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A6M Zero Fighter Plane

A6M Zero Fighter Plane

Find out how the world's first strategic fighter plane, the Mitsubishi A6M Zero, allowed the Japanese to achieve air superiority in World War II, at least until the Allied planes came along.


A6M Zero Fighter Plane - HISTORY

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The Agile A6M Zero

The Successor to the A5M with Ambitious Specifications

When the Imperial Japanese Army challenged Mitsubishi and Nakajima to design and build successors to the A5M plane to aid the war effort in China, the specifications were so ambitious that Nakajima pulled out of the bid leaving chief designer Jiro Horikoshi to assemble a team.

The new plane was to have a top speed of 500 km/hr, be fitted with two 7 mm machine guns, two 20 mm cannons, be capable of flying 2 hours at max speed and 6–8 hours at crushing speed with drop tanks attached. The plane also needed to be carrier based (capable of flying off an aircraft carrier) which limited its wing span.

Horikoshi set about designing the Zero with this specification in mind. His goals were to make the new aircraft as maneuverable as possible and to provide it with a range capable of escorting Japanese bombers to China and back. Horikoshi knew that key to this was making the fighter as lightweight as possible.

Design changes included a one-metre shortening of the main wings from 12 to 11 metres, and incorporated many of the most advanced techniques of the era. Thin elliptical wings minimized drag along with state-of the art flush riveting. New heat treatment knowledge obtained from the Germans allowed Horikoshi to develop an all metal structure, its frame entirely made from this new age hardened aluminium and he cut holes into the frame where possible to reduce weight.

Its skin was only 1.2 mm thick over its thickest sections like the leading edge of the wing, to 0.5 mm thick over the thinnest sections at the aft of the plane.

The engine was located close to a smaller cockpit which helped to save weight, but also made the Zero more manoeuvrable. The Zero design team used an engine that made around 300 horsepower less than the Pratt & Whitney R-1840 Twin Wasp powering the F4F-4 Wildcat. Newer American fighters more than doubled the Zero’s horsepower with a commensurate increase in wing loading and performance. However, less wing loading meant quicker maneuvering.

As the war progressed, the Zero continued to operate without significant improvements, suggesting that Horikoshi’s team had extracted all possible performance from the Zero design.

Eventually, it was improvements in American tactics and technology that resulted in the rapid loss of many Zeros and their pilots. The absence of protective equipment – armor plate and self-sealing fuel tanks – that had allowed the Zero to be so agile in combat exposed a weakness that the Americans were able to exploit.

From 1939 – 1945: A6M1 to A6M8

A: carrier fighter (capable of flying off an aircraft carrier)
6: the sixth carrier fighter ordered
M: Mitsubishi
52: model variant

A6M1
Special attention was paid to weight savings, and a new special aluminium alloy developed by Sumimoto was adopted. Powered by a Mitsubishi Zuisei 13 (Auspicious Star) fourteen-cylinder, twin-row air-cooled radial engine, rated at 780 hp for take off and 875 hp at 11,810 feet.
Two 7.7 mm Type 97 machine guns in the upper fuselage decking
Two wing-mounted 20-mm Type 99 cannon
Three-bladed constant speed propeller
Speed was 305 mph at 12,470 feet – slightly below requirement

A6M2
Re-engineered with a Nakajima NK1C Sakae 12 (Prosperity) engine
Manually upward-folding wingtips (about 20 inches long) were incorporated so that the plane could fit the deck elevators of the Imperial Navy’s aircraft carriers. This modification resulted in a change of designation to Navy Type 0 Carrier Fighter Model 21.

During the first year of the Pacific War, the standard shipboard fighter serving with the US Navy was the Grumman F4F Wildcat. The A6M2 was superior to the F4F Wildcat in speed, climb rate, and maneuverability, but the Wildcat had better firepower and was more robust. In a dive the two aircraft were fairly equal, but the turning circle of the Zero Fighter was very much smaller than that of the Wildcat by virtue of its lower wing loadings.

A6M2-N “Rufe”
A seaplane adaptation of the Mitsubishi A6M2 Zero Fighter
The A6M2 Model 11 with the non-folding wingtips was used as the basis.
The retractable landing gear was removed and the wheel wells were faired over. A large central float was mounted and two stabilizing cantilever floats were fitted underneath the outboard wings.

A6M3”Hap”
Powered by a 1130 hp Sakae 21 equipped with a two-speed supercharger instead of a single-speed unit as used on the earlier Sakae 12.

The ammunition supply for the wing-mounted 20-mm cannon was increased from 60 rpg to 100 rpg. In order to simplify production and maintenance, the folding wingtips and the tab balances were removed, reducing the wingspan to 36 feet 1 1/16 inches and wing area to 231.75 square feet. This resulted in a slight increase in the level speed with little adverse effect in the overall maneuverability. Japanese pilots did find that both the maneuverability and climb rate of the new clipped-wing Zero Fighter were slightly poorer than those of the earlier A6M2, but the aircraft was considerably faster in a dive, the ailerons were more effective, and the roll rate was better at high speed.

A6M4
Modified to take an experimental turbo supercharged Sakae engine. However, major teething troubles were encountered with the A6M4, and no production order was placed.

A6M5
The converted A6M3 aircraft was fitted with a new set of wings with heavier gauge skin and with redesigned, non-folding rounded wingtips. The wingspan was reduced to 36 feet 1 1/16 inches

The A6M5 was faster than the A6M3 Model 32. More important, it could now be dived at speeds of up to 410 mph. It was rushed into production as the Navy Type 0 Carrier Fighter Model 52.

The Model 52 began to reach front line units in the autumn of 1943. It was immediately confronted by the new Grumman F6F Hellcat, which was slightly less maneuverable but which was much more strongly built, heavier armed, and better protected.

A6M5a
Heavier gauge wing skin which enabled a further increase in diving speed to 460 mph, bringing it almost up to Western standards. This was to be the highest diving speed attained by any Zero variant. Armament was improved by replacing the drum fed Type 99 Model 2 Mk3 cannon with 100 rpg with belt-fed 20-mm Type 99 Model 2 Mk4 cannon with 125 rpg.

A6M5b
Additional armament, some fire protection for the fuel tanks and some armor protection for the pilot. One of the fuselage-mounted 7.7-mm Type 97 machine guns was replaced by a 13.2-mm Type 3 machine gun.

A6M5c
Two additional 13.2-mm machine guns were installed in the wings outboard of the cannon. The fuselage-mounted 13.2-mm machine gun was retained, but the smaller-caliber 7.7-mm fuselage-mounted gun was deleted. An armor plate was mounted behind the pilot’s seat to provide some protection against attacks from the rear. Wing racks were provided for unguided air-to-air rockets.

A6M6c
Powered by the water-methanol boosted Sakae 31 engine

A6M7 dive bomber
The under-fuselage drop tank installation was replaced by a special bomb rack capable of carrying a single 551 pound or 1100 pound bomb.

A6M8
The A6M8 was the last production version of the Zero.
The forward fuselage was completely redesigned to accommodate the 1560 hp Mitsubishi MK8P Kinsei 62, which had a larger diameter than the Sakae, requiring that the fuselage-mounted gun be removed. At the same time, the fuel tank fire-extinguishing system was improved, and additional fuel tankage was added. The fuselage center line could carry a single 1100-lb bomb, and a pair of 77-Imp gall drop tanks could be carried underneath the wings.

Six thousand three hundred machines were ordered. However, owing to the chaotic conditions prevailing in Japanese industry in the closing months of the war, none were actually delivered.


Most Famous Japanese Plane of WWII – 15 Facts About the Mitsubishi Zero

One of the most famous planes of the Second World War, the Mitsubishi A6M Zero-Sen, was Japan’s best fighter and the bane of Allied airmen in the Pacific.

Rigorous Specifications

The Zero was designed to meet a tough set of specifications set down by the Japanese Navy in 1937. They wanted a plane to replace the A5M carrier fighter, also produced by Mitsubishi. The new plane had to have a top speed in excess of 310mph (about 499kmph) and reach an altitude of 9840 feet (almost 3,000 meters) in three and a half minutes. It also had to have better maneuverability and range than any existing fighter, as well as carry two machine guns and two cannons. It was an ambitious brief.

