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Yokosuka D4Y Suisei (Judy) Carrier-Borne Dive Bomber Aircraft

Though hitting some speed bumps early on in its development evolution, the D4Y proved to be a capable carrier-based performer.

 Updated: 7/7/2017; Authored By Staff Writer; Content ¬©

The Yokosuka D4Y Suisei (translating to "Comet" and nicknamed "Judy" by the Allies) was a capable dive bomber serving the Imperial Japanese Navy during the Second World War. The system saw some reliability issues in early presentations and suffered heavy losses at the hands of Allied carrier groups but the system performed admirably well thanks to the performance capabilities inherent in the design - this of course at the expense of crew protection and structural armoring.

The D4Y was a single engine, two-crew dive bomber platform. The Mitsubishi MK8P Kinsei 62 radial piston engine found in the D4Y3 model offered up reliability with performance at 357 miles per hour with a ceiling of nearly 35,000 feet. The crew sat in a long greenhouse-type canopy in tandem. Defensive armament consisted of twin 7.7mm machine guns in a forward-fixed position and a single 13.1mm machine gun in a trainable rear cockpit mounting. External ordnance was limited to 1,235 pounds of stores. Overall, the design concept actually stemmed from the German Heinkel He 118, as Japan purchased manufacturing rights for the German type back in 1938.

The D4Y first flew in late 1942 in its dive bomber form designated simply as the D4Y1. The system then appeared shortly thereafter in a reconnaissance form as the D4Y1-C. Before long, the D4Y series was fielded in quantity across several Japanese carrier groups and would see yet another improved version - known as the D4Y2 - appear. This one being fitted with a Atsuta 32 Aichi-brand 1,400hp engine. It was soon found, however, that the aircraft, though performing well in terms of capability, suffered from reliability problems with the new engine. To add insult to injury, the performance gains brought about by the new powerplant were negated to some extent by the fact that crew and fuel protection was not addressed, leading to heavy losses. The D4Y3 addressed the D4Y2's reliability problems with the introduction of the Mitsubishi MK8P Kinsei 62 radial piston engine. By the end of the war, as with most of the IJN's small airframes, the D4Y was made into a dedicated suicide model. This one, a single-seater, was designated as the D4Y4 and fielded in 1945.

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Yokosuka D4Y3 Suisei (Judy) Technical Specifications

Service Year: 1942
Type: Carrier-Borne Dive Bomber Aircraft
National Origin: Imperial Japan
Manufacturer(s): Yokosuka - Japan
Production Total: 2,033

Structural (Crew Space, Dimensions and Weights)

Operating Crew (Typical): 2
Overall Length: 33.53 feet (10.22 meters)
Overall Width: 37.73 feet (11.50 meters)
Overall Height: 12.27 feet (3.74 meters)

Weight (Empty): 5,514 lb (2,501 kg)
Weight (MTOW): 10,267 lb (4,657 kg)

Installed Power and Standard Day Performance

Propulsion: 1 x Mitsubishi MK8P Kinsei 62 radial piston engine developing 1,560 horsepower.

Maximum Speed: 357 mph (575 kph; 310 knots)
Maximum Range: 944 miles (1,520 km)
Service Ceiling: 34,449 feet (10,500 meters; 6.52 miles)
Rate-of-Climb: 2,163 feet-per-minute (659 m/min)

Armament / Mission Payload

2 x 7.7mm Type 97 machine guns in fixed forward-firing nose mount.
1 x 13.1mm Type 2 machine gun in trainable mount in rear cockpit position.

Up to 1,235 lb of conventional drop bombs.

Global Operators / Customers

Imperial Japan

Model Variants (Including Prototypes)

D4Y1 - Initial dive bomber model; fitted with Daimler-Benz DB 600G powerplant (imported from Germany).
D4Y1-C - Reconnaissance Variant
D4Y2 - 1 x 13.2mm machine gun in trainable rear cockpit mounting replacing original 1 x 7.92mm machine gun.
D4Y3 - Fitted with Kinsei 62 radial engine.
D4Y4 - Single-seat suicide dive-bomber