Aichi D3A
Aichi D3A
Description
Role	Dive bomber
Crew	two, pilot and gunner
First Flight	January 1938
Entered Service
Manufacturer	Aichi
Dimensions
Length	10.2 m	33 ft 5 in
Wingspan	14.37 m	47 ft 2 in
Height	3.85 m	12 ft 8 in
Wing area	ft²	m²
Weights
Empty	2,408 kg	5,309 lb
Loaded	lb	kg
Maximum takeoff	3,650 kg	8,047 lb
Powerplant
Engine	Mitubishi Kinsei 44
Power	798 kW	1,070 hp
Performance
Maximum speed	427 km/h	240 mph
Combat range	1,472 km	915 miles
Ferry range	miles	km
Service ceiling	9,300 m	30,500 km
Rate of climb	m/min	km/min
Wing loading	lb/ft²	kg/m²
Power/mass	hp/lb	kW/kg
Armament
Guns	3 × 7.7 mm Type 97 machineguns
Bombs	250 kg (main) 2 × 60 kg (secondary)	551 lb (main) 2 × 132 lb (secondary)

The Aichi D3A (99式艦上爆撃機, Allied code name Val) 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 elliptical 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 710 hp (529 kW) 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 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 prior to delivery to try to address the problems. Power was increased by replacing the Hikari with the 840 hp (626 kW) 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 1,000 hp (746 kW) Kinsei 43 or 1,070 hp (798 kW) 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 Type 97 machine-guns, and one flexible 7.7 mm Type 92 machine gun in the rear cockpit for defense. Normal bombload was a single 250 kg (550 lb) bomb carried under the fuselage, which was swung out under the prop 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.

Starting with the attack on Pearl Harbor, the D3A1 took part in all major Japanese carrier operations in the first ten months of the war. They achieved fame during the Indian Ocean raid in April 1942 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 1,300 hp (970 kW) 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 U.S. 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.