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122-656: The Akutan Zero , also known as Koga's Zero (古賀のゼロ) and the Aleutian Zero , was a type 0 model 21 Mitsubishi A6M Zero Japanese fighter aircraft piloted by Petty Officer Tadayoshi Koga, that crash-landed on Akutan Island , Alaska Territory , during World War II . It was found intact by the Americans in July 1942 and became the first Zero acquired by the United States during the war that could be restored to airworthy condition. It

244-548: A Warren truss layout — riveted onto the spars, resulting in a substantial increase in structural strength at a time when most other aircraft designs were built almost completely with wood-structure wings. The Junkers all-metal corrugated-covered wing / multiple tubular wing spar design format was emulated after World War I by American aviation designer William Stout for his 1920s-era Ford Trimotor airliner series, and by Russian aerospace designer Andrei Tupolev for such aircraft as his Tupolev ANT-2 of 1922, upwards in size to

366-452: A general aviation aircraft usually consists of a sheet aluminium spar web, with L- or T-shaped spar caps being welded or riveted to the top and bottom of the sheet to prevent buckling under applied loads. Larger aircraft using this method of spar construction may have the spar caps sealed to provide integral fuel tanks . Fatigue of metal wing spars has been an identified causal factor in aviation accidents, especially in older aircraft as

488-529: A raid of Chongqing , attacked 34 Soviet-built Polikarpov I-15s and I-16s of the Chinese Nationalist Air Force , claimed "all 27" of the Chinese fighters shot down without loss to themselves. However Major Louie Yim-qun had in fact nursed his I-15 riddled with 48 bullet holes back to base, and Lieutenant Gao Youxin claimed to have shot down one Zero, but at most 4 Zeroes sustained some damage in

610-645: A ball of fire by now. When the Lockheed P-38 Lightning , armed with four "light barrel" AN/M2 .50 cal. Browning machine guns and one 20 mm autocannon , and the Grumman F6F Hellcat and Vought F4U Corsair , each with six AN/M2 .50 calibre Browning guns, appeared in the Pacific theater, the A6M, with its low-powered engine and lighter armament, was hard-pressed to remain competitive. In combat with an F6F or F4U,

732-520: A cost of increased complexity and difficulty of packaging additional equipment such as fuel tanks, guns, aileron jacks, etc.). Although multi-spar wings have been used since at least the 1930s (for example, the World War 2-era Curtiss P-40 had 3 spars per wing), they gained greater popularity when the increasing speed of jet fighters demanded thinner wings to reduce drag at high speeds. The Mach 2 F-104 Starfighter used numerous slender spars to allow for

854-513: 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. While stable on the ground despite its light weight, the aircraft was designed purely for the attack role, emphasizing long range, maneuverability, and firepower at the expense of protection of its pilot. Most lacked self-sealing tanks and armor plating. Captain Eric Brown ,

976-431: A good rate of roll. Another important maneuver was Lieutenant Commander John S. "Jimmy" Thach 's " Thach Weave ", in which two fighters would fly about 60 m (200 ft) apart. If a Zero latched onto the tail of one of the fighters, the two aircraft would turn toward each other. If the Zero followed his original target through the turn, he would come into a position to be fired on by the target's wingman. This tactic

1098-405: A knife. They searched it for anything with intelligence value, and buried Koga in a shallow grave near the crash site. Thies returned with his team to Dutch Harbor, where he reported the plane as salvageable. The next day (July 12), a salvage team under Lieutenant Robert Kirmse was dispatched to Akutan. This team gave Koga a Christian burial in a nearby knoll and set about recovering the plane, but

1220-435: A maximum speed of 565 km/h (351 mph) at 6,000 m (20,000 ft), reaching that altitude in 7:01 minutes. Subsequent variants included: Some Model 21 and 52 aircraft were converted to "bakusen" ( fighter-bombers ) by mounting a bomb rack and 250 kg (550 lb) bomb in place of the centerline drop tank. Up to seven Model 52 planes were ostensibly converted into A6M5-K two-seat trainers. Mass production

1342-578: A mystery. Three other downed Zeros were available to the Allies before the Akutan Zero was recovered. In February 1942, a Zero (serial number 5349) piloted by Hajime Toyoshima crashed on Melville Island in Australia after the bombing of Darwin ; it was heavily damaged. Another Zero, piloted by Yoshimitsu Maeda, crashed near Cape Rodney, New Guinea . The team sent to recover the plane erred when they chopped off

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1464-678: A part of Mitsubishi Heavy Industries . It was operated by the Imperial Japanese Navy (IJN) from 1940 to 1945. The A6M was designated as the Mitsubishi Navy Type 0 carrier fighter ( 零式艦上戦闘機 , rei-shiki-kanjō-sentōki ) , or the Mitsubishi A6M Rei-sen. The A6M was usually referred to by its pilots as the Reisen ( 零戦 , zero fighter), "0" being the last digit of the imperial year 2600 (1940) when it entered service with

1586-501: A prototype plane exists. It shows a turbo unit mounted in the forward left fuselage. Lack of suitable alloys for use in the manufacture of a turbo-supercharger and its related ducting caused numerous ruptures, resulting in fires and poor performance. Consequently, further development of a turbo-supercharged A6M was cancelled. The lack of acceptance by the Navy suggests that it did not bestow model number 41 or 42 formally, although it appears that

1708-450: A small loop of high wing over which placed them out of reach and in position for another attack. By reversing the turn sharply after each attack the leader may get a shot at the enemy while he is climbing away or head on into a scissor if the Jap turns to meet it. In contrast, Allied fighters were designed with ruggedness and pilot protection in mind. The Japanese ace Saburō Sakai described how

