Nakajima G8N1 Renzan

In February 1943 the Imperial Navy staff asked Nakajima Aircraft Company to design a four-engined bomber, capable of meeting an earlier specification set for a long-range land-based attack plane. The final specification, issued on 14 September 1943, called for a plane with a maximum speed of 320 knots (590 km/h; 370 mph) able to carry a 4,000 kg (8,800 lb) bomb-load 2,000 nmi (3,700 km; 2,300 mi) or a reduced bomb-load 4,000 nmi (7,400 km; 4,600 mi).

Nakajima’s design featured a mid-mounted wing of small area and high aspect ratio, a tricycle landing gear and a large single-fin rudder. Power came from four 2,000 hp Nakajima NK9K-L “Homare” 24 radial engines with Hitachi 92 turbo superchargers and driving four-bladed propellers. The engines were cooled by counter-rotating fans positioned just inside the engine cowlings. Defensive armament included power-operated nose, dorsal, ventral and tail turrets along with two free-swiveling machine guns at the beam positions.

The initial prototype was completed in October 1944 and delivered to the Navy for testing in January 1945, a year after the Navy ordered development to start. Three further examples were completed by June 1945, with the third prototype being destroyed on the ground by US carrier aircraft.

Other than minor problems with the turbo superchargers, the Renzan performed satisfactorily and the Navy hoped to have a total of 16 prototypes and 48 production-version G8N1s assembled by September 1945. But the worsening war situation and a critical shortage of light aluminium alloys led to the project’s cancellation in June.

After the war, one prototype was taken to the United States and scrapped after testing.

Specifications (G8N1)

General Characteristics

Crew: 10
Length: 22.935 m (75 ft 3 in)
Wingspan: 32.54 m (106 ft 9 in)
Height: 7.2 m (23 ft 7 in)
Wing area: 112 m2 (1,210 sq ft)
Empty weight: 17,400 kg (38,360 lb)
Gross weight: 26,800 kg (59,084 lb)
Max takeoff weight: 32,150 kg (70,879 lb)
Powerplant: 4 × Nakajima NK9K-L Homare 24 18-cylinder air-cooled radial piston engines, 1,500 kW (2,000 hp) each for take-off
1,380 kW (1,850 hp) at 8,000 m (26,247 ft)
Propellers: 4-bladed constant-speed metal propellers

Performance

Maximum speed: 593 km/h (368 mph, 320 kn) at 8,000 m (26,247 ft)
Cruise speed: 370 km/h (230 mph, 200 kn) at 4,000 m (13,123 ft)
Range: 3,945 km (2,451 mi, 2,130 nmi)
Ferry range: 7,464 km (4,638 mi, 4,030 nmi)
Service ceiling: 10,200 m (33,500 ft)
Time to altitude: 8,000 m (26,247 ft) in 17 minutes 34 seconds
Wing loading: 239.3 kg/m2 (49.0 lb/sq ft)
Power/mass: 0.2191 kW/kg (0.1333 hp/lb)

Armament

Guns:
6× 20 mm Type 99 cannon – 2 each in the dorsal, ventral, and tail turrets
*2× 13 mm (.51 in) Type 2 machine guns in nose turret
2× 13 mm (.51 in) Type 2 machine gun in fuselage sides
Bombs:
2x 2,000 kg (4,409 lb) bombs – maximum
4x 250 kg (551 lb) bombs – normal