Mitsubishi A6M Zero By Marc Grossman CC BY-SA 3.0

The Only Competitor

Given the difficulty of meeting the Navy’s demands, few companies were willing to take up the challenge. Only Mitsubishi threw its hat into the ring, with a design team led by Jiro Horikoshi.

Taking Flight

The prototype Zero first took flight on April 1st, 1939. It met the expectations of the navy and proved the incredible skill of Jiro Horikoshi’s team. On the 14 th of September, it was accepted into service as the A6M1 Carrier Fighter.

Jirō Horikoshi was a student of the Faculty of Engineering, Tokyo Imperial University.

Changing Engines

The first Zeros were powered by the Mitsubishi Zuisei, a relatively lightweight engine that minimized the weight of the plane. Later on, these were replaced by Nakajima Sakae 925hp radial engines. The Sakae was a little heavier and larger than the Zuisei, but more than compensated for this with extra power. The plane far exceeded the Navy’s expectations.

Named for the Year

Many Japanese military vehicles were named for the year in which their production began. This pattern extended to Navy fighters. The Zero entered full production in 1940 AD, equivalent to the year 2600 in the Japanese calendar. Based on this, it was given the name Zero-Sen – Type Zero.

A pair of Zeros over China

First Fight Over China

As the Zero was being prepared for production, Japan was embroiled in an invasion of China. As the Chinese put up increasingly stiff resistance, the Navy asked for early Zeros to be sent to China. It was here that they saw their first use in combat in August 1940. In the skies above Chungking, 15 Zeros shot down all the Chinese fighters sent against them – a very promising start for Mitsubishi’s creation.

Ignored by the West

Intelligence about the impressive new fighter quickly reached the American government. Despite rising tensions in the Pacific, they largely ignored this information until after the attack on Pearl Harbor in December, 1941. As a result, the Americans missed out on a year of planning to tackle this formidable weapon.

Photograph taken from a Japanese plane during the torpedo attack on ships moored on both sides of Ford Island shortly after the beginning of the Pearl Harbor attack.

The First Sea-Borne Plane to Outclass Land-Based Opponents

Naval planes faced limitations on their design due to the need to be transported on and flown from aircraft carriers. It was one thing for a shipboard fighter to reliably defeat an enemy equivalent, but the Zero was the first plane to achieve something more – becoming a seaborne plane that could reliably beat land-based fighters. This made it a particularly intimidating foe, one that Allied pilots struggled against.

A6M2 “Zero” Model 21 of Shōkaku prior to attack on Pearl Harbor, 7 December 1941.

An Aerial Armada

In the early days of the war in the Pacific, it seemed to the Allies that the Japanese must have had an endless supply of Zeros. They appeared in every major battle, tearing holes in Allied air forces.

In reality, the Japanese had fewer than 500 Zeros by December, 1941, but they were working on making more. Over the course of the war, Mitsubishi manufactured 3,879 Zeros. In addition, Nakajima made a further 6,215, and Sasebo, Hitachi, and Nakajima produced 844 between them – a total of 10,938 planes.

An Imperial Japanese Navy Mitsubishi A6M Zero fighter on the aircraft carrier Akagi

Dominating the Early War

Throughout 1942, the Zero flew triumphantly through the skies over East Asia and the western Pacific. Fast, maneuverable, and well-armed, it was regularly able to defeat the fighters the Allies flew against it. In fighting over Ceylon, Zeros decisively defeated British Hawker Hurricanes, planes admired for their impressive maneuverability.

Flying from Land and Sea

Though designed as carrier aircraft, Zeros also flew from land. This often involved longer distance flights, as Japan used island bases to extend its dominance.

Zero A6M3 Model 32.

Flown by the Enemy

“Know your enemy” is one of the most fundamental maxims of war. In keeping with this, understanding and defeating the Zero became an obsession for Japan’s opponents. In the middle of 1942, they finally got their wish when they captured a Zero intact.

This plane was shipped to the United States, where a program of intensive testing began. To their surprise and delight, the Americans discovered that this powerful plane had flaws and limitations, flaws which they could now use to their advantage.

A6M3 Model 22, flown by Japanese ace Hiroyoshi Nishizawa over the Solomon Islands, 1943

The Americans, British, and Chinese all carried out test flights in captured Zeros bearing their countries’ own markings. This became a driver for innovation in the Pacific war.

Fall of a Champion

In 1943, the tables were turned. The Allies, who had been frantically improving their fighter designs, started fielding planes with more powerful engines and better armor. The Zero, which had barely changed in four years, had little protection against harder-hitting weapons and better-moving planes. The Zero went from winning most confrontations to losing them.

Mitsubishi A6M3 Zero wreck abandoned at Munda Airfield, Central Solomons, 1943

Engine Upgrade

To counter this change, Mitsubishi created the most powerful Zero, the A6M8. Its 1560hp Kinsei engine made it a better match for its enemies, but it wasn’t enough to regain its dominance.

Kamikaze

Having lost much of its value as a fighter, the Zero was the first plane to be used in kamikaze (“divine wind”) attacks. Loaded with explosives, Zeros were turned into flying bombs for suicide attacks against Allied targets. Following the first successes, entire kamikaze teams were formed, with Zeros as their most popular planes.

Once the best weapon in the air, the mighty Zero could now only win by destroying itself.


Messerschmitt Bf 109

The Messerschmitt Bf 109, officially shortened to Bf 109, was the iconic German fighter of WWII. An argument could be made that the Bf 109 was the most successful fighter platform of the war. Which is not to say that the 109 was the best fighter of the war, but that its design was the most solid and serviceable of WWII.

With initial plans dating back to 1934, first prototype flown in 1935, and the first model entering operational service in 1937 and seeing combat in the Spanish Civil War, the Bf 109 was the only fighter, aside from the Spitfire, that was deployed in front line service at war&rsquos beginning in 1939, and with incremental improvements, remained in front line service, effective and competitive against newer fighters, until war&rsquos end. The prototype that flew in 1935 was the world&rsquos first low wing, retractable wheels, all metal monoplane fighter &ndash a basic design subsequently used by all sides during WWII.

At its most basic, the essence of the Bf 109 was to take the smallest feasible airframe, and attach to it the most powerful engine possible. The design had flaws, such as a cramped cockpit, a poor rear view, and a narrow undercarriage that rendered ground handling hazardous to inexperienced pilots. Moreover, small size translated into limited fuel capacity, reducing its range &ndash which proved problematic during the Battle of Britain, when Bf 109s were typically limited to 15 minutes&rsquo worth of fighting over Britain, before dwindling fuel forced them to disengage and fly back home.

Nonetheless, the basic concept of small airframe married to big engine proved successful, allowing as it did for progressive upgrades as more powerful engines became available, and allowing the Bf 109 to remain competitive throughout the war. The adaptable design allowed the plane to progress from the 109D model in 1939, with a top speed of 320 m.p.h., to the 109K model at war&rsquos end, capable of 452 m.p.h.

Eric Hartman, the war&rsquos top ace with 352 kills, flew the Bf 109. Indeed, the top three aces of the war, with over 900 kills between them, flew 109s, as did the top scoring ace against the Western Allies. In addition to the interceptor and escort role for which it had been originally designed, the 109 was sufficiently adaptable to serve in other roles, including ground attack, and reconnaissance. With nearly 34,000 manufactured between 1936 and 1945, the Bf 109 was the most produced fighter aircraft in history.


Myth of the Zero

This Mitsubishi A6M5, captured at Saipan in July 1944 and now maintained by Planes of Fame, is the only Zero still flying with its original Nakajima Sakae 31 engine.

Mitsubishi’s legendary A6M ran circles around opposing fighters early in World War II, but by 1945 its odds of surviving a dogfight were close to zero.

Has there ever been a warplane as mythic as the Mitsubishi Zero? Legend, mystery, racism and rumor conflated to create an unbeatable fighter flown by samurai-tough pilots. The Zero was said to have awesome performance, superb maneuverability and combat characteristics an order of magnitude ahead of anything else in the sky.

Or, if you believed a different set of legends, mysteries, racism and rumor, it was a flimsy, beer-can tinderbox that brazenly aped Western designs and was flown by short, bandy-legged Asians who wore Coke-bottle-bottom glasses and fled whenever the U.S. Navy opened a can of Grumman whup-ass.

The truth—and how many times have you heard this?—lies somewhere in the middle.

