Top speed 550 km/h Length 10 m Number built 2,038 | Wingspan 12 m Engine type Reciprocating engine First flight December 1940 | |
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The Yokosuka (横須賀) D4Y Suisei (彗星, "Comet") Navy Carrier dive bomber was operated by the Imperial Japanese Navy. Its Allied reporting name was "Judy". The D4Y was one of the fastest dive-bombers of the war and only the delays in its development hindered its service while its predecessor, the slower fixed-gear Aichi D3A, remained in service much longer than intended. Despite limited use, the speed and the range of the D4Y were nevertheless valuable, and the type was used with success as reconnaissance aircraft as well as for kamikaze missions.
Contents
- Yokosuka d4y suisei judy
- Design and development
- Operational history
- Marianas
- Leyte and Philippines
- In defense of the homeland
- Night fighter
- Last action
- Operators
- Surviving aircraft
- Specifications D4Y2
- References
Yokosuka d4y suisei judy
Design and development
Development of the aircraft began in 1938 at the Yokosuka Naval Air Technical Arsenal as a carrier-based dive bomber to replace the Aichi D3A. The aircraft was a single-engine, all-metal low-wing monoplane, with a wide-track retractable undercarriage and wing-mounted dive brakes. It had a crew of two: a pilot and a navigator/radio-operator/gunner, seated under a long, glazed canopy which provided good all-round visibility. The pilot of bomber versions was provided with a telescopic bombsight. The aircraft was powered by an Aichi Atsuta liquid-cooled inverted V12 engine, a licensed copy of the German DB 601, rated at 895 kW (1,200 hp). The radiator was behind and below the three-blade propeller, as in the P-40 Warhawk.
The aircraft had a slim fuselage that enabled it to reach high speeds in horizontal flight and in dives, while it had excellent maneuverability despite high wing loading, with the Suisei having superior performance to contemporary dive bombers such as the Curtiss SB2C Helldiver. In order to conform with the Japanese Navy's requirement for long range, weight was minimized by not fitting the D4Y with self-sealing fuel tanks or armour. In consequence, the D4Y was extremely vulnerable and tended to catch fire when hit.
Bombs were fitted under the wings and in an internal fuselage bomb bay. It usually carried one 500 kg (1,100 lb) bomb but there were reports that the D4Y sometimes carried two 250 kg (550 lb) bombs, for example during the attack on the light aircraft carrier USS Princeton; only 30 kg (70 lb) bombs were carried externally. The aircraft was armed with two 7.7 mm (.303 in) Type 97 aircraft machine guns in the nose and a 7.92 mm (.312 inm) Type 1 machine gun selected for its high rate of fire, in the rear of the cockpit. The rear gun was replaced by a 13 mm (.51 in) Type 2 machine gun. This armament was typical for Japanese carrier-based dive-bombers, unlike "carrier attack bombers" (i.e. torpedo bombers) like the Nakajima B5N and B6N which were not given forward-firing armament until the late-war Aichi B7A, which was expected to serve as both a dive-bomber and torpedo-bomber, and was given a pair of 20mm Type 99-2 cannon. The forward machine guns were retained in the kamikaze version.
The first (of five) prototypes made its maiden flight in December 1940. After the prototype trials, problems with flutter were encountered, a fatal flaw for an airframe subject to the stresses of dive bombing. Until this could be resolved, early production aircraft were used as reconnaissance aircraft, as the D4Y1-C, which took advantage of its high speed and long range, while not over-stressing the airframe. Production of the D4Y1-C continued in small numbers until March 1943, when the increasing losses incurred by the D3A resulted in production switching to the D4Y1 dive-bomber, the aircraft's structural problems finally being solved. Although the D4Y could operate from the large fleet carriers that formed the core of the Combined Fleet at the start of the war, it had problems operating from the smaller and slower carriers such as the Hiyō class which formed a large proportion of Japan's carrier fleet after the losses of the Battle of Midway. Catapult equipment was fitted, giving rise to the D4Y1 Kai (or improved) model.
Early versions of the D4Y were difficult to keep operational because the Atsuta engines were unreliable in front-line service. From the beginning, some had argued that the D4Y should be powered by an air-cooled radial engine which Japanese engineers and maintenance crew had experience with, and trusted. The aircraft was re-engined with the reliable Mitsubishi MK8P Kinsei 62, a 14-cylinder two-row radial engine as the Yokosuka D4Y3 Model 33.
Although the new engine improved ceiling and rate of climb (over 10,000 m/32,800 ft, and climb to 3,000 m/9,800 ft in 4.5 minutes, instead of 9,400 m/30,800 ft and 5 minutes), the higher fuel consumption resulted in reduced range and cruising speed and the engine obstructed the forward and downward view of the pilot, hampering carrier operations. These problems were tolerated because of the increased availability of the new variant.
The last version was the D4Y4 Special Strike Bomber, a single-seat kamikaze aircraft, capable of carrying one 800 kg (1,760 lb) bomb, which was put into production in February 1945. It was equipped with three RATO boosters for terminal dive acceleration. This aircraft was an almost ideal kamikaze model: it had a combination of speed (560 km/h/350 mph), range (2,500 km/1,550 mi) and payload (800 kg/1,760 lb) probably not matched by any other Japanese aircraft.
The D4Y5 Model 54 was a planned version designed in 1945. It was to be powered by the Nakajima NK9C Homare 12 radial engine rated at 1,361 kW (1,825 hp), a new four-blade metal propeller of the constant-speed type and more armour for the crew and fuel tanks. Ultimately, 2,038 of all variants were produced, mostly by Aichi.
