ZERO TYPE HISTORY

MITSUBISHI A6M ‘ZERO’

The most widely known and most successful Japanese combat aircraft of all time, its layout and large wing make this an attractive and practical subject for scale modelling

In early 1937, the elliptical-winged, fi xed and bespatted undercarriage Mitsubishi A5M fi ghter was just entering service, when the Imperial Japanese Navy (IJN) began to defi ne the specifi cation for that aircraft’s eventual replacement.

In October that year, it issued “Planning

Requirements for the Prototype 12-shi

Carrier-based Fighter”, to the leading

Japanese aircraft manufacturers,

Nakajima and Mitsubishi, and both fi rms started preliminary design work while they awaited receipt of more defi nitive requirements, expected in a few months.

Based on the experiences of the A5M in China, the IJN issued an update calling for a speed of 310 mph (500 km/h) at 4,000 m (13,000 ft.) and a climb to 9,800 ft (3,000 m) in 9.5 minutes. The specifi cation required an endurance (with drop tanks) of two hours at normal power, or six to eight hours at economical cruising speed. Armament was to consist of two 20 mm cannons, two 7.7 mm (.303 in) machine guns and two 60 kg (130 lb.) bombs.

A complete radio set was to be mounted in all aircraft, along with a radio direction fi nder for long-range navigation. The manoeuvrability was to be at least equal to that of the A5M, while the wingspan had to be less than 12 m (39 ft.) to enable the aircraft to be ‘struck down’ into the hangar decks of existing Japanese carriers.

Nakajima’s team considered the new requirements unachievable and withdrew

A formation of Mitsubishi A6M3 Model 22 Zeros of the 251st Kokutai over the Solmon

Islands in the South Pacifi c, east of Australia (though by a considerable distance). The two aircraft in the foreground display extensive fuselage weathering and all in the formation carry the centreline auxiliary fuel tank that enabled the lightweight fi ghter to to deliver air strikes over very long distances.

from the competition in thje following January, but Mitsubishi’s chief designer, Jiro Horikoshi, thought that the requirements could be met, but only if the aircraft were made as light as possible.

Thus, every possible weight-saving measure was incorporated into the new design; so that most of the aircraft was to be built of a new top-secret aluminium alloy that had been developed by Sumitomo Metal Industries in 1936. Called “extra super duralumin” (ESD), it was lighter, stronger and more ductile than other existing alloys used at the time, but was prone to corrosive attack, which made it brittle. This detrimental effect was countered with an anticorrosion coating applied after fabrication.

No armour protection was provided for the pilot, engine or other critical points of the aircraft and self-sealing fuel tanks, both of which were becoming common among the Air Forces of Western powers.

All of this concentration on weight saving made the Zero lighter, more manoeuvrable, and the longest-ranged single-engine fighter of World War II, which made it capable of searching out an enemy hundreds of miles away, bringing it to battle, then returning to its base or aircraft carrier. However, that trade-off in weight and construction also made it prone to catching fire and exploding when struck by enemy fire.

With its low-wing cantilever monoplane layout, retractable, wide-set conventional main undercarriage and enclosed cockpit, the Zero was one of the most modern carrier-based aircraft in the world at the time of its introduction. It had a fairly high-lift, low-speed wing with very low wing loading, resulting in a particularly low stalling speed of tess that 69 mph (110 km/h). Its low airframe weight was the main reason for its phenomenal manoeuvrability, allowing it to out-turn any Allied fighter of the time. WHAT’S IN A NAME?

The A6M is usually known as the “Zero” from its Japanese Navy type designation, Type 0 carrier fighter (Rei shiki Kanjō sentōki), taken from the last digit of the Imperial year 2600 (1940) when it entered service. In Japan, it was unofficially referred to as both Rei-sen and Zero-sen, but Japanese pilots most commonly called it Zero-sen, where sen is the first syllable of sentōki, Japanese for “fighter plane”.

In the official designation “A6M”, the “A” signified a carrier-based fighter, “6” meant that it was the sixth such model built for the Imperial Navy, and “M” indicated Mitsubishi as the manufacturer.

The official Allied code name subsequently applied to the type was “Zeke”, in keeping with the practice of giving male names to Japanese fighters, female names to bombers, bird names to gliders, and tree names to trainers. “Zeke” was part of the first batch of “hillbilly” code names assigned by Captain Frank T. McCoy of Nashville, Tennessee (assigned to the Allied Technical Air Intelligence Unit (ATAIU) at Eagle Farm Airport in Australia), who wanted quick, distinctive, easy-to-remember names.

