Grumman F4F Wildcat

Development

XF4F-1

On 2 March 1936, Grumman was awarded a contract for the development of its model G-16, a shipboard biplane fighter for the US Navy, under the designation XF4F-1. The G-16, which was designed by Dick Hutton and Bill Schwendler, was very similar in general layout to the earlier biplane fighters of Grumman, the F2F and its development the F3F. It was smaller, with a wing span of 27ft, compared with 32ft for the F3F. Its length was 23ft 3in, and its gross weight 4500lb.

The XF4F-1 had a conservative biplane layout, with staggered wings. A bulge of the lower front fuselage covered the narrow-track retractable landing gear, similar to that of the F3F. A fully covered cockpit was placed relatively far aft to the tail, behind the lower wing trailing edge. The aircraft was powered by the 900hp Wright XR-1670-2 14-cylinder, two-row radial engine. As an alternative, the XR-1535-95 of 800hp was considered. With the XR-1670 engine, a top speed of 264mph was estimated. This was only a marginal improvement over the performance of last models of the F3F. The armament consisted of two cowl-mounted .50 guns, or one .50 and one .30.

The performance of the XF4F-1 was obviously inferior to that expected of the Brewster F2A design, which was to become the USNs first operational monoplane fighter. The future of the XF4F-1 held little promise, because it was considered merely as a back-up for the F2A, if this proved to be unsuitable. Nobody was very happy about the model G-16, and after four months the USN cancelled the contract. The XF4F-1 was never flown.

XF4F-2

To compete with the Brewster F2A, Grumman developed the model G-18. The first sketches showed a mid-wing monoplane development of the XF4F-1, with an almost unchanged fuselage. The monoplane wing had a span of 34ft, with rounded tips. The tail surfaces had similar rounded tips. Like the F2A, the G-18 had no wing folding.

The fuselage had, because of the radial engine and voluminous undercarriage retraction mechanism, a rotund, tubby shape. This was already a trademark of Grumman, established with the earlier F2F and F3F. The cockpit was moved much forward by comparison with the XF4F-1, so that the pilot now sat over the wing. The cross-section of the fuselage was maximal at the cockpit, and tapered towards to the engins. This assured that the pilot had a good forward view, which was essential for a deck-landing. The cockpit was fitted with a telescopic gunsight, which protuted through the windscreen. Two down-look windows were cut in each side of the lower fuselage. The fuselage spine which started behind the cockpit tapered down rapidly, and ended just in front of the tail fin. The hingeline of the rudder was canted forward.

The model G-18 was powered by the Pratt & Whitney R-1830-66 Twin Wasp engine, a two-row, fourteen-cylinder radial. A Hamilton Standard two-position propeller was fitted. The armament installation was basically the same as that of the XF4F-1, with two 0.50 guns with 200 rounds each in the top of the engine cowling, and provision for two 100lb bombs under the wings. The gross weight of the aircraft was 5635lb, a substantial increase over the XF4F-1 biplane.

The G-18 was ordered on 28 July 1936. Despite the substantial differences with the G-16, the designation XF4F-2 was applied. The prototype, BuNo 0383, was first flown on 2 September 1937. During trials its demonstrated a maximum level speed of 290mph, which was faster than the XF2A-1, but still below the USN requirement of 300mph.

The XF4F-2 was delivered to NAS Anacostia on 23 December 1937 for evaluation. During trials the prototype suffered from a series of snags and accidents. None of these was particularly serious, but their undermined the confidence of the USN. The XF4F-2 suffered repeated engine crankshaft failures. The arrestor hook proved too weak. On 24 February 1938 there was an on board fire when ballast bags in the aft fuselage began to burn. And on 11 April 1938 the XF4F-2 suffered a crash when the engine failed during a simulated deck landing.

As a result, the US Navy selected the more reliable Brewster F2A-1 Buffalo for production, after NACA tests had suggested that minor aerodynamic improvements could boost the speed of the XF2A-1 by 30mph. The USN ordered 54 F2A-1s on 11 June 1938.

F4F-3

Despite this setback, the USN continued to show interest in the F4F. This was probably partly due to its unwillingness to rely fully on the production of Brewster: The order for the F2A-1 was the first production contract for Brewster, and the manufacturer did not even possess a factory which was adequate for the production of aircraft. Grumman had already built the FF, F2F and F3F for the Navy, and the F4F showed some promise. A development contract was awarded in October 1938.

The Grumman G-36, designated XF4F-3 by the USN, was first flown 12 February 1939. It had been evolved from the XF4F-2 (the prototype of which was modified to become the XF4F-3) by installing the Pratt & Whitney XR-1830-76 engine with a two-stage, two-speed supercharger. Two intercoolers were also installed. This was the first fighter to enter service with such an engine installation. (The first version of the Mitsubishi A6M 'Zeke' with a two-stage supercharger was the A6M3, which began to enter service when Battle of Guadalcanal began.) The two-bladed, two-position propeller of the XF4F-2 was replaced by a three-bladed Curtiss-Electric constant-speed propeller, which was initially distrusted by the pilots. Because of the increased engine weight, a larger wing with rectangular tips was fitted. This increased the wing span from 34ft to 38ft and the wing area from 232ft2 to 260ft2. Also, the fuselage was revised and lengthened. At this stage the prototype still had the tail surfaces of the XF4F-2 with a canted rudder hingeline. Thanks to its new engine, the XF4F-3 reached 333.5mph at 21000ft.

