Aerodynamic issues and problems with the strength of the wing and brake-flaps were resolved only by March 1943 when Naval Carrier-Based Bomber ‘Susie’ Model 11 (D4Y1) was finally fielded. Production of the airplane was quickly stepped up and in the "Mariana Turkey Shoot" 170 D4Y1 and D4Y1-С aircraft participated as victims. Nonetheless, the Japanese Navy leadership was still unwilling to sacrifice operating range for fuel tank protection and crew safety, and the next Model 12 (D4Y2) that was launched into production in October 1944 differed only in that its Aichi AE1P Atsuta-32 engine power rating was increased to 1400 hp. Some of the production machines (Models 12а D4Y2a and D4Y2-Сa) featured a self-defense 13.2-mm machine gun (Type 2, 13-mm), while Model 22 and Model 22А were equipped for catapult launching from short-decked light aircraft carriers.
Yokosuka D4Y3 «Susei»
Aichi's Atsuta engine had low reliability and endurance and was difficult to maintain and repair. Aichi designers instead offered to modify Comet's nose in order to accommodate a proven 14-cylinder, twin-row, radial Mitsubishi MK8P Kinsei-62 engine. A test program conducted in May 1944 demonstrated that the increase to a 1560 hp engine power rating together with a new engine cowling and improved fairings had slightly improved aircraft flight performance characteristics. The only adverse effect of this larger-size front was restricted view at takeoff and landing. The new Model 33 and Model 33а (D4Y3 и D4Y3a) were immediately put into production, while production of D4Y2 in August 1944 was transferred to the smaller manufacturing facilities at the 11th Naval Aviation Arsenal at Hiro. It was here that the Japanese attempted to make a D4Y2-S night fighter: all bomb equipment was removed and a 20-mm Type 99 Model 2 cannon with its upward-pitched barrel was installed in place of the gunner's cockpit. However, lack of radar and a slow rate of climb made the Susei-Е night fighter ineffective. The last modified version in the Comet production was the D4Y4 Susei Special Strike Bomber Model 43. This one-seat kamikaze airplane capable of carrying one 800-kg bomb was launched into production in February 1945. It was equipped with terminal dive acceleration and solid boosters for takeoff from short runways. There is no data concerning how many of the 294 manufactured D4Y4s actually succeeded in damaging American ships. In all, 2038 D4Y dive bombers were produced, and it was only the loss of aircraft carriers and experienced pilots to superior American airpower in 1944-45 that prevented this outstanding aircraft from becoming a true success story.
B7A2 profiles
cockpit of a museum B7A2.
The last Japanese carrier-based bomber of WWII was the Aichi B7A Rusei (Falling Star). This aircraft never took off on a military mission from the deck of an aircraft carrier. Work on this project started in 1941. This machine was supposed to replace both the D4Y dive bomber and the B6N torpedo bomber on a new series of heavy aircraft carriers; therefore, its size and weight allowances were much more liberal. To obtain desired flight performance, an advanced Nakajima Homare 18-cylinder twin-row radial power plant rated at 2000 hp was selected for this large single-engine aircraft. The prototype that flew for the first time in May 1942, demonstrated excellent flight performance, although persistent engine problems delayed series production, which started only in April 1944 at Aichi's Funakate plant and the 21st Naval Aviation Arsenal in Omara.
B7A2 being prepared for operational flight, 1945 г.
B7A2 being tested in the United States after the war.
The Naval Carrier-based Strike Bomber Rusei’ (B7A2) was equipped with the Nakajima NK9C Homare-12 engine rated at 1825 hp at take off. The large bomb bay for a 500-kg bomb became a determining factor in the selection of a mid-wing design. An externally carried torpedo and a large four-blade propeller required a fuselage elevated high above the ground so that the airplane received an inverted gull-wing (similar to the American F4U Corsair fighter) to reduce the height of its landing gear. The trailing edge of the center wing section sported flaps with airbrakes in front of them. The consoles folded upwards and were equipped with elevons (ailerons that deflect 10 degrees down when flaps are extended). In the center wing section beyond the propeller diameter were mounted two 20-mm Type 99 Model 2 cannons, and an additional 13.2-mm machine gun was installed in the gunner-radioman's cockpit. By the end of 1944, when B7A2 or “Grace” was finally ready for deployment, Japan had lost all its aircraft carriers so that those few B7A2 squadrons that were formed had to operate from island bases. In May 1945 the Funakata plant was destroyed in an earthquake so that only 105 B7A2s were manufactured until the end of the war. The aircraft did not score any notable successes.
P1Y1 profiles
the cockpit of a museum P1Y1.
With all its aircraft carriers lost, the Japanese navy now had to rely on the fast twin-engine Yokosuka P1Y Ginga (Milky Way) bomber. This aircraft earned the respect of the Allies, who knew it as “Frances”. The order for the development of a strike aircraft comparable to the latest American North American B-25 Mitchell and Martin B-26 Marauder bombers and equipped with the same Nakajima Homare engine as the B7A, was given to the 1st Naval Technical Aviation Arsenal in Yokosuka at the end of 1940. Production, including manufacture of prototypes, was planned to take place at the Nakajima plant in Kaizume, but because of engine delays, the first prototype was assembled only in August 1943. The aircraft flew beautifully as long as its capricious engines and hydraulics were operating adequately. The aircraft was launched into production but its drive train, engine, equipment and weapon systems still continued to undergo improvements. The Japanese Fleet was obliged to officially put the Naval Ginga Bomber Model 11 (P1Y1) into its inventory in October 1944 when 453 of the aircraft were already manufactured. Actually, the bomber started to fly combat missions only in February 1945, when all its engine problems were finally resolved.
In conclusion, some words should be said about different pilot training and operational practices, which, together with other factors, determined the outcome of the Pacific war. Rewards for experienced pilots were not in keeping with Japanese traditions. The pilots fought continuously until killed or heavily wounded. Nobody cared about the living conditions or comfort of the flight crews, nor about the need for adequate armor plating to protect them. All these and other hardships endured by the Japanese airmen were considered to be part of their duty. As a result, by the end of 1942 nearly all experienced Japanese pilots had perished either in epidemics or in burning aircraft with insufficient protection. In American practice, on the other hand, in any invasion the fighting units were quickly followed by construction units, which built canteens, bars, cinemas, saunas and other amenities for the flight crews and technical personnel. The pilots, after finishing flight school, practiced with their regiments for a whole year before they were considered fit for deployment to a war theater. After 25-50 combat missions they were granted a furlough for recuperation. The aces were sent to flight schools as instructors and not allowed to fight any longer. Thus, the overwhelming air superiority that the American naval aviation enjoyed by 1944 reflected not only superior numbers of better aircraft but also and primarily the superior experience of American aircrews.
Yokosuka P1Y «Ginga», 1945.
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