The oft-forgotten fact is that the Zero’s effective combat career was measured in months. Not counting its earliest sucker-punch missions over China, when the best-trained fighter pilots in the world swatted down scores of ill-flown Polikarpov biplanes and open-cockpit monoplanes, the Zero reigned supreme in the Pacific War only from the day of the Pearl Harbor attack until American pilots learned tactics that allowed even pudgy F4F Wildcats to level the aerial playing field during the Guadalcanal campaign in the summer and fall of 1942. When the second generation of U.S. World War II fighters—P-38, F4U and F6F—arrived beginning in early 1943, the Zero was finished as an effective fighter. In January 1944, a single Marine F4U pilot, 1st Lt. Robert Hanson, shot down 20 Zeros in 17 days.

The Zero soldiered on until the end of the war, of course—many self-immolating as kamikazes—but only because the Japanese had nothing to replace it, and the Zero often was simply cannon fodder. The June 1944 Marianas Turkey Shoot is the most notorious example of such inequity. Not that the Zero wasn’t still dangerous even in 1945, especially if an aviator was cocky enough to try to dogfight one of the few remaining experienced Zero pilots. Nobody ever built a fighter that could outmaneuver it, and the fact that Grumman developed the F8F Bearcat as a Zero-beater—a task that it was just a bit too late to fulfill—shows that the Zero was never entirely disdained.

The Japanese had counted on a short, brutal war—not to annex America as an enormous sushi-loving colony, but to force the U.S. to the negotiating table in order to establish an unfettered area of Japanese exploitation in Southeast Asia and the Pacific. So Japan had done little to prepare for a protracted conflict. Zero pilots were superbly trained, but only hundreds at a time, then a few thousand a year while the U.S. was turning tens of thousands of college grads into pilots the great majority of Japanese pilots were the equivalent of our NCOs. Nor was the production of a Zero successor given high priority. Much like the German high command initially assumed the Me-109 would suffice for the duration of the war and that it didn’t need to engineer a successor, the Japanese waited too long to develop and produce the Shiden, Raiden and Reppu. Or perhaps they should have developed just one of them. It didn’t help that Japan, a small island nation with limited engineering and manufacturing manpower, spent its time dithering over the development of more than 90 major combat types as well as several dozen lesser models. By the time they did get serious, raw materials were lacking and the country’s skilled airframe-and-engine workforce had fled the manufacturing centers, bombed out of their homes.

The Zero was incrementally improved throughout the war, from the A6M2, the first model to take on American fighters, to the A6M8 (only two built), intended to attack B-29s. The Zero’s excellent Nakajima-built Sakae engine was eventually upgraded by about 150 hp, but it never attained anything like the horsepower offered by the Pratt & Whitney R-2800, the P-38’s twin Allisons or the P-51’s Packard Merlin. Yes, the Zero’s power-to-weight ratio was always better than that of its U.S. opponents, but sheer horsepower allowed the Americans to loft superior firepower, substantial armor and overbuilt airframes. What the Japanese needed and never got was not a better Zero but an all-new fighter—a Japanese Hellcat. When the war ended and the Zero stood down, the U.S. was within a week or two of introducing yet a third generation of Pacific fighters in the form of the Bearcat. Imagine a novice Zero pilot forced to confront this Grumman brute.

The Zero began the Pacific War with an aura of invincibility. After Pearl Harbor, it quickly came to be viewed as some kind of mystery ship, imbued with strange powers, able to do things no other airplane could. Yet it was simply a well-engineered, straightforward aircraft optimized for maneuverability and flown against an enemy that had never credited the Japanese with the ability to design a cutting-edge fighter. Even though Claire Chennault of the Flying Tigers had sent back to the U.S. reports of the airplane’s capabilities over China, they were ignored, and American aircraft-recognition manuals didn’t even include a picture of a Zero. As aviation historian William Green wrote, the Zero“created a myth—the myth of Japanese invincibility in the air….Its successive appearance over every major battle area in the opening days of the war seemed to indicate that the Japanese possessed unlimited supplies of this remarkable fighter, and its almost mystical powers of maneuver and ability to traverse vast stretches of water fostered the acceptance of the myth of its invincibility in Allied minds.” Zeros often showed up so far from the nearest Japanese-controlled land that the Americans set out in search of the carrier from which it was assumed they’d taken off.


Petty Officer Second Class (PO2c) Sakae Mori, takes off from the carrier "Akagi" in an A6M2 to participate in the Pearl Harbor attack on December 7, 1941. (National Archives)

The Zero was designed by a team under the direction of a brilliant young aeronautical engineer, Jiro Horikoshi. Mitsubishi had the foresight to send Horikoshi to work and observe at aircraft factories in Europe and the U.S. in 1929, and he even spent several months at a Curtiss plant in New York, as an acceptance inspector for a batch of P-6 Hawk pursuit biplanes the Japanese had ordered. Horikoshi had already engineered the Mitsubishi A5M, later code-named “Claude” by the Allies. For an open-cockpit, fixed-gear fighter, the A5M displayed outstanding performance—in no small part because of its flush riveting, a production technique the Japanese would subsequently use on the Zero at a time when American airframers were just discovering its low-drag advantage. In order to fight not only the already-overmatched Chinese but also the Pacific war against the U.S. that was beginning to look inevitable, however, Japan needed something more than the Claude. The Japanese would never have attacked Pearl Harbor if they hadn’t had the Zero. At the time, in fact, some planners had misgivings that there weren’t yet enough Zeros available for the attack to succeed.

When the Japanese navy gave Mitsubishi its marching orders as Zero design began, it demanded a triple threat: an escort with the extreme range needed to accompany bombers deep into China and later to cover vast Pacific distances a point-defense interceptor with a rapid rate of climb to hit attacking bombers before they reached their targets and a consummate dogfighter with extreme maneuverability. (Though it’s often assumed the Japanese army air force also flew Zeros, it never did. Another Zero oddity is that though all Japanese naval aviators were carrier-qualified, many, including the famous Zero super-ace Saburo Sakai, never operated from a carrier in combat.)

The extreme-range criterion resulted in one piece of little-acknowledged pioneering for which the Zero was responsible: It was the first airplane designed from inception to carry a jettisonable external fuel tank. A Zero’s maximum fuel load, including the belly tank, typically was about 230 gallons, and this gave it a seven- or eight-hour combat endurance. Sakai set the Zero endurance record—just over 12 hours—by throttling back to 1,700 rpm and running what today we’d call “lean of peak” (maximum exhaust-gas temperature) at just 130 mph. He intentionally ran his tanks bone-dry while circling above his Formosa air base after a mission and dead-sticked in from 8,000 feet.

Another Zero innovation was its 360-degree-view cockpit canopy, second only to the British Westland Whirlwind’s bubble canopy. Though it was a multipaned greenhouse rather than a true bubble, the Zero’s glassware provided a considerably better rearward view than anything but a true open-cockpit design, and also had excellent drag-reducing properties. It could be opened in flight but not jettisoned, making parachute egress difficult. It was assumed that a Zero samurai would continue fighting to the death rather than bail out. Most Zero pilots refused to wear parachutes in any case, until they ultimately were ordered to strap them on.

It has often been said that “the engine makes the airplane,” whether it’s the Spirit of St. Louis’ Wright Whirlwind, the P-51’s Merlin or the 747’s JT9D. In the late 1930s the Japanese had developed nothing more powerful than several 800- to 1,000- hp radials with little growth potential, at a time when American, British and German manufacturers were cranking out 1,200-hp engines, with 2,000 hp visible on the horizon. So Horikoshi needed to make his new fighter super light, which he did in part by having lightening holes cut and drilled through every internal airframe part possible—a technique that racecar builders would recognize immediately. In fact, Horikoshi could be called the Colin Chapman of aircraft designers Chapman was the Lotus designer whose mantra was “simplicate and add lightness.”

This horrified some traditional engineers, one of whom, when later asked to identify the Zero’s main weakness, complained that “it was full of holes!” Horikoshi also persuaded the navy to change its ultimate-load standards for many components he didn’t consider crucial he designed them to “fail” but then rebound to their previous shape as soon as the load was reduced. As a result, the Zero was the fastest 1,000-hp, radial-engine fighter ever produced—but one with a number of single-point-failure locations that, if hit, could bring down the airplane.