The engine cooling was a problem, and a series of cowl and propeller spinner designs was tried to improve it. Finally the propeller spinner was deleted, and cuffs were fitted to the propeller blade roots. NACA tests at Langley field resulted in some redesign. The tail fin was made larger, and the fuselage spine aft of the cockpit, which previously ended just in front of the tail fin, was extended and faired into the fin root. The tailplane was raised 20in, from the fuselage onto the fin. The wing dihedral was increased, and the ailerons reduced in area. The radio mast was moved from in front of the cockpit to behind the cockpit. The armament of the XF4F-3 was two 0.3 cowl guns and two 0.5 wing guns. A telescopic gun sight was still fitted.

In this form, the F4F-3 was accepted by the USN, and an order for 54 was received in August 1939. After the first two, the cowl guns were removed, and four 0.50 wing guns fitted. The production aircraft were powered by the R-1830-76 engine, which initially gave some problems. Most F4F-3s had no armour and self-sealing fuel tanks.

The first delivery was made on 5 December 1940, to VF-4. Then later VF-7, VF-42, VF-71 were equipped. The F4F-3 was also given to USMC, beginning with VMF-121, VMF-211 and VMF-221. The first cruise was made USS Ranger and USS Wasp, in early 1941. Experience resulted in the deletion of the wing flotation bags, because these tended to inflate in flight. They were positioned over the wing leading edge, and generated prodigious drag. In one such incident, Ensign Howell of VF-42 was killed. There was also a need to strengthen the windscreen, and fuel tank pressurization was required to fly at high altitude. The tailwheel was weak, and cockpit ventilation was inadequate.

A shortage of the -76 engines with their two-stage superchargers resulted in a production batch with -90 engines with single-stage, two-speed superchargers. These aircraft were designated F4F-3A. The first one was delivered on 26 November 1940.

The name 'Wildcat' was officially adopted on 1 October 1941.

At the time of Pearl Harbour only USS Enterprise had a fully-equipped Wildcat squadron, VF-6 with F4F-3As. The USS Enterprise was then transferring a detachment of VMF-211, also equipped with F4F-3s, to Wake. The USS Saratoga was in San Diego, working up for operations of the F4F-3s of VF-3. Eleven F4F-3s of VMF-211 were at the Ewa Marine Air Corps Station on Oahu; nine of these were damaged or destroyed during the Japanese attack. The detachment of VMF-211 on Wake lost 7 Wildcats to Japanese attacks on 8 December, but the remaining five put up a fierce defense, making the first bomber kill on 9 December. The destroyer Kisagara was sunk by the Wildcats, and the Japanese invasion force retreated. In these dark days the defense of Wake generated enthusiasm in the USA, but it was impossible to send help, and later Wake surrendered to a much superior invasion force.

In February 1942 the USS Yorktown and USS Enterprise striked against the Marshall and Gilbert islands. Meanwhile the USS Lexington operated near New Guinea, for an attack on the Japanese base of Rabaul. The latter attack was abortive, because the Japanese detected the presence of the US fleet. But Lt. Edward H. 'Butch' O'Hare of VF-3 later received the Congressional Medal of Honor for shooting down five Mitsubishi G4M 'Betty' bombers over Rabaul, on 20 February.

Coral Sea

In May 1942 the F4F-3s of VF-2 and VF-42, on board of USS Yorktown and USS Lexington, participated in the Battle of the Coral Sea. The USS Lexington and USS Yorktown fought against the Zuikaku, Shokaku and the light Shoho in this battle, in an attempt to halt a Japanese invasion of Port Moresby on Papua.

On 7 May a force of 93 US aircraft, of which 18 Wildcats, found the light carrier Shoho --- a small ship of 11200 tons, which carried only 12 Zeros for its own defense. Shoho was sunk, and the attackers lost only three aircraft. It was claimed that eight Zeroes had been shot down. An unescorted counter-attack by B5Ns and D3As in the evening was successfully repelled, with heavy losses on the side of the attackers. Eight aircraft were shot down, eleven more failed to find their carriers. However, when 69 Japanese aircraft attacked again the next day, the fighter cover of USS Lexington and USS Yorktown consisted of only eight Wildcats, because all others had been sent to escort an attack on the Japanese carriers Shokaku and Zuikaku. The Shokaku was seriously damaged, but the USS Lexington had to be abandoned and the USS Yorktown was damaged. The aircraft losses were high on both sides, taking into account the small number of aircraft committed to battle; the Japanese lost 40 aircraft, the US 33.

During these battles, it became clear that attacks without fighter escort amounted to suicide, but that the fighter component on the carriers was completely insufficient to provide both fighter cover for the carrier and an escort for an attack force. Most US carriers carried less than 20 fighters. The introduction of the F4F-4 with its folding wings improved this situation, because it increased the number of fighters that could be parked on a surface by more than a factor 2. The F4F-3 was replaced by the F4F-4 in June 1943, during the battle of Midway; only VMF-221 still used them at that time.

The total production of the F4F-3 was 285, that of the F4F-3A was 95. After the Italian attack of 1941, 30 F4F-3As were sent to Greece, and were used after the Greek surrender by the FAA as Martlet Mk.III.

A few were fitted with cameras and referred to F4F-3P; there was also one F4F-3AP.

Specification of the Grumman F4F-3 Wildcat:

Engine: Pratt & Whitney R-1830-76 Twin Wasp, 14-cylinder, two-row radial engine, with a two-speed, two-stage mechanical supercharger. Three-bladed Curtiss Electric C5315(S) propeller with a diameter of 9ft 9in. Power of 1200hp at 2700rpm for take-off. Military power 1100hp at 2550rpm, sea level; 1000hp at 19000ft. 147 US gallons in internal fuel tanks, provision for one 58 US gallon external tank under each wing.

Performance: 278mph at sea level, 330mph at 22000ft. Max range cruise 185mph. Initial climb rate 2050ft/min. Service ceiling 31000ft, absolute ceiling 32600ft. Max endurance 9.4 hrs. Take-off distance 228ft into a 25kn wind.

