Kawanishi E7K “Alf” (1933)

Kawanishi E7K “Alf” (1933)

Imperial Japanese Navy, 533 built

IJN main cruiser reconnaissance floatplane in 1941

In 1932, the Imperial Japanese Navy requested Kawanishi Aircraft to replace its previous E5K (1931) as part of the 7-Shi requirement. The new design was designated E7K1, powered by a 462 kW (620 hp) Hiro Type 91 W-12 inline engine to reach better speed. The first flew on 6 February 1933 already, trialled by the Navy in May, competiting with the Aichi AB-6. The E7K1 was accepted based on better performances overall, and ordered as the Navy Type 94 Reconnaissance Seaplane (九四式水上偵察機), entering service by early 1935. A popular aircraft despite the unrelliable liquid-cooled Hiro engine, the production swapped on an improved Hiro 91, which was still unreliabe. At last in 1938 Kawanishi introduced the E7K2 with a Mitsubishi Zuisei 11 radial, far more reliable and powerful. This brand new variant first flew in August 1938, ordered soon as the “Navy Type 94 Reconnaissance Seaplane Model 2”, the E7K1 being renamed Model 1 retrospectively.

Aboard IJN Abukuma, 1941
The E7K was deployed from 1936 (Model 1) over China, and until the Pearl Harbor. The E7K1 was versed in second-line duties, notably training, while the E7K2 fought on first line until 1943, some even ending as kamikaze in 1945. It was often compared to the Nakajima E8N, but the latter was a smaller type, main battleship model for artillery spotting. In countless engagements, the main reconnaissance model was the Kawanishi E7K2 catapulted by IJN cruisers. It even motivatied the conversion of entire cruisers like the Mogami as hybrid seaplane carriers, or construction of the Tone class.

Design Development of the E7K

The failure of the Navy E5Y Project

In early 1932, it became apparent to the Imperial Japanese Navy Staff that replacing the ageing 14 E1Y2 long-range shipborne reconnaissance aircraft was now urgent. There was already a specification emitted and answers, but none was considered worthy of a production, despite combined efforts of Aichi, Kawanishi and Nakajima under Yokosuka state arsenal supervision. Thus work had been going on from 1928 to 1931 with little to show for it. The Navy Type 90-3 E5Y1 indeed failed to meet requirements and was barely superior to its predecessor. In the end, the admiralty choose instead to stick to a modified version of the Type 14 long-range reconnaissance aircraft, known as Aichi E1Y3. This was temporary however, and the technical department of the Kaigun Koku Hombu Fleet Air Headquarters started a new design competition open to all manufacturers. This ended the policy of state-design models. From now on until 1945, competition (“Shisaku Seizo” or “shi”) between manufacturers became the norm rather than cooperation.

From now on all these open competition would had “Shi-” added to a numerical prefix with the development year from the Showa era (1926) and the first of these was 6-Shi in 1931. The same year it was to address the need for a night flying boat, a carrier-based dive bomber and two-seat carrier-based bomber. They led to nowhere, but in 1932 7-Shi became the most ambitious and largest od such programs, with a carrier-based fighter, torpedo bomber, dive bomber, carrier-based heavy strike aircraft, ground bomber, long-range shipborne reconnaissance aircraft, the project which concerns us.
The latter was proposed to Kawanishi and Aichi, which had good knowhow with long-range reconnaissance aircraft and were familiar with E5Y/E5K project issues.
Aichi developed the eye-pleasing AB-6 with an enclosed cockpit, wing fairings and slats but all these innovations prevented to play on the essentials and this one lost as a competitor to Kawanishi.
The latter surprise all since the company since then had not produced a single successful military project, having exerted its meagre talents until then on the civil market. It had to acquire licence of floats and floatplaned for others to gain experience.

About Kawanishi

Kawanishi was founded by Seibei in 1918, alongside Chukuhei Nakajima, which cooperated for a year before departing their own way in 1919. “Kawanishi Kikai Seisakusho” starting the production of machine tools for the textile industry at first. Apparently Chukuhei Nakajima’s behaviour angered many of his talented engineers which left Nakajima and followed Senbei Kawanishi, and this included the director Eiji Sekiguchi, engineers Fujio Togawa, Konoshin Tamaki, and test pilot Yukichi Goto. Thanks to this, an aviation department was created and work started of the first models.
From 1922 the commpany was managed by Ryuzo Kawanishi and completely switched to aviation. Eiji Sekiguchi succeeded in having several projects of transport aircraft built for the civilian market, and the company tried, but failed to be retained in a carrier-based fighter program. The K-11 was unsuccessful but the company purchased E2N1, E4N2, E5K1 and other floatplane models for tests. When it came, the Company, which gained considerable experience of the years, felt ready to address the new 7-Shi long-range reconnaissance floatplane.

Detailed Design

The design of “Type J” (factory designation) was fairly conservative in comparison of the Aichi model. The forward section was cladded in duralumin, the rest was covered with linen with separate duralumin inserts on the hood and cockpit. It was designed to be powered by the Type 91 W-12 cyclinders, in-line engine which was part of the 7-Shi specs, a licenced verison of the French W12 Lorraine-Dietrich, made by Hiro as the 12Eb in the 11th fleet arsenal. This new engine developed 500 hp and up to 620 at takeoff speed. It was coupled with a two-bladed wooden constant-pitch propeller.

The nose was moved quite far forward due to the lenght of the engine, as behind were located a large fuel and oil tanks, as range was a priority. The propeller was so well forward that the propeller arc reached the tip of the floats. There were open separate cockpits for the pilot, navigator and gunner-observern the latter installed back to back in a small space. This eased somewhat communication. Both the pilot and navigator had plexiglas visors while the navigator had a duplicated aircraft dashboard, with simplified instrumentation, but no double command. The gunner’s seat was recessed eneough so that in stowed position he did not protrude up. He moved on a folding seat and higher position to fire with the flexible-mounted machine gun. A second machine gun was located on a retractable bracket in the lower hatch installation, to protect the floatplane’s belly. To be fired, the gunner folded the seat and lied down at the bottom of the fuselage.

The main structure called for a single-keel scheme without additional braces and struts. It was reinforced enough to withstand the stress of taking off from a catapult, and manipulations when recovering it at sea. As a biplane or equal span wings, both 14 meters in all, procured stability and lift. Wing consoles were connected by N-shaped struts. The upper wing was slightly forward compared to the lower one, and attached to the fuselage with N-shaped struts. The lower wing received extra reinforcement structs connected to the fuselage and the biplane could fold back on hinges along the fuselage, easing storage. Its landing gear comprised two floats attached at four points on large legs, reinforced by X type bracing. This was sturdy and reliable combination, if not not innovative. But if the structure was sound, it will soon appear that the choice of engine, based on paper performances, was less than ideal.

First flight of the protoype

The prototype “Type J” flew on February 6, 1933. Tests went on at Kawanishi until May 1933, after which it was handed over to the fleet’s commission for comparative testing with its rival Aichi AB-6. The provisional armament were two Type 92 machine guns, lower and upper position aft and a single Vickers synchronized MG on the hood. A standard bomb rack was installed underbelly, able to carry up to four 30-kg or two 60-kg bombs. This was not bad for a reconnaissance model, enabling extra capabilities.
Comparative tests took place at the Yokosuka Kokutai base, and lasted for a year. Both performed equally, although Kavanishi’s mode proved a little faster and easier to pilot. The Aichi model shone in takeoff and landing characteristics only. The Navy preferred the Kawanishi prototype and asked to improve the model on some points for new tests.

Second protoype (1934)

By April 1934, Kawanishi presented a second prototype, designated already “Long-range reconnaissance hydroplane Type 94 model 1”, simplified as E7K1. By May, after new tests, the technical department of the Kaigun Koku Hombu fleet concluded the Kawanishi reconnaissance aircraft was a definitive choice, accepted for production.

Production of the E7K1

It wa the first model of the new Kawanishi plant created near the village of Naruo, halfway between Osaka and Kobe. The first serial model had the very same engine as the prototype, soon replaced by an improved version Hiro Type 91 model 2 rated for 750 hp on takeoff, 600 hp normal use. It was connected to a four-bladed fixed-pitch wooden propeller. The Vickers foward machine gun was removed, but it seems a telescopic sight was kept.
Production was set up for a first run at the end of 1934. In 1935, the Sugita “Nippon Hikoki K.K.” plant was chosen to join serial production. In total until 1937, 183 E7K1 were assembled (57 for Nippon Hikoki K.K.).
By the fall of 1937, the model was stopped due to obsolescence. However next specifications would fail to procure a suitable replacement, delayed, and it was decided to resume production of Type 94 biplane based solely on reliability, although with engine issues.

Development of the E7K2

By early 1938, an improved version was developed called ‘Type 94 model 2’, later known as E7K2. The airframe and fuselage were kept unchanged but it was chosen to replace its relatively temperamental older and less powerful engine by a brand new air-cooled Mitsubishi 14-cylinder MK2A Zuisei 11, 28 liters in capacitt. It was probably the most successful Japanese aircraft engine of the time, adopted by the Navy and army as Ha-26. Output on takeoff rose to 875 hp. The modified version prototype first flow in August 1938 and was immediately authorized for production. Flight performance was still in the same vein, albeit a better speed, and moreover much greater reliability and service life. In fact this new version was so successful, greater orders were placed and it constituted overall the bulk of the E7K production.

Production went on until November 1939 with a scheduled replacement at last by the monoplane E13A1 in the same rile when finally adopted. Both Kawanishi and Nippon Hikoki, K.K. delivered respectively 288 and 60 E7K2, for a total of 348, compared to 183 for the E7K1, and a total overall of 531 units, whereas other sources states 533 (indeed with the two prototypes).
By the fall of 1939, the model was nevertheless outdated and only stayed frontline due to the lack of replacement, as the new E13A needed time for production to be stepped up. The E7K1 with the Hiro Type 91 engine was meanwhile sidelined to training.

Despite its age, the E7K was nevertheless popular with its crews and pilots for an excellent handling, good visibility overall, and for the Navy, their great autonomy, which was paramount to create a wide reconnaissance area around the fleet. Each cruiser carried indeed from two to four of them, sometimes even more, like the Tone class. A classic squadron of cruiser (four) was indeed capable of sending a total of eight in the air at all times, probing all directions.


E7K1: Production version with a Hiro Type 91 520 hp water-cooled W-12 engine, 183 built (including 57 built by Nippon Hikoki K.K.)
E7K2: Re-engined version with a Mitsubishi Zuisei 11 radial engine, about 350 built (including 60 built by Nippon Hikoki K.K.)

E7K2 1938

Crew: 3: Pilot, Observer, Rear gunner
Fuselage Lenght 10.41 m (34 ft 2 in)
Wingspan 14 m (45 ft 11 in)
Wing area 43.6 m2 (469 sq ft)
Height 4.85 m (15 ft 11 in)
Empty weight: 2,100 kg (4,630 lb)
Gross weight: 3,300 kg (7,275 lb)
Propeller: 2-bladed metal propeller
Engine: Mitsubishi MK2 Zuisei 11, 14-cyl AC radial 650 kW (870 hp) TO
Top speed: 276 km/h (171 mph, 149 kn) at 2,000 m (6,562 ft)
Cruise speed: 185 km/h (115 mph, 100 kn) at 1,000 m (3,281 ft)
Climb rate: 3,000 m (9,843 ft) in 9 minutes 6 seconds
Climb rate: 3,000 m (9,843 ft) in 9 minutes 6 seconds
Service ceiling: 9,800 m (32,200 ft)
Wing Loading: 75.7 kg/m2 (15.5 lb/sq ft)
Power/mass: 0.196 kW/kg (0.119 hp/lb)
Armament: MGs 3: fixed Type 97 Vickers fwd, 2× trainable 7.7 mm Type 92 Lewis gun ventral/dorsal
Bombs and other Payloads 120 kg (264.6 lb) of bombs

Active service

E7K in flight, with a E8N in the background
By the end of 1935, the E7K1 had completely replaced the previous model in the fleet, paired with Nakajima E8N. Battleships were sometimes provided the E7K in complement. Two however were on board all heavy cruisers, and one per light cruiser. They were not distributed to tenders or seaplane carriers although a few E7K were distributed to the Kamikawa Maru, Kimikawa Maru, Kiyokawa Maru, Kunikawa Maru, Kagu Maru, and Kinugasa Maru as organic reconnaissance model. However the Navy staff preferred smaller models, and the E8N was still chosen over the E7K. Coastal air bases also were provided a few E7Ks. The baptisme of fire started with the 2nd Sino-Japanese incident by August 1937. Seaplane tenders took part in cooastal operations but mainly deployed the Nakajima E8N.

By August 14, 1937, the Japanese air forces launched long range raids and deep penetration, but the Chinese Air Force retaliated with around 40 Northrop “Gamma” escorting by Curtiss “Hawk” III fighters. They directly headed for the headquarters of the Japanese 3rd Fleet, in Shanghai. There was no defence left in the area and and later local E7K reconnaissance from the flagship of the 3rd fleet and from the old Izumo plus a single E8N from IJN Sendai were launched and tried to counter these.
The armored cruiser Izumo lost its E7K even before gaining altitude, but this allowed a diversion and the E8N from Sendai shot down one Hawk III. The E7K1 was also used for bombing missions, but with limited success.

On September 19, 1937 (offensive on Nanking), Eight E7K from the Maizuru kokutai took off with bombs to attack a Chinese convoy on the outskirts, intercepted by a single Boeing P-26 “Peashooter” from the 17th Squadron, 3rd Group (Captain Wong Sun Shui), but could shot down none, repelled by concentrated fire from the Japanese gunners. The convoy was bombed and two armored vehicles, 9 trucks were reported destroyed. Those from Chinkai Kokutai (Korea) patrolled the blockade of the Chinese coast and Yellow Sea, and attacked targets of oppurtunity.

By December 1942, the E7K2 started to be withdrawn but they were still used by coastal units and the “Alf” served in the Hataka kokutai in Kure, totalling 54 E7K2s and 48 short-range E8N2s. In Korea, Chinkai Kokutai operated six, as in in Yokosuka Kokutai. Eight E7K2 served also in Komatsujima kokutai (Aichi Prefecture), six with Maizuru kokutai, six with the 18th Kokutai (Saipan), 10 with the 19th Kokutai (Kwajalain) at the time of Pearl Harbor and afterwards.
E7K2 served until early 1943 both declining due to numbers shot down, replaced, or simply worn out. Surviving E7K2 ended in turn with training units, replacing the K1. Experiments were done, like towing the Kugisho MXY3 target glider or radio control the MXY4. In the latter case, it was launched from a special ramp on the upper wing. By June 1943 in Niihama near Kure was created the “Takuma Kokutai” to train floatplane crews with the E7K2. It operated until September 1944 but was reorganized and fusioned with Yokohama kokutai with a mix of H8K “Emily”, Aichi E13A “Jake” to form a combat unit, and the largest hydroaviation base in Japan. Their task was combat patrols around the Home Islands.

By February 1945, the same unit was modified to form Special Attack units at Takuma base. They were turned into kamikaze to attack US Forces at Okinawa. The Squadron “Kotohira Suishin” comprised E7K2s modified to be equipped with a new rack capable of holding a 250-kg bomb. By April 1945, four suicide attacks saw the entire Takuma Kokutai wiped out even before reching its objective. They were spotted by radar and intercepted by hordes of F6F and F4U, all easy meat before even approaching their fleet. The remainder were sold for scrap and none survived in any museum.

Read More

On alchetron.com
on airwar.ru
On ww2aircraft.net/
On valka.cz
on combinedfleet.com
On aviastar.org
On ipms-sg.ch
on pacificeagles.net/
On wikipedia.org

Model kits



Basic early production Type 94 Type 1, 1935

E7K1 Navy Air Base Chiyoda, Tokyo, 1939

E7K1, Seaplane Carrier Kamoi, 1937

E7K1 Tateyama Kokutai, 1940

E7K2 in 1939

E7K2 on IJN Abukuma, 1941

E7K2 model 2 on IJN Sendai, 19 December 1941, invasion of Malaya. That day she detected and reported the Dutch submarine O-20, later sunk by destroyers.

E7K2 on IJN Kashii, Burma, 1942

E7K2 from Kashuwa Kokutai, Chiba Preferecture, Japan, 1943


In a Russian publication src

E7K and E8N in flight together, the main spotter-reconnaissance models of the IJN in 1940

E7K2 on a catapult immat. UI-I, from one of the Nagara class cruisers.

The same, different angle, colorized by Irootoko jr.

E7K in flight. All: CC

Mitsubishi A6M Zero “Zeke”

Mitsubishi A6M Zero “Zeke” (1939)

Imperial Japanese Navy, 10,939 built

The legendary Japanese fighter

Just named colloquially “zero” and still popularly known as such today, the A6M, or “Mitsubishi Navy Type 0 carrier fighter” (零式艦上戦闘機) hence the number used as nickname, was the brainchild of superstar aviation designer Jiro Horikoshi. A superb dogfighter, combined with perhaps the best trained naval fighter pilots of the world’s at the time, achieved total air dominance in the Pacific until 1943.

With 10,939 delivered by Mitsubishi, Nakajima and other plants, it was also the most ubiquitous of all WW2 Japanese models, soldiering over a very large area, between aircraft carriers and land bases, from Mandchuria to New Guinea, Malaysia to the Aleutians. The A6M gained an aura of invincibility in the first year of the war, brushing aside all opposition. This was the result of a number of factors, but its advantages became problems when the allies started to field better planes in 1944-45. It’s designated successor, the A7M Reppū never had the time to replaced it, but the A6M went through several iterations and variants to correct its known issues.

A6M2 in 1940

Design development

A successor to the A5M “Claude”

The A5M “Claude” was the Imperial Japanese navy main monoplane fighter in 1939, a 1st generation model, also designed by Horikoshi with elliptic wings and modern features, all metal fuselage but still antiquated ones, like fixed undecarriage and open cockpit. It was already a superb dogfigher, putting agility over all else. But in 1939, with a more serious opposition over China, pilots started to recoignise its limitations.

This process started early on: The Mitsubishi A5M fighter was just entering service in early 1937, when its replacement was already discussed. On 5 October 1937 was signed and published “Planning Requirements for the Prototype 12-shi Carrier-based Fighter” (or simply “12-shi spec”), sent to Nakajima and Mitsubishi to submit proposals. Both firms started preliminary design work, whereas requirements were still awaited. They were stn in the following months.

A5M4 onboard IJN Soryu in 1941
A5M4 onboard IJN Soryu in 1941

Genesis context

It happened that the the Japanese Navy was an early pioneers in carrier-borne fighter aircraft with Hosho preceding Argus by months, and fielded the Type 10 fighter, world’s first designed fighter for carrier operation while others were still adapted land-based models. The Type 3 fighter or A1N1 (a Nakajima copy of the Gloster Gambet) while in service, was followed by the 1931 Nakajima Type 90 (A2N) and 1935 Type 95 (A4N), faster but less agile.

So Mitsubishi was left out of the loop for about ten years before going back for the Type 96 A5N(A5N), first all-metal monoplane fighter, while Nakajima, which competed for the same, basically created a copy for the army, the Ki-27. Soon despite initial reserve, pilots found the apparent superiorority of the A5M in 1937 over all opposition. This new model gave Japanese designers, engineers and craftsmen a valuable experience, this time more and more decoupled from Western designs, with new techniques.

Among key points were how to minimize drag and obtain flush riveting, all sorts of weight saving measures without compromising rigidity, plus the ideal installation of radial engines into a new, high-speed, stressed skin all-metal airframe undergoing no short amount of streamlining at any level. The Type 96 (A5M) entered serviced just as a war in China broke and the Navy soon realized its limited range,n which became the main focus for the next replacement. The idea was to lead deeper penetrations for longer and more efficient escort missions into China as the war progressed. It was also realized that the Type 96 would soon be obsolete compared to upcoming Western Models; After all, both the spitfire and Me-109 emerged in 1935 already.

Other key points were the need for a retractable landing gear and heavier firepower, as the A5M two light machine guns were WW1 standard, rather puny compared to the opposition. Pilots complained about the time they needed to best their opponents in a dogfight. Examination of carrier versus land performance for a dedicated model also brought concerns in the Japanese Naval Command about theory and practice in their new and young tool, naval aviation.

To the traditional roles, reconnaissance, defence, spotting and harrassing until the big-guns battleships arrive to finish the job, was a position already dubious at the end of WWI World War 1 but still prevalent among Naval powers. So based on multiple naval games held by the academy and officers, the IJN soon realized that by having a fully independent arm from the army air force would help them reaching their goals more heavily. Without some legal cluttering or hampering capabilities and types, securing air superiority well beyond the reach of naval artillery thanks to a long range, became a main priority, not only for the attack aicraft of the nex generation, the B5N/D3A, but it’s escort, even reinforcing the idea of longer range could be useful for a fighter in open seas. Overall in 1937-38 these new doctrines, further pushed forward by Yamamoto and other promoters in the Navy versus traditionalists, made the Japanese Fleet Air Arm arguably the world’s best, years ahead of other nations. They clearly demonstrated this superiority in all engagements until 1943. Based on these experiences and discussions came the 1937 specifications 12-Shi:

Specification 12-shi (October 1937)

The design staff started with early combat reports of the A5M in China. From there, the IJN specified updated requirements, in October 1937. These were calling for:

  • A speed of 270 kn (310 mph; 500 km/h) at 4,000 m (13,000 ft)
  • A climb to 3,000 m (9,800 ft) in 9.5 minutes.
  • An endurance (With drop tanks) of two hours in normal regime
  • 6-8 hours at economical cruising speed.
  • A better armament with two 20 mm cannons and two 7.7 mm (.303 in) MG plus two 60 kg (130 lb) bombs.
  • A complete, modern radio set
  • A Radio direction finder for long-range navigation.
  • Maneuverability at least equal to the A5M
  • A wingspan below 12 m (39 ft) to fit in aircraft carriers hangars.

What’s amazing beyond the numbers, is that these figures were not only unheard carrier-borne fighter, demanding speed, rate of climb and armament, they were equal or superior to any land-based fighters, and cherry on the cake, were coupled with the world’s best range, several fold above all competition and usually proper to bomber, mixed with (which was contradictory) with exceptional agilty (how to reconcile the weight of extra avgas and lightness ?). Mitsubishi was apparently not afraid of the task, and entristed again Jiro Horikoshi to form a dream team of engineers, to study this seemingly impossible proposal. Nakajima which was the natural contender was quick in its reaction after reading these and said the Navy’s demands were impossible, pulling out of the competition right away.

Nakajima’s out, Mitsubishi takes up the gauntlet (April 1938)

Ki-43 first prototype. It would fly first on January 1939. Note, i can’t find any photo for markings;

Nakajima’s team considered these new requirements impossible and pulled out outright in January 1938. However this must not fool us into thinking this was the official reason. Instead at the time, they looked towards a larger and more lucrative army contract, notably the awaited successor of the Ki-27 “Nate”, which would evolved into, here again, a model relatively similar to the “Zero”, the equally legendary Ki-43 Hayabusa (“Oscar”) (see later). And the agility of the latter even surpassed the A6M, but true, with a far lesser range and not the constraints of a carrier-based model. Both branches would have their respective champion.

Meanwhile, Mitsubishi’s chief designer Jiro Horikoshi, believed the requirements could be met. His take on the matter as that weight saving was to be the ultimate objective of the design. His team basically sat day and night, trying to eliminate every possible elements, replacing it by a lighter solution. Every weight-saving measure was incorporated into the design, requiring also a lot of “out-of-the box” thinking, notably by simplifying parts. Therefore, it at first the team (before having the complete specs) worked on a retractable undercarriage, enclosed cockpit version of the A5M with the latest engine, it was soon clear that very little of the former model could be reused, if at all.

Horikoshi at first simply retained and strengthened his former Type 96 design team with Yoshitoshi Sone and Teruo Tojo for the calculations, Brothers Sone and Yoshio Yoshikawa the structural work, Denichiro Inoue and Shotaro Tanaka the powerplant installation, Yoshimi Hatakenaka the armament plus equipment, Sadahiko Kato and Takeyoshi Mori the landing gear and its equipment. They selected the in-house Mitsubishi MK2 Zuisei 13, capable of delivering 875hp.

The pilot controversy (April-May 1938)

IJN Shokaku pilots in 1941

On April 10, 1938, a draft design of a new fighter sparked a lively discussion around technical decisions to made by designers, and terms of reference itself. Conservative pilots criticized the closed cockpit, arguing that it would severely restrict visibility while pilots managed to convince earlier Mitsubishi designers to also renounced it for the A5M2b modification, mostly to allow the pilots to look over the side of the cockpit forward, to find the correct glide path.

Composition of the armament and priority of flight qualities, which were maneuverability OR speed also fuelled the debate. On that matter, Lieutenant Commander (and Ace) Minoru Genda believed for a carrier-based fighter agility was key, over speed. For him, this way the fighter would be able to impose a battle on the enemy, winning a “turning contest”. He advocated achieving less power and if necessary, also heavy weaponry. Ace Lieutenant Commander Takeo Shibata led the opposing faction, stating that the A5M already demonstrated the Japanese already outperform other fighters.

Battles in China showed -and all pilots agreed on this- that the main problem, in order to engage opposition, was first to get there. Due to its short flight range, the A5M could just not escort bombers up to the objectives. So Shibata wanted both high straight speed and range to be paramount in the new design. Speed for hims was also a factor to impose its own battle tactics on slower opponents. Shibata also argued well-trained pilots with a faster aircraft would have a double edge in combat, even with marginally lower maneuverability.

This controversy between the two aces was not resolved at a meeting held on April 13, 1938. Circles close to the the Imperial Navy High Command started to voice their frustration over the pilot’s internal war and many started to advocate for a freeze of the 12-Ci program, rewrited them as well.

Jiro Horikoshi however intervened, and promised to ease all oppositions with his design. Based on early calculations, he was able to convince the Navy and the pilots alike that his new high-performance would have at the same time, the desired speed, range and maneuverability to please all pilots. Kaigun Koku Hombu (IJN aviation procurement bureau) officially approved the basic layout of the new model. But even construction of prototypes was greenlighted, Mitsubishi’s design team already had the design well refined in Oyomachi, Nagoya.

Impossible Challenges

Demands were so radical, though, it obliged to almost start from scratch. The company also took into consideration innovationd in several fields to achieve its goals, notably the use of a new top-secret aluminium alloy, developed by Sumitomo Metal Industries in 1936. This “extra super duralumin” (ESD) was indeed lighter, yet stronger, and more ductile than other alloys used at the time. The only problem -a serious one for using it at sea- was corrosive attack which made it brittle.

The problem was soon solved by consulting chemical companies and securing an equally innovative anti-corrosion coating, to be applied after fabrication. Among other measures, it was soon obvious that no armour protection was affordable given the limitations, for the pilot. Any special protection for critical points of the aircraft or the engine were ommitted as well as self-sealing fuel tanks. These measures, radical, helped reaching the specifications, but their cost was not apparent at first. It was paid dearly in 1943, five years later.

The Mitsubishi Type 0 given the year, was however lighter and more maneuverable than any fighter that came before, added to the longest range for any fighter plane (single-engine) at the time, in WW2. Tactically it was an enormous advantage for the Navy, that could escort their strike aircraft all the way to their objective, stay in defense, assist destroying opposition, and escort them back safely. No other country at the time has such fighter. The Zero was also capable of searching out possible targets hundreds of kilometres away, patrol much longer, etc. The tradeoff in weight and weak construction was known. It was discovered later it was quick to catch fire and exploding after a few rounds.

The reasoning was however, that speed and agility was the best defense. Given the cultivated aggressiveness of Japanese pilots, the new fighter was fitting them like a glove. The A6M in the end, secuced the navy as being the 2nd generation fighter it needed, by combining in addition of this agility, heavy armament and long range, a low-wing cantilever monoplane layout, a etractable, wide-set conventional landing gear, and an enclosed, well designed cockpit.

Outside advanced techniques with this extra-super duralumin, work was greatly facilitated by getting rid of pilot armour and self-sealing fuel tanks, thanks to the attack mentality of pilots of the time. Armament however as asked for was to be seriously upgraded. This ended by the choice of a pair of licence-built Oerlikon 20mm cannon (as the Type 99) located in the wings, which needed serious strenghtening at this place, exclusing also the fitting of satisfying arrangement of folding wings. The fuselage retained two Type 97 7.7mm machine guns in the hood.

Design Development

The young and very talented design team behind the Mitsubishi A6M1 Type Zero. A smiling Dr. Jiro Horikoshi is at the center. His assistant, Yoshitoshi Sone, is at the left. (Mitsubishi Kokuki K.K.)

Construction of the first prototype started circa in November 1938, completed in March 1939. This very first Type 0 weighed… 43,801b which was ludicrously light even compared to the gracious Spitfire prototype (53,32lb). So despite a modest output and helped by a sober consumption, the model maintained both long range and good performance and agility in all corners. That however meant future, heavier powerful engines could not be fitted without extensive redesign. So the offensive first, agility first doctrine eventually contained the seeds of its own downfall and never having a true successor.

Nakajima understood quickly these limitations and after trying to upgrade the Ki-43 by creating an interceptor derivative, the Ki-44, soon started again from a blank page with the Ki-84 whereas Mitsubishi condemned the Navy to stick with the A6M until the end of the war. The A7P (see later) indeed would never be ready in time. The Navy was nevertheless quite impressed with the prototype, which started unofficial tests at Mitsubishi’s Nagoya factory on 16th March 1939. Various systems were started and closed, flight commands, starter, ect.

Full engine tests started on the 18th, before being towed by ox-cart to Kagamigahara airfield for full air tests. Test pilot Katsuzo Shima had the privilege of “deflouring” the A6M, lifting off at 5.30 pm, 1st April 1939 for the maiden flight. Problems were detected with the braking system. Excessive vibration too in flight, which were common for new models. After extra bracing and solving minor issues, the Navy staff was invited for official tests of the model now called the “A6M1”, using an identical prototype.

On April 25, 1939 the first flight showed a limited top speed due to unsufficient output, compared to new fighters created in Germany, Great Britain or the USA now gearing up for 1000 hp+ gines. On May 1, Kaigun Koku Hombu instructed the powerplant team to install on the first prototype, now inactivated for further factory tests, the Nakajima Sakae 12 rated for 940 hp. While being refitted on October 18, the second prototype was tested with a three-blade propeller, seemingly superior and full armament set. These were factory tests though, performed whereas on October 25, the model was was accepted by the fleet. Weapons testing started later in October, with excellent results as for acuracy, nine hits sercured out of 20 shells, in flight on a 19 m2 ground target​​.

The third prototype was in fact the very first pre-series A6M2 fitted with the Sakae 12 engine. To install it, the engine mount and hood were reworked to accomodate the larger Sakae and for minimizing and keep forward visibility, designers made the hood a very tight fit, a veritable glove around the engine. The first consequence was unsufficien engine cooling, an issue the designers took considerable effort to solve. The team also worked to eliminate a noted tendency by test pilots to a flat spin and so the tail was redesigned, with its cord moved back, the horizontal tail shifted up resulting in this elongated “tail” and almost triangular shape, and increased length. The original configuration can be seen on the production A6M2-N “Rufe”.

This third prototype was vital to secure mass production, at Nagoya aircraft factory No.3. The Navy the lack of outright speed at 304 mph instead of 315 mph as asked for, had all the remaining requirements met and teething issues worked on actively, so it was officially accepted on the 14th September 1939. And it was time: War raged in Europe since the 1st. This order came even before the completion of the full test cycle, and it gained its Full military designation, to be communicated to all branches of the administration, as “A6M1 Type 0 Carrier-borne Fighter”.

Name and designation

ONI comparison between the Zeke and Hamp
ONI comparison between the “Zeke” and “Hamp”, believed to be a completely new aircraft.

And this brought us to the famous name of the model. Unlike later WW2 models which for propaganda reasons received nicknames instead of the cold navy designation (the army did the same), the usual practice for pilots and personal was to call it the “Rei-sen” an abbreviation of the full designation. It was by no means official or had any meaning. Also, A6M referred to A for the type (fighter), 6 as the sixth fighter model designed by Mitsubishi, and of course “M” standing for Mitsubishi.

The ‘0’ however, derived from the last digit by virtue of the unique Japanese calendar in reality came from the year 2600 (1940) and the “Rei Shiki Sento Ki” shortened to Rei-Sen or Reisen could mean “zero” by simplification. It became popular, but was not official in US Intel either. In 1941, the Allies applying code-names to all models had the A6M2 designator chosen being ‘Zeke’ last letter in the alphabet in reference to the “model 0”, “Zek” being a contraction from the biblical name “Ezekiel” although “zero” while not official became far more popular.

The cut-wings version A6M3-72 was designated ‘Hamp’ and the A6M3-22 ‘Zeke Mark 2’, the A6M2-N ‘Rufe’ (see later). ‘Zero’ in western sources mostly became first popular by US use, as British personnel in Singapore/Malaya called them first as ‘Navy Noughts’. The model became so feared (a bit like the Tiger tank of the Wehrmacht), that the handy nickname of “Zero” became a reference for all Japanese fighters in the general public and the press, obscuring many other models, including those of the army. It has been maintained the same way over many years in popular culture, as basically the only known model by the general public. Even among pilots, especially in 1942, “Zeros” were seen everywhere despite they encountered the “Oscar” or its successors. Despite it’s many design changes, the A6M5 also kept the famous name.

