Category Archives: Imperial Navy Air Force

Japan

Nightfighter, Torpedobomber, Reconnaissance

Nakajima C6N1-S ‘Saiun’, (Iridecent Cloud), (Myrt). 302nd Kokutai, (Hasegawa)

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TYPE: Carrier-based reconnaissance aircraft, land-based night fighter

ACCOMMODATION:  Crew of two

POWER PLANT: One Nakajima NK9B Homare 11 air-cooled radial engine, rated at 1,991 hp

PERFORMANCE: 380 mph at 20,000 ft

COMMENT: The Nakajima C6N Saiun ( “Iridecent Cloud“) was a carrier-based reconnaissance aircraft  used by the Imperial Japanese Navy Air Service in World War II. Advanced for its time, it was the fastest carrier based aircraft put into service by Japan during the war. The Allied reporting name was Myrt.
The Nakajima C6N originated from a 1942 Imperial Japanese Navy specification for a carrier-based reconnaissance plane with a top speed of 403 mph at 19,700 ft and a range of 2,500 nautical miles. Nakajima’s initial proposal, designated N-50, was for a craft with two 1,000 hp engines housed in tandem in the fuselage, driving two propellers mounted on the wings. With the development of the 2,000 hp class Nakajima Homare engine, the dual powerplant configuration was abandoned and Nakajima decided on a more conventional single-engine layout. Unfortunately the new Homare’s power output was less than expected, and the design had to be optimized in other areas. The resulting aircraft was designed around a long and extremely narrow cylindrical fuselage just large enough in diameter to accommodate the engine. The crew of three sat in tandem under a single canopy, while equipment was similarly arranged in a line along the fuselage. The C6N’s low-mounted laminar flow wing housed fuel tanks and was fitted with both Fowler and slit flaps and leading-edge slats which lowered the aircraft’s landing speed to ease use aboard aircraft carriers. Like Nakajima’s earlier B6N Tenzan torpedo bomber, the vertical stabilizer was angled slightly forward to enable tighter packing on aircraft carrier decks.
The C6N’s first flight was on May 1943, with the prototype demonstrating a speed of 397 mph. Performance of the Homare engine was disappointing, especially its power at altitude, and a series of 18 further prototypes and pre-production aircraft were built before the Saiun was finally ordered into production in February 1944.
Although designed for carrier use, by the time it entered service in September 1944 there were few carriers left for it to operate from, so most C6Ns were flown from land bases. Its speed was exemplified by a telegraph sent after a successful mission: “No Grummans can catch us.” The top speed of the Grumman F6F Hellcats was indeed of the same level, so overtaking a Saiun was out of the question.
A total of 463 aircraft were produced. A single prototype of  turbocharged development mounting a 4-blade propeller was built; this was called the C6N2 Saiun-kai. Several examples of a night fighter version C6N1-S with oblique-firing (Schräge Musik configuration) single 30 mm (or dual 20 mm) cannon were converted from existing C6N1s. As Allied bombers came within reach of the Japanese home islands, a first class night fighter was required. This led Nakajima to develop the C6N1-S by removing the observer and replacing him with two 20 mm cannons. The C6N1-S’s effectiveness was hampered by the lack of air-to-air radar, although it was fast enough to enjoy almost complete immunity from interception by Allied fighters. The 30 mm version was only used to attack Boeing B-29 Superfortress once, on August 1, 1945. The destructive power of the Type 2 cannon extended to twisting the skin of the Saiun’s lightweight fuselage.
A torpedo carrying C6N1-B was also proposed, but was not needed after most of Japan’s aircraft carriers were destroyed.
Despite its speed and performance, on 15 August 1945 a C6N1 happened to be the last aircraft to be shot down in World War II. Just five minutes later, the war was over and all Japanese aircraft were grounded (Ref. 24).

