Aichi D3A

The Aichi D3A (known as Val to the Allies) 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.

In the summer of 1936 the Japanese Navy issued the 11-Shi specification for a monoplane carrier-based dive-bomber to replace the existing D1A biplanes currently in service. Aichi, Nakajima[?] and Mitsubishi all submitted designs, and Aichi and Nakajima were both asked for two prototypes each.

The Aichi design started with low-mounted eliptical wings inspired by the Heinkel He 70[?] Blitz. The fuselage looked quite similar to the Zero, although the entire plane was built much studier to withstand the rigours of dive bombing. It flew slow 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 710hp Nakajima Hikari 1 nine cylinder radial.

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 200kts, and the Navy was already asking for a faster diving speed of 240kts.

The second aircraft was extensively modified prior to delivery to try to address the problems. Power was increased by replacing the Hikari with the 840hp 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. The production models featured slightly smaller wings and increased power in the form of the 1,000hp Kinsei 43 or 1,070hp Kinsei 44. The directional instability problem was finally cured with the fitting of a long dorsal fin, and the aircraft actually became highly maneuverable.

Armament was two forward-firing 7.7mm Type 97 machine-guns, and one flexible 7.7mm Type 92 machine gun in the rear cockpit for defense. Normal bombload was a single 250kg (551lb) bomb carried under the fuselage, which was swung out under the prop on release by a trapeze. Two additional 60kg (132lb) bombs could be carried on wing racks located under each wing outboard of the dive brakes.

Starting with the attack on Pearl Harbour, the D3A1 took part in all major Japanese carrier operations in the first ten months of the war. They achieved fame during the campaign in the Indian Ocean when the D3A1s scored with over 80% of their bombs during attacks on the cruisers HMS Cornwall and HMS Dorsetshire and the carrier HMS Hermes. In some cases they were pressed into duty as fighters, their manuverability being enough to allow them to survive in this role.

In June 1942, an improved version of the D3A powered by a 1,300hp 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 237 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 the autumn of 1942, and most Model 11's 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 D3A2's 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.