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Drawing D3A1 model 11
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Drawing D3A2 model 22 "Val"
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Aichi D3A1 (99) at the airfield.
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Aichi D3A1 (99) in flight at summer 1941.
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D3N
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- Dive Bomber
- First flight: 1937
- Nakajima
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The success of the Japanese carrier-based dive bomber Aichi D3A "Val" in the first half of the war was so devastating that not even all Japanese aviation experts know that another aircraft could well have been in place of the "Val". Having a more progressive design, better flight data and a much larger reserve for development, a dive bomber developed by Nakajima would have achieved, in any case, no worse results. But, as it often happens, not everything is decided by the best quality level of competing designs. Often the status of a developer firm, as well as a "hairy paw" in the echelons of power, do their job no less efficiently than the brains of engineers.
When in 1936 the technical department of the Imperial Navy Aviation Headquarters Kaigun Koku Hombu formulated the requirements of specification 11-Shi for a new carrier-based dive bomber - according to the Japanese classification - "Carrier-based bomber" "Kanjo Bakugekiki" - to replace the D1A2 biplane in service, in Three companies were invited to participate in the competition: Aichi, as the developer of the aforementioned dive bomber; Nakajima, as the company that had the greatest, albeit unsuccessful, experience in the development of such machines, as well as, of course, Mitsubishi, the traditional supplier of marine aircraft.
Mitsubishi, however, assessing their strength, refused to participate in the competition, and the main struggle unfolded between the Nakajima and Aichi companies.
The Aichi project, eventually realized in the famous "Val", is well known. Structurally, he largely had the German influence of the designs of Ernst Heinkel, with whom the company had been closely cooperating for many years.
But Nakajima's plane was original. The development of the dive bomber Nakajima was headed by Ryozo Yamamoto. The project, which received the internal designation "DB", was distinguished by a number of original solutions. To ensure braking during a dive, unusual landing gear was used. Racks retracted into the wing had an interesting design. They had three positions - the usual, in the released position, when harvesting, they turned around their longitudinal vertical axis and retracted back into the wing niches. But they could also be fixed in the deployed position, so that the wheels were turned against the oncoming air flow, playing the role of brakes. Thus, the specified dive speed limit of 240 knots, about 440 km / h, was provided.
The first prototype, designated D3N1, was ready in March 1937, almost a year ahead of its competitor. And then inexplicable things begin. When the first Nakajima prototype went through almost the entire test cycle, showing very good data, there was no reaction at all from the naval leadership. The Aichi AM-17 prototype, which took off only in December 1937, turned out to be slightly larger in size, had only folding wingtips, while Nakajima's plane could completely fold not only all the consoles, but also the vertical tail. In addition, the Aichi prototype had a shorter range, rate of climb, service ceiling and higher landing speed - that is, those qualities that are usually put at the forefront in the development of deck vehicles. Only, having a more powerful engine, AM-17 developed a little more speed. In terms of armament and bomb load, the aircraft were identical. The very first tests of the AM-17 revealed the low thrust-to-weight ratio of the Aichi aircraft, poor handling and unreliable operation of the aerodynamic brakes. While the D3N was devoid of these shortcomings.
However, the decision of the Kaigun Koku Hombu was delayed ... While the Aichi firm built three prototypes one by one, experimenting with different wings and motors, practically copying the cockpit canopy from Nakajima, the fleet did not issue orders for new Nakajima prototypes.
At the end of 1938, suddenly there was a demand to reduce the previously indicated dive speed limit from 240 knots to 200 knots (364 km / h), surprisingly coinciding with the parameters shown by the AM-17. And at the same time, Nakajima received an order for the production of two more prototypes. Ryozo Yamamoto had to urgently make changes to the design. The extended landing gear could no longer ensure the deceleration of the aircraft to a predetermined value. Perforated brake grids appeared on the trailing edge of the wing, similar to those used on the American Douglas SBD. The slightly more powerful Nakajima "Hikari"-1 Kai engine with a takeoff power of 820 hp was installed on the second and third prototypes, while the D3A1 had already received a 1000 hp Mitsubishi "Kinsei" 43. In the spring of 1939, the Aichi aircraft was declared the winner and was adopted.
It's hard to say what was the reason for such obvious playing along with the Aichi project. The motivation that the D3A showed more speed with a more powerful engine hardly holds up to criticism.
The second prototype D3N1 was left on Nakajima and was used throughout the war as a test bed for different versions of the Sakae and Homare engines. It is curious that during the tests of the NK1F Sakae 21 engine with a power of 1115 hp, which was tested on the D1N1 in early 1941, the aircraft showed a speed of 436 km / h, while the later modification of the Aichi D3A2, equipped with an even more powerful engine 1300-horsepower Mitsubishi "Kinsei" 54 showed only 425 km / h. But it was impossible to change the decision.
The second prototype D3N1 managed to survive the war and was sent for remelting by the "new masters" of Japan only in the fall of 1945.
© Evgeny Aranov
Crew |
2 |
Dimensions |
Wing plane, m |
14.50 |
Wing area, m² |
34.00 |
Length, m |
8.80 |
Height, m |
2.80 |
Powerplant |
1 × PE Nakajima Hikari-1 Kai, power, hp |
1 × 820 |
Weights, kg |
Empty weight |
1,800 |
Loaded weight |
3,400 |
Performance |
Maximum speed, km/h |
344 |
Cruise speed, km/h |
255 |
Rate of climb, m/min |
375 |
Service ceiling, m |
7,000 |
Service range, km |
1,600 |
Armament. Two 7.7 mm Type 97 machine guns above the engine and one 7.7 mm Type 92 machine gun on the gunner's turret.
250 kg bomb on a trapezoid under the fuselage + two 30-60 kg under the wing.
Bibliography
- Aichi B7A Ryusei /E Aranov./
- Experimental Nakajima D3N1 deck dive bomber /Evgeny Aranov/
- "Japan Aircraft of World War II." /Oleg Doroshkevich/
- "Encyclopedia of military engineering" /Aerospace Publising/
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