Warplanes of Japan: Aichi B7A Ryusei

Aichi B7A Ryusei

(IJNAF Photo)

Aichi B7A2 Ryusei, codenamed "Grace".

The Aichi B7A Ryusei (流星, Ryūsei, "Shooting Star"; Allied reporting name"Grace") was a large and powerful carrier-borne torpedo-dive bomber produced by Aichi Kokuki for the Imperial Japanese Navy Air Service during theSecond 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.

The B7A Ryusei (originally designated AM-23 by Aichi) was designed in responseto a 1941 16-Shi requirement issued by the Imperial Japanese Navy Air Servicefor a carrier attack bomber that would replace both the Nakajima B6N Tenzan torpedo plane and the Yokosuka D4Y Suisei dive bomber in IJN service.[1] It wasintended for use aboard a new generation of Taihō-class carriers, the first ofwhich was laid down in July 1941. Because the deck elevators on the Taihōs hada 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 isincorrect because the Kanji for both first names are the same and oftenconfused) chose a mid-wing arrangement for the B7A to provide for an internalbomb-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 invertedgull wing, similar to the F4U Corsair, in order to shorten the length of themain landing gear. The wing featured extendable ailerons with a ten-degreerange of deflection, enabling them to act as auxiliary flaps. Dive brakes werefitted underneath just outboard of the fuselage. The B7A's outer wing panelswere designed to fold upwards hydraulically for carrier stowage, reducing itsoverall 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 requestedthat Aichi design the aircraft around the 1,360 kW (1,825 hp) Nakajima NK9CHomare 12 18-cylinder two-row air-cooled radial engine. This was expected tobecome the Navy's standard aircraft engine in the 1,340 kW (1,800 hp) to 1,641kW (2,200 hp) range.[1] One production model B7A2 was later fitted with a 1,491kW (2,000 hp) Nakajima Homare 23 radial engine and plans were also made to fitthe 1,641 kW (2,200 hp) Mitsubishi MK9 radial to an advanced version of theRyusei (designated B7A3 Ryusei Kai) but the latter effort never came tofruition.

The B7A had a weight-carrying capacity stemming from its requirements,[3] resultingin a weapons load no greater than its predecessors. The presence of an internalbomb bay with two high-load-capability attachment points allowed the aircraftto carry two 250 kg (550 lb) or six 60 kg (132 lb) bombs. Alternatively, itcould carry a single externally mounted Type 91 torpedo, weighing up to 848 kg(1,870 lb).[4]

Defensive armament initially consisted of two 20mm Type 99 Model 2 cannons inthe wing roots and one flexible 7.92mm Type 1 machine-gun mounted in the rearcockpit. Later production models of the B7A2 featured a 13mm Type 2 machine-gunin place of the 7.92mm gun.

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

Given the codename "Grace" by the Allies, the B7A first flew as aprototype in May 1942, but teething problems with the experimental NK9C Homareengine and necessary modifications to the airframe meant that the type did notenter into production until two years later in May 1944. Nine prototype B7A1swere built and 80 production version B7A2s completed by Aichi before a severeearthquake in May 1945 destroyed the factory at Funakata where they were beingassembled. A further 25 examples were produced at the 21st Naval Air Arsenal atOmura.

Operational history
In June 1944, the Taihō was the only Imperial Japanese Navy aircraft carrierthen modern enough to operate the B7A Ryusei in its intended role. OtherJapanese carriers lacked the modern arresting gear necessary to assist therecovery of aircraft weighing over 4000 kg. However, Taiho was sunk during theBattle of the Philippine Sea before enough B7As were even available to embark.Afterward, the B7A was relegated to operating from land bases, primarily withthe Yokosuka and 752nd Air Groups.[1] The Japanese completed only one othercarrier capable of operating the B7A, the Shinano, which was sunk byBalao-class submarine Archerfish in November 1944, just ten days after beingcommissioned.

Variants
B7A1
One prototype and eight supplementary prototypes.
B7A2
Two-seat torpedo-dive bomber aircraft for the Imperial Japanese Navy; 105built.
B7A2 Experimental
One aircraft fitted with a 1,491 kW (2,000 hp) Nakajima Homare 23 radialengine.
B7A3
Proposed version with a 1641 kW (2,200 hp) Mitsubishi MK9A (Ha-43). Not built.(Wikipedia)

(IJNAF Photos)

Aichi B7A2 Ryusei, codenamed "Grace".

(USAAF Photos)

Aichi B7A2 Ryusei, codenamed "Grace", (Serial No. 816) captured by the US and test flown in 1946 by the US air intelligence unit ATAIU-SEA.  Shipped to the USA it is shown here in USN markings, No. 52, USAAF FE-1204, currently in storage in the Paul E. Garber facility, Suitland, Maryland.  Aichi B7A2, USAAF FE-1206 was scrapped at Middletown, Pennsylvania.

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