Initial Reception

ONI, the “Hamp”, A6M2

ONI, the “Zeke”, A6M3

ONI depictions of the “Zeke 52” (A6M5)

The pre-production batch was received for military testing at Yokosuka kokutai, stationed at the Oppama airfield. This instructor/test unit was the most famous in Japan, staffed by the most experienced pilots of the IJN. They were all fully able to appreciate the model, and in their initial reports, spoke highly of its flight characteristics, rivalling in superlatives terms. The A6M1 was trouble-free in addition, which added to the immense trust they had for it, apart a serious incident on March 11, 1940 when test pilot Okuyama flying the second prototype tested overloading the engine with revolutions in a steep dive.

The second approach from 1,500 m to 900 m at 50° angle generated such vibrations and noise the suddenly exploded, leading the prototype to burst into pieces, with the pilot thrown out of the cockpit at 300 m. His parachute opened, but the schock was such the pilot was pulled out of the belts and fell into the water at great speed, killed instantly. Exact cause could not be determined although some expressed that perhaps the aileron balancers broke resulting in the initial vibration that destroyed the aircraft. This, the initial order delivery schedule was pushed from May to July 1940, leaving time to strengthen the attachment points of these balancers, as well as the rudders.

Final tuning as production took place added pressure from the high command and military personal, as its amazing flight qualities spread like live fire from Oppama among aviators. Some went off working hours to see and test it of possible, while Mitsubishi was trying to manage the best flight range as requested probably the most stringent and demanding specification. Extra rosy reviews came also from Yokosuka kokutai test pilots despite Mitsubishi’s insitence that their “product” was still unfinished.

On July 21, 1940, Kaigun Koku Hombu announced the reception of the first batch of six pre-production fighters, which flew to Hankou in China, staffed with pilots from Yokosuka Kokutai led by Tamotsu Yokoyama. The small contingent was integrated into the 12th Rengo Kokutai. Back in Japan, the next batch of pre-production aircraft were sent straight to IJN Kaga for carrier qualification. After successful completion, the A6M2 model 11 was accepted into service, gaining the “Reisen” moniker. These nine carried fighters also departed for Hankow, reinforcing the 12th Rengo Kokutai (which had a first loss due to AA at the time).

Problem with engine cooling were solved by using tin deflectors installed on the cylinders of the first row meanwhile. Their effect was to directing air jets to the cylinders of the second row. This became the standard for all variants, whatever the engine, but another issue was revealed in front-line conditions which was the frequent jamming of the ventral fuel tank discharge system. This unwanted “ballast” created drag under the fuselage, reuniting the aerodynamics qualities of the aircraft to some extent.

Design evolution


Mitsubishi being asked, despite the acceptance and first order, to solve the lack of speed, concentrated on the next iteration in 1940, the A6M2. Same model but with a the more powerful 940hp Nakajima Sakae 12 engine. The A6M2 was mostly modified with extra bracing for the larger, heavier engine, and the first 15 pre-production models were sent to Hankow, China for operational trials, starting on 21 July 1940. First combat missions started, showing a clear cut superiority over any model of Chinese fighters. Only two Zeros were lost in these early operations and it was by AA fire, traded for many, many kills, fighters and bombers alike. They ruled the skies over China, at least in dedicated coastal areas. More inland, the Ki-43 made it’s combat debut also, leading to interesting comparisons.

Mitsubishi built 47 more A6M2 Model 11 by November 1940 and started working on the Model 21, to answer a regular critique. The wing structure intil that point did not supported the complicated gear for wings folding. A first measure found was folding wingtips. The passage from “11” to “21” denoted this airframe change, the other digit, the engine change. The A6M2 Model 21 thus became standard at the time of Pearl Harbour, 18 mo,nths after its combat debut. There were 328 of these in JNAF units, the bulk of some 521 naval fighters aboard carriers of the Kido Butai (1st fleet air arm). The A5M was now relegated to light carriers, land-based units and theaters, notably in China.

1941 saw an effort by the design team to try overcoming the A6M initial design limitations, to keep its superiority over Allied fighters. This led to the design of the first real all-out improvement, the A6M3 Model 32 which was redesigned around the 1,130 hp Sakae 21 engine. For simplification the folding wingtip section was removed for a simplified clipped wing. The centre of gravity was also moved back towards the bulkhead and this reduced in turn the fuel tank volume.

Later came the Model 22 which saw the return to the folding-tip wing and fitting an extra 12 gallon fuel tank in each wing to reclaimed the lost range (it was still superior to any allied fighter). Meanwhile, engineers worked on an even greater improvements, the Model 52. The Model 22 had a fairly short operational life and production with just 560 delivered between 1942 and 1943, including those by Nakajima.

For most naval air historians the A6M5 Model 52 was really the “game changer”, less compared to the Model 32 it replaced, but compared to the A6M1 as a whole. Helped by some weight saving in the wing, heavier gauge wing skins were possible to make for higher dive speed (a point which was lacking previously, the F4F could escaped that way, being way more rigid), and the engine had a new cowling caracterized by individual exhaust stacks for additional thrust. This became in 1943 the standard, most numerous and used version overall.

The Model 52 became outdated however by 1944 as already by mid-1943 it did not fared well compared to the beast that was the F6F, so further modifications were pressed on, all severely hampered by the limitations of the initial design. Meanwhile, Mitsubishin came with the A7M Reppu and J2M Raiden, the latter entering service unlike the first in small quantitied, and Kawanishi with the excellent and N1K Shiden, but these complicated design failed to obtain masse production and Mitsubishin’s factories were stuck with a 1940 model that cannot be upgraded any longer.

To try improve altitude combat capabilities and enabling some interception capabilities at a time the Empire was on the defenseive, Jiro’s team managed to pull out the ramarkable A6M4, first with a turbo-supercharged engine and the A6M6 using water-methanol injection. The Navy also wanted a more serious fighter bomber from it’s standard model leading to the development of the A6M7 and eventually to the A6M8 fitted to endure the massive 1,350 hp Kinsei engine, almost twice the power of the original Suisei 13 and its 875 hp. Their development was complicated by shortages of all sorts plus bombings, and in small quantities.

Design Features

-The Zero also revolutionized the way naval fighter could operate, by bringing an amazing radius of action, twice the previous figures in the IJN: 1,180 miles. Ex. The FAA Sea Hurricane was limited for example to 600 miles, the sea spitfire just 550, and the F4F 845 miles.

-The zero blended the limit between carrier-borne fighters and land based equivalents. When the zero was in service, the F4F was 4 months late in its introduction. For the first time a naval fighter, usually inferior to its land counterparts, could dominate the skies and dogfight with any model in the air at that time. This gave the fighter a “long arm”, ability to escort the attack planes to target, engaged the CAP in a long dogfight further straining gazoline, and came back escorting all the way. It could strile by keeping the carriers out of arm’s way. This range completely deceived US commander in 1942. ONI figures were totally underestimated at around 800 miles and surprise total in operations. Having a 500 miles radius of action around a carrier was unheard of, and decisive. Their appearance seemibly in many places at once made the US think the Japanese had far more zeros than in reality.

-Thus, it was clear the US intel needed to have their hands on a zero at all costs. It became as much top priority as for the British cracking for example the Enigma code. However in almost all cases, down Zeros were so light they disintegrated, leaving practicall nothing to study but scattered small remains on miles on end. The first occasion it nearly happened was over Parl Harbor in Dec. 1941, as two of these were shot down, but the first landed on its belly, but slided and crashed into N.4 hangar at Kamehameha. At least the rear section survived well enough to be studied. Another crash-landed on its way back to the Kido Butai, also making a controlled belly-landing on Nihao Island. The pilot, Shigenori Nishikaichi was captured by local Hawaiians, but managed to escape, returned to his planes and burned it entirely, before being caught and killed. The first would be captured in Alaska. This was a crucial blow as the Japanese lost their secrecy and pilots were duly briefed on the strenghts and weaknesses of the nible champion.

-August 1940: Start of service. Sept. 13 first victory over China 30 Chinese fighters I-15/I-16. 30 min. dogfight over chongking. Saburo Sindu claimed 20+ Chinese down without any loss, but four zeros damaged.

-The “zero” had a indirect major shortcoming: Its production. Interservice rivalry first objected to adopt the A6M despite it’s qualities, and even for the Navy itself, Japan lacked the engineers, the economic muscle, and the industrial culture needed to rapidlt ramp up to wartime production the way the US did. By late 1943 still, the Zero, was still hand made by skilled laborers. The models were only made in Nagoya and parts conveyed by mostly primitive means: Oxen were carrying these between facilities ! Due to the absence of airfield or railway nearby, not good roads and the fear to damage tghe delicate fighter on trucks, so they were carried the old way for 34 miles being final assembly.

General structure

(To come if i can find infos)


A6M5 Sakae engine without cover. A distant licenced mix of Hawker Siddeley, Bristol Jupiter and Wright Cyclone designs studied and improved over the years.

The A6M1 engine was not the one initially planned for production, but a quick in-house production model to speed up testing. It was the Mitsubishi MK2C Zuisen 13: A 2-row, 14 cyl. radial air-cooled, supercharged engine with a cubic capacity of 28.017 liter (1,709.7 cubic inch displacement) and rated for 780 horsepower. It was half the final evolution of the Type 0 A6M7.

The first standard engine of the production A6M2 Model 12 was the air-cooled, supercharged, 27.874 liter (1,700.962 cubic inch) Nakajima Hikoki K.K. NK1C Sakae 12. This was a two-row, fourteen-cylinder radial rated at 925 horsepower coupled with a three-bladed Sumitomo constant-speed propeller through a 1.71:1 gear reduction. The Navy found it lacked power and wanted to swap to the next model in development.

Various hood and cowling designs between types

This gave the A6M2 Model 22, powered by the Nakajima NK1F Sakae 21 (hence the model name) 14-cylinder radial rated for 1130 hp and equipped with a two-speed supercharger. A single A6M3 was tested with a Sakae 12 to but posed weight distribution and center of gravity issues. Differences between the Sakae 12 and 21 were the bulbous reduction gear housing around the front of the crankshaft (absent from the Sakae 12). The Sakae 21 had the Naval designation NK1F, first letter standing for the manufacturer, Nakajima, K for “air cooled”, 1 for the sequence number within given class of engines and F for the version of the engine. The Sakae 12 was also called NK1C.

Specs were as follows: Cruise speed 207 mph (333 kilometers per hour), max 277 mph (446 kilometers per hour, Sea Level) or 335 mph (539 kilometers per hour) at 16,000 feet (4,877 meters) with a ceiling at 37,000 feet (11,278 meters), maximum range to 1,175 miles (1,891 kilometers). This was less than the A6M1 and go go downards until measures were taken to reclaim the lost fuel.

Cowling of the experimental A6M8

The standard A6M3 was given the Sakae 21, with a new 2-stage mechanical supercharger, improved gearbox, upflow carburetor rated at 1130 hp on the Model 21. This was the “chopped-wings, low range” Zero of the whole serie. The A6M3 M22 regained some range. The A6M4 was a rare, mostly experimental variation with a turbocharger which never worked properly mostly due to materials issues. The A6M5 kept the same engine with minor improvements, and the A6M6 tested the Sakae 31a engine with water-methanol injection, never passing out the prototype phase, but pushing the figure to 1,210 hp (902 kW).

The A6M7 had the 1,130 hp Sakae-31 engine. By 1944 when it was tested, this was 1,000+ hp shy of most allied fighters. This engine remained the most powerful on offer before Mitsubish came out, two years late, with the Kinsei 62 engine, capable of 1,163 kW (1,560 hp). It was adopted by the prototypes A6M8 but never saw action. Thus, the Zero made all its WW2 career with 1,000 hp like some Italian fighters. It was not a problem as long as the superstructure remained light, but demands for protection and better armament rose weight considerably and performances stayed on the same range all along, with decreasing range to boot.


The Production A6M1 was given a couple of Dai Nihon Heiki K.K. Two Type 97 7.7 mm (.303-caliber) light machine guns were mounted in the hood, firing in slight channels, and synchronized with the propeller arc. These were licenced Vickers Type E .303 machine gun, so they were liquid-cooled. 600 rounds in sore for either, with tracers. This was coupled with two Type 99 20 mm autocannons mounted in the wing, but with just 60 shells per gun. Both were licensed Oerlikon FF guns. No rack was installed to carry bombs unlike what was planned (aktghough fittings were there), but a belly extra fuel tank as the range was already insane for the time.

Specifications for the 1937 12-Shi fighter called two 20mm cannon, two 7.7mm LMG, racks for two 60kg bombs, and with A6M3 Model 32 no modifications were made but in the channels which the LMGs fired through as the engine hood grew in size. Ammunition supply for wings cannon was a main criticism, and it was increased from 60 to 100 rounds per gun. Same for the Model 22. The Model 22KO or A6M3 Model 22a had longer-barrel cannons. Some Model 22s experimentally tested a 30mm cannons, in combat at Rabaul. But vibrations were just to much for the wings.

The 7.7mm machine guns had a capacity raised to 680 rounds each and close to the Army Type 89 MG with belt ammunition for a 1000rpm rate of fire and effective range of 600m. They had a muzzle velocity of 2460ft/sec and weight 26lb each. Replacement on the field and service was easy. Not so much for the 20 mm wing guns.

Divergence path between the 7.7 and 20 mm.

The wing Type 99 cannons of the Model 22 used drum-magazine types (100 rounds) belt-fed later to reach 150 rounds. The Model 22a or Model 2 Shiki 3 with a longer barrel reached 490rpm at 2,000ft/second, and useful range of l000m. The 30mm Type 5 tested by just three A6M3 Model 22 were limited to a 45-round magazine, with a muzzle velocity of 2460ft/sec, but as said before was not adopted.

The pilot could aim via a Type 98 reflector gunsight mounted in front of his position, the tube going through the front glass, but for post-action briefings an optional Type 89 camera-gun could be fitted to the port wing root. The Type 89 Motion Picture Gun 2nd remodeled No/3899 from Roku Sakura.

Armament was augmented on the A6M5a, with belt-fed Type 99-2 (long barrel) 4-shiki, to 125 rounds per gun. The next A6M5b replaced the right LMG by a single 13.2 mm Type 3 gun with a 790 m/s (2,600 ft/s) muzzle velocity and, 900 m (3,000 ft) range, 800 rpm, 240 rounds in store. That was an appreciable increase of firepower, but asymetric. The A6M5c was even more powerful and engineers managed to shoe in two extra 13.2 mm (.51 in) Type 3 machine guns (same model as on the hood) in the wings, outer portion from the cannons. Although ammo was limited they had on paper more firepower than their adversaries given the fact 20 mm superior to 0.5 in HMGs. However the left hood 7.7 mm gun was deleted, making room for extra ammunition for the right Type 3 HMG. In addition the underwing was reinforced to accept four racks carrying each a small 60 kgs incendiary bomb or rockets. The “special type” bakusen was a modified fighter bomber substituting to the drop tank rack, a bomb rack to lift a 250 kg (550 lb) bomb.

Eventually the little-known A6M8 fitted with the most powerful engine of the serie, had a brand new cowling now with a pair of 13.2mm Type 3 HMGs and those in the wings replaced by two more of 20 mm for four total, each with a 125 rounds belt. Unfortunately, Only two prototypes were built, this model never saw combat. This was a sharp contrast to its Army rival Nakajima Ki-43 Hayabusa which at its beginning only carried two 7.7 mm LMGs.

Cockpit, Equipments & Avionics

On the A6M2

The Zero cockpit was clear and simple to read, with the lightest materials possible, and common dials for several metrics to save space and weight. It also made for a less complicated electric wiring, less chances of a shortcut and fire. The two most important dials for the pitch and yaw and speed indicator were placed right between the central console, either side of the 7.7 mm machine guns, which took some internal space but could be serviced by the pilot. The rest of instruments, 13 different dials mostly related to the engine’s rpm and oil, avgas indicators among others, was located below. Extra gauges and dials were located on the right side, along with control levers. See also a 360° view.

On the A6M5

Normal provision was a full radio fit with a direction finding equipment. The radio direction indicator was located at the lower left of the instrument panel with a console on the right side of the cockpit, close to the inertia panel of Zerostarting handle. The proper radio control unit was located on a console rear of it. The loop antenna was installed behind the pilot’s head, under the glass cover, and can be manipulated through a control handle a the rear of the radio control unit. The wooden mast (because lighter) rear of the cockpit supported the radio aerial connected to the fin top. To serve the radio a transformer and battery were located inside the fuselage, behind the pilot’s seat. The Model 11 standard model was the Type 96-Ku-1 radio, complemented by the Type 1 Ku-3 direction finder. The Model 22 was likely equipped the same way.

Final assessment

IJN Ace Nishizawa’s A6M5 UT105, 7 May 1945. The worn out dark olive green paint factory applied is well visible here.

When it was introduced in early 1940, the “Zero” was one of the most modern carrier-based aircraft in the world. Its oppositon in the Royal Navy was the heavy Fairey Fulmar and in the US Navy the Brewster F2A Buffalo, to the point of being superseded by the Grumman F4F Wildcat. Until the introduction of the F6F Hellcat from mid-1943, the Zero was almost “untouchable”.

Its main advantages as a dogfighter were a fairly high-lift, low-speed wing and very low wing loading. It also had a very low stalling speed (below 60 knots or 110 km/h, 69 mph). Its “phenomenal” maneuverability as recoignised by its foes over China and Chennault’s “Flying Tigers” already in 1940 (equipped with the Curtiss P40 Warhawk) allowed the A6M to out-turn any Allied fighter of the time. Eearly models were fitted with servo tabs on the ailerons, after pilots complained about too heavy commands at above 300 kp/190 mph. That was the price for lightness as, these features were planned bu not included. However, servo tabs were retired, as with this lightened control forces pilots had much confidence to overstress their airframe, making quite vigorous maneuvers while not always grasping how flimsy was their fighter to endure G-Forces.

In fact, first information seeping through about the new Japanese “superfighter” arrived peacemeal in Europe and America, both in vague and contradictory terms. The existence was noted in reports by many observers, notably Colonel Claire E. Chennault, working still as an adviser to Chiang Kai-Shek, before meeting them in person with the “Flying Tigers”. These messages were not given the same importance given the isolationist policy of the US at that time. This majority simply wanted to prevent an increase in military spending, and spread the opinion that this new mystery fight was just a “pale copy” of European models. There were some ground for it, with only proofs such as licensed/copies of the Hamilton-Standard propeller, Bendix chassis, Palmer tires, “Sperry”, “Pioneer” and “Collsman avionics, “Oerlikon” cannons and “Vickers” derived light machine guns. At the same time, the press was far more enthusiastic about the new Lightning, Corsair, and Mustang in development, they assumed would be infintely superior.

A6M2 drawing

However the rampaged of the Zero in air battles in China also convinced the Japanese military that Japanese aviation overall could gain incontested air supremacy, not only over China, but over Asia at large. The common belief at the time was that a single Reisen even in the hands of an experience pilot, could down from two to five enemy aircraft in a first encounter. Such calculations were recalled during heated discussions when considering war against the USn despite contradictory opinion (generally from the Navy and Yamamoto in particular) about the economic superiority of the United States.

The hope of a short war, just like in Germany in 1939 was that six months would be sufficient for Japan to expand rapidly in all the pacific and create a “glacis” containing enough resource for a possible war or attrition although most believed (hoped) that the “decadent west” and rampant pacifism would prevail. Qualitative advantage was seeked for already in all branches of the military, navy included (examples were many, like the “long lance torpedo”, the Yamato super-battleships, giant aircraft-carrying submarines, superior destroyers and cruisers, etc.).

The “superfighter” fully met this picture. But its high qualities, praised at the start and proven time and again until late 1942, brought the IJNAF it’s own demise, as specialists of Kaigun Koku Hombu missed the moment when work on its successor, from a black page, was to start. It should had started right in 1941, but at the time the military simply did not believe their wonder machine would become obsolete within the “six month” campaign credo. A fatal mistake as the Zero soldiered on until 1945 with significant but not game changing improvements.

Production & Variants

Technical tree of all versions

In the end, Mitsubishi, which facilities were tailored initially for peacetime and had a rather low output and limilited possibilities only produced 3,879 out of more than 10,000. This is, ironically its competitor, Nakajima, who assembled the remaining 6,215. The remainder were 844 spread between trainers and floatplanes, also built by Nakajima, which had larger and better facilities.

A6M1 (1939)

Initial prototypes, two which carried this A6M1 designation. The A6M1 was really the ideal “pure” zero as it was first thought of. It’s super light structure made the best of the 700+ hp of its tiny original engine, manoeuvrability was superb with a turning circle barely larger than that of the A5M, and extraordinary range for any fighter. The two prototype A6M1s were powered by the air-cooled, supercharged, 28.017 liter (1,709.7 cubic inch displacement) Mitsubishi MK2C Zuisen 13, 2-row, 14 cylinder radial rated for 780 horsepower (takeoff). It was coupled with a two-bladed variable pitch propeller, later three-bladed Sumitomo constant-speed propeller after early trials (license-built Hamilton Standard). The second prototype was called c/n 202 and contributed to the September 1939 acceptance trials by the Navy. Next would be production (pre-prod batches initially) A6M2s. Name Rei Shiki Sento Ki, or “Rei-Sen,” was chosen.

A6M2 M11 and M21 (1940)

Tech cutaway of the A6M2

A total of only sixty-four A6M2 model 11 with serial numbers from 3-67 were built. The first wave of modifications saw the strengthening the rear spar of the wing from the 22nd model. From 37th location of the exhaust pipes was moved away to the fourth flap regulating engine cooling and fifth. The port’s cross section for the wings guns was reduced, the cabin air inflow holes for ventilation were relocated at the leading edge of the right wing console. The 47th introduced a modified glazing of the cockpit rear canopy.

Tests on board Kaga the fit in a standard lift to be very tight, with a gap too small to safely move it from the hangar to the flight deck and back. Personnel successfully coped with this problem nevertheless, fing ways for a perfect firt on the lift each time, but doubts came about the same in the heat of battle. So Mitsubishi introduced wingtips manually fold. Minor improvements consisted in changing the cross section of the cannon ports, cabin ventilation air intake, leading to the A6M2 model 21.

From the 127th the Model 21 received a new aileron balancer adjustable on the ground after the April 17, 1941 crashed that killed Lieutenant Shimokawa due to vibrations (see abiove). From November 1940, it was also built by Nakajima (Koizuma plant) in two years, for a total of 740 A6M2 model 21 at Mitsubishi and 800 for Nakajima, which developed from it the A6M2N “Rufe”.

The “zero floatplane”: A6M2-N “Rufe”

A6M2-N Rufe

The A6M2-N floatplane was developed as requested by the Navy to support amphibious operations (operated by one of the many IJN seaplane tenders), or defend remote bases. Based on the A6M-2 Model 11 technically, it had a modified tail to keep stability with a much higher drag, cauised by the added floats: One large under the fuselage to keep balace and two small underwing. 327 total were built, and it was deployed in 1942 as the “Suisen 2” (“Hydro fighter type 2”). Its first actions were mostly defensive, in the Aleutians and Solomon Islands. They were found surprisingly good at harassing PT boats at night, causing the latter to increase AA and adopt projectors. They were also found useful to drop flares on them, allowing destroyers to fire on them.

A6M2-N also were used to protect fueling depots in Balikpapan and Avon Bases in the Dutch East Indies, sparing land fighters or the Shumushu base in the North Kuriles, relatively “quiet” sectors. They were operated notably in several operations from IJN Kamikawa Maru in the Solomons and Kuriles and the Hokoku Maru and Aikoku Maru during the Indian Ocean raids. The Aeutians saw the first kills, RCAF Curtiss P-40 Warhawk, Lockheed P-38 Lightning and B-17 Flying Fortress. They were found versatile enough to be used for patrols, as fighter-bomber and short reconnaissance support during amphibious landings, spotting targets of opportunity for escorting vessel’s artillery.

The “Otsu Air Group” used them alongside the Kawanishi N1K1 Kyofu (“Rex”) from the Biwa lake, Honshū area. The French forces in Indochina managed to captured and test one of these, until crashed after being overhauled.

A6M3, the chopped off wings version

A6M3 model 32 cutaway
A6M3 model 32 cutaway

A6M3 M21

By mid-1941 the company agreed with pilots that the recently introduced A6M1 needed modernization. It turned out the pilots wanted to strengthen firepower but it was not done due to structure issues, and improving maneuverability was not considered, however speed qualities were. The adoption of the Sakae 21, with its two-stage mechanical supercharger and improved gearbox plus upflow carburetor for a, output of 1130 hp, improved high-altitude characteristics, but the increased weight diminshed somewhat agility.

To compensate the fuselage’s fuel tank was reduced from 98 to 60 liters, whcih reduced the range accordingly. An advantage early in the war, it was not that important. The hood was also modified, to accomodate a new supercharger air intake above the engine, raised with now machine gun’s characteristic channels. An automatic, larger propeller of 3.05 m was also installed from 4th production model, and ammunition load (by default of armament) went from 60 to 100 shells per barrel for the main wings 20 mm guns. It was in larger drums, protruding beyond the wing, so now covered by a fairing. Ailerons were also modified, without the initial and fragile complex two-stage control system.

A6M3 M32

The A6M3 entered service in June 1941, so even before Pearl Habour, and had their first tests in China. Reports shows performances were increased to a lesser extent than expected. Many pilots also wanted to abandon the wing folding mechanism. Designers when decided to have the wingtips cut off along the folding line for it to still fit. Speed also increased a bit, and the wings surface lost, about a square meter deteriorated maneuverability to the price of increase climb rate at 6000 m in 7 min 19 s (7 min 27 previously). The A6M3 model 32 as a new model however experienced teething problems with the Sakae 21 engine, and production of just 32 was only reached by July 1942, with 343 total. This was pinprick compared to the next, main production version which was the one mostly encountered by pilots.

The “chopped off” wings version was assumed by the allies to be a new model and received the codename “Hap” (nickname of the USAAF General Henry Arnold), which ordered it was changed to “Hump” and eventually discarded in December 1942, and eventually with better intel, was called “Zek 32”.

A6M3 M22

When the Zero Model 32 arrived in frontline units a fierce battle developed over the Solomon Islands, compounded later by the crippling losses at the Battle of Midway and lack of airfield network in the combat area. This the admiralty returned to the demand of reclaiming range of the Zero, tat least close to the one of the A6M1. For this purpose, the A6M3 model 22 appeared with two additional fuel tanks holding each 45 liters located in the wing, near the weapon bays. Not to impair maneuverability wings were back to their elongated folding wingtips. In all, 560 model 22 were produced, including some Model 22a, improved with their type 99 model 2 guns with elongated barrel. Three aircraft also tested a new 30-mm guns, but the wings were just too “delicate” to withstand their recoil. Both variants of the A6M3 m32/m22 were built by Nakajima, to increase radically production numbers.

A6M4: The high altitude interceptor

The A6M4 model 32 was a new version using a turbocharger was used. Only two prototypes were built tested at the 1st technical arsenal of the fleet. Mitsubishi in fact forgotten all details about the designation “A6M4” and exact production records and Jiro Horikoshi himelf did not recalled the details. The model was developed in secrecy in a separate workshop around a small team. “A6M4” appeared on a captured Japanese memo at the Air Technical Arsenal dated 1 October 1942, only mentioning a “cross-section of the A6M4 intercooler”. Design and testing of this turbo-supercharger performed by First Naval Air Technical Arsenal at Yokosuka generated a report and at least one photo of a prototype exists, showing a turbo unit mounted in the forward left fuselage.

The main problem was then to get suitable alloys for the manufacture of the turbo-supercharger and its ducting. Bad quality materials caused ruptures, fires and degrading performance which cancelled further developments. The navy never accepted it, so the potential numbers Model 41/42 were never formalized, whereas the arsenal still used the designation “A6M4”. This experience was not lost as it povided technocal backrgound for further tests and engine designs. If production was never launch, Japan would never have its interceptor variant, the Zero staying a low-alt dogfighter to the end. But the J2M became that “bomber killer” ask for later, and work done on the A6M4 contributed to it.


This was by far, the best known, best produced and numerically largest variant of all. But it was also the challenger of the new F6F Hellcat, among others. Its genesis went back to late 1942, when pilots reported on possible improvements on the A6M3. What became the Model 52 started over the same issues of getting rid of the mediocre wingtip folding system but shortening the wings while increasing speed. The aileron trim tab and flaps were revised first, and Nakajima, due to the poor daily rate of Mitsubishi, took on the bulk of the production. So the model could have been seen as the “Nakajima A6M5”. The prototype was created in June 1943 based on a production A6M3, making its maiden flight on August 1943. Performances were average, but better than initial models, thanks to hood and exhaust modifications, topping at 565 km/h (351 mph)) at 6,000 m (20,000 ft) with a climb rate of 7:01 minutes.

It seems that early production models were still fitted with the same exhaust system and cowl flaps as on the Model 22, but the upper cowling was redesigned towards the Model 22, while a new exhaust system was worked on, providing better thrust by spreading stacks aft with better distribution. The new exhaust system was completed by “notched” cowl flaps, and heat shields aft, not to damage the fuselage. From the 4274th model, another incremental improvement came with wing fuel tanks adopting for safety, carbon dioxide fire extinguishers. Still not self-sealing, that was at least one protection measure, sorely lacking. From #4354, a new radio, the Model 3 with its aerial Mark 1 with a shortened antenna mast were standardized. From #4550, the lowest exhaust stacks were made even compared to those above, but the first pilot flying it, reported these burned the forward edge of the landing gear doors and compromised the tires so from the next plane, #4551 Mitsubishi install even shorter lower exhaust stacks. Nakajima manufactured the Model 52 at Koizumi (Gunma Prefecture). The

A6M5a, Model 52

The M52 Ko, appeared from #4651 at Mitsbushi.
-Its armament was modified, getting rid of the Type 2 drums for the belt-fed Type 99-2 4-shiki, with 125 rounds per gun (25 more) and the underwing could be better streamlined, with the elimination of the bulge. The ejection port for spent cartridge cases was moved also away.

-Another modification which was well awaited, was about extra rigidity, with a thicker wing skinning installed, for greater diving speeds.

A6M5b, Model 52

The 52 Otsu was mostly concened by an armament change over the hood:
The old 7.7 mm (.303 in) Type 97 gun (750 m/s (2,500 ft/s) the right forward was replaced by a single 13.2 mm Type 3 gun capable of 790 m/s (2,600 ft/s) for muzzle velocity and a 900 m (3,000 ft) range, 800 rpm and storage for 240 rounds. It needed also an enlarged opening and channel, creating an asymmetric appearance on the cowling.

-The other main modificaton was a revised gas outlet near the windscreen.
-Each wing cannon received a fairing on the leading edge.
-An armored glass 45 mm (1.8 in) thick was fitted to the windscreen as protection.
-A larger propeller spinner was fitted.
-The ventral drop tank was changed, having fins and suspended instead on a slanted pipe.

The first of A6M5b or “M52 Ko” was tested and ready by April 1944, production ending in October 1944.

A6M5c (Model 52 Hei)

The final production variant of WW2.

-An extra 13.2 mm (.51 in) Type 3 machine gun was added in each wing, outboard of the cannon, with the right reinforcements. The left hood 7.7 mm gun was deleted and not replaced. But this version overamm had three 13 mm and two 20 mm guns, ending as the best armed Zero in service.
-In addition, it was modified to carry four racks underwings, to be used to carry rockets or small bombs, located outboard of the 13 mm wings guns.
-Major change, the engine, a Sakae 31 engine, for increased performances
-For protection, an extra 55 mm (2.2 in) thick piece of armored glass was installed at the headrest.
-Also a 8 mm (0.31 in) thick plate was installed behind the seat. At last the pilot got the protection it deserved.
-The central 300 l (79 US gal) drop tank was changed to a four-post design.
-Wing skin was thickened for better dive performances, with detailed structural improvements.

The first A6M5 made its maiden flight in September 1944, but it was not a good dogfighter and was used at the time mostly as an intercepting to reach B-29s and for “special attacks” (Kamikaze raids).

The ultimate sub-version was a “pure” interceptor, the A6M5-S (A6M5 Yakan Sentōki) and dedicated night fighter. The armament was changed as a single 20 mm Type 99 cannon was installed behind the pilot aiming upward, and inspired by the Luftwaffe’s Schräge Musik installation which prototype and plans were carried by submarines. There was no radar and thus this variant was basically “blind” and only vectored from the ground to a probable location.

There were also experiments of a bakusen, a fighter bomber, with Model 21 and 52 converted with a bomb rack holding a 250 kg (550 lb) bomb, replacing the drop tank. Numbers so converted are unknown.

Also, the Model 52 was converted into the specialized A6M5-K two-seat trainer at the end of the war, in short numbers as advanced trainer by Hitachi, but mass production never started.


The A6M6 Type 0 Model 53 was developed to take advantage of the Sakae 31a engine with a newly designed water-methanol engine boost, plus self-sealing wing tanks, something that was expected; Preliminary testings however were disappointing, with not notable increase of power and unreliability of the fuel injection system. Testings went on until it was dedided to cancel this version, amidst priorities. Only a single prototype was produced. This version shows how much the IJN was desperate to see a power increase on its warbird, by all means possible. But the basic structure was simply not to accept larger engines. There was no way around a complete redesign.


