Rubbish.
The association of the development of the Grumman F6F-3 with the restoration of #4593 A6M2 is one of the great urban legends of WWII. Nothing of the kind happened.
The Zero that crashed on Akutan Island was #4593. Its crash site was discovered by the crew of a PBY, piloted by Lieut. William Theis, on July 10, 1942, while on routine patrol.
The only USN/USMC fighter combat experience at with the A6M at the time that Koga’s plane was being recovered occurred with the VF squadrons that fought at Coral Sea, VF-2 and VF-42, and the VF and VMF squadrons at Midway, VF-3 (and 59% of the combat flying pilots in VF-3 were from VF-42), VF-6, VF-8, and VMF-221. By the time the F6F-1 was ready to take to the air, the after action reports from these actions had yet to be distributed. Further, having read those reports, I can safely say that there is not much in them at all that could possibly be of interest to a Grumman designer, especially since the F6F-1 was already built.
The “Aleutian Zero” was # 4593, recovered, loaded aboard the USS St Mihiel, then shipped to, and restored by US Navy personnel at North Island NAS, San Diego, California. Grumman, contrary to what one often finds on the internet, had absolutely nothing to do with the restoration. In fact, the Grumman plant was located at Bethpage, New York. The airplane arrived in San Diego from Alaska on August 12, 1942.
Once repairs were completed, it first flew with a USN pilot (Lt Cdr Eddie Sanders) on 20 September 1942. My father’s log book show that he flew this same airplane on 14 September 1944, 19 September, 14 October, 21 October, and 25 October 1944. It was destroyed in a taxiway accident in February 1945. My father salvaged the port wingtip and some instruments all of which he donated to the USN Museum at the Washington Navy Yard in 1986.
The US Navy asked Grumman to start the design of the F6F in June 1941 as a hedge against problems with the development of the Chance-Vought F4U which was scheduled to replace the Grumman F4F series. Grumman was already out of the starting blocks on this having begun studies on a concept for an improved F4F in early 1938; by 1940 the concept had received a company designation of G-50. The Navy’s order of 30 June 1941 was for two of the G-50 models, now designated as the XF6F-1 and the XF6F-2. As things turned out having Grumman design its own replacement for the F4F was a good idea as there were, indeed, development and deployment problems with the F4U.
The Grumman XF6F-1 first flew almost a year later, on 26 June 1942, (20 days after the Battle of Midway and 7 days after VF-3, VF-6, and VF-8 arrived back at Pearl Harbor), with a Wright R-2600 engine. Even at that time, it was already obvious to both the USN and Grumman that the 1600 hp R-2600, in either its R-2600-10 version in the XF6F-1 or its R-2600-16 version in the XF6F-2, was not going to provide the speed desired for the airplane. The solution, which Grumman had already identified, was a switch to the 2000 hp Pratt & Whitney R-2800 engine. The XF6F-1 flight with the R-2600-10 was essentially a test to verify what Grumman and the Navy already suspected - the need for more power. The XF6F-3, the re-designated XF6F-1 now mounting the R-2800 engine, first flew on 30 July 1942. This was 20 days before the Koga Zero arrived in San Diego and almost two months before A6M2 #4593 got into the air over North Island. The F6F-3 was version of the Hellcat that first entered combat and of which some 4403 were produced. The Navy, with remarkable prescience, placed its first order for the F6F-3 on 23 May 1942, before any version of the aircraft ever got in the air; a scant two weeks after USN fighter pilots had encountered the A6M2 for the first time at the Battle of the Coral Sea; and four months before the restored and repaired A6M2 #4593 ever got into the air over southern California.
Thus, the F6F was developed independent of the restoration of the A6M2 # 4593 and most, if not all of the basic design work accomplished long before the USN VF squadrons first ran into the A6M2 at the Battle of the Coral Sea in May 1942.
And even if there were a major design change based on some examination of the Koga Zero, something that would have caused a major change to performance, that would have required a contract change order (there isn’t one to my knowledge) and that would have required a nomenclature change, i.e., to F6F-4. There was only one F6F-4 (b/n 02981) modified from the original XF6F-1, but it was not a production model.
