The Aichi D3A Type 99 Carrier Bomber (Allied reporting name "Val") is a World War II carrier-borne dive bomber. It was the primary dive bomber of the Imperial Japanese Navy (IJN) and was involved in almost all IJN actions, including the attack on Pearl Harbor.
The Aichi D3A was the first Japanese aircraft to bomb American targets in the war, commencing with Pearl Harbor and U.S. bases in the Philippines, such as Clark Air Force Base. Vals sank more Allied warships than any other Axis aircraft.
Design and development
In mid-1936, the Japanese Navy issued the 11-Shi specification for a monoplane carrier-based dive bomber to replace the existing D1A biplane then in service. Aichi, Nakajima, and Mitsubishi all submitted designs, with the former two subsequently being asked for two prototypes each.
The Aichi design started with low-mounted elliptical wings inspired by the Heinkel He 70 Blitz. It flew slowly enough that the drag from the landing gear was not a serious issue, so fixed gear was used for simplicity. The aircraft was to be powered by the 529 kW (709 hp) Nakajima Hikari 1 nine-cylinder radial engine.
The first prototype was completed in December 1937, and flight trials began a month later. Initial tests were disappointing. The aircraft was underpowered and suffered from directional instability in wide turns, and in tighter turns it tended to snap roll. The dive brakes vibrated heavily when extended at their design speed of 200 knots (370 km/h), and the Navy was already asking for a faster diving speed of 240 knots (440 km/h).
The second aircraft was extensively modified before delivery to try to address the problems. Power was increased by replacing the Hikari with the 626 kW (839 hp) Mitsubishi Kinsei 3 in a redesigned cowling, and the vertical tail was enlarged to help with the directional instability. The wings were slightly larger in span and the outer sections of the leading edges had wash-out to combat the snap rolls, and strengthened dive brakes were fitted. These changes cured all of the problems except the directional instability, and it was enough for the D3A1 to win over the Nakajima D3N1
In December 1939, the Navy ordered the aircraft as the Navy Type 99 Carrier Bomber Model 11 (kanjō bakugekiki, usually abbreviated to 艦爆 kanbaku.). The production models featured slightly smaller wings and increased power in the form of the 746 kW (1,000 hp) Kinsei 43 or 798 kW (1,070 hp) Kinsei 44. The directional instability problem was finally cured with the fitting of a long dorsal fin-strake which started midway down the rear fuselage, and the aircraft actually became highly maneuverable.
Armament was two forward-firing 7.7 mm (0.303 in) Type 97 machine guns, and one flexible 7.7 mm (.303 in) Type 92 machine gun in the rear cockpit for defense. Normal bombload was a single 250 kg (550 lb) bomb carried under the fuselage, swung out under the propeller on release by a trapeze. Two additional 60 kg (130 lb) bombs could be carried on wing racks located under each wing outboard of the dive brakes.
The D3A1 commenced carrier qualification trials aboard the aircraft carriers Akagi and Kaga during 1940, while a small number of aircraft made their combat debut from land bases over China. Starting with the attack on Pearl Harbor, the D3A1 took part in all major Japanese carrier operations in the first 10 months of the war. They achieved their first major success against the Royal Navy during their Indian Ocean raid in April 1942. Val dive bombers scored over 80% hits with their bombs during attacks on two heavy cruisers and an aircraft carrier during the operation. During the course of the war, Val dive bombers often combined their attacks upon enemy warships with the IJN Nakajima B5N Kate torpedo bomber; consequently enemy vessels were often sunk by a combination strike of bombs and torpedoes. However, there were occasions when just the Vals would make the attacks, or at least score the sinking hits. Discounting the Pearl Harbor strike, which also used the B5N for level bombing and torpedo attacks, Val dive bombers were credited with sinking the following Allied warships:
- USS Peary, American destroyer, 19 February 1942 – Australia (Darwin)
- USS Pope, American destroyer, 1 March 1942 – Pacific Ocean
- USS Edsall, American destroyer, 1 March 1942- Pacific Ocean
- USS Pecos, American oiler, 1 March 1942- Pacific Ocean
- HMS Cornwall, British heavy cruiser, 5 April 1942 – Indian Ocean
- HMS Dorsetshire, British heavy cruiser, 5 April 1942 – Indian Ocean
- HMS Hector, British armed merchant cruiser, 5 April 1942 – Indian Ocean
- HMS Tenedos, British destroyer, 5 April 1942 – Indian Ocean
- HMS Hermes, British aircraft carrier, 9 April 1942 – Indian Ocean
- HMAS Vampire, Australian destroyer, 9 April 1942 – Indian Ocean
- USS Sims, American destroyer, 7 May 1942 – Pacific Ocean
- USS De Haven, American destroyer, 1 February 1943 – Pacific Ocean
- USS Aaron Ward, American destroyer, 7 April 1943 – Pacific Ocean
- USS Brownson, American destroyer, 26 December 1943 – Pacific Ocean
- USS Abner Read, American destroyer, sunk by kamikaze 1 November 1944 – Pacific Ocean
- USS William D. Porter, American destroyer, sunk by kamikaze 10 June 1945 – Japan (Okinawa)
As the war progressed, there were instances when the dive bombers were pressed into duty as fighters in the interceptor role, their maneuverability being enough to allow them to survive in this role. In June 1942, an improved version of the D3A powered by a 969 kW (1,299 hp) Kinsei 54 was tested as the Model 12. The extra power reduced range, so the design was further modified with additional fuel tanks to bring the total tankage to 900 L (240 US gal), giving it the range needed to fight effectively over the Solomon Islands. Known to the Navy as the Model 22, it began to replace the Model 11 in front-line units in autumn 1942, and most Model 11s were then sent to training units.
When the Yokosuka D4Y Suisei became available, the D3A2s ended up with land-based units or operating from the smaller carriers, which were too small to handle the fast-landing Suisei. When American forces recaptured the Philippines in 1944, land-based D3A2s took part in the fighting, but were hopelessly outdated and losses were heavy. By then, many D3A1s and D3A2s were operated by training units in Japan, and several were modified with dual controls as Navy Type 99 Bomber Trainer Model 12s (D3A2-K). During the last year of the war, the D3A2s were pressed back into combat for kamikaze missions.