The Zero was skinned with the lightest-gauge aluminum possible, and when the shadows were right, some photos of Zeros in flight show them seemingly clothed in crinkled tinfoil, especially in the cockpit area. British test pilot Eric Brown, who flew a captured Zero immediately after the war, even today recalls the constant noise of the oil-canning fuselage skin—“like the sound produced when one pushes on the side of a large biscuit tin.” A typical Zero loaded with full fuel and ordnance weighed about 5,500 pounds—less than a midsize Cessna twin. A fully loaded Hellcat weighed well over twice that much, and definitely wasn’t full of holes.

The single heaviest component of any airframe is the main wing spar. Horikoshi lightened the Zero’s by 30 percent by using a new zinc/aluminum alloy called Super Ultra Duralumin, which had recently been developed by Sumitomo Metals. A similar alloy was at the same time being experimented with in the U.S., and it would come to be called 7075—the most common “aircraft grade” aluminum even today. One major benefit of 7075 over the Sumitomo metal was that it was very corrosion-resistant. In many recovered Zero hulks, the main spars have largely turned to powder.

In another weight-saving measure, the Zero’s main spar was continuous, from wingtip to wingtip, and thus was an inseparable part of the fuselage center section rather than having a left and right wing, each bolted to the fuselage. This eliminated the weight of fasteners and spar brackets. Though it might seem that permanently affixed wings would make a Zero difficult to transport, Horikoshi had designed the entire tailcone and empennage to easily unbolt just aft of the cockpit. With everything removed forward of the firewall as well, the wing and cockpit became a single long but light and narrow truckload.

Horikoshi’s search for lightness led him to the oft-criticized failure to include adequate armor or self-sealing fuel tanks in the Zero design. What is forgotten, however, is that virtually no fighters at the time the Zero was introduced had such features. It remained for the Battle of Britain, in the summer of 1940, to demonstrate the need for armor and protected tanks. In any case, the Zero’s designers considered armor unnecessary because they didn’t think anybody would be able to put any rounds into the fighter. Maybe a lucky shot here and there, but not enough of a danger to compromise the design’s lightness. Little did they know what the Navy and Marines had in store for them.

Most combat units also removed their Zeros’ radios for additional weight savings, since the Japanese transceiver was of very poor quality. (How strange, since Japan quickly became the world’s microelectronics powerhouse two decades later.) This left Zero pilots unable to warn wingmen of surprise attacks, and they could coordinate their own attacks only with occasional hand signals. A typical multi-plane Zero attack was a melee of individual aerobatics, and Japanese pilots were in nearly as much danger of midairs with their mates as they were of getting shot at. As one USN pilot put it, “From the way the Zero pilots rollicked around the sky, at times it looked as though they would rather stunt than fight.”

“Yonekawa…flew upside down, waving both hands around in the cockpit,” wrote Sakai in his book Samurai.“Then he flew directly over me, under me, and went through a wide hesitation roll around my fighter. He was like a kid showing off. He finally flew on my wing and held the stick between his knees. Still grinning, he waved his lunchbox at me and started to eat.”

Zero pilots had actually preceded naval aviator John Thach’s famous “Thach Weave” by developing their own “escort weave” tactic while protecting bombers. But without fighter-to-fighter communication, it was far less effective than Thach’s independently developed cover-my-six maneuver.

The Zero’s flight controls mixed some ingenious engineering with at least one awkward feature: Its ailerons were large and powerful, which added greatly to the fighter’s low-speed maneuverability and spectacular roll rate, but they were very difficult to deflect at high speeds. American pilots soon learned to dive and turn sharply—especially to the right, which substantial prop-induced torque made particularly difficult for the Zero—when they had a Zero on their tail.

Horikoshi did an interesting job with the Zero’s elevator, however. The airplane’s speed range was broad, from low-speed maneuvering to flat-out dashes at more than 300 mph, and elevator effectiveness of course increased with speed, to the point where it could become quite touchy. So Horikoshi designed an elastic control system, with thin elevator cables that stretched a bit as speed increased and a slightly flexible elevator-control torque tube. Normally, such a setup would be anathema to an aeronautical engineer, for it encouraged an elevator to flutter as speed increased, but somehow, whether through luck or engineering talent, Horikoshi found a sweet spot where there was no danger of flutter yet elevator control forces remained constant regardless of the airspeed.


Hiroyoshi Nishizawa, Japan's highest scoring Zero pilot, leads a flight of A6M3 Model 22s of the 251st "Kokutai" from Rabaul in 1943. (National Archives)

Zeros were feared in part because of their two heavy wing-mounted 20mm cannons—Swiss Oerlikons built under license by the Japanese. (Japanese hospitality: Oerlikon sent five Swiss engineers to Japan in 1938 to help set up production, and the Japanese interned them until 1945.) Horikoshi suspected that the Zero would yaw appreciably as first one and then the other cannon fired and recoiled, so he specified a fuselage longer than its optimal length, which gave the vertical stabilizer a longer moment arm and thus provided greater longitudinal stability. But the Oerlikons were still problematic. They had a low rate of fire, limited capacity (initially only 60 rounds per gun, later increased to 100) and low muzzle velocity. The latter meant that the cannon was effective for close-in fighting, where a single round into a Wildcat’s wing root or cockpit could mean a kill, but as the distance to target increased, the cannon rounds would lose energy and drop away ineffectually, like a softball thrown underhand.

A number of the Zero’s smaller components, such as instruments and engine accessories, were also license-built Bendix, Sperry, Kollsman and other designs, which would lead to later claims that the airplane was a “copy” of the Hughes H-1 Racer or the vaguely similar looking Vought V-143, but as Horikoshi later wrote, “We were trying to surpass the rest of the world’s technology, not just catch up to it.” The Zero’s single most important “U.S.” part was its Hamilton Standard-design constant-speed propeller. The Japanese had also bought a V-143 in 1937, and the Zero’s landing gear and retraction mechanism was almost certainly a copy of the Vought’s design after all, the Zero was one of the first retractables the Japanese built.

The Zero’s two cowl-mounted 7.7mm machine guns were not particularly effective, especially against the new generation of heavy, over built U.S. fighters. At little more than half the caliber of the American .50s, they were used by many Zero pilots mainly as “pointers” for their cannons if they saw hits from the machine guns, they toggled the cannons alive and fired them instead. Just like a World War I Spad or Fokker, the Zero’s 7.7mm receivers were in the cockpit, above the instrument panel on either side, and the pilot pulled levers to charge them. Shades of the Red Baron.

Ultimately, the Zero’s main failing was that it was designed to a 1930s paradigm: Air combat meant dogfighting, and dogfighting, at least in the days before energy management, meant a circle-chase, in one form or another, with the better airplane turning tighter than the lesser one and eventually getting into a firing position from a rear quarter. Victory was then nearly inevitable. And the Zero was the world’s tightest-turning, most maneuverable fighter. Thanks to its aerobatic ability, Zero pilots also developed a combat maneuver that initially baffled American airmen: a kind of sideways loop with square turns and side-slips out of the turns, which tightened the turn greatly.

It didn’t take long, however, for American pilots to learn that rat-racing with a Zero was a loser’s game, so they disdained tail chases that played straight into the Zero’s only air combat strength it was neither strong, unusually fast, good in a dive nor effectively armed. Hit and run became the mantra: Attack a Zero from above, fire while diving upon it and then keep going. Convert diving energy to zooming altitude and do it again, if necessary.

Perhaps it was inevitable that the Zero would become a myth, a legend, a paragon among fighters when it was in fact a conventional airplane with several ahead-of-its-time characteristics. It could be argued that the Zero was an excellent airplane but a lousy fighter. After flying a Zero, the highly respected Curtiss test pilot H. Lloyd Child even suggested that “a commercial version of it would appeal to a sportsman pilot after the war. Its clean lines, simplicity, lightness and ease of handling…would make this a desirable airplane for a millionaire private owner.”