1830-563: A two-blade propeller. It first flew on 1 April, and passed testing within a remarkably short period. By September, it had already been accepted for Navy testing as the A6M1 Type 0 Carrier Fighter, with the only notable change being a switch to a three-bladed propeller to cure a vibration problem. While the Navy was testing the first two prototypes, they suggested that the third be fitted with the 700 kW (940 hp) Nakajima Sakae 12 engine instead. Mitsubishi had its own engine of this class in

1952-532: A wing of unusually thin section; the F-16 Fighting Falcon uses a similar construction. Other aircraft like the F-4 Phantom , F-15 Eagle and others use 3 or more spars to give sufficient strength in a relatively thin wing, and thus qualify as multi-spar aircraft. False spars, like main spars, are load bearing structural members running spanwise but are not joined to the fuselage. Their most common purpose

2074-570: Is that the F4F-4 is even more sluggish and slow than the F4F-3. It is also felt that it was a mistake to put 6 guns on the F4F-4 and thus to reduce the rounds per gun. Many of our fighters ran out of ammunition even before the Jap dive bombers arrived over our forces; these were experienced pilots, not novices. They were astounded by the Zero's superiority: In the Coral Sea, they made all their approaches from

2196-467: The ASG 29 . The increase in strength and reduction in weight compared to the earlier fibreglass-sparred aircraft allows a greater quantity of water ballast to be carried. Aircraft utilizing three or more spars are considered multi-spar aircraft. Using multiple spars allows for an equivalent overall strength of wing, but with multiple, smaller, spars, which in turn allow for a thinner wing or tail structure (at

2318-571: The BD-5 , which was designed and constructed by Jim Bede in the early 1970s. The spar used in the BD-5 and subsequent BD projects was primarily aluminium tube of approximately 2 inches (5.1 cm) in diameter, and joined at the wing root with a much larger internal diameter aluminium tube to provide the wing structural integrity. In aircraft such as the Vickers Wellington , a geodesic wing spar structure

2440-581: The Battle of the Coral Sea , such as Jim Flatley , and the Battle of Midway, such as Jimmy Thach ; their input was obtained during a meeting with Grumman Vice President Jake Swirbul at Pearl Harbor on 23 June 1942. The first production F6F-3 made its first flight just over three months later, on October 3, 1942. While the captured Zero's tests did not drastically influence the Hellcat's design, they did impart knowledge of

2562-622: The China Burma India Theater by the " Flying Tigers " of the American Volunteer Group (AVG) against similarly maneuverable Japanese Army aircraft such as the Nakajima Ki-27 "Nate" and Nakajima Ki-43 "Oscar" . AVG pilots were trained by their commander Claire Chennault to exploit the advantages of their P-40 Warhawks , which were very sturdy, heavily armed, generally faster in a dive, and level flight at low altitude, with

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2684-453: The Extra 300 when performing extreme aerobatic manoeuvers; the spars of these aircraft are designed to safely withstand great load factors . Early aircraft used spars often carved from solid spruce or ash . Several different wooden spar types have been used and experimented with such as spars that are box-section in form; and laminated spars laid up in a jig , and compression glued to retain

2806-715: The Polikarpov I-16s and I-153s that had been such a problem for the A5Ms when in service. In one encounter, 13 Zeros shot down 27 I-15s and I-16s in under three minutes without loss. After hearing of these reports, the Navy immediately ordered the A6M2 into production as the Type 0 Carrier Fighter, Model 11. Reports of the Zero's performance slowly filtered back to the US. They were met with scepticism by most US military officials, who thought it impossible for

2928-528: The Shumagin Islands , he reoriented his plane and began to return to Dutch Harbor by the most direct course: over Akutan Island. Machinist Mate Albert Knack, who was the plane captain (note: the term "plane captain" in US Navy usage refers to an aircraft's assigned maintenance crew chief, not the pilot-in-command), spotted Koga's wreck. Thies's plane circled the crash site for several minutes, noted its position on

3050-592: The 1/2 hour-long dogfight over Chongqing. By the time they were redeployed a year later, the Zeros had shot down 99 Chinese aircraft (up to 266 according to other sources). At the time of the attack on Pearl Harbor , 521 Zeros were active in the Pacific, 328 in first-line units. The carrier-borne Model 21 was the type encountered by the Americans. Its tremendous range of over 2,600 kilometres (1,600 mi) allowed it to range farther from its carrier than expected, appearing over distant battlefronts and giving Allied commanders

3172-478: The A6M during the Second Sino-Japanese War . Inevitably some aircraft were lost, with at least two falling more-or-less intact into Chinese hands. The first known example, an A6M2 (the 12th of the 15 pre-production aircraft, Serial V-110), fell near Fainan Island. On 18 September 1940 a team, including Western volunteers assisting the Chinese, examined the wreck. It was largely intact, and a detailed report

3294-516: The A6M's levels of maneuverability and consistently exceeding its firepower, armor, and speed, the A6M had largely become outdated as a fighter aircraft. However, as design delays and production difficulties hampered the introduction of newer Japanese aircraft models, the Zero continued to serve in a front-line role until the end of the war in the Pacific . During the final phases, it was also adapted for use in kamikaze operations. Japan produced more Zeros than any other model of combat aircraft during

3416-642: The Akutan Zero and recently commissioned USN pilots flying newer Navy aircraft. Later in 1943, the aircraft was displayed at Washington National Airport as a war prize. In 1944, it was recalled to North Island for use as a training plane for rookie pilots being sent to the Pacific. A model 52 Zero, captured during the liberation of Guam , was later used as well. Data and conclusions from these tests were published in Informational Intelligence Summary 59 , Technical Aviation Intelligence Brief #3 , Tactical and Technical Trends #5 (published prior to

3538-588: The Allied Technical Air Intelligence Unit 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

