The Nakajima G8N Renzan (Mountain Range) was a four engined long range bomber designed from 1943 and that only reached the prototype stage before the end of the Second World War. Many of the Japanese Navy's successes in 1941-42 had been won with the aid of very long range fighters and bombers that could appear where they weren’t expected, while the Army often operated over very long ranges in China. As a result both services had issued specifications for replacement aircraft, but neither the Mitsubishi G7M nor the Kawanishi Ki-100 really lived up to expectations.
The Navy's response was to issue an 18-Shi specification for a four-engined attack bomber, the G8N1 Renzan (Mountain Range). The new aircraft was to have a top speed of 368mph, a range of 2,300 miles with a full bomb load and 4,605 miles with a reduced load, a full bomb load of 8,816lb and good armour and defensive guns. The speed and range requirements were the same as those for the earlier G7M.
Nakajima responded with a mid-winged aircraft, with tricycle landing gear, and a single vertical tail. It was powered by four Nakajima NK9K-L Homare 24 engines, with Hitachi 92 turbo supercharges, providing 2,000hp each. The engines were given cooling fans. The armour requirements were met by building the aircraft from large thick metal plate, a technique that was hoped would speed production. The aircraft was to be armed with four powered gun turrets (nose, dorsal, ventral and tail) and with two manually operated side guns.
The first prototype made its maiden flight on 23 October 1944, and it was followed by the second, third and fourth aircraft in December 1944, March 1945 and June 1945. The new aircraft performed well, but by the summer of 1945 the war was coming ever closer to Japan, and long range bombers were no longer a high priority. The programme was also badly disrupted by American bombing, while the third prototype was destroyed by marauding naval aircraft. Planned production of the G8N1 was cancelled.
Two more versions of the aircraft were proposed. The G8N2 was to use 2,200hp Mitsubishi MK9A radials, but this was never built. The G8N3 Renzan-Kai Model 23 would have been built from steel instead of the rare light alloys used in the G8N1, but this too was never built.
Engine: Four Nakajima NK9K-L Homare 24 eighteen cylinder air-cooled radial engines
Power: 2,000hp at take off, 1,850hp at 26,245ft
Wing span: 106ft 9in
Length: 75ft 10in
Height: 23ft 7.5in
Empty Weight: 38,360lb
Loaded Weight: 59,084lb
Maximum Weight: 70,879lb
Max Speed: 368mph at 26,245ft
Cruising Speed: 230mph at 13,125ft
Service Ceiling: 33,465ft
Range: 2,452 miles normal, 4,639 maximum
Armament: Four powered turrets - twin 20mm cannon in dorsal, ventral and tail turrets, twin 13mm machine guns in nose. One 13mm machine gun in each beam position
Bomb-load: 2,204lb normal, 8,818lb maximum