If you discount the victories over poorly trained Chinese pilots flying outmoded Soviet fighters, the huge fleet of Allied aircraft destroyed while they were parked in the opening days of the war and the kills of utterly unprepared American pilots in many cases flying adequate airplanes but using the wrong tactics against the Zero, the mythic Mitsubishi comes off surprisingly poorly. It was extremely light and had numerous failure points where a very few rounds of heavy-caliber machine gun fire could do catastrophic damage. It was flammable, and its pilot was terribly vulnerable. It was not particularly fast, and in any case its high-speed handling was poor. Its controls were poorly harmonized. Its armament was a mixed bag of too-light machine guns and crude cannons. It had no useful communications equipment. Ultimately, the Zero was a bare-bones airplane—nothing extra, nothing fancy—typical of frugal Japanese designs “with very little margin for modification, designs which had little, if any, ‘stretch’ built into them,” wrote Zero expert Robert C. Mikesh.

Some say that because the Zero was the best dogfighter in the Pacific theater, perhaps the world, it was by definition the best fighter. But there’s an old saying in auto racing, “To win, you have to finish.” So praising the Zero’s maneuverability is a bit like saying a racecar is the best in the world be cause it’s the fastest, even if it can’t finish more than 10 laps of a track before having a mechanical failure and being beaten to the checkered flag by a slower car.

Unfortunately for the Japanese, the Pacific War was one race that the Zero finished last. Dead last.

For further reading, frequent contributor Stephan Wilkinson recommends: Zero, by Robert C. Mikesh Eagles of Mitsubishi: The Story of the Zero Fighter, by Jiro Horikoshi and Combat Legend: Mitsubishi Zero, by Robert Jackson.

Originally published in the July 2012 issue of Aviation History Magazine. To subscribe, click here.


Japanese “Army Zero” – Nakajima Ki-43 in 27 Photos

The Japanese Nakajima Ki-43 Hayabusa was a relatively slow, lightly armed, and fragile land-based tactical fighter plane, but it became legendary for its performance in East Asia during the early years of the Second World War, and was famous for its extraordinary maneuverability and climb rate during its service with the Imperial Japanese Army Air Service.

Although the Ki-43 was officially reported as Oscar by the Allies, it was often referred to as the “Army Zero” by American pilots, owing to the fact that its layout and lines, Nakajima Sakae radial engine, round cowlings, and bubble-type canopy were features very similar to the Mitsubishi A6M Zero long-range fighter, which served with the Japanese Navy.

Propeller, Nakajima Ki-43-II Hayabusa in the “Great Patriotic War Museum”. Photo: Mike1979 Russia CC BY-SA 3.0

Hideo Itokawa was the designer of the Ki-43, and his achievements would later earn him fame as the pioneer of Japanese rocketry. It is important to note that the Ki-43 story did not start out as a success story.

Front view of a Japanese Nakajima Ki-43 Hayabusa (隼 Peregrine Falcon), designated as an Army Type 1 Fighter, and referred to by Allied forces as “Oscar”.

The first flown prototype in early January 1939 was a disappointment as it did not offer better maneuverability than the Ki-27, the purpose for which the Ki-43 had been made.

Hideo Itokawa – a pioneer of Japanese rocketry, popularly known as “Dr. Rocket,” and described in the media as the father of Japan’s space development.

To correct the manueverability problems, subsequent prototypes were produced between 1939 and 1940. Major changes were made and many field tests were executed. Experimental changes included a slimmer fuselage, a new canopy, and the introduction of Fowler flaps to improve the lift of the plane’s wings at a certain speed. The Fowler flap was implemented on the 11th prototype and brought about a dramatically enhanced performance in tight turns.

Ki-43 Hayabusa Cockpit (1944)

The 13th prototype combined all these changes, and tests conducted with this aircraft ended satisfactorily. Thus, the Nakajima Aircraft Company was instructed to place that prototype, which was designated Ki-43-I, into production.

Nakajima Ki-43-I Hayabusa aircraft in flight over Brisbane, Queensland (Australia) in 1943.

The Ki-43-I had an amazing maneuverability and remarkable climb rate owing to its light weight. It was powered by a Nakajima Ha-25 engine, and its maximum speed was 307.5 mph at 13,160 ft.

A Japanese Nakajima Ki-43-I Hayabusa (s n 750) in dense jungle 6 km from Vunakanau airfield, Rabaul, in September 1945.

Prototypes for the Ki-43-II had their maiden flights in February 1942. They came with the more powerful Nakajima Ha-115 fourteen cylinder air-cooled radial engine, which was an upgrade from the Ki-43-I’s engine. The wing structure of the Ki-43-I was strengthened in the Ki-43-II, and racks were added to the wings for drop tanks or bombs. Its speed also increased to 333 mph and its climb rate to 3,900 feet per minute.

Nakajima Ki43 II, P-5017, Chinese Air Force

It was equipped with an armament consisting of two fixed, forward-firing 12.7 mm Ho-103 machine guns in the cowl, and two 551 lb bombs.

12.7 mm Ho-103 machine gun.Photo Sturmvogel 66 CC BY-SA 3.0

It had a self-sealing fuel tank and a .5″ armor plate to protect the pilot’s head and back. Its canopy was slightly taller, and a reflector gunsight replaced the telescopic gunsight of the earlier prototype.

By November 1942, production of the Ki-43-II began at Nakajima’s Ota factory.

Nakajima Ki-43 type2 – at Pima Air Space Museum

The Nakajima was the most widely used fighter in the Japanese Army Air Force (JAAF) and fully equipped both the 30 Sentai Flight Regiment and 12 Chutais Independent Squadron. The first unit to be equipped with them was the 59th Flight Regiment, whose Ki-43s made their debut operational sorties across the skies of Hengyang on 29 October 1941.

Japanese Army Air Force fighter plane active in the Pacific throughout the war. The Japanese name for this aircraft was “Peregrine Falcon” and the Allied code name was “Oscar”.Photo Stumanusa CC BY 3.0

Ki-43s fought over the skies of the Japanese home islands, China, the Malay Peninsula, Burma, the Philippines, New Guinea, and other South Pacific islands.

A captured Japanese Nakajima Ki-43 Hayabusa (Allied code name “Oscar”) fighter at Clark Field, Luzon (Philippines), in 1945.

During their first combat experiences, the Ki-43 exerted some aerial superiority in Malaya, Netherlands East Indies, Burma and New Guinea just as the Zero did, but as the war got more intense, its light armor and less efficient self-sealing fuel tanks would be its weaknesses, causing several losses and casualties. Its machine guns could barely penetrate the heavily armored Allied planes.

Captured Ki-43 Hayabusa on Munda Field 14 June 1944

From October to December 1944, 17 Ki-43s were downed, but to their credit, they scored a total of 25 kills, claiming the fall of Allied aircraft such as the C-47, B-24 Liberator, Spitfire, Beaufighter, Mosquito, F4U Corsair, B-29 Superfortress, F6F Hellcat, P-38, and B-25.

US Ki-43-II Otsu code XJ005 Hollandia 1944

Towards the end of their time, several Ki-43s, just like many other Japanese aircraft, were expended in kamikaze strikes.

Nakajima, Ki-43, Hayabusa ‘Peregrine Falcon’ Oscar ‘Jim’ Army Type 1 Fighter

By the time of its retirements, in 1945 in Japan and 1952 in China, a total of 5,919 Nakajima Ki-43s had been built, with 13 variants.

A Japanese Nakajima Ki-43-I Hayabusa at Brisbane, Queensland (Australia) in 1943.

A Japanese Nakajima Ki-43-II Hayabusa fighter.

Front view, Nakajima Ki-43-IB Oscar at the Flying Heritage Collection.Photo Articseahorse CC BY-SA 4.0

Japanese Nakajima Ki-43 Hayabusa (隼 Peregrine Falcon), designated as an Army Type 1 Fighter, and referred to by Allied forces as “Oscar”.

Ki-84s, Ki-43s on a JAAF base post-war.

Nakajima Ki-43 from “Kato hayabusa sento-tai (Colonel Kato’s Falcon Squadron)”.

Nakajima Ki-43 Hayabusa fighter, taken as war booty by the Chinese Nationalists and issued to the 6th Group of the Chinese Nationalist Air Force, runs up before a flight.

Nakajima Ki-43-IB Hayabusa taking off at Brisbane, Queensland (Australia) in 1943. After its capture it was rebuilt by the Technical Air Intelligence Unit (TAIU) in Hangar 7 at Eagle Farm, Brisbane.

