Warplanes of Japan: Aichi D3A

Aichi D3A

(IJNAF Photo)

The Aichi D3A (Navy designation "Type 99 Carrier Bomber"; Allied reporting name "Val") is a Second World War carrier-borne dive bomber. It was the primary dive bomber of theImperial 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 monoplanecarrier-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 theHeinkel He 70 Blitz. It flew slowly enough that the drag from the landing gear was not a serious issue, so the fixed gear was used for simplicity. The aircraft was to be powered by the 529 kW (709 hp) Nakajima Hikari 1nine-cylinder radial engine.

The first prototype was completed in December 1937, and flight trials began amonth later, after which it was designated as D3A1. 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 240knots (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 (839hp) 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 CarrierBomber Model 11 (kanjō bakugekiki, usually abbreviated to 艦爆 kanbaku.[9]). The production models featured slightly smaller wingsand 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.

In June 1942, an improved version of D3A1, powered by a 969 kW (1,299 hp)Kinsei 54, was tested and designated as D3A2 or the Model 12. The extra powerreduced range, so the design was further modified with additional fuel tanks tobring the total tankage to 900 L (240 US gal), giving it the range needed tofight 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, andmost Model 11s were then sent to training units. While some late productionmodels of D3A1 were fitted with a propeller spinner, it became a standard withD3A2.

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 aimingthe bomb during the dive. The observer/navigator position was equipped with aType 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 topof 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 250kg bomb (e.g., Type 99 No 25 semi-AP or Type 98 No 25 land bomb) carried underthe 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.

Initially, D3A dive bombers were painted in silver. During the summer of 1941,the paint finish changed to light olive grey. The color changed again in early 1942 to dark green.

An individual D3A dive bomber was commanded by the senior ranking crew memberaboard, which could be the observer rather than the pilot.[7] This was in contrastto 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 toLieutenant 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 first saw combat operation in November 1939, one month prior to itsofficial acceptance as the Navy Type 99 dive bomber. Nakajima sent several examplesto the 14th Air group operating at Haikou on Hainan island in South China.These D3A1s were commanded by Lieutenant Sadamu Takahashi and supported theImperial Japanese Army in the capture of Nanning, which was intended to cut thesupplies coming from French Indochina. After the capture of Nanning, theycontinued to be operated in the area in 1940. In May 1940, 12th Air Groupbecame the second front-line unit to be equipped with the new D3A1 divebombers. They first participated in the capture of Yichang and conductedanti-shipping operations on Yangtze river, west of Yichang, in order to cut theChinese supplies coming from Chongqing. In September, D3A1 from the 12th AirGroup started to fly missions against Chongqing, which was the Chinese capitalat the time. After the invasion of Indochina in autumn 1940, 14th Air Groupoperated at Hanoi and flew missions against Kunming and Burma Road.

The D3A1 commenced carrier qualification trials aboard the aircraft carriersAkagi and Kaga during 1940, while a small number of aircraft made their combatdebut from land bases over China. Starting with the attack on Pearl Harbor, theD3A1 took part in all major Japanese carrier operations in the first 10 monthsof the war. They achieved their first major success against the Royal Navyduring their Indian Ocean raid in April 1942. D3A1 dive bombers scored over 80%hits[14] with their bombs during attacks on two heavy cruisers and an aircraftcarrier during the operation.

Before the Indian Ocean raid, the established doctrine regarding attacksagainst ships was to arm all D3A1 dive bombers with semi-AP bombs. On 5 April1942, an IJN carrier force attacked Colombo on Ceylon with half of itscomplement, while the other half was kept in reserve for strikes against ships.Since a second strike against Colombo was deemed necessary, the dive bombers ofthe reserve force were rearmed from semi-AP bombs to land bombs. When Britishheavy cruisers were spotted soon afterwards, the reserve force was sent with aportion of D3A1 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 inorder to intentionally equip the first few D3A1 dive bombers with land bombs.This new method was already implemented for the attack that sank HMS Hermes just four days later, and continued to be used from then on.

During 1942, dive bombing attacks by carrier-based D3A1 and D3A2 bomberssignificantly contributed to sinking of three US fleet carriers: Lexington atthe Battle of the Coral Sea, Yorktown at the Battle of Midway and Hornet at theBattle of the Santa Cruz Islands. In addition, they damaged the carrierEnterprise both at the Battle of the Eastern Solomons and at the Battle of theSanta Cruz Islands. Besides carrier-based units, D3A dive bombers also operated from land bases during the Solomon Islands campaign, where they participated inthe Guadalcanal Campaign, Operation I-Go, Operation SE and Operation RO, and during the New Guinea campaign, where they participated in the Battle of MilneBay and Battle of Buna–Gona. The main land-based unit to operate D3A divebombers during these campaigns and battles was the 2nd/582nd Air Group.

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 (partial list):

USS Peary, American destroyer, 19 February 1942 – Australia (Darwin)
USS Pope, American destroyer, 1 March 1942 – Java Sea
USS Edsall, American destroyer, 1 March 1942- Indian Ocean
USS Pecos, American oiler, 1 March 1942- Indian 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
RFA Athelstone, British freighter, 9 April 1942 - Indian Ocean
HMS Hollyhock, British corvette, 9 April 1942 - Indian Ocean
SS British Sergeant, British Tanker, 9 April 1942 - Indian Ocean
SS Norviken, Norwegian Cargo Ship, 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 (IronbottomSound)
USS Aaron Ward, American destroyer, 7 April 1943 – Pacific Ocean (IronbottomSound)
USS Kanawha, American oiler, 8 April 1943 – Pacific Ocean (Tulagi, SolomonIslands)
USS Brownson, American destroyer, 26 December 1943 – Pacific Ocean[21]
USS Abner Read, American destroyer, sunk by kamikaze 1 November 1944 – PacificOcean
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. 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.

Surviving aircraft
A D3A2 is currently under restoration at the Planes of Fame Museum in Chino,California. There are two unrestored D3As on display at the National Museum ofthe Pacific War in Fredericksburg, Texas. In 2022, the Pearl Harbor Aviation Museum began acquiring the remains of a D3A from Papua New Guinea for eventualexhibit. (Wikipedia)

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(IJNAF Photos)

Aichi D3A1 dive-bomber.

(Author Photo).

Aichi D3A2, codenamed "Val" on display in wrecked "as found" condition on display inside the National Museum of the Pacific War in Fredericksburg, Texas.

(Alan Wilson Photo)

Aichi D3A2 Model 22_Val, (3179), Reg. No. N3131G, currently under restoration at the Planes of Fame Museum in Chino, California.

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