Aichi B7A Ryūsei (jap. 愛知 流星艦上攻撃機, Aichi ryuusei-kanjou-kougeki-ki, tähdenlento, liittoutuneiden raportointinimi Grace) oli Aichi Kōkūkin valmistama kaksipaikkainen torpedo- ja syöksypommittaja, joka palveli keisarillisen Japanin laivaston ilmavoimissa toisessa maailmansodassa.
Ryūsei tarkoitettiin korvaamaan sekä Nakajima B6N Tenzan -torpedopommittaja että Yokosuka D4Y -syöksypommittaja.
Koneen moottorina oli 2 000-hevosvoimainen kaksirivinen Nakajima Homare NK9C -tähtimoottori, jonka kehitysongelmat viivästyttivät koneen käyttöönottoa. Ensilento tapahtui toukokuussa 1942, mutta tuotanto päästiin aloittamaan vasta huhtikuussa 1944. Materiaalipula sekä tuotantolaitosten pommitukset alkoivat jo tuolloin haitata lentokoneiden valmistusta pahoin. Eniten valmistettiin B7A2-tyyppiä, kaikkiaan koneita tuotettiin 105 kappaletta, joista 80 Aichin tehtailla.
Sodan loppuvaiheissa Tyynellämerellä kaikkien Japanin lentotukialusten tultua tuhotuiksi koneet toimivat maatukikohdista.
Aseistuksena oli kaksi kiinteää 20 mm eteenpäin ampuvaa tykkiä, 13 mm konekivääri taka-ampumossa, sekä 800 kg pommikuorma tai torpedo.
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 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.
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.
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)
Max. 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)
Armament: 2 × 20 mm Type 99 Model 2 cannons in wings, 1× 7.92 mm (0.312 in) Type 1 or 13 mm (0.51 in) Type 2 machine gun in the rear cockpit
Bombs: 800 kg (1,764 lb) of general ordnance or 1× 800 kg (1,764 lb) torpedo
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 800 kg (1,764 lb) torpedo mounted externally.
Defensive armament initially consisted of two 20mm Type 99 Model 2 cannons in the wing roots and one flexible 7.92mm Type 1 machine-gun mounted in the rear cockpit. Later production models of the B7A2 featured a 13mm Type 2 machine-gun in place of the 7.92mm gun.
Despite the plane's weight and size, it displayed fighter-like handling and performance, besting 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.
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 relegat 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.