The Hellcat-Zero Myth

Several World War II historians have perpetuated a myth that should be laid to rest: that the design of Grumman’s outstanding F6F Hellcat fighter plane was based on secrets learned from a Japanese Zero found almost intact in the Aleutians in 1942. In truth, the Hellcat was flying before the Zero was recovered.

The Japanese attempt to capture Midway Island included a diversionary attack on the Aleutians. During the attack, on 3 June 1942, Petty Officer Tadayoshi Koga was killed when he crash-landed his Zero on Akutan Island. The plane was discovered about five weeks later and shipped to the United States for repair and testing. It arrived in San Diego in August, and the repairs were completed in October.*

By that time, two models of the F6F had flown. The XF6F-1 first flew on 26 June 1942. On 30 July, the XF6F-3 took to the air, and on 4 October, the first production F6F-3 made its maiden flight. (The XF6F-3 had a more powerful engine. The F6F-1 was powered by a Wright R-2600-16 rated at 1,700 horsepower; the F6F-3 was powered by a Pratt & Whitney R-2800-8, rated at 2,000 horsepower.)

Of course, the F6F design work dates much earlier. The Grumman specifications for the XF6F-1 were dated 24 February 1941, and those of the F6F-3, 1 August 1941. The contact for the XF6F-1 was signed on 30 June 1941 and the production order for the F6F-3 on 23 May 1942.

Despite this chronology, some histories tell us that the Hellcat design was based on Koga’s Zero. The book Miracle at Midway says American engineers “rushed to their drawing boards” to come up with a match for the Zero. A biography of Japan’s Admiral Isoroku Yamamoto claims, “Immediately blueprints were got out” for what became the Hellcat. How did this myth get started?

Following the trail of the authors’ footnotes and bibliographies, one comes at last to a work by two Japanese. The book Zero! was written by Masatake Okumiya and Jiro Horikoshi, in collaboration with American writer Martin Caidin, and published in 1956 by E. P. Dutton. Okumiya was a veteran flying officer in the Japanese Navy. He was a staff officer of carrier forces in most of the major air-sea battles in the Pacific from 1942 to 1944. In the last year of the war he was put in command of Japan’s homeland air defense. Horikoshi was the aeronautical engineer who designed the Zero.

The authors say that after Koga’s Zero was studied in the United States, “ ... the Americans rushed to completion a fighter airplane intended specifically to wrest from Japan the advantage afforded by the Zero. This was the United States Navy’s Grumman F6F Hellcat. . . .” The phrase “rushed to completion” might imply that production was speeded up on a plane already being built. But the authors didn’t mean that, for they also say: “The F6F was the first plane designed by the Grumman company following their thorough study of the captured Zero fighter.”

Okumiya and Horikoshi seem to hedge a little later in the book. Discussing the Hellcat’s combat debut in September 1943, they write: “Our first reports on the new Grumman stated that its design had been affected by a careful American examination of a Zero fighter captured in the Aleutians in the spring of 1942. To some extent this appeared to be so, since the philosophy of weight-saving was carried throughout the Hellcat’s structure to an extent without parallel in other American aircraft of that time.” [Emphasis added.]

No matter to what extent the reports were true, Okumiya and Horikoshi believed the recovery of Koga’s Zero had an important bearing on the outcome of the war. Okumiya was Rear Admiral Kakuji Kakuda’s air staff officer during the Aleutians campaign. “I could not realize at the time,” he writes, “how far-reaching an effect this seemingly trivial incident of losing to the enemy a single intact Zero could have. We felt strongly that the unnoticed capture of the airplane, assisting the enemy so greatly in producing a fighter plane intended specifically to overcome the Zero’s advantages, did much to hasten our final defeat.”

If Zero! was the start of the myth, how did it spread?

John Deane Potter picked up the story in 1965 in his book Yamamoto: The Man Who Menaced America, (New York: The Viking Press) giving it a separate chapter, “The Lost Fighter.” Potter writes: “Grumman engineers studied the captured Zeke [the U. S. name for the Zero] with their operational experience gained from the Wildcat [the F4F]. Immediately blueprints were got out for a fighter containing all the Zeke’s advantages—and none of its weaknesses. They reduced the thickness of the fuselage and made every effort to cut down weight. This Zeke adaptation became the U. S. Navy’s Grumman F6F Hellcat.”