3660-584: 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 and improved close maneuverability. American test pilots found that the Zero's controls were "very light" at 320 km/h (200 mph) but stiffened at speeds above 348 km/h (216 mph) to safeguard against wing failure. The Zero could not keep up with Allied aircraft in high-speed maneuvers, and its low " never exceed speed " (V NE ) made it vulnerable in

3782-528: The Battle of Midway Allied pilots expressed a high level of dissatisfaction with the F4F Wildcat . Captain Elliott Buckmaster , commanding officer of USS  Yorktown notes: The fighter pilots are very disappointed with the performance and length of sustained fire power of the F4F-4 airplanes. The Zero fighters could easily outmaneuver and out-climb the F4F-3, and the consensus of fighter pilot opinion

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3904-606: The F6F airframe to incorporate the 2,000 hp (1,500 kW) R-2800-10 engine, driving a three-bladed Hamilton Standard propeller. With this combination, Grumman estimated the XF6F-3's performance would surpass that of the XF6F-1 by 25%. This first Double Wasp-equipped Hellcat airframe, bearing BuAer serial number 02982, first flew on 30 July 1942. The F6F-3 subtype had been designed with specific "Wildcat vs Zero" input from F4F pilots who fought in

4026-518: 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

4148-531: The IJN. The official Allied reporting name was " Zeke ", although the name "Zero" was used colloquially as well. The Zero is considered to have been the most capable carrier-based fighter in the world when it was introduced early in World War II , combining excellent maneuverability and very long range. The Imperial Japanese Navy Air Service also frequently used it as a land-based fighter. In early combat operations,

4270-503: The Imperial Navy, and "M" indicated Mitsubishi as the manufacturer. The official Allied code name 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

4392-591: The Japanese Midway operation, the Japanese attacked the Aleutian islands , off the south coast of Alaska . A Japanese task force led by Admiral Kakuji Kakuta bombed Dutch Harbor on Unalaska Island twice, once on June 3 and again the following day. Tadayoshi Koga (September 10, 1922 – June 4, 1942), a 19-year-old flight petty officer first class , was launched from the Japanese aircraft carrier Ryūjō as part of

4514-438: The Japanese to build such an aircraft. After the delivery of the 65th aircraft, a further change was worked into the production lines, which introduced folding wingtips to allow them to fit on aircraft carriers. The resulting Model 21 would become one of the most produced versions early in the war. A feature was the improved range with 520 L (140 US gal) wing tank and 320 L (85 US gal) drop tank. When

4636-492: The June 4 raid. Koga was part of a three-plane section; his wingmen were Chief Petty Officer Makoto Endo and Petty Officer Tsuguo Shikada. Koga and his comrades attacked Dutch Harbor, and are believed to be the three Zeroes that shot down an American PBY-5A Catalina flying boat piloted by Bud Mitchell, and strafed its survivors in the water, killing Mitchell and all six of his crewmen. In the process, Koga's plane (serial number 4593)

4758-598: The Model 32 was unsuited to that campaign and was used mainly for shorter range offensive missions and interception. This variant was flown by only a small number of units, and only 343 were built. One example survives today, and is on display at the Tachiarai Peace Memorial Museum in Tachiarai, Fukuoka . In order to correct the deficiencies of the Model 32, a new version with folding wingtips and redesigned wing

4880-461: The Model 52. Mitsubishi is unable to state with certainty that it ever used the designation "A6M4" or model numbers for it. However, "A6M4" does appear in a translation of a captured Japanese memo from a Naval Air Technical Arsenal, titled Quarterly Report on Research Experiments, dated 1 October 1942. It mentions a "cross-section of the A6M4 intercooler" then being designed. Some researchers believe "A6M4"

5002-471: The Navy, it was flight tested by Frederick M. Trapnell , the Anacostia Naval Air Station director of flight testing. He flew the Akutan Zero in performance maneuvers while Sanders simultaneously flew American planes performing identical maneuvers, simulating aerial combat. Following these, USN test pilot Lieutenant Melvin C. "Boogey" Hoffman conducted more dogfighting tests between himself flying

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5124-467: The PBY Catalina squadron that discovered the Zero and later rose to the rank of admiral, said that Koga's Zero was "of tremendous historical significance". William N. Leonard concurred: "The captured Zero was a treasure. To my knowledge, no other captured machine has ever unlocked so many secrets at a time when the need was so great." Some historians dispute the degree to which the Akutan Zero influenced

5246-450: The Sakae 21 engine, which used a two-speed supercharger for better altitude performance, and increased power to 831 kW (1,130 hp). A prototype Zero with the new engine was first flown on 15 July 1941. The new Sakae was slightly heavier and somewhat longer due to the larger supercharger, which moved the center of gravity too far forward on the existing airframe. To correct for this,

5368-607: The United States. The Second Sino-Japanese War began in 1937. Attacks by Chinese fighter planes on Japanese bombers led the Japanese to develop the concept of fighter escorts . The limited range of the Mitsubishi A5M "Claude" fighter used to escort the bombers caused the Japanese Navy Air staff to commission the Mitsubishi A6M Zero as a long-range land- and carrier-based fighter. The Zero, which first flew in 1939,

5490-457: The XF6F-1's first flight, and based on combat accounts of encounters between the F4F Wildcat and A6M Zero, on 26 April 1942, BuAer directed Grumman to install the more powerful 18-cylinder Pratt & Whitney R-2800 Double Wasp radial engine—already powering Chance Vought's Corsair design since its beginnings in 1940—in the second XF6F-1 prototype. Grumman complied by redesigning and strengthening

