Aviation of World War II

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  • Long-Range Bomber
  • First flight: 1933
  • Hiro

International conferences on limiting the tonnage of warships of the main classes, held in Washington in 1922 and London in 1930, brought Japan into the number of outsiders compared to the United States and Great Britain. This in no way suited the Japanese leadership, whose ambitious plans stretched very far and the strike power of the fleet played the first violin in these plans. It was at this time that the Japanese military, perhaps the first in the world, began to consider aviation as an alternative to the warships of the fleet. Where, in addition to carrier-based aviation, it was supposed to have heavy basic attack aircraft.

In 1932, the technical department of the newly created Naval Aviation Department - Kaigun Koku Hombu - was headed by shosho (rear admiral) Yamamoto Isoroku, the future commander of the Combined Fleet. The overall direction of the Kaigun Koku Hombu was carried out by Chosho (Vice Admiral) Shigeru Matsuyama. It was he who singled out the naval base bomber in a separate class of vehicles - in Japanese terminology "Rikujo Kogeki-ki" - the base attack aircraft, in literal translation, or abbreviated as "Rikko". This type of combat aircraft was conceived as a multi-seat, multi-engine vehicle capable of attacking potential enemy warships with torpedoes or bombs far out to sea far from its bases, and also be able to air support its own fleet in combat with the enemy fleet. At the same time, the “Rikko” class of naval base attack aircraft was divided into two more subclasses - “sea attack torpedo bombers” (kogeki-ki), whose main function was a torpedo attack on enemy ships (although bombing attacks were not excluded) and a separate type of “clean” bomber (bakugeki-ki), armed only with bombs.

It was the creation of the last subclass of machines that was decided to be included in the first place in the 7-Shi specification developed in 1932 for a number of naval aircraft. The task for the "naval bomber-attack aircraft" provided for the creation of an aircraft capable of flying 2 thousand nautical miles with two tons of bombs. Due to the great remoteness of the operation of the new machine from its bases, it had to have powerful defensive weapons. Dynamic parameters were not specified.

It was decided to entrust the development of the project to the 11th arsenal of the Hiro fleet, which had the greatest experience in creating multi-engine all-metal flying boats. The project was led by the chief designer of the arsenal shosa (lieutenant commander) Jun Okamura. In view of the particular importance of the task, Okamura's design team was given an assistant from the technical department of Kaigun Koku Hombu chusa (captain of the 3rd rank) Misao Wada, who, although formally subordinate to Okamura, but having a higher rank, was more of a supervisory body and permanent interference in the creative process of the team, rather interfered with it. Looking ahead, it is useful to note that Misao Wada, already being rear admiral and head of the technical department of Kaigun Koku Hombu, trivially "hacked" the project of a 4-engine attack aircraft proposed by Mitsubishi, insisting on an illiterate and unmotivated decision to build a 2-engine basic long-range bomber - the future "Batty" G4M, sacrificing the survivability of the machine.

The design of the new aircraft received the designation "Hirosho 7-Shi Special Attack Aircraft" or the short name G2H1. The design used a thick wing of high elongation with a diagonal power set, developed by the German engineer Wagner. The fuselage is monocoque. Twin keels with rudders repeated the previous design of the company's flying boat Type 90-1 (H3H1). The wing was equipped with "double" Junkers ailerons. The two upper and lower turrets, retractable in flight, looked innovative, which also suggested the German influence of Junkers on the Japanese design. Later, the same turrets were used on the first modifications of the later Japanese project "sea attack aircraft" 96-Rikko G3M.

The powerplant of the aircraft consisted of a pair of new 18-cylinder Hiro Type 94 water-cooled W-engines with a take-off power of 1180 hp. at a nominal of about 900 hp, driving wooden 4-blade fixed-pitch propellers. I must say that the Type 94 engines, being Hiro's own development of the 11th Arsenal, were an attempt to scale the previous project of the 12-cylinder Type 90/91 - a licensed copy of the French Lorraine-Dietrich model 12 and became the nail in the coffin of the entire project. The hope that a much more powerful power plant with a twin-engine layout could correspond to the parameters of a 3 or even 4-engine aircraft did not materialize. It was not possible to achieve reliable operation of these motors, and they were not used anywhere else except on the G2H.

The first prototype of the G2H1 bomber was ready on April 29, 1933 and was delivered by ship to a test airfield in the 1st Arsenal of the Yokosuka Fleet. The aircraft made an impression with its dimensions, in no way inferior to the later 4-engine American B-17, and even surpassed it in wingspan.

In mid-May 1933, in the presence of his "godfather" Rear Admiral Yamamoto, the new bomber took to the air for the first time. Pilots of the Yokosuka Experimental Group kokutai - shosa (lieutenant commander) Shinnosuke Muneyuki and Toshihiko Odahara were sitting at the helm. After takeoff, the pilots made one pass over the spectators gathered on the airfield before proceeding to Kasumigaura Air Base, where they landed safely.

