immune to Allied interception.
Work on the C6N began soon after Japan entered the war. In 1941 torpedo bombers were used to fly reconnaissance missions from aircraft carriers, but in the spring of 1942 the Navy issued a specification for a purpose-built long range reconnaissance aircraft.
The specification called for a three-seat aircraft with a top speed of 403mph at 19,685ft, a normal range of 1,727 miles and a maximum range of 3,078 miles.
The Nakajima design team was led by the engineers Yasuo Fukuda and Yoshizo Yamamoto. The specification was very challenging, and their first suggestion was for a very unusual twin engined aircraft, with the engines in the fuselage but the propellers on the leading edge of the wings. This would eliminate the engine nacelles and thus reduce drag, but would also have greatly increased the complexity of the design.
This plan was abandoned when the Nakajima Homare eighteen-cylinder double-row air cooled radial engine became available. The double row layout meant that the new engine provided more power for the same frontal area as a single row radial engine, and allowed Nakajima to produce a more conventional design. The basis of the new design was a low wing single engine monoplane, somewhat similar to the Nakajima B6N Tenzan. In order to keep the fuselage cross-section as small as possible the oil cooler had to be mounted outside the engine. The design was also constrained by the size of carrier lifts, and so the vertical tail surfaces were leant forward to reduce the length of the aircraft. The thin wings still had enough room for four protected fuel tanks and two unprotected tanks, allowing the aircraft to carry 300 gallons of fuel internally. Another 160 gallons could be carried in a drop tank. The aircraft was not expected to engage in combat and so it was only given a single rear firing 7.7mm machine gun.
The prototype was powered by the 1,820hp Homare 11 engine with a four-blade constant-speed propeller. It made its maiden flight on 15 May 1943 and a series of trials began. The new engine was problematic, with power falling off unexpectedly at altitude. The prototype's top speed was only 397mph.
The first prototype was followed by eighteen more prototypes and pre-production aircraft. Some of these had the 1,990hp Homare 21 engine, with a three-blade constant-speed propeller.
The C6N was a great improvement over the D4Y2-C then being used for reconnaissance. In the spring of 1944 it was officially ordered into production as the Navy Carrier Reconnaissance Plane Saiun (Painted Cloud).
The C6N1 entered service in the summer of 1944 and took part in the fighting in the Marianas Islands. Its speed was close to that of the Grumman F6F-5 Hellcat, making it almost impossible to intercept. For the last year of the war the Japanese were thus able to shadow the American fleets, but their worsening position meant that they were unable to take advantage of the information they gained.
A number of variants of the C6N were designed or produced.
The C6N1-B Saiun Model 21 was to be a torpedo-bomber variant, carrying one torpedo under the right-hand side of the fuselage. The project was abandoned after Japan lost her carrier force.
The C6N1-S was a night fighter variant designed to attack the B-29. It had a crew of two, with the rear gunner removed. The weight saved was used to install two obliquely mounted 20mm Type 99 cannon. A small number were converted and they were the fastest of the Japanese night fighters, but without effective airborne radar they weren't able to make many interceptions.
One prototype of the C6N2 was produced. This used the turbosupercharged NK9K-L Homare 24 engine, but the new engine was troublesome and the design hadn’t been perfected by the end of the war.
The C6N3 Saiun KAI 1 would have been the designation for a night fighter version of the aircraft powered by the turbosupercharged engine, but problems with the C6N2 meant that it was never built.
Three more variants were planned, none of which were ever built.
The C6N4 Saiun KAI 2 would have been powered by a Mitsubishi MK9A engine
Details of the C6N5 Saiun KAI 3 are sparse.
The C6N6 Saiun KAI 4 would have been built from wood in an attempt to save rare materials.
Engine: Nakajuma NK9H Homare 21 radial piston engine
Span: 41ft 0in
Length: 36ft 1in
Height: 12ft 11.5in
Empty weight: 6,543lb
Maximum take-off weight: 11,596lb
Max speed: 379mph at 20,015ft
Climb Rate: 8 min 9 sec to 19,685ft
Service ceiling: 35,235ft
Range: 3,299 miles
Armament: One rear-firing 7.92mm machine-gun on trainable mount