5612-568: The Zero gained a reputation as a dogfighter , achieving an outstanding kill ratio of 12 to 1, but by mid-1942 a combination of new tactics and the introduction of better equipment enabled Allied pilots to engage the Zero on generally equal terms. By 1943, the Zero was less effective against newer Allied fighters. The Zero lacked hydraulic boosting for its ailerons and rudder, rendering it difficult to maneuver at high speeds. Lack of self-sealing fuel tanks also made it more vulnerable than its contemporaries. By 1944, with Allied fighters approaching

5734-591: The Zero in most respects, except range, without sacrificing pilot armor, self-sealing fuel tanks, and a sturdy fuselage structure. The new F6F Hellcat would compensate for the extra weight with additional power. On September 20, 1942, two months after the Zero's capture, Lieutenant Commander Eddie R. Sanders took the Akutan Zero up for its first test flight. He made 24 test flights between September 20 and October 15. According to Sanders' report: These flights covered performance tests such as we do on planes undergoing Navy tests. The very first flight exposed weaknesses of

5856-481: The Zero was an aerodynamic impossibility. With the coming of war, the U.S. fighting services learned better; the Zero's maneuverability outperformed any Allied fighter it encountered for the first two years of the war. According to American flying ace William N. Leonard , "In these early encounters and on our own we were learning the folly of dogfighting with the Zero". To achieve this dogfighting agility, however, Japanese engineers had traded off durability. The Zero

5978-415: 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 . Combined with its light weight, this resulted in a very low stalling speed of well below 60 kn (110 km/h; 69 mph). This was the main reason for its phenomenal maneuverability, allowing it to out-turn any Allied fighter of

6100-410: 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 carburetor . We now had

6222-420: The Zero's handling characteristics, including its limitations in rolling right and diving. That information, together with the improved capabilities of the Hellcat, were credited with helping American pilots "tip the balance in the Pacific". American aces Kenneth A. Walsh and R. Robert Porter, among others, credited tactics derived from this knowledge with saving their lives. James Sargent Russell , who commanded

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6344-493: The Zero. American author Jim Rearden led a search on Akutan in 1988 in an attempt to repatriate Koga's body. He located Koga's grave, but found it empty. Rearden and Japanese businessman Minoru Kawamoto conducted a records search. They found that Koga's body had been exhumed by an American Graves Registration Service team in 1947, and re-buried on Adak Island , further down the Aleutian chain. The team, unaware of Koga's identity, marked his body as unidentified. The Adak cemetery

6466-439: The acquisition of the Akutan Zero "was no less serious" than the Japanese defeat at the Battle of Midway , and that it "did much to hasten Japan's final defeat". Nonetheless, historian John Lundstrom and others challenge "the contention that it took dissection of Koga's Zero to create tactics that beat the fabled airplane". The Akutan Zero was destroyed in a training accident in 1945. Parts of it are preserved in several museums in

6588-524: The acrobatic Japs", as Lieutenant General Claire Lee Chennault noted. Although not as fast as the British fighter, the Zero could out-turn the Spitfire with ease, sustain a climb at a very steep angle, and stay in the air for three times as long. Allied pilots soon developed tactics to cope with the Zero. Because of its extreme agility, engaging a Zero in a traditional turning dogfight was likely to be fatal. It

6710-470: The answer for our pilots who were being outmaneuvered 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. In early 1943, the Zero was transferred from Naval Air Station North Island to Anacostia Naval Air Station . The Navy wished to make use of

6832-454: The arsenal did use the designation "A6M4". The prototype engines nevertheless provided useful experience for future engine designs. Sometimes considered as the most effective variant, the Model 52 was developed to again shorten the wings to increase speed and dispense with the folding wing mechanism. In addition, ailerons, aileron trim tab and flaps were revised. Produced first by Mitsubishi, most Model 52s were made by Nakajima. The prototype

6954-405: The attack against Dutch Harbor the previous day (June 3). Rearden noted, "It seems likely that in the near half-century after the event Shikada's memory confused the raids of June 3 and June 4 ... It also seems likely that in his interview, Shikada employed selective memory in not mentioning shooting down Mitchell's PBY and then machine-gunning the crew on the water". It is not known who fired

7076-551: The attack in December 1941, and United States Office of Naval Intelligence , along with BuAer had them studied, and then shipped to the Experimental Engineering Department at Dayton, Ohio in 1942. It was noted that the experimental Grumman XF6F-1s then undergoing testing in June 1942 and the Zero had "wings integrated with the fuselage," an unusual design feature in American aircraft of the day. The Akutan Zero

7198-542: The chief naval test pilot of the Royal Navy , recalled being impressed by the Zero during tests of captured aircraft. "I don't think I have ever flown a fighter that could match the rate of turn of the Zero. The Zero had ruled the roost totally and was the finest fighter in the world until mid-1943." The first two A6M1 prototypes were completed in March 1939, powered by the 580 kW (780 hp) Mitsubishi Zuisei 13 engine with

7320-490: The destroyer USS  Williamson . ( Note : The description above is solely based on "Koga's Zero" by American author Jim Rearden. See .) The crash site, which was out of sight of standard flight lanes and not visible by ship, remained undetected and undisturbed for over a month. On July 10, 1942, an American PBY Catalina piloted by Lieutenant William "Bill" Thies spotted the wreckage. Thies's Catalina had been patrolling by dead reckoning and had become lost. On spotting

7442-401: The distance between the spar caps. Even in modern times, "homebuilt replica aircraft" such as the replica Spitfires use laminated wooden spars. These spars are laminated usually from spruce or douglas fir (by clamping and glueing). A number of enthusiasts build "replica" Spitfires that will actually fly using a variety of engines relative to the size of the aircraft. A typical metal spar in

