Aichi B7A Ryūsei

The Aichi B7A (Allied reporting name "Grace"), was a large carrier-borne torpedo-dive bomber designed and produced by Japanese aircraft manufacturer Aichi Kokuki. It was operated by the Imperial Japanese Navy Air Service (IJNAS) during the Second World War.

Designed to replace the Yokosuka D4Y dive bomber and the Nakajima B6N torpedo bomber, work began on developing the B7A in 1941, just prior to the start of the Pacific War. The B7A was furnished with dive brakes and a folding wing, while power was provided by a single Nakajima NK9C Homare 12 18-cylinder radial engine. Armaments were stowed both in an internal bomb bay and on external attachment points, permitting the carriage of munitions such as the Type 91 torpedo, while the defensive weapons comprised a pair of cannons and a single flexibly-mounted machine gun. In spite of its size and weight, the B7A was a relatively fast and agile aircraft. In May 1942, the prototype B7A performed its maiden flight; while engine-related difficulties delayed quantity production of the type, the aircraft demonstrated strong performance in both handling and speed once fitted with an appropriate powerplant.

By the time the B7A entered service in late 1944, Japan's military circumstances had declined substantially. Specifically, there was a shortage of suitably-equipped aircraft carriers (most of the IJN's carriers lacked the appropriate arresting gear), especially after the losses of Taihō and the Shinano in 1944, which meant that the type would operate primarily from land bases instead. Furthermore, the B7A was only produced in only small numbers, in part due to the destruction of Aichi's facility in Funakata. Thus, it had relatively little chance to distinguish itself in combat prior to the Surrender of Japan in August 1945.

Design and development The B7A Ryūsei (Internally designated AM-23 by Aichi)Francillon 1979, p. 289. was designed in response to a 1941 16-Shi requirement issued by the Imperial Japanese Navy Air Service (IJNAS) for a carrier attack bomber that would replace both the Nakajima B6N Tenzan torpedo plane and the Yokosuka D4Y Suisei dive bomber in IJNAS service. It was intended for use aboard a new generation of Taihō-class carriers, the first of which was laid down in July 1941. Because the deck elevators on the Taihōs had a larger square area than those of older Japanese carriers, the longstanding maximum limit of on carrier aircraft length could now be lifted.Francillon 1979, p. 288. A key objective of the requirement was to extend the reach of Japanese carrier-borne attack aircraft, which was reasoned to increase the survivability of the IJN's carriers as a result of being able to maintain greater distance from enemy forces.Friedman 2013, p. 26.

The B7A featured all-metal construction, save for the fabric coverings of the flight control surfaces. Chief Engineer Toshio Ozaki opted for a mid-wing arrangement for the B7A to provide for an internal bomb bay and to ensure enough clearance for the aircraft's four-bladed propeller. This in turn necessitated the adoption of an inverted gull wing, similar to the F4U Corsair, in order to shorten the length of the main landing gear. This wing featured extendable ailerons with a ten-degree range of deflection, enabling them to act as auxiliary flaps. Furthermore, dive brakes were fitted underneath just outboard of the fuselage. The outer portion of the wings could be hydraulically folded upwards for more compact stowage onboard ship, reducing its overall span from to approximately .

Selection of a powerplant was dictated by the Imperial Japanese Navy (IJN), which requested that Aichi design the aircraft around the 1,360 kW (1,825 hp) Nakajima NK9C Homare 12 18-cylinder two-row air-cooled radial engine. This powerplant was expected to become the IJN's standard aircraft engine in the 1,340 kW (1,800 hp) to 1,641 kW (2,200 hp) range. One production model B7A2 was later fitted with a 1,491 kW (2,000 hp) Nakajima Homare 23 radial engine and plans were also made to fit the 1,641 kW (2,200 hp) Mitsubishi MK9 radial to an advanced version of the Ryūsei (designated B7A3 Ryūsei Kai) but the latter effort never came to fruition.Francillon 1979, pp. 290-291.