The Allied code for Japanese aircraft was introduced in 1942, and McCoy chose “Zeke” for the “Zero”. Later, two variants of the fighter received their own code names. The Nakajima A6M2-N floatplane version of the Zero was called “Rufe”, and the A6M3-32 variant was initially called “Hap”. Perhaps unsurprising, General Henry “Hap” Arnold, commander of the USAAF at the time, objected to that name, so it was changed to “Hamp”.

FIRST ACTIONS

The first Zeros (pre-series of 15 A6M2) became operational in China in July 1939, even prior to the commencement of war in Europe and well before Japan’s entry into WW2. In September 1940, Zeros based in China scored their first air-toair victories when 13 A6M2s led by Lieutenant Saburo t

Forerunner to the A6M Zero, was the Mitsubishi A5M, that commenced air operations in China during 1937. With open cockpit and spatted main undercarriage, the type bears chronological comparrison roughtly with the Boeing P-26, although the A5M is much more aerodynamically clean, with elliptical wings, devoid of wire wing bracing. Bulge under the wing centreline is an early form of auxilliary fuel tank.

Warming up for a mission from the Japanese Home Island of Kyushu, these A6M5 Model 52c Zeros each carry very long centreline auxilliary fuel tanks.

The scene on the flght deck of the IJN Fleet Carrier Shokaku during the Battle of

Santa Cruz, Solomon Islands in lat October 1942 as the A6M2 of Lt. Hideki Shingo begins its takeoff run. In the ‘air-exhange’ of the battle for the possession of the vital Henderson Field on Guadalcanal, Solomon Islands. Shokaku and the light

carrier Zuiho suffered significant damage, while the USS fleet carrier Hornet was

sunk and the USS Enterprise heavily damaged.

A pair of early A6M2 Model 11s of the 12th Kokutai en-route to a target somewhere in China, during May 1941.

The scene on the rear deck of IJN carrier Shokaku as the air strike force prepares to launch during the Battle of Santa Cruz. Aircraft in the foreground are A6M2 Zeros, while further back are Aichi D3A ‘Val’ dive bombers. In the immediate aftermath of the December 7th, 1941 air attack against the USN anchorage at Pearl Harbour, Hawiian Islands, Japanes forces quickly struck south, down the Malayan peninsula, and

across the widely spread islands of the central Pacific and Oceana. Few such island outposts had pre-prepared landing grounds for aircraft. Here the Mitsubishi A6M2-N floatplane fighter, developed

during late 1940 became an important tool.

Shindo, escorting 27 G3M “Nell” mediumheavy bombers on a raid of Chunking. Attacked by 34 Soviet-built Polikarpov I-15s and I-16s of the Chinese Nationalist Air Force, the Japanese unit involved claimed “all 27” of the Chinese fighters shot down without loss to themselves, in the half-hour long dogfight over Chunking. By the time they were redeployed a year later, this Zero equipped unit had claimed more than a hundred such victories.

At the time of the attack on Pearl Harbour in December 1941, 521 Zeros were active in the Pacific, 328 of them in first-line units. The carrier-borne Model 21 was the type first encountered by the Americans. Its tremendous range of over 2,600 kilometres (1,600 mi) allowed it to range further from its carrier than expected, appearing over distant battlefronts and giving Allied commanders the impression that there were several times as many Zeros as actually existed.

SURPRISE, SURPRISE…

Because of Western prejudices (and assumed racial superiority), the performance of the A6M came as something of a painful surprise, the revelation acquired through the capture of two examples, in China, where the Sino-Japanese war had been in train since 1937. The first was a wreck, recovered in late summer 1940 while the other, an intact flyable example, was captured in early 1941, before Japan and USA were at war. This windfall had made clear to anyone who would pay attention, the manufacturing quality and performance of the A6M.

The second example was extensively flown and studied by a team that had included naturalised German-American Gerhard Neumann, who had volunteered his air-mechanic experience to the Chinese after moving to USA in 1938 and who, in later life, became a senior executive of General Electric Aviation Engine Division. Neumann’s contribution to the analysis of the captured Zero included a detailed and illustrated report that was sent to Washington.

Overall, inspectors were impressed with the quality of the machine, less so by the performance - although this was later put down to the use of 85-octane fuel rather than the 100 octane required by the Sakae engine.

The American Military discovered many of the A6M’s unique attributes when they recovered a largely intact specimen of an A6M2 on Akutan Island in the Aleutians. During an air raid over Dutch Harbour on 4 June 1942, one of the raiding Zero fighters was hit by ground-based anti-aircraft fire and crashed. The relatively undamaged fighter was found over a month later by an American salvage team. It was returned to full airworthiness for tests that revealed both strengths and deficiencies in design and performance.

The experts found that the A6M’s airframe was “built like a fine watch”; the Zero was constructed with flush rivets, and even the guns were flush with the wings. The instrument panel was a “marvel of simplicity… with no superfluities to distract the pilot”. What most impressed the experts was that the Zero’s fuselage and wings were constructed in one piece, unlike the American method that built them separately and joined the two parts together.