Potter lists Zero! in his bibliography and obviously relies heavily on it. His reference to fuselage and weight closely follows Okumiya and Horikoshi, who write: “Grumman engineers painstakingly reduced the thickness of the fuselage, and bent every effort to reduce structural weight.” Potter also echoes the Japanese authors’ conclusion: “The seemingly trivial incident of losing a single intact Zeke had almost as long-term an effect on the Pacific war as the loss of (Vice Admiral Chuichi] Nagumo’s four carriers [in the battle of Midway]. The Japanese did not know the aircraft had been captured undamaged. It gave the Americans a unique peep at one of the best, most secret fighters of the war. When they began to manufacture a fighter specifically guaranteed to overcome the fast maneuverable Zekes they did much to hasten Japan’s final defeat.”

Four years later, the myth surfaced again, this time in a book about the Aleutians campaign, Brian Garfield’s The Tliousand-Mile War (Garden City, New York: Doubleday, 1969). Garfield recounts the crash and recovery of the Zero and writes: “This apparently trivial loss cost Japan dearly. American engineers with this opportunity to fly and study the war’s fastest, deadliest and most secret fighter, would design the Navy’s F6F Hellcat around the principles they learned from Koga’s Zero. In less than 18 months, the Hellcat would drive the Zero from the Pacific skies.” Garfield lists Potter’s Yamamoto in his bibliography. He does not list Zero! but says he did consult the book. He also said, in a letter to this author, that he heard about the Zero-Hellcat connection “from several veteran pilots who seemed to take it as gospel.”

The myth is repeated in another book still in the book stores, Gordon W. Prange’s Miracle at Miday (New York: McGraw-Hill Book Company, 1982), edited by Donald M. Goldstein and Katherine V. Dillon. In Prange’s version, after the Zero was tested in the United States, “the American aircraft designers rushed to their drawing boards to come up with a fighter which at last could put the Indian sign on the legendary Zero. The answer was the Grumman F6F Hellcat, which outclassed the Zero in almost every department.”

Where did Prange get the story? From Okumiya-Horikoshi and Potter.

And now the tale lives on in Ronald H. Spector’s Eagle Against The Sun: The American War with Japan (New York: The Free Press, 1985). Spector’s version: “In less than eighteen months American engineers, studying and testing the captured Zero, would produce their own deadlier version: the F6F Hellcat.” Where did Spector get the story? He cites only Garfield’s The Thousand-Mile War.

And so the myth spreads. Can it be stopped? Perhaps. We can hope that future historians writing on the Pacific war will learn the truth and decide, “The myth stops here!”

Changing the Hellcat’s Engine

Lieutenant Commander Abe Vosseller was a very, very sharp aviation engineer. He wasn't an aeronautical engineering duty officer (AEDO); he was a line officer, but he had a lot of experience and training in engineering work. He was in overall charge of the engineering development of new fighters. In 1942, he was working very closely with Lieutenant Commander George Anderson, the future CNO, in the Plans Division of the Bureau of Aeronautics.

At the time, the AEDOs had come up with a new Wright engine which was slated to go into the F6F Hellcat. It wasn’t adequate in power. However, we did have another engine, the R-2800-8, built by Pratt and Whitney. We always had better luck with Pratt and Whitney than we did with Wright.

The R-2800-8 was a very, very fine engine and had developed no bugs at all as it had been progressing in its tests. Abe Vosseller and George Anderson got the idea that this would be the ideal engine for the F6F. They talked it over with AEDOs, who took a dim view all around and would have nothing to do with it, saying, “It’s too much engine for that airplane,” and so on and so forth. So then they went up to Bethpage and talked to the people at Grumman, to Roy Grumman primarily. He was willing to take all the responsibility for putting the Pratt and Whitney in the airplane and having his own test pilots work it out. But he couldn’t get one. The engine was government-furnished equipment, and he had to take whatever engine the Navy gave him to put in his airplane.

Believe it or not, George Anderson and Abe Vosseler essentially stole one of the new engines. There weren’t many of them in existence at the time, but they sent some sort of a message to Pratt and Whitney that a truck would be sent to pick up one of the engines for experimental purposes. The inspector there was to divert one. They got a Navy truck and driver, sent it to Pratt and Whitney, got the engine and took it from their plant down to Grumman. The engine went into the F6F, and then Roy Grumman had his test pilots “wring it out. ” The improvement in the performance was phenomenal— the difference between day and night.

After receiving the figures from Roy, Vosseller and George Anderson went to Rear Admiral John Towers, Chief of the Bureau of Aeronautics, and said, “The AEDOs have said not to do this. But we know this is the engine that is right for the F6F. Here are the figures, but we’ll never convince them.” So they dropped the performance figures in his hands, and before the morning was out the designation of the engine for the Hellcat was changed to the R-2800-8. That’s how the Pratt and Whitney engine got into the F6F.

From the Naval Institute oral history of Vice Admiral Herbert L. Riley, USN (Ret.)