Weights: 5293lb empty, 7467lb normal, 3978kg max take-off.

Dimensions: Wing span 38ft, length 28ft 9 3/8in, height 8ft, wing area 260ft2. Wing root chord 8ft 7in, wing tip chord 5ft 1 5/8in.

Armament: Four Colt-Browning 0.50 guns. Two 100lb bombs.

F4F-3S

A floatplane version of the F4F-3 was developed for use at forward island bases in the Pacific, before the construction of airfields. It was inspired by appearance of the A6M-2N 'Rufe', a modification of the Mitsubishi A6M 'Zeke' by Nakajima. BuNo 4083 was modified to become the F4F-3S 'Wildcatfish'. Twin floats, manufactured by Edo, were fitted. To restore the stability, small auxiliary fins were added to the tailplane. Because this was still insufficient, a ventral fin was added later.

The F4F-3S was first flown 28 February 1943. The weight and drag of the floats reduced the maximum speed to 241mph. As the performance of the basic F4F-3 was already below that of the A6M, the F4F-3S was clearly of limited usefulness. Anyway, the construction of the airfields at forward bases by the 'Seabees' was surprisingly quick. Only one was converted.

Martlet Mk.I

At the end of 1939 Grumman received a French order for 81 aircraft of model G-36A, to equip the new carriers Joffre and Painleve. The main difference with the basic model G-36 was due to the unavailability for export of the two-stage supercharged engine of F4F-3. The G-36A was powered by the nine-cylinder, single-row R-1820-G205A radial engine, of 1200hp. This was combined with a Hamilton Standard constant-speed propeller. The first deliveries featured highly polished, shiny propeller blades.

The G-36A had also French instrumentation, radio, and gunsight. The throttle was modified to conform to French pre-war practice: the throttle lever was moved towards the pilot to increase engine power. The armament too was French, six 75mm Darne guns being specified. The first G-36A was flown on 11 May 1940.

None of the aircraft ever entered French service. After defeat of France, all contracts were taken over by Britain. The throttle was modified again, four 0.50 guns were installed in the wings, and most traces of the original ownership removed. The Martlets were modified for British use by Blackburn, which continued to do this for all later marks. British gunsights, catapult spools, and other items were installed. After initial attempts to fit British radio sets, it was decided to use the much superior American equipment.

The British Admiralty chose the name of Martlet Mk.I for this fighter. The first ones entered service in August 1940, with No 804 squadron, then stationed at Hatson in the Orkneys. The Martlet Mk.I did not have a wing folding mechanism, and was therefore only used from land bases.

The small fighter from Grumman was designed for carrier use, and for land- based operations this resulted in some problems, especially with the soft, narrow-track undercarriage. There were problems with landing or taking off in a cross-wind or when taking corners during fast taxying, because the Martlet Mk.I tended to roll on its undercarriage, enough to make a wingtip touch the ground. A 'Wing Tip Club' was formed at Haston. Of course these problems would not have been felt in carrier operations. RAF test pilots also had some other criticisms, especially related to the cockpit: Carbon monoxide leaked into cockpit, there was a strong draught when cockpit was opened, except at low speed, and there was no provision for the jettisoning of the canopy. Another problem was the lack of automatic boost control, which kept the pilot busy with adjustments. The manual retraction of the landing gear was probably disliked by all pilots who ever flew a Wildcat.

The first combat of Grumman's little fighter took place on 25 December 1940, when two aircraft from No 804 squadron brought down a Ju 88A near Scapa Flow, the base of the Home Fleet. The pilots of these aircraft were Lt. L.L.N. Carver and Sub. Lt. (A) Parke.

Martlet Mk.II

Before the FAA (Fleet Air Arm) took on charge the Martlet Mk.Is of the original French order, it had already order one hundred model G-36B fighters. The British chose the Pratt & Whitney R-1830-S3C4-G engine to power this aircraft; this too had a single-stage supercharger. The FAA decided to accept a delay in delivery to get folding wings, which were vitally important if the Martlet was to be used from British carriers with their small hangar decks. Nevertheless, the first ten received had fixed wings. The first Martlet with folding wings was not delivered before August 1941. A description of the wing folding is given in the chapter on the F4F-4.

The Martlet Mk.II was about 1000lb (450kg) heavier than Mk.I, because of wing folding, a heavier engine, and two additional machine guns. Also in contrast to F4F-3, the British aircraft were fitted with armour and self-sealing fuel tanks. The Mk.II also had a larger tailwheel. For carrier operations, the 'sting' tail hook and attachment point for the American single-point catapult launch system were considered important advantages. Nevertheless, the Martlets were modified to have British-style catapult spools.

At this point, the Martlet was simply the only single-seat, monoplane carrier fighter available to the British fleet. Previously it had equipped its fighter units with the Gloster Sea Gladiator biplane fighter, and the single-engined, two-seat Fairey Fulmar, which was a nice and reliable aircraft but just didn't have the performance required to combat enemy single-seaters. The Martlet was therefore received with enthusiasm by the FAA.

The majority of the Martlet Mk.IIs (54) were sent to the Far East. The first shipboard operations of the type in British service were in September 1941, on board of HMS Audacity. The Audacity was a conversion of the former German merchant vessel Hannover. It was a very small carrier with a carrier deck of 128m by 18m. It no lifts and no hangar deck; the six Wildcats were parked on the deck at all times. On its first voyage, it served as escort carrier for a convoy to Gibraltar. On 20 September, a German Fw 200 was downed when it made a bomb run at the convoy. On the next voyage, four Fw 200s fell to the guns of the Martlets. Operations from the HMS Audacity also demonstrated that the fighter cover was useful against U-boats. Audacity was sunk by an U-boat on 21 December 1941, but it had proven the usefulness of escort carriers.