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7564-427: The engine mountings were cut back by 185 mm (7.3 in) to move the engine toward the cockpit. This had the side effect of reducing the size of the main fuselage fuel tank (located between the engine and the cockpit) from 518 L (137 US gal) to 470 L (120 US gal). The cowling was redesigned to enlarge the cowl flaps, revise the oil cooler air intake, and move the carburetor air intake to

7686-674: The experiences of the A5M in China, the IJN sent out updated requirements in October, calling for a speed of 270 kn (310 mph; 500 km/h) at 4,000 m (13,000 ft) and a climb to 3,000 m (9,800 ft) in 9.5 minutes. With drop tanks , the IJN wanted an endurance 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

7808-601: The expertise of the NACA Langley Research Center in flight instrumentation, and it was flown to Langley on March 5, 1943, for the installation of the instrumentation. While there, it underwent aerodynamic tests in the Full-Scale Wind Tunnel under conditions of strict secrecy. This work included wake surveys to determine the drag of aircraft components; tunnel scale measurements of lift, drag, control effectiveness; and sideslip tests. After its return to

7930-480: The fabled airplane. To them the Zero did not long remain a mystery plane. Word quickly circulated among the combat pilots as to its particular attributes. Indeed on 6 October while testing the Zero, Akutan Zero test pilot Frederick M. Trapnell made a highly revealing statement: 'The general impression of the airplane is exactly as originally created by intelligence—including the performance'. Nine wrecked Mitsubishi A6M Zeros were recovered from Pearl Harbor shortly after

8052-728: The first test flight), and Informational Intelligence Summary 85 . These results tend to somewhat understate the Zero's capabilities. Data from the captured aircraft were submitted to the BuAer and Grumman for study in 1942. The U.S. carrier -borne fighter plane that succeeded the Grumman F4F Wildcat , the F6F Hellcat , was tested in its first experimental mode as the XF6F-1 prototype with an under-powered Wright R-2600 Twin Cyclone 14-cylinder, two-row radial engine on 26 June 1942. Shortly before

8174-695: The form of the Kinsei , so they were somewhat reluctant to use the Sakae. Nevertheless, when the first A6M2 was completed in January 1940, the Sakae's extra power pushed the performance of the Zero well past the original specifications. The new version was so promising that the Navy had 15 built and shipped to China before they had completed testing. They arrived in Manchuria in July 1940, and first saw combat over Chongqing in August. There they proved to be completely untouchable by

8296-578: The impression that there were several times as many Zeros as actually existed. The Zero quickly gained a fearsome reputation. Thanks to a combination of unsurpassed maneuverability—compared to contemporary Axis fighters—and excellent firepower, it easily disposed of Allied aircraft sent against it in the Pacific in 1941. It proved a difficult opponent even for the Supermarine Spitfire . "The RAF pilots were trained in methods that were excellent against German and Italian equipment but suicide against

8418-424: The island was a Japanese submarine assigned to pick up downed pilots. At Akutan, the three Zeros circled a grassy flat half a mile inland from Broad Bight. Shikada thought the ground was firm beneath the grass, but in his second pass he noticed water glistening. He suddenly realized Koga should make a belly landing . But by then Koga had lowered his landing gear and was almost down. The plane's landing gear mired in

8540-431: The lack of heavy equipment (which they had been unable to unload after the delivery ship lost two anchors) frustrated their efforts. On July 15, a third recovery team was dispatched. This time, with proper heavy equipment, the team was able to free the Zero from the mud and haul it overland to a nearby barge , without further damaging it. The Zero was taken to Dutch Harbor, turned right-side up, and cleaned. The Akutan Zero

8662-463: 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 ; 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

8784-601: The lines switched to updated models, 740 Model 21s had been completed by Mitsubishi, and another 800 by Nakajima. Two other versions of the Model 21 were built in small numbers, the Nakajima-built A6M2-N "Rufe" floatplane (based on the Model 11 with a slightly modified tail), and the A6M2-K two-seat trainer of which a total of 508 were built by Hitachi and the Sasebo Naval Air Arsenal. In 1941, Nakajima introduced

8906-433: The map, and returned to Dutch Harbor to report it. Thies persuaded his commanding officer, Paul Foley , to let him return with a salvage team. The next day (July 11), the team flew out to inspect the wreck. Navy photographer's mate Arthur W. Bauman took pictures as they worked. Thies's team extracted Koga's body from the plane by having Knack (the smallest crew member) crawl up inside the plane and cut his safety harness with

9028-509: The new design type was accepted formally by the Navy, the A6M3 Model 22 already stood ready for service in December 1942. Approximately 560 aircraft of the new type had been produced in the meantime by Mitsubishi Jukogyo K.K. According to a theory, the very late production Model 22 might have had wings similar to the shortened, rounded-tip wing of the Model 52. One plane of such arrangement was photographed at Lakunai Airfield ("Rabaul East") in

9150-405: The new style of exhaust commenced with number 3904. Whether this is correct, indicates retrofitting intentions, refers to the prototype but not to all subsequent planes, or is in error, is unclear.) From production number 4274, the wing fuel tanks received carbon dioxide fire extinguishers . From number 4354, the radio became the Model 3, aerial Mark 1, and at that point it is said the antenna mast

9272-495: The only positive thing that could be said of the Zero at this stage of the war was that, in the hands of a skillful pilot, it could maneuver as well as most of its opponents. Nonetheless, in competent hands, the Zero could still be deadly. Because of shortages of high-powered aviation engines and problems with planned successor models, namely the superior Mitsubishi A7M2 Reppū , the Zero remained in production until 1945, with over 10,000 of all variants produced. The Japanese deployed

