Nakajima C6N saiun "Myrt" (1944)
Imperial Japanese Navy 1943-45, 463 built
Design development
The C6N was developed from a 1942 IJN specification calling for a carrier-based reconnaissance plane with a specified speed of 350 knots (650 km/h) at 6,000 over 2,500 nautical miles (4,960 km) or range. Nakajima proposed its N-50 at first, which had two 1,000 hp (750 kW) engines in tandem inside the fuselage and driving two propellers on the wings to help clean up the latter from any drag.But since the company also worked on the latest Homare capable of 2,000 hp (1,500 kW) the dual powerplant, which had known cooling issues, was abandoned. Nakajima decided went for the single-engine layout, but meantime, engineers of the engines department bank tests were less than stellar. The output fell short of expectations. The project had to be revised to be as nimble, light and streamlined as possible. The C6N made its first flight on 15 May 1943. The prototype demonstrating 639 km/h (345 kn; 397 mph), less than specified, and it was by pushing Homare engine to its very limits. It proved generally was disappointing especially at altitude. Therefore Nakajima went on pushing the enveloped on 18 further prototypes and pre-production models. Eventually, it seems the last was ablt to reach the specified 650 kph and had better altitude characteristics, and the Saiun was ordered at last by the IJN in February 1944.
Detailed Design
The final result had a long and extremely narrow cylindrical fuselage: Its diameter started as the same as the engine and was narrowed gradually down to the tail. There was a single, long canopy under which sat all three crewmen in tandem: Pilot, Observer and rear gunner. Due to weight savings, there were no armor anywhere to protect the pilot but at least self-sealing tanks.
General structure and wings
The C6N had classic Nakajima low-mounted laminar flow wings, which span was almost equal to the fuselage, and which housed fuel tanks. They were fitted with Fowler and slit flaps, plus leading-edge slats helping to diminish landing speed as much as possible thanks to aircraft carrier use. Like the B6N Tenzan torpedo bomber they shared many characteristics and parts, including their vertical stabilizer, angled slightly forward to take less space while staying efficient, calculated with drag in mind. Construction was all-metal, with stressed duralumin over aluminium framing and steel internal structural framing. The landing gear was classic, deploying outwards for a better landing span, same as the B6N. The tail wheel was fully folding inside, leaving no bump. In general the profile was very clean, with as few asperities as possible, including no air intake.Powerplant & Performances
The prototype flew with a Nakajima NK9B Homare 11, which was a 18-cylinder, air-cooled radial piston engine which devemoped 1,485 kW (1,991 hp) less than the expected 2,000 hp. The output treshold was surpassed with the Homare 23, 25 and the late war Homare 42 producing 2,200 hp (1,640 kW). Unfortunately it was way too big to fit the C6N. Nevertheless, the Myrt was upgraded to the NK9K-L Homare 22 and Nakajima NK9H Homare 21 in tests, the production C6N1 Saiun Model 11 with its three-blade propeller being equipped with the NK9H Homare 21 engine. The best variant was the C6N2 Test production Saiun Kai which had a four-blade propeller and the new 1,980-hp (1,476-kW) Nakajima NK9K-L Homare 24-Ru turbocharged engine for altitude flights. Only two prototypes in February 1945 tests this configuration.
Armament
Due to its role and speed constraints, the C6N carried no significant armament as designed, just a single lexibly-mounted, rearward-firing 7.92 mm Type 1 machine gun, manned by the tail gunner. When not in use, it was folded inside the fuselage. Theoretically, if converted as an attack plane, it could have been equipped with attach points for a variety of bombs and there was definitely hardpoints under the belly to hold an additional fuel tank, extending the range. From there it was still possible to attach a standard aerial torpedo, yet with miuch degraded performances. During the war various tests were also made as an interceptor, with an angled dorsal gun, either a pair of 20mm, or a single 30mm to deal with B-29 bombers in 1945, inspired by the German Schräge Musik system. They were tested but no production followed (see variants below).Production and Variants
Only one large production variant, C6N1, and the basic Type 17 pre-production serie. About four more prototypes and 5 projects. Interestingly the success of the Mosquito led to the design of an equivalent version, the wooden-built C6N6. However like the others it remained at paper stage only.-C6N1 Experimental Type 17 carrier reconnaissance plane (17-Shi Kanjō Teisatsuki)
-3 prototypes, 16 supplementary prototypes with 4-blade propeller (later 3-blased) and NK9K-L Homare 22 engine
-Modified prototype with the NK9H Homare 21 engine renamed Shisei Saiun for pre-production in July 1943.