The B7A had a weight-carrying capacity stemming from its requirements, resulting in a weapons load no greater than its predecessors. The presence of an internal bomb bay with two high-load-capability attachment points allowed the aircraft to carry two 250 kg (550 lb) or six 60 kg (132 lb) bombs. Alternatively, it could carry a single externally mounted Type 91 torpedo, weighing up to 848 kg (1,870 lb). The aircraft's defensive armament initially consisted of a pair of 20 mm Type 99 Model 2 cannons in the wing roots and a single flexibly-mounted 7.92 mm Type 1 machine gun mounted in the rear cockpit. Later production models of the B7A2 featured a 13 mm Type 2 machine gun in place of the 7.92 mm gun.Francillon 1979, p. 291.

Despite the aircraft 's weight and size, it displayed fighter-like handling and performance, beating the version of the A6M Zero in service at the time. For the era, the B7A was both relatively fast and highly manoeuvrable.Gunston 1985, p. 26.

Given the codename "Grace" by the Allies, the prototype B7A performed its maiden flight in May 1942, but teething problems with the experimental NK9C Homare engine and necessary modifications to the airframe meant that the type did not enter into production until two years later in May 1944.Francillon 1979, pp. 289-290. Despite being easier to produce than the Yokosuka D4Y, which Aichi had produced numerous of, the manufacturing rate of the B7A was relatively slow.Francillon 1979, p. 290. Nine prototype B7A1s were built and 80 production version B7A2s completed by Aichi before a severe earthquake in May 1945 destroyed the factory at Funakata where they were being assembled. A further 25 examples were produced at the 21st Naval Air Arsenal at Ōmura.Mondey 1984, p. 8.

Operational history In June 1944, was the only IJN aircraft carrier then suitably equipped to operate the B7A Ryūsei in its intended role. Other Japanese carriers lacked the modern arresting gear necessary to assist the recovery of aircraft weighing over . However, Taiho was sunk during the Battle of the Philippine Sea before enough B7As were even available to embark.Ahlberg & Lengerer 2008, pp. 91-93. Imperial Japan only completed one other carrier capable of operating the B7A, , which was sunk by the Balao-class submarine on 29 November 1944, just ten days after being commissioned.Garzke & Dulin 1985, p. 78.Blair 2001, pp. 779–780.

As a consequence of these carrier losses, the B7A was relegated to operating from various land bases, being primarily flown by the Yokosuka and 752nd Air Groups.

Variants B7A1 One prototype and eight supplementary prototypes. B7A2 Two-seat torpedo-dive bomber aircraft for the Imperial Japanese Navy; 105 built.Matsuura 1997 Aichi B7A Ryusei (Shooting Star) retrieved: 16 September 2010. B7A2 Experimental One aircraft fitted with a 1,491 kW (2,000 hp) Nakajima Homare 23 radial engine. B7A3 Proposed version with a 1641 kW (2,200 hp) Mitsubishi MK9A (Ha-43). Not built.

Number built According to Model Art (2000), p. 72. Funakata Factory, Aichi Kokuki, Nagoya, work number 3201-3289. January February March April May June July August September October November December Sub total 1942 1 1 1943 0 0 0 1 0 1 1 1 1 0 1 0 6 1944 1 1 0 0 1 0 1 1 2 5 5 9 26 1945 7 12 11 13 8 3 2 0 56 21st Naval Air Arsenal, Imperial Japanese Navy, Ōmura, work number 1-25. January February March April May June July August September October November December Sub total 1944 1 0 1 0 1 4 1 0 0 8 1945 2 1 3 2 4 0 4 1 17

Operators

Imperial Japanese Navy Air Service Yokosuka Naval Air Group 131st Naval Air Group 752nd Naval Air Group 1001st Naval Air Group 5th Attack Squadron, a part of 131st/752nd Naval Air Group

Specifications (B7A2)

Aichi B7A Ryūsei

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