Grumman F6F Hellcat

The Grumman F6F Hellcat was a carrier-based fighter aircraft conceived to replace the earlier F4F Wildcat in United States Navy (USN) service. Although the F6F resembled the Wildcat, it was a completely new design, powered by a 2,000 hp Pratt & Whitney R-2800, the same powerplant used for both the Navy's earlier Chance Vought F4U Corsair and the United States Army Air Force's (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 the Hellcat was the least modified fighter of the war, with a total of 12,200 being built in just over two years.

Hellcats were credited with destroying 5,223 aircraft while in service with the U.S. Navy, U.S. Marine Corps and the Royal Navy's Fleet Air Arm This was more than any other Allied naval aircraft. Postwar, the Hellcat was phased out of frontline service, but remained in service as late as 1954 as a night fighter.

XF6F
Grumman had been working on a successor to the F4F Wildcat since 1938 and the contract for the prototypeXF6F-1 was signed on 30 June 1941. The aircraft was designed to use the Wright R-2600 Twin Cyclone two-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 landing gear retracting into the fuselage, 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. 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 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. BuAer's LT CDR A. M. Jackson  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 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 (CV-9) in February 1943.

Further development
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-section hardpoint 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.

The F6F-5 featured several improvements including a more powerful R-2800-10W engine, embodying a water-injection system and housed in a slightly more streamlined engine cowling, spring-loaded control tabs on the ailerons, 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 underway.

U.S. Navy and Marines
The Hellcat first saw action against the Japanese on 1 September 1943 when fighters off the USS Independence (CVL-22) shot down a Kawanishi H8K "Emily" flying boat. Soon after, on 23 and 24 November, Hellcats engaged Japanese aircraft over Tarawa, shooting down a claimed 30 Mitsubishi Zeros for the loss of one F6F. Over Rabaul, New Britain, on 11 November 1943, Hellcats and F4U Corsairs were engaged in day-long fights with many Japanese aircraft including A6M Zeros, claiming nearly 50 aircraft.

When trials were flown against a captured Zero Type 52, they showed that the Hellcat was faster at all altitudes. The F6F outclimbed the Zero marginally above 14,000 ft and rolled faster at speeds above 235 mph. The Japanese fighter could out-turn its American opponent with ease at low speed and enjoyed a slightly better rate of climb below 14,000 ft. The trials report concluded: "“Do not dogfight with a Zero 52. Do not try to follow a loop or half-roll with a pull-through. When attacking, use your superior power and high speed performance to engage at the most favourable moment. To evade a Zero 52 on your tail, roll and dive away into a high speed turn.”"

Hellcats were the major U.S. Navy fighter type involved in the Battle of the Philippine Sea, where so many Japanese aircraft were shot down that Navy aircrews nicknamed the battle "the Great Marianas Turkey Shoot". The F6F accounted for 75% of all aerial victories recorded by the U.S. Navy in the Pacific. Radar-equipped Hellcat night fighter squadrons appeared in early 1944.

U.S. Navy and Marine F6F pilots flew 66,530 combat sorties and claimed 5,163 kills (56% of all U.S. Navy/Marine air victories of the war) at a recorded cost of 270 Hellcats in aerial combat (an overall kill-to-loss ratio of 19:1 based on claimed but not confirmed kills). The aircraft performed well against the best Japanese opponents with a claimed 13:1 kill ratio against the A6M Zero, 9.5:1 against the Nakajima Ki-84, and 3.7:1 against the Mitsubishi J2M during the last year of the war. The F6F became the prime ace-maker aircraft in the American inventory, with 305 Hellcat aces. The U.S. successes were not only attributed to superior aircraft, but also from 1942 onwards, they faced increasingly inexperienced Japanese aviators as well as having the advantage of increasing numerical superiority. In the ground attack role, Hellcats dropped 6,503 tons (5,899 tonnes) of bombs.

The U.S. Navy preferred the more docile flight qualities of the F6F compared with the Vought F4U Corsair, especially during carrier takeoffs and landings, and the F6F remained the standard USN carrier-borne fighter until the F4U series was finally cleared for carrier operations in late-1944. 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. The U.S. Navy's all-time leading ace, Captain David McCampbell USN (Ret), scored all his 34 victories in the Hellcat. He once described the F6F as "... an outstanding fighter plane. It performed well, was easy to fly and was a stable gun platform. But what I really remember most was that it was rugged and easy to maintain."