This brings us to the natural successor of the Zero, the A7M Reppu, developed better below. However engineers at Mitsubishi were not done yet. The A6M7 Type 0 Model 62/63 was at least a rare variant to see service, the very last. It was designed to meet a new Navy requirement for a dedicated attack/dive bomber version operable from smaller aircraft carriers and/or replace the Aichi D3A2 on a lighter package than the Suisei. The A6M7 was completely modified for for dive bombing, with a reinforced vertical stabilizer, special bomb rack underbelly and racks underwings for two 350 litre drop tanks plus bomb swing stopper underside the wings. It received naturally the last engine, the Sakae-31 capable of 1,130hp at take-off. Gun/MG armament was also the same as the A6M5c. The model was capable of carrying a single 500kg bomb. Production started by May 1945 but the need for it radically declined and it was used more in the “special attack” (kamikaz) role, in particular over Okinawa.


Basically the same attempt of power improvement as the A6M6 but with a Mitsubishi Kinsei 62 engine capable of 1,163 kW (1,560 hp), making a 60% power increase compared to the A6M2. The cowling and nose were completely redesigned. The carburetor intake was massively enlarged as on the B6N Tenzan with a long duct, exhausts modified, and large spinner similar to the Yokosuka D4Y which shared the same engine. The larger cowling also had the advantage of allowing larger nose MGs, both 13.2mm Type 3 models. Eventually, four 20mm Type99 shiki-2 cannons were fitted in the wings, two paired, with the same ammunition figures of 125 rounds, belt-fed.

To regain range also, this ultimate Zero carried two 150 l (40 US gal) drop tanks underwings. Under the fuselage two new racks were installed, designed to be capable of holding 250 kg (550 lb) bombs. However the most ever powerful zeros never saw service: Only two prototypes were completed in April 1945. Despite an IJN order for 6,300, production never materialized and US troops captured the two prototypes having completed all their tests flights.

Detailed specs

Specs A6M5 (1943)

Crew: 1: Pilot
Fuselage Lenght 9.06 m (29 ft 9 in)
Wingspan 12 m (39 ft 4 in)11 m (36 ft 1 in)
Wing area 22.44 m2 (241.5 sq ft), Aspect ratio: 6.4
Airfoil type Root MAC118/NACA 2315, tip MAC118/NACA 3309
Weight Empty/Gross/Max TO: 1,680 kg (3,704 lb)/2,796 kg (6,164 lb)/2,796 kg (6,164 lb) for the A6M2
Max takeoff weight: 1,671 kg (3,684 lb)
Propeller: 3-bladed Sumimoto constant speed metal propeller
Engine: Nakajima Sakae 21 engine 14-cylinder air-cooled radial 1130 hp (see notes)
Fuel cap.: 518 l (137 US gal; 114 imp gal) internal and
Top speed: 600 km/h (370 mph, 320 kn), 533 max, 333 cruise at 4,500 m (14,930 ft)
Climb rate: 15.7 m/s (3,090 ft/min), 6,000 m (20,000 ft) in 7 minutes 27 seconds* A6M2
Wing Loading: 107.4 kg/m2 (22.0 lb/sq ft)*
Endurance: 1,870 km (1,160 mi, 1,010 nmi)* A6M2
Ferry Range (straight A to B): 3,102 km (1,927 mi, 1,675 nmi)*
Service ceiling: 9,800 m (32,200 ft)
Wing Loading: 93.8 kg/m2 (19.2 lb/sq ft)
Power/mass: 0.3161 kW/kg (0.1923 hp/lb)
Armament 2× 7.7 mm (0.303 in) hood, 2×20 mm wings guns
Other payloads 1x 330 l (87 US gal; 73 imp gal) drop tank* A6M2

The A6M in action

Type 0 A6M2 taking off from IJN Akagi for the Pearl Harbor attack

First engagements over China (1940-41)

As said above, its the flight group Yokohama Kukutai, that cemented the reputation of the aicraft over China, based in Hankow. The kill ratio obtained at the time was simply demential. It was way above that of the F6F later in the war, and was not kept as high due to the degrading quality of the pilots, opposition and context later in WW2. So the overall picture was far less favourable, and after starting on a 12 to 1 kill ratio, from mid-1942 it rapidly started to fall, until reaching by late 1942 and early 1943 something closer to 1:1. By mid-1944 it has been radically inverted to 1:12, and even dug deeper.

The first pre-series A6M2 with the 12th Rengo Kōkūtai started operatuins by July 1940 and on 13 September 1940 had at last their first victories when 13 A6M2s led by Lieutenant Saburo Shindo, escorting a group of G3M “Nell” bombers over Chunking repelled the attack of 34 I-15s and I-16s and claimed 27 of them for no loss. However four Zeroes sustained some damage, and until their retirement in September 1941, they had claimed 99 Chinese aircraft, local conservative figures, and 266 according to Japanese sources. A massive divergence which is quite common at the time and did not help historians today.

By early 1941, the presence of the A6M spiked, well helped by a superior range, many based at Hankow and recently captured airfields to help Japanese forces progessing into the mainland, and from carriers close to the coast, the assigned area of operation of the IJN. But this grow was done at more a limited pace from mid-1941, with the introduction and testing of the A6M3, of which only a few preseries saw action. Air groups were soon back on carriers and back home for extensive training in preparation for future operations. In fact it was even supposed to be withdrawn already in the late summer of 1941 (So late August to early to mid-September). Therefore, in the fall of 1941, all sights of the A6M made by AVG Flying Tigers were actually cases of mistaken identity. However there is the Gerhard Neumann case, a German-born refugee which was part of Chennault’s team. He allegegly reconstituted several downed/forced landed zeros as late September 1942, so a full year after Japanese allegedly retired it from the area;

However, there are missing records for some IJNAF units, which could have led to believe they stayed behind, probably with the earlier A6M2, now superseded on first line service by the A6M3. And there were the Tainan Kokutai Zeros, operating as far as north of Hainan Island. On November 22, 1941, a composite fighter squadron attached to the 22nd Air Flotilla HQ was created to participate in the fall of Singapore, 14 A6M2s model 21 (Tainan Air Group) plus 13 A6M2, same model, from the 3rd Air Group flew via Saigon and Hainan Island to be based at Soc Trang, south of Saigon by December 1941. Two made emergency landings on the Luichow Peninsula. But they were not lost to enemy action from the AVG, only recuperated from scattered part by Neumann. The Chinese AF was indeed the first to have a more precise opinion on the warbird, when an A6M2 the pre-production batch, serial V-110 was recuperated in good general state on the Fainan Island, examined on 18 September 1940 by a mixed US-Chinese team led by Neumann. The crucial intel however was very slow to enter ONI database (The US weren’t at war back then).

The A6M3 and early pacific operations 1941-43

In late 1941 in preparation of the operation against Pearl Harbor, all A6M3s were stationed on carriers and in home island reserve units. Apart a few A6M2s in Indochina as seen above, the Zero was entirely focused on the upcoming pacific theater. On 7 December, from all six fleet carriers of the Kido Butai, some 521 Zeros took part in early operations, including 328 in first-line carrier units. Not all took off that day, only a fraction, as a second wave was prepared, and the remainder were kept for CAP. The Model 21 became the common encounter in these early weeks in December 1941 and January 1942, which staggering range of 2,600 kilometres fooled the US intel and high command. At Pearl, PBY searched in vain for the carrier fleet, which in reality was stationed far more to the north, based on the supposed range of the A6M. The appearing over distant battlefronts of the A6M seemed to indicate they were far more of them than in reality.

These encounters soon created a psychosis in USN and USAAF pilot’s mind, as the previously “pale copy of…” seemed on the contrary invincible. Zeros becalme quickly the bete noire of Pacific pilots, and “zeroes” were seen everywhere, even though these were often “Oscars”. This alleged superiority was not completely well funded, as its early opponents like the Brewster Buffalo on the British side, never were a match to start from. But when the FAA started to introduced the spitfire in this theater of operation, pilots were surprised of the almost supernatural dogfighting abilities of the A6M, comparating quite well with the Me-109. Some even found it superior. By late 1942 when the FW.190 appeared on the western front, both were easily compared. The A6M3 could out-turn the Spitfire with ease and sustain a climb at a very steep angle while having thrice the range.

A lot was learned at Corea Sea in May, at Midway in June, and Guadalcanal from August 1942. Allied pilots soon developed tactics playing their strenght. Avoiding dogfight and instead swoop down from above in a high-speed pass and firing a quick burst, then back up to altitude. The F4F Wildcat applied them with success at Guadalcanal and practiced a type of high-altitude ambush, using the early warning system provided by Coastwatchers and radar. They were deduced from reports in China of those used by Chennault, the “boom-and-zoom” tactics against the equally agile Nakajima Ki-27 “Nate” and Nakajima Ki-43 “Oscar”. AVG pilots used their P-40s strenghts in the same way the F4F.

The captured restored A6M5 in flight in 1944. After the Aleutian A6M2, it brought significant improvement to allied intel on the new model, that most pilots found impressive for its low power compared to allied standards.

Lieutenant Commander John S. “Jimmy” Thach, USN ace, also introduced the “Thach Weave”, a formation of F4Fs some 60 m (200 ft) apart. If one was attacked, the remainder two would turn toward each other and surge behind the attacker. If the Japanese pilot then turned to disengaged, it would present its flank by the bait’s wingman. This was the main tactic used at the Battle of Midway and also in the Solomon, until the gradual retirement of the Wildcat. Both Coral Sea and Midway saw a large portion of the best and more experienced IJN pilots lost. Something the Kido Butai never recovered. Already during later engagements like at Santa Cruz and in general over Guadalcanal, pilot experience started to swing to the US side.

Although many officers were critical of the Wildcat, speaking of a “sluggish cat” with too short ammunition storage, Japanese pilots had a somehwat different opinion: Japanese ace Saburō Sakai for example was impressed by the toughness of opponents, as the only brake to the Zero’s total domination:

I had full confidence in my ability to destroy the Grumman and decided to finish off the enemy fighter with only my 7.7 mm machine guns. I turned the 20mm cannon switch to the ‘off’ position, and closed in. For some strange reason, even after I had poured about five or six hundred rounds of ammunition directly into the Grumman, the airplane did not fall, but kept on flying! I thought this very odd—it had never happened before—and closed the distance between the two airplanes until I could almost reach out and touch the Grumman. To my surprise, the Grumman’s rudder and tail were torn to shreds, looking like an old torn piece of rag. With his plane in such condition, no wonder the pilot was unable to continue fighting! A Zero which had taken that many bullets would have been a ball of fire by now.

The A6M4 and late pacific operations 1943-45

The later years, after the arrival of the F6F and F4U in very large quantities and with better, more experienced pilots, the A6M5, despite being the largest production of the type, largely thanks to Nakajima, already overworked with Army fighters and countless others, met it’s demise. Despite all attempts to modernize it, the light initial structure could not be up-engined, up-armed or beefed up much in any ways. Many attemps made until the end of the war led to small experimental series only.

Until the epic Battle of Leyte in October 1945 when the IJN committed its last reserves, the number of fleet carriers dwindled dow gradually, and the great replacement plan of the new armored Taiho class and lighter Unryu class failed to materialize. Post-Midway, the fleet still had the two large Shokaku class, the Jun’yo, Zuiho, Chitose pairs, and a cohort of smaller escort, on which the A6M could still operate, but both Taiho and Shinano had fairly short careers (a single sortie for the latter!), while none of the new and promising Unryu class was really operational in time, most even never completed.

After the catastrophy of Midway, further losses at Santa Cruz and the long attrition campaign of the Solomons (notably the 1st and second battle of Guadalcanal), the Kido Butai was gradually eviscerated. Already outmatched (marginally depending on the pilot) by USN/USMC models, the USAAF also introduced a perfect “zero killer” as the powerfully armed Lockheed P-38 Lightning, which four “light barrel” AN/M2 .50 cal. Browning machine and 20 mm autocannon in the nose could be fatal in a single short burst to the A6M, whicle being able to pick its targets thanks to their speed, and even equalling the A6M in range thanks to their configuration.

The amazing raid to eliminate admiral Isoroku Yamamoto (Operation Vengeance) is a good example of this. 18 P-38G fighter aircraft from the 339th Fighter Squadron arrived on the aerial convoy of 2 G4M1 bombers covered by six A6M3 fighter aircraft, after making a 600 miles out to the target, 400 miles back (1,000-mile total with extra fuel allotted). So after arriving, pilots were already too short of gazoline, to engage in any dogfight and used their speed and surprise to shoot down the two bombers, without engaging the Zeros, and then quickly turn back, loosing one P38G for a single A6M3 damage during the engagement.

The A6M5, still somewhat underarmed compared to the six Brownings 0.5 of the Navy fighters was hard-pressed but it’s main asset remained always in the hands of a skillful pilot as still, it was able to maneuver at least as well any opponents, and being still deadly in competent hands. Many aces of the 1940 era were still alive, although promoted and spared combat as commanders, to form the new generation of 1943, 1944 and 1945 pilots. Shortages of materials also started to impair construction and cause some delays, while quality generally dwindlded down, notably for the engines. While the A7M2 Reppū was awaited all along 1944 and into 1945, the A6M5 went on soldiering until the famous June 1944 “Turkey Shoot” of the Marianas, where the last commander and flying officers with enough experienced were shot down.

By October 1944, the “bait fleet”, Vice Admiral Jisaburō Ozawa’s “Northern Force”, could only sent a limited number of fighters, to lure out Halsey’s TF 38. Ozawa’s tempting decoy actually had only 108 aircraft on the six carriers. The largest par of which were indeed A6M5s. Overwhelmed by several fold more fighters sent by Halsey, in two waves, they were nearly all shot down but a few.

A6M5 Model 52C prepared in Kyushu for a Kamikaze operation over Okinawa.

Afterwards, apart some incursions around iwo Jima and last ditch attacks over the Philippines, the longer Okinawa campaign coincided with the start of Kamikaze operations. In these, the improperly trained pilots of the 1945 wave, were soon mixed with students reciving the most basic training.

These A6M5 were not the best platform for such missions as they carried a small bomb load if any, and the ventral space was used by a droppable fuel tank. In Kamikaze attacks, not all fighters were destined to end as “missiles”. Trained pilots were preferred to escort the composite flights, and defend it against incoming fighters, always detected in advance by radar, until low-altitude flights were attempted by more experienced groups. The A6M5 was seconded in these operation by the fresh (May 1945) A6M7, better provided in bombs, and properly used for Kamikaze attacks, not escort.

The army rivals: “Oscar” and “Frank”

Unlike the Navy, and just as for the previous A5M/Ki-27 duel, the inter-service rivalry prevented the adoption of a Navy fighter. Both branches had similar specifications and Nakajima knew about Mitsubishi’s prototype in development. They choose to adopt the same basic philosophy as the Army asked the company to develop the fighter quicker. Compared to the Zero there were two major differences: It was to be even less rugged (land based fighters were less “tough” than their carrier counterparts) and had less range. Perhaps it’s why development ended sooner, and Nakajima’s prototype flew a month earlier.

In early 1942, unlike the Navy which just upgraded the A6M while a successor was in the works, the Navy decided to create a brand new fighter, the Ki-84 Hayate (“Frank”), which in many was was superior to the A6M5. In fact it was perhaps the very best Japanese fighter of WW2, more powerful and beter protected the Zero could ever dream to be. Its equivalent, the A6M7 “Reppu”, for several reasons, was never ready in time (see later).

Ki-43-IIb Hayabusa “Oscar” (1st Air Combat Regiment, 1st Company, 1st Squadron, Home Defence 1943)

Compared to the A6M3, it’s contemporary, the Ki-43, which first flew in January 1939, earlier than the A6M, on April 1, 1939. Also it was also lighter, and in comparative tests, out-turned the A6M2/3/5 at low altitude, but was slower at 320 mph versus 330 mph (A6M3) or 351 mph (A6M5) with aslo a slower climb rate. Alsi it’s armament was way too light, with just two 7.7 mm MGs versus the Zero’s two 20 mm (0.787 in) wings cannons. It proved also difficult to uprade with armor and self-sealing tanks without degrading it’s performances, unlike the A6M5.

On the long run, before replacement came with the Ki-84 in 1944, the Ki-84 was out-done by the A6M5 in any corner, even the late Ki-43-III “Ko” (Mark 3a) introduced in December 1944 with the JAAF. It had a slightly improved Sakae engine, individual exhaust stacks for 354 mph at med altitude but the same twin HMGs. The Ki-43 “Otsu” (Mark 3b) had the Mitsubishi Ha-112-II radial engine and two 20 mm (0.79 in) Ho-5 cannon, but the structure could not handle these and the Ki-84 in development looks more promising.

In between the Ki-43 and Ki-84 appeared the Ki-44 Shoki “Tojo”. Nakajima’s engineers in 1940 started developing a new interceptor as a private venture based on the Ki-43 cell, heavily modified, with a new engine. Eventually, a Japanese Army Air Force specification was emitted, calling for a maximum speed of 600 km/h (370 mph) at 4,000 m (13,130 ft), reached in five minutes. The new interceptor featured the in-house Ha-41 14-cylinder double-row radial engine intended for bombers inistially.

As it was larger, the fuselage was strenghtened and enlarged, but otherwise shared many points with the Oscar still. All in all, production was slow, with an average of 50 monthly, peaking at 85 in April 1944 and really starting in February 1942, with many-production models made from August 1940. The 1223 “Tojo” mostly made operated from Japan to intercept bombers, and was the equivalent of the later Navy J2M. It’s development work paved the way for a more agile, less specialized model that became the Ki-84.

Ki-84 Hayate “Frank” (1943) (Author’s illu)

The Hayate was probably the best mass-produced fighter of the IJA (Imperial Japanese Army) in WW2. In performances it was superior to the liquid-cooled powered Kawasaki Ki-61 Hien “Tony” but inferior to the Ki-100, the same re-engineered with a radial, something a bit counterintuitive. The IJAAF Ki-100 by coupling a Mitsubishi Ha-112-II radial to a Ki-61 fuselage in 1945 was marginally better as an interecptor. It was too little, too late however.

The span of service of the Ki-84 and production, more than 3,514 so less than the A6M5 total production, which added to the “Oscar” (5,919) amounted to circa 9,500 so a bit less than the Zero, made it a good-all around package of performances, ruggedness and availability. Engineers had lightened the Ki-43 so much that it was obvious it was severely constrained all-around, to improve the engine, protection or armament. A brand new model was necessary, this time, much strongly built but with also a far more powerful radial engine in order to compensate.

It only flew in April 1943, so well after the A6M5, with a 1 800 ch Nakajima Ha-45-11 Homare (four variants, the last, 21, output’s was 1990 hp) and top speed of about 580 to 630 kph, for a 10,500 m ceiling. Armament was way superior, with two wing 20 mm guns and two 12.7 mm heavy machine guns in the nose. The pilot was protected by an armor plate behind, and extra armor was added to sensitive parts, and there were self-sealing tanks. In short, resilience was much better, and compared favourably to the A6M5 whih still inherited from the A6M2 “flimsiness”.

But since they were less common, allied encounters were rarer and pilot’s impression dificult to assess. After the war, speed tests with captured Ki-84s showed it was comparable to or better than the P-51 Mustang and P-47N. It aldo kept the edge in maneuverability against the P-47, P-38 and Chance Vought F4U Corsair, and some pilots allegedly said given it’s reputation “forget it, it’s a Frank”. Only the lack of experienced pilots prevented its success, as the last produced were squandered with rookies in Kamikaze missions.

Zero Aces

IJN Pilot Abe on IJN Akagi, posing in front of his Zero.

The basic unit called “Kōkūtai” or “air group” (航空隊), specific to Navy air groups. A Kōkūtai could be based on land or aircraft carriers and its dotattion could vary considerably, upt to several hundreds aircraft, like the 343 Kokutai (see later). One famous carrier-based group was the 652nd Kōkūtai. Each of these was subdivided into Hikōtai (“squadron”), three per Kokutai. In the IJA the equivalent was a Sentai.

The Tainan Kōkūtai based in Formosa inb 1944-45 became the most famous group, a nest of aces. This group operated from Rabaul in New Britain and started its rampage in the Philippines by early 1942, the Dutch East Indies, New Guinea and and mainland Japan towards of the end of the war. Saburō Sakai was one of its leading aces. The IJN Air Service organized an “all aces” elite unit, the 343 Kōkūtai, equipped not with the A6M5 in late 1944, but with Kawanishi N1K2-J fighters under orders of the famous Minoru Genda. This one of the rare “veteran” true fighter units among many Kokutai which basically were spent in Kamikaze missions.

Other veteran pilots flew also with the 601st Naval Air Group (225 aircraft of all type, nominal strenght), which operated with the 3rd Fleet (15 February 1944–9 July 1944), the 1st Carrier Division or Kido Butai (10 July 1944–9 February 1945) and the 3rd Air Fleet (10 February 1945–postwar). In it were operating the 161st, 162nd, 308th, 310th, and 402nd Fighter Sentai. They notably operated from IJN Taihō, Zuikaku and Shōkaku (symbols 311/11, 312/12 and 313/13), taking part in the Battle of the Philippine Sea, the Battle of Iwo Jima, Battle of Okinawa and the defence of Japan, flying the A6M5 and N1K1 in 1945.

  • Tetsuzō Iwamoto: 94 (14 in China and personal claims 202 kills)
  • Shoichi Sugita: 70 (some sources: 80)
  • Saburō Sakai: 64 (2 in China)
  • Takeo Okumura: 54 (4 in China)
  • Hiroyoshi Nishizawa: 36 official (102 claimed)
  • Toshio Ohta: 34
  • Kazuo Sugino: 32
  • Junichi Sasai: 27
  • Sito Origami: 10 (9 in China, 1 disputed)
  • Toshiyuki Sueda: 9
  • Kunio Iwashita: 9
  • *Note: Many of these pilots transitioned from the A5M (China) to the A6M, and a selected few survivors piloted the N1K1 in 1945.

    Flying the A6M-2N “Rufe”

  • Master Sergeant Kawai: 4
  • Master Sergeant Maruyama: 4
  • In Home defence

  • Captain-Petty Officer Takeo Tanimizu: 8 (A6M5c)

Revised IJN fighter attack formations in 1942

Zero Adversaries

The A6M2 clearly dominated the sky when pitted against Chinese Polikarpov 1-15 biplanes and 1-16 monoplanes, but from late 1941, the RAF Buffalos, USAAF P-36 Mohawks. Due to its low wing loading it could out-turn any of them in all dogfights and just dominated any encounter. Some equality was found when encountering the P40B Tomahawk and Hawker Hurricane, but only pilots made the difference, using their best assets and using hit and run tactics. Chennault used to dive into Japanese formations to take on a few aircraft before running out of range or in clouds.

The Zero started to find even better opponents in the P-38 Lightning and even the stubby F4F Wildcat. P-38 pilots selected their moment of fight, based on their superior speed, notably better altitude, ready to pounce for an eye blink killing blow thanks to their armament. The F4F was more agile, and could, if well used, even outperform the Zero in some corners, but mostly taking punishment and escape.

The third generation of American fighters mounted the F6F and F4U and they dominated dogfight by sheer power, speed and strength. Both F4U and F6F, even with relatively inexperienced pilots, could take on the Zero with confidence in any conditions, and this was coupled with overwhelming numerical superiority. The last Zeros fought off B29s escorted P51 Mustangs over the home islands, and between the fierce self-defence and high altitude, speed offered by the first and the intrinsict qualities of the second, equally at home at this altitude, A6M5 were no longer a match.

Zero vs. Chinese I-153 & I-16


I-16 Type 5 of a Chinese ace, 1940. Author’s illustration

The bulk of the Nationalist Air Force in 1937-39 was equipped with the I-153 biplane and I-16 monoplane. The latter was still enountered well into 1943 and so reports of duels between these and the A6M2 are known. The small Polikarpov I-16 “Ishak” (Donkey) was the beloved, main first line fighter of the Soviet Union of 1941 despite its age.

At Nomonanh in 1939, the adversaries of the Soviet Air force were IJAAF models, so likely the Ki-27 “Nate” in majority as the Ki-43 was just getting started. The Navy could however had seen some combat in China over Mandchuria in 1945 during the Soviet invasion of August, as it had the responsability of coastal areas. But at the time, these units probably flew second-line, worn-out A6M2, and combat reports of combat are scarce. By that time, the Soviet AF flew the Mig-7 and Yak-9, which were infinitely superior, with veteran pilots.

Zero vs. US P40E Tomahawk


Famous P40E of Chennault’s “flying tigers” in 1941. Author’s illustration

The P40 was derived from the P36 Hawk, a 1935 (first flight) modern all-metal, enclosed cockpit, with rectracting undercarriage and stressed aliminium skin fuselage and wings model. It equipped USAAF units in 1939 and still largely in 1941 while being replaced by the P40. The Zero would deal with the P36 in China already. On 11 January 1939, five Hawk 75Ms of veteran CAF 25th Fighter Squadron Cdr. Liu Yijun defended Chongqing, proving superior to the I-15 and I-16 and eventually the 75A-5 was built under license in China until moved to India (RAF Mohawk IV). For top speed and agility it was easily dominated by the A6M2.

Curtiss improved massively over the design by just fitting on the prototype XP-37 an Allison V-1710 inline engine with cockpit moved further to the rear of the fuselage. The final product, called YP-37 (13 built) and then XP-40 with the Allison V-1710 became the prototype of the Curtiss P-40 Warhawk. The latter first flew on 14 October 1938 and started to replace the P36 in USAAF units in 1939 and until December 1941, became the main USAAF fighter. Its top speed of 538 km/h (334 mph/290 kn) at 15,000 ft (4,600 m) was on par to the A6M2’s 533 km/h (331 mph, 288 kn) at 4,550 m (14,930 ft), but it never was as agile.

Still, the P40E Tomahawk flew by Claire Chennault’s squadron for the Chinese Nationalist Air Force met the A5M and A6M and was among the first to clearly report and warn the USAAF about the performances and agility of the new fighter. He also learned how to best deal with it, avoiding dogfights and devising adapted tactics, a precious set of advice that was officialized after the capture of a Zero and extensive tests. A bit like the Wildcat, the P40 could still count in its superior construction to survive battle damage. The few that were still around in late 1942 when the A6M5 appeared were hopelessely outmatched.

Zero vs. P38 Lighting


P-38F of USAF top ace Richard Bong in 1944 – Author’s illustration

The incontestable winning point of the P-38 design was its superchargers, worked on for years at NACA -predecessor of NASA- which enabled superior performances to anything else that flew at the time, thanks to the light fuselage and peculiar twin-boom design combined to two very powerful inline engines, a pair of Allison V-1710 V-12 liquid-cooled turbo-supercharged piston engine rated for 1,600 hp (1,200 kW) each, enough for 666 km/h (414 mph/360 kn) based on 1,425 hp.

At high altitude, reaching 44,000 ft (13,000 m) the superchargers gave it superior performances, well completed by a combat range of 2,100 km (1,300 mi, 1,100 nmi) versus 1,870 km (1,160 mi, 1,010 nmi) for the A6M2. It was still faster at all altitude ranges than the A6M5 and could escape easily in dives, reaching in rare cases 800+ kph but dealing with extreme air compressibility issues, notably strong vibrations.

For agility however, it was noted as inferior to the A6M5 and only the pilot’s respective skills generated a more balanced result. A twin-boom plane generally had more drag than a monocoque, single fuselage model. However the model generated plenty of aces, like Richard Bong (40) or Thomas McGuire (38), top aces of the USAAF, which preferred it over the M51 Mustang. Like the Navy pilots they were perfectly briefed over the advantages and weaknesses of the A6M and they had in the nose the most powerful armament of any US “light” fighter in this war, one Hispano M2(C) 20 mm cannon and four M2 Browning machine guns in the nose. One or two 20 mm HE rounds could tear apart a zero while the P38 presented almost the same ruggedness as the Corsair and Hellcat.

Zero vs. Grumman F4F Wildcat

F4F-3 of ace J.S. Thach

F4F-3 of ace J.S. Thach from VF3 “Felix” in 1942.

The big difference between the two was that the Grumman F4F Wildcat was designed based on awaited specifications from the Navy, for a modern monoplane, and the company used the biplane F3F as a base. When the specs arrived some adjustments were made and it entered service as such. It’s not before encounters were made at the battle of Wake on December 8 and later on the 23th for the surviving fighters, that the F4F had a glimpse about its main adversary for the upcoming two years (and more). Indeed, even after its replacement by the Hellcat, the valiant F4F was small enough to fit on escort aicraft carriers, and most of them (of the Casablanca class) were tasked to defend amphibious fleets in all operations. Therefore, the F4F went on to fight not only the Zero until 1945 but even other late models.

Many aces were made on the F4F and pilots soon devised the best tactics to stay alive when encountering the Japanese warbird. They could not count on defeating it at its own game -in a barrel loop and tight turns-, and instead, try to hide in the clouds if the engagement started badly, or more commonly dive, or just count on their own resilience and ability to still manoeuver at extreme speeds. Many tactics based on this were devised, and it took about a year before they started to be told to young recruits until late 1942. One of the best was always the dive: The Wildcat could dive at 400+ mph while the Zero’s controls began stiffened at 250 mph and were unmovable at 350 mph, beyond that, its structure was just not strong enough to risked grave damage. Marc Liebman, Captain USN (ret) in particular gathered all reports on these encounters and deduced this and other advantages Wilcat’s pilots could count on. This particular tactic allowed the F4F to choose to leave behind its follower and return later or out-turn the A6M at the first occasion.

Among these, the Wildcat could also take on hard G manouvers the Zero cannot follow, since the latter still has a traditional float type carburetor. The engine will just starve out trying to catch the Wildcat in those. At a macro level also, most Zeros did not have radios and could not coordinate properly their attacks or defense. Also if the Wilcat could manage to stay alive when fired at, the Zero was limited to 10 seconds of ammunition for its 20mm cannons, and next its machine guns were virtually useless against the F4F, which could absorb enormous punishment. The F4F could never be underestimated. It was not “easy meat”, even mith moderately trained pilots. There is a reason why it was maintained so long both in the FAA and USN.

Zero vs. Grumman F6F Hellcat

F6F-3 of ace Alex Vraciu from CV-16 USS Lexington summer 1944.

Unlike the F4F which was designed in the complete ignorance of the A6M, the F6F was created with it in mind, specifically, taking in account as many pilot experience as possible. All the strong points of the Wildcats were just pushed forward. With more power, more sturdiness, a better armament, the “orgre” that was the Hellcat when it arrived in 1943 started to completely dominate the A6M3. However, it started from a long way away. The previous F4F compared by a young pilot of that time as “a little beer bottle of a plane with a battery of .50-caliber guns in its tiny wings.”. Despite a more powerful, 1,200 horsepower engine, its speed was limited to 318 mph, compared to 331 mph on the A6M and tactically a range of 770 miles compared to 1,950. Engineers at Grumman were confident to radically improve on both points, but especially on the first.

The process started in 1938 already when the F4F was not even in service, engineers worked on a new version redesigned around the massive Wright 14-cylinder, 2,600 horsepower in development. But t’s really when a zero crashed almost intact in the Aleutians that Grumman’s engineers had a clearer picture of what they had to beat. But they persisted on their design, with some adjustments. But the luck of diverging schedules, Grumman had its hands on the even more impressive Pratt & Whitney 2000 hp R-2800 Double Wasp, which formed the beating heart of the new warbird.

As a result, at 380 mph the F6F outpaced the Zero at optimum altitude, had a better, 37,000-foot service ceiling and above 10,000 feet climbed as quickly, while being even more faster in a dive. For range they still performed at 400 miles from their carriers of needed. And when it came in 1943, the pool of experienced pilots in the IJN had been already reduced significantly by the F4F. F6F pilots were essentialy now fightng a downhill battle. Event the A6M5 could not regained the advantage. Both were now geavenly matched and IJN pilots had in turn to learn how to to beat the F6F and avoid its strenght, looking for close dogfights and counting on surprise.

But the amazing ruggedness of the F6F, based on raw power, was always very efficient. In February 1944 for example during an attack on Truk, Lt. Eugene A. Valencia escaped attacking Zeros, was hit, but then turned back hard to make a surprising (for them) head-on run, guns blazing, managing to shoot down three A6M5s straight away. In June 1944, the “great Mariannas Turkey Shoot” was not longer an even affair between worn-out zeros and inexperienced pilots. It just turned ugly for the Japanese, earning for the F6F it’s record kill ratio, confirmed time and again until the end of the war.

Indeed its qualities as “kamikaze killer” was also considerable: Over Okinawa on April 17, 1945, four Hellcats from USS Yorktown (ii) detected an enemy formation of some 40 light bombers and zeros from 25,000 feet, and a limited two-airplane Hellcat section dove and attacked, the other section covering them, and they then reversed course. This particular maneuver broke the kamikaze formation with 17 confirmed kills in a matter of minutes. This tactic became a favorite and mowed down these formations, leaving only scraps to hit the steel wall of the task force’s AA.