Operational history
Lacking armor and self-sealing fuel tanks, the Suiseis did not fare well against Allied fighters. They did, however, cause considerable damage to ships, including the carrier USS Franklin which was nearly sunk by an assumed single D4Y and the light carrier USS Princeton which was sunk by a single D4Y.
The D4Y was operated from the following Japanese aircraft carriers: Chitose, Chiyoda, Hiyō, Junyō, Shinyo, Shōkaku, Sōryū, Taihō, Unryū, Unyō and Zuikaku.
The D4Y1-C reconnaissance aircraft entered service in mid-1942, when two of these aircraft were deployed aboard Sōryū at the Battle of Midway, both of which were lost when Sōryū was sunk.
Marianas
During the Battle of the Marianas, the D4Ys were engaged by U.S. Navy fighters and shot down in large numbers. It was faster than the Grumman F4F Wildcat, but not the new Grumman F6F Hellcat which entered combat in September 1943. The Japanese aircraft were adequate for 1943, but the rapid advances in American materiel in 1944 (among them, the introduction in large numbers of the Essex-class aircraft carrier) left the Japanese behind. Another disadvantage suffered by the Japanese was their inexperienced pilots.
The U.S. Task Force 58 struck the Philippine airfields and destroyed the land air forces first, before engaging Japanese naval aircraft. The result was what the Americans called "The Great Marianas Turkey Shoot", with 400 Japanese aircraft shot down in a single day. A single Hellcat pilot, Lieutenant Alexander Vraciu, shot down six D4Ys within a few minutes.
One D4Y was said to have damaged the battleship USS South Dakota.
Leyte and Philippines
The D4Y was relegated to land operations where both the liquid-cooled engine D4Y2, and the radial engine D4Y3 fought against the U.S. fleet, scoring some successes. An unseen D4Y bombed and sank the Princeton on 24 October 1944. D4Ys hit other carriers as well, by both conventional attacks and kamikaze actions. In the Philippines air battles, the Japanese used kamikazes for the first time, and they scored heavily. D4Ys from 761 Kōkūtai may have hit the escort carrier USS Kalinin Bay on 25 October 1944, and the next day, USS Suwannee. Both were badly damaged, especially Suwannee, with heavy casualties and many aircraft destroyed. A month later on 25 November, USS Essex, Hancock, Intrepid and Cabot were hit by kamikazes, almost exclusively A6M Zero fighters and D4Ys, with much more damage. D4Ys also made conventional attacks. All these D4Ys were from 601 and 653 Kōkūtai.
In defense of the homeland
Task Force 58 approached southern Japan in March 1945 to strike military objectives in support of the invasion of Okinawa. The Japanese responded with massive kamikaze attacks, codenamed Kikusui, in which many D4Ys were used. A dedicated kamikaze version of the D4Y3, the D4Y4 with a non-detachable 800 kg bomb attached in a semi-recessed manner, was developed. The Japanese had begun installing rocket boosters on some Kamikazes, including the D4Y4 in order to increase speed near the target. As the D4Y4 was virtually identical in the air to the D4Y3, it was difficult to determine the sorties of each type.
Carriers USS Enterprise and Yorktown were damaged by D4Ys of 701 Wing on 18 March. On 19 March, the carrier USS Franklin was hit with two bombs from a single D4Y, which then escaped despite heavy anti-aircraft fire. Franklin was so heavily damaged that she was retired until the end of the war. Another D4Y hit the carrier USS Wasp.
On 12 April 1945, another D4Y, part of Kikusui mission N.2, struck Enterprise, causing some damage.
During Kikusui N.6, on 11 May 1945, USS Bunker Hill was hit and put out of action by two kamikazes that some sources identify as D4Ys. This was the third Essex-class carrier forced to retire to the United States to repair.
Night fighter
The D4Y was faster than the A6M Zero and some were employed as D4Y2-S night fighters against Boeing B-29 Superfortress bombers late in the war. The night fighter conversions were made at the 11th Naval Aviation Arsenal at Hiro. Each D4Y2-S had its bombing systems and equipment removed, and replaced by a 20 mm Type 99 cannon installed in the rear cockpit, with the barrel slanted up and forwards in a similar manner to the German Schräge Musik armament fitting (pioneered by the IJNAS in May 1943 on the Nakajima J1N). Some examples also carried two or four 10 cm air-to-air rockets under the wings; lack of radar for night interceptions, inadequate climb rate and the B-29's high ceiling limited the D4Y2-S effectiveness as a night fighter. Little is known of their operations.
Last action
At the end of the war, D4Ys were still being used operationally against the U.S. Navy. Among the last of these were 11 aircraft led by Vice Admiral Matome Ugaki on a search mission on 15 August 1945, of which all but three were lost.
Operators
Surviving aircraft
A restored D4Y1 (serial 4316) is located at the Yasukuni Jinja Yūshūkan shrine in Tokyo.
An engineless D4Y1 was recovered from Babo Airfield, Indonesia in 1991. It was acquired and restored to non-flying status by the Planes of Fame Air Museum in Chino, California. It was restored to represent a radial engined D4Y3, using an American Pratt & Whitney R-1830 engine. The engine is in running condition and can be started to demonstrate ground running and taxiing of the aircraft.
Specifications (D4Y2)
Data from The Encyclopedia of World Aircraft
General characteristics
Performance
Armament