During the course of World War II, 2,462 F6F Hellcats were lost to all causes; 270 in aerial combat, 553 lost to anti-aircraft ground and shipboard fire, and 341 were lost to operational causes. Of the total figure 1,298 were destroyed in training and ferry operations, normally outside of the combat zones.

British use
The British Fleet Air Arm (FAA) received 1,263 F6Fs under the Lend-Lease Act; initially it was known as the Grumman Gannet Mark I. The name Hellcat replaced it in early 1943 for the sake of simplicity, the Royal Navy at that time adopting the use of the existing American naval names for all the U.S.-made aircraft supplied to it, with the F6F-3 being designated Hellcat F Mk.I, the F6F-5, the Hellcat F Mk.II and the F6F-5N, the Hellcat NF Mk.II. They saw action off Norway, in the Mediterranean and in the Far East. A number were fitted with photographic reconnaissance equipment similar to the F6F-5P, receiving the designation Hellcat FR Mk.II. The Pacific War being a naval war, the FAA Hellcats primarily faced land based aircraft in the European and Mediterranean Theaters, and as a consequence experienced far fewer opportunities for air-to-air combat than their USN/Marines counterparts; they claimed a total of 52 enemy aircraft kills during 18 aerial combats from May 1944 to July 1945. 1844 Naval Air Squadron, on board HMS Indomitable (92) of the British Pacific Fleetwas the highest scoring unit, with 32.5 kills.

FAA Hellcats, as with other Lend-Lease aircraft, were rapidly replaced by British aircraft after the end of the war, with only two of the 12 squadrons equipped with the Hellcat at VJ-Day still retaining Hellcats by the end of 1945. These two squadrons were disbanded in 1946.

Postwar
Postwar, the Hellcat was succeeded by the F8F Bearcat, which was smaller, more powerful and more maneuverable, but entered service too late to see combat in World War II. The Hellcat was used for second-line USN duties, including training. In late 1952, Guided Missile Unit 90 used F6F-5K drones, each carrying a 2000 lb bomb, to attack bridges in Korea; flying from USS Boxer (CV-21), radio controlled from an escorting AD Skyraider. The French Aéronavale was equipped with F6F-5 Hellcats and used them in Indochina. The Uruguayan Navy also used them until the early 1960s.

XF6F prototypes

 * XF6F-1
 * First prototype, powered by a two-stage 1,600 hp (1,500 kW) Wright R-2600-10 Cyclone 14 radial piston engine.


 * XF6F-2
 * The first XF6F-1 prototype revised and fitted with a turbocharged Wright R-2600-16 Cyclone radial piston engine. R-2600 replaced by turbo-charged R-2800-21.


 * XF6F-3
 * Second prototype fitted with a two-stage supercharged 2,000 hp (1,500 kW) Pratt & Whitney R-2800-10 Double Wasp radial piston engine.


 * XF6F-4
 * One F6F-3 fitted with a two-speed turbocharged 2,100 hp (1,567 kW) Pratt & Whitney R-2800-27 Double Wasp radial piston engine.


 * XF6F-6
 * Two F6F-5s that were fitted with the 2,100 hp (1,566 kW) Pratt & Whitney R-2800-18W radial piston engine, and four-bladed propellers.

Series production

 * F6F-3 (British designations Gannet Mk. I then Hellcat Mk. I)
 * Single-seat fighter, fighter-bomber aircraft, powered by a 2,000 hp (1,500 kW) Pratt & Whitney R-2800-10 Double Wasp radial piston engine.


 * F6F-3E
 * Night fighter version, equipped with an AN/APS-4 radar in a fairing on the starboard outer wing.


 * F6F-3N
 * Another night fighter version, equipped with a newer AN/APS-6 radar in a fairing on the starboard outer wing.