9394-463: The outcome of the air war in the Pacific. For example, the Thach Weave , a tactic created by John Thach and used with great success by American airmen against the Zero, was devised by Thach before the attack on Pearl Harbor, based on intelligence reports on the Zero's performance in China. The capture and flight tests of Koga's Zero is usually described as a tremendous coup for the Allies as it revealed

9516-426: The plane revealed it was hit with small arms fire: .50 caliber bullet holes and smaller, from both above and below. The fatal shot severed the return oil line, and Koga's plane immediately began trailing oil. Koga reduced speed to keep the engine from seizing for as long as possible. The three Zeros flew to Akutan Island, 25 miles east of Dutch Harbor, which had been designated for emergency landings. Waiting near

9638-532: The quality of the aircraft, less so by the performance—although this was later put down to using 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, the Akutan Zero , on Akutan Island in the Aleutians . During an air raid over Dutch Harbor on 4 June 1942, one A6M fighter

9760-592: The rear or high side and did relatively little damage because of our armor. It also is desired to call attention to the fact that there was an absence of the fancy stunting during pull outs or approaches for attacks. In this battle, the Japs dove in, made the attack and then immediately pulled out, taking advantage of their superior climb and maneuverability. In attacking fighters, the Zeros usually attacked from above rear at high speed and recovered by climbing vertically until they lost some speed and then pulled on through to complete

9882-514: The reduced drag allowed the diving speed to be increased to 670 km/h (415 mph). On the downside, turning and range, which were the strengths of the Model 21, suffered due to smaller ailerons, decreased lift and greater fuel consumption. The shorter range proved a significant limitation during the Solomons Campaign, during which Zeros based at Rabaul had to travel nearly to their maximum range to reach Guadalcanal and return. Consequently,

10004-469: The requirements could be met, but only if the aircraft were made as light as possible. Every possible weight-saving measure was incorporated into the design. Most of the aircraft was built of a new top-secret aluminium alloy developed by Sumitomo Metal Industries in 1936. Called " extra super duralumin ", it was lighter, stronger and more ductile than other alloys used at the time but was prone to corrosive attack, which made it brittle. This detrimental effect

10126-465: The second half of 1943, and has been published widely in a number of Japanese books. While the engine cowling is the same of previous Model 32 and 22, the theory proposes that the plane is an early production Model 52. The Model 32, 22, 22 Kō, 52, 52 Kō and 52 Otsu were all powered by the Nakajima Sakae Mod. 21 engine. That engine kept its designation in spite of changes in the exhaust system for

10248-442: The secrets of that mysterious aircraft and led directly to its downfall. According to this viewpoint, only then did Allied pilots learn how to deal with their nimble opponents. The Japanese could not agree more... Yet those naval pilots who fought the Zero at Coral Sea , Midway, and Guadalcanal without the benefit of test reports would beg to differ with the contention that it took dissection of Koga's Zero to create tactics that beat

10370-427: The shot that brought down Koga's plane, although numerous individuals have claimed credit. Photographic evidence strongly suggests it was hit by ground fire. Members of the 206th Coast Artillery Regiment , which had both 3-inch anti-aircraft guns and .50-caliber machine guns in position defending Dutch Harbor, claimed credit, in addition to claims made by United States Navy ships that were present. Physical inspection of

10492-400: The standard United States Navy fighter of the time. 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

10614-410: The then-gigantic Maksim Gorki of 1934. A design aspect of the Supermarine Spitfire wing that contributed greatly to its success was an innovative spar boom design, made up of five square concentric tubes that fitted into each other. Two of these booms were linked together by an alloy web, creating a lightweight and very strong main spar. A version of this spar construction method is also used in

10736-520: The time. Early models were fitted with servo tabs on the ailerons after pilots complained that control forces became too heavy at speeds above 300 kilometres per hour (190 mph). They were discontinued on later models after it was found that the lightened control forces were causing pilots to overstress the wings during vigorous maneuvers. The A6M is usually known as the "Zero" from its Japanese Navy aircraft_type designation , Type 0 carrier fighter ( Rei shiki Kanjō sentōki , 零式艦上戦闘機 ), taken from

10858-435: 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

10980-509: The upper half of the cowling. The wings were redesigned to reduce span, eliminate the folding tips, and square off the wingtips. The inboard edge of the aileron was moved outboard by one rib, and the wing fuel tanks were enlarged accordingly to 420 L (110 US gal). The two 20 mm wing cannon were upgraded from the Type 99 Mark 1 to the Mark 2, which required a bulge in the sheet metal of

11102-476: The war. The Mitsubishi A5M fighter was just entering service in early 1937, when the Imperial Japanese Navy started looking for its eventual replacement. On 5 October 1937, it issued "Planning Requirements for the Prototype 12-shi Carrier-based Fighter", sending them to Nakajima and Mitsubishi. Both firms started preliminary design work while awaiting more definitive requirements a few months later. Based on

11224-615: The water and mud, causing the plane to flip upside down and skid to a stop. Although the aircraft survived the landing nearly intact, Petty Officer Koga died instantly on impact, probably from a broken neck or a blunt-force blow to his head. Koga's wingmen, circling above, had orders to destroy any Zeros that crash-landed in enemy territory, but as they did not know if Koga was still alive, they could not bring themselves to strafe his plane. They decided to leave without firing on it. The Japanese submarine stationed off Akutan Island to pick up pilots searched for Koga in vain before being driven off by

11346-667: The wing dihedral . Wooden spars are still being used in light aircraft such as the Robin DR400 and its relatives. A disadvantage of the wooden spar is the deteriorating effect that atmospheric conditions, both dry and wet, and biological threats such as wood-boring insect infestation and fungal attack can have on the component; consequently regular inspections are often mandated to maintain airworthiness . Wood wing spars of multipiece construction usually consist of upper and lower members, called spar caps , and vertical sheet wood members, known as shear webs or more simply webs , that span