Zero vs. Chance-Vought F4U Corsair

F4U-1 “Gus Gopher” (Wilbur “Gus” Thomas) VMF-213, Guadalcanal 1943
The prototype XF4U-1 flew at the time the A6M barely reached production. It would become from 1943 one of its fiercest adversary from its introduction in December 1942.

After the F6F, the F4U was the other “Butcher bird” of the USN, or to be more accurate at first, of the USMC. The “whistling death” from Chance-Vought was making its maiden flight two years before the F6F Prototype. However soon it appeared plagued by two issues that prevented adoption as a main carrier-based model, plus teething issues that delayed its entry into service, and the F6F was chosen instead by December 1942: Lack of visibility from the nose, crucial when landing as the flying deck was hidden from view, and linked to the first, its innate propensity to “bounce off” the deck, missing all arrestors cables. Since the USN was hiring plethora of new young pilots to populate its numerous air groups stationed on the Essex-class fleet carriers by in late 1942, they wanted an easier models, so the F4U was ruled out and passed onto the USMC, quite eager to replace its antiquated models. It’s ruggedness made it perfect to land on summarily prepared airfields, and visibility was no longer an issue.

In the hands of the Marines, spread over many airfields in the central Pacific, the gullwing terror was able to regain supremacy over the Imperial Japanese Army Air Force, as did the F6F from the Task Forces. In addition to the USMC, the Fleet Air Arm also inherited this model, which was found largely superior in many ways to the seafires and sea hurricanes still populating British carriers in 1943. With a new optical guiding system, the visibility problem when landing was overcome, and it also helped in fine to solve the “deck bouncing” issue, now far more precise. So much so that in late 1944, the F4U made a comeback on USN fleet carriers and doubled the F6F as a fighter bomber, it’s specialty. F6F and F4U were hand in hand pummeling the home islands in 1945.

Now compared to the Zero, the main advantage of the F4U was its superior speed. The first version was faster than the A6M3, and subsequent versions stayed aloways superior in this regard to the A6M5 or Type 0 model 52. The other advantage was of course its raw power, far superior to the A6M, with the last version F4U-4 had a modified dual-stage-supercharged 18W engine, which when injected with a water/alcohol mixture reached 2,450 hp (1,830 kW). It was almost double of the A6M5 at the time. As the F6F, the structure of the F4U was extremely rugged and it proved quite resilient in combat, being capable of absorbing extra punishment the A6M5 could not.

In the first wave alone of the “Great Mariana turkey shoot”, 42 out of 60 Japanese planes (most being zeros) were shot down for two F6F and a single F4U conceded in return. Like F6F pilots, still, they learned hown not to dogfight the A6M5 and instead, use their armor and speed to blow them apart in high speed passes instead, denying them a close range in equal terms. In 1945 USN stats would give a 11:1 kill ratio in favor of the Corsair versus identified A6M Zero in combat. Although the radical decrease in pilot quality should be taken in account, it was still compensated by a better model overall compared to the A6M2 or A6M3. That left still some margin of superiority to the F4U. USMC pilots meanwhile, were more used to combat land planes, especially the Ki-43 “Oscar” and Ki-84 “Frank” at the end of the war, but still encountered second line A6M2 and A6M3.

Zero vs. P51 Mustang

North American P51D F6D Mustang “The Flying Undertaker”, Ace Major William Shomo (6 victories), Tinian AB, spring 1945.

This fantastic fighter was designed in just 120 days as the prototype NA-73X flew on October 25, 1940. The initial goal was to create an assault plane powered by an Allison engine, not a fighter, and the early NA-73s and NA-83 were only ordered on paper by the British RAF. It took until 1943 before the idea emerged to escort bombers with long-range fighters, and the mediocre initial assault plane was remotorized by the Rolls-Royce Merlin (a match made in heaven), licence-produced by Packard. Some 15,000 airframes were created between Los Angeles and Dallas plants. With its pressurized cockpit and its trademark design innovations, like the “laminar flow”, bubble canopy, landing gear, mass production simplifications, conical lofting, and general good looks, courtesy of “Ed” Schmued, the “best USAAF ww2 fighter” also generated scores of aces.

Those were only encountered by rare A6M5 over the Home Island, after the capture of Iwo Jima and conversion into a massive air base. The latter operated scores of the massive B-29 superfortress, and for escort, their P-51 Mustangs. These highly dangerous missions lasted for seven hours, at the limit of range, with 3 hours flying over the open Pacific, one over their objective with fierce dogfights and 3h for the return to Iwo Jima. Losses over the open sea were frequent due to possible mechanical breakdowns or damaged planes over Japan due to AA, and pilots picked-up at sea always ended POWs with marginally greater chance of survival in 1945 compared to their earlier USN counterparts.

P51 taking off from Iwo Jima airbase, May 1945.

When air opposition dropped radically the USN started to used its F6F and F4U for ground attacks, and so was the P51. Starting in July 1945, 51 raids by the VII Fighter Command claimed to have destroyed or damaged 1,062 aircraft and 254 ships. Many A6M5 (produced until the last days of the war) were simply destroyed on the ground.

Never ready successor: A6M7 Reppu “Sam” (1944)

A6M7 Reppu Sam
Profile rendition of one of the prototypes

The A7M Reppu (“Strong Gale”) was planned as the successor to the A6M, since the basic frame of the A6M5 could be furrther upgraded and updated without completely redesigning it. The Navy was influenced in large part by the development of the Army’s Ki-84, and design work began in April 1942, at a time the Kido Butai was still intact (the battle of Coral Sea did not happened yet).

Mitsubishi’s chief engineer, the very same Jiro Horikoshi and his team, worked aoround the clock to the new prototype, and by July 1942, the Japanese Navy at last backed this officialy up with specific requests, redesignated the “Navy Experimental 17-shi Ko Type Carrier Fighter”. Top speed as requested was now to be 639 kph with a ceiling of 6,000 meters and a climb rate of that altitude in 6 minutes. For armament, it needed to have two 20-millimeter cannons plus two 13 mm HMGs while keeping the same maneuverability as the A6M3.

Horikoshi’s team soon found the engine suitable for the right performances but at that time instead of concentrating on it, Mitsbushi was completely absorbed into the construction of the G4M bomber and A6M fighters already, so the prototype was delayed quite significantly. So much so that unlike the Ki-84, the first A6M7 prototype flew on 6 May 1944. Right away, the promising engine did not delivered as expected: It was found to be underpowered.


War emergency was such that the Navy ordered Mitsubishi to stop development of the A7M, with a permission to continue, while not using resources to develop new engines. A7M development went on using the existing Ha-43 engine and basically the engineers were back at work trying to lighten the structure enough to regain performances. The first prototype with the Ha-43 engine flew on 13 Oct 1944 and managed to reach 628 kph (below the requested speed, but accepted due to the new engine), however its handling was even better than the A6M5.

However fate intervened again: An earthquake in the Nagoya region, added to the scarcity of resources caused by the Allied naval blockade further delayed production of the preserie, of which only eight aircraft were ready by the next summer of 1945, meaning none was deployed in any active unit. The few flying ones made test flights when avgas was available, but the A7M fighters would never see action and the remainder in construction or completion at various stages were captured at Nagoya by the occupation troops.

Of note it should be said that Mitsubishi was not “stuck” with the A6M. In 20 March 1942 first flew the prototype, and from December was delivered to the Navy a new non-carrier based fighter: The J2M Raider “Jack”. Thus rather disgracious and stubby fighter was entirely developed from precise specifications for a home defence fighter provided by a much more powerful engine, not compatible with the flimsier A6M5: The 1,044 kW (1,400 hp) Mitsubishi MK4C Kasei 13 14-cylinder air-cooled radial engine (prototypes) up to the Kasei 26a engine (3-speed supercharger for 1,820 horsepower (1,360 kW)) for high altitude. On the larger scope, these changed very little: Only 621 were produced, devoted to B-29 interception until the last day of the war. It was never intended as a carrier fighter, having no hook or reinforced undercarriage.

comparison A7M A6M
Comparison between the A6M and A7M

The navy also had another high performance fighter, from Kawanishi: Unique case in aviation history, it came from a floatplane interceptor, the excellent N1K Kyōfū “Rex” developed from May 1942 and introduced in late 1943 to replace the Nakajima A6M2-N “rufe”. It was developed into a land-based interceptor, the N1K-J Shiden “George”, the first J-1 flying in December 1942 and the first J-2 in December 1943. In all, 1,532 combined were delivered, a far cry to the 10,000+ of the A6M, but the very last N1K5-J Shiden KAI 5 powered by the HA-43 (MK9A) 2,200 takeoff hp (project only) was certainly very promising.

Preserved Zeros today

A6M3 at the Flying Heritage Coll.

A6M2 M21 at the Kawaguchiko Motor Museum, Yamanashi prefecture

Mitsubishi A6M Zero yamato-museum

A6M1 prototype at Junishikansen (Mock-up Replica, full size)

Many A6M5s were captured in various stage of completion when the home island were occupied. Most of these would make the bulk of preserved aircraft arond the world today. Most surviving Zeros for this reason are either A6M5, or are made up of parts from multiple airframes recuperated and restored over the years, procuring a bit more diversity in types and models. They are however referred to by conflicting manufacturer serial numbers. Some were picked-up in utterly wrecked condition, and have been reconstructed and restored by recreating the missing modern parts, to the point they only had few original ones. Most of the flying ones no longer have their original engines, replaced with similar American units. The “Planes of Fame Museum’s” A6M5 is the only one with its Sakae engine.

Flyable Zeros (outside reconstritutions based on the North American T-6 Texans with modified fuselages used in movies and series) are a few (3), but static ones could be found in Australia (2), China (1), Germany (1, replica), Indonesia (1), Japan (10), New Zealand (1), UK (2), and the US (15, including replicas and in storage, prending restoration).



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On airwar.ru
On warbirdforum.com
jstor.org dealing with the Zero, John F. O’Connell Air Power History Vol. 63, No. 3
On weaponsandwarfare.com
ONI plates on the zeke 52
ONI handbook IJN A6M
Cat against the sun – airforcemag.com
Speaker Briefing: F4F vs A6M Setting the Record Straight, Marc Liebman, USN
Same, more detailed
On Peter Lewis’ site 1985-1999
wiki commons, cc photos


Hellcat vs Zero, by two vet pilots.
A6M Zero – Japan’s Mystery Machine. Armoured carriers channel
Pacific Legends Day – F6F Hellcat – A6M3 Zero – Flying Heritage Collection
Drachinifel’s The A6M Naval Carrier Fighter – Zero or Hero?
The Rise and Fall of the Japanese Mitsubishi A6M Zero
The A6M Zero – Documentary (1/4)
Zero: Legend vs reality – Military Aviation History

Model Kits

A fair number of manufacturers had been on this legend for many years and it’s not over. All Japanese manufacturers and many others, among which, classed by scales:
Eureka Hobby, Kyo 1:14, Cleveland Model & Supply, Guillow, Kyo, 1:16, Komet 1:22, bandai, Trumpeter 1:24, Doyusha, midori 1:28, Ace Whitman, megow 1:30, Hasegawa covered the 1:48 for example, and it is down to Pit-Road/Rainbow to crowd carriers at 1:350. 1:72 is of course the usual scale, covered by Airfix, and many others. See the full list below.
main query scalemates
On 1001hobbies
1:32 On Tamiya

Author’s Illustrations

Standard colours for JNAF combat aircraft varied over time. From 1940, it was light brownish grey (…).

From July 1943 dark green was applied to the upper surfaces with light grey or even natural metal lower surfaces. Engine cowlings were always black. The addition of lighter/darker green and grey spots here and there was done on the field and varied considerably from unit to unit. It was presumably an attempt at a blotch-type camouflage but paint was a rare commodity and there was little regulation on the matter, a bit like in army sentais. The red Hinomaru on both sides also differed. On the fuselage it was backed by a white circle for better identification from 1943 over dark green, and on upper wings, but on the lower wings they were generally were not outlined in white.

In 1944, this outline was often black. The factory-applied dark green paint was of degrading quality until the end of the war due to chemical shortages and wore out rapidly so that over time, it left the original light grey/factory finish appear behind, creating fatigue patterns acting as impromtu camouflages. Individual aircraft identification data on the port rear fuselage was in black with the unit/aircraft numbers painted across the fin and rudder in white or yellow, and sometimes red, although barely visible over dark green. In addition, Hikōtai leaders had extra identification bands as well as for flight leaders in sub-units. After the surrender as ordered by the allies, some wore surrender Markings with a dark green paintwork covered with washable white. The following profiles had been split for commodity between the three more common series, A6M2, 3 and 5, and a few prototypes plus oddball liveries. See also.

A6M1 prototype, Kagamigahara airfield, April 1939

A6M1 Navy 1st prototype, carrier qualifications, late 1939

A6M2 in 1940

A6M2 in China, 1940

A6M2, 12th Rengo Kokutai, Hankow, China 1940

A6M2 Lt. Minoru Suzuki, 11th Kokutai, Ame Iro, China 1941

A6M2b, Model 21, IJN Zuikaku, December 1941

A6M2 IJN Ace Saburo Sakai, Tainian Kokutai, Bali, Early 1942

A6M2 IJN Hiryu 1941-42

A6M2 Model 21, Rabaul, November 1942

A6M2 Model 21 Kasumigaura Flying Group, Japan, 1943

A6M2 captured by the USMC, Saipan, June 1944

A6M2 M21, 261 Kokutai, 1943/44

A6M2 Oitu Kokutai, February 1944

A6M3 m22 of IJN ace Hiroyoshi Nishizawa, Aichi prefecture, Kyushu spring 1943

A6M3 m22 of 201 Kokutai, Rabaul, New Britain, May 1943

A6M3 m22 of IJN ace Matsuo Hagiri, Buin, Summer 1943

A6M3 Model 22, 201 Kokutai, Ace Takeo Omura, Buin, September 1943

A6M3 m22a at Magwe, Burma, December 1943

A6M3 model 32 Tainan Kokutai, 2nd Chutai Buna, New Guinea August 1943

A6M3 m32 of Tainan Kokutai, 4th Chutai, same.

A6M3 m32 of 204 Kokutai, IJN ace Kenji Yanagira, Buin, April 1943

A6M3 m32 of 204 Kokutai, Munda, New Guinea 1943

A6M3 m32 of IJN ace Takeo Tanimizu, Tainan Kokutai, Formosa September 1944

A6M3 m22 in Saipan, June 1944

A6M5, Model 55, IJN Taiho, October 1944

A6M5b, 652 Kokutai, IJN Jun’yo, June 1944

A6M5 model 52, 231 Kokutai, Japan 1944

A6M5c (Model 52c), 721 Kokutai Jinrai 406/407 Hikotai at Miyazaki Air Base, Kyushu, 1945

A6M5a Model 52a, 256 Kokutai, Malbalacat Air Base, Philippines October 1944 (Battle of Leyte)

Model 52 modified as a fighter bomber, 301 Hikotai, 201 Kokutai; Early Kamikaze unit, October 944 (Battle of Leyte)

A6M5 model 52c, 332 (Interceptor) Kokutai, Narua Air Base, Japan summer 1945

A6M5 of 302 Kokutai, Atsugi Air Base, Japan, 1945

A6M5b of an unknown unit

A6L5 m52 Kokutai Genzan, Wonsan, Korea 1944

A6M5 m52 at Rabaul, 1944

A6M5c, 303 Sentai, 203 KoKutai, IJN ace Takeo Taminizu, 1944

A6M5c of IJN ace Tetsuzo Iwamoto 1944

A6M5 captured in Saipan with a factory unpainted livery.

A6M5b of an unknown Kokutai, note the paint fatigue

A6M5c from 352 Kokutai, Kasanohara Air Base, Kagoshima, Kyushu, March 1945

A6M5c of Tsukuba Naval Air Corp, Oita Air Base, Japan, July 1945

A6M5c of Tsukuba Flying group, early 1945

To come (if references are available): A6M4, A6M6, A6M7 and A6M8.


A6M Zero Chino California

Zero on Zuikaku, Indian Ocean raid, April 1942

Zero photo References on Wagner coll.
















































Nakajima B5N “Kate” (1937)

Nakajima B5N “Kate” (1937)

Imperial Japanese Navy, 1,149 built

The Main IJN Carrier Torpedo Bomber in 1939-42

The Nakajima B5N was completely unknown by US Intel before 1941, and vastly underrated (like most Japanese aviation, seen as mediocre western copies). Little was known that this model, albeit of the same generation, vastly outperformed the Douglas TBD Devastator, its rival at the time, which in all western publications was proudly accumulating records and “world’s firsts”. The B5N was simply faster and more capable overall. For some authors it was even the world’s best carrier-borne torpedo bomber when WW2 broke out, period. Best proof of that, the “Kate”, much like the “Val” was soon feared in the early phase of the Pacific Campaign, was never truly replaced and fought on the frontline to the end.

Distant Origins

The first Japanese aircraft were imported until by 1918, Lieutenant Chikuhei Nakajima resigned to establish his own aviation company in Ota, Gumma Prefecture in assoviation with Seibei Kawanishi, but they disagreed, both later creating their own companies. Chikuhei Nakajima went on with licensed aircraft but still worked on a proper model to fill both Army and Navy competitions. In 1921, Captain Sempill, with thirty British instructors were invited to evaluate the technical needs of the young JNAF. Herbert Smith (from Sopwith) was found at the head of Mitsubishi, soon creating the mediocre Type 10 torpedo bomber, entering service in 1923 on IJN Hosho. At the time all but a young Captain Yamamoto at the Kasumigaura Naval Flight Aviation School predicted their need over battleships.

Until 1929, development was still slow, as doubt prevailed for further development of the Naval Air Force (a similar downhill battle was led by Mitchell and his supportsr in the US). What did’nt helped to convince the general staff was the poor performance of early models. But the help of foreign advisers (another good example was Kawasaki’s Vogt, Mitsubishi’s Petty from Blackburn), helped Japanese designers gaining experience, and after purchasing whole series or planes to assemble, single examples were purchased for comparative tests, copying all features along the way. This was well known by the Western world that long believed the Japanese cannot do anything else but poor copies, until December 7th, 1941.

Captain Yamamoto however, back from his srtay at the Washington embassy, promoted vice admiral started to head the Naval Aviation Technical Bureau, pushing new models more in line with his scenario of naval warfare across the Pacific. This proces, started in 1931, and also concerning many other aspects like training and ordnance, ended in 1941, making at that tomùe the IJN probably the most powerful and efficient naval air force worldwide. Transitional fighters (9-Shi program) led to the excellent A6M “Zero”, while the dive bomber bomber led to the dreaful Type 99 (Aichi D3A “Val”) but Yamamoto insited for a for long-range land-based naval bombers as well (Mitsubishi G3M “Nell”, Mitsubishi G4M “Betty”) and for torpedo bombers wanted to replace the mediocre Type 89 (Mitsubishi B2M) for 1936, leading at first to the Type 96 Yokosuka B4Y, still a biplane limited to 277 km/h and 1,574 km. In 1937 already this was considered whoelly unsuficient.

A year prior however, in 1935 the 10-Shi specification were published, pushing the boundaries of what was capable for a modern torpedo bomber design. Performance were to be several fold higher, leading to the Navy to trust only two firms to came up with a solution: Mitsubishi and Nakajima, answering and soon retained. The programme at Nakajima was headed by Katsuji Nakamura’s team.

Design development

Mitsubishi B5M, it’s loosing competitor

The B5N was designed Katsuji Nakamura to replace the previous biplane, barely into service, internally designated as the “Type K”. 10-Shi specs for a naval carrier-based strike bomber called for 330 km/h top speed (min figure) that no biplane could match. Indeed at the time, the Mitsubishi’s A5M already reached 449 km/h and showed what a monoplane can achieve. The admiralty though was aware of yaw control in the last stages of the landing approach and was worried about achieving enough landing accuracy. Discussions led to think this issue of speed could be overcome by the use of flaps, a novelty rediscovered from WWI.

Mitsubishi studied with great attention the American Northrop BT bomber, which was imported in 1935 from the USA. It had a retractable landing gear and powerful engine, more than the Northrop A-17 “Shrike”. The latter also inspired the Kawasaki Ki-32, Mitsubishi B5M and Mitsubishi Ki-30. Douglas turned these into the TBD Devastator and SBD Dauntless and so Jiro Horikoshi believed these were to watch with great attention.

Meanwhile Nakajima worked around a new 840-hp Nakajima Hikari 2 radial engine, woven into a low-drag NACA cowl its new model also comprised a serie of innovative features like a hydraulically retractable landing gear. It was the first time such hydraulic system was created in Japan and issues were many. To overcome them took time though and Mitsubish translated this later into the 12-Shi spec program (A6M).

Meanwhile both also worked to have the new aircraft fitting inside always low and narrow carrier hangars, and ways to fold and maintained in flight the wings. Soon a rotary nodes system was created, in which wing consoles overlapped one another and power brought by Hydraulic cylinders placed in each wing. Also worked out for quite long was the trailing edge of the wing, and the designe of a more modern three-bladed variable pitch propeller.

First flight

Kate tested by the USN, US Navy (R. Francillion coll.)

The Type K prototype made its first flight in January 1937. She was able to reach 370 km/h in level flight, a record at the time for a torpedo-bomber. However as the full folding mecanism was not ready yet, trials urged the use of a lever inserted by a technician into the lower surface of the wing console. The Fowler-type flap mechanism was too advanced and not ready so it was replaced by a simplified device in which the entire trailing edge section turned. The variable pitch propeller also proved to be complex and was replaced at the last minute by a constant speed propeller. The second prototype had to be fitted with integral fuel tanks were inside the center section.

A parralel development, the Nakajima C3N (1936)

For the second prototype also, a new engine was adopted, the 770 hp Hikari 3 which presented the advantage of easy of removal and replacement. The definitive engine hood was well-rounded and the nose short, in full contrast to following models. After the first factory flights (the very first was made in January 1937), the Nakajima led the competition as opposed to the Mitsubishi B5M. It was ordered into production soon afterwards, under the full designation “Type 97 Carrier Attack Bomber”.

Competition won by Nakajima

ONI plate, B5N, CINCPOA, US Intel

The Mitsubishi 10-Shi answer was very similar, but more conservative in its technical approach, with a more elliptical wing, in part based on the Type 97 fighter, itself inspired by the Heinkel 77. However, the landing gear was non-retractable and it had prominent fairings, while the wings were originally manually folded. The engine, the 1000-horsepower Mitsubishi Kinsei had better takeoff stats than the Nakajima design maximum speed reached being 378 kph, ten more than the Nakajima’s 368 km/h.

However in the end, the admiralty decided not to produce this aircraft: Despite its better perforamnces caracteristics, the Nakajima design was chosen for production in standard, related to its greater development potential and more advanced technical solutions. The second reason was that Mitsubishi’s design staff was already struggling to modificaty the Type 96 naval carrier-based fighter and was involved in the 11-Shi specification calling for a dive bomber (won by Aichi with its D3A) while working on the 12-Shi program fighter (future Zero). In 1937, the admiralty nevertheless ordered 125 of the Mitsbishi model designated B5M1. Designated Type 97 Model 2 naval carrier-based strike bomber, the allies would codename these “Mavis”. It was mostly used as a land and naval carrier-based attack bomber for anti-submarine patrols in South China and Hainan and was gradually retired after 1943.

Final design

The pilot sat in front of the cockpit but forward visibility was reduced while on the ground, a common issue at the time on these tail down models. It was in part due to the high wheeltrain legs in relation to the cumbersome torpedo below. It was ensured it’s tail would not hit the deck. However it was also assumed that for landing, the latter would have been launched or jettisoned anyway.

Good visibility nevetheless for the final approach and deck operations to e machanism helped raising the seat on both phases so that his eyes could be at the top of the visor binding. Simple instruments for blind flight were also added. The second member of the crew was the navigator, weapon officer and observer, located in the second seat further down in the cockpit and facing forward, exiting or entering though a sliding window on both sides. he acted also a auxiliary mechanic as his dashboard showed fuel consumption in an indicator gage on top of the center-section fuel tanks, located on the wings. For dropping bombs, he could removed the two seat’s floor hatch panels and access a ledge to the left of the torpedo/bomb suspended under the fuselage. The last member was the radio operator which doubled as rear gunner, seaying while facing rearwards, accessing his machine gun stored inside the fuselage but which could be erected after the rear canopy was moved back. Early radios modls though were of the low frequency and needed a long towed antenna.

Communication between crew members were done using still an old style speaking pipe, and oxygen equipment was purely optional even though the high altitude this model could achieve. This made it simpler and cheaoper as well, but also much lighter, something all designers in Japan tried to achieve. They all wore life jackets of a very inefficient design and hot furred aviator leather combis.

Design in detail

Comparison betwen the Nakajima Type 11 and 12.

General construction


Single-bay fuselage, with an all-metal stress skin, mostly welded and of duralumin. It was semi-monocoque with tubular sections. There was a release system for a towed antenna on the B5N1, but the B5N2 instead had a wire antenna stretched from one top of the cockpit to the top of the tail. Longerons as well as partial rear fuselage sections were skin-covered. It had relatively large wings suitable to carry a large payload, but causing drag and therefore reducing both speed and agility. Dimensions were reduced as weight leading to a very light design compared to the USN Devastator. The hope was to out-run opposition, so protection was absent. Fuel tanks were not self-sealing at first and there was no armor plating to protect the pilots’s heads.

The two-spar wing had a manual folding system and the right one folded first so that it layed below the left, one on top of the cockpit, supported by auxiliary struts. The slotted flaps were placed up to the wing folding hinges and ailerons with linen cover, were located outside. They had built-in fuel tanks behind the upper and lower wing lining, placed between the main and rear spars of the center section, attached with edges brackets. Trim tabs were provided on horizontal and vertical rudders.

The hydraulically retractable main undercarriage mounted under the wings had each leg fitted with an oil-damper type shock absorber reinforced by a forward bending strut. When retracted the wheels were turned 90° to fit inside the wings. The tail wheel was non-retractable and cast. The retractable landing hook was mounted ahead of it. It was sprung by a coil spring when landing to extent downards and retracted before taking off in its tensioned position.

The B5N was caracterized by its long glass cockpit, protecting a three-seat crew: The pilot, the navigator/bombardier/observer seated beind, and a radio-operator/gunner at the rear. Like with other IJN multi-seat aircraft, it was commanded by a senior ranking crew member, more often the observer, which directed the flight. This combination was important to deliver strikes in the middle of the pacific. Despite the lightness of its structure, the B5N was sturdy enough to make rough landings, equipped with a stable, large span landing gear, folding inwards. The wings had as straight section up to 1/3 of their lenght, then followed by an upwards section, with the folding cuts about 40% of the total lenght. A pair of small doors in the floor of the second crew member opened through the lower surface of the left wing root for visual aiming during bombing.

The B5N had a right-mounted pitot tube for flight data, an underwing mounted antenna, and main radio antenna placed at the rear, above the radio set. The radio operator seat was in fact a rotating stool, allowing him to turn back towards the tail to man the defensive machine gun. The navigator was seated more conventionally, and facing forward. The overall cockpit was not roomy however. Overall, the B5N looked right and very modern for its time, but its output was not sufficient to out-run fighters as expected, with a top speed of just 320 kph at best, most late 1930s Chinese fighters could catch it.

Engine & performances


The navigator/bombardier/observer was given a Type 90 bombsight, a long vertical tube, located in the front-left of his seat. He also had a Type 3 reflector compass, for precise navigation over the Pacific. It was mounted on top of the cockpit frame. He also had at its disposal a standard-issue radio set, Type 96 Mk3 for the B5N1 and Type 2 Mk3 on the B5N2. It was placed in front of the operator/rear gunner, behind the navigator/bombardier/observer’s seat.


Very early production Type 97 model 1 in 1938

The B5N1 carried a forward machine gun armament for strafing an possible attack in flight, two 7.7 Type 97 machine guns in the wings. But it was not the case for all. In fact many went just equipped with a defensive armament only, a single flexible-mounted 7.7 mm (.303 in) Type 92 machine gun.

The main use of the B5N was its Type 91 torpedo carried underbelly. It was mounted under racks were fixed eccentrically, to the right-bottom of the fuselage. They could be replaced for a model supporting a 800 kg bomb (Like the Type 99 No 80 armor-piercing bomb also used by the “Val” with devastating result, but in that case, dropped in level-bombing) or two 250 kg bombs (Type 98, No 25) or six smaller 60 kg bombs (Type 2 No 6). Replacing racks however was a two hours long process to complete, which cost the admiralty dearly at Midway…

Production & succession

Combat experience during the Second Sino-Japanese War revealed weaknesses in the original B5N1 design, notably the lack of protection for bth the crew and fuel tanks. The Navy however preferred to add more power to the model to out-run opposition rather than taking punishment, leading to the B5N2 equipped with the Sakae Model 11, 14-cyl. twin-row radial also used on the initial A6M fighter. Performance ended only marginally better, but it was produced anyway from 1939 at an increased rate until 1943, a long production run for a 1937 design.

Work on improving performances of the B5N1 continued so that in December 1939 already the B5N2 powered by a Nakajima Sakae two-row radial engine and revised cowl seemed a wnning formula, and other design changes included a modified antenna above the rear cockpit. Known at first in ordnance as the Type 97 Model 3 Naval Carrier-Based Attack Bomber, it became the Type 97 Model 12 in accordance with the new model designation system. In December 1941, it was already replacing the B5N1s onboard aicraft carriers, although both models took part in the Pearl Harbor attack.

Nakajima Aircraft Company produced alone 1,149, the production run ceasing in mid-1943 with the B5N2. The B5N was to be replaced by the B6N Tenzan “Jill” which first flew in March 1941, but development dragged on and it was only ready in August 1943, introduced and produced until 1945, so only available in numbers in 1944. More were produced, 1,268 in all but their battle records were certainly less brillant.

Itself was to be replaced by the Aichi B7A Ryusei “Grace” (Nakajima lost the competition to its rival). It first flew in May 1942 after a seemingly impossible spec of 1941 to replace both the B6N and D4Y, so having a universal torpedo/dive bomber for the new light carriers (with reduced air groups) potentially built by the IJN after 1943. However the Aichi B7A development proved complicated and it was only produced from late 1944, to 114 units only, most seized in Japan after the war has ended, and with practically no carrier left to carry them. The last variant B7A3, never built, was planned with a 1641 kW (2,200 hp) Mitsubishi MK9A engine, twice as powerful as the “kate”.

  • Type K: 1937 factory Prototype.
  • B5N1: First production model of 1938.
  • B5N1-K: 1944-45 conversion into advanced training aircraft.
  • B5N2: Improved main production version from 1939.

Detailed specs

Nakajima B5N2 (1939)

Crew: 3: Pilot, navigator/bomber, gunner/radio
Fuselage Lenght 10.3 m (33 ft 10 in)
Wingspan 15.5 m (50 ft 11 in)
Wing area 37.7 m2 (406 sq ft)
Height 3.7 m (12 ft 2 in)
Airfoil type NN-5 mod. (16%); tip: NN-9 mod. (8%)
Empty weight: 2,279 kg (5,024 lb)
Max takeoff weight: 4,100 kg (9,040 lb)
Propeller: 3-bladed metal propeller
Engine: Nakajima PE NK1B Sakae 11, 14-cyl. ACR 1,000 hp TO or 970 hp at 3,000 m
Top speed: 378 km/h (235 mph, 204 kn) at 3,600 m (11,811 ft)
Climb rate: 6,5 m/s (1,280 ft/min)
Range: 978 km (608 mi, 528 nmi) or 1,991 km (1,237 mi, 1,075 nmi) straight
Service ceiling: 8,260 m (27,100 ft)
Time to altitude: 3,000 m (9,843 ft) in 7 minutes 40 seconds
Power/mass: 0.196 kW/kg (0.119 hp/lb)
Wing loading 100.8 kg/m2 (20.6 lb/sq ft)
Armament 1-3x 7.7 mm (0.303 in) Type 97 MGs, 1 torpedo/800 kgs bomb, see notes

The B5N “Kate” in action

B5N2 over the Java sea, February 1942

On December 7, 1941, the western world reminded the “Never underestimate the enemy” motto first coined by Sun Tsu. The yet completely unknown or dismissed Nakajima B5N first appeared to Pearl Harbor an her rampage would go on for most of the Pacific War.

The B5N, codenamed “Kate” by ONI in 1941 was primarily deployed as a carrier-based aircraft, but later in the war as a land-based bomber. The B5N1 first saw action in the Second Sino-Japanese War, from 1938. There, default were recoignised but the IJN wanted more speed, not protection. These combat debut were as land-based aircraft, and in support of the Army operating in Hankow. In the autumn of 1940 under forced agreement with the Vichy government, French Indochina was dotted with bases operating B5N2s, used for bombing Chiang Kai-shek troops in southern China. The B5N2 introduced in 1939 became by far the largest production of the tyme, playing a major role at Pearl Harbor and all subsequent engagements of the IJN until the situation started to reverse.

A B5N takes off from IJN Shokaku for the Pearl Harbor attack

In November 1940 the Taranto pushed Minoru Genda, later recalled by Admiral Yamamoto to propose a similar surprise attack on Pearl Harbor. For this, the Type 97 was however to be armed with special torpedoes due to the local shallow waters. They were equipped with wooden tails, forcing them to stay close to the surface after launch. Armor-piercing bombs being in short supply and reeserved to the “Val”, B5N2s used as bombers were given 16-inch naval shells with welded stabilizers instead, becoming 800-kg bombs.

