Engineering:Nakajima C6N

Short description: Japanese carrier-based reconnaissance aircraft

C6N
Nakajima C6N1
Role	Carrier-based reconnaissance aircraft
National origin	Empire of Japan
Manufacturer	Nakajima Aircraft Company
First flight	15 May 1943
Introduction	1944
Retired	1945
Primary user	Imperial Japanese Navy Air Service
Number built	463

The Nakajima C6N Saiun (彩雲, "Iridescent Cloud") was a carrier-based reconnaissance aircraft used by the Imperial Japanese Navy Air Service in World War II. Advanced for its time, it was the fastest carrier-based aircraft put into service by Japan during the war. The Allied reporting name was Myrt.

Development and design

The C6N originated from a 1942 Imperial Japanese Navy specification for a carrier-based reconnaissance plane with a top speed of 350 knots (650 km/h) at 6,000 m and range of 2,500 nautical miles (4,960 km). Nakajima's initial proposal, designated N-50, was for a craft with two 1,000 hp (750 kW) engines housed in tandem in the fuselage, driving two propellers mounted on the wings. With the development of the 2,000 hp (1,500 kW) class Nakajima Homare engine, the dual powerplant configuration was abandoned and Nakajima decided on a more conventional single-engine layout. Unfortunately the new Homare's power output was less than expected, and the design had to be optimized in other areas. The resulting aircraft was designed around a long and extremely narrow cylindrical fuselage just large enough in diameter to accommodate the engine. The crew of three sat in tandem under a single canopy, while equipment was similarly arranged in a line along the fuselage. The C6N's low-mounted laminar flow wing housed fuel tanks and was fitted with both Fowler and slit flaps and leading-edge slats which lowered the aircraft's landing speed to ease use aboard aircraft carriers. Like Nakajima's earlier B6N Tenzan torpedo bomber, the vertical stabilizer was angled slightly forward to enable tighter packing on aircraft carrier decks.

The C6N's first flight was on 15 May 1943, with the prototype demonstrating a speed of 639 km/h (345 kn; 397 mph). Performance of the Homare engine was disappointing, especially its power at altitude, and a series of 18 further prototypes and pre-production aircraft were built before the Saiun was finally ordered into production in February 1944.

Operational history

Although designed for carrier use, by the time it entered service in September 1944 there were few carriers left for it to operate from, so most C6Ns were flown from land bases. Its speed was exemplified by a telegraph sent after a successful mission: "No Grummans can catch us." ("我に追いつくグラマンなし"). The top speed of the Hellcat was indeed of the same level, so overtaking a Saiun was out of the question.

A total of 463 aircraft were produced. A single prototype of a turbocharged development mounting a 4-blade propeller was built; this was called the C6N2 Saiun-kai. Several examples of a night fighter version C6N1-S with oblique-firing (Schräge Musik configuration) single 30 mm (or dual 20 mm) cannon were converted from existing C6N1s. As Allied bombers came within reach of the Japanese home islands, a first class night fighter was required. This led Nakajima to develop the C6N1-S by removing the observer and replacing him with two 20 mm cannons. The C6N1-S's effectiveness was hampered by the lack of air-to-air radar, although it was fast enough to enjoy almost complete immunity from interception by Allied fighters. A torpedo carrying C6N1-B was also proposed, but was not needed after most of Japan's aircraft carriers were destroyed.

Despite its speed and performance, on 15 August 1945 a C6N1 happened to be the last aircraft to be shot down in World War II. Just five minutes later, the war was over and all Japanese aircraft were grounded.

Variants

Nakajima C6N1-S night fighter variant. Note the obliquely mounted 30 mm cannon in the fuselage of plane ヨD-295.

Source:Famous Airplanes of the World

C6N1 Experimental Type 17 carrier reconnaissance plane (17試艦上偵察機, 17-Shi Kanjō Teisatsuki)

Three prototypes and sixteen supplementary prototypes produced, four-blade propeller; latter batch were equipped three-blade propeller, mounted Nakajima NK9K-L Homare 22 engine, No. 6 was mounted Nakajima NK9H Homare 21 engine. Renamed Test production Saiun (試製彩雲, Shisei Saiun) in July 1943.

C6N1 Saiun Model 11 (彩雲11型, Saiun 11-gata)

General production model. Three-blade propeller, mounted Nakajima NK9H Homare 21 engine.

C6N1-B Saiun Model 21 (彩雲21型, Saiun 21-gata)

Proposed torpedo bomber version. Only a project.

C6N1 Saiun Model 11 night fighter variant (彩雲11型改造夜戦, Saiun 11-gata Kaizō yasen)

Temporary rebuilt two-seat night fighter version; this was not a regulation naval aircraft. Development code C6N1-S was not discovered in the IJN official documents. One model with a single 30 mm Type 2 cannon was built in June 1945, and at least five models with ×2 20 mm Type 99-1 cannon were converted from standard C6N1 models. One surviving example of the ×2 20mm cannon variant is stored in the Paul E. Garber Preservation, Restoration, and Storage Facility. The 30 mm version was only used to attack B-29s once, on August 1, 1945. The destructive power of the Type 2 cannon extended to twisting the skin of the Saiun's lightweight fuselage.

C6N2 Test production Saiun Kai/Saiun Model 12 (試製彩雲改/彩雲12型, Shisei Saiun Kai/Saiun 12-gata)

Fitted with four-blade propeller, 1,980 PS (1,456 kW) Nakajima NK9L-L Homare 24-Ru turbocharged engine. The Hitachi 92 turbocharger was fitted with the aim of improving high altitude performance; target speed was 345 kn (639 km/h; 397 mph) at 8,500 m (27,900 ft). One prototype (コ–C6T1) was converted from a regular C6N1 in February 1945 and first flew in July of that year. The installation of an oil cooler and an intercooler necessitated a sizable cowling to be installed beneath the engine.