11468-479: The wing below each cannon. The wings also included larger ammunition boxes and thus allowing 100 rounds per cannon. The Sakae 21 engine and other changes increased maximum speed by only 11 km/h (6.8 mph) compared to the Model 21, but sacrificed nearly 1,000 km (620 miles) of range. Nevertheless, the Navy accepted the type and it entered production in April 1942. The shorter wingspan led to better roll, and

11590-403: The wing rigidity needed to enable the aircraft to fly safely. Biplanes employing flying wires have much of the flight loads transmitted through the wires and interplane struts enabling smaller section and thus lighter spars to be used at the cost of increasing drag . Some of the forces acting on a wing spar are: Many of these loads are reversed abruptly in flight with an aircraft such as

11712-419: The wings, severing the wing spars and rendering the hulk unflyable. The third came from China, where Gerhard Neumann reconstructed a working aircraft from a partly intact Zero (serial number 3372) that had landed in Chinese territory plus salvaged pieces from other downed Zeros. Neumann's aircraft did not reach the United States for testing until after the recovery of the Akutan Zero. In June 1942, as part of

11834-511: Was applied to one or two prototype planes fitted with an experimental turbo-supercharged Sakae engine designed for high altitude. Mitsubishi's involvement in the project was probably quite limited or nil; the unmodified Sakae engine was made by Nakajima. The design and testing of the turbo-supercharger was the responsibility of the First Naval Air [Technical] Arsenal ( 第一海軍航空廠 , Dai Ichi Kaigun Kōkūshō ) at Yokosuka. At least one photo of

11956-505: Was better to swoop down from above in a high-speed pass, fire a quick burst, then climb 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 Guadalcanal defense through high-altitude ambush, which was possible with an early warning system consisting of coastwatchers and radar . Such "boom-and-zoom" tactics were also successfully used in

12078-433: Was compiled and sent to the U.S. The second, an A6M2-21 (Serial V-173), made a forced landing near Tietsan airfield 17 February 1941. The pilot was shot before he could destroy his plane, the fuel system fixed, and it was taken into Chinese service. The plane was extensively flown and studied by a team which included Gerhard Neumann , and a detailed and illustrated report was sent to Washington. Overall they were impressed with

12200-502: Was contemplated by Hitachi, but not undertaken. The A6M6 was developed to use the Sakae 31a engine, featuring water-methanol engine boost and self-sealing wing tanks. During preliminary testing, its performance was considered unsatisfactory due to the additional engine power failing to materialize and the unreliability of the fuel injection system. Testing continued on the A6M6 but the end of war stopped further development. Only one prototype

12322-799: Was countered with a zinc chromate anti-corrosion 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 , which were becoming common among other combatants, were not used. This made the Zero lighter, more maneuverable, and one of the longest-ranged single-engine fighters of World War II, which made it capable of searching out an enemy hundreds of kilometres away, bringing it to battle, then returning to its base or aircraft carrier. However, that tradeoff 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 landing gear , and enclosed cockpit,

12444-461: Was damaged by small arms fire. Tsuguo Shikada, one of Koga's wingmen, published an account in 1984 in which he claimed the damage to Koga's plane occurred while his section was making an attack against two American Catalinas anchored in the bay. This account omits any mention of shooting down Mitchell's PBY. Both American and Japanese records contradict his claims; there were no PBYs in the bay that day. However, his claims do match American records from

12566-690: Was destroyed during a training accident in February 1945. While the Zero was taxiing for a take-off, a Curtiss SB2C Helldiver lost control and rammed into it. The Helldiver's propeller sliced the Zero into pieces. From the wreckage, William N. Leonard salvaged several gauges, which he donated to the National Museum of the United States Navy . The Alaska Heritage Museum and the Smithsonian National Air and Space Museum also have small pieces of

12688-547: Was dressed and re-used." The Zero's red Hinomaru roundel was repainted with the American blue-circle-white-star insignia. The whole time, the plane was kept under 24-hour military police guard in order to deter would-be souvenir hunters from damaging the plane. The Zero was fit to fly again on September 20. Data from the captured Zero had been transmitted to the U.S. Navy's Bureau of Aeronautics (BuAer) and Grumman Aircraft . After careful study, Roy Grumman decided that he could design an aircraft that could match or surpass

12810-614: Was employed, which had the advantages of being lightweight and able to withstand heavy battle damage with only partial loss of strength. Many modern aircraft use carbon fibre and Kevlar in their construction, ranging in size from large airliners to small homebuilt aircraft . Of note are the developments made by Scaled Composites and the German glider manufacturers Schempp-Hirth and Schleicher . These companies initially employed solid fibreglass spars in their designs but now often use carbon fibre in their high performance gliders such as

12932-585: Was excavated in 1953, and 236 bodies were returned to Japan. The body buried next to Koga (Shigeyoshi Shindo) was one of 13 identified; the remaining 223 unidentified remains were cremated and interred in Chidorigafuchi National Cemetery in Japan. It is probable that Koga was one of them. Mitsubishi A6M Zero The Mitsubishi A6M " Zero " is a long-range carrier-capable fighter aircraft formerly manufactured by Mitsubishi Aircraft Company ,

13054-511: Was exceedingly agile and lightweight, with maneuverability and range superior to any other fighter in the world at that time. In 1940 Claire Lee Chennault , leader of the Flying Tigers , wrote a report to warn his home country of the Zero's performance. However, United States Department of War analysts rejected the Chennault report as "arrant nonsense" and concluded the performance attributed to

13176-652: Was first used to good effect during the Battle of Midway and later over the Solomon Islands . Many highly experienced Japanese aviators were lost in combat, resulting in a progressive decline in pilot quality, which became a significant factor in Allied successes. Unexpected heavy losses of pilots at the Battles of the Coral Sea and Midway dealt the Japanese carrier air force a blow from which it never fully recovered. Throughout