 * F6F-5 Hellcat (British Hellcat Mk. II)
 * Improved version, with a redesigned engine cowling, a new windscreen structure with an integral bulletproof windscreen, new ailerons and strengthened tail surfaces; powered by a 2,200 hp (1,640 kW) Pratt & Whitney R-2800-10W (-W denotes Water Injection) radial piston engine.
 * Improved version, with a redesigned engine cowling, a new windscreen structure with an integral bulletproof windscreen, new ailerons and strengthened tail surfaces; powered by a 2,200 hp (1,640 kW) Pratt & Whitney R-2800-10W (-W denotes Water Injection) radial piston engine.


 * F6F-5K Hellcat
 * A number of F6F-5s and F6F-5Ns were converted into radio-controlled target drones.


 * F6F-5N Hellcat (British Hellcat N.F. Mk II)
 * Night fighter version, fitted with an AN/APS-6 radar. Some were armed with two 20 mm (0.79 in) AN/M2 cannon in the inner wing bays and four 0.50 in (12.7 mm) M2 Browning machine guns in the outer.


 * F6F-5P Hellcat
 * Small numbers of F6F-5s were converted into photo-reconnaissance aircraft, with the camera equipment being fitted in the rear fuselage.


 * Hellcat FR Mk II
 * This designation was given to British Hellcats fitted with camera equipment.


 * FV-1
 * Proposed designation for Hellcats to be built by Canadian Vickers; cancelled before any built.

Operators

 * French Navy
 * Royal Navy
 * United States Navy
 * United States Marine Corps
 * Uruguayan Navy
 * United States Navy
 * United States Marine Corps
 * Uruguayan Navy
 * Uruguayan Navy

Survivors
A relatively large number of Grumman F6Fs are survivors, either in museums or in flyable condition. In order of Bu.No. they are:

United Kingdom

 * Airworthy
 * F6F-5K
 * 80141 - The Fighter Collection in Duxford.


 * On display
 * F6F-5
 * 79779 - Fleet Air Arm Museum in RNAS Yeovilton.

United States

 * Airworthy
 * F6F-3
 * 41930 - Chino Warbirds Inc. in Houston, Texas.
 * F6F-5
 * 70222 - Commemorative Air Force (Southern California Wing) at Camarillo Airport (former Oxnard AFB) in Camarillo, California.
 * 78645 - Yanks Air Museum in Chino, California.
 * 79863 - Vulcan Warbirds Inc., hangared at the Flying Heritage Collection in Everett, Washington.
 * F6F-5N
 * 94204 - Lone Star Flight Museum in Galveston, Texas.
 * 94473 - Palm Springs Air Museum in Palm Springs, California.


 * On display
 * F6F-3
 * 41476 - Evergreen Aviation & Space Museum in McMinnville, Oregon. It is on loan from the National Museum of the Marine Corps in Triangle, Virginia.
 * 42874 - San Diego Aerospace Museum in San Diego, California.
 * F6F-3K
 * 41834 - National Air and Space Museum in Washington D.C..
 * F6F-5
 * 66237 - National Museum of Naval Aviation at NAS Pensacola in Pensacola, Florida.
 * 70185 - Quonset Air Museum at Quonset State Airport (former NAS Quonset Point) in Quonset Point, Rhode Island.
 * 94203 - National Museum of Naval Aviation at NAS Pensacola in Pensacola, Florida.
 * F6F-5K
 * 77722 - Joint Base Andrews Naval Air Facility at Andrews AFB in Maryland.
 * 79192 - New England Air Museum in Windsor Locks, Connecticut.
 * 79593 - USS Yorktown (CV-10)/Patriots Point Naval & Maritime Museum in Mount Pleasant, South Carolina.
 * 79683 - Kalamazoo Aviation History Museum in Kalamazoo, Michigan.
 * 94263 - Cradle of Aviation Museum in New York. It is on loan from the USMC Museum in Quantico, Virginia.


 * Under restoration
 * F6F-3
 * 25910 - under restoration at the National Museum of Naval Aviation at NAS Pensacola in Pensacola, Florida after being retrieved from Lake Michigan in 2009.
 * 40467 - under restoration at Yanks Air Museum in Chino, California.
 * 43041 - under restoration to airworthy condition at Fantasy of Flight in Polk City, Florida.