Trainer

Kyushu W11W1 Shiragiku, (White Crysanthemum), Tokai Chimtao Okutai (Pavla Models)

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TYPE: Trainer aircraft

ACCOMMODATION: Crew of five

POWER PLANT: One Hitachi GK2B Amakaze 21 radial engine, rated at 515 hp

PERFORMANCE: 140 mph at 5,577 ft

COMMENT: The Kyushu K11W Shiragiku (“White Chrysanthemum”) was a land-based bombing trainer aircraft which served in the Imperial Japanese Navy Airforce Service (IJN) in the latter years of World War II.
In late 1940 work on a single-engined crew trainer began at K.K. Watanabe Tekkosho to meet the requirements set by the Japanese Navy in the 15-Shi specification calling for an aircraft intended to replace the Navy Type 90 Operations Trainer Mitsubishi K3M. Even though the aircraft was to be used to train a complete bomber crew, Watanabe retained a single-engine configuration and, with its wings mounted at mid-fuselage, deep belly and retactable main undercarriage, the aircraft bore a strong resemblage to the North American O-47 observation monoplane. The pilot and radio-operator/gunner were seated above the wing under a transparent canopy while the instructor, navigator and bombardier were housed in a cabin under the wing.
Powered by a 515 hp Hitachi GK2B Amakaze 21 air-cooled radial, the prototype K11W1 made its first flight in November 1942, and the flight trials programm was completed rapidly, as no major problems were encountered. Shortly after the reorganization of K.K. Watanabe Tekkosho into Kyushu Hikoki K.K. , the company received a production contract for the K11W1 which entered service in summer 1943 as the Navy Operations Trainer Shiragiku (White Crysanthemum) Model 11. For armament training the Shiragiku carried a single flexible rear-firing 7.7 mm machine-gun and two 30 kg bombs, but late in the war the aircraft was modified to carry a single 250 kg bomb for Kamikaze sorties.
Development of the Shiragiku led to the K11W2, an all-wood version, which was built in small numbers and saw limited service as a utility transport and  anti-submarine aircraft. Experience with this version led to the design of a specialzed anti-submarine patrol aircraft, the Q3W1 Nankai (South Sea). The Nankai was a two seater retaining much of the structure oft he K11W2 and fitted with redesigned square-tipped tail surfaces, but its development was suspended  when in January 1945 the maiden flight of the single prototype ended in a wheels-up landing (Ref.: 1).

Fighterbomber

Yokosuka D3Y2-K “Myojo Kai” (“Venus Modified”) (Valom)

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TYPE: Dive bomber, trainer, suicide aircraft

ACCOMMODATION: Pilot only

POWER PLANT: One Mitsubishi “Kinsai 62” radial engine, rated at 1,560 hp

PERFORMANCE: 292 mph

COMMENT: The Yokosuka D3Y “Myojo” (“Venus”) was a Japanese two-seat dive bomber/trainer designed and built by the Yokosuka Naval Air Technical Arsenal derived from the Aichi D3A. It was made nearly entirely of wood in an attempt to conserve valuable resources. Upon Japan’s surrender, the project came to a halt with only a few aircraft delivered.
The D3Y was a two-seat bomber trainer constructed of wood, so as not to use more valuable materials. It was based on the successful Aichi D3A, with design starting in late 1942. Like the D3A, it was a two-seat low-winged monoplane with a fixed tailwheel undercarriage. To allow construction by unskilled workers, the elliptical wing and rounded tail of the D3A were replaced by straight tapered alternatives, while the fuselage was lengthened to improve stability. Two prototypes were built during 1944, but these proved heavier than expected. Three production aircraft, which were redesigned to save weight, were completed for the Imperial Japanese Navy Air Force (IJNAF) before the end of the war, and officially designated the Navy Type 99 Bomber Trainer Myojo Model 22.
In Yokosuka’s design bureau two different variants of the basic design were on the drawing board.
The D3Y1-K “Myojo” (Navy Type 99 Bomber Trainer Myojo Model 22) was a two seat wooden dive-bomber trainer. Powered by a 1,300 hp Mitsubishi Kinsei 54 radial engine, based on the Aichi D3A2-K, the aircraft featured some significant changes to allow production in wood. Two prototypes and three production aircraft were completed before the final collaps.
The second design, a single-seat D3Y2-K Special Attacker Myojo Kai (“Venus Modified”) for suicide missions was initiated early in 1945. Powered by a 1,560 hp Mitsubishi Kinsei 62 and fitted with a jettisonable undercarriage on take-off since the aircraft was not expected to return. This version was to have been armed with two 20mm Type 99 MK1 cannon in the engine cowling was to carry a single bomb up to 800 kg. The prototype had not been completed when the war ended, and the planned monthly production of thirty D5Y-1s, as the aircraft had been redesignated, was never undertaken (Ref.: 1, 24).