13298-411: Was found over a month later by an American salvage team and was shipped to Naval Air Station North Island , where testing flights of the repaired A6M revealed both strengths and deficiencies in design and performance. The experts who evaluated the captured Zero found that the plane weighed about 2,360 kg (5,200 lb) fully loaded, some 1,260 kg (2,780 lb) lighter than the F4F Wildcat,

13420-484: Was hit by ground-based anti-aircraft fire. Losing oil, Flight Petty Officer Tadayoshi Koga attempted an emergency landing on Akutan Island about 20 miles (32 km) northeast of Dutch Harbor, but his Zero flipped over on soft ground in a sudden crash-landing. Koga died instantly of head injuries (his neck was broken by the tremendous impact), but his wingmen hoped he had survived and so went against Japanese doctrine to destroy disabled Zeros. The relatively undamaged fighter

13542-507: Was initially called "Hap". General "Hap" Arnold , commander of the United States Army Air Forces , objected to that name, however, so it was changed to "Hamp". The first Zeros (pre-series of 15 A6M2) went into operation with the 12th Rengo Kōkūtai in July 1940. On 13 September 1940, the Zeros scored their first air-to-air victories when 13 A6M2s led by Lieutenant Saburo Shindo, escorting 27 G3M "Nell" medium-heavy bombers on

13664-410: Was introduced. The fuel tanks were moved to the outer wings, fuel lines for a 330 L (87 US gal) drop tank were installed under each wing and the internal fuel capacity was increased to 570 L (150 US gal). More importantly, it regained its capabilities for long operating ranges, similar to the previous A6M2 Model 21, which was vastly shortened by the Model 32. However, before

13786-483: Was loaded onto the USS ; St. Mihiel and transported to Seattle, arriving on August 1. From there, it was transported by barge to Naval Air Station North Island near San Diego where repairs were carefully carried out. These repairs "consisted mostly of straightening the vertical stabilizer, rudder, wing tips, flaps, and canopy. The sheared-off landing struts needed more extensive work. The three-blade Sumitomo propeller

13908-538: Was made in June 1943 by modifying an A6M3 and was first flown in August 1943. The first Model 52 is said in the handling manual to have production number 3904, which apparently refers to the prototype. Research by Mr. Bunzo Komine published by Mr. Kenji Miyazaki states that aircraft 3904 through 4103 had the same exhaust system and cowl flaps as on the Model 22. This is partially corroborated by two wrecks researched by Mr. Stan Gajda and Mr. L. G. Halls, production number 4007 and 4043, respectively. (The upper cowling

14030-482: Was produced. Spar (aeronautics) Spars are also used in other aircraft aerofoil surfaces such as the tailplane and fin and serve a similar function, although the loads transmitted may be different from those of a wing spar. The wing spar provides the majority of the weight support and dynamic load integrity of cantilever monoplanes , often coupled with the strength of the wing 'D' box itself. Together, these two structural components collectively provide

14152-537: Was repaired and flown by American test pilots. As a result of information gained from these tests, American tacticians were able to devise ways to defeat the Zero, which was the Imperial Japanese Navy 's primary fighter plane throughout the war. The Akutan Zero has been described as "a prize almost beyond value to the United States", and "probably one of the greatest prizes of the Pacific War ". Japanese historian and JASDF lieutenant general Masatake Okumiya stated that

14274-476: Was shortened slightly. Through production number 4550, the lowest exhaust stacks were approximately the same length as those immediately above them. This caused hot exhaust to burn the forward edge of the landing gear doors and heat the tires. Therefore, from number 4551 Mitsubishi began to install shorter bottom stacks. Nakajima manufactured the Model 52 at its Koizumi plant in Gunma Prefecture . The A6M5 had

14396-439: Was slightly redesigned from that of the Model 22. ) An early production A6M5 Zero with non-separated exhaust, with an A6M3 Model 22 in the background. A new exhaust system provided an increment of thrust by aiming the stacks aft and distributing them around the forward fuselage. The new exhaust system required "notched" cowl flaps and heat shields just aft of the stacks. (Note, however, that the handling manual translation states that

14518-411: Was the case with Chalk's Ocean Airways Flight 101 . The German Junkers J.I armoured fuselage ground-attack sesquiplane of 1917 used a Hugo Junkers -designed multi-tube network of several tubular wing spars, placed just under the corrugated duralumin wing covering and with each tubular spar connected to the adjacent one with a space frame of triangulated duralumin strips — usually in the manner of

14640-430: Was the primary Japanese Navy fighter throughout the war. During the war, the Japanese manufactured roughly 10,500 Zeros. Nine Zeros were shot down during the attack on Pearl Harbor . From these wrecks, the Allies learned that the Zero lacked armor and self-sealing fuel tanks, but little else about its capabilities. The Zero's flight performance characteristics—crucial to devising tactics and machinery to combat it—remained

14762-435: Was to be mounted in all aircraft, along with a radio direction finder for long-range navigation. The maneuverability was to be at least equal to that of the A5M, while the wingspan had to be less than 12 m (39 ft) to allow for use on aircraft carriers. Nakajima's team considered the new requirements unachievable and pulled out of the competition in January. Mitsubishi's chief designer, Jiro Horikoshi , thought that

14884-465: Was very lightly built; it had no armor and no self-sealing fuel tanks . According to American author Jim Rearden , "The Zero was probably the easiest fighter of any in World War II to bring down when hit ... The Japanese ... were not prepared to or weren't capable of building more advanced fighters in the numbers needed to cope with increasing numbers and quality of American fighters". The Zero

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