After training in the Gulf of South Kyushu, these B5Ns distribited among Kido Butai’s six aircraft carriers under orders of Admiral Nagumo gathered in Tankan Bay, Kuriles Islands and sailed from 28 November. In all, Genda had at its disposal some 353 aircraft, launched in two waves. They left the carriers in the monring early hours of December 7, B5N2 armed with bombs under command of Mitsuo Fuchida. 50 took part in the first wave, alongside 40 B5N1 with torpedoes led by Lieutenant Commander Shigeharu Murata. The attacked commenced at 7.49 AM. It was highly successful. A second wave later included 54 B5Ns fitted as bombers. It was all over at 8.30 and only five B5N2 were lost. Stats shown they had some 30% direct hits from torpedoes, 27% from bombers, the payoff of months of intensive training.

A B5N2 passes close to USS Noprthampton at the battle of Santa Cruz Islands.

In early 1942, Nagumo assaulted the Dutch East Indies, and this costed the British among others the loss of the Dorsetshire, Cornwall and Hermes, by B5N2s and D3A2s (Type 97 and Type 99). B5N2s also sank the aircraft carrier USS Lexington at Coral Sea, and USS Hornet at Santa Cruz Islands. B5Ns also nearly sank USS Yorktown at Midway, finished off by I-168 later.

B5N2s crews were trained in coordinated attacks on enemy carriers with the Aichi D3A dive bombers. Dive bombers weere the first to act, trying to suppress the ship’s AA or daw it to them, allowing the slow flying “kates” to make their torpedo run to target, very low-flying. At the Battle of Eastern Solomons, the IJN initially sent only dive bombers to enable a later torpedo strike but this tactic proved unsuccessful: They did not launch until the battle was over.

Pearl Harbor: Akagi’s B5N crews

The IJN had operated with almost no effective countermeasures and gambled all on the first major air strike. This was their undoing at Midway. Later Ryujo and Junyo were to strike at the Aleutian Islands, Akagi, Kaga, Soryu and and Hiryu meanwhile hitting Midway and on 5/7/42, two waves of B5N2 bombers hit Midway Island. However that day they lost 50% of their trained crews and never recovered from this. Eastern Solomons, Santa Cruz, and Guadalcanal drained aircraft and crews, which the remainder took refuge in Truk. Carrier battles were absent of 1943, B5N2s were used from land bases: Buin and Kolombangara (Solomons) for punctual strikes, made difficult by the increaing numbers of ships and excellent AA. Also in 1943 with the new Essex-class carriers came the Hellcat, which had no issue downing the slow B5N2 in droves.

B5N2 taking off from IJN Zuikaku at Coral Sea, May 1942

By 1944, the Corsair also became the B5N nightmare, but the latter became increasingly rare. The “Jill” started to replace them on various bases and they were gradually retired to the home islands. The Marianas and the Battle of the Philippines on 19 June signed the loss of 1,600 aircraft and 3 aircraft carriers and many B5Ns. However in October 1944 the first kamikaze attacks started and the battle in Leyte Gulf, in which mpore and more battle-worn “Kates” flew with inexperienced pilots as Kamikaze. Some were still around in this guise at Iwo Jima and Okinawa. The last took hoff from Kyushu in the sumer of 1945

General Assessment

B5N2 in Rabaul

B5N Kate on Kataoka Airfield, Shumshu Island

The trio, A6M2 (“Zero”), D3A1 (“Val”) and B5N2 (“Kate”) paralleled the USN F4F-3 Wildcat, SBD-3 Dauntless and TBD-1 Devastator and all had a performance advantage but perhaps for the Dauntless. The British Fleet Air Arm models, after years of peacetime neglect, were hopelessly behind: The Fulmar, Skua and Swordfish were just not fit to survive in the Pacific. When in 1943 this early trio changed for the new combination F6F Hellcat, SB2C Helldiver and TBF Avenger, the “Zero” was never replaced, and the B5N2 stayed in frontline until the summer of 1944.

Frantic work to replace the B5N2 eventually culminated in the B6N1 Tenzan (“Heaven’s Peak”) which was prepared for trials in March 1942, powered by a 1870 hp oversized Nakajima Mamori engine, but plagues with vibration problems forcing replacement for a Mitsubishi Kinsei, as the B6N2 (“Jill”) and absent of the devastating Marianas battle of June 1944. In the Philippine Sea, carrier-based aircraft like the “Jill” mostly were used only from land bases.

The remaining B5N2s received an anti-ship radar to stay relevant, its with antennas along the sides of the fuselage enabling anti-submarine patrols in all weather conditions or night. These pilots expertly flew their machine, forced by the primitive detection system, to just 9-12 meters above the surface. They carried up to 283.5-kg bombs with delayed fuses, acting like depht charges and exploding at a set depth. In 1945, the last B5N2s still serviceable were still used to tow gliders and targets in the home islands.


A B5N replica as of today, made from an AT-6 Texan, heavily modified.

Japanese Aircraft of the Pacific War ” /Rene J Francillion.
“Japan Warplanes of World War II” /Oleg Doroshkevich
Angelucci, Enzo and Paolo Matricardi. World Aircraft: World War II, Volume II (Sampson Low Guides). Maidenhead
Chambers, Mark A. (2017). Nakajima B5N ‘Kate’ and B6N ‘Jill’ Units. Vol. Combat Aircraft #119. Osprey Publishing.
Francillon, René J. Japanese Aircraft of the Pacific War. London: Putnam & Company Ltd., 1970
Francillon, René J. Japanese Bombers of World War Two, Volume One. Windsor, Berkshire, UK: Hylton Lacy Publishers Ltd.
Lundstrom, John B. (2005a). The First Team: Pacific Naval Air Combat from Pearl Harbor to Midway (New ed.) NIP.
Lundstrom, John B. (2005b). First Team and the Guadalcanal Campaign: Naval Fighter Combat from August to November 1942
Mikesh, Robert C. (2004). Japanese Aircraft Equipment: 1940-1945. Schiffer Publishing.
Parshall, Jonathan and Anthony Tully. Shattered Sword: The Untold Story of the Battle of Midway. Potomac Books
Tagaya, Osamu (2003). Imperial Japanese Naval Aviator 1937-45. Osprey Publishing.
Tagaya, Osamu (2011). Aichi 99 Kanbaku ‘Val’ Units of World War 2. Botley, UK: Osprey Publications.

List of airfoil designations
On The Pacific War Online Encyclopedia

Model kits of the B5Ns on scalemates

Color trivia: Early B5Ns came from the factory in peacetime left in an overall silver finish. In wartime, they were painted in dark olive green as a standard, which was sometimes retr-applied on the field with surprising results and strange camouflage patterns. In other cases, the paint was weathered and partly disappeared, creating patterns of dark, mate and shiny silver in between. Add to this, the usual markings in Kenjis and arabic numbers on the tail, as unit symbols, and identification bands completed a sometimes vivid livery, always a subject appreciated by modellers.

Nakajima B5N1 12th Kokutaio, China 1938-39, one of the first operator. Denomination Donation Slogan Hokoku 268 “Tokyo Kikai-Go”

B5N1, 14th Kokutai, Sanzai Dao, with its Chinese camouflage, Southern China 1939

B5N1 Model 11 14th Kokutai China 1938-39

B5N1 at the Yokosuka Naval Air Base for training, 1940

B5N1 at the Konoe Naval Air Corps training unit, 1941

Nakajima B5N-1 from the 4th Kokutai, IJN Ryujo, 1941

B5N-1 IJN Zuiho, February 1942

B5N-2, IJN Shokaku, December 1941, Pearl Harbor Attack

B5N-2, IJN Zuiho, Battle of Santa Cruz, October 1942

B5N2 IJN Soryu Central Pacific Dec. 1941

B5N2 1st Koku Kantai, IJN Akagi, Pearl Harbor, 7 Dec. 1941

B5N2 IJ Zuikaku Indian Ocean Raid 1942

B5N2 Lt. J. Tomonaga IJ Hiryu Central Pacific June 1942

B5N 2 on Saipan, June 1944

BH2 in flight – Green coll.

Type 55 bomb sight and torpedo release system

A Formation of B5N-1 from IJN Akagi in 1941

Nakajima B5N2 “Kate” carrying 250 kg (550 lb) bomb.

movie extract, “Hawai Mare oki kaisen (The War at Sea from Hawaii to Malay)” (1942).

B5N in flight

B5Ns over the Java Sea February 1942

Captured B5N with US markings, TAIC

Type 97 in flight

B5N1 aboard IJN Akagi with a dummy torpedo

B5N in flight

B5N2 in flight

B5N2 over Hickam field, Pearl Harbor

B5N1 from IJN Soryu in 1939

Type 97 from IJN Ryujo flying with mount Fuji behind

Surviving “Kate” in reconstruction at PHAM

Colorized photo, B5N and destroyer, South Java Sea. 1942

Mitsubishi F1M “Pete”

Mitsubishi F1M “Pete” (1936)

Imperial Japanese Navy, 944 built

The last IJN Biplane

Genesis for this model started in 1935 when first planned to succeed the Nakajima E8N as main catapult-launched navy spotter, mostly based on cruisers (The E13N was for battleships and succeed the E7K). The E8N (assigned the identifier “Dave” by US Intel) was a sturdy, reliable model, but slow and underpowered. Coming from the 1932 7-Shi specification, later 8-shi in 1933 it first flew in 1934 and was deployed from late 1935 and early 1936 too all capital ships and 16 cruisers of the IJN, plus five seaplane tenders.

As customary as soon it was introduced a new specification planned its successor, was made known to three manufacturers in 1934, Mitsubishi, Aichi and Kawanishi.

F1M predecessor, the E8N

Design development (1936-40)

In 1934, the specs called for still a short-ranged reconnaissance and observation model to be catapult-launched, and only with improved performances, now allowed by more powerful engines. Mitsubishi’s answered with the Ka-17, which was tested in 1935 and first flew in June 1936 after revisions of the specifications. It was proved superior to its competitors from Aichi and Kawanishi and thus, earned the contract. The F1M1 performed better than the Aichi but was plagued by poor stability while swimming and flying.


It was thus redesigned to solve these issues, and notably the wings were redesigned this time with a straight tapered leading edge, as well as trailing edges, plus they were rigged with a greater dihedral. Also to really nail stability, the vertical fin and rudder were much enlarged. Its floats were also enlarged to increase buoyancy and stability when at sea. Also, the Mitsubishi Hikari engine was replaced by a 652 kilowatts (875 hp) Mitsubishi Zuisei 14-cyl. radial engine, with a redesigned cowling which gave it better forward visibility. The final fuselage was smooth and aerodunamic.

Tested again later in 1936, the pilot resported its handling characteristics were greatly improved. The Navy appreciated the effort made by Mitsbushi and greenlighter production, as the “Navy Type 0 observation seaplane Model 11”, with the short designation F1M2. The F1M1 was only produced to four prototypes. 940 aircraft were built in total, 342 by Mitsubishi and 598 by Sasebo Arsenal, plus the 21st Arsenal. Production started in early 1941, after Mitsubishi had to create an entirely new production chain for it, already busy with other models such as the A5M.


The Ka-17 was a small all-metal biplane, powered by a single Nakajima Hikari 1 radial engine. The latter was rated for 610 kilowatts (820 hp) and basically was the same which propelled its direct competitor, the Aichi F1A. This was still a biplane, but with elliptical wings and many wind tunnels studies and design care to reduce drag. Bracing was reduced to the minimum and interplane struts much simplified: It had “n” struts between the central upper wing and fuselage, and simple pillar-like profiled struts to maintained both upper and low wings.

Also the large central float was attached to the belly by a single, profiled large pillar, followed by a rear “V” strut attachment. Both fmaller underwings floats were attached by “N” type struts. Bracing was only provided in a “X” tranverse fashion between the wings. Thanks to its Mitsubishi MK2C Zuisei 13, 14-cylinder air-cooled radial piston engine rated for 652 kW (875 hp) (ar take-off), or 600 kW (800 hp) at 3,500 m at 11,500 ft mated to a 3-bladed variable-pitch metal propeller, the The F1M2 had a maximum speed of 368 km/h (230 mph). Its max range was up to 1,072 km (670 mi) light (no payload). it was also armed with three 7.7 mm (.303 in) machine guns: Two fixed forward-firing on the nose, and a single flexible mounted rear-firing one for the observer. The underwings had racks for two 60 kg (132 lb) bombs. So this made for a versatile platform.

A single variant was manufactured, the F1M2-K two-seat training version.

Detailed specs

Mitsubishi F1M2

Crew: 2: Pilot, radio/observer/gunner
Fuselage Lenght 9.5 m (31 ft 2 in)
Wingspan 11 m (36 ft 1 in)
Wing area 29.5 m2 (318 sq ft)
Height 4 m (13 ft 1 in)
Empty weight: 1,928 kg (4,251 lb)
Max takeoff weight: 2,856 kg (5,622 lb)
Propeller: 3-bladed metal propeller
Engine: Mitsubishi MK2C Zuisei 13 14-cyl. 652 kW (875 hp) TO/600 kW (800 hp) at 3,500 m
Top speed: 370 km/h (230 mph, 200 kn) at 3,440 m (11,290 ft)
Climb rate: 5,000 m (16,000 ft) in 9 min 36 sec
Range: 740 km (460 mi, 400 nmi)
Service ceiling: 9,440 m (30,970 ft)
Wing Loading: 86.3 kg/m2 (17.7 lb/sq ft)
Power/mass: 0.156 hp/lb (0.256 kW/kg)
Armament: MGs 2 × fixed fwd 7.7 mm (.303 in) Type 97, 1× flexible rear Type 92 LMG
Armament: Bombs 2× 60 kg (132 lb) bombs (or single 250 kg bomb for suicidal missions)

The F1M2 in action

Introduced a bit late as a biplane (almost six years after its first flight !) this model was the last biplane in service with the IJN. The formula had its advantages through: Although it limited top speed and high-G evolutions, the structure proved sturdy enough to practice dive bombing if needed. The reduced span and high lift was also an advantage for onboard storage, handling and lift when catapultes. The engine proved powerful enough to give extra agility to this model, and surprisingly enough, the “Pete” was used as fighter when the occasion arose, against allied bombers mostly.

The F1M was deployed in the fleet for gunnery spotting alongside the Nakajima E13A. In 1940 the Type 0 Model 11 was aboard eight battleships, including the Nagato and Yamato, nine cruisers and six aircraft tenders, plus many shore based units. Although the F1M’s comparatively low speed made it vulnerable to the best Allied fighters, it could successfully be used as a front line aircraft in secondary theatres (of which there were many in the Pacific).

The F1M even sometimes acted as a fighter in these isolated islands, or was seen acting as dive bomber in support of amphibious landings early on in 1942, and also a convoy escort aircraft, although limited somewhat by its short range, making ASW coastal patrols. Its main strength here was its manoeuvrability, so it was not eve, considered a threat by second-line Allied aircraft, which underestimated its capabilities.

The “Pete” performed soon a large veriety of mission when deployed over China: Convoy escort, bomber, anti-submarine and maritime patrol, but also rescue, transport, and anti-shipping strike: In one occasion, a “pete” equipped with bombs made a hit and sank the Motor Torpedo Boat PT-34, on 9 April 1942. Later in the war, it was also used as area-defense fighter, seeing impromptu fights with US planes in the Aleutians, notably the F4F Wildcat.

The F1M also saw plenty of action in and around the Solomons and played its part in all subsequent engagements, notably in New Guinea, used as point-defense fighter against Australian and US bombers and fighters coming from nearby Australia. The F1M was also the last IJN observation model to see large production and widespread use. Although its replacement was planned, as the Kawanishi E15K Shiun “Norm”, it never arrived in service in time (only 15 were delivered). In 1945, Indonesians captured a few F1M2s, which were used to fight the Dutch all along the gruelling Indonesian National Revolution. The Royal Thai Navy also operated some in 1944.


Francillon, R.J. Japanese Aircraft of the Pacific War. Putnam, 1970.
Green, William. War Planes of the Second World War, Volume Six: Floatplanes. Macdonald & Co.
Wieliczko, Leszek A. (2017). “Mitsubishi F1M (Pete)”. Technika Wojskowa Historia

On pacificeagles.net
On historyofwar.org
On daveswarbirds.com

Fujumi 1/72 1997.
General quety on scalemates, many kits

F1M1 in grey livery, 1941

F1M1 in green livery, 1942

F1M2, unknown unit

F1M2 IJN Haruna, Bat. Guadalcanal, November 1942

F1M2 in June 1945, used by a Kamikaze unit.

Two damaged Mitsubishi F1M2 (Allied code name “Pete”) observation seaplanes beached at the former Japanese seaplane base at Rekata Bay on the northern end of Santa Isabel island in March 1944. The man standing on the float of the nearer aircraft is flight lieutenant J. Beattie, Royal New Zealand Air Force.

Captured parts of an Indonesian “Pete”: Corporal Ralph Hayden and Leading Aircraftman Harry Pearce of No. 80 Squadron RAF amongst parts of a Mitsubishi F1M, bearing Indonesian markings, at an airfield and seaplane base in Surabaya (Soerabaja), Java, January 1946. In the background are Kawanishi N1K floatplanes.

Model kit

F1M1 over Rabaul

Planned replacement: The Kawanishi E15K Shiun (1942)

Aichi D3A “Val” (1936)

Aichi D3A (1938)

Imperial Japanese Navy, 1,495 built

The D3A2 “Val” main IJN Dive Bomber in 1941

The “Val” as it was referred in the USN, was the main Imperial Japanese Dive Bomber of WW2, until replaced gradually from 1942 onwards by the Yokosuka D4Y Suisei, far more modern by all standards and benefiting from a higher production. But it was really the dreaded “Val” that made all the heavy lifting for the IJN in the crucial first year of the war with the US, until December 1942, with ace pilots and results: They sank single-handedly 11 destroyers, two heavy cruisers, one aircraft carrier and several auxiliaries, while assisting in many others, notably five fleet aircraft carriers.

Superb colorization by irootoko Jr. of the D3A taking off from Akagi during the Indian Ocean raid.

The Aichi D3A was innovative as being a cantilever monoplane, unlike the D1A/D2A “Susie” it replaced. It would be adopted in 1939, battle tested in China, and then produced three times more. The D3A was also the last fixed undercarriage model of the IJN, although it had a fully enclosed cockpit, and folding wingtips. Rugged, not very fast but surprinsingly agile, the “Val” was also accurate enough for the task intended, and performed well into the Kido Butai (1st air fleet) from all carrier decks since Pearl Harbor to the fall of Guadalcanal. It was delivered in two main variants, the D3A1 and D3A2 which soldiered on into well late 1944 in land-based units and for training in 1945.

Development: A replacement for the D2Y

The IJN wanted in mid-1936 a new dive bomber to replace the Aichi D2Y which just entered production. Looking at what other countries were working on, the days of the biplane seemed off, and the admiralty expressed the desire for a cantilever monoplane. The 11-Shi specification was specified to Aichi, Nakajima, and Mitsubishi, which all worked on, and submitted their own designs, and asked in a second phase for two prototypes each.

German Heinkel HE-70 “Blitz”, an inspiration for the wings design.

The Aichi design team worked on low-mounted elliptical wings, inspired by the Heinkel He 70 Blitz, then just purchased for evaluation. The elliptical shape was at the start a mathematical theory destined to procure the best compromise of all shapes, providing lift, agility and maintaining drag low enough for agility. This type of wing was also prototyped on Mitchell’s fighter at the same time.

The very first prototype, on paper, was to be powered by the 529 kW (709 hp) Nakajima Hikari 1. It was feeble for an engine, and flew slow enough not to worry about the drag caused by its fixed landing gear, an ideal solution to land on aicraft carriers. It was not seen as a serious issue as top speed was not a priority. Simplicity also imposed a trusted nine-cylinder radial engine. They dropped the idea of a liquid-cooled inline engine, as none was provided at the time in Japan.

The first built of the two prototype was complete in December 1937. It flew a month later in 1938, and despite poor test results, was designated by the Navy as as D3A1 (Factory wise it was the Type Navy Dive Bomber, and did not received a more “bankable” surname as later models). Initial tests showed the Type 99 was clearly underpowered, but also suffered from directional instability in wide turns while tighter turns made it to snap roll. Also when diving, its brakes vibrated a lot when extended, so much so it was feared they would shear off and damage the plane in flight. Still at the time, the Navy asked for a design speed of 200 knots (370 km/h), but made a revision to take in account faster western fighters depliyed in China, and asked for a diving speed of 240 knots (440 km/h).

The Loosing Competitor, Nakajima D3N1

The second prototype was extensively modified to address these demands and solve the flight issues:

-A new engine was adopted, the 626 kW (839 hp) Mitsubishi Kinsei 3
-There was a redesigned cowling
-The Vertical tail was enlarged and reshaped for better directional instability.
-Wings had now a larger span with leading edges hawing wash-out
-Strengthened dive brakes.
This fixed all but one problem as the prototype made its flight debut: The directional instability was still there, but still, the pckage was judged by the Navy Commission superior at the time to its competitor the Nakajima D3N1.

Second Type 99 protoype in 1939.

In December 1939, the Navy ordered the new model as the “Navy Type 99 Carrier Bomber Model 11” (“kanjō bakugekiki”). Production was adapted however, and presented slightly larger wing span, improved dive brakes, and increased power (Now the 746 kW (1,000 hp) Kinsei 43 and later 798 kW (1,070 hp) Kinsei 44, plus redesigned cowling. A long dorsal fin-strake, starting midway down the rear fuselage, caracteristic of the D3A, cured the instability problem. In fact it made, combined with the more powerful engine and elliptic wings, the D3A extremely manoeuvrable, so much so that new mission were invisioned.

Final Design

D3A1 From IJN Akagi over China, 1940

The fuselage was single-bay, of ovale section with framing and stress aluminium skin. The cockpit and its two sliding canopies was relatively short, just intended for two seats, the pilot forward and the observer/navigator/gunner aft, on a revolving seat. As seen above, the wings were ellipitic to increase manoeuvrability, as were the vertical tail and tailwings. As the britsh would have said, it “looked right” tat first glance, and indeed flight right, without any vice. Without its fixed undercarriage creating drag and a more powerful engine, plus some armor and self-sealing tanks, it could have been an excellent fight-bomber.


kinsei 54 of a D3A3 in maintenance on an island, 1944

The The Mitsubishi Kinsei (金星, or “Venus”) was a 14-cylinder, air-cooled, twin-row radial aircraft engine. It was developed by Mitsubishi in 1934 for the IJN, wit factory designation A8 when experimental and in service, MK8 “Kinsei” (Navy designation). In 1941, the reputation of this engine was such it was also adopted by the Army as Ha-112 or 1,300hp Army Type 1 and Ha-33 in May 1943, equipping the Yokosuka D4Y3-D4Y4 and Kawasaki Ki-100 in its late version.

Kinsei 41 saw increase in compression ratio from 6.0:1 to 6.6:1 with a larger supercharger and it was introduced from 1936 produced until 1945. The D3A1 had the Kinsei 43, delivering 1,000 hp (750 kW) at 2400 rpm at sea level
or 990 hp (740 kW) at 2400 rpm at 2,800 m (9,200 ft), and later the Kinsei 44 which developed 1,070 hp (800 kW) at sea level and 1,080 hp (810 kW) at 2,000 m (6,600 ft).

The D3A2 jumped on the next iteration, in the Kinsei 50 serie. The latter had a final compression ratio of 7.0:1 and Indirect fuel injection plus a larger two-speed supercharger. The D3A2 Kinsei 54 improved output to 1,200 hp (890 kW) at 2500 rpm at 3,000 m (9,800 ft) and 1,100 hp (820 kW) at 2500 rpm at 6,200 m (20,300 ft) thanks to previous improvements, redesigned cylinder head, water injection and then higher pressure oil pump.


Vals from IJN Shokaku, 1942 (AWM)

The only issue with the “Val” was its relatively weak payload, especially compared to the B5N “Kate” which carried a bomb almost double the weight. The D3A1 and D3A2 both carried:
-Two fixed forward-firing 7.7 mm (0.303 in) Type 97 machine guns in the wings
-One flexible 7.7 mm (.303 in) Type 92 machine gun rear of the cockpit
-Normal bomb load: 250 kg bomb (Type 99 No 25 semi-AP or Type 98 No 25 land bomb) under the fuselage. To avoid hitting the propeller, it was swung under it and released by a trapeze.
-Two additional 60 kg bombs (Type 99 No 6 semi-AP or Type 2 No 6 land bomb) were carried underwings racks located outboard of the dive brakes.


The pilot had a Type 95 telescopic gunsight and later Type 99 used for aiming the bomb when diving. The observer/navigator had a Type 97 Mk1 drift sight located in the front-left of his seat. A drift meter was also mounted on the floor, front-right of his seat. Between him and the pilot was located the lain Type 96 Mk2 radio set, which on top of it a Type 3 reflector compass for navigation.


Production: D3A1

In total, some 479 D3A1 were delovered by Aichi Kokuki KK, less than the D1A/D3A total production, but it filled the needs of the IJN and all its aicraft carriers when introduced in 1940. Due to the rapid progress of aviaton performances, in 1942, this model was no longer relevant and already engineers at Aichi worked out a much improved model. One of te improvements brought to the late D3A1 was a propeller spinner, which became standard with the next iteration.

Production: D3A2

In June 1942, these efforts succeeded by bringing an all improved version of the D3A1, now powered by the 969 kW (1,299 hp) Kinsei 54 engine. This, and many other modifications, like the engine cowl, srength, tail, and fuselage glasshouse tested in a modern wind tunnel, brought even more performances to what became the D3A2 (Aichi Model 12, Navy Model 22). Range was reduced by the larger engine, so engineers found a way to cram into the fuselage additional fuel tanks, bringing the total to 900 L (240 US gal) so that it could effectively roamed free all along the Solomon Islands.

The Navy Model 22 started to replace the Model 11 (D3A1) in front-line units in autumn 1942, those retired being sent to training units or land-based units. However already by late 1943, they were replaced in turn by the Yokosuka D4Y Suisei (“Judy”).

Overall, Aichi Kokuki K.K., at Funakata, Nagoya produced two 11-Shi prototypes (1937-38), six D3A1 Service trials aircraft (1939), 470 D3A1 Model 11 production (Dec 1939-Aug 1942) a single D3A2 Model 12 prototype (June 1942) and 815 D3A2 Model 22 production (Aug 1942-June 1944) for 1,294 total and Showa Hikoki Kogyo K.K. in Tokyo added to this 201 D3A2 Model 22 production (Dec 1942-Aug 1945).

The forgotten “Val”: D3Y Myojo

D3Y Myojo
D3Y Myojo in 1945.

Aichi was conscious that mass production used lots of valuable materials, and in 1943, started a study to replace the D3A1 used for training by an equivalent using non-strategic materials, and in this case, wood. Therefore, The D3Y was designed as a two-seat bomber trainer, based on the successful Aichi D3A2, still with a fixed tailwheel undercarriage.

Aichi planned to allow construction by unskilled workers and the design was much simplified: Straight tapered wings were used while the fuselage was lengthened to improve stability. Only two prototypes were built in 1944, proving heavier than expected for their Mitsubishi Kinsei 54 radial engine, same as the D3A2. After much redesign to save weight, it was approved for production and in 1945, three producton models only were delivered, designated “Navy Type 99 Bomber Trainer, Myojo Model 22”. Myojo meant “venus”. Its characteristics are not well known, but it could carry at least a dummy bomb, likely to have been replaced in case by a real one:

It’s armament indeed as designed comprised two 20 mm (0.787 in) Type 99 Mark 1 machine guns in the engine cowling and a single 800 kgs (1800 ib) bomb. There was no provision of a rear gunner, just a pilot. Performances were rarther similar to the regular D3A2, 470 km/h (290 mph, 250 kn) at 5,000 m (16,000 ft) for top speed, 296 km/h cruise speed, and a range of 1,472 km (915 mi, 795 nmi). Aichi also worked on an improved version called the D5Y1 Myojo Kai (Navy Special Attacker Myojo Kai), also known as the experimental D3Y2-K Myojo, a derivative used for Kamikaze missions. To improve its performances in the air, the undrrcarriage was jettisonable. The prototype was seized incomplete in August 1945.

Detailed specs

D3A1 Specs

Crew: 2: Pilot, observer/radio
Fuselage Lenght 10.195 m (33 ft 5 in)
Wingspan 14.365 m (47 ft 2 in)
Wing area 34.9 m2 (376 sq ft)
Height 3.84 m (12 ft 7 in)
Empty weight: 2,408 kg (5,309 lb)
Max takeoff weight: 3,650 kg (8,050 lb)
Propeller: 3-bladed metal constant speed propeller
Engine: 1,070 hp (800 kW) Mitsubishi Kinsei 44 – D3A1 Model 11 (late production)
Top speed: 387 km/h (240 mph; 209 kn) at 3,000 m (9,800 ft)
Climb rate: 3,000 m (9,800 ft) in 6 minutes 27 seconds
Endurance: 1,472 km (915 mi)
Service ceiling: 9,300 m (30,500 ft)
Wing Loading: 104.6 kg/m2 (21.4 lb/sq ft)
Power/mass: 4.9 kg/kW (8 lb/hp)
Armament 2x forward-firing 7.7 mm Type 97, one Type 92 rear flexible moun, 1x 250 kg (550 lb) fuselage bomb, 2x 60 kg (130 lb) underwings
Other payloads 2x 160 l (42.27 US gal; 35.20 imp gal) drop-tanks

D3A2 M22 Specs

Empty weight: 2,570 kg (5,666 lb)
Max takeoff weight: 3,800 kg (8,378 lb)
Propeller: 3-bladed metal propeller
Engine: Mitsubishi Kinsei 54 14-cyl. AC RPE 970 kW (1,300 hp) take-off, 1,200 hp (890 kW)/3,000 m, 1,100 hp (820 kW)/6,200 m
Top speed: 430 km/h (270 mph, 230 kn) at 6,200 m (20,300 ft)
Climb rate: 3,000 m (9,800 ft) in 5 minutes 48 seconds
Endurance: 1,352 km (840 mi, 730 nmi)
Service ceiling: 9,800 m (32,200 ft)
Wing Loading: 108.9 kg/m2 (22.3 lb/sq ft)
Power/mass: 3.9 kg/kW (6.4 lb/hp)

The D3A in action

Tactical use of the “Val”

D3A taking of from Akagi for the Indian Ocean Raid

The D3A operated as a carrier-based dve bomber, able to operate decisive strikes on the often lightly protected vertical decks of USN major ships, capital ships and aicraft carriers, which had the largest surface. By doctrine, IJN pilots avoided to targets light vessels like destroyers, being a narrow, nimble and very agile ships. Cruisers were manageable using the “follow the lead” tactic by a more experience dive bomber crew. Individual D3As were commanded by the senior ranking crew member aboard. It happened to be the observer in some cases, not the pilot, unlike in the USN where the pilot was almost always commander. Both Lieutenant Takehiko Chihaya at Pearl Harbor and Lieutenant Keiichi Arima in the Solomon Islands campaign were observers/commanders.

On the tactical organization size, the First air fleet (Kido Butai) took the best advantage of these airborne combined arms tactics by using two divisions, with two carriers each, carrying divided strike forces, one division having mostly dive bombers and the other torpedo planes, while the fighter escort and CAP was contributed to all four carriers.

The D3A approached in high altitude to facilitate long range spotting by the chief observer of the squadron, the one aboard the division (Chutai, 3×3 planes) leader, although a spotting could be achievd by any “Val” in the formation, in groups of three, two “Shotai” on the wings, one on front, which was also the Chutai leader. When spotted, the targeted ship was approached from 17-22 km away (10-14 miles), ideally on its front. An attack was coming from 9,800 feets, down to 3,000 feets (3000 down to 900 m) according to the manual, the division splitting into three Shotai (sections) of three planes each to choose their own path without interference.

All three started a 20% approach, going into three direction to approach the ship on various angles, to avoid the risk of the ship avoiding the attack, before starting their final dive in a steep to almost vertical (in general in a 55-60° angle) started at least at 4900 feets (1,500 m). The pilot uses its bomb aiming forward a separate device using its own set of graduations from the main targeting sight, which could be setup via a rotating nob inside the cockpit.

D3A preparing to take off for the Pearl Harbor attack

Once the bomb dropped, the “Val” started its resource at around 2000 ft (600 m) to recover t around 160 feets (50 m), basically just above the enemy vessels, to the point of having its fixed undercarriage touching or hitting water in other cases. It was likely the plane would tumble over and break apart when it happened. This was seen sometimes with some zealous veteran pilots. Rookie “Val” pilots in 1943 tended to dive, and correspondingly take their resource far earlier, leading to growing inacurracy.

This standard tactic was often coupled in conjunction of two other squadrons: B5N “Kate” in bombing configuration, dropping their payload from well above target, and the same in torpedo-carrying configuration, if when going well combined, made their torpedo attack at the same time. The goal was for the latter to start a bit earlier in order to force the target ship an evasive turn hard to port/starboard, on which the “Val” squadron leader would calculate a trajectory ideal to meet the ship making its manoeuver.