-C6N1 Saiun Model 11 Production model. 3-blade prop. and Nakajima NK9H Homare 21.
-Project torpedo bomber C6N1-B (Model 21)
-Prototype C6N1 Saiun Model 11 night fighter variant*
-Two C6N2 Test production Saiun Kai (Model 12), 4-blade prop. 1,980-hp (1,476-kW) NK9K-L Homare 24-Ru (turbocharged), February 1945.
-Project C6N3 high-altitude night fighter variant C6N2 with 2x 20 mm cannons.
-Incomplete prototype: C6N4 Test production Saiun Kai 2 with the MK9A Ha 43-11 Ru turbocharged.
-Project C6N5 Saiun Kai 3 torpedo bomber.
-Project C6N6 Test production Saiun Kai 4, Wooden-built.
The Night Fighter: This was not a regulation naval aircraft as the C6N1-S was not discovered in IJN official documents (otherwise burnt?). It had a 30 mm Type 5 cannon in the back, transverse-firing, five production models received two extra 20 mm Type 99-1 cannons, one of which is housed at the Paul E. Garber Preservation and Storage Facility.
Service
The C6N was deployed in the following naval air groups: -Yokosuka Kōkūtai, 121, 131st, 132nd, 141st, 171st, 210th, 302nd, 343rd, 701st, 723rd, 752nd, 762nd, 801st and 1001st Kōkūtai. It was also used by the Navy land-based Aerial Squadron for Reconnaissance, and the 3rd, 4th, 11th, 12th and 102nd Hikōtai. It was also used by Kamikaze groups in mid-1945, the 1st Mitate Special Attack Group (from 752nd Kōkūtai, active), Sairyū Unit (from 752nd Kōkūtai, disbanded without a first sortie) and "Saiun Unit" (models from 723rd Kōkūtai, no sortie).⚙ specifications | |
| Empty Weight | 2,968 kg (6,543 lb) |
| Gross Weight | 4,500 kg (9,921 lb) |
| Max TO Weight | 5,260 kg (11,596 lb) |
| Length: | 11 m (36 ft 1 in) |
| Wingspan: | 12.5 m (41 ft 0 in) |
| Airfoil: | K151 ; tip: K159 |
| Height: | 3.96 m (13 ft) |
| Wing area: | 25.5 m2 (274 sq ft) |
| Wing Loading: | 176 kg/m2 (36 lb/sq ft) |
| Engine | Nakajima NK9B Homare 11 18-cylinder air-cooled radial piston engine, 1,485 kW (1,991 hp) |
| Propeller | Fixed pitch, 4 bladed metal, constant-speed metal propeller |
| Power/mass: | 0.33 kW/kg (0.20 hp/lb) |
| Top Speed | 610 km/h (380 mph, 330 kn) at 6,100 m (20,013 ft) |
| Cruiser Speed | 390 km/h (240 mph, 210 kn) |
| Rate of climb | ? |
| Time to altitude: | 6,000 m (19,685 ft) in 8 min 9 sec |
| Ceiling | 10,470 m (34,350 ft) |
| Ferry Range | 5,300 km (3,300 mi, 2,900 nmi) (with auxiliary fuel) |
| Range | ? |
| Armament | 1× flexibly mounted rearward-firing 7.92 mm Type 1 MG |
| Crew | 3: Pilot and observer, gunner |
C6N-1 Prototype in 1943
C6N-1 Model 11, Atsugi Naval Air Base, Kanagawa Prefecture, 3th Hikotai, 302th Kokutai, 1945
C6N-1, 11th Hokutai, 762th Kokutai, March 1945
C6N planned for IJN Shinano before she was sunk in 1944.
Suicide Attack Group Azusa Tokubetsu Kougekitai Kanoya NB March 1945
C6N-1 Matsuyama Naval Air Base, Ehime Prefecture, February 1945
C6N1-S of Kokutai 302, Atsugi Air Base, August 1945. Experimental interceptor with an oblically-mounted Type 5 30 mm gun. Crew: Hiroshi Yakuda, Taro Fukuda. One combat mission, in teh night of 1st August, firing ten rounds at a B-29. Fate unknown.
Nakajima C6N on tarmac
Nakajima C6N at Oppoma air base, 1945
Nakajima C6N-1 of a reconnaissance aircraft 121st Kokutai