Fighterbomber, Projects

Kugisho (Yokosuka) R2Y2 “Keiun-Kai”(Airmodel, Resin)

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TYPE: Fast attack bomber

ACCOMMODATION: Crew of two

POWER PLANT: Two Mitsubishi Ne 330 axial-flow turbojet engines, rated at 1,320 kp each

PERFORMANCE: 495 mph (estimated)

COMMENT: In late 1944, Kugisho (a WW II acronym for Dai-Ichi Kaigun Koku Gijitsusho, First Naval Air Technical Arsenal. Kugisho was based at Yokosuka, hence the type is often incorrectly designated Yokosuka) approached the Imperial Japanese Navy (IJN) and informed them that the Yokosuka R2Y1 Keiun‘s airframe was readily adaptable to other roles, including that of a fast attack bomber. To heighten the interest, it was proposed that the Ha-70 10 engine be replaced with two Mitsubishi Ne330 axial flow turbojets, each of the engines being slung under the wings in nacelles. The fuselage space vacated by the Aichi engine would be replaced with fuel tanks. For weapons, the aircraft would carry one 1,800kg bomb and have a cannon armament in the nose. With the introduction of the Ne330 engines, the maximum speed was expected to be 495mph, superior to the projected 447 mph top speed of the Aichi engine model. With these advantages in mind, the IJN approved that work should begin on designing the R2Y2, the turbojet powered “Keiun” which was sometimes referred to as the “Keiun-Kai”, as well as permitting the R2Y1 to be completed as an airframe demonstrator to test the handling characteristics.
Even before the destruction of the first R2Y1, a second example was being constructed and design work for the R2Y2 was underway.
Contemporary sources show no less than four versions for how the R2Y2 may ultimately have appeared. The first version had the Ne330 engines in underwing nacelles. The second version showed the two engines buried within the fuselage with wing root air intakes and narrow jet nozzles. The third version removed the wing intakes and replaced them with a nose intake, but it retained the narrow nozzles. Finally, the fourth version was similar to the third except the engine nozzles were larger.
The first design is considered by most to be the initial R2Y2 concept while the other three are subject to debate. In part, this is due to the fact that the Japanese had very little time to explore various installations of turbojets in airframes. The easiest means to place turbojets on aircraft was by using nacelles and this was seen in the Nakajima “Kitsuka”, Nakajima Ki-201 “Karyu” and proposed Kugisho “Tenga” and Kawanishi K-200.
Even the Germans with their turbojet experience did not fully understand the effects of a long nose intake feeding a high performance jet buried in a combat fighter’s fuselage. Messerschmitt, when they began to study how to start the Messerschmitt Me P.1101 Vl second generation jet fighter, catalogued the obstacles that needed to be overcome. They included the effects of engine operation on the fuselage integrity, ensuring the nose intake was properly positioned and shaped for maximum airflow, making sure the intake tube was made as smooth as possible to minimize air restrictions, how to protect the rear of the aircraft from the heat generated by the exhaust thrust, the effects of reduced airflow on thrust due to flight angles and more. The Germanswere at least able to devote some time to investigating these problems and providing promising solutions to them.
This was time however, that the Japanese simply did not have. Up until the construction of the and the planned Focke-Wulf Ta 183, all of the War time jet designs flown by the Luftwaffe had nacelle mounted turbojets, e.g. Messerschmitt Me 262. The Japanese may not have been made fully privy to the latest German jet engine technology as it pertained to long intakes before the war ended.
It is within reason to suggest that the R2Y2 with the wing root intakes could have been under consideration since it would be a logical development, especially since such intake arrangements were not entirely new. The third and fourth designs may or may not have been post-war conjecture.
Unfortunately for Kugisho and the IJN, the R2Y2 would never be brought to full production. With the end of the war, the second R2Y1 prototype remained incomplete and the R2Y2 would forever remain a design board aircraft

(Ref.: Dyer III, Edwin M.: Japanese Secret Projects, Experimental Aircraft of the IJA and IJN 1939-1945, Midland Publishing, Hersham, U.K., 2010).