C6N3 Test production Saiun Kai 1 (試製彩雲改1, Shisei Saiun Kai 1)

Proposed high-altitude night fighter version of the C6N2. Dual 20 mm cannons were installed. Only a project.

C6N4 Test production Saiun Kai 2 (試製彩雲改2, Shisei Saiun Kai 2)

Fitted 2,200-hp Mitsubishi MK9A Ha 43-11 Ru turbocharged engine, one prototype was converted from C6N1, incomplete.

C6N5 Test production Saiun Kai 3 (試製彩雲改3, Shisei Saiun Kai 3)

Proposed torpedo bomber version. Only a project.

C6N6 Test production Saiun Kai 4 (試製彩雲改4, Shisei Saiun Kai 4)

Wooden aircraft model. Only a project.

Operators

Japan

• Imperial Japanese Navy Air Service

• Naval Air Group
  • Yokosuka Kōkūtai
  • 121st Kōkūtai
  • 131st Kōkūtai
  • 132nd Kōkūtai
  • 141st Kōkūtai
  • 171st Kōkūtai
  • 210th Kōkūtai
  • 302nd Kōkūtai
  • 343rd Kōkūtai
  • 701st Kōkūtai
  • 723rd Kōkūtai
  • 752nd Kōkūtai
  • 762nd Kōkūtai
  • 801st Kōkūtai
  • 1001st Kōkūtai
• Aerial Squadron
  • Reconnaissance 3rd Hikōtai
  • Reconnaissance 4th Hikōtai
  • Reconnaissance 11th Hikōtai
  • Reconnaissance 12th Hikōtai
  • Reconnaissance 102nd Hikōtai
• Kamikaze
  • 1st Mitate Special Attack Group (picked from 752nd Kōkūtai)
  • Sairyū Unit (picked from 752nd Kōkūtai, no sorties)
  • Saiun Unit (picked from 723rd Kōkūtai, no sorties)

Specifications (C6N1)

Data from Japanese Aircraft of the Pacific War

General characteristics

• Crew: 3
• Length: 11 m (36 ft 1 in)
• Wingspan: 12.5 m (41 ft 0 in)
• Height: 3.96 m (13 ft 0 in)
• Wing area: 25.5 m² (274 sq ft)
• Airfoil: root: K151 ; tip: K159
• Empty weight: 2,968 kg (6,543 lb)
• Gross weight: 4,500 kg (9,921 lb)
• Max takeoff weight: 5,260 kg (11,596 lb)
• Powerplant: 1 × Nakajima NK9B Homare 11 18-cylinder air-cooled radial piston engine, 1,485 kW (1,991 hp)
• Propellers: 3-bladed

Performance

• Maximum speed: 610 km/h (380 mph, 330 kn) at 6,100 m (20,000 ft)
• Cruise speed: 390 km/h (240 mph, 210 kn)
• Ferry range: 5,300 km (3,300 mi, 2,900 nmi) (with auxiliary fuel)
• Service ceiling: 10,470 m (34,350 ft)
• Time to altitude: 6,000 m (19,700 ft) in 8 min 9 sec
• Wing loading: 176 kg/m² (36 lb/sq ft)
• Power/mass: 0.33 kW/kg (0.20 hp/lb)

Armament

• Guns: 1× flexibly mounted rearward-firing 7.92 mm Type 1 machine gun

See also

Aircraft of comparable role, configuration and era

• Mitsubishi Ki-46

Related lists

• List of aircraft of World War II
• List of military aircraft of Japan

Bibliography

• Francillon, René J. Japanese Aircraft of the Pacific War. London: Putnam & Company Ltd., 1970. ISBN:0-370-00033-1 (2nd edition 1979, ISBN:0-370-30251-6).
• Francillon, René J. Japanese Carrier Air Groups, 1941–45. London; Osprey Publishing Ltd., 1979. ISBN:0-85045-295-3.
• Huggins, Mark (January–February 2004). "Hunters over Tokyo: The JNAF's Air Defence of Japan 1944–1945". Air Enthusiast (109): 66–71. ISSN 0143-5450. 
• Mondey, David. The Concise Guide to Axis Aircraft of World War II. London: Chancellor Press, 1996. ISBN:1-85152-966-7.
• (in ja) 彩雲・零水偵, Mechanic of World Aircraft, 3, Koujinsha, 1993-03-14, ISBN 4-7698-0633-7 

Further reading

• Famous Airplanes of the World No. 108 Carrier Reconnaissance Plane "Saiun", Bunrindō (Japan), 2005. ISBN:4-89319-119-5.
• The Maru Mechanic No. 15 Nakajima C6N1 Carrier Based Rec. Saiun, Ushio Shobō (Japan), 1979.
• Model Art, No. 458, Special issue Imperial Japanese Navy Air Force Suicide Attack Unit "Kamikaze", Model Art Co. Ltd. (Japan) 1995.
• Kazuhiko Osuo, Kamikaze, Kōjinsha (Japan), 2005. ISBN:4-7698-1226-4. (This book is same as Model Art No. 458.)

External links

• Joao Paulo Julião Matsuura (1997). "Nakajima C6N Saiun (Painted Cloud)". WWII Imperial Japanese Naval Aviation Page. CombinedFleet.com. http://www.combinedfleet.com/ijna/c6n.htm.