The same was true the other way, depending on the circumstances (mainly the timing of squadrons arrival): “Vals” could dive first, and when discovered, drive AA fire to them, allowing “Kates” to operate their dangerous torpedo run where the ship was evading, just over the waves. Both USN and Japanese air crews arrived in training and simulations to the same conclusions about the best way to “corner” an enemy vessel. The strenght of USN AA was also a factor for Japanese air crews in their decision of operate immediately rather than waiting to take a better position during the pacific war. It should be added that “Zeros”, when not deadling with the enemy CAP, were used to strafe enemy vessels and targert their AA crews in particular, helping the work of torpedo-bombers.

The “Val” limited speed was comparable to its arch-rival the Dauntless, but it was criticized for its “light” payload, a single 250 kgs (550 Ibs) bomb, versus the latter which caried a much more potent 454 kgs bomb (1000 ibs). Almost double. Damage result was in relations, despite the use of timing fuse and AP cap allowing the Japanese bombs to penetrate the target’s decks before exploding, as shown by the fate of USS Arizona at Pearl. B5N Kates could carry a much larger 800 kgs (1760 Ibs), but it was only used in high altitude bombing and thus, less accurate. Nonetheless, those used at Pearl Harbor were modified, fitting AP shell cones into bomb bodies to ensure armo-piercing capabilities.

The “Val” carried two types, the Type 99 N°25 AP (armor-piercing) before Pearl Harbor and the Type 99 N°25 HE (High explosive) detonating on impact. The first could be used in early attacks, for example by the leader of each “Shutai”, exploding on AA gun mounts and blinding AA crews, clearing the way for the next two carrying an AP bomb. This was the tactic adopted at Pearl Harbor, repeated later in several battles like against USS Yorktown at Midway. In that case however, the dive bombers attacked from the rear.

Overall, given their tally, the “Vals” small bomb did its job well enough in many cases. Only the lack of training later in the war limited their success

First combat operations (1939-41)

The D3A1 first saw combat operation in November 1939, even before its official acceptance as the Navy Type 99 dive bomber. Nakajima indeed sent several early D3As to the 14th Air group, based on Hainan island and flying over the Haikou area of South China.

These formed a small “shutai” commanded by Lieutenant Sadamu Takahashi, in support of the Imperial Japanese Army. It took part in the battle of Nanning, and multiplied raids over the supply lines coming from French Indochina. After the fall of Nanning, they stayed operational there until 1940. By May 1940, the 12th Air Group gained the first production D3A1 dive bombers. They took part in the capture of Yichang and started anti-shipping patrols over the Yangtze river, to cut Chinese supplies from Chongqing. In September 1940, D3A1 from the 12th Kokutai started operations against Chongqing, by then the Chinese capital. The 14th Kokotai had the occasion to us its D3A1s in Indochina by the autumn of 1940, over (and later from) Hanoi, launching air raids over Kunming and Burma Road.

This was land-based missions, but in parallel, the D3A1 commenced carrier qualification trials: IJN Akagi and Kaga received theirs in 1940, making their combat debut from land bases in China.

Early Pacific operations (1942-43)

At Pearl Harbor, the D3A1 took a curcal part to the success of the two raids over the Hawaiian Pacific fleet stronghold, and could be credited notably with the destruction of several of the battleships present, but none single-handedly. The first 10 months of the war saw them exytremely active and during the Indian Ocean raid in April 1942 they reached their greatest tally, scoring over 80% hits and sinking two heavy cruisers and an aircraft carrier.

D3A1 dive bombers generally used semi-AP bombs and from 5 April 1942, Colombo, Ceylon was attacked by half the “Vals” active in the raid, while the other half was kept in reserve in case RN ships were reported. Later the Japanese command ordered a second strike against Colombo and the reserve D3As were rearmed with classic land bombs. In between, British heavy cruisers were spotted and the D3A with land bombs took part in the attack, unintentionally proving very effective: Their blast “cleaned up” the cruiser’s decks, nullifying anti-aircraft defense and allowing a pintpoint accuracy by the next D3A equuipped with semi-AP bombs. That accidental success led to modify the doctrine having in each Chutai, the one Shotai in the lead equipped with land bombs. This was the method use to sink HMS Hermes, and it became permanent.

1942 Netherlands, New Guinea and Solomons operations saw the better D3A2 took a grater part in operations, significantly contributing to sinking USS Lexington at the Battle of the Coral Sea, Yorktown at the Battle of Midway and USS Hornet at the Battle of the Santa Cruz Islands.

In addition, USS Enterprise was badly damaged at the Battle of the Eastern Solomons and at Santa Cruz, each time due to D3A hits. None prove fatal anyway. D3A1 in particular, superseded by the new D3A2 were often land-based, which came in handy during the Solomon Islands campaign, and the battle of Guadalcanal: Operation I-Go, Operation SE and Operation RO. In New Guinea they participated in the Battle of Milne Bay and Battle of Buna–Gona. During these operations, the veterans of the 2nd/582nd Air Group distinguishe themselves particularly, even shooting down enemy planes when the occasion presented itself.

D3A2s most often combined their attacks with the B5N Kate, which resulted in combination strikes that did not secured credits in sinkings for dive bombers alone. However, in many occasions especially for the land-based Kokutai in the Solomons and New Guinea, they operated alone. However D3A pilots were credited single-handedy to sink ships in the cases they succesfully hit destroyers: in the Indian Ocean alone in april, they sunk USS Edsall, USS Pecos, HMS Cornwall and Dorsetshire, HMS Hector, HMS Tenedos, HMS Hermes, and HMAS Vampire in march-April. In the February raid against Darwin, they sank USS Peary and in the Java sea in March, USS Pope. During the campaings of the Pacific in early 1943 they sank USS De Haven, USS Aaron Ward, USS Kanawha, and USS Brownson.

Later operations (1944-45)

The D3A was gradually replaced by the Yokosuka D4Y Suisei “Judy”, more modern, faster and heavily armed. The remaining D3A2s were left on land-based airfields and continued to perform occasional attacks. Some of these dive bombers left behind in isolated islands outpassed in the “island-hopping campaign” were pressed as impromptu fighters/interceptors. Without payload, and despite their fixed undercarriage, they proved very agile. Many encounters with the F4F saw the “Val” survive. Many more shot down allied attack planes.

Remaining D3A2s also still saw servive in small carriers of the IJN, as better suited than the heavier and fast-landing Suisei. A bit like for the F4F and GM Wildcat in 1944 operating from escort carriers, they were still a common asset abord IJN escort carriers in 1944 and 1945. When US forces recaptured the Philippines in 1944, they were attacked by scores of land-based D3A2s. Of course losses were heavy. The remaining models stayed in training units back in Japan, for D4Y pilots, while several were modified with dual controls, becoming the “Navy Type 99 Bomber Trainer Model 12” or D3A2-K.

D3A1 from IJN Akagi

Remaining D3A2s were then used in 1945 kamikaze missions, USS Abner Read, an American destroyer, being sunk by one such kamikaze on 1 November 1944 and USS William D. Porter, on 10 June 1945 off Okinawa. Aichi’s successor of the D3A, a wooden model named D3Y Myojo, was never mass-produced in time.


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On militaryfactory.com
Japanese Bomber Tactics (Navy) World War 2, mil. aviation vizualized
Refs On wingspalette
Full monty on Calameo


Initially, D3A dive bombers were painted silver and the engine black. Unit symbols were generally painted red, white or yellow, including on the undercarriage fairings. Bands indicated the squadron and position. During the summer of 1941 (so before Pearl Harbor started), the paint finish became by default (very)light olive grey. By early 1942, dark green, buit alsways with the engine cowling and forward fuselage paintained black. Like most of Japanese planes this paint wore out quickly leaving to interesting camouflage-like patterns, but no true camouflages were ever applied, at least as regulated.

Mitsubishi M17, 3rd prototype

D3A1 of the first production batch tests in China, early 1940.

Aichi D3A1, 14 Sentai, China 1940

1st Shutai (Squadron), 21 st Section, October 1941

IJN Kaga, December 1941

IJN Shokaku, Pearl Harbor attack

IJN Zuikaku, Pearl Harbor attack

BI-231 flown by Lt. Cmdr. Egusa, 1st Sqn, 21 section, which had two different D3A aircraft garishly painted with unique schemes. The wild scheme in this profile is called ‘Jaja Uma’ (7 December 1941).

D3A1 IJN Shokaku, Battle of Coral Sea, May 1942.

D3A1 late production, 35th Kokutai, late 1942

D3A2 of Yokosuka KoKutai, early 1943

D3A2 of Yokosuka Hikotai in 1943

D3A2 onboard IJN Shokaku in June 1943

D3A2 of the 553th Hikotai, April 1944

D3A2 with droppable fuel tank, late 1944 (55th Kokutai) Island Base

Poster dedicated to the Aichi D3A “Val”, common 1941-43 IJN dive bomber. Full poster with all variants in preparation.

Example of macbook laptop sleeve. Dozens of variants and models possible as well as ipad skins, ipad snap cases, laptop skins, iphone skin and snap cases, soft cases, tough cases, iphone wallet, T-shirts, mouse pade, baseball and dad caps, art, canvas, framed art, metal, photographic print as all scale and effect, postcard and poster, acrylic block, clock, coaster, comforter, duver cover, shower curtain, throw pillow, drawstring bag, print tote bag, mug, cottong tote bag, mask, pin, scarf, tag mug, tarvel mug, water bottle, zipper pouch, greeting card, hardcover journal or spiral notebook… And help our website !

Nakajima E8N “Dave”

Nakajima E8N “Dave” (1934)

Imperial Japanese Navy, 755 built

The “Dave”, standard IJN observation seaplane

The Nakajima E8N was a Japanese ship-borne and catapult-launched reconnaissance seaplane which saw service mostly during the Second Sino-Japanese War. This single-engine, two-seat biplane was given a main ventral float complemented by underwing outriggers. Not fast, but reliable and with sufficient range, it was quickly adopted by all battleships and cruisers in service with the IJN, the remainder affected to isolated islands and stations in the Pacific War. The Allies gave it the reporting name “Dave”.

The E8N essentially was planned as a replacement for the 1930 E4N, from the same firm. The latter, with 153 built, already was a standard observation floatplane of the IJN, catapulted from Cruisers and Battleships. It first flew in 1930 and was introduced in 1931. Production, between the E4N2 (85) and E4N2-C (67) and the E4N3, stopped in 1933, at which point a replacement was in the tubes. Propelled by a Nakajima Kotobuki 2, 9-cylinder air-cooled radial piston engine rated for 433 kW (581 hp), the E4N reached 232 km/h (144 mph, 125 kn) but had a range of 1,019 km (633 mi, 550 nmi). It led also to the confidential P1, the same with undercarriage, land-based (nine built) which saw service from 1934 in the home islands only.

E4N, pinterest
Nakajima E4N1, N2, N3.

The 8-shi competition

The first large-scale competition for aviation projects 7-Shi, held by the headquarters of the Imperial Japanese Navy in 1932, turned out to be quite a successful experience. Of the six programs, four ended with the adoption of a corresponding class model. Among these projects, were the Hiro G2H long-range bomber, the Mitsubishi 3MT5 heavy carrier-based and carrier-based torpedo bomber, and the Kugisho B3Y carrier-based torpedo bomber. But these machines, despite their adoption by the fleet aviation, can only be called successful with some reservations. Their release was very limited, and their combat career was short. Only the fourth project of a long-range ship reconnaissance aircraft, embodied in the Kavanishi E7K aircraft, turned out to be truly successful. The reconnaissance Kavanishi was produced in large series and was in service with the Japanese fleet for more than 10 years.

In the early 1930s, the Japanese fleet staff preferred to have two types of reconnaissance aircraft, one for their large warships, a long-range three-seater, and a short-range two-seater for the cruisers. The project of a long-range reconnaissance aircraft was drafted by the technical department of the headquarters of the Kaigun Koku Hombu, after a long research, ending with the E7K.

The short-range reconnaissance model developed for the IJN by 1932 was represented by a fairly advanced Nakajima E4N1, or Type 90-2, which just had been put into service. In the era of apid aviation development throughout the world, the obsolescence of aircraft technology met such a rapid pace that it would be simply criminal to rely on a successful project just into service for the next ten years.

While the new E4N2 was still being tested, the Kaigun Koku Hombu already prepared specs for new 1933 8-Shi design competition, including requirements for a new short-range reconnaissance model supposed to replace the E4N2. There were no particularly stringent requirements for these projects, as it was assumed that the new reconnaissance aircraft would be a little faster and better than the E4N2 already being tested, and still compatible with the same standard fleet catapults, with a forward and defensive armament, and ability to carry light bombs, possibly dropped after a dive. The only strict requirement was to ensure its maneuverability to cope with modern fighters, and the use of the specific Nakajima “Kotobuki 2” Kai 1 engine (585 hp).

The 8-Shi spec was issued to Kawanishi, Nakajima and Aichi, long-standing rivals for floatplanes in Japan, and the the Kawanishi E8K looked the most progressive, showing a cantilever single-float monoplane, with a two-seats enclosed cabin. Flight data were disappointing however. It was in no way superior to the E4N2 that was to replace and inferior in agility. The Aichi AB-7 biplane and AM-7 monoplane were worked in parrallel but the second was abandoned almost immediately.

Design continuity

E8N bluprint

At Nakajima, it was voted for a continuity of design, extrapolating on the E4N2, only modified under the factory project name “Type MS”. The same design team worked on the new close-range float reconnaissance model under direction of Shinobu Mitsutake, already experienced on the E4N1 and its E4N2 evolution as well as engines specialist Kiyoshi Akegawan under overall direction by Kishiro Matsuo. Matsuo staked all on a simple incremental improvement all cross the board for an easier, faster and cheaper production setup, also allowing technological continuity, same parts supplies, maintenance ease, which all were considered favourably by the examination board.

Outwardly, the new model was very close to the production E4N2, with an upper given a greater sweep, shorter chord, smaller area overall for better agility. To improve fight stability, both the keel and rudder were made taller. In addition, the rudder underside was bevelled. Also the attachment of supporting floats diverged, by using I-struts with cross guy cables instead of N struts. The fabric covering was replaced with aluminum on the wings also, allowing dives. The Type MS project was designated E8N1 for tests, but still almost indistinguishable from the E4N. It first flew in March 1934 and no issues were found, although the cruising speed decreased slightly while top speed improved due to the more powerful engine and less drag.

Development of the E8N

Protoype MS in 1934

The E8N was developed as a replacement for the E4N, an evolutionary development with revised, smaller wings, taller tail surfaces and bigger engine. Seven prototypes were constructed all under the company designation Nakajima MS, at first under private venture, but Nakajima was confident the Navy would soon come with a competition. The first of these prototypes flew in March 1934. As expected, Nakajima obtained an official request, and its prototype was soon engaged in comparative trials against those from Aichi and Kawanishi.

Since the Navy appreciated the E4N, they were confident enough to brush aside the competitors, as for most specs she resorted better overall. The Nakajima A8N was eventually granted the greenlight for production on October 1935, under the official designation “Navy Type 95 Reconnaissance Seaplane Model 1”. About 800 were ordered, but since Nakajima did not have that capacity, Kawanishi took over a large part of the production which went on until 1940. The production ceased however at the 748th to make room for a more modern models such as the Aichi E13A “Jake” (1941), a monoplane, or the Mitsubishi F1M “Pete” (1940), last biplane.


The Nakajima E8N reconnaissance ship was a classic all-metal biplane using a single float and two supporting floats underwings. Like its predecessor the E4N2s it retained the ability to mount a wheeled undercarriage, but this was never used. The fuselage and wing were all-metal. The fuselage forward entire section was framed with aluminium, covered by thin aluminum sheets, while the tail section was covered with canvas. The center section supported four I-shaped struts under which the single float was attached. The wings also as said received an aluminum skin, which was new and augented the plane’s rigidity, enabling a better agility than its predecessor, as calculated between the shorter span and more powerful engine.


IJN Haguro’s E8N spotter plane taxiing after landing. The observer is standing with the cable hook to be hoisted back on board. Colorized by hirootoko JR

The E8N1 was the Initial production type powered by 433 kW (580 hp) Nakajima Kotobuki 2 Kai 1 radial engine and upgraded mid-production as the N2 when was introduced the more powerful (470 kW/630 hp) Nakajima Kotobuki Kai 2 engine. Both acted on a two-bladed, metal, constant pitch propeller. The “Kotobuki” (“Jupiter”) 2 Kai 1 was a reliable, largely used engine developed as a mix between the Bristol Jupiter and Pratt & Whitney Wasp. The Kai 1 was an evolved version of the second model which develped 585 hp (436 kW). Air-cooled, its bore was 146 mm (5.75 in), stroke 160 mm (6.3 in) and it displaced 24.1 L (1,471.1 cu in). It was 1.021 mm x 1,280 mm and weighted 350 kg (772 lb). It was further developed into the 3-Kai of 710 hp (529 kW), never mounted on the E8N as the structure would probably had not tolerated it.


As standard, the E8N was given a fixed, forward-firing single 7.7-mm Type 97 machine gun above in the fuselage, left of the aircraft axis with an interruptor gear. The other was a Type 92 machine gun strapped on a flexible mount around the rear position, manned by the observer and purely defensive. There too was an interruptor on the rail to avoid firing on the tail.

The floatplane also was fitted with two underwings racks, each capable of dropping a 30 kgs (66 Ibs) bomb. The lifting capacity was in reality greater, and it was said capable of lifting two 60 kgs bombs for short range runs. Thanks to the aluminium-covered wings and reinforced structure, dive-bombing was not only possible, but pilots trained for it. This capability was demonsrated in several occasions, but the damage inflicted was minimal.


Production was first setup quickly at the Nakajima plant, in Ota. Later another in Koizuma was specially built for it, augmenting deliveries. The Type 95 reconnaissance aircraft was peoduced until 1940, with more than 700 delivered to the IJN, most of which were Type 95 model 2 (E8N2) which had a greater takeoff power of 630 hp, an important fact to stay aloft in all conditions immediately after launch from the catapults. As the war broke out in China, heavy losses forced the Japanese command to look for replenishments and in 1938 a license agreement was concluded with Kawanishi, for the production of E8N2s at Konan plant (48 more assembled).

Detailed specs

Nakajima E8N “Dave”

Crew: 2: Pilot, Observer
Fuselage Lenght 8.81 m (28 ft 11 in)
Wingspan 10.98 m (36 ft)
Wing area 26.5 m2 (285 sq ft)
Height 3.84 m (12 ft 7 in)
Empty weight: 1,320 kg (2,910 lb)
Max takeoff weight: 1,900 kg (4,190 lb)
Propeller: 2-bladed fixed pitch metal propeller
Engine: Nakajima Kotobuki 2 KAI 9-cylinder air-cooled radial 470 kW (630 hp) at 3,000 m (9,843 ft)
Top speed: 300 km/h (190 mph, 160 kn) at 3,000 m (9,843 ft)
Climb rate: 3,000 m (9,843 ft) in 6 minutes 31 seconds
Endurance: 898 km (558 mi, 485 nmi)
Service ceiling: 7,270 m (23,850 ft)
Wing Loading: 71.7 kg/m2 (14.7 lb/sq ft)
Power/mass: 0.2491 kW/kg (0.1515 hp/lb)
Armament Fixed fwd+ flex rear 7.7 mm Type 97 MG, 2×30 kg (66 Ibs) bombs

The Nakajima E8N in action

Imperial Japanese Navy Air Service’s seaplane Nakajima E8N in the foreground with a Kawanishi E7K seaplane in the background

The Nakajima E8N “Dave” in the fleet

The E8N arrived in late 1935, early 1936 and gradually was supplied too all capital ships and 16 cruisers of the IJN, plus five seaplane tenders:

Battleships IJN Fuso, Haruna, Hyuga, Ise, Kirishima, Kongo, Mutsu, Nagato, Yamashiro Aoba, Ashigara, Atago, Chokai, Haguro, Kako, Kashima, Katori, Kumano, Maya, Mikuma, Mogami, Myoko, Nachi, Suzuya, Takao, Tone Aircraft tenders IJN Chiyoda, Kamoi, Kiyokawa Maru, Sagara Maru and Sanuki Maru

There was no carrier-borne version with undercarriage. It was used from the start of the second Sino-Japanese War by the fleet, and it was discovered it was sturdy enough to perform dive-bombing missions if the need arose, athough she did not carried much ordnance. The rest of her time alternated between observation, reconnaissance and artillery spotting.

The E8N became in fact the short-range catapulted reconnaissance type of the IJN. Obsession with classifications, and with the international context urging some rationalization, the IJN staff wanted to merge the functions of short and long range reconnaissance, and add to this gunnery obervation, patrols, liaison, or carrying out bombing and strikes on coastal targets. In 1939 a new class was drafted, the “Observation Seaplane” (letter F), which ended with the Type 0 (F1M “Pete”) replacing the E8N in the fleet. Nevertheless, the E8N remained in service until the end of 1943 and afterwards in training units.

The arrival of this model onboard IJN ships started in 1936. They were were mainly assigned to battleships and heavy cruisers, mainly for artillery spotting. Light cruisers in IJN doctrine were to be the “eyes of the fleet”, and used the long-range reconnaissance Kawanishi E7K instead. Battleships in fact had enough room to carrt both one single E7K and two or even three E8Ns. Only Yamato and Musashi never operated it, having instead the “Pete” onboard, and other models like the “Rufe” naval fighter.

Also exceptions, the IJN Chikuma and Tone as modified, carried two E7K and three E8N, but composition often changed along their deignated tasks and availability. E8N scouts were also based on many fleet tenders. On for example the four sister-ship Kamikawa Maru, Kimikawa Maru, Kiyokawa Maru and Kunikawa Maru, which carried each six E8N reconnaissance aircraft plus two in reserve, and three E7K, one reserve. The Sagaru Maru and Sanuki Maru had six plus two in reserve, Sanyo Maru, Kagu Maru, Kinugasa Maru carried eight plus four E7Ks. IJN Notoro had eight, IJN Kamoi ​​no less than twelve not counting reserve models.

Composition of the air groups varied, buyt the E8N was maintained as a mandatory model in all cases, a testimony to its recoignised high efficiency depit its near-obsolete features. Even in late 1942, they operated from IJN Sanyo Maru which also had six F1M1 “Pete” and two E13A1 “Jake”.

Active Combat career 1936-1943

E8N scouts started just when the 2nd Japanese-Chinese incident took place. Scouts brought previous reconnaissance data, released from many fleet tenders and where there was no opposition, being used a dive bombers anf to straf opportunity targets, even as escort fighters in some cases. In August 1937, 21 kokutai operated E8N scouts in northern China, 22 kokutai in central and southern China, in addition to IJN Kamoi own models off the coast. On August 14, 1937, there was a counter-raid of some 40 Chinese Northrop “Gamma” bombers escorted by Curtiss “Hawk” III on the HQ of the Japanese 3rd Fleet, in Shanghai. At thioer second sortie they were intercepted by a mix of E7K rfrom IJN Izumo and E8Ns from IJN Sendai. On E8N managed to shot a hawk with a well adjusted, lucky burst. Pilot Liang Hun Yun died in the event. A Chinese Gamma bomber was also shot down. This was the exception however.

The E7K and E8N were easy prey for modern fighters in general. On August 16, the first E8N1 was lost in action, shot down NW of Shanghai by 24th Sqn. Captain Liu Chui-Kang on his Hawk III fighter. On August 20 he shot down another over the Yangtze River, NW of Shanghai, despite it was escorted by a Nakajima A4N1 fighter. The fighter was dealt for first. Another E8N was lost over Shanghai on 4 September 1937, followed by others in September, as well as in October 1937 when the first two E8N2 (from IJN Kamoi) were also shot down.

In January 1938, one E8N2 (from Kamoi) shot down a Chinese reconnaissance Vought V-65 “Corsair” over Canton and another the the next day dogfighted for 10 minute with a lone Chinese Gloster “Gladiator”, both surviving and breaking off. In February 1938 some from Notoro and Kinugasa Maru carried many attack missions in addition to their observation duties. On February 24, all 13 E8N were in the sky to attack the city of Nan Hsiyung with bombs, others being used as fighters. They were intercepted by three Gloster Gladiator (28, 29 Squadrons). Some were shot down but one E8N place itself in a frontal attack position and shot down one with a single burst, hitting Lieutenant Young in the head. Gladiators MGs tended to fail also due to low-quality Belgian cartridges, which saved the Japanese at this point. Most went back. The Chinese lost two Gladiators, two damaged, claiming only two E8N2, three damaged, which was quite even.

The records showing the Japanese extensively used their floatplanes for all sorts of missions also showed acute shortages on some areas over China. The front, which stretched thin inland, and Chinese fierce resistance was grinding down the effectivness of all squadrons. The E8N2 bomb load was light, but they could effectively dive and thus hit targets with better accuracy than levelled attacks. Training included dive bombing in fact and E8Ns could be surprisingly deadly in precision bombing. By mid-May 1938, the IJN Kamikawa Maru joined the fray, deploying some 12 E8N2s and operating in Hukou area, intercepted by five Gladiators (28 Sqn). Japanese scouts however put quite a fight due to their surprising agility for floatplanes. After 1:50 however, the die were cast with six “Dave” down.

The “Dave” in WW2

In December 1941, the E8N was considered obsolete, but still equipped the fleet until it was re-equipped by the new Aichi E13A1 and Mitsubishi F1M2. The Allies classified and named it believed these were still modern by Japanese standards. They stil served in many units at this point: Combat training “Hataka” kokutai, Kure (48), Yokosuka kokutai (12), Komatsujima kokutai (8), “Iwakuni” kokutai (8 or less), and most IJN fleet tenders patrollig off China. Those were used as light bombers with mixed success due to shortages.

On June 3, 1942, E8Ns saw action the Japanese for the raid on Dutch Harbor (Aleutians) screening for 9 Zeros, 12 D3A/B5N bombers, marred by heavy fog. Four E8Ns from Takao, Maya reached Makushin Bay and did their job, throwin their two 60-kg bombs and attacking the five USN destroyers in the bay, all missed. On their way back, they were intercepted by two land-based P-40E fighters, with two lost. On February 27, 1942 at the battle of Java Sea, E8N2 from Nachi and Haguro adjusted long-range fire, contributing to their many hits. On April 9, 1942 a single “Dave” from IJN Haruna spotted off Ceylon the aicraft carrier HMS Hermes, later attacked and sunk by a massive strike.

On December 25, 1941, two “Dave” from IJN Chokai shot down a Dutch Dornier Do-24K off the coast of Anambas Island, South China Sea. E8N scout far north also took place in the incident in which the Soviet transport Angarstroy on April 19, 1942 on her way to Vladivostok, met by four battleships and eight destroyers and ordered by a dropped injunction on deck by a “Dave” to change course. The E8N was largely in service by December 1941, providing crucial reconnaissance from IJN Haruna notably during the Battle of Midway, but by late 1942 most had been retired from surface vessels and relegated to second-line duties in remote pacific islands and home waters. The last were still used for training floatplane pilots in 1945.

The Kriegsmarine E8N

The E8N had such reputation that by early 1941 the German Naval Attaché to Japan, Vice-Admiral Paul Wenneker asked to have one purchased. It was ferried on board KM Münsterland, which later met the German auxiliary cruiser SMS Orion, at Maug Island (Marianas), on 1st February 1941. KMS Orion became the only WW2 German warship to operate a Japanese float plane. Donated to Germany as a goodwill gesture, and this particular model took an active part in the preparation of the local raid of “Orion” from the end of 1940, roaming the Indian Ocean. It was disguised as a RAF model with typical British cockades, mimicking some colonial 2nd line model or lend-lease “Seagull”. However its only contribution was to spot the cargo ship “Chaucer”. Its fate is unknown. Orion was renamed Hektor in 1944 and Orion again in 1945, not surviving the war as she was sunk in an air raid on 4 May 1945.

The Thai E8Ns

In 1938, the Kingdom of Siam ordered 18 E8N, an order completed only by September 1940 when they arrived. They received the designation BTL-2 and actually took part in hostilities, patrolling the coastal zone near the Cambodian border but not participated in the war against France. They were only retired in 1946.


World Air Forces – Historical Listings Thailand (THL)
Francillon, Rene (1979). Japanese Aircraft of the Pacific War. Putnam & Company Limited.
Joao, Matsuura. “WWII Imperial Japanese Naval Aviation Page”.
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E8NOn super-hobby.fr
RS models 1/72
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The E8N on Scalemates, all manufacturers, all scales

Nakajima E8N1, IJN Nachi, 1936

E8N1, Fleet tender IJN Kamoi, East China sea June-july 1938

E8N2 Armored Cruiser IJN Izumo, 3rd fleet flagship, Shanghai 1939

E8N2, AI-2, Battleships IJN Nagato, October 1941

E8N1 Yokohama Kokutai, Kanagawa prefecture, circa 1944

Maintenance Training E8N2 of SeiRen 65 Yokosuka Kokutai, Japan 1944

E8N2 of AsU-22, Amatsuka Kokutai (seaplane base), Japan Summer 1945

E8N1 of the Royal Thai Force, 1942

E8N1 on KMS Kormoran, Pacific 1942, with fake British markings

Nakajima E4N

E4N squadron

Type 95 Suiki Suitei

Nakajima E8N

E8N lifted onboard a cruiser by crane in harbour

E8N being catapulted

E8N “Dave” in flight Formation

Yokosuka B4Y “Jean” (1935)

Yokosuka B4Y “Jean” (1935)

Imperial Japanese Navy, 205 built

Mitsubishi B2M
The Mitsubishi B2M which needed replacement (1932), derived from the Blackburn Ripon

The Yokosuka B4Y, also called Navy Type 96 Carrier Attack Bomber was the specialized torpedo bomber of the IJN, and last biplane of that type before the arrival of the B5N “Kate”. Introduced in servive from 1936, it equipped all IJN aircraft carriers and was still in use by 1943 in China, in second line and training units. The B4Y replaced the Mitsubishi B2M2 as the last operational biplane by the IJN. It was known by the Allies as “Jean”.

Design development

Yokosuka (Kogisho) B3Y
The previous Yokosuka B3Y (1932)

In 1932, the Imperial Japanese Navy issued a requirement for a new carrier-borne attack aircraft, submitted to Aichi, Mitsubishi and Nakajima. All three answered to it, while building their own prototype. None however deemed satisfactory. Yokosuka (Kugisho at the time) proposed the B3Y, which was evaluated but deemed inadequate for the role. The service issued in 1934 a new requirement calld “9-Shi”, for a better model.

The 1934 9-shi competition

In 1934, the technical department of the Imperial Japanese Navy announced the third competition over the past five years (one yearly) to determine the best possible carrier-based torpedo bomber, and replaced the B1M, B2M and B3Y generation. The 9-Shi specification went to Mitsubishi, Nakajima, and the 1st Marine Technical Aviation Arsenal (Yokosuka). This specification was initially considered temporary as a new competition was already prepared. It was supposed to produced a fundamentally new monoplane torpedo bomber. All its parameters were to be on par -ideally- to the nimble and agile A5M fighter.

At the time, in 1934, capabilities of the Japanese aviation were certainly not able to produce anything near the asked specification, while the fleet urgently needed a new generation, and dissimilar biplanes destrimental to maintenance and training, which in addition belonged to different generations between themselves. Mitsubishi and Nakajima hurried to a project, and the fist took the previous B3N as a base. It choose to increase its engine power and present it as the B4N, with X-shaped wings.

Mitsubishi did the same, just starting over a modified 3MT10, a project developed for the 7-shi specification competition: It was its Ka-12 (B4M) torpedo bomber. Both prototypes took off in late 1934, Yokosuka Arsenal lagging behind to deliver its own model. Meanwhile, the team work fevershly under Sanae Kawasaki. The latter emphasized the use of already proven solutions, an enough modularity to install any engine, which also allowed easy upgrades.

To accomplish this, Kawasaki worked on a biplane wing box derived from the Kawanishi E7K1 with Yokosuka’s newly developed fuselage. The first hybrid was equipped with the “Hiro-Type 91” 600 hp engine. It first flown late 1935 and in early to mid-1936, four more prototypes were produced by Yokosuka with Kawasaki, with the second and third powered by the 640 hp Kotobuki-3 air-cooled engine. The fourth and fifth prototypes received the Nakajima Hikari 2 capable of 840 h.p. Each time, reinforcements were brought to the whole structure, so see if it can cope.

As a result of these internal tests at Yokosuka, it was found that the marriage between the B4Y1 fuselage with the Hikari-2 engine was cleary a head above the compeition, although still hardly matching the 9-shi very ambitious navy specs; By November 1936, an order was received by Mitsubishi, Nakajima and the 11th Sea Aviation Arsenal while Yokosuka answered officially with its Yokosuka B3Y, keeping the same formula between orders and just improving on the engine and overall perfomances. This allowed nevertheless to innovate, as the B3Y became the first Japanese carrier attack bomber, fitted with the air-cooled radial engine Nakajima Hikari 2. The B4Y derived from it retained its fixed spatted landing gear, but introduced for the first time an enclosed cockpit for the navigator and radioman/gunner behind, not disturbed by the greater air flow due to the speed. The pilot however to keep max visibility still had an open cockpit, with just a standard windshield. Even the very fast A5M fighter, as the Army “Nate” also kept an open cockpit at the time.