Fighter, Projects

Kugisho High-Speed Aircraft Project with DB 601A (Unicraft Models, Resin)

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TYPE: High speed fighter project

ACCOMMODATION: Pilot only

POWER PLANT: One Daimler-Benz DB 601A liquid-cooled engine, rated at 1,159 hp

PERFORMANCE: No data available

COMMENT: Every aircraft creator seeks to reduce drag in their designs. The more drag, the slower the aircraft moves through the air due to the resistance. Drag cannot be completely removed from a design, but even in the early years of aviation various methods for minimizing drag were investigated and many different solutions were tried.
Not surprisingly, such applications were valued by those providing the military with aircraft and in Japan, prior to the outbreak of hostilities with the US, the Dai-lchi Kaigun Kok[ Gijutsu-sho (Yokosuka Naval Air Technical Arsenal, Kugisho) would study such efforts in an attempt to produce fast flying aircraft.
With the war clouds looming on the horizon, the seeds planted by the air racers of the 1920s and early 1930s were germinating in the aircraft used by the air forces of the major powers. Designs by Curtiss for the US Army Air Force were influenced by the Curtiss racers while the retractable landing gear of the 1920 Dayton Wright RB racer would become a hallmark of Grumman aircraft such as the F2F. In Great Britain, R. J. Mitchell would draw heavily from his experience designing Schneider Trophy racers to build the Supermarine Type 300 which would eventually evolve into the Supermarine Spitfire.
On 26 April 1939 German test pilot Fritz Wendel flew to a new world speed record of almost 469 mph with a Messerschmitt Me 209. The Me 209 was solely designed to break speed records and was a completely separate aircraft from the Messerschmitt Bf 109 that entered service with the German Luftwaffe at that time. It shared only its Daimler-Benz DB 601 liquid-cooled engine with the Bf 109.
Consequentially, Japan sought to produce racing aircraft and planes designed to beat world speed records. In 1938, a group of designers sought to produce a high-speed aircraft to challenge the world air speed record. Once war had broken out this aircraft, called the Ken lll, was soon taken over by the Imperial Japanese Army (IJA). Redesignated the Ki-78, its development was continued under Kawasaki. During this time, it may have been the Imperial Japanese Navy (IJN) who decided to conduct its own studies of high speed aircraft with Kugisho assigned the task of doing so. Whether the studies were initiated in response to the IJA’s own high-speed aircraft project is unknown but the prevalent aircraft design philosophy of both the IJN and the IJA prior to the war was of speed, agility and range at the expense of fire- power, durability and protection.
Kugisho examined over half a dozen aspects of aerodynamics in order to produce data on what would be needed to realize an aircraft capable of significant speed. One leading point of research was the main wings. The shape of a wing is one of the more critical aspects of aircraft design. Factors such as wing loading, expected air speeds, angles of attack and the intended use of the aircraft all influence how the wing is shaped. For high speeds, a low aspect ratio wing is often considered. Typically, these are short span wings with the benefits of higher maneuverability and less drag. In addition, having a backward sweep to the wing also lowers drag. The drag most associated with wings is termed induced drag, which is caused by wing tip vortices that change how the air flows over the wings. This change results in less and less lift which then requires a higher and higher angle of attack to compensate and, from this, induced drag results. Elliptical wings offer less induced drag than more conventional straight wings. However, low aspect ratio wings are more prone to larger vortices because they cannot be spread out across a longer wing.
Kugisho’s study on wing shapes was the likely result of testing various airfoils in a wind tunnel to determine their effectiveness and record the results. Another aspect Kugisho engineers reviewed were the merits and flaws of using either an inline or a radial engine and how each type reduced the form drag. In both cases the engineers drew up two concept aircraft and each made use of streamlining. Streamlining is the process of shaping an object, in this case, a fuselage, to increase its speed by reducing the sources of drag.
One concept used the German 1,159hp Daimler-Benz DB 601A, a 12-cylinder, inverted-V, liquid-cooled, inline engine. This engine would be license built for the IJN as the Aichi AEl Atsuta (the ‘A’ stood for Aichi, ‘E’ for liquid-cooled and ‘l’ for first liquid-cooled engine.  Atsuta was a holy shrine in Aichi Prefecture) and for the IJA as the Ha-40, before it was renamed the [Ha-60] 22.
The second concept aircraft (Kugisho High-Speed Aircraft Project with NK-1B) used a 1,000hp Nakajima NKlB Sakae 11 which was a 14-cylinder, air-cooled, radial engine. This engine was a license version of the French Gnome-Rhone l4K Mistral Major (in engine nomenclature, the ‘N’ was for Nakajima, ‘K’ for air-cooled, ‘1’as the first air-cooled engine, while the ‘B’ was for the second version of the NKl; Sakae means prosperity in Japanese).
Kugisho would use the same basic airframe for the engine study. It consisted of a well streamlined fuselage with the pilot mounted in a cockpit set behind the wing and just forward of the vertical stabilizer. This style was found in a number of racing aircraft such as the American GeeBee Rl and Geebee Z. Both aircraft used a standard tail-sitter configuration for the landing gear. The concept equipped with the DB 601A engine had a fuselage shape that was not unlike the Kawasaki Ki-61 Hien (“Swallow”, codenamed “Tony” by the Allies) which would appear in prototype form in December 1941 . The wings were mounted low on the fuselage. The fuselage appearance was due to the inverted-V engine which, by design, offered lower height, weight and length when compared to more conventional engines.
By contrast, the concept using the Nakajima NKlB had a more ovoid fuselage shape, the result of the height of the radial engine. To maintain the aerodynamic streamlining a large spinner was used. Also, in contrast to the DB 601A equipped design, the wings were mounted mid-fuselage.
Kugisho would not produce any direct prototype aircraft from either concept. lnstead, results of the various studies were likely kept available as reference for engineers to access as a means of obtaining data on the aerodynamic problem. Perhaps Kugisho in hindsight considered themselves fortunate to not have expended additional expense and effort in producing working prototypes given the failure of the IJA’s Kawasaki Ki-78, a program that lingered on into 1944 and never met its design goals (Ref.: Dyer III, Edwin M.: Japanese Secret Projects, Experimental Aircraft of the IJA and IJN 1939-1945, Midland Publishing, Hersham, U.K., 2010).