In May 1942 the No 881 and 882 squadron, on HMS Illustrious, participated in operations against (Vichy-French) Madagascar. In August 1942 No 806 on HMS Indomitable provided fighter cover for a convoy to Malta. Later in that year they participated in the landings in French North Africa.

Martlet Mk.III

The first 30 F4F-3As were released for sale to Greece, after the Italian invasion of that country in November 1940. However, at the defeat of Greece in April 1941 the aircraft had only reached Gibraltar. They were taken over by the FAA as Martlet Mk.III.

Because these aircraft did not have folding wings, they were only used from land bases. They served in a shore-based role in the Western Desert, with the so-called 'Royal Naval Fighter Unit.'

F4F-4

The major difference between the F4F-4 and the F4F-3 was the introduction of a wing folding mechanism. A single hinge was placed in the wing spar. The hinge line was reportedly experimentally determined by Roy Grumman with the help of an eraser in which two bend paperclips were inserted, representing the wings. The main spar was angled forward, so that the top of the hinge line was well in front of the bottom; there were small blisters on the wing covering the top of the hinge. When folding the wing backwards, the leading edge of the wing moved downwards, so that the wings were stored parallel with the fuselage, leading edge down. They were secured to the tailplane with struts. Unfolded, they were secure by a locking cylinder in the leading edge, which was screwed in with a crank. Five F4F-4s could be parked in the place previously used by two F4F-3s. Also, aircraft handling on the deck and through the lift became much easier.

The first XF4F-1 had hydraulic wing folding, but this was abandoned because of the excess weight. All production aircraft had manual wing folding.

The F4F-4 had also other modifications to make the aircraft more combat-capable. Armament was increased to six guns, with 1440 rounds. Armour and self-sealing fuel tanks, previously only fitted to the British Martlets and a few F4F-3s, were fitted. This much improved the survival chances of the pilot. There was a provision for 50 or 58 US gal drop tanks under the fixed parts of the wing, as well as bombs. The engine was the R-1830-86 of 1200hp, also fitted to the last F4F-3s, but because of the additional weight, the performance suffered. The F4F-4 also proved less suitable for operations for escort carriers, which lead to the development of the lighter FM-2. The US Navy orders totaled 1169 F4F-4s. It had replaced the F4F-3 by August 1942.

The F4F-4A was an unbuilt version powered by the R-1830-90. At least one Wildcat was converted to F4F-4P photo-recce configuration. One F4F-4 was fitted, as an experiment, with electrically-operated, full-span flaps. Another served as a testbed for the breakaway wing tips, which were later used on the F8F Bearcat.

Midway

The most famous battle in which the Wildcat participated was the Battle of Midway. While six Wildcats were based on Midway itself, as well as 21 F2A Buffalos, most of the fighter component was contributed by the carriers. With the lessons of the Coral Sea in mind, the fighter strength of the US fleet was increased by one third. The USS Yorktown carried 25 fighters, the USS Hornet and USS Enterprise each 27.

Their contribution was not, however, decisive, if only by their still relatively small number. Of the 116 aircraft which attacked the Japanese fleet on 4 June, only 20 were Wildcats; all others were torpedo and dive bombers. 36 Wildcats were kept behind to protect the US carriers. Half of the fighter escort did not find the Japanese fleet and later had to ditch because they had ran out of fuel. The weak fighter cover (six Wildcats) of VT-3 was unable to protect the 12 TBDs, while VT-6 and VT-8 attacked without any fighter escort, with disastrous results. However, the battle turned around dramatically when two formations of SBD Dauntless dive bombers arrived, encountered no opposition, and hit the Akagi, Kaga and Soryu. While the Wildcats were reasonably able to defend themselves --- claiming four kills, for the loss of one --- it was clear that the battle had been won more by luck than by strength. When the surviving Japanese carrier, the Hiryu, counter-attacked, the fighter cover of the Yorktown, 12 Wildcats, claimed 13 of the 18 attacking D3A 'Val' dive bombers, and three of the six A6Ms. A follow-up attack force of 10 B5N 'Kate' torpedo bombers and six A6Ms also lost four aircraft. However, this did not prevent that the Yorktown was hit by three bombs and two torpedos, which eventually caused its loss.

Guadalcanal

The qualities of the F4F were proven in the next large series of battles in the Pacific, the fights around the island of Guadalcanal. Guadalcanal is one of the Solomon islands, which are North-East of Australia. The island of 160 by 80 km is mountaineous and covered with a dense jungle. Most of the fights centered around Henderson Field, the airbase near Cap Lunga.

The battles began with the landing of the 1st Division of the USMC on Guadalcanal, on 7 August 1942, protected by a large part of the US fleet. During three days of intensive fighting between US Navy aircraft of the USS Enterprise, USS Saratoga and USS Wasp (a total of 99 fighters, 103 dive-bombers, and 41 torpedo-bombers) and Japanese aircraft from Rabaul on New Ireland (75 fighters, 48 twin-engined bombers, 18 long-range recce flying boats, 12 floatplane fighters, and 16 dive-bombers) the Japanese suffered disproportionate losses. Of course, this was partly due to the large distance between Guadalcanal and their base at Rabaul --- flights of 2000km were required --- which made it impossible for some of the used aircraft, notable the D3A dive bombers, to return to their base. Also, the G4M 'Betty' bomber was extremely vulnerable. The A6M 'Zeke' fighter force had some successes. In a famous incident, the Japanese fighter pilot Saburo Sakai witnessed how a single F4F fought off three A6Ms, until Sakai himself intervened.