Nakajima Ki-43-IB Oscar at the Flying Heritage Collection.Photo Articseahorse CC BY-SA 4.0

Nakajima Ki-43-II Hayabusa in the Great Patriotic War Museum.Photo Mike1979 Russia CC BY-SA 3.0

Nakajima, Ki-43, Hayabusa “Peregrine Falcon” Oscar “Jim” Army Type 1 Fighter

The Nakajima Ki-43 Hayabusa (隼, “Peregrine Falcon”) was a single-engine land-based tactical fighter used by the Imperial Japanese Army Air Force in World War II.

Wreck of a Japanese Army Air Force Nakajima Ki-43 Hayabusa plane (Oscar) in the Southwest Pacific in 1943.


Japan’s Mitsubishi A6M Zero Fighter was Amazing, Except for 1 Weakness

How effective can an aircraft carrier-based fighter be without carriers?

Here's What You Need To Remember: The Wildcat never exceeded the Zero in performance, but over time the non-existent armor protection and loss of entire carriers took a heavy toll on Japanese aviators, eroding their experience advantage. In 1943, new, much faster U.S. fighters such as the F6F Hellcat and F4U Corsair decisively won air superiority for the Allies.

Japan began the Pacific War with two major technological advantages over the U.S. Navy: the much more reliable Long Lance torpedo, and the Mitsubishi A6M Zero carried-based fighter, a design that defied expectations by outperforming land-based fighters when in it was introduced into service in 1940.

Designer Jiro Horikoshi maximized the Zero’s performance by reducing airframe weight to an unprecedented degree by cutting armor protection and employing an “extra super” duralumin alloy. Combined with an 840-horsepower Sakae 12 radial engine, the A6M2 Type Zero could attain speeds of 346 miles per hour, while exhibiting extraordinary maneuverability and high rates of climb. For armament, the Zero boasted two punchy Type 99 20-millimeter cannons in the wing—though only with sixty rounds of ammunition—and two rifle-caliber machine guns firing through the propeller.

The elegant airframe weighed only 1.85-tons empty, giving the Zero a tremendous range of 1,600 miles—very useful for scouting for enemy ships and launching long-distance raids. By comparison, Germany’s excellent contemporary Bf 109 fighter could fly only 500 miles, fatefully reducing its effectiveness in the Battle of Britain.

The Zero debuted fantastically in combat in July 1940, with thirteen land-based A6M2 Zeros shooting down twice their number of Russian-built I-16 and I-153 fighters in a three-minute engagement.

When Japan launched her surprise attack on Pearl Harbor, and on British and Dutch possessions in East Asia, the 521 Zeroes serving in the Japanese Navy quickly became the terror of Allied fighter pilots. U.S. Army P-39 Airacobras struggled to match the Zero’s high altitude performance. Even the pilots of agile British Spitfires found they were likely to be out-turned and out-climbed by a Zero.

The U.S. Navy at the time was phasing in the Grumman F4F Wildcat at the expense of the infamously awful F2A Buffalo. The tubby-looking Wildcat was heavier at 2.5 to 3 tons and had a range slightly over 800 miles. The Wildcat’s supercharged 1,200 horsepower R-1830 radial engine allowed it to attain speeds of 331 mph while armed with four jam-prone .50-caliber machine guns, or 320 mph on the heavier F4F-4 model with six machine guns and side-folding wings for improved stowage.

Thus the U.S. Navy’s top fighter was slower and less maneuverable than the Zero. But unexpectedly—after a rough start, and despite starting the war with less combat experience, Wildcat pilots managed to trade-off evenly with Zeroes. At Wake Island, just four Marine Wildcats helped repel besieging Japanese forces for two weeks and even sank the destroyer Kisaragi. In February 1942, Wildcat pilot Edward “Butch” O’Hare managed to shoot down three Japanese bombers and damage three more during a raid.

Though the Wildcat didn’t claim air superiority over the nimble Japanese fighters, they performed well enough to allow American dive and torpedo bombers to sink five Japanese aircraft carriers in the Battles of the Coral Sea and Midway—finally turning the tide of the war in the Pacific.

How did they pull it off?

The Zero’s lack of armor and a self-sealing fuel tank (which have internal bladders that swell to close off holes) meant they were infamously prone to disintegrating or catching fire after sustaining light damage. Meanwhile, once a Zero pilot expended his limited supply of 20-millimeter shells, the remaining rifle-caliber machine guns struggled to down better-armored Wildcats. Navy and Marine Wildcat pilots learned to make slashing attacks from above leveraging their superior diving speed. But it simply wasn’t always possible to avoid getting into a turning dogfight with a Zero.

Contemplating this problem, naval aviator John Thach, devised the tactic called the Thach Weave in which two Wildcats flying side-by-side laid a trap for pursuing Zeros. Both the “bait” and “hook” plane would complete two consecutive 90-degree turns towards each other, forming a figure eight. A Zero choosing to pursue the bait plane would end up having its tail in the sights of the hook.

After successfully testing the maneuver with Wildcat ace Edward O’Hare, John Thach had a chance to try his Thach Weave the Battle of Midway. On June 4, Thach’s six F4Fs of VF-3 squadron from the carrier Yorktown were escorting Devastator torpedo bombers when they were bounced by fifteen to twenty Zeros, one of which immediately set a Wildcat ablaze while another knocked out the radio on the Wildcat of Thach’s wingman.

Thach called on the radio for rookie pilot Ram Dibb to help him perform the Weave maneuver. Steve Erling’s book Thach Weave recounts what happened next:

“With so many enemy planes in the air, Thach was not sure anything would work, but the answer came when a Zero followed Dibb during one of his turns… Thach found himself angry that the young inexperienced Dibb was the target of this Zero. Wisdom called for a short burst of shells to hopefully cause the Zero to break off the pass, but it was apparent this Zero was not going to break off. Anger rising, Thach continued straight ahead, the firing button depressed, rather than ducking under the Zero. At last the Zero broke off, and as he passed close by, Thach could see flames pouring from its underside.”

“Continuing the weave now discouraged the Zeros from following the Wildcats in their turns, but one made the same mistake as Thach’s first kill, and when he was too slow in his pullout, Thach shot him down and added a third mark on his kneepad. Soon after, Dibb erased another enemy fighter converging astern of Thach and Macomber.

By then the Zeros had shot down all but two of the torpedo bombers and might have finished off the Wildcats. But at that moment, two squadrons of SBD dive bombers came screaming out from the clouds on the now unprotected Japanese carriers. The Zeros were too low and far afield to intercept them, and bomber proceeded to fatally cripple the carriers Akagi and Kaga.

The Thach Weave was subsequently adopted by other Navy and Marine squadrons, and top Japanese ace Saburo Sakai described the maneuver vexing a squadron mate’s attack run over Guadalcanal in his biography.

The Wildcat never exceeded the Zero in performance, but over time the non-existent armor protection and loss of entire carriers took a heavy toll on Japanese aviators, eroding their experience advantage. In 1943, new, much faster U.S. fighters such as the F6F Hellcat and F4U Corsair decisively won air superiority for the Allies. In the 1944 Great Marianas Turkey Shoot over the Philippine Sea, Allied fighters and flak gunners shot down over 500 Japanese warplanes for just 123 USN aircraft lost.

Both the Zero and Wildcat saw action through the remainder of World War II, many of the former ending their days as Kamikaze aircraft. The Wildcat carried on a little-known but surprisingly successful career with the U.S. and Royal Navies in the European theater, dueling French fighters over North Africa, flying from small escort carriers to hunt Nazi bombers and submarines, and even embarked on the last Allied air raid of the war, sinking a U-Boat in Norway on May 5, 1945.

Sébastien Roblin holds a Master’s Degree in Conflict Resolution from Georgetown University and served as a university instructor for the Peace Corps in China. He has also worked in education, editing, and refugee resettlement in France and the United States. He currently writes on security and military history for War Is Boring. This first appeared in December 2018.


The Allies’ main opponent in the Pacific air war, the Mitsubishi A6M Zero is the most famous symbol of Japanese air power during World War II. The fighter first flew in April 1939, and Mitsubishi, Nakajima, Hitachi and the Japanese navy produced 10,815 Zeros from 1940-1945. Zeros were produced in greater number than any other aircraft. Its distinctive design and historical impact make the Zero an important machine in air power history.