Reconnaissance, Trainer, Observation

Nakajima E8N2 ‘Dave’, Training Unit, Kyushu (Wings Models, Vacu-formed)

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TYPE: Ship-borne reconnaissance floatplane, Trainer

ACCOMMODATION: Crew of two

POWER PLANT: One Nakajima Kotobuki 2 KAI 2 radial engine, rated at 630 hp

PERFORMANCE:  186 mph

COMMENT: The Nakajima E8N was developed as a replacement for the same company’s E4N and was essentially an evolutionary development of the earlier type, with revised wings of lesser area and taller tail surfaces. Seven prototypes were constructed, under the company designation MS, first flying in March 1934. These were duly engaged in comparative trials against competitors from Aichi and Kawanishi.
The MS was ordered into production, designated Navy Type 95 Reconnaissance Seaplane Model 1 in October 1935. A total of 755 E8Ns were built by Nakajima and Kawanishi, production continuing until 1940. Operating as a catapult-launched reconnaissance aircraft the E8N was subsequently shipped aboard all the capital ships then in service, battleships, cruisers and aircraft tenders. It was used successfully in the Second Sino-Japanese War and distinguished itself on several occasions by destroying opposing Chinese fighters. Occasionally the aircraft was operated as a dive-bomber but was more often employed as a reconnaissance and artillery spotting aircraft.
One E8N was purchased in early 1941 by the German Naval Attaché to Japan, Vice-Admiral Wenneker, and dispatched on board “KM Münsterland” to rendezvous with the German auxiliary cruiser “Orion” at Maug Island in the Marianas. The meeting occurred on 1 Feb 1941, and “Orion” thus became the only German naval vessel of the Second World War to employ a Japanese float plane.
Some aircraft remained in service with the fleet at the outbreak of the Pacific War, and one flew reconnaissance from the battleship Haruna during the Battle of Midway. The type was coded “Dave” by the Allies. Later, they were replaced by more modern aircraft such as the Aichi E13A and the Mitsubishi F1M and the remaining aircraft were reassigned to second-line duties for instance communications, liaison and training (Ref.: 24).