Finally, the US force did establish some kind of air superiority over Guadalcanal when the Japanese decided to suspend air attacks after two days, because of the excessive losses. However, at this moment Rear-admiral Fletcher decided to remove the US carrier fleet from the battle zone, handling according to the principle that the carriers, which were as vulnerable as they were valuable, should not stay in the same area for more than two days. The decision was not unlogical in itself, but combined with the disastrous end of the naval battle at Savo Island on the next day, it contributed to put an end to the career of Fletcher.

Two weeks later the carriers had returned, and in the fight known as the Battle of Eastern Solomons, the USS Enterprise and USS Saratoga fought a battle with the Zuikaku, Shokaku and the light carrier Ryujo. While US carrier aircraft found and sank the Ryujo, a Japanese counter-attack of the main force managed to damage the USS Enterprise, despite a fighter cover of 53 Wildcats, which was largely kept at a distance by the escorting A6Ms. In this case, inefficient fighter control was largely to blame. This remained a problem during the next fights, despite the advantage of radar. Enterprise was only temporarily disabled, however. At the end of the month, Japanese submarines damaged USS Saratoga and sank USS Wasp.

On 26 October, during the battle of the Santa Cruz islands, the pattern repeated itself. US aircraft damaged the Zuiho and Shokaku, while Japanese aircraft hit USS Hornet and USS Enterprise, and finally sank USS Hornet. While this undoubtly was a tactical victory for the Japanese, the aircraft losses of both parties were again so high that they had to retreat. The presence of US aircraft on Henderson Field, near Cap Lunga on Guadalcanal, outweighed the advantage.

The result of these battles suggests that overall, the Wildcat failed to fulfill its role. While the Wildcats did shoot down a considerable number of enemy aircraft, thereby limiting the strength of Japanese attacks on the US fleet, the carriers invariably suffered serious damage whenever they were the target of a Japanese attack. And attacks on the Japanese fleet often resulted in the loss of a considerable number of aircraft. After 1942, newer fighters replaced the Wildcat as carrier-borne fighter, and the US Navy established air superiority. One would be inclined to blame the Wildcat. However, this is too simplistic. There is no doubt that the F6F and F4U were better aircraft than the old F4F, but the Wildcat was not as inferior to the A6M as some sources suggest. In a combat situation, the two fighters were fairly evely matched, if the Wildcat pilot was wise enough to use the strong points of their aircraft --- dogfighting with the A6M was always to be avoided.

The low impact of the fighter force in the battles of 1941 and early 1942 can be attributed to their numerical weakness. Large carriers as the USS Lexington and USS Saratoga began the war with only 18 fighters on board, a fourth of all aircraft they carried. At the battle of Okinawa in March 1945, the large fleet carriers had 70 or more fighters, or two thirds of all aircraft they carried were fighters. At Okinawa, a small escort carrier had a more powerful fighter cover than the USS Lexington in the Battle of the Coral Sea. Of course, this change towards a larger complement of fighters was made possible by the fact that the newer, larger fighters could carry a substantial armament load. The F6F could carry two 1000lb bombs, a load comparable to that of the TBF Avenger of the SBD Dauntless. The unability to carry a substantial bomb load was always a weakness of the Wildcat.

There was also important tactical changes, with a much stronger attempt to gain air superiority. Instead of escorting torpedo bombers and dive bombers, the fighters were sent out alone to attack Japanese bases, achieving air superiority before the final attack was done. These tactics finally culminated in the 'Big Blue Blanket' designed to Jimmy Thach as a defense against Kamikaze attacks.

Specification of the Grumman F4F-4 Wildcat:

Engine: Pratt & Whitney R-1830-86 Twin Wasp, 14-cylinder, two-row engine, with a two-speed, two-stage mechanical supercharger. Three-bladed Curtiss Electric propeller with a diameter of 2.97m. Power 1200hp at 2900rpm for take-off. Military power 1200hp at 2700rpm from sea level to 550m, and 1135hp at 1035m. Normal power 1100hp at 2550rpm at sea level, 1090hp at 3445m. 545 in internal fuel tanks, provision for one 220l external tank under each wing.

Performance: 441km/h at sea level, 515km/h at 5735m. Max range cruise 259km/h at 1525m. Initial climb rate 9.9m/sec. Climb to 3050m 5.6min, to 6100m 12.4min. Service ceiling 10370m. Max range on internal fuel 1335km, 2051km with two drop tanks. Take-off distance 195m, 125m into a 28km/h (15kn) wind.

Weights: 2676kg empty, 3621kg normal, 3978kg max take-off.

Dimensions: Wing span 11.59m, length 8.85m, height 3.44, wing area 24.15m. Width with folded wing 4.35m.

Armament: Six Colt-Browning 0.50 guns, 240 rounds each.

Martlet Mk.IV

This was basically F4F-4 delivered to Britain under Lend-Lease contracts. For contractual purposes, the USN designation F4F-4B was assigned. It was never used by the USN.

The engine was the R-1820-40B Cyclone, also known was GR-1820-G250A-3 for export. A Hamilton Standard Hydromatic airscrew was used. The top speed of the Martlet Mk.IV was 296mph, slightly below that of the F4F-4. Gross weight was 7904lb.

FM-1 and Martlet Mk.V

The production facilities of Grumman were not large enough to built large numbers of the F6F, TBF and F4F. The Eastern Aircraft Division of General Motors was created to take over production of the TBF and F4F, under the designations TBM and FM. The name 'Mongoose' was proposed for Eastern-built Wildcats, but luckily it didn't stick.

The FM-1 was basically a F4F-4 built by the Eastern Aircraft, in its factory at Linden, New Jersey. There was one change: The FM-1 had only four guns, with ammunition increased to 430 rounds per gun. This version of the Wildcat was primarily intended for escort carriers, as the F6F was replacing the F4F on the fleet carriers.

