World War 2 In Review

Aichi B7A.

The Aichi B7A Ryusei (Shooting Star, Allied reporting name Grace) was a large and powerful carrier-borne torpedo-dive bomber produced by Aichi Kokuki KK for the Imperial Japanese Navy Air Service during the Second World War. Built in only small numbers and deprived of the aircraft carriers it was intended to operate from, the type had little chance to distinguish itself in combat before the war ended in August 1945.

General Information

Type: Torpedo bomber and Dive bomber

National origin: Japan

Manufacturer:

Aichi Kokuki

21st Naval Air Arsenal

Primary user: Imperial Japanese Navy Air Service

Number built: 114 total

Aichi Kokuki K.K. at Funakata:

9 B7A1 prototypes (May 1942-Feb 1944)

80 B7A2 production aircraft (May 1944-July 1945)

Dai-Nijuichi Kaigun Kokusho at Omara (Sasebo):

25 B7A2 production aircraft (Apr 1944-Aug 1945)

Manufactured: 1942–1945

First flight: May 1942

Retired: September 1945

Design and Development

The B7A Ryusei (originally designated AM-23 by Aichi) was designed in response to a 1941 16-Shi requirement issued by the Imperial Japanese Navy Air Service for a carrier attack bomber that would replace both the Nakajima B6N Tenzan torpedo plane and the Yokosuka D4Y Suisei dive bomber in IJN 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 11 m (36 ft) on carrier aircraft length could now be lifted.

Chief Engineer Toshio Ozaki (name often seen as Norio Ozaki, but this is incorrect because the Kanji for both first names are the same and often confused) chose a mid-wing arrangement for the B7A to provide for an internal bomb-bay and to ensure enough clearance for the plane’s 3.5 m (11 ft) four-bladed propeller. This in turn necessitated the adoption of an inverted gull wing, reminiscent of the F4U Corsair, in order to shorten the length of the main landing gear. The wing featured extendable ailerons with a ten-degree range of deflection, enabling them to act as auxiliary flaps. Dive brakes were fitted underneath just outboard of the fuselage. The B7A’s outer wing panels were designed to fold upwards hydraulically for carrier stowage, reducing its overall span from 14.4 m (47 ft) to approximately 7.9 m (26 ft).

Selection of a powerplant was dictated by the Japanese Navy 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 was expected to become the Navy’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 Ryusei (designated B7A3 Ryusei Kai) but the latter effort never came to fruition.

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).

Defensive armament initially consisted of two 20 mm Type 99 Model 2 cannons in the wing roots and one flexible 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.

Despite the plane's weight and size, it displayed fighter-like handling and performance, beating the version of the A6M Zero in service at the time. It was fast and highly maneuverable.

Given the codename "Grace" by the Allies, the B7A first flew as a prototype 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. 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 Omura.

Operational History

In June 1944, IJN Taihō, the only Imperial Japanese Navy aircraft carrier then large enough to operate the B7A Ryusei in its intended role, was sunk during the Battle of the Philippine Sea before enough B7As were even available to embark. Thereafter, the B7A was relegated to operating from land bases, primarily with the Yokosuka and 752nd Air Groups. The Japanese completed only one other carrier capable of operating the B7A, IJN Shinano, but she was sunk by an American submarine in November 1944, just ten days after being commissioned.

Variants

B7A1: Prototypes. Nine built.

B7A2: Two-seat torpedo-dive bomber aircraft for the Imperial Japanese Navy.

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.

Operators

Japan

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

Crew: 2

Length: 11.49 m (37 ft 8.33 in)

Wingspan: 14.40 m (47 ft 3 in)

Height: 4.07 m (13 ft 4.5 in)

Wing area: 35.40 m² (381.041 ft²)

Empty weight: 3,810 kg (8,400 lb)

Loaded weight: 5,625 kg (12,401 lb)

Maximum takeoff weight: 6,500 kg (14,330 lb)

Powerplant: 1 × Nakajima NK9C Homare 12 18-cylinder air-cooled radial engine, 1,360 kW (1,825 hp)

Maximum speed: 567 km/h (306 kn, 352 mph)

Range: 3,038 km (1,888 mi)

Service ceiling: 11,250 m (36,910 ft)

Rate of climb: 9.6 m/s (1,889.8 ft/min)

Wing loading: 158.9 kg/m² (32.5 lb/ft²)

Power/mass: 240 W/kg (0.147 hp/lb)

Guns:

2× 20 mm Type 99 Model 2 cannons in wings

1× 7.92 mm (0.312 in) Type 1

13 mm (0.51 in) Type 2 machine gun in the rear cockpit

Bombs:

800 kg (1,764 lb) of general ordnance

1× 800 kg (1,764 lb) torpedo

Bibliography

Chant, Chris. Aircraft of World War II - 300 of the World's Greatest aircraft 1939-45. Amber Books Ltd., 1999.

Francillon, Ph.D., René J. Japanese Aircraft of the Pacific War. London: Putnam & Company Ltd., 1979.

Gunston, Bill. Military Aviation Library World War II: Japanese & Italian Aircraft. Salamander Books Ltd., 1985.

Millot, Bernard (October 1976). "Aichi B7A "Ryusei" (Grace)". Le Fana de l'Aviation: Le Fanatique de l'Aviation (in French) (83): 26–29.

Mondey, David. Concise Guide to Axis Aircraft of World War II. Temple Press, 1984.

Model Art Special Issue Carrier Attack Bombers of the Imperial Japanese Navy. Model Art Co., Ltd., 2000.

B7A1.

B7A.

A captured Imperial Japanese Navy Aichi B7A2 Ryusei on the ground.

B7A2.

B7A.

B7A captured by the U.S. and test flown in 1946 by the U.S. air intelligence unit ATAIU-SEA. Note the U.S. national insignias.

Another view of the captured B7A undergoing U.S. evaluation.

Aichi B7A2.

B7A2 "Grace" by Ian Robertson (Hasegawa)

B7A2 "Grace".

Aichi B7A2 Japan, September 1945.

Aichi B7A2 Ryusei of Kougeki (Attack) 5th Hikotai, 752nd Kokutai, Katori Naval Air Base, Chiba prefecture, end of Apr 1945. After May 1945 this aircraft operated from Kisarazu Naval Air Base, Chiba prefecture, and was captured by the American forces.