Reconnaissance, Trainer, Observation

Kawanishi E7K2 (“Alf”), (Tamiya)

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TYPE: Reconnaissance floatplane

ACCOMMODATION: Crew of three

POWER PLANT: One Mitsubishi “Zusei” 11 radial engine, rated at 870 hp

PERFORMANCE: 171 mph

COMMENT: The Kawanishi E7K was a Japanese 1930s three-seat reconnaissance floatplane. It was allocated the reporting name “Alf” by the Allies of WW II.
In 1932 the Imperial Japanese Navy requested the Kawanishi Aircraft Company to produce a replacement for the company’s Kawanishi E5K. The resulting design, designated the Kawanishi E7K1, was an equal span biplane powered by a 620 hp “Hiro Type 91W-12 liquid-cooled inline engine. The first aircraft flew on 6 February 1933 and was handed over to the navy for trials three months later. It was flown in competition with the Aichi AB-6 which was designed to meet the same 7-Shi requirement. The E7K1 was ordered into production as the Navy Type 94 Reconnaissance Seaplane and entered service in early 1935. It became a popular aircraft, but was hindered by the unreliability of the “Hiro” engine. Later production E7K1s were fitted with a more powerful version of the “Hiro 91”, but this did not improve the reliability. In 1938 Kawanishi developed an improved E7K2 with a Mitsubishi “Zuisei 11” radial engine. It first flew in August 1938 and was ordered by the Navy as the Navy Type 94 Reconnaissance Seaplane Model 2. The earlier E7K1 was renamed to Navy Type 94 Reconnaissance Seaplane Model 1.
The type was used extensively by the Japanese Navy from 1938 until the beginning of the Pacific War, when E7K1 were relegated to training duties but the E7K2, despite their obsolescence, remained in first-line service until 1943. The aircraft was initially used for convoy escort, anti-submarine patrol and reconnaissance. Later in the war, the E7K2s were retained in the liaison and training role and as mother aircraft for the MXY4 radio-controlled target plane. Also both versions were used in Kamikaze operations in the closing stages of the war (Ref.: 1, 24).

Trainer

Yokosuka K5Y2 (“Willow”)

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TYPE: Intermediate trainer

ACCOMMODATION: Crew of two

POWER PLANT: One Hitachi “Amakaze” radial engine, rated at 300 hp

PERFORMANCE: 132 mph

COMMENT: The Yokosuka K5Y2 was a two-seat unequal-span biplane trainer (Allied reporting name “Willow”) that served in the Imperial Japanese Navy during World War II. Due to its bright orange paint scheme (applied to all Japanese military trainers for visibility), it earned the nickname “Red dragonfly”, after a type of insect common throughout Japan.
The aircraft was based on the Yokosuka Navy Type 91 Intermediate Trainer, but stability problems led to a redesign by Kawanishi in 1933. It entered service in 1934 as Navy Type 93 Intermediate Trainer K5Y1 with fixed tail-skid landing gear, and remained in use throughout the war. Floatplane types K5Y2 and K5Y3 were also produced. After the initial 60 examples by Kawanishi, production was continued by Watanabe (556 aircraft built), Mitsubishi (60), Hitachi (1,393), First Naval Air Technical Arsenal (75), Nakajima (24), Nippon (2,733), and Fuji (896), for a total of 5,770. These aircraft were the mainstay of Imperial Japanese Navy Air Service’s flight training’s, and as intermediate trainers, they were capable of performing demanding aerobatic maneuvers. Two further land-based versions, the K5Y4 with a 480 hp “Amakaze” 21A engine and the K5Y5 with a 515 hp “Amakaze” 15, were projected but never built.
A K5Y of the Kamikaze Special Attack Corps 3rd Ryuko Squadron was credited with sinking the destroyer USS Callaghan on July 29, 1945, the last US warship lost to kamikaze attack during the war (Ref.: 24).

Trainer

M6A1-K “Nanzan” (“South Mountain”), (‘Shisei-Seiran Kai), (MPM-Models)

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TYPE: Trainer aircraft for Aichi M6A1 “Seiran”

ACCOMMODATION: Pilot and trainer

POWER PLANT: One Aichi Atsuta Type 32 liquid-cooled engine, rated at 1,400 hp

PERFORMANCE: 310 mph at 17,060 ft

COMMENT:  The Aichi M6A1-K “Seiran Kai” was a trainer version of the submarine-launched attack floatplane Aichi M6A1 “Seiran”. It was fitted with an inwardly-retracting undercarriage, and the folding tip of the rudder was dispensed with as the absence of floats improved directional stability. The popular name of the M6A1-K was later changed to “Nanzan” (Southern Mountain”).
Two prototypes of this aircraft were built and flight tested before the war in the Pacific ended in 1945 (Ref.: 24).