Contract for 1800 aircraft were awarded on 18 April 1942. The first one was flown on 31 August. Finally 1060 were built before production was switched to the FM-2. Of these, 839 were destined for the USN and USMC, and 312 were delivered to Britain as Martlet Mk.V.

These British aircraft flew support missions for the invasion of Southern France, Operation Dragoon, in August 1944. Later they also flew from HMS Illustrious in support of the invasion of Italy, in Salerno Bay. They also operated from HMS Victorious in West-Pacific. In January 1944, the Admiralty decided to abandon the name Martlet, and the type became the Wildcat Mk.IV in British service.

F4F-5

Nos 3 and 4 from the F4F-3 production line were completed as XF4F-5, with the R-1820-40 Cyclone engine with a single-stage supercharger, this because the R-1830-76 gave problems. Later one of these was fitted with a R-1820-48 with a two-stage supercharger, and one with a turbo-supercharged R-1820-54.

F4F-6

This was a version of the F4F-3 with R-1830-90 with single-stage, two-speed supercharger. It was ordered into production as the F4F-3A.

F4F-7

The F4F-7 was a long-range photo-recce version, first flown on 31 December 1941. The F4F-7 had a non-folding wing, containing 555 US gallons of fuel. This boosted the total fuel capacity to 695 US gallons, giving a range of 3700 miles, or an endurance of 25 hours! Obviously this was a bit exaggerating the point, for such flights would have been much too demanding for the pilot, even though an autopilot was installed.

To save weight, the F4F-7 had no armament or armour, and the bullet resistant windscreen was replaced by a simple curved one. Nevertheless, the gross weight increased to 10328lb. To reduce the weight quickly in case of an emergency, a fuel dump system was installed. The two dump pipes of this system were visible under the rudder. A single camera was carried.

Only 21 were built, and the rest of the order was completed as fighters. Only two are reported to have been used, at Guadalcanal.

Specification of the Grumman F4F-7 Wildcat:

Engine: Pratt & Whitney R-1830-86 Twin Wasp, 14-cylinder, two-row engine, with a two-speed, two-stage mechanical supercharger. Three-bladed Curtiss Electric C5315(S) propeller with a diameter of 2.97m. 1200hp at 2900rpm for take-off. Military power 1200hp at 2700rpm from sea level to 550m, and 1135hp at 1035m. Normal power 1100hp at 2550rpm at sea level, 1090hp at 3445m.

Performance: 250mph at sea level, 309mph at 22000ft. Cruise speed 200mph. Landing speed 86mph. Initial climb rate 1730ft/min. Service ceiling 28300ft. Max range on internal fuel 4540 miles, endurance 25.5hrs. Take-off distance 574ft into a 25kn wind.

Weights: 5468lb empty, 10336lb combat gross weight.

Armament: none.

XF4F-8 and FM-2

The increased weight of the F4F-4 made this version less suitable for use on the small decks of escort carriers. However, the Wildcat was more suited to these small, slow carriers than the newer, but also larger and heavier fighters such as the F6F and F4U. Therefore it was decided in 1942 to develop a lighter model. The two prototypes were built by Grumman under the designation XF4F-8, but production aircraft were built by Eastern as the FM-2.

The new Wildcat was powered by the R-1820-56 engine. Previous USN Wildcats were all powered by the R-1830, but the R-1820-56 delivered 1350hp, 150hp more than the engine of the F4F-4, and was also 102kg lighter, with a weight of 604kg. The weight was also reduced by deleting two guns (increasing ammunition to 1720 rounds at the same time) and the reserve fuel tank. The new engine had a single-stage supercharger, and performance at altitude was therefore below that of the F4F-4. But at low levels the performance was considerably better, with a spectacular improvement in climbing rate. The main tasks of the FM-2 were to be submarine patrols and close air support, so performance at high altitude was less important.

The two XF4F-8s were modified F4F-4s. The first one was flown on 8 November 1942. The prototypes were fitted with slotted flaps, but these proved less efficient that the split flaps of earlier models. The XF4F-8 weighed 2433kg empty, 3211kg gross, and 3752kg at max overload. The production FM-2 was, inevitably, a bit heavier.

Characteristic for the engine installation was a rectangular indentation of the forward fuselage aft of the cowling ring, above the wing leading edges, were the exhaust of the engine were grouped. The circular oil coolers under the inboard wing sections were removed. In side view, the FM-2 was easy to identify. And a taller vertical tail was fitted, because of the more powerful torque of the engine. This had other benefits, for the FM-2 now also had fully satisfactory spin recovery characteristics. The tailhook had to be reinforced after combat experienced showed it to be too weak.

Some later aircraft had the -56W or -56WA engines, with water injection. A tank with a 10min water supply was carried. After the 240st aircraft the main fuel tank of 117 US gallons was replaced by one of 126 US gallons, compensating a bit for the deletion of the reserve tank. After the 3301st aircraft provision was made for six 5in rockets.

The first order, for 1265, was signed in early 1943. The final production of the FM-2 was 4127, plus 340 Wildcat Mk.VIs for the FAA. The FM-2 was the most built version of the Wildcat.

The first combat of the FM-2 was during Operation Flintlock, the invasion of Kwajalein, in January 1944, when the USS Manila Bay (Task Group 52.9) carried twelve FM-2s. In June they fought in operation Forager, the invasion of the Marianas. Experience showed that the FM-2 had at best only a marginal performance advantage over the Japanese aircraft, and that its reduced armament was a disadvantage. But the Japanese pilots of the time were inexperienced and poorly trained.

In October 1944 a conference on aircraft requirements was held at Patuxent River. The armed forces showed their latest fighters, and an impressive demonstration of the XF8F-1 Bearcat was done by Bob Hall. But the FM-2 was nevertheless considered the best fighter below 10000ft, even in comparison with the F6F, F4U, P-47 and P-51. It was stable, handled well in a dive, and had excellent landing characteristics. On the other hand, its level speed was unimpressive, its small armament load was a problem, and the cockpit provided no rearward view.