The Zero got its name from its official designation, Navy Type Zero Carrier-Based Fighter (or Reisen), though the Allies code-named it “Zeke.” In the early part of the war, Allied aircraft such as the Curtiss P-40 and Seversky P-35 were at a disadvantage in a dogfight with a Zero flown by a skilled pilot, and the A6M became a well-known and dangerous opponent.

As explained by Mark Chambers in his book Wings of the Rising Sun, perhaps the most significant Zero captured during World War II, and the one that contributed most to Allied victory in the Pacific, was the A6M2 Model 21 known as “Koga’s Zero.” The aircraft’s history is particularly intriguing. In accordance with the IJN’s Midway offensive, it launched an attack on the Aleutian Islands, located in the southern coastal region of Alaska, in June 1942. The Japanese task force responsible for the strike was under the command of Rear Admiral Kakuji Kakuta, and his carrier-based aerial strike force bombed Dutch Harbor, located on Unalaska Island, twice on Jun. 3-4.

Assigned to the second of these strikes, 19-year-old P01 c Tadayoshi Koga took off in his A6M2 (construction number 4593) from the carrier Ryujo during the afternoon of Jun. 4. Flying in a formation consisting of three Zeros, Koga was accompanied by wingmen CPO Makoto Endo and PO Tsuguo Shikada. The three pilots strafed Dutch Harbor and downed the US Navy PBY-5A Catalina flown by Lt Bud Mitchell. Koga’s aircraft, however, subsequently sustained damage from American ground fire. With the return oil line of his fighter having been damaged, resulting in the Zero trailing oil in its wake, Koga pulled back on the throttle in an attempt to keep the engine running long enough for him to reach Akutan Island, 25 miles to the east of Dutch Harbor. The Imperial Japanese Navy Air Force (IJNAF) pilots had previously decided that Akutan was to be used as an emergency landing site should any of their aircraft be badly damaged, downed aviators then being rescued by IJN I-Boats (submarines) that were patrolling in the waters off the island.

Upon overflying a grassy area of Akutan, near Broad Bight, Shikada wrongly believed that there was solid ground beneath the grass. He communicated this to Koga, who attempted a conventional, gear down, landing. His aircraft flipped over as soon as its undercarriage came into contact with the marshy ground. While the Zero received little further damage, Koga suffered a broken neck when the fighter came to rest inverted, killing him instantly. All fighter pilots had been ordered to destroy any Zero that made an emergency landing in Allied-held areas to prevent the aircraft from falling into enemy hands. Endo and Shikada believed that Koga had survived the emergency landing, however, and they chose not to strafe the fighter prior to departing the area.

The aircraft remained preserved at the crash site for more than a month. Then, on Jul. 10, a US Navy PBY Catalina, with Lt William “Bill” Thies at the controls, made visual contact with Koga’s overturned Zero — the wreckage had first been spotted by PBY crewman Machinist’s Mate Albert Knack. After circling the downed Zero several times and confirming and recording the position of the wreck, the PBY flew back to Dutch Harbor. The following day, a recovery team was flown by Thies out to the crash site to assess the aircraft. After removing Koga’s corpse from the cockpit and hastily burying it close to the wreckage, Thies determined that the Zero was recoverable and reported this to his commander at Dutch Harbor. On Jul. 13 Lt Robert Kirmse led a recovery effort on Akutan. After providing Koga with a Christian burial near to the crash site, Kirmse and his men began the aircraft recovery process. After bringing in heavy lift equipment, the Zero was extricated from the mud and moved via land transport to a barge, which shipped it to Dutch Harbor. Once the fighter had reached the port the preservation process was initiated.

Koga’s Zero was subsequently loaded on board the transport vessel USS St. Mihiel (AP-32) and shipped southeast to Seattle, Washington. The aircraft was then transported by barge to Naval Air Station (NAS) North Island, arriving on Aug. 12. Here, the fighter’s damaged vertical stabilizer, rudder, wingtips, flaps and canopy were repaired, as was the landing gear and the Zero’s three-bladed Sumitomo propeller. The aircraft was then repainted in standard US Navy colors of the day (Blue-Gray over Light Gull-Gray) and adorned with US national insignia. Closely guarded by military police, the A6M2 made its first flight in American hands — with Lt Cdr Eddie R. Sanders at the controls — on Sep. 26.

Preliminary data obtained from ground study and evaluations of Koga’s Zero were relayed to both the Bureau of Aeronautics and Grumman, and it was the latter company’s Leroy Grumman and his design team that benefited most from this information. They were able to subtly modify their new F6F Hellcat prior to it entering widespread fleet service, these changes helping the Grumman aircraft become the most effective carrier fighter of the war.

Lt Cdr Sanders made a total of 24 test flights in the Zero between Sep. 26 and Oct. 15, noting in his subsequent report:

“These flights covered performance tests such as we do on planes undergoing Navy tests. The very first flight exposed weaknesses of the Zero which our pilots could exploit with proper tactics … immediately apparent was the fact that the ailerons froze up at speeds above 200 knots so that rolling maneuvers at those speeds were slow and required much force on the control stick. It rolled to the left much easier than to the right. Also, its engine cut out under negative acceleration due to its float-type carburettor. We now had the answer for our pilots who were being out-maneuvered and unable to escape a pursuing Zero. Go into a vertical power dive, using negative acceleration if possible to open the range while the Zero’s engine was stopped by the acceleration. At about 200 knots, roll hard right before the Zero pilot could get his sights lined up.”

Once the fighter had been sent to NAS Anacostia in late 1942, a series of test flights were performed by the Naval Air Station’s Flight Test Director, Cdr Frederick M. Trapnell. He flew identical flight profiles in both the Zero and US fighters to compare their performance, executing similar aerial maneuvers in mock dogfights. US Navy test pilot Lt Melvin C. “Boogey” Hoffman was also checked out in the A6M2, after which he helped train Naval Aviators flying new F6F Hellcats, F4U Corsairs and FM Wildcats by dogfighting with them in the Zero.

In 1943 the aircraft was tested in NACA’s LMAL in Hampton, Virginia, where the facility’s Full-Scale Wind Tunnel was used to evaluate the Zero’s aerodynamic qualities. It was also shown off to the public at Washington National Airport that same year during a war booty exhibition. By September 1944 the well-used A6M2 was stationed at NAS North Island once again, where it served as a training aid for “green” Naval Aviators preparing for duty in the Pacific. Koga’s Zero finally met its demise in a training mishap on or about Feb. 10, 1945, when the fighter was hit by a Curtiss SB2C Helldiver while being taxied at NAS North Island with Cdr Richard Crommelin at the controls. The dive-bomber suffered from very poor forward visibility, and its pilot failed to see the Zero until its propeller had started cutting chunks out of its fuselage. The A6M2 was subsequently scrapped, apart from a wingtip and some cockpit instruments that are now displayed in the Navy Museum at the Washington Navy Yard in Washington, D.C.

Wings of the Rising Sun is published by Osprey Publishing and is available to order here.


Re-evaluating the A6M Zero – Why was it unarmored?

Much has been said about the Zero’s lack of survivability features, however, most evaluations fail to elucidate on the underlying reasons for the Zero not having cockpit armor or self-sealing fuel tanks until the development of the later models. While indeed, the lack of such features was a serious drawback for the Zero, aviation historian Osamu Tagaya notes that the reasons are often misconstrued by westerners. Rather than being a design oversight, the real reasons for the Zeros lack of protective features stems from operational philosophies & contemporary attitudes, lack of experience and false conclusions, organizational deficiencies, technological limitations, and finally, psychological and cultural values (Mikesh, 1994, p. 103).

Operational Philosophies, Contemporary Attitudes, Lack of Experience, & False Conclusions

We must understand that in the mid-1930s, neither aircraft designers nor air force officers foresaw the need for self-sealing fuel tanks or armor in aircraft at the time. In fact, none of the Zeros contemporaries in the late-1930s, such as the Wildcat, Hurricane, Spitfire, or Bf-109E, initially had sealing tanks or armor either. The change in attitudes in the West was not due to someone’s farsightedness, but rather the harsh realities of combat during the Battle of Britain. Such features didn’t become standard until the latter half of 1940. Around the same time, and into 1941, U.S. aircraft began having these features installed. Unfortunately, Japan did not heed the lessons that western nations learned in the Battle of Britain and instead drew the wrong conclusions from the Second Sino-Japanese War where they developed a sense of arrogance and superiority given the weak nature of the air opposition in the skies over China. While Japanese experience in China did see some combat units request protective features, it was not until the stiff opposition during the Guadalcanal campaign that Japan felt the urgency. It wasn’t until late-1943 that the Zero began having a level of protection that U.S. aircraft already had by mid-1942. By then, the advantage had been hopelessly lost (Mikesh, 1994, p. 104 – 106).

