The Aichi D3A (99式艦上爆撃機, Allied code name Val) was a World War II dive bomber produced by the Aichi company in Japan. It was the primary carrier-borne dive bomber in the Imperial Japanese Navy in the early stages of the war, and participated in almost all actions, including Pearl Harbor.
The Aichi design started with low-mounted elliptical wings inspired by the Heinkel He 70 Blitz. The fuselage looked quite similar to the Zero, although the entire plane was built stronger to withstand the rigours of dive bombing. It flew slowly enough that the drag from the landing gear was not a serious issue, so fixed gear were used for simplicity. The plane was to be powered by the 710 hp (529 kW) 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 prior to delivery to try to address the problems. Power was increased by replacing the Hikari with the 840 hp (626 kW) 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.
Armament was two forward-firing 7.7 mm Type 97 machine-guns, and one flexible 7.7 mm Type 92 machine gun in the rear cockpit for defense. Normal bombload was a single 250 kg (550 lb) bomb carried under the fuselage, which was 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.
Starting with the attack on Pearl Harbor, the D3A1 took part in all major Japanese carrier operations in the first ten months of the war. They achieved fame during the Indian Ocean raid in April 1942 when the D3A1s scored with over 80% of their bombs during attacks on the British cruisers HMS Cornwall and HMS Dorsetshire and the carrier HMS Hermes. In some cases they were pressed into duty as fighters, their maneuverability being enough to allow them to survive in this role.
In June 1942, an improved version of the D3A powered by a 1,300 hp (970 kW) 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 U.S. 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 returned to 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.
In 1945, Indonesian guerillas captured numerous ex-Japanese air bases. Several numbers of D3A Val were captured by Indonesian guerillas, including at Bugis Air Base in Malang (repatriated 18 September 1945). Most of the aircraft were destroyed during 1945-1949 when the former Dutch East Indies and the Netherlands were engaged in military conflict/police action in Indonesia.