I have list of all the design changes over the operational history of the F6F, none of them relate to performance issues that could be traced to the Koga A6M2.
I have not only the combat reports for Coral Sea and Midway, but also BuAer interview transcripts of Jimmy Thach and Noel Gayler. The most you can get out of all these documents is that the F4F is inferior in climb, turn, and speed performance compared to the to the Zero. Big deal. Gayler’s interview was conducted on 17 June 1942, nine days before the XF6F-1 took to the air. Thach’s interview was on 28 August 1942, two days before the XF6F-3’s debut. There is nothing in the combat reports or the Gayler and Thach interviews that remotely suggest any specific engineering design considerations.
No, confident with Grumman’s design, the Navy ordered initial production work on the F6F on 20 June 1941 slightly more than a year before the first one ever took off. The first production order, for some Six months later, on January 7, 1942 when the Navy awarded a contract for 1,264 F6Fs; this was six months BEFORE the XF6F-3 ever flew. After that first flight (all done at the Bethpage NY facility) of the XF6F-3, the order was increased. Production, however, was somewhat delayed as Grumman did not have a building in which to set up the assembly line. Grumman had to stand in line for construction materials just like everyone else. Eventually, things started moving; in fact, work was started on production models with the roof and only three of the four walls of the F6F production facility, Plant Number 3, in place. The first production model F6F-3 (b/n 04775) flew on 3 October 1942, two weeks after Eddie Sanders took the air in the Koga Zero, and a short 4 days after his initial report was issued. VF-9 was the first squadron to get the F6F-3, taking their first delivery on 16 January 1943, a little over 18 months from the initial contract order. F6F-3 production increased rapidly. As you can see, there wasn’t a heck of a lot of time for design changes between the June test flight and the deliver of the first F6F-3 in October.
And, indeed, there were small tweaking changes made during the production runs, but they were superficial for the most part. I could list the changes, but that would just take up space. The big change was the change in engine, R2800-10 to R2800-10W, between the F6F-3 and the F6F-5.
Then there’s the obvious question . . . exactly what features were incorporated into the F6F design that resulted from flights tests conducted on the A6M2 in California while the first production models of the F6F-3 were being built on Long Island? The first F6F-3 rolled out less than a month after Koga’s Zero was airworthy. Just what did Sanders and company find that would make Leroy Grumman go running back to the drawing board while the approved design was already in production? Answer: Absolutely nothing.
Just what was so earth shattering about the A6M2 design? (Fair warning, this paragraph is a paraphrase from the words which from an F4F ace - with 2 A6Ms to his credit - who also flew the Koga Zero and was a post war Navy test pilot.) Answer, nothing, absolutely nothing . . . that’s the point no one gets. There was no rocket science here. The design was not some miracle. Examination of the aircraft and test flights explained its performance, but there was nothing earth shattering about the design once you figured out what the Japanese wanted to be able to do with the airplane.
The design of the A6M2 was the result of the kind of war the IJN wanted to fight, the way they wanted to fight it. The F6F was designed to meet the USN’s requirements for the kind of war they wanted to fight, the way they wanted to fight it. There was nothing there. US builders were perfectly capable of building an airplane that could perform in the same manner as the A6M2 if they had a customer who asked for it. These are two fundamentally different aircraft that represent diametrically opposing mentalities, doctrines, and practices. Their only similarities were that they could fly, sat one pilot, and could land on an aircraft carrier. There was nothing in the A6M2 design that was needed in the F6F and the F6F was designed and approved before the Koga Zero fell into US hands. This whole issue is wrapped up in the postwar super plane A6M mentality and the corresponding IJN super pilot nonsense. Evaluating the place of the A6M2 in history requires getting away from the wartime propaganda, post-war misinformation, the breath taking overly enthusiastic “gee whiz” factor, and look at the cold hard facts of designing airplanes to meet the customer’s specifications as they relate to his doctrine and practice and the timeframes in which those events occur.