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G5N Shinzan
Heavy Bomber

G5N Shinzan

G5N Shinzan (Decay) . In the late 1930s, the aviation command of the Imperial Japanese Navy came to the conclusion that it was necessary to have a heavy bomber capable of solving strategic tasks. Realizing this, in 1938 Kaigun Koku Hombu formulated the 13-Si requirements for a new bomber, the flight range of which was to be of the order of 5556-6482 km (3000-3500 nautical miles). The only way to achieve such a range - along with an increased bomb load (2000-4000 kg) compared to the G3M and G4M - was to use a four-engine scheme.However, at that time, none of the Japanese aircraft manufacturers had the experience of building such large aircraft, and this is still more complicated an already very difficult task.

A way out of the situation was found in the USA, where two years earlier, Douglas specialists began working on a large four-engined long-range DC-4E passenger aircraft (not to be confused with the later DC-4 / C-54 Skymaster project) ... This aircraft, which lost in the competition to the Boeing B-307 and was built in a single copy, was bought by the civil airline "Japanese Airlines" by order and for the money of the fleet, allegedly for its own needs. After the assembly of the American aircraft delivered to Japan in disassembled form, it passed flight tests and was secretly transferred to the Nakajima company, which was instructed to develop a bomber project in accordance with the 13-C specification. It was prescribed to use the DC-4E design as a base.

The prototype G5N1, which became the first four-engined aircraft in the Japanese fleet, took off in April 1941. From the "American" he borrowed a wing, engine nacelles, landing gear with a front strut and a number of other, smaller units and assemblies. The fuselage was completely new, narrower than that of the original, with a glazed nose and an extensive bomb bay, as well as a two-keel spaced tail unit.

The all-metal G5N mid-wing was borrowed from the American Douglas DC-4E transport aircraft that served as the prototype. It had an unprecedentedly large span for Japanese cars - more than 42 m.Four new Nakajima NK7A Mamoru 11 radial engines with a capacity of 1870 hp were used as power plants. from.

The G5N's all-metal fuselage was designed from scratch by the Japanese. The aircraft was the first in Japan with a front landing gear.

Defensive armament included two 20-mm Type 99 Model 1 cannons (one each in the dorsal and tail turrets) and four 7.7-mm Type 97 machine guns for the bow, lower and two side rifle mounts.The maximum bomb load was supposed to reach 4000 kg (when flying over long distances - 2000 kg). The crew consisted of seven people.

The flight test results did not meet the customer's expectations. Fully equipped and armed, the Shinzan turned out to be almost 20% heavier than planned, its engines were unreliable, and its characteristics - primarily speed and range - were unsatisfactory. Despite this, three more experimental G5N1s and two modified G5N2s were built with the proven, but even less powerful (1530 hp) Mitsubishi Kasei 12 engines. The lack of power was too obvious, and in the end Kaigun Koku Hombu abandoned plans for further development of the aircraft as a bomber. Two experimental G5N1s were also equipped with Kasei 12 engines and, together with two G5N2s, converted into a transport version, designated "Shinzan KAI Model 12 Transport Aircraft" (G5N2-L Model 12). The firing points were dismantled and the bomb bay was converted into a cargo bay. The crew was reduced to six people.

The G5N2-L aircraft were used as transport aircraft almost until the end of the war. They flew on the routes connecting the Japanese Islands with Hong Kong, Taiwan, the Philippines, about. Tinian and the Mariana Islands. At the turn of 1944-1945, two vehicles were lost.

Despite the fact that the G5N project was unsuccessful, the company "Nakajima" acquired extremely important experience, which was later used in the development of the next four-engined bomber G8N "Renzan".

G8N Renzan

G8N Renzan

G8N Renzan (Mountain Range) . The failure with the G5N Shinzan forced Kaigun Koku Hombu to return to the twin-engine bomber concept for a while. However, by the end of 1943, after analyzing preliminary designs and design parameters, it became clear to both the developers and the customer that the twin-engine aircraft was not able to meet the requirements. This conclusion was predictable, therefore, back in February 1943, Kaigun Koku Hombu handed over to the Nakajima company the preliminary design requirements of the 18-Si for a four-engine long-range bomber. To this, the fleet command was also prompted by reports from the fronts about the high efficiency of the American four-engine B-17 and B-24 bombers. In the final form, the assignment for the development of a new bomber, designated G8N1 "Renzan" (Mountain Range), was issued on September 14, 1943. It provided for the creation of a powerful defensive weapon and a well-protected vehicle that would develop a maximum speed of 592 km / h, climb 8000 m in 20 minutes and had a flight range of 3700 km with a full bomb load (4000 kg) and 7400 km without a load.

