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The Aichi D3A, (Allied reporting name "Val")〔Note: This code name was applied mid-to-late 1943; more often the D3A was referred to as the "Type 99 navy dive bomber" by Allied forces.〕 was a World War II carrier-borne dive bomber. It was the primary dive bomber of the Imperial Japanese Navy (IJN), and participated 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,〔Angelucci and Matricardi 1978, p. 142.〕〔Worth 2001, p. 170.〕〔Casey 1977, p. 87.〕 despite being considered obsolescent when the war started. ==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 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 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.〔Francillon 1979, p. 272.〕 The aircraft was to be powered by the 529 kW (710 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 kn (370 km/h), and the Navy was already asking for a faster diving speed of 240 kn (440 km/h).〔Francillon 1979, pp. 272–273.〕 The second aircraft was extensively modified prior to delivery to try to address the problems. Power was increased by replacing the Hikari with the 626 kW (840 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.〔Francillon 1969, p. 24.〕 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Aichi D3A」の詳細全文を読む スポンサード リンク
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