Fighter

Mitsubishi A7M2 “Reppū” (“Strong Gale”, “Sam”), (MPM Models)

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TYPE: Carrier-borne and land-based fighter

ACCOMMODATION: Pilot only

POWER PLANT: One Mitsubishi Ha-43 radial engine, rated at 2,200 hp

PERFORMANCE: 390 mph at 21,660 ft

COMMENT: Towards the end of 1940, the Imperial Japanese Navy asked Mitsubishi to start design on a 16-Shi carrier-based fighter, which would be the successor to the carrier-based Mitsubishi A6M “Rei-sen” (“Zeke”, Allied reporting code “Zero”). At that time, however, there were no viable high-output, compact engines to use for a new fighter. In addition, Mitsubishi’s design’s team was preoccupied with addressing early production issues with the A6M2b as well as starting development on the A6M3 and the 14-Shi interceptor which would later become the Mitsubishi J2M “Raiden” (Allied code “Jack”), a land-based interceptor built to counter high-altitude bombers). As a result, work on the “Rei-sen” successor was halted in January 1941.
In April 1942, the development of the A6M3 and the 14-Shi interceptor was complete, and the Japanese Navy once again tasked Mitsubishi with designing a new “Zero” successor to become the “Navy Experimental 17-Shi Ko (A) Type Carrier Fighter “Reppu” (“Strong Gale”, Allied reporting code “Sam”). In July 1942 the Navy issued specifications for the fighter: it had to fly faster than 397 mph above 20,000 ft, climb to 20,000 ft in less than 6 minutes, be armed with two 20 mm cannon and two 0.51 in machine guns, and retain the maneuverability of the A6M3 “Rei-sen”.
As before, one of the main hurdles was engine selection. To meet the specifications the engine would need to produce at least 2,000 hp, which narrowed choices down to Nakajima’s NK9 (Ha-45) under development (later becoming “Homare”), or Mitsubishi’s MK9 (Ha-43), which was also still being developed. Both engines were based on 14-cylinder Nakajima “Sakae” and Mitsubishi “Kinsei”, respectively) engines converted to 18-cylinder power plants. The early NK9 had less output but was already approved by the Navy for use on the Yokosuka P1Y “Ginga” (Allied code “Frances”), while the larger MK9 promised more horsepower.
With the larger, more powerful engine, wing loading became an issue. With the MK9 the engineers concluded it could fulfill the requirements; however, production of the MK9 was delayed compared to the NK9, and the Japanese Navy instructed Mitsubishi to use the NK9.
Work on the 17-Shi was further delayed by factories prioritizing Mitsubishi  A6M “Reisen” and Mitsubishi G4M (Allied code “Betty”) bomber production as well as further work on A6M variants and addressing Mitsubishi J2M “Raiden” issues. As a result, the 17-Shi, which became the A7M1, officially flew for the first time on 6 May 1944, four years after development started. The aircraft demonstrated excellent handling and maneuverability, but was underpowered as Mitsubishi engineers feared, and with a top speed similar to the A6M5 “Rei-sen”/”Zeke”. It was a disappointment, and the Navy ordered development to stop on 30 July 1944, but Mitsubishi obtained permission for development to continue using the Ha-43 engine, flying with the completed Ha-43 on 13 October 1944. The Mitsubishi A7M2 “Reppu” now achieved a top speed of 390 mph, while climb and other areas of performance surpassed the “Zero”, leading the Navy to change its mind and adopt the aircraft. The A7M2 “Reppu” was also equipped with automatic combat flaps, used earlier on the Kawanishi N1K-J “Shiden” (Allied code “George”), significantly improving maneuverability.
In June 1945, ace pilot Saburo Sakai was ordered to Nagoya to test the airplane. He declared it to be the fastest fighter he had ever seen, able to surpass anything on the air, Japanese or American. He claimed it could fly in circles, while ascending, around a Grumman F6F “Hellcat” or a North American P-51 “Mustang”, and that engineers stated it could fight at up to 39,370 ft.
When the war in the Pacific area ended a total of 10 Mitsubishi A7M “Reppu’s” were built including only one production aircraft A7M2 (Ref.: 24).