About Yokosuka and the IJN

Kaigun Kōkū Gijutsu-shō (海軍航空技術廠) was created in 1913 as “Naval Air Technical Arsenal”, later simplified as “Kūgi-shō”, as it was associated with the first IJN arsenal, funded 1869, at Yokosuka, about 13 miles south of Yokohama on Tokyo Bay. When evaluating new planes (purchased from abroad), the Navy brought them to the arsenal for assembly from their crates, until they were flown by pilots sent abroad for flying lessons, tasked of final evaluation before any foreign purchase.

Modifications were made on site as weaknesses were found and/or when improvements were asked for. The IJN established in May 1913 a workshop on site, called the “Aeroplane Factory” under supervision of the Ordnance Department, at the arsenal’s torpedo factory. The facility was renamed “Naval Establishment for Aeronautical Research” (December 1919), then “Naval Technical Research Institute” in April 1923, then relocated to Tsukiji with several other Naval support units. As the latter waqs destroyed following the Great Kanto earthquake, a new one called Kaigun Kokusho (Naval Air Arsenal) was stablished in 1932 near Yokosuka, where draftsmen and Designers were transferred from the Hiro Naval Arsenal, closed.

Yokosuka was responsible for the 1918 mass-produced Ro-go Ko-gata reconnaissance floatplane, for the B3Y (1933, 129 built) biplane torpedo bomber which preceded the B4Y, the D2Y, D3Y, D4Y Suisei ‘Judy’ and D5Y dive bombers, scores of reconnaissance flotplanes, flying boats, trainers, transport and special purpose machines like the human missile “ohka” in 1945.

Design of the B4Y

Yokosuka B4Y
3-views plan

The B4Y was designed by Sanae Kawasaki at the First Naval Air Technical Arsenal at Yokosuka. Regarded only as an interim type, the Navy wanted a torpedo bomber offering performance comparable to the Mitsubishi A5M monoplane fighter. The result was a biplane with fixed landing gear and an all-metal structure with metal or fabric skin. To speed development and production, the B4Y utilised the wings from the Kawanishi E7K. The B4Y1 was also the first Navy carrier attack aircraft to utilize an air-cooled engine, as the prototype that was equipped with the Nakajima Hikari 2 radial engine performed better than its opponents. The crew of three occupied two cockpits. The pilot in the open front cockpit and the other two crewmen, (navigator and radio operator/gunner), in the enclosed rear cockpit.


The Nakajima Hikari 2 developed between 750 and 840 hp (560–630 kW). It was a 9-cylinder air-cooled radial aircraft piston engine with bore of 160 mm (6.3 in), stroke of 180 mm (7.1 in), displacement of 32.57 L (1,988 cu in) and diameter of 1.375 mm. It was as said, air-cooled, and was a relatived to the earlier Nakajima Kotobuki, based on the earlier licenced Bristol Jupiter.


There was no fixed machine-gun forward for the pilot to fire. The only armament on board, outsid the payload, was a single, flexibly mounted and rearward-firing 7.7 mm (0.303 in) Type 92 machine gun manned by the rear gunner. Its payload was more diverse, consisting either of a standard airbone 800 kg (1,764 lb) torpedo*, or 500 kg (1,102 lb) of bombs, generally small 50 kgs bombs under racks, generally two racks of six mounted under the wings.

This model was sturdy enough to perform dives, although this was noever done in practice. Regular strafing and levelled attacks only. Due to the use mostly in China, there are no records of ships torpedoed by the “Jean”. They were almost always operated as bombers. The torpedo was likely the standard 45 cm (17.7″) Type 91 (1931) Mod 1. It was given a 331 lbs. (150 kg) Type 97 warhead and was capable of 140 HP / 2,200 yards (2,000 m) / 41-43 knots thanks to its Kerosene-air wet-heater.


The accepted serial aircraft received the ordnance designation “deck torpedo bomber sea type 96”. The model was commonly known also by its reduced factory/model navy designation of B4Y, where “Y” stands for yokosula. A total of 205 B4Y1 were produced, including the 5 prototype, so 200 standardized production models. The 5 prototypes built with various engines in 1935-36 were created at the arsenal in Yokosuka, but since the latter did not have the facilities for mass production, the order was spread among manufacturers:
-Nakajima Aircraft Company: 37 aircraft in 1937-38
-Mitsubishi Heavy Industries (Nagoya): 135 aircraft in 1937-38
-Hiro 11th Naval Arsenal: 28 aircraft in 1938

For the Yokosuka B4Y being produced in 1938 meant it was expected to serve at least until 1941. But already the age of monoplane was launched and either structurally or by data, biplanes were condemned so this model was already obsolescent. From early 1937, they started to actively replace the existing models of previous generations, on carrier-based air groups. It became in 1939 when all were delivered, the standard torpedo-bomber onboard carriers of the Kido Butai: IJN Hosho, Ryujo, Akagi, Kaga, Soryu and Un’yo, as well as the coastal Kokutai 13 and 15.

Detailed specs

Specs Yokosuka B4Y

Crew: 3: Pilot, navigator/observer, radio operator/gunner
Fuselage Lenght 10.15 m (33 ft 4 in)
Wingspan 15 m (49 ft 3 in)
Wing area 50 m2 (540 sq ft)
Height 4.36 m (14 ft 4 in)
Empty weight: 2,000 kg (4,409 lb)
Max takeoff weight: 3,600 kg (7,937 lb)
Propeller: 2-bladed fixed pitch wooden/metal propeller
Engine: Nakajima Hikari 2, 9-cyl. AC radial 630 kW (840 hp) TO, 522 kW (700 hp)/1,200 m (3,937 ft)
Top speed: 278 km/h (2173 mph, 150 kn)
Endurance: 1,573 km (977 mi, 849 nmi)
Service ceiling: 6,000 m (20,000 ft)
Wing Loading: 72 kg/m2 (15 lb/sq ft)
Power/mass: 0.1749 kW/kg (0.1064 hp/lb)
Armament 1x 7.7 mm Type 92 MG rear, 800 kgs torpedo or 500 kgs bombs

The B4Y in action

B4Y in 1938 flying over IJN Akagi

The Yokosuka B4Ys was first introduced in 1937, and saw action for the first time in the Sino-Japanese War. The first unit to operate the model was the 13th Kokutai. They helped to destroy the Chinese cruisers based in the Yangtze in September 1937. They were also responsible -in part- of the scontroversial sinking of the gunboat USS Panay, off Nanking in December. Identified sooner, the allies gave it the codename “Jean” for easier identification. The Allied Reporting Name was a reference to General MacArthur’s wife.

Operations in China 1937-41

On September 7, 1937, six B4Y from IJN Kaga, escorted by three A5M fighters, raided the coast when they were intercepted by three Chinese Hawk III fighters (led by deputy commander, 22nd fighter group, Lieutenant Lai Ming Tang). Lieutenants Lu Ji-Chun and Zhou Geng-Xu attacked the bombers while the leader dealt with the three Japanese fighters. Lu and Zhou shot down soon one B4Y each, but Lu Ji-Chun was soon obliged to make an emergency landing, wounded by one B4Y tail gunner.

On December 12, 1937, three B4Y1 from Kaga sa said above, spotted and attacked (with bombs) the gunboat USS Panay anchored on the Yangtze River.

B4Y in camouflaged livery operating over China

In April 1938, B4Ys from IJN Soryu also operated in China, nine in all which flew to the Nanjing airfield, for operations over the Yangtze. In April also, the newly formed 14 kokutai arrived in China, and included 18 B4Y, al painted with a green-brown camouflage. In July 1938, 15 kokutai was created, also in the same area, operating nine B4Ys. Despite extreme combat activity the B4Y carrier-based torpedo bombers had little to do. The bulk of the Chinese fleet has been dealt by bombers already.

The front in addition soon moved far from the coast and the IJA bases and airfields soon took over the operations. Japanese carrier-based torpedo bombers still operated from ground airfields in late 1938 and along 1939, making only routine patrols on the shores and along the Yangtze River coast (as assigned to the IJN). No longer the Chinese aviation caused troubles to these operations. All these IJN aircraft carriers anyway stuck to the coast of China as assigned, but soon ran out of targets, only be used for reconnaissance and spotting, and training in between.

WW2 Operations

B4Y1s from December 1941 were replaced already on carriers by the B5N from 1939, and practically disappeared from the fleet’s combat strength. From 1942, they were sidelined, used as trainers in second line airfields in home waters, and in China, as well as from the training aircraft carriers IJN Hosho and Un’yō, until 1943. By June 1942 however one “Jean” from IJN Hosho in second echelon at the Battle of Midway, spotted the crippled IJN Hiryu on the 6th.

At the end of 1941, the Suzuka Kokutai still included 24 B4Ys for advanced flight training, located at the Suzuka airbase, in Mie Prefecture (east coast of Honshu). It was a combat training unit which trained and certified no less than a third of Japanese naval pilots. They soon made the transition to the B5N and its replacement later. B4Ys from Suzuka were actively used for training but also regularly flew on combat patrols along the coast, but also used as target-tug and other second-line tasks. The last of them were written off by the fall of 1944, completely worn out. There is no reported use of any for Kamikaze missions in 1944, they were too slow to be used as such anyway.


Evgeny Aranov. Carrier-borne torpedo bombers
Andrey Firsov: IJN Aviation
Aviation and Time. A. Demin. Air Dragons of the Celestial Empire
Rene J Francillion. Japanese Aircraft of the Pacific War
Shuppan Kyodo. Encyclopedia of Japanese aircraft

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The modeller’s corner

WoW rendition of the B4Y

On Scalemates

Yokosuka B4Y1 onboard IJN Akagi in 1938

B4Y1 IJN Akagi, Autumn 1937

B4Y1 13th Kokutai in China

B4Y1 IJN Kaga operatin in China 1938

B4U1 of the 12th Kokutai in China

B4Y1 in China, unknown unit, yellow band

B4Y1 of the 12th Kokutao winter 1938-39

B4Y onboard IJN Soryu, December 1939

B4Y dropping bombs over China

Early production model in Navy white livery

Navy Model being serviced.

Navy B4Ys in a land base, China 1937

Type 96 in camouflage livery with its typical bomb load over China

Mitsubishi A5M “Claude” (1937)

Mitsubishi A5M “Claude” (1937)

Imperial Japanese Navy, 1085 built

The main IJN fighter in 1940

The Mitsubish A5M (allied designation “claude”) was until the arrival of the legendary “zeke”, the main Japanese Imperial Navy Fighter. Designed alongside the Army Fighter Nakajima Nakajima Ki-27 “Nate”, this was the first generation monoplane of this type, supremely agile, relatively tough, but still transitional with its fixed undercarriage and open cockpit. Despite of this, the “Claude” equipped all IJN aicraft carriers until 1940 and was massively used in China, seeing active combat in some areas until mid-1943.

“Japan can’t do planes, just mediocre imitations”

In the mid-1930s, high-speed monoplane fighters started to enter air forces in increasing numbers despite many aviation specialists and manufacturers still believed just was just a “fad” and that biplane offered more advantages. Biplanes were the mainstay of fight deck aviation, with perhaps te exception of the French Bearn’s parasol monoplane Dewoitine 371. In that case, due to the limitation of landing speed due a small flight deck.

By 1935 however a new generation of fixed-wheeltrain, open cockpit transitional cantilever (low wing) monoplanes appeared, for the Air Forces at first. It was not long before carrier-based fighters appeared. The world’s first one appeared from Japan, a country believed to have backwards factories and designers that were only able to copy Western designs. The fallacy of this was realized when Westerners fought in Chiang-Kai-Chek’s aviation during the second sino-Japanese war. Reports came back of a strain of victories won by a small, super-agile A5M, of which the West knew little.

With significant gaps in requirements for land and ship fighter aviation, efforts concentrated on high-speed single-seat monoplanes. But these requirements were still contradictory, for taking off and landing, with a low specific wing loading, and high structural strength. The switch to all-metal high-speed monoplanes faced many difficulties both in Japan and abroad.

Development start: 1935 IJN specs for a carrier-borne fighter

In 1935, the biplane Nakajima I-95 biplane, offering 350 km/h, was adopted by the Imperial Japanese Navya as the A4N. The Main Directorate of Naval Aviation came to the conclusion a top speed of onlu 350 kph was going to be soon obsolete. So requirements based on a new engine, led to tactical and technical No.9 Navy (“9-Si”) specifications. They required a a high-speed monoplane, able of speed up to 400 km/h. It was restricted to companies working already with the Navy and wit a recoignised knowhow, Mitsubishi and Nakajima.

The Admiralty No. 9 requirements called for the following:
Speed ​​over 350 km/h (190 knots) at an altitude of 3 km (9,842)
Climb 5,000 meters (16,400 feets) in 6.5 minutes.
Fuel capacity over 200 gasoline liters
A pair of standard machine guns
Span less below 11 meters (36 feets), length below 8 meters (26 feets)
This specification was offered to Mitsubishi and Nakajima, abd were ready by the fall of year.

Design development

Ka-14 Prototype

Mitsubishi Ka-14 prototype

The A5M carrier-based fighter was designed on the basis of the 9-Shi technical requirement issued at first in February 1934. It determined only basic data for the new aircraft, without limiting the layout. This made it possible for superstar designer Jiro Horikoshi, leading the design team from Mitsubishi Jukoge. He wanted right away a very innovative model, but sketched several options, including one-and-a-half-plane (sesquiplane) with small lower wings, and a fully cantilever monoplane designated Ka-14. The desire to increase the maximum flight speed with span restrictions due to aircraft carrier’s cargo lifts led a high wing load of 77.2 kg/m2. The Ka-14 was designed very quickly, in just 11 months, the first prototype being ready at that point, with which such a tight construction control it ended even lighter than initially precognized.

Based on the lightest structure, with the more suitable power specs, the Nakajima “Kotobuki” 5 radial engine (developing up to 600hp) was chosen, mated to a two-blade metal propeller. The undercarriage was non-retractable with wheels covered by drop-shaped fairings. According to designers, a retractable undrrcarriage would have gave a speed increase of only 3% while significantly complicate the undecarriage and raise its weight. The prototype was made with all-metal construction, combining high strength and lightness combined with good aerodynamics, and gull wings. It promised a big leap forward in flight performance.

On February 4, 1935, test pilot Kajima made the maiden flight onboard the Ka-14 prototype. In factory tests, the prototype showed a speed of 444 km/h (xx mph) at an altitude of 3200m (xx feets). Which was way above the required 350 kph. Other requirements were also all exceeded, so the representatives of the fleet did not even believe the company and asked control tests by their own naval pilots. The first to test the Ka-14, Kobayashi, flew at the Kagamigahara base, and obtained an amazing 449 kph out of the prototype, blowing away all the navy’s expectations.

Five other Prototypes

The second prototype was revised by designers as given flaps to improve its landing qualities, very important for deck landing and lengthened the fuselage, installing a new gearless engine Kotobuki 3 with a maximum output of 715 hp plus the wing was in “reverse gull” was replaced by a more standard cantilever one. The result was improved handling and stability, without compromising flight performance. Speed ​​was not everything and dogfighting was the main requirement.

The Ka-14 was more agile than many biplanes and in Japan, maneuverability was traditionally highly valued, but insufficient on the Ka-14. Pilots of the Yokosuka Experimental Squadron conducted training air battles with the Ka-14 and their conclusion was that they preferred the proven Nakajima A4N1.

Only the arrival of a generation of younger pilots preferring speed and vertical evolutions (contrary to the traditional instructions) made it possible to unleash and reveal the true potential of the new fighter. In the fall of 1936, the Ka-14 was eventually adopted as the “Type 96 Model 1 carrier-based fighter” or A5M1. The serial A5M1 differed from the second prototype by an increased fuel reserve, slightly altered engine hood, the 2KAI-Ko Kotobuki rated for 630 hp. The outlines of the upper fuselage and vertical tail also changed. The armament now consisted of two standard 7.7 mm type 89 machine guns, noth located at the top of the fuelage. The undercarriage was redesigned, provided a better suspension and a rack to add a droppable gas tank under the fuselage. At first the drop tank was half-buried in the fuselage. Tactical unit development of the new fighter with close collaboration of combat pilots started in the first months of 1937 and the A5M officially entered the 13th air squadron as its first active units.

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Design choices

Final production A5M1, codename “claude”

The main concept behind the fighter was developed at meetings with specialists from the Navy’s Main Directorate of Aviation and the head of the Navt department, Rear Admiral I. Yamamoto. To lighten the fighter and increase its maximum speed, the mandatory ship-based operation specs were willfully excluded from the initial design, in ordere to reach max performances right away. The Mitsubishi Ka-14 represented a brand new generation of aluminum monoplanes for the Imperial Japanese Navy and D. Horikoshi low-wing layout, fixed landing gear, open cockpit, low cantilever wing in “reverse gull” configuration were all brand new. The marriage of this base to the Kotobuki series 9-cylinder radial air-cooled Nakajima engine seemed to be a perfect match. The two 2 synchronized AP-89 MGs seems “light” to WW2 standard, but they were in light of interwar standard fighter armament, inherited from WWI. To improve aerodynamic qualities for the first time in the Japanese aviation industry, blind riveting was used for the entire aircraft. To reach the level of the A5M for pre-production, Mitsubishi won approval of the construction of 6 prototypes, only the first of these fitted with gull wings.

Comparison with the A4N and compromise

In the winter of 1935, with a top speed rated at 450 km/h (243 knots) and 5,000 m reached in 5 minutes. 54 sec. D. Horikoshi created with the Ka-14 the best-performing plane ever built in Japan, but it was not agile, nor fit for carrier-based duty, not having the standard Navy kit installed. There was competition, and the Ka-14 competed against Nakajima’s Ki-11 KB (I-95) soon dropping out of it as the problem with the wing struts compromised its controllability.

The Navy, like the Ground Forces eventually rejected all future Nakajima biplane fighters in favor of the Mitsubishi. The Nakajima’s performances and characteristics were still superior to specs, but the overall impression was that the Mitsubishi was still wa superior to the Ki. 11. In the summer of 1935, Minoru Genda’s squadron tested the Ka-14 “to the bone”, and noted its speed, rate of climb, and especially its stability when firing were all extremely important for air combat.

He noted its lack of maneuverability in comparison with the I-95, and when soon at the head of the department of the Navy, Yokosuka (T. Onishi) made a proposal to keep both models, the A4N and A5M, in service. Listening opinion of experienced pilots, the Aviation Directorate eventually organized a training battle between both models, flew by the most experienced pilots at Yokosuka base. They all became ardent supporters of the monoplane, speaking ofits outstanding performances over Kagamihara airfield, on very high throttle response.

The final choice of engine

Nakajima Kotobuki Hikari

Despite the very positive attitude of fighter pilots, fine-tuning for adoption into service dragged on for almost 3 years. The main reason were aerodynamics fixes, problems with ‘floating’ when deck landing, and yawing at high angles of attack, plus the choice of a suitable engine. Aerodynamic design problems led to the abandonment of the reverse gull wing for a conventional straight wings and from the third prototype, the gearless power plant rated for 640 hp were installed. Take-off weight was superior but the new prototype still showed the same performances data, but with safer handling. In total, 4 prototypes of the new cantilever fighter with the Nakajima Kotobuki/Hikari radial, 9-cyl. engine were tested as well as the in-house Mitsubishi-Venus (Kinsei) rated at 730 hp.

Comparative test led to the adoption of the Nakajima engine for serial production. The Kotobuki was derived from the 1920s Bristol Jupiter VII (on the IJN tested Gloster Gamecock), combined with a purchased Pratt & Whitney Wasp 9-cylinder radial. The 450 PS “Kotobuki” (“longevity”) was first tested by the Nakajima A2N, then approved on the Nakajima C3N in 1931 and later lightened, called the “Hikari (light)” model, adopted by the A5M in its 2-Kai-1 585 hp (436 kW), 2-Kai-3 610 hp (455 kW) and 3-Kai 710 hp (529 kW) variants.


Together with the DB-96 version, long-range torpedo bomber adopted the same year, the I-96 (A5M) was the first independently designed plane created by the Mitsubishi Design Bureau (no British assistance at any level until in the 1920s). Despite some difficulties, the Navy’s Main Directorate of Aviation decided to accept the I-96/A5M and by the fall of 1936, it went to more factory tests, with Navy standard additions, until an order for serial production was obtained. The production amounted to 1,100 units plane, with a production run from 1936 to 1940 in the Mitsubishi-Nagoya plant, of 788 planes, and 39 afterwards at the Watanabe plant, until 1942. The former indeed swapped on the A6M in between. Also, Navy Aircraft factory N°21 at Omura built a further 264 A5M5 until 1944. It looks amazing that a 1935 model was produced that late in WW2 despite being obsolete, but this last batch was entirely made of double command/cockpit advanced training models.

A5M design

tech drawing
tech drawing of the A5M4, 3 views, cc

Single-engine all-metal low-wing aircraft. The fuselage of semi-monocoque oval cross-section, elliptical wings and tail of the classic scheme. The fuselage and wing are all aluminum, and the control surfaces are covered with cloth. The cockpit is open (some of the cars of the second modification had a closed canopy. The chassis is three-point fixed with the main struts closed by aerodynamic fairings. All modifications, except for the second, were equipped with aircraft engine options. ), on the second modification (2.98 m). The gas tank capacity is 330 liters, on the second modification PTB with a capacity of 160 liters. Armament (except for the experimental cannon vehicle) from the synchronized AP-89 (Vickers-Arisaka 7.7 mm). modifications had wing pylons for OFAB-30.


Guns: Two 7.7 mm (0.303 in) Type 97 aircraft machine gun fuselage-mounted, synchronized light machine guns. They fired through the engine cylinders and propeller at about 1 and 11 o’clock, with interruptor gear.
Bombs: Although not their primary vocation the A5M could carry two 30 kg (66 lb) bombs underwing, or a single 160 l (42.27 US gallons, 35.20 imperial gallons) drop-tank.

Service debuts

The A5M1 in serial production was followed by the A5M2-Ko with the Kotobuki 2KAI-3-Ko engine in an elongated hood, with a three-blade propeller and an even more developed gargrot, A5M2-Otsu with a closed cockpit and a Kotobuki engine 3. From the closed cockpit, which constrained review, quickly abandoned, replacing it with an enlarged visor. The Mitsubishi plant in Nagoya at that time was joined by the fleet’s aviation arsenal in Omura, where the assembly of the A5M2-Otsu was also established. A number of A5M variants were built that did not go into series, such as the A5M1-Ko armed with a pair of 20-mm Oerlikon cannons and the A5M3-Ko with a French Hispano-Suiza 12Xcrs inline engine and a 20-mm cannon that fired through the hollow propeller shaft. Two experimental modifications, named Ki.18 and Ki.33, were manufactured for the Army Air Force, but they could not compete with aircraft from other companies.


A5M2b, immat. 3-104, 1938

Serial production A5M1: Kotobuki-2 engine (580 hp) or Kotobuki 2M (585 hp), and synchronized Type-89 MGs (500 rds.)
A5M2 early type: Kotobuki-M (610 hp), three-bladed metal prop.
A5M2 medium type: Kotobuki-3 (640 hp), closed cockpit, OFAB-30 droppable tank rack
A5M2 late type: Kotobuki-4 (710 hp) OFAB-30 rack or PTB 210
A5M2K: About 102 by Navy plant No. 21

A5M3 early type: Two Oerlikon FF 20 mm air cannons
A5M3b with Hispano-Suiza HS.404 engine-cannon (610 hp, 20 mm)


Ka-14: Six prototypes with various engines and design modifications.
A5M1: Navy carrier-based fighter, Model 1: first production model with 633 kW (850 hp) Kotobuki 2 KAI I engine.
A5M2/2a: Model 21: More powerful engine.
A5M2b: Model 22: First production examples with NACA cowling and 477 kW (640 hp) Kotobuki 3 engine.
A5M3a: Prototypes with 448 kW (601 hp) Hispano-Suiza 12 Xcrs engine.
A5M4: Model 24 (ex-Model 4): The A5M2b with different engine, closed cockpit, additional detachable fuel tank. The last production models (Model 34) with Kotobuki 41 KAI engine.
A5M1-A5M4: 780 constructed by Mitsubishi. 39 constructed by Watanabe, 161 manufactured by Naval Ohmura Arsenal.
A5M4-K: Two-seat trainer version of A5M4, 103 constructed by Naval Ohmura Arsenal.
Ki-18: Mitsubishi Ki-18, Single prototype land-based version for IJAAF, based on the A5M. 410 kW (550 hp) Kotobuki 5 engine.
Ki-33: Mitsubishi Ki-33, Two prototypes, a development of Ki-18 with a different engine, and closed cockpit.
Total Production (all variants): 1,094

About the Ki-18

In 1934, Mitsubishi developed a prototype for IJN, the Ka-14 9-Shi, showing outstanding performance, so much so that with Navy’s consent, the Army placed a order for a modified version, in order to be evaluated. It was soon designated Ki-18.

Like the Ki-14 it was a low-wing monoplane, all-metal, however fabric-covered control surfaces. Its engine was the Nakajima Kotobuki-5, a nine-cylinder radial rated at 410 kW (550 hp) taking off and up to 447 kW (600 hp) at 3,100 m (10,170 ft) with the same two-blade, fixed-pitch, but this time wooden propeller.

From the second Ka-14, the inverted gull wing had been modified into a straight model the Ka-18 retook, and it had an enlarged rudder, a larger landing gear also with spats and different engine cowling. The direction of the throttle was adapted to Army practice (reversed) while the machine guns were Army models 7.7 mm (.303 in) Type 89 machine guns.

The Ki-18 first flew in August 1935 at the Tachikawa Air Technical Research Institute, and later at the Akeno Army Flying School. By early 1936, the engine was replaced: The new Nakajima Kotobuki 3 (477 kW/533 kW (715 hp) at 2,800 m (9,190 ft)) was installed, and the Ki-18 reached 444 km/h (276 mph) at 3,050 m (10,010 ft), climbing also at 5,000 m (16,400 ft) in 6 minutes 25.8 seconds, which the army delighted for.

However in the end, of the Akeno Army Flying School gave the Ki-18 a very high recommendation and pushed for its production, the Army Air Technical Research Institute still rejeted it as being a Navy design, vehemently ignoring the data and instead recommended a new competition with Nakajima, Kawasaki and Mitsubishi, and later cancelled as the Kawasaki K-10 just entered production since a year and replacement was estimated “too soon”. The petty bickering of the Army cost Japan a “common fighter” that would have been a better basis for future developments and less taxpayer’s waste overall. The Competition did took place and from it emerged the 1936 Nakajima Ki-27 (allied codename “Nate”), virtually a clone of the A5M, to the point at some point the US intel thought they were the same. Some 3,368 were produced, mostly based in China when WW2 broke out.

Ki-27 Shimada

The “early A5M”. After the rejection of the Ka-18, the Army made a new competition and chose the very similar Nakajima Ki-27 “Nate” (here the personal plane of the army ace Kenji Shimada, commander of the 1st Chutai of the 11th Sentai, Battle of Khalkin Gol June 1939).

About the Ki-33


Not being rebuffed by the rejection of the Ki-18, in the new competition ordered by the Army, pitting the three main Japanese manufacturers based on new army specifications for a monoplane fighter to replace the Kawasaki Ki-10 led in mid 1935 Kawasaki, Mitsubishi and Nakajima ordered for a prototype each. Mitsubishi’s Ki-33 by the time was busy setting up both production of the A5M fighter and G3M bomber and lacked the design capacity to develop abrand new figher. Even though the Ki-18 was rejected, the base design was retaken, with a main changes the Nakajima Ha-1-Ko engine rated at 555 kW (744 hp), and aft-sliding canopy, raised aft fuselage decking and modified vertical tail surfaces. Two were built, completed in June 1936, tested in November, until the spring of 1937, from which the Ki-27 emerged as the winner on grounds of agility.

Detailed specs

A5M4 1938

Crew: 1: Pilot
Fuselage Lenght 7.565 m (24 ft 10 in)
Wingspan 11 m (36 ft 1 in)
Wing area 17.8 m2 (192 sq ft)
Height 3.27 m (10 ft 9 in)
Airfoil type B-9 mod. (16%); tip: B-9 mod. (9%)
Empty weight: 1,216 kg (2,681 lb)
Max takeoff weight: 1,671 kg (3,684 lb)
Propeller: 3-bladed metal propeller
Engine: Nakajima Kotobuki 41 or 41 KAI 9-cylinder air-cooled radial 585 kW (785 hp) at 3,000 m (9,843 ft)
Top speed: 435 km/h (270 mph, 235 kn) at 3,000 m (9,843 ft)
Climb rate: 3,000 m (9,843 ft) in 3 minutes 35 seconds
Endurance: 1,201 km (746 mi, 648 nmi)
Service ceiling: 9,800 m (32,200 ft)
Wing Loading: 93.8 kg/m2 (19.2 lb/sq ft)
Power/mass: 0.3161 kW/kg (0.1923 hp/lb)
Armament 2× 7.7 mm (0.303 in) Type 97 MGs, 2×30 kg (66 Ibs) bombs
Other payloads 1x 160 l (42.27 US gal; 35.20 imp gal) drop-tank

The A5M in action

A5M 1, Kokutai 14, China, 1939 (src ww2 photos)

In July 1937, Japan started a second open war with China. Things went awhol since 1932 and the occupation of Mandchuria already, but when all-out war began, Naval aviation played a major role in early operations near Shanghai and along the shores. In 1937, the imperial fleet had four aircraft carriers in servce, with mixed air groups including at the time 12 air groups flying the A2N3, A2N4 and A4N1s. IJN Ryuiho, Shoho, and Kaga as IJN Akagi remained in drydock, ongoing a full modernization.

The very first sorties soon showed the old biplane fighters could not satisfactorily cope with the tasks assigned to them, despite adequate training, suffering significant losses. They were limited to 350 kph, while their Chinese Air Force opponents were in majority the American Curtis Hawk III, capable of 385 kph, giving them an edge in dogfights. They were especially deadly against slower Japanese bombers. The Japanese command was amazed that the heavier Hawk was designed and used as a fighter-bomber, still inferior to Japanese fighters in agility, but entirely compensating by speed. Especially when intercepting bombers, it became a determining factor. After the first reports came out, it became clear new monoplanes were urgently needed.

By the end of August, IJN Kaga was recommissiond and in Sasebo loaded her first two A5Ms, for testing in front-line conditions. On August 22, they made their first combat debut and met for the first time Chinese fighters on September 4. According to Japanese data they shot down three for no loss.

Chinese Curtiss Hawk III

Combat debuts over China (1937)

Type 96 Type 4’s ace pilots, IJN Akagi, 1937

Two other aicraft carriers went back to Sasebo, receiving a new air group and especially A5Ms. They returned into combat and gradually, the A5M arrived in larger numbers over China. The A5M1 quickly proved its superiority and gained for Japan air supremacy within a few months. On September 7 over Lake Tang, Captain Igarashi shot down three Hawks in a row. The A5M1 surpassed it by 50 kph. On September 9, the 13th squadron was transferred to the Kungta airfield (later to be camouflaged) and on the 15th, those carried by IJN Kaga were also transferred there.

From Kungta in September 19, a raid was condicted on Nanking, by then the capital of China, with 45 aircraft including twelve A5Ms from the 13th squadron, all equipped with droppable fuel tanks for the first time in combat conditions. Over Nanking, they encountered 23 Chinese fighters, Curtis but also Boeings and Italian Fiats. The Chinese lost seven and the Japanese four, but no A5M1.

The first losses took place on 21 September, from Hosho and Ryuho when attacking Canton. On the way back, short of gasoline, they splashed and sank. In the air, the first was shot down on October 12 when escorting nine bombers covered by 11 A5Ms. In aerial combat, the A5M1 demonstrated a significant advantage against all the best Chinese fighters of the day, the Curtis Hawk II/III and even the British Gladiators. The well trained pilots did wonders with this new fighter, and increased their tally quicky by the end of August, A5M1s shot down more than 330 Chinese aircraft (only 100 for the Chinese) for around 30 Mitsubishi A5M lost.

A5M and crew posing, unknwon aircraft carrier, circa 1938 (src warbirdphotographs.com)

As shown by NCO Kasimura, the A5M was light but still sturdy: In aerial combat, he collided with a Chinese Hawk, which fell on top of his A5M severing almost half its tail, but he still managed to made it to Shanghai. However at some point, Soviet pilots and their planes started to appear in the ranks of Chiang Kai-shek’s diverse air force. Formally considered, like the British and American “mercenaries”, as foreign volunteers. In reality they were regular personnel units from the Red Army Air Force, with careful selection and additional training. Theses units even retained their organizational structure, down to the mechanics and officers, and their combat effectiveness significantly exceeded the Chinese. Their I-15bis and I-16 fighters sson appeared as a match for the Japanese A5M, while extra planes and instructors started to benefit Chinese pilots as well.