In the Battle of Leyte, 15 of the 18 escort carriers of the 'Taffy' force carried FM-2s. Only weak air opposition on the first days, but on 24 October there was spiritied fighting, and Lt. K. G. Hippe of VC-27 became an 'ace-in-a-day' by shooting down five K-48 'Lily' bombers, being bettered by Lt Cdr H. Funk who claimed six kills that day. At the end of the day, the Japanese had lost 47 aircraft; five FM-2s had been lost. This result confirmed the confidence in the FM-2. However, it was felt yet again that the number of available fighters was too small: at the end of the day, the 15 carriers had 'only' 290 FM-2s. For the attack on Mindoro in December, the number of fighters was boasted to 24 on each of six escort carriers.

In 1945 a new and rather unique unit was deployed, VOC-1 on USS Wake Island. This unit was intended to act as artillery spotters for the fleet. The pilots had trained on F4Us and F6Fs, but reequipped finally with the FM-2. In the battle of Okinawa VOC-2 made its debut. The spotters proved very effective, and fought in the front line for the next invasions in the Pacific, of Iwo Jima in February and of Okinawa in March, in which 12 and 18 escort carriers participated, respectively.

At the end of the war, four USN pilots had become aces on the FM-2: Lt. R. Elliot (VC-27) with nine kills, Lt Cdr H. Funk (VF-26) with six, Lt. K. Hippe (VC-13) with five, and Ens J. McGraw (VC-10 and VC-80) with five. Total claims for the FM-2 were 420.

Specification of the General Motors (Eastern Aircraft) FM-2 Wildcat:

Engine: Wright R-1820-56W Cyclone, 9-cylinder, single-row engine, with a two-speed, single-stage mechanical supercharger. Three-bladed Curtiss Electric CS propeller with a diameter of 10ft. 1350hp for take-off, 1200hp at 5000ft, 900hp at 18500ft.

Performance: 289mph at sea level, 319mph at 19600ft. Max climb rate at sea level 2890ft/min. Best climb 3650ft/min. Service ceiling 35600ft. Max range on internal fuel 780 miles, 1350 miles with two drop tanks. Take-off distance 195m, 125m into a 28km/h (15kn) wind.

Weights: 5542lb empty, 7431lb gross.

Armament: Four Colt-Browning 0.50 guns, 1720 rounds total. Racks for six 5in rockets under the wings.

Wildcat Mk.VI

The FM-2 was known as Martlet Mk.VI in FAA service; it was renamed Wildcat Mk.VI in January 1944. 340 were delivered. The FM-2 equipped, partially or completely, 22 squadrons, ten of which used the type operationally. Their first major action was operation Dragoon, the invasion of Southern France, in which No 881 sqn flew 180 sorties. But the Wildcat Mk.VI operated mainly in Far East.

On 26 March 1945, Mk.VIs of No 882 squadron shot down five Bf 109Gs over Norway. These were the last FAA victories of WWII.

XF2M-1

The F2M was a design by Eastern Motors for a version of the Wildcat powered by the XR-1820-70 engine. It was never built.

Description

All details for F4F-4, except indicated otherwise.

Construction

The wing was built around a single main spar. Models with folding wings had a inclined main spar, parallel with the hinge line. The folding parts were flush-riveted, the fixed parts were not. When folding the wing backwards, the leading edge of the wing moved downwards, so that the wings were stored parallel with the fuselage, leading edge down. They were secured to the tailplane with struts.

All control surfaces of the Wildcat were fabric-covered and were mechanically operated, with exception of the flaps, which were operated by a vacuum tank installed behind the cockpit. The rudder and elevator had small horn balances, the ailerons had inset hinges.

The fuselage was of semi-monococque construction, with a skin of aluminium alloy. It had external rivets, with overlap of the fuselage skin at the joints of skin and frames. This give the outside of the fuselage a 'rib' at each frame.

The radial engine was carried by a tubular engine mounting, attached to the cockpit firewall. An 11 US gallon oil tank was installed in the upper half of the fuselage, between the engine mounting ring and the cockpit firewall. The lower half of this fuselage bay was occupied by the landing gear. The intercoolers, generator, engine starter and other engine accesories were also in this section. The main fuel tank (117 US gal, 443l) was below the cockpit floor. There was a reserve fuel tank (27 US gal, 102l) behind the cockpit.

In the bay behind the cockpit were also the vacuum tank for flap actuation, the oxygen bottle, the R/T set, and the battery. There was an access door to the aft fuselage on the right side, aft of the wing root. Closer to the aft bulkhead the radio compass was installed. An opening was made in each side of the fuselage, connected by a tube inside, and served as attachment points for lifting the aircraft.

In the fuselage spine behind the cockpit (aft of the section covered by the sliding canopy) a liferaft was installed, but this was usually deployed too late to be of any use.

Engine

The engines used by the Wildcat version were the Pratt & Whitney R-1830 Twin Wasp fourteen-cylinder, two-row radial engine, and the Wright R-1820 Cyclone nine-cylinder, single-row radial engine.

The R-1820 was less complicated and lighter than R-1830, and later versions were more powerful at lower altitude. The larger diameter of the R-1820 resulted in slightly worse forward view, and the R-1820 was much noisier and produced more vibration than the R-1830.

Cockpit

To access the cockpit, there was a foot support and a hand hold at each side of the fuselage, aft of the cockpit. There were walkways over the wing roots. The cockpit was roomy, but the FAA judged that the arrangement of the controls was a bit confusing. The pilot had a good view to front, for deck landing, because of high position of the cockpit. The view sideways and downwards was also reasonable. There was virtually no rearwards view. The Wildcat had a bullet resistant windscreen, with a reflector sight, and rearward-sliding plexiglass canopy. Most had a single window on each side of the lower fuselage, intended to give the pilot some view downwards, but this was minimal. They were probably more useful as access panels to the lower fuselage.