The Japanese method was much slower, but resulted in a very strong structure. American test pilots found that the Zero’s controls were “very light” at 200 mph (320 km/h), but stiffened at faster speeds above 216 mph (348 km/h). The Zero could not keep up with Allied aircraft in high-speed manoeuvres, and its low “never exceed speed” (VNE) made it vulnerable in a dive. Testing also revealed that the Zero could not roll as quickly to the right as it could to the left, which could be exploited. The aircraft was designed purely for the attack role, emphasizing long range, manoeuvrability, and firepower at the expense of protection for its pilot.

ZERO SUM-UP

The Zero quickly gained a fearsome reputation. Thanks to a combination of unsurpassed manoeuvrability compared to contemporary Allied fighters and to excellent firepower, it easily disposed of Allied aircraft sent against it in the Pacific during late 1941 and into 1942. It proved a difficult opponent even for the Super marine Spitfire when examples reached Australia, where these were deployed against Japanese carrier borne air strikes against Darwin, Northern Territory.

However Allied pilots soon developed tactics to cope with the Zero. Due to its extreme agility, engaging a Zero in a traditional, turning dogfight was likely to be fatal. It was better to swoop down from above in a high-speed pass, fire a quick burst, then zoom quickly back up to altitude. A short burst of fire from heavy machine guns or cannon was often enough to bring down the fragile Zero

These tactics were regularly employed by Grumman F4F Wildcat fighters during the 1942-3 Guadalcanal campaign through high-altitude ambush.

Many highly experienced Japanese aviators were lost in combat, resulting in a progressive decline in quality, which became a significant factor in Allied

ONE WAY TICKET: Thought to be the pre-takeoff ovation for the very first Kamikazi Special Attack strike by

members of the 201st Kokutai, this mixed group of A6M2s and A6M5s mostly carry centreline-attached bombs, but two have only centreline fuel tanks, so are likely to have been navigational escorts. Early

Kamikazi missions were voluntary, but later, ‘selection’ became an order.

BITTER END: Post-war boneyard of a wide range Japanese military aircraft, of which many are A6M Zeros. In the background, a number of Douglas C-47s of the US Occupying Forces can also be seen. successes. Unexpected heavy losses of pilots at the Sea/Air Battles of the Coral Sea and Midway dealt the Japanese carrier air force a blow from which it never fully recovered.

Nevertheless, on the American side throughout the Battle of Midway U.S. pilots expressed a high level of dissatisfaction with their F4F Wildcats, deemed very disappointing in performance and length of sustained firepower of the F4F-4 aircraft. The Zero fighters could easily outmanoeuvre and out-climb the F4F-3. Generally, they were astounded by the Zero’s superiority.

In contrast, Allied fighters were designed with ruggedness and pilot protection in mind. The Japanese ace Saburō Sakai described how the toughness of early Grumman aircraft was a factor in preventing the Zero from attaining 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 that had taken that many bullets would have been a ball of fire by now”.

TURNING OF THE TIDE

However, when the first variants of the powerfully armed Lockheed P-38 Lightning, armed with four .50 cal. Browning machine guns and one 20 mm cannon reached the Pacific war theatre, followed by the Grumman F6F Hellcat and Vought F4U Corsair, both with six .50 calibre Browning guns, the A6M, with its low-powered engine and lighter armament, was hard-pressed to remain competitive. In combat with an F6F or F4U, the only positive thing that could be said of the Zero at this stage of the war was that, in the hands of a skilful pilot, it could manoeuvre as well as most of its opponents. In competent hands, the Zero could still be deadly.

Last ‘full’ production version of the Zero was the A6M5, although further development included the A6M6 to wring further performance out of the basic design by applying water-methanol injection to an upgraded Sakae 31 engine and self sealing fuel tanks, but this progressed no further than prototype stage. Last to reach production and Service was the A6M7 which was a dedicated dive-bomber destined to feature on Kamikaze attacks.

Finally came the A6M8 with Mitsubishi Kinsei 62 engine. Two prototypes were completed in April 1945 but the by then chaotic situation of Japanese industry obstructed the start of the ambitious program of production for 6,300 A6M8s. Only the two prototypes being completed and flown before the war’s end

A total pf 10,934 Zeros of all variants were produced, of which the Nakajima Company produced the largest number – 6,215. The same Company also produces the A6M2-N floatplane with large centreline float and twin outrigger stabilisers under the wings, Allied codename -

The A6M Zero played a part in every battle where the Japanese Navy and Air Force were engaged and during the final stages of WW2, was the mainstay for Kamikaze attacks against. U.S. and British Pacific Fleets. n