The Grumman F6F Hellcat was an American carrier-based fighter aircraft designed to replace the earlier F4F Wildcat in United States Navy (USN) service. The Hellcat competed with the faster Vought F4U Corsairfor use as a carrier based fighter. The Corsair had significant issues with carrier landings which the Hellcat did not, allowing the Hellcat to become the Navy's dominant fighter in the second part of World War II, a position the Hellcat did not relinquish. The Corsair instead was primarily deployed to great effect in land-based use by the U.S. Marine Corps.
Although the F6F resembled the Wildcat in some ways, it was a new design, powered by a 2,000 hp Pratt & Whitney R-2800, the same powerplant used for both the Corsair and the United States Army Air Force(USAAF) Republic P-47 Thunderbolt fighters. Some military observers tagged the Hellcat as the "Wildcat's big brother".
The F6F was best known for its role as a rugged, well-designed carrier fighter which was able, after its combat debut in early 1943, to counter the Mitsubishi A6M Zero and help secure air superiority over the Pacific Theater. Such was the quality of the basic simple, straightforward design, that 12,200 were built in just over two years.
Hellcats were credited with destroying a total of 5,223 enemy aircraft while in service with the U.S. Navy, U.S. Marine Corps and the Royal Navy Fleet Air Arm.[Note 2] This was more than any other Allied naval aircraft. Postwar, the Hellcat was phased out of front line service but remained in service as late as 1954 as a night fighter.
Design and development
The unpainted XF6F-1 prior to its first flight
Grumman had been working on a successor to the F4F Wildcat since 1938 and the contract for the prototype XF6F-1 was signed on 30 June 1941. The aircraft was originally designed to use the Wright R-2600 Twin Cyclonetwo-row, 14-cylinder radial engine of 1,700 hp (1,268 kW) driving a three-bladed Curtiss Electric propeller. Instead of the Wildcat's narrow-track, hand-cranked main landing gear retracting into the fuselage that it had inherited, little changed in design from the 1931-debuted Grumman FF-1 fighter biplane, the Hellcat had wide-set, hydraulically actuated landing gear struts which rotated through 90° while retracting backwards into the wings, much like that of the earlier Chance Vought F4U Corsair, but with full wheel doors fitted to the struts that covered the entire strut and the upper half of the main wheel when retracted, and twisted with the main gear struts during retraction. The wing was mounted lower on the fuselage and was able to be hydraulically or manually folded, with each panel outboard of the undercarriage bay folding backwards from pivoting on a specially oriented, Grumman-patented diagonal axis pivoting system much like the earlier F4F, with a folded stowage position parallel to the fuselage with the leading edges pointing diagonally down.
Throughout early 1942 Roy Grumman, along with his chief designers Jake Swirbul and Bill Schwendler, worked closely with the U.S. Navy's Bureau of Aeronautics (BuAer) and experienced F4F pilots, to develop the new fighter in such a way that it could counter the Zero's strengths and help gain air command in the Pacific Theater of Operations. On 22 April 1942, Lieutenant Commander Butch O'Hare toured the Grumman Aircraft company and spoke with Grumman engineers, analyzing the performance of the F4F Wildcat against the Mitsubishi A6M Zero in aerial combat.[Note 3] BuAer's LT CDR A. M. Jackson [Note 4] directed Grumman's designers to mount the cockpit higher in the fuselage. In addition, the forward fuselage sloped down slightly to the engine cowling, affording the Hellcat's pilot good visibility.
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 own beginnings in 1940 — in the second XF6F-1 prototype. Grumman complied by redesigning and strengthening the F6F airframe to incorporate the 2,000 hp (1,500 kW) R-2800-10, driving a three-bladed Hamilton Standard propeller. With this combination Grumman estimated the XF6F-3s performance would increase by 25% over that of the XF6F-1. The Cyclone-powered XF6F-1 (02981) first flew on 26 June 1942, followed by the first Double Wasp-equipped aircraft, the XF6F-3 (02982), which first flew on 30 July 1942. The first production F6F-3, powered by an R-2800-10, flew on 3 October 1942, with the type reaching operational readiness with VF-9 on USS Essex in February 1943. [Note 5]
An early F6F-3 in Blue-Gray over Light Gull-Gray
The F6F series were designed to take damage and get the pilot safely back to base. A bullet-resistant windshield and a total of 212 lb (96 kg) of cockpit armor was fitted, along with armor around the oil tank and oil cooler. A 250 gal (946 l) self-sealing fuel tank was fitted in the fuselage. Standard armament on the F6F-3 consisted of six .50 in (12.7 mm) M2/AN Browning air-cooled machine guns with 400 rounds per gun. A center-sectionhardpoint under the fuselage could carry a single 150 gal (568 l) disposable drop tank, while later aircraft had single bomb racks installed under each wing, inboard of the undercarriage bays; with these and the center-section hard point late model F6F-3s could carry a total bomb-load in excess of 2,000 lb (900 kg). Six 5 in (127 mm) HVARs (High Velocity Aircraft Rocket) could be carried; three under each wing on "zero-length" launchers.