The first models did only have seat lap belt, and not a shoulder harness. In case of a crash, this seriously endangered the pilot's head.

The front panel of Martlet Mk.II had a directional gyro and an artificial horizon on the top row, left and right of the gunsight mounting. On the lower row were, left to right, the air speed indicator, altimeter, turn-and-bank indicator, rate of climb indicator, boost gauge and oil temperature/pressure indicators. The engine instrumentation was to the left and right of the main instrument panel. (The arrangement of the F4F-3 was basically the same, but there was a compass at the center of the panel, which was displaced by the larger gunsight in the Martlet Mk.II.)

Left of the main panel the ignition switch, fuel pump, supercharger controls, engine rpm indicator, and propeller switches were grouped. Also the undercarriage lamp and reflector sight intensity controls were located there. Right of the main panel the fuel gauge, carburetor temperate gauge, temperature gauge, inertia starter switch, cowling gills control and fire extinguisher control were found. The left console contained even more engine controls, such as the cylinder temperature gauge, main fuel cock, and throttle lever. The rudder, elevator and aileron trim were also on the left console, with the controls for the arrester hook and the locking tailwheel. One the right console was a box with electric switches, including the gun selector switches, and cockpit lighting controls. Behind it was the R/T panel. Below the right console was the infamous undercarriage crank; 30 turns were required to retract the undercarriage.

Undercarriage

The undercarriage of the Wildcat had a narrow track and was very soft. There were hydraulic brakes, controlled by toe brakes on the rudder pedals. They were less efficient than desirable.

The main wheels were retracted by 30 turns on a hand crack, the pilot being required to crank with his right hand while holding the stick with his left hand. Usually this resulted in a wobbling climb. This was disliked by pilots, and somewhat dangerous; there were at least two accidents, one fatal, when the lead of the pilot's R/T headset got entangled in crank. The retraction mechanism used chains which lead to sprockets at the top of the compression strut; this folded in two places, near the top and near the wheel. The wheels (Bendix 26x6 in) were stored flat aside the fuselage, under the wing leading edge. A lower fuselage cover was attached to the landing gear, and sealed the underside.

There was a non-retractable locking tailwheel. It was required to lock this before take-off, to counter the Wildcat's tendency to swing. It was Installed aft of the aft fuselage bulkhead, in front of the tailplanes. The first models had a solid tailwheel, but this was later replaced with a larger, inflatable one which lifted the tail (9in, 23cm) higher on the ground, giving better control during take-off.

The sting tailhook extended from the extreme end of the tail and then dropped down.

Armament

The Wildcat had gun cocking handles on cockpit floor, with steel cables running to guns.

0.50 guns were used in all operational fighter models: four in the F4F-3, Martlet Mk.I, FM-1, and FM-2, and six all other models. The wing guns of the F4F-3 were installed just outboard of the propeller disc, staggered to make room for the ammunition feeds. The additional wing guns of the F4F were installed more outboard, outside of the ammunition boxes of the inner guns.

The installation of the guns in FM-1 and FM-2 was similar to that of the F4F-3, but not identical; the guns barrels did not protrude from the wing leading edges as in the F4F-3.

The guns were accessible by panels in the upper wing surface. The gun ammunition boxes could be removed and replaced from the underside of the wing.

Handling

For take-off, the Wildcat required careful handling, because the fuselage blanked the rudder, and there was a strong tendency to veer to port. Cross-winds were to be avoided. The tailwheel had to be locked and checked. Until the tail was lifted, careful appliance of the brakes was required, to avoid overheating them. These problems were of course more important for land-based operations than for carrier operations.

The level and dive speed was inferior to that of contemporary land-based fighters, but climb and manoeuvrability were good. However, they were still inferior to the performance of the A6M 'Zeke', which excelled in these aspects. The Wildcat was relatively stable, and had heavier stick forces than other fighters.

Deck-landing characteristics were very good, because of the good handling at low speed, the excellent forward vision, a robust undercarriage, and the sting tailhook. The stall was completely innocuous, at 157km/h clean, and 146km/h all down (Martlet Mk.II). A spin was not easy to recover from, and deliberate spinning was prohibited. This was cured with the larger tail of the FM-2.

In comparison with its most important opponent, the Mitsubishi A6M Reisen 'Zeke', better known as 'Zero', the F4F-4 was inferior in level speed, climb and manoeuvrability. They were however fairly evenly matched in a dive, because the F4F was heavier and more powerful, and better controllable at high speed. It never had an operational speed limit; the terminal dive speed was probably over 500mph.

Most importantly, the F4F was a sturdy aircraft, with armour and self-sealing fuel tanks, which resisted the armament of the A6M well. It was very unusual for a Wildcat to catch fire when hit, while the woefully vulnerable A6M tended to fall apart or burst in flames when hit by a short burst of the Wildcat's .50 guns.

Much depended on the tactics applied and the training of the pilots. The 'Thach Weave' was adapted by the USN as a standard fighter tactic, and was very effective. However, in the beginning of the war the Japanese pilots often had combat experience, which USN pilots did not yet have. Nevertheless the F4F, despite its theoretical disadvantages, did remarkably well in combat. A kill ratio of 6.9 to 1 was claimed: 178 lost, for 905 'confirmed' kills. The most successful Wildcat pilot was Joe Foss, with 26 kills, all on the Wildcat. This made him the leading USMC ace.

Sources


Emmanuel Gustin
gustin@uia.ua.ac.be