In the process of continuing flight tests of the first prototype, which was joined by the second at the end of 1933, obvious problems were also revealed. Among them were tail vibration, insufficient rigidity of the fuselage power pack, aileron flutter, and constant engine failures. At the beginning of 1934, one of the prototypes of the aircraft was lost during the next test flight. Due to the destruction of the tail in flight, a huge plane crashed into Tokyo Bay, none of the crew survived. After the disaster, the remaining prototype was sent for revision in order to eliminate the identified problems. After changes were made to the design of the airframe, the tests were continued. The vibration of the plumage was eliminated, but problems with the engines continued. The tests went on throughout 1935, when, finally, in July 1936, the fleet did not decide to accept the aircraft into service under the designation "Basic attack aircraft of the fleet Type 95". By that time, the aircraft, while still the largest naval aircraft in Japan, was already conceptually obsolete. The development of aviation in the second half of the 30s was very fast and the Japanese giant, with its angular shape, fixed landing gear and thick wing, obviously could not compete with its peers. Moreover, by that time, the tests of the new "basic attack aircraft of the fleet" Mitsubishi Type 96 - the future G3M1 "Nell", which in the end was given preference to the fleet, were quite successfully completed. Nevertheless, it was decided to release an initial batch of Hiro G2H bombers. Only six copies of this machine were built at the Hiro arsenal, including a modified surviving prototype, after which production was transferred to the Mitsubishi serial plant, where two more copies were made. But soon the fleet finally made a choice in favor of the smaller, but much faster and more versatile Mitsubishi Type 96 G3M1 bomber, and the huge G2H was discontinued.

Taking into account the rather complex designation system adopted in Japanese naval aviation, for the two "basic attack aircraft of the fleet" Type 96 of the Mitsubishi company and Type 95 of the Hiro arsenal, which entered service almost simultaneously, the Japanese, in order to avoid confusion, decided ... to complicate the situation even more and introduced semi-official the designations for the G3M are "Type 96 Chu-Ko" (Chu-Ko) - "medium fleet attack aircraft", and for the G2H - "Type 95 Dai-ko" (Dai-Ko) - "heavy attack aircraft of the fleet. Often they were simply designated " Chu-Ko" and "Dai-Ko". True, after the short career of the G2H bomber ended, these designations were abolished and all subsequent "base fleet attack aircraft" were designated Rikko ("Rikko") with a numerical prefix indicating the year of adoption "from the founding of the Empire."

Hiro G2H1
Crew 6-7
Wing span, m 31.68
Wing area, m² 140.00
Length, m 20.15
Height, m 6.28
2 × PE Type 94 W-18, power, hp 2 × 1,180
Weights, kg
Empty weight 7567
Gross weight 11,000
Maximum speed, km/h 245
Cruise speed, km/h 215
Servie ceiling, m 5,130
Service range, км 1,567

Armament. Five 7.7 mm machine guns, including two on the turret in the forward fuselage, two on the turret in the upper fuselage and one on the turret in the lower fuselage.

Bomb load: up to six 250-kg bombs or four 400-kg bombs on the ventral suspension.

Photo Description
Drawing G2H1

Drawing G2H1


Combat use. All eight G2H1 bombers produced were sent to the Kisarazu kokutai, with the first of them accepted on April 1st, 1936, even before official adoption. But obsolete aircraft were used in Kisarazu Ku only as training in the second line for training crews in long flights over the ocean.

An acute shortage of aircraft during the 2nd China Incident, which began in August 1937, forced the Japanese fleet to use everything that was available. Eight "heavy attack aircraft" G2H from "Kisarazu" kokutai did not go unnoticed. In the second half of August, all eight aircraft flew from the Japanese Islands to the airfield of Saishuto Island (now Jeju-Do) on the southern coast of South Korea. During the flight, one of the bombers, for unknown reasons, lagged behind the group and crashed near the coast of Sagami Bay, southwest of Tokyo. The remaining seven aircraft safely reached the place of deployment and became part of the temporarily formed 1st joint kokutai (regiment), while continuing to be listed as part of Kisarazu Ku.

The first sortie on a combat mission "heavy attack aircraft" Type 95 G2H made September 30, 1937, flying in full force to the Shanghai area. A group of seven aircraft was led by Taiyi (Senior Lieutenant Morokazu Mihara). During the first half of October, a group of seven G2H1s conducted nine sorties in the Shanghai area, successfully avoiding interception by Chinese fighters. Although several aircraft were damaged by anti-aircraft fire, none one bomber was not lost.

However, in preparation for the next sortie on October 24, 1937, an engine caught fire on one of the G2Hs during launch. The flames quickly engulfed the fueled and armed vehicle, followed by an explosion of fuel and ammunition - no more, no less - three 250-kg, five 60-kg and five 50-kg bombs. Neighboring cars blazed along the chain. Within a few minutes, four bombers were destroyed, and the fifth was badly damaged beyond repair. The surviving two bombers were withdrawn from the combat area. Until the end of 1937, they were still listed as part of Kisarazu Ku., but then their traces are lost.

The Type 95 G2H1 "Heavy Basic Fleet Attack Aircraft" was the latest design of the 11th Hirosho Fleet Arsenal. Soon, all design work was transferred to the 1st arsenal of the Kugisho fleet, better known (albeit incorrectly) as the Yokosuka firm.

© Evgeny Aranov


  • Pre-war base bombers of the Japanese fleet /Andrey Firsov/
  • Japanese aviation. /Aerospace Publishing/