Aichi D3A

The Aichi D3A, (Allied reporting name "Val") was a World War II carrier-borne dive bomber of the Imperial Japanese Navy (IJN). It was the primary dive bomber in the Imperial Japanese Navy, and participated in almost all actions, including the attack on Pearl Harbor. The Aichi D3A was the first Japanese aircraft to bomb American targets in World War II, commencing with Pearl Harbor and U.S. bases in the Philippines, such as Clark Air Force Base. During the course of the Second World War, the Val dive bomber sank more Allied warships than any other Axis aircraft, despite being considered obsolescent when the war started.

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. 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).

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.

In December 1939, the Navy ordered the aircraft as the Navy Type 99 Carrier Bomber Model 11 (kanjō bakugekiki, usually abbreviated to 艦爆 kanbaku.[9]). 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, and the aircraft actually became highly maneuverable.

Armament was two forward-firing 7.7 mm (.303 in) Type 97 machine guns, and one flexible 7.7 mm (.303 in) Type 92 machine gun in the rear cockpit for defense. Normal bombload was a single 250 kg (550 lb) bomb carried under the fuselage, 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.

The D3A1 commenced carrier qualification trials aboard the 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. Val dive bombers scored over 80% hits with their bombs during attacks on two heavy cruisers and an aircraft carrier during the operation. 

During the course of the war, Val dive bombers often combined their attacks upon enemy warships with the IJN Kate torpedo bomber; consequently enemy vessels were often sunk by a combination strike of bombs and torpedoes. However, there were occasions when just the Vals would make the attacks, or at least score the sinking hits. Discounting the Pearl Harbor strike, which also used the Nakajima B5N for level bombing and torpedo attacks, Val dive bombers were credited with sinking the following Allied warships.

Allied warships sunk by Aichi D3As; type, nation, date of loss, location
USS Peary, American destroyer, 19 February 1942 - Australia (Darwin)
USS Langley, American seaplane tender 
(scuttled by U.S. forces after attack) 27 Feb 1942 - Pacific Ocean
USS Pope, American destroyer, 1 March 1942 - Pacific 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
HMAS Vampire, Australian destroyer, 9 April 1942 - Indian Ocean
USS Sims, American destroyer, 7 May 1942 - Pacific Ocean
USS Benham, American destroyer, 15 November 1942 - Pacific Ocean
USS De Haven, American destroyer, 1 February 1943 - Pacific Ocean
USS Aaron Ward, American destroyer, 7 April 1943 - Pacific Ocean
USS Brownson, American destroyer, 26 December 1943 - Pacific Ocean[16]
USS Abner Read, American destroyer,
sunk by kamikaze 1 November 1944 - Pacific Ocean
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. In June 1942, an improved version of the D3A powered by a 969 kW (1,300 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. Another unrestored D3A2 is on display at the National Museum of the Pacific War in Fredericksburg, Texas 

Specifications D3A1
Crew: Two, pilot and gunner
Length: 10.2 m 
Wingspan: 14.37 m
Height: 3.85 m 
Wing area: 34.9 m2
Empty weight: 2,408 kg 
Max. takeoff weight: 3,650 kg 
Powerplant: 1 × Mitsubishi Kinsei 44, 798 kW / 1,070 hp
Maximum speed: 389 km/h 
Range: 1,472 km 
Service ceiling: 9,300 m 
Armament: 2 × fixed, forward-firing 7.7 mm (0.303 in) Type 97 machine guns
1 × flexible, rearward-firing 7.7 mm (0.303 in) Type 92 machine gun
1 × 250 kg (551 lb) or 2 × 60 kg (132 lb) bombs
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Specifications (D3A2)
Aichi D3A2 with telescopic sight, before take off.
D3A2 with Type 98 bomb, marked as an aircraft assigned to Akagi

General
Crew: Two (pilot and gunner)
Length: 10.2 m (33 ft 5.4 in)
Wingspan: 14.37 m (47 ft 2 in)
Height: 3.8 m (12 ft 7.5 in)
Wing area: 34.9 m² (375.6 ft²)
Empty weight: 2,570 kg (5,666 lb)
Max. takeoff weight: 4,122 kg (9,100 lb)
Powerplant: 1 × Mitsubishi Kinsei 54, 969 kW (1,300 hp)
Maximum speed: 430 km/h (232 kn, 267 mph (430 km/h))
Range: 1,352 km (730 nmi, 840 mi (1,350 km))
Service ceiling: 10,500 m (34,450 ft)
Rate of climb: 8.62 m/s (1,869.685 ft/min)
Armament: 2 × fixed, forward 7.7 mm (0.303 in) Type 97 machine guns
1 × flexible, rearward-firing 7.7 mm (0.303 in) Type 92 machine gun
1 × 250 kg (551 lb) or 2 × 60 kg (132 lb) bombs