Two night fighter sub-variants of the F6F-3 were developed: the 18 F6F-3E's were converted from standard-3s and featured the AN/APS-4 radar in a pod mounted on a rack beneath the right wing, with a small radar-scope fitted in the middle of the main instrument panel and radar operating controls installed on the port side of the cockpit. The later F6F-3N, first flown in July 1943, was fitted with the AN/APS-6 radar in the fuselage, with the antenna dish in a bulbous fairing mounted on the leading-edge of the outer right wing; approximately 200 F6F-3Ns were built. Hellcat night fighters claimed their first victories in November 1943. A total of 4,402 F6F-3s were built through until April 1944, when production was changed to the F6F-5.
An early production F6F-5 being tested with eight 5 in. HVAR rockets
The F6F-5 featured several improvements including a more powerful R-2800-10W engine employing a water-injection system and housed in a slightly more streamlined engine cowling, spring-loaded control tabs on theailerons, and an improved, clear view windscreen, with a flat armored-glass front panel replacing the F6F-3's curved plexiglass panel and internal armor glass screen. In addition, the rear fuselage and tail units were strengthened, and, apart from some early production aircraft, the majority of the F6F-5's built were painted in an overall gloss sea blue finish. After the first few F6F-5s were built, the small windows behind the main canopy were deleted. The F6F-5N night fighter variant was fitted with an AN/APS-6 radar in a fairing on the outer-starboard wing. A small number of standard F6F-5s were also fitted with camera equipment for reconnaissance duties as the F6F-5P. While all F6F-5s were capable of carrying an armament mix of one 20 mm (.79 in) M2 cannon in each of the inboard gun bays (220 rounds per gun), along with two pairs of .50 in (12.7 mm) machine guns (each with 400 rounds per gun), this configuration was only used on later F6F-5N night fighters. The F6F-5 was the most common F6F variant, with 7,870 being built.
Other prototypes in the F6F series included the XF6F-4 (02981, a conversion of the XF6F-1 powered by an R-2800-27 and armed with four 20mm M2 cannon) which first flew on 3 October 1942 as the prototype for the projected F6F-4. This version never entered production and 02981 was converted to an F6F-3 production aircraft. Another experimental prototype was the XF6F-2 (66244), an F6F-3 converted to use a Wright R-2600-15, fitted with a Birman manufactured mixed-flow turbocharger, which was later replaced by a Pratt & Whitney R-2800-21, also fitted with a Birman turbocharger. The turbochargers proved to be unreliable on both engines, while performance improvements were marginal. As with the XF6F-4, 66244 was soon converted back to a standard F6F-3. Two XF6F-6s (70188 and 70913) were converted from F6F-5s and used the 18-cylinder 2,100 hp (1,567 kW) Pratt and Whitney R-2800-18W two-stage supercharged radial engine with water injection and driving a Hamilton-Standard four-bladed propeller. The XF6F-6s were the fastest version of the Hellcat series with a top speed of 417 mph (671 km/h), but the war ended before this variant could be mass-produced.
The last Hellcat rolled out in November 1945, the total production being 12,275, of which 11,000 had been built in just two years. This high production rate was credited to the sound original design, which required little modification once production was under way.
The U.S. Navy much preferred the more docile flight qualities of the F6F compared with the Vought F4U Corsair, despite the superior speed of the Corsair. This preference was especially noted during carrier landings, a critical success requirement for the Navy, in which the Corsair was fundamentally flawed in comparison. The Corsair was thus released by the Navy to the Marine Corps who without the need to worry about carrier landings, used the Corsair to immense effect in land-based sorties. The Hellcat remained the standard USN carrier-borne fighter until the F4U series was finally cleared for U.S. carrier operations in late-1944 (the carrier landing issues had by now been tackled largely thanks to use of Corsair by the Royal Navy Fleet Air Arm). In addition to its good flight qualities, the Hellcat was easy to maintain and had an airframe tough enough to withstand the rigors of routine carrier operations. Like the Wildcat, the Hellcat was designed for ease of manufacture and ability to withstand significant damage.
Grumman F6F-5 ready for launch from USS Bennington
in May 1945. The majority of the F6F-5s built were painted overall Glossy Sea Blue.