On October 23, 1944, the first flight was made by the prototype G8N1, which was an all-metal monoplane, the design of which was simplified as much as possible to facilitate mass production, with a mid-wing, having a laminar profile and high elongation with a relatively small surface area. It was equipped with four turbocharged (Hitachi Type 92) Nakajima Homare 24 radial engines with 2000 hp. everyone.

The all-metal mid-wing G8N had a laminar profile and was characterized by a fairly small surface area (112 m & # 178; compared to 202 m & # 178; for the G5M) with a high aspect ratio. Inside it housed sealed fuel tanks with a total capacity of 13,450 liters. The main landing gear was retracted into the engine nacelles. The morally obsolete tail unit with end washers was replaced by a single keel tail.

An unprecedentedly powerful defensive armament for Japanese aircraft was represented by six 20-mm Type 99 Model 2 cannons (in the dorsal and ventral turrets, as well as in the tail mount) and four 13-mm Type 2 machine guns (twin in the mechanized bow turret and one in the windows on the sides of the fuselage).

In case of successful completion of the tests, it was planned to release 48 production G8N1 bombers by September 1945, including 16 experimental and pre-production vehicles. But in practice, it all boiled down to the construction of three more prototypes, which were completed in October 1944, March and June 1945. This delay was caused by the constant raids of American aircraft and the shortage of light alloys. In addition, the sharply deteriorating strategic situation in Japan forced to change priorities. Now there was no time for strategic bombers and the serial production of the Renzans had to be abandoned.

After the war, the fourth prototype of the G8N1 "Renzan" was transported to the United States, where it was thoroughly tested. The results surprised the Americans. The characteristics demonstrated by the Japanese bomber were much higher than those of the American "classmates" Boeing B-17 and Consolidated B-24 and were only slightly inferior to those of the Boeing B-29 strategic bomber. After the end of hostilities, the allies assigned the codename "Rita" to G8N1.

Crew 7 9
Wing span, m 42.12 32.54
Wing area, m² 201.8 112.0
Length, m 31.02 22.94
Height, m 6.13 7.20
Nakajima engine 4×NK7A «Mamoru-11» 4×NK9K-L «Homare 24»
Power, h.p. 4×1,870 4×2,000
Weight, kg
Empty 20,100 17,400
Gross weight 32,000 32,150
Maximum speed, km/h /m 420/4100 593/8000
Climb time, min / altitude, m 5.38/2000 17.6/8000
Service ceiling, m 7,450 10,200
Service range, km 4,260 3,950
cannon 2×20-mm 6×20-mm
machine guns 4×7,7-мм 4×13-мм
Bomb, kg 4000 4000
Photo Description
Drawing G5N2

Drawing G5N2

Drawing G8N1

Drawing G8N1, (turbocharger at the bottom of the engine)

G5N Shinzan at the Japanese airbase Atsugi, 1945

G5N Shinzan at the Japanese airbase Atsugi, 1945

G5N Shinzan. Cockpit and tail gunner

G5N Shinzan. Cockpit and tail gunner.

G8N Renzan in the USA, 1945

G8N Renzan in the USA, 1945


  • "Encyclopedia of military engineering " /Aerospace Publising/
  • "Japan Warplanes of World War II" /Oleg Doroshkevich/

August 05, 2018
The G5N, which was never put into service, nevertheless received a codename from the allies - "Liz", a feminine name assigned only to bombers. The transport use of prototypes of a heavy bomber is a payback for the low flight characteristics of the aircraft.

April 27, 2018

G8N Renzan is a heavy four-engined bomber that never became a saving super-fortress for the Imperial Japan.
High performance characteristics "Renzan" owes, first of all, to its "laminar" wing with a small area and a power plant with a capacity of 8000 hp.

April 28, 2018

It is interesting to compare with the attempt of the Germans to create their own strategic bomber Me 264 , also an unfulfilled program due to the Allied bombing and end of the war.