The A5M2 found its match (1938)

Chinese Polikarpov I-15

The I-15 was superior in armament and survivability, notably due to the pilot’s armor protection. In dogfight, the A5M however still appeared superior. The first duel between the two models started on November 22, 1937, Captain G.M. Prokofiev leading six “ishaks” into a pack of six A5Ms, ending with one A5M down, pilot Miyazaki dead. Both sides significantly overestimated their victory numbers so estimating their respective performances is tricky at best. During the raid on Wuhan on January 18, 1938, 15 Japanese bombers escorted by 11 A5Ms were met by a force of 19 I-15bis and 10 I-16, the Japanese claiming 18, while the Soviet confirmed only 4 while insisting on 14 kill (5 for the Japanese). So this was even. Same, of even worse, on June 29 over Wuhan, in a raid of 18 G3M bombers escorted by 27 A5M fighters, met by 67 enemy fighters (including 25 soviet fighters with Chinese pilots), the Chinese claiming 11 kills for 11 losses of their own. The Japanese claimed to have shot down 51 fighters that day… for two losses.

Soviet pilots considered in their reports the A5M as a serious and worthy adversary. The Chinese Tupolev SB bomber were easily dealt for by the old A4Ns of the fleet, as well as the Ki.10 army fighters. The A5M was used as a fighter interceptor, in a pure air superiority role, in which it still excelled. On the 13 January 1938, thirteen SB led by F.P. Polynin were intercepted by A4N1s, which could not stop them, and the Soviets destroyed the aifield as planned, but they were met when returning by accurate anti-aircraft guns, finished off by eight A5Ms. To escape the onloaught, after two SBs went down, they tried to climb to 6000-7000 m.

The first damaged, crash-landed A5Ms also became trophies of the Chinese army, one being tested by the Chinese, but apparently no reports were sent to the Americans. Two were repaired and sent to the USSR, bu were apparently sabotaged by Japanese agents whle en route, with sugar was poured into the gas tanks.

The A5M2 in combat (1939)

IJN Akagi’s A5M in flight over China, 1937

On October 28, 1938 the soviets started to test intensively one A5M2-Otsu at the Air Force Research Institute and it was soon found it did not work well in the Russian cold and satisfactory tests only started in the spring of 1939 with a first flight on May 13. It had excellent results in stability, maneuverability and was easy to fly, but according to soviet data, still lacked in some maneuverability spheres and in armament, rated lower than the new Soviet fighters in the end. By mid-1939 however the A5M was outdated and Mitsubishi to the point of delivering its legendary A6M.

However the Soviet industry copied some of its features and design solutions like the convenient of the battery in a special container, a compact and reliable Japanese voltammeter, ultraviolet illumination for the dashboard. Later, crucially, the A5M was not present at Khalkhin Gol, but the Ki.27 (“Nate”) instead, about the same type for the Army.

In China, the A5M2 and 3 went on in active combat units in 1939, 1940 and 1941, as long as they were not replaced by more recent models, prioritized for Pacific Operations. The Imperial Japanese Navy used it increasingly on land bases, and by mid-1941, all frontline aicraft deck-based units were supposed to have transitioned. Still, the A5M persisted due to the need to acquire combat experience in a large range of naval aircraft and the nature of the Chinese front. After September 1939, foreign delveries to China marked a step and only went worse in 1940, so oppostion soon dwindled down, making the A5M still relevant on this theater for many years.

At the time, the main IJN aviation base was located in Hankou, and A5Ms were mostly relegated to shore patrols, covering airfields and ports, and escorting bombers inland to some point. In interior China, there were many Japanese Army airfield that took the bulk of operations. By the start of 1940, two IJN air groups operated in China, the 2nd and 3rd Kokutai including more than 50 A5Ms while aircraft carriers retained them as primary fighter off the coast since the end of 1938.

Combat debut of the A5M4

Japanese ace Kashimura’s personal A5M4 in flight, 9 December 1937

The A5M4 production started at the end of 1938 and arrived in active units in China in early 1939. Still was very close to the A5M2-Otsu, it had a new visor in the cockpit, and a powerful radio among other details. Moreover, it was equipped with the new “Kotobuki” 41 engine, delivering 785hp. With new underwing suspended tanks with greater capacity, its range jumped to 648 km. In parallel with the A5M4 the training two-seater A5M4-K was also produced, with an instructor’s seat and cockpit located behind the main one, both open. The Nakajima plant in Nagoya ceased production in 1940 and Omur took charge of the rest of the production, mostly the A5M4-K and even a few at Watanabe Tekkose until 1941. At the end of the 1941, the Japanese acquired bases in Indochina and soon the 14th squadron, equipped with the A5M4 arrived there. From there, raids against Kunming in southern China commenced.

By mid-1941 the 12th and 14th air detachments (Kokutai) as well new aircraft carriers like the Shokaku class were completely re-equipped with the new A6M. A5Ms were transferred to local air defense units of coastal bases and training units.

The Mitsubishi A5M in WW2

IJN ace Mitsugu Mori (9 victories), china 1938, 12th naval air Group By December 1941, the IJN listed only 193 A5Ms in active service, of which 144 were in second line home islands bases, deployed to provide air cover for local defense, above the naval bases in Sasebo, Omura, Ominato and Takao. However a “special air group” was mustered by the fleet to participate in the invasion of Malaya, where local air opposition was judged weak, and squadrons deployed on light aircraft carriers Soho (11 A5M), Ryuho (22), Zuiho (16). US intel assigned the A5M4 the codename “Claude”. IJN Ryuiho’s fighters (Rear Admiral Kakuji, 4th Aircraft Carrier Division) covered the landing in the Philippines as well, in the Davao region and Mindanao, that the A6M stationed in Taiwan could not reach. Ryuiho’s A5M4s also soldiered in the Dutch East Indies. By February-March 1942 Ryuyho also made strikes in the Bay of Bengal.

Soon Japanese coquest needed protection and airfields, either captured or create needed extra fighters, the best ones (A6Ms) being reserved fir the Navy. So air cover was needed, and the hastily newly formed air defense units were provided stock A5Ms: The 4th squadron in Rabaul, 1st and 6th in the Marshall Islands (Luoti, Taloa and Palau airfields) were equipped with the “Claude”. They were still actively used until April 1942, after which A6M were in suffocent numbers to be detached in these Navy bases. Some local airfield, such as Buin Island, retained their A5M well until September 1943.

Japan local defence airfield were considered too far from the front to be equipped with modern fighters and ficused instead of training or carrying out local uneventful patrols, until at least in April 1942, bombers from the Dolittle raid striking the Tokyo area were nearly intercepted by three A5M4s from the Kasumigaura squadron, patrolling nearby, but at the time, they failed to identify the American planes, assuming these were Japanese.

The last pacific battles

The A5M took part in the battle in the Coral Sea, on May 7, 1942: Two A5Ms and four A6Ms flew from IJN Soho as a CAP (the escort fighters sent in attack were all A6Ms). They interecpted dive and torpedo bombers of from Yorktown and Lexington and managed to shot down three, but their carrier was hist and sunk in 20 minutes. Having nowhere to land -they splashed although one A5M4 managed to crash land on nearest island. On July 14, 1942 the auxiliary aircraft carrier “Kasuga Maru” (a rebuilt liner transformed as an assault ship) had onboard 11 A6M and 14 A5Ms.

By the end of 1942, all A5M units in the home islands were now relegated to training units and flight schools. By the end of 1944, A5M4 and A5M4-K were still in number, althugh by that point, worn-out machines versed into kamikaze detachments with bomb suspended under the fuselage. They saw action off the coast of Japan and especially over Iwo Jima in early 1945.


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Taylor, Michael J. H. (1989). Jane’s Encyclopedia of Aviation. London: Studio Editions.
Bond, Charles R.; Anderson, Terry H. (1984). A Flying Tiger’s Diary. College Station, Texas: Texas A&M University.
Francillon, Ph.D., René J. Japanese Aircraft of the Pacific War. London: Putnam & Company Ltd., 1970 (second edition 1979).
Green, William (1961). Warplanes of the Second World War, Volume 3 Macdonald & Co.
Green, William; Swanborough, Gordon “The Zero Precursor, Mitsubishi’s A5M”. Air Enthusiast. No. 19.
Januszewski, Tadeusz (2003). Mitsubishi A5M Claude. Sandomierz, Poland/Redbourn Mushroom Model Publications.
Mikesh, Robert C.; Abe, Shorzoe (1990). Japanese Aircraft, 1910-1941. Putnam Aeronautical.
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The A5M on airwar.ru
A Flying Tiger’s diary, by Bond, Charles R; Anderson, Terry H., 1946
On militaryfactory.com
On historyofwar.org
Japanese Aircraft of World War II (Technical Guides): 1937–1945
A5M claude by Dariusz Paduch on kagero.pl
On combinedfleet.com
On aviastar.org
On scalemates.com

Mitsubishi KA-14, the very first inverted gull wing prototype, 1935. Six were built and modified (from the second one).

Mitsubishi Ki-18, land-based version for Army with a 410 kW (550 hp) Kotobuki 5 engine.

Mitsubishi Ki-33, two prototypes for the Army with a new engine and modified cockpit.

Mitsubishi A5M3a prototype with the 448 kW (601 hp) Hispano-Suiza 12 Xcrs engine

Mitsubishi A5M1 Kashimura China 1937

Mitsubishi A5M1 Buntai China 1937

Mitsubishi A5M1 PO3c, Shanghai China March 1938

Mitsubishi A5M1 POC3c Nanchang July 1938

Mitsubishi A5M2a late 12th Kokutai, 1939

Mitsubishi A5M2b, 12th Kokutai (captured in China, 1939)

Mitsubishi A5M2b early type, Hyawata Kokutai Ibaraki 1940

Mitsubishi A5M2a late 12th Kokutai, 1939

Mitsubishi A5M2b late type, 14th Kokutai (captured)

Mitsubishi A5M2b, 14th Kokutai 1939

Mitsubishi A5M4, IJN Soryu 1940

Mitsubishi A5M4, IJN Soryu 1941

Mitsubishi A5M4, IJN Zuiho February 1942

A5M2b, 4th Tainan Kokutai Lakunai Air Base New Britain April 1942

A5M4 14th Kokutai Haiku Air Base South China October 1940

A5M4 381 Kokutai Tebrau Malaysia 1945

A5M4 Ota 116, Omurai Kokutai, Nagasaki August 1945

Mitsubishi A5M4 single seat advanced trainer, Kasumigaura Kojutai, Japan 1944


A5M Claude Kokutai ?

A5M4 Hosho early 1942

A5M2b 113-2

A5M2b 3-165

A5M4 green

A5M4 Used for training

A5M4 green

A5M “Claude”

A5M4 12th Kokutai



Aichi D1A (1934)

Aichi D1A “Susie” (1934)

Imperial Japanese Navy, 590 built

The last IJN biplane dive bomber

The Aichi D1A/D2A “Susie” was a reliable, modern dive bomber biplane in service with the IJN from 1935 to 1940 (1942 with Mandchukuo). It was the direct predecessor of the D3A “Val” monoplane of WW2 fame, and still served in many units in China while replaced in the fleet from 1940. Two models were developed, the D1A1 and D1A2, mostly used in China.

About Aichi Kokuki KK

The first Aichi soon confounded with dive bombers, notaly its D3A “Val” for WW2 fame. The company Aichi Kōkūki Kabushiki Kaisha (愛知航空機株式会社) or Aichi Aircraft Co., Ltd, was founded in 1898 and started as a small crafts specialist, Watch and Electric Manufacturing Co., Ltd. It turned to aviation in 1920, and without expertise but only ambitions in this field, turned to the German manufacturer Heinkel in 1923, relying initially on heavy technical assistance from that company to eventually give birth to its first model, the Type H Carrier Fighter in 1926, a carrier-based floatplane fighter, and license-built Heinkel HD 23. In 1928 came its first bomber biplane, the 1928 AB-1. Soo also, the company started prospecting for Navy Contracts, and provided a vast sways of floatplanes and convertibles, notably the 1930 Aichi E8A, the floatplanes E12A and E13A, and its first dive bomber, the Aichi D1A and its derivative, the D2A, leading later to the excellent monoplane D3A. Alongside it also developed torpedo bombers like the WW2 B7A and B8A, or special service submarine-launched M6A Seiran. The company also developed aircraft engines, notably radials but also inline, like the Aichi Atsuta derived from the Daimler-Benz DB 601A inverted V12. The company was reorganized in civilian prduction, notably cars after 1945 and still exist today, now integrated into Nissan.

Heinkel He 50 (1932)

Development of the D1A

The D1A came out of the IJN need for an advanced carrier borne dive bomber. In 1932, Aichi answered such query from the Navy, with the AB-8 (internal designation related to biplanes), a carrier-based attack bomber prototype which competed -and lost- to the Kugisho B3Y. With rapid advances in aircraft technologies, Aichi not to be undone proposed a modified version of the AB-9 for the 1934 competition. Therefore the company prototype denominated AB-9 first flew that year, not designed by Aichi, but Ernst Heinkel Flugzeugwerke at the company request, searching for a more advanced model, partly in metal and with a superior speed and payload.

Aichi D1A1

Heinkel found interest in this request as forbidden to develop military planes in Germany according to the treaty of Versailles, and sent specialists in Japan, with engineers, blueprints and even parts in order to create the prototype Aichi wanted to present. This version designed by Heinkel was the He 50 developed from 1931 so in secret, and which in Germany was used as a patrol floatplane instead of a landing gear model. The model was only built and introduced into service as a dive bomber after Hitler arrived in power, also exported to China and used by Spain during the civil war.

The specific Japanese prototype was the He 50b, third prototype also designated HE 66 for export to Japan, with three more completed for German evaluation. All were powered by the same 373 kW (600 hp) Bramo 322B radial. These led to the He 50A, main production version later replaced by the Stuka. Pragrmatic, Aichi immediately started copying in detail the He 66 which was finalized rapidly as the prototype.

It won the IJN competition and the latter ordered the finalisation of design, produced as the D1A1 under navy aviation ordnance designation (Last letter for Aichi, D for “dive bomber”, first model). Production was geared up, still with German assistance the same year and deliveries started in 1935, after which the model started to replace older bombers in service on all service aircraft cariers of the time: Kaga, Akagi, Ryujo, and the completing Soryu. In all, Aichi would deliver 162 D1A and 428 of the improved D1A2 until 1938, when replaced by the new D3A monoplane.


The design of the D1A was based on the Heinkel He 66, a two-bay biplane constructed of metal with fabric covering. The braced tail unit was conventional, and landing gear of fixed tailskid type. It had a purposedly reinforced fixed landing gear, and conventional type tail landing skid. It was not at first equipped for carrier operations. The D1A was given initially a Siemens SAM-22B (Jupiter VI) radial engine and was somewhat underpowered. The production version D1A1 was given the 418kW Nakajima Kotobuki 2 Kai 1 radial engine. The D1A2 was given an even more powerful Mitsubishi engine. The Navy Type 94 Carrier Bomber Aichi D1A1 production version had its radial engine enclosed by a Townend ring, the introduction of slightly swept wings, replacement of the tailskid by a non-castoring tailwheel. Also in the 162 delivered, the last 44 were given the 433kW Kotobuki 3 engine.

The construction was a radical departure over previous Aichi models, all-metal framing with reinforced fabric covering which ensured greater strenght. The end result was a sturdy airplane, able to rought landing on a carrier (to some extent), and dive bombing, subjecting the structure to extreme stress. With a relatively bulky radial engine it was not going to achieve speed records but had a good endurance and agility. The great letdown was its lack of usability on carriers with non-folding wings and still a wheeltrain relatively weak as well as no tailhook on initial models.

Specifics of the D1A2 (*D2A) (1936):

Basically the same model, the Navy Type 96 Carrier Bomber) appeared in 1936-37. It was 30′ 10″ (9.4 m) long, 11′ 2.7″ (3.45 m) high, with a wingspan of 37′ 3.6″ (11.37 m) and a Wing area of 366.51 sq. ft (34.05 sq. m) which were unchanged, but its empty weight of 3086 lbs (1400 kg) and loaded weight of 5291 lbs (2400 kg). Its main external difference were spatted wheels, NACA engine cowling, and improved windscreen. It was also faster and more powerful with a higher powered Nakajima Hikari 1 engine. The machine guns were replaced by two Type 99.


Armament was limited to two fixed machine guns in the nose, of the standard Japanese 7.7 mm (.303 in) Type 92 machine guns with an interruptor gear mechanism. There was a thord one on a flexible mount aft, for defence. The payload carried was important in 1934, with a single 250 kg (551 lb) bomb under fuselage, and main purpose of the plane, and two 30 kg (66 lb) bombs under wings.


The D1A was given the 365 kW (490 hp)copy by Aichi of the 373 kW (600 hp) Bramo 322B radial. The D2A, main production version was given the 433 kW (580 hp) Nakajima Hikari 1, a 9-cylinder air-cooled radial piston unit capable of delivering 540 kW (730 hp) for take-off. Its nomal output was 500 kW (670 hp) at 3,500 m (11,500 ft). It was mated to a 2-bladed metal propeller. It had a wing area of 34.7 m2 (374 sq ft) and a maximum takeoff weight of 2,610 kg (5,754 lb).

Performance wise, it was capable of 309 km/h (192 mph, 167 kn) at 3,200 m (10,500 ft) and a range of 926 km (575 mi, 500 nmi). Its cruise speed was 222 km/h (138 mph, 120 kn) at 1,000 m (3,300 ft) and it service ceiling of 6,980 m (22,900 ft) with a time to altitude of 3,000 m (9,800 ft) in 7 minutes 51 seconds.

Detailed specs

D1A2 1936

Crew: One pilot
Fuselage Lenght 9.3 m (30 ft 6 in)
Wingspan 11.4 m (37 ft 5 in)
Height 3.41 m (11 ft 2 in)
Empty weight: 1,516 kg (3,342 lb)
Gross weight: 2,500 kg (5,512 lb)
Powerplant: Mitsubishi Hikari 1 Engine, 433 kW (380 hp)
Propellers: 2-bladed fixed-pitch metal propeller
Maximum speed: 309 km/h (192 mph, 167 kn)
Endurance: 926 km (575 mi, 500 nmi)
Service ceiling: 7,000 m (23,000 ft)
Time to altitude: 3,000 m (9,843 ft) in 10 minutes
Power/mass: 0.18 kW/kg (0.11 hp/lb)
Armament 3 × 7.7 mm MGs, 250 kgs bombs


BA-9: Initial prototype derived from the He 66.
D1A1: Initial production version with unfaired carriage and 365 kW engine.
D1A2: Final production version with faired carriage, 433 kW engine.
D2A: Same model, alternative designation.
AB-11: Proposed retractable undercarriage version, paper project.

The D1A/D2A in service

In the IJN

Without a proper structural integrity for a tail hook to perform hard carrier landings, the D2A was only tested on carriers before being versed in Imperial Japanese Army airfields. It was assigned at first to the Carriers IJN Akagi, Kaga and Ryujo only, in detail, the 12th, 13th, 14th and 15th Kokutais. It is reportdly also in service on Hiryu and Soryu until replacement by the D3A, likely in 1940. But it was not practical and gradually retired from the Kido Butai and sent to China.

In China

It was tasked in China (caouflaged or painted khaki) to destroy numerous ground targets in Manchuria and seemed successful in this task. Their limited defensive capability imposed the use of fighters to repel Chinese attackers. After campaiging in the rest of China, the D2A was gradually retired and it ceased all activity in 1940 in first line, although the model was allegedly completely retired only in 1942. D1A1s however remained in use with training units in December 1941. About 70 D1A2s also were kept in second-line units in China, so allied intel had to find for them a classification codename which was ‘Susie’. She was rarely encountered during the war, but perhaps by the “flying tigers” in 1941. In 1942, only those in service with Mandchukuo were still active.

In 1937 D1As from Ryujo’s were implicated with the USS Panay incident, which happened during the Japanese all-out attack on Shanghai and the Yangtse.

In service with Mandchukuo

Already seen in the dedicated sub about Mandchukuo in WW2, the puppet country reprsented by Pu Yi, last Emperor of China but under Japanese supervision had a limited force (Manchukuo Imperial Navy Air Force) notably composed of two squadrons of Aichi D1A biplanes.


IJN Aviation
Naval aviation
Wiki page
On wings palette
On daveswarbirds.com

Aichi D1A1 based on land, Kyushu 1935 – built by public subscription.

D1A2 in China 1937

A2 on IJN Kaga, 1937

A2 based in China, Autumn 1937

D1A2 based in Nagasaki, early 1941.

Aichi D1A2 Mandchukuo Coast Guard, 1943

Ryujo’s D1A2 in flight off China, 1935

D1A2 in formation flight over China 1936, camouflaged in khaki

Various photos of the D1A2 in China 1937-40

Nakajima A4N (1935)

Nakajima A4N (1932)

IJN aviation Imperial Japanese Navy, 148 built

The 1930s IJN naval fighter

The Nakajima A4N was a carrier-based fighter, last biplane by Nakajima. The first prototype was completed in 1934, but engine issues delayed the entry service until 1936. It was internally called Nakajima YM (factory designation), or Navy Type 95 Carrier Fighter. In all, 221 were built, mostly active during the Chinese War and until its replacement in 1937-38 by the Mitsubishi A5M.

Type 95 Shiki Kansen

The precedessor: Nakajima A2N

Type 95 Siki Kansen

The A2N was developed as a private venture by Nakajima, intended to fill the carrier-borne fighter niche in 1929. It was based loosely on the Boeing Model 69 and 100, both imported a year before and the same for technical analysis and evaluation. Takao Yoshida was chief designer of the project and created two prototypes: One was designated Navy Type 90 Carrier Fighter (in anticipation of Navy trials, outside specifications). It was ready in December 1929, Powered by a Bristol Jupiter VI engine under licence.

The Navy tested it, but it was rejected as not offering much advantage over the existing Nakajima A1N. The latter was indeed a copy of the British Gloster Gambet, which prototype first flew on 12 December 1927, introduced in early 1929 in active units, and which production was ongoing (151 were delivered). They already equipped IJN Hosho, Kaga and Akagi. But the IJN had an ambitious program of new “sub-treaty” light aircraft carriers, and IJN Ryujo was one of these. Nakajima, like its competitor Mitsubishi knew they would be a greater need for fighters in the near future.

4-view blueprint of the A2N

After the refusal, Jingo Kurihara started a major redesign, leading to the creation in 1930 of another prototype, the Type 91 or A2N1, powered by the improved 432 kW (579 hp) Nakajima Kotobuki 2 engine. It was completed in May 1931 and trialled this year extensively. This time the naval staff was impressed by its performances and accepted it in April 1932 for service. 100 were ordered (the most common number given), bbut the company started to work on the next iteration, believing it had now secured the IJN fighter market for years. The production run went on in 1936 with a two-seat trainer called the A3N3-1, with 66 built until 1939 as advanced trainer for the next A2N.

  • A2N1 (Navy Type 90-I Carrier Fighter) Guns located in both sides of the nose, but few produced.
  • A2N2 (Type 90-II) – Guns transferred to the upper surface of the nose, the fuel tanks mounted on the fuselage sides.
  • A2N3 (Type 90-III) – principal production variant. 5° of dihedral on upper mainplane.
  • A3N3-1 (Navy Type 90 training fighter) two-seat trainer: 66 built 1936-39.

The A2N In Combat

In 1932, Minoru Genda, later famous for its constribition to the attack at Pearl Harbor, formed a flight demonstration team. It was called the “Genda’s Flying Circus”, and was used to promote naval aviation. He flew the A2N all across the country, creating vocations in the youth, some of these ending as kamikaze in 1944-45. The Type 90 Carrier-based fighter was as planned the main fighter of IJN Hōshō, Kaga and Ryūjō, replacing completely the Mitsubishi 1MF. The A2N was also of course deployed in China, taking part in the Mandchurian incident and northern air force patrols, and the first air battles of the Second Sino-Japanese War in 1937. However production ceased in 1936 and the type ws considered already obsolescent. Mitsubishi notably already worked on a new monoplane, more promising. Air-combat units flew the A2N in many high-profil operations such as Japanese troop-landings in the Battle of Shanghai (16 August 1937), where Akio Matsuba from Kaga shot-down a Chinese Douglas O-2M, followed by many other victories. The first aces of the IJN were A1N pilots, but the model by that time was already uperseded by the A4N, and soon the A5M as well.

Brief specs:

6.183 x 3.025 m, wingspan: 9.37 m (30 ft 9 in), weight 1,045 kg/1,550 kg (3,417 lb), Powerplant Nakajima Kotobuki 2 9-cylinder air-cooled radial piston engine 343–433 kW (460–580 hp) with a 2-bladed Hamilton Standard fixed-pitch metal propeller. Top speed 293 km/h (182 mph, 158 kn), cruise 167 km/h, Range 500 km (310 mi, 270 nmi), ceiling: 9,000 m (30,000 ft), climb rate 3,000 m (9,843 ft)/5 minutes. It was armed with two fixed forward firing 7.7 mm (0.303 in) machine guns but carried no other payload.

Development of the Nakajima A4N

4-view blueprint of the A4N

The Imperial Japanese Navy developed official requirements for a new “9-Shi specification” carrier-based aircraft one of these being a fighter, in order to replace the main Nakajima A2N. In February 1934 this specification was issued to Mitsubishi while instructing Nakajima to modernize its A2N. Takao Yoshida and Shinobu Miyake took the head of the new design team. The first prototype called Nakajima YM flew for the first time in October 1934, and flew in early 1935. There was an hypothetic A3N in 1933, but the model was never developed further.

The first tests revealed a top speed of 352 km/h at 3,200 m, matching the official specification. However on February 1, 1935, Mitsubishi presented its Ka-14 prototype, forerunner of its future A5M? Inspired by the Boeing P26, it first flew that day. The Navy was faced with two fighters of similar performances, one monoplane, the other biplane, and there were two school of thoughts about them. Some believed the monoplane was not a viable solution and just a fad. So the two companies stuck to their guns and defended their “baby”.

At last, the Navy made comparative tests, by selected combat pilots. The end result was that the Mitsubishi prototype had a better high speed, Nakajima better maneuverability. This just confirmed the general opinion about monoplanes versus biplane worldwide at the time. Soon, the Navy realized it could have both fighters, one reserved for escort and dogfights, the other as interceptor, and given the planned construction of two new carriers, replacing existing parks and limited production capacity of both manufacturers, started to discuss about the possibility to have both models accepted.

Further tests took place at the end of 1935 conducted by Lieutenant Minoru Genda and Lieutenant Ryosuke Nomura, plus other selected, high profile pilots. Since they were celebrities at the time, this new test took almost a public importance. A more extensive palette of tests was performed, and according to the results the Nakajima fighter won, notably due to its superiority in a popular aerobatic tactic at the time, the so-called “dog dump”. The Navy however did not sidelined the A5M for long as it would came back soon, with the needs of the 1937 war. The first production fighter was designated A4N1, and classified in the Navy ordnance as the “Type 95 carrier-based fleet fighter.”


The new A4N was similar to the A2N, but still with important differences. Dimensions of the airframe were slightly larger, the engine was a more powerful Nakajima Hikari 1 capable of 730 hp with 600 liters of capacity. The single-bay chassis was redesigned, with split struts combined for better stiffness and increasing rigidity. Also a tailwheel was added for better control on the ground. To increase the range, suspended tanks were installed under the left or right wing. They allowed the A4N to reach 950-980 km, but generally capped to 845 km with a reserve for dogfighting. Armament comprised two Type 97 7.7 (0.3 inches) machine guns and the power to weight ratio was now positive to such point, the wings were reinforced to carry a limited bomb load, up to 120 kg (either the standard light 30 kg or heavier 60 kg models).

Nakajima Kobuki 1 engine



Nakajima Hikari 1 9-cylinder air-cooled radial piston engine, 500 kW (670 hp) to 544 kW (730 hp). A classic star engine, long developed for the Kobuki and a British model, but modified along the lines of the Wright used in Boign models, and a lot of local modifications to improve its performances. This was a sturdy engine, which equipped most IJN models: The Aichi D1A2 and D3A prototype, Kawasaki Ki-45 prototype, Mitsubishi F1M1, Nakajima B5N1, C3N and Yokosuka B4Y1. The Hikari 1 developed 820 hp (610 kW) which was considerable in 1935, but the Hikari 1 kai was pushed to 730 hp (540 kW), the Hikari 2 up to 840 hp (630 kW) and the more tamed Hikari 3 offered 770 hp (570 kW).


Two fixed, forward-firing 7.7 mm (0.8 inches) Type 97 machine guns. Two 30 kg (66 Ibs.) or two 60 kg (132 Ibs.) bombs underwings.

Detailed specs

A4N1 1931

Crew: One pilot
Fuselage Lenght 6.64 m (21 ft 9 in)
Wingspan 10 m (32 ft 10 in)
Height 3.07 m (10 ft 1 in)
Wing Area 22.89 m2 (246.4 sq ft), load 76.9 kg/m2 (15.8 lb/sq ft)
Empty weight: 1,276 kg (2,813 lb)
Gross weight: 1,760 kg (3,880 lb)
Powerplant: Nakajima Hikari 1 9-cyl. 670-730 hp (500-544 kW)
Propellers: 2-bladed Hamilton fixed-pitch metal propeller
Maximum speed: 352 km/h (219 mph, 190 kn) at 3,200 m (10,499 ft)
Service ceiling: 7,740 m (25,390 ft)
Range: 846 km (526 mi, 457 nmi)
Time to altitude: 3,000 m (9,843 ft) in 3 minutes 30 seconds
Power/mass: 0.2884 kW/kg (0.1754 hp/lb)
Armament 2x 7.7 mm LMGs, 2×30/60 kgs bombs

The A4 in action

A4Ns in formation in China, 1937 (world of warships)

However, the service of this biplane was short-lived, since the leadership of the Imperial Navy was convinced of the superiority of monoplanes over biplanes. The tactics of using the A5M high-speed monoplane proved the unconditional advantages of this scheme in fighter aircraft, but the rearmament was carried out for a very long time. By the beginning of the Sino-Japanese War, as part of the naval aviation, only the 12th mixed kokutai (Luda airfield, Dairen) had 12 A4N fighters in its composition. The functions were short-range escort operations and air defense.

The first battles were unsuccessful: on August 24, 1937, the commander of the 24th Fighter Squadron of the Air Force of the Republic of China, Captain Liu Chuikang, in a Curtiss Hawk III fighter shot down an A4N northwest of Shanghai, and the pilot was killed. On August 25, the Japanese from the aircraft carrier “Hosho” tried to intercept He-111A bombers, damaging two bombers. In August, the 12th Kokutai went on vacation, but returned to service on September 5 as part of the 3rd Fleet, stationed at Kunda Air Base (Shanghai), and joined the support of the ground forces. A4Ns also became stormtroopers. The losses intensified: on September 18, the plane of senior lieutenant Kazue Sato was shot down in the Baoding area by air defense forces, and the captain, having made an emergency landing, was killed in a firefight. In October-November, the fighters began to be replaced by Mitsubishi monoplanes. Since December 1937, the Kanoya kokutai began to operate in the Shanghai area, which had the A4N daitai (squadron), but they were only engaged in air defense. A4N have become only a tool to make up for losses.

On April 13, 1938, the aircraft carrier “Kaga”, having several A4N fighters in its air group, supported the attacks on Canton, and that day at least one A4N fighter was shot down: Lieutenant Teng Chunkai from the 28th squadron distinguished himself about two aircraft shot down, but the second was the Aichi D1A deck bomber. Lieutenant Kwan Yensun reported another A4N shot down and two injured. In response, two Japanese shot down two Gloster Gladiator fighters: Chief of the 2nd class Hatsuo Hidaka (pilot U Bojun died) and Chief Petty Officer Chono distinguished themselves. On April 25, 1938, the air group of the Soryu aircraft carrier (Nanjing airport) joined the hostilities, and in June the 15th kokutai with old aircraft was also abandoned. The reason for such a massive inclusion of the Nakajima A4N in the battle was the large losses in aircraft. On July 16, Chinese Air Force bombers launched a bombardment of the airfield, and the 15th Kokutai repelled the attack, shooting down three planes. Chief Petty Officer Ichiro Higayashima and Petty Officer 2nd Class Yoshiharu Matsumoto distinguished themselves.

In March, the Kanoya Kokutai withdrew the A4N, in April the Soryu and Kaga aircraft carriers withdrew their aircraft, and in September 1938 the 15th Kokutai abandoned them as well. For a short time, the aircraft was based on the Ryujo aircraft carrier as a training aircraft. By the end of 1938, it was gone in combat units: all Nakajima A4Ns became training ones.



Green, William; Swanborough, Gordon (1994). The Complete Book of Fighters. New York: Smithmark.
Mikesh, Robert C.; Abe, Shorzoe (1990). Japanese Aircraft, 1910-1941. London: Putnam Aeronautical Books.
Passingham, Malcolm (November 1995). “Les premiers chasseurs embarqués Nakajima (2e partie): Le A2N Type 90”
Gustavsson, Hakans. “Håkans Aviation page – Sino-Japanese Air War 1937”. Biplane Fighter Aces – China.
Sun, Lianggang. “Shanghai 1937 – Where World War II Began”. SHANGHAI 1937: WHERE WORLD WAR II STARTED.
Gustavsson, Hakans. “Japanese biplane fighter aces – Akio Matsuba”. Biplane Fighter Aces – Japan.

The initial prototype tested in 1934.

AKN-1 IJN Akagi, 1936

A4N1, 12th Kokutai 1936

12th Kokutai, Shanghai August 1937

Unknown unit, China winter 1937/38


Nakajima Type 97 650 hp engine

The 1937 Panay incident, where A4Ns were involved in