Aviation History

The story of Koga’s Zero, the captured A6M that helped the F6F Hellcat become the most effective carrier fighter of World War II

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 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.

US military personnel inspect a Japanese Zero aircraft piloted by Tadayoshi Koga that crashed on Akutan Island after bombing Dutch Harbor on June 4, 1942.

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.

Koga’s Zero at the NACA Langley Reserch Center in Hampton Virginia, in March 1943.

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.

US Navy Lieutenant Commander Eddie Sanders taxis Koga’s Zero at Naval Air Station San Diego, California in September 1942.

Photo credit: U.S. Navy

Dario Leone

Dario Leone is an aviation, defense and military writer. He is the Founder and Editor of “The Aviation Geek Club” one of the world’s most read military aviation blogs. His writing has appeared in The National Interest and other news media. He has reported from Europe and flown Super Puma and Cougar helicopters with the Swiss Air Force.

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