|Aichi D3A1 from carrier Akagi.|
|Role||Carrier-based dive bomber|
|Manufacturer||Aichi Kokuki KK|
|First flight||January 1938|
|Primary user||Imperial Japanese Navy|
|Yokosuka D3Y My?jo|
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. They sank more Allied warships than any other Axis aircraft.
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 (kanj? bakugekiki, usually abbreviated to 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.
The pilot position was equipped with a Type 95 telescopic gunsight in the earlier models and a Type 99 in the later models, which were used for aiming the bomb during the dive. The observer/navigator position was equipped with a Type 97 Mk1 drift sight, which was a long vertical tube located in the front-left of the observer's seat. In addition, the observer position was equipped with a drift meter that was mounted on the floor in the front-right of the observer's seat. The observer also operated a Type 96 Mk2 radio set that was mounted in front of the observer's seat and behind the pilot's seat. On top of the radio set was a Type 3 reflector compass for precise navigation.
Armament was two fixed forward-firing 7.7 mm (0.303 in) Type 97 machine guns, and one flexible 7.7 mm (.303 in) Type 92 machine gun at the rear end of cockpit, which was operated by the observer. Normal bomb load was a single 250 kg bomb (e.g., Type 99 No 25 semi-AP or Type 98 No 25 land bomb) carried under the fuselage, swung out under the propeller on release by a trapeze. Two additional 60 kg bombs (e.g., Type 99 No 6 semi-AP or Type 2 No 6 land bomb) could be carried on wing racks located under each wing outboard of the dive brakes.
An individual D3A dive bomber was commanded by the senior ranking crew member aboard, which could be the observer rather than the pilot. This was in contrast to US Navy, where the pilot was almost always the commander of a dive bomber. For example, Petty Officer First Class Kiyoto Furuta was serving as a pilot to Lieutenant Takehiko Chihaya during the Attack on Pearl Harbor, and later on to Lieutenant Keiichi Arima during the two carrier battles of the Solomon Islands campaign, both of whom were observers.
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. D3A1 dive bombers scored over 80% hits with their bombs during attacks on two heavy cruisers and an aircraft carrier during the operation.
Before Indian Ocean raid, the established doctrine regarding attack against ships was to arm all D3A dive bombers with semi-AP bombs. On 5 April 1942, IJN carrier force attacked Colombo on Ceylon with half of its complement, while the other half was kept in reserve for strikes against ships. Since a second strike against Colombo was deemed necessary, the dive bombers of reserve force were rearmed from semi-AP bombs to land bombs. When British heavy cruisers were spotted soon afterwards, the reserve force was sent with a portion of D3A dive bombers armed with land bombs. In the subsequent attack, land bombs unintentionally proved very effective in suppressing the anti-aircraft fire from the ships. As a result, the doctrine was modified in order to intentionally equip the first few D3A dive bombers with land bombs. This new method was already implemented for the attack that sunk HMS Hermes just four days later, and continued to be used from then on.
During 1942, dive bombing attacks by D3A bombers significantly contributed to sinking of three US fleet carriers: Lexington at the Battle of the Coral Sea, Yorktown at the Battle of Midway and Hornet at the Battle of the Santa Cruz Islands. In addition, they damaged carrier Enterprise both at the Battle of the Eastern Solomons and at the Battle of the Santa Cruz Islands.
During the course of the war, D3A 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 D3A's 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, D3A dive bombers were credited with sinking the following Allied warships:
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.
One D3A is currently under restoration at the Planes of Fame Museum in Chino, California. There are two unrestored D3As on display at the National Museum of the Pacific War in Fredericksburg, Texas.
Data from Japanese Aircraft of the Pacific War
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