In Jiro Horikoshi’s words (regarding adding armor to the Model 52c AKA A6M5c):

The most significant request was bulletproofing, a feature which had not even been mentioned in the Zero’s initial planning requirements. Over the years, the lack of bulletproofing has frequently been mentioned as a weak point of the Zero. The reason for this shortcoming was that the aircraft could not afford the additional weight necessary for bulletproofing, given the requirements stipulated with respect to heavy armament, long range capability, and maneuverability. These items took priority over anything else, and since we did not have reliable high-power engines, bulletproofing was sacrificed. Japanese pilots of those days had a feeling similar to that which must have been experienced by skillful samurai who single handedly fought many well-protected enemies. This attitude on the part of the pilots accelerated the general trend of assigning a low priority to bulletproofing. Certainly, if one type of aircraft demonstrated overwhelming offensive ability, this in itself could become a major defensive force. But as our opponents’ offensive abilities approached or even exceeded our own, an unskilled pilot or one who was outnumbered needed the additional protection of bulletproofing (Horikoshi, 1981, p. 144).

While aviation is not my field of expertise, it is important to put the concept of aircraft armor into context. Aircraft are not armored like tanks or fortresses. What is gained in weight is lost in speed and agility. According to Mark Peattie (2001), designing a combat aircraft is a trade-off between weight, speed, ceiling, range, maneuverability, armor, armament, and any number of other variables (p. 91). Cockpit armor is largely a pilot survival feature. Remember that the Zero was designed as a fighter plane and not a ground attack aircraft. Ground attack aircraft like the Il-2 Sturmovik or the modern A-10 Thunderbolt II are designed to fly low and slow and expected to be targeted by enemy anti-aircraft fire. Hence, they are built with armor, redundant systems, and are generally very rugged in construction. The Zero, and many fighter aircraft including modern ones, favor speed and agility. True, many Allied fighter planes did incorporate some armor for survivability, but their ability to withstand punishment and return to base was also the result of their very rugged designs. There are historical instances of aircraft taking seemingly ridiculous amounts of damage and still being able to bring the pilot back safely. Grumman Aircraft Corporation was famously known as the “Grumman Iron Works” for consistently designing very rugged and reliable planes.

Organizational Deficiencies & Technological Limitations

The design requirements for the Zero set forth by the Navy were seemingly contradictory. Horikoshi and his team worked tirelessly to create a lightweight fighter that possessed impressive range and maneuverability. However, sacrifices had to be made in several areas. While a superb design, the Zero possessed many single-point failure points where structural failure would result in complete destruction of the aircraft. Furthermore, while the Zero’s climb rate was unprecedented at the time, its dive speed was relatively slow, a problem that would put it at a disadvantage later in the Pacific War with the introduction of heavier and faster Allied fighters. The legendary maneuverability of the Zero was only notable in slow-turning dogfights below 4,500 meters (15,000 feet). Pilots noted that at its maximum speed of 288 knots at 4,500 meters, the ailerons stiffened and the plane became extremely sluggish (Peattie, 2001, p. 92).

Regarding the industrial capabilities in Japan, we must remember that in contrast to the technologically advanced Japan that we see today, the Japan of the 1930s and 40s was still an agrarian and light-industrial society that was being ruled from the top down by a totalitarian regime. Japan emerged from feudalism in 1868, and in less than 100 years, they had bridged the technological gap, but only due to the imposition of industrialization from the government, and only in certain areas. While Japan could produce some internationally competitive products, the standard of living and economic infrastructure still lagged significantly behind the West. Tagaya compares the Japan at the time to the Soviet Union or many present-day Third World countries. As a result of Japan’s industrial limitations, they could not produce a high-grade rubber of consistent quality necessary for self-sealing tanks which delayed their development (Mikesh, 1994, p. 106).

Horikoshi further attributes the problems with the Zero mainly to its “underpowered engine.” He mentions that in Japan, it was standard procedure to prioritize certain design elements. Thus, “it was natural for a fighter not to be bulletproofed” (Horikoshi, 1981, p. 151). He goes on to say:

Priorities varied between different aircraft types. For example, a bomber could not maneuver to avoid the bullets of an enemy fighter in daytime combat, regardless of top speed. Consequently, bulletproofing should have been a high priority item for a bomber. In the case of a fighter, the pilot’s skill and the performance of the airplane could compensate for the lack of bulletproofing to some extent. In short, bulletproofing was a low priority for a fighter, but it became more important as pilot skill decreased and as the number of enemy fighters increased (p. 151).

Finally, Horikoshi mentions a memo from the Navy Aeronautics HQ written 1 year and 5 months after the start of the war which mentioned the need for bulletproofing in the future. However, he says that:

In those days, the consensus still seemed to be that the advantages of improved maneuverability and increased offensive firepower with a lighter aircraft made it inadvisable to weigh a fighter down with bulletproofing. In the future, bulletproofing would be clearly necessary, but for the present its absence resulted from our efforts to strengthen offensive firepower. As a matter of fact, only when the United States stepped up the counterattack and introduced new, powerful fighters in overwhelming numbers did bulletproofing become essential (p. 151).

Psychological & Cultural Values

Japanese cultural values may also explain why the Japanese took longer to address the problem of aircraft protection. The samurai psyche still pervaded Japanese society, particularly the military, which demanded an acceptance of an honorable death. While irrational by today’s Japanese standards, anything that hinted at trying to save one’s skin, such as armor plating, was seen as cowardly. Additionally, Japanese aviators often demanded the most out of their aircraft, thus any additional weight that would reduce its performance was dismissed. The underlying attitude was that such protective features were luxuries rather than necessities. Only after the wholesale attrition of the pilots did they finally see that living to fight another day was more important in modern warfare than dying an honorable death (Mikesh, 1994, p. 106).

Conclusion

In summation, according to Horikoshi, why did the Zero not have armor and self-sealing tanks?

  1. It was never mentioned in the initial design requirements. (indeed, he never once brings it up earlier in the book when he is discussing the design of the Zero).
  2. Weight restrictions meant the prioritization of armament, range, and maneuverability for the fighter.
  3. Lack of a high-powered engine meant weight had to be saved.
  4. Military ethos assigned a low priority to armor.
  5. Lack of credible enemy air threats early on meant armor was not thought to be needed until later on.

As can be seen, the design requirements of the Zero favored creating a fighter plane with excellent handling characteristics.

This is actually a good lesson in the evaluation of historical evidence. We do have Horikoshi’s memoir to go off of here, so that provides us with a strong primary source, albeit, published 30 years after the fact. We should be careful of using the benefit of hindsight to project our evaluation onto the decisions that were initially made. This is known as hindsight bias. We should also be careful of creating a negative proof here. Just because there is no evidence that the Zero’s designers or the navy considered adding armor or self-sealing tanks, does not mean that they never did. Rather, we could say that we have found a low correlation of the fact that they did not consider adding such features to the initial design. Furthermore, it is difficult to establish this beyond any reasonable doubt because valid empirical proof would require the establishment of possibility and probability. The evidence must be relevant and in the affirmative. We cannot just say that X was possibly the case, rather we must also establish that it probably was and present relevant evidence. Horikoshi does state that weight restrictions meant the prioritization of armament, range, and maneuverability, but we have not established that any one of those was the most probable factor on why they left out armor and self-sealing tanks. Many other components of the Zero were sacrificed to meet those requirements and we also see that there was an entire ethos embodied in the design philosophy.


3 Eventual Capture

The Allied forces tried for so long, without success, to capture an intact Zero. They needed to study the aircraft's working to understand its flaws and how other planes could defeat it. Mid-1942, the allies got their wish. By 1943, Japan's opponents had understood the concept behind the A6M and built fighters with more robust engines and better protection that could outrun and overpower them.

via The National Interest

The loss of many experienced Japanese pilots also took its toll, as many of the junior pilots lacked the technical knowledge to fly the aircraft successfully.

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