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Yokosuka D4Y Suisei


Influenced by flight tests with a Heinkel He 118 in 1938, the Japanese navy decided that future carrier-based aircraft should be much cleaner aerodynamically. A 13-Shi (1938) specification was issued to the Yokosuka naval air arsenal for a carrier--based dive-bomber of exceptionally high performance. It had to operate from small car-riers and carry a 250-kg (551-lb) bombload for 800 nautical miles (1481 km) and reach 280 knots (519 km/h).
Designed as a fast carrier-based attack bomber and powered by an imported Daimler-Benz DB 600G engine, the D4Y1 was first flown in December 1941.

Achieving excellent performance despite having only a 960-hp DB 600G, the D4Y1-C reconnaissance aircraft were ordered into production at Aichi's Nagoya plant, the first of 660 aircraft being completed in the late spring of 1942.

It was not until March 1942 that the first production D4Y1 Model 11 emerged from the Aichi factory at Nagoya (the Allies later thought this an Aichi design). Powered by the 1200‑hp, Aichi AE1A Atsuta 12 inverted‑V‑12 (licence‑built modified DB 601A) the aircraft had such speed and range it was ordered as the D4Y1‑C reconnaissance aircraft, with rear fuselage camera(s) and underwing drop tanks, and the ‑C model remained in use until Japan's final surrender.Work continued to perfect the basic D4Y1 and eventually it entered service in March 1943. The first service aircraft were lost when the Soryu was sunk at Midway. The Model 21 was generally similiar. Many D4Y1s were completed as dive-bombers, and 174 Suiseis of the 1st, 2nd and 3rd Koku Sentais were embarked in nine carriers before the Battle of the Philippine Sea. However, they were intercepted by American carriers, and suffered heavy casualties without achieving any success.

Production amounted to 660 by Aichi, with the Japanese name Suisei (Comet) and the Allied code-name 'Judy', but in the first big action at the Marianas 'turkey shoot' they suffered severe casualties at the hands of US Navy fighters and failed to sink any major warships. Their chief faults were complete absence of armour or self-sealing tanks and the armament of two fixed 7.7-mm (0.303-in) Type 97 machine-guns in the nose and a 7.92-nun (0.312-in) Type 1 aimed by the radio operator/navigator/gunner in the rear seat. Normal bombload was 310 kg (683 lb), but for short ranges 560 kg (1234 lb) could be accommodated.

Like many of the best Japanese aircraft of the Second World War, the D4Y had the misfortune to enter service just as the era of Japanese superiority was coming abruptly to an end. The fleet carriers were fairly soon all sent to the bottom of the Pacific, and most of the total of 2038 of all versions of D4Y operated from escort carriers and shore bases, often in roles quite different from those for which the type was designed. The first new sub‑type, other than the ‑C, was the D4Y2 (Model 22), which had the 1400‑hp Atsuta 32 engine, and the fin and rudder were modified and increased in area, and, in the main D4Y2a variant, a 13mm (0.51‑in) Type 2 gun in the rear cockpit. Entering service just in time for the Leyte Gulf and Philippines battles in October 1944, the new model was coolly received, because it still had neither armour nor tank protec­tion. Aichi built 326, plus about 100 by Dai‑Juichi Kaigun Kokusho (Hiro Naval Air Arsenal), but they were shot out of the sky and soon appeared as kamikaze suicide attackers, usually with an 800‑kg (1764‑lb) bombload, carried externally.





From the start the liquid-cooled engine had been unpopular, owing to its difficult maintenance and poor reliability. The general feeling about the trim Suisei had been that there was not much wrong with it that proper protection and a radial engine would not cure, and in the winter of 1943/4 the Aichi team schemed an installation for the 14-cylinder two-row Mitsubishi Mk8P Kinsei 62.

The D4Y3 prototype, flown in May 1944, showed acceptable handling qualities and almost identical performance to the earlier models, with marginally lower speed but longer range and improved takeoff and climb capability. Production was authorized at once, and both Aichi and Hiro arsenal delivered a total of about 350 in all. These still did not have any protection for crew or fuel, and only the later D4Y3a had a 13-mm (0.51in) rear gun. Most had provision for catapulting but as there were virtually no carriers, the majority were also equipped to have three RATO rockets clipped below the rear fuselage to assist takeoff from island airstrips.

The last sub-type was the D4Y4, a purpose-designed kamikaze aircraft. A single-seater, it carried an 800-kg (1764-lb) bomb or explosive charge (made from a mine or torpedo) semi-externally. 296 were delivered by Aichi in 1945.

The proposed D4Y5, with 1825-hp NK9C Homare engine and proper armour and protected tanks, did not fly. The D4Y2 was later converted to a night fighter.

A total of 2,319 D4Ys was completed. Aichi handled most of the payroll and 500 were completed by Hiro Arsenal.


Engine: 1 x Aichi AE1P Atsuta, 1050kW
Max take-off weight: 3840 kg / 8466 lb
Empty weight: 2640 kg / 5820 lb
Wingspan: 11.5 m / 38 ft 9 in
Length: 10.2 m / 33 ft 6 in
Height: 3.75 m / 12 ft 4 in
Wing area: 22.8 sq.m / 245.42 sq ft
Max. speed: 575 km/h / 357 mph
Cruise speed: 425 km/h / 264 mph
Ceiling: 10700 m / 35100 ft
Range: 3600 km / 2237 miles
Crew: 2
Armament: 7.92 or 13mm machine-guns
Bombload: 1 x 500-kg, 2 x 30-kg

Engine: Mitsubishi Kinsi 62, 1560 hp
Span: 11.5 m (37ft 8.75in)
Length: 10.22 m (33 ft 6.5 in)
Height: 10 ft 9.5 in
Empty weight: 5514 lb
Gross weight. 4657 kg (10267 lb)
Maximum speed: 575 km/h (357 mph) at 19,360 ft
Service ceilig: 34,450 ft
Max range: 944 miles
Armament: 1 x 7.9mm mg, 2 x 7.7mm mg
Bombload: 1650 lb
Crew: 2


Yokosuka D4Y Suisei / Judy


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