Grumman G-18 / G-36 / F4F Wildcat
General Motors FM-1 / FM-2
Designed in 1937 by Robert L. Hall, the company's first carrier-based fighter of monoplane configuration was designed to meet a US Navy requirement which originated in 1935, but it was not until July 1936 that the Navy ordered this aircraft, under the designation XF4F-2 (G-18).
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 to the G-16, the designation XF4F-2 was applied. The prototype, BuNo 0383, was first flown on 2 September 1937. During trials it 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. 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.
To overcome the shortcomings of the XF4F-2, a new prototype was built with a more powerful two-stage supercharged engine, and airframe revisions which increased wing span and brought changes to wingtips and tail surfaces. In this form the XF4F-3 flew for the first time on 12 February 1939.
In July 1936 the navy ordered the prototype XF4F-2, with one of the new 900-hp Pratt & Whitney R-1830 Twin Wasps at the front of a rather tubby fuselage which carried the monoplane wing an inch or two below the mid position. The R-1830S C5-G went into production in 1940 to power the Grumman F4F-3 Wildcat fighter. This was the first production aircraft with two-stage supercharging. The hand-cranked landing gear was re-tained, and the pilot could look down through two windows in the floor of the comfortable cockpit. Bob Hall, designer of the faintly similar Gee Bee racers, took the XF4F-2 on its first flight on 2 Sep-tember 1937. Armed with two 0.5-in guns and two 100-lb bombs, this showed promise but suffered from prolonged engine problems. First flown on 12 February 1939, the XF4F-3 had a com-pletely revised airframe, with broad square-tipped wings and a much-improved tail. It also had a far better Twin Wasp, with a two-stage two-speed supercharger. Armament was increased to two 0.3-in in the fuselage and two 0.5-in in the outer wings. Though by far the heaviest Grumman fighter yet, the Dash-3 proved a fine aircraft, with excellent manoeuvrability, a speed of 333 mph and service ceiling of 33,500 ft. In August 1939 the navy ordered the first batch of 54 F4F-3s, with a longer fuselage, four 0.5-in guns in the wings and, later, armour and self-sealing fuel tanks. This order was soon increased.
Grumman offered an export version of the F4F-3 ordered by the US Navy as the G-36A, a contract for 81 aircraft being placed on behalf of France's Marine Nationale, and France added 81 of a version called the G.36A with Cyclone engines. Seven were in various stages of assembly when France fell and the entire batch was transferred to Britain which also placed a contract for 100 G-36As on its own account. Britain’s Fleet Air Arm put in British non-metric instruments and a throttle lever that worked in the normal sense (the French pulled the lever back for take-off). The six 7.5-mm French guns in the wings were retained.
They proved far better than any other fighter in the Fleet Air Arm, and opened their score on Christmas Day 1940 when two from 804 Squadron shot down a Ju 88 in the north of Scotland.
Whereas the French contract aircraft were powered by the 1,200 hp Wright R-1820-G205A Cyclone, Britain selected the Pratt & Whitney S3C4-G Twin Wasp of similar power. The first (French contract) G-36A flew on 11 May 1940 and entered British service as the Martlet I, a contractual change resulting in the British order being switched to the G-36B with folding wings, this entering service as the Martlet II (although the first 10 were accepted with fixed wings). The 30 F4F-3As that had been assigned to Greece were also taken into the Royal Navy inventory as Martlet IIIs, and with the passage of the Lend-Lease Act, 220 aircraft essentially similar to the F4F-4 but with the single-stage R-1820-40B engine were assigned to the Royal Navy as Martlet IVs (F4F-4Bs), these becoming Wildcat IVs when British and US names were standardised in March 1944.
Churchill regarded the production of Fulmars vital and the greater need for land Spitfires, the diversion of resources to a new navalised variant would reduce Spitfire’s production numbers. To cover the gap until the Fulmar’s replacement (the Fairey Firefly) was able to enter service, Grumman Wildcats were ordered for the FAA. These entered service towards the end of 1940 as the Martlet, but these were unavailable in sufficient numbers, while Sea Hurricanes, without folding wings, were also not advanced enough as a solution.
The appearance of the A6M2-N float fighter in the Aleutians prompted US Navy interest in a float-equipped version of the F4F-3 shipboard fighter. One example was therefore fitted with Edo designed and manufactured single-step metal floats, and with auxiliary rudders mounted near the tips of the tailplane flew on 28 February 1943. The need for additional keel area aft was revealed by initial trials and a large ventral fin was added to improve yaw stability. The floats and their bracing struts raised the fighter's weight by only some 500 lb (227 kg), and from calm water at normal loaded weight the F4F-3S could take-off within 34 seconds. However, the dramatic effect of float drag on speed performance led to an earlier contract to complete 100 F4F-3 Wildcats as float fighters being cancelled.
Altogether Grumman built 369 F4F-3s for the US Navy, followed by 95 Dash-3As with the R-1830-90 engine. Some were converted to F4F-3P photo aircraft and BuNo 4038 was fitted with twin floats. The navy allotted the name Wildcat, thereby establishing the famous series of Grumman ‘cat’ fighters, and the British changed to the same name in January 1944. The chief drawback of the otherwise outstanding F4F-3 was its size, which did not fit too well with the constricted decks of the new escort carriers.
Leroy Grumman took two paperclips and, after bending them in various directions, stuck them into a pencil eraser. He thus proceeded to demonstrate the principle of what at first was called the ‘stowing’. By attaching the outer wings by oblique skewed hinges they were made to fold back on each side of the fuselage, upper surface outwards. The company made absolutely sure it worked before committing it to production at the 163rd aircraft, subsequent deliveries being designated F4F-4s, or Martlet IIs. These had the 1,200-hp R-1830-86 engine and the heavy armament of six 0.5-in guns in the outer wings. They were by far the most important Allied fighters in the Pacific from Pearl Harbor until the summer of 1943. Grumman completed the last of 1,971 F4F-4s on the last day of 1942, subsequently needing every inch of floor for the TBF and F6F. Small numbers were built of the experimental Dash-5 to -8.
In January 1942 General Motors formed its Eastern Aircraft Division to build aircraft in under-used car factories. In 1942 the manufacture of the Wildcat was transferred to the Eastern Aircraft Division of the General Motors Corporation. The first FM-1 Wildcat, assembled from parts supplied by Grumman, flew on 1 September 1942. The FM-1, fitted with a Pratt & Whitney R-1830-86 engine, was virtually the same as the F4F-4 (Wildcat IV). By 11 April 1944 the Eastern Aircraft Division had produced its 2,500th Wildcat.
Manufacture of the F4F-4 continued in slightly modified form as the FM-1 Wildcat, the R-1830-86 Twin Wasp engine being retained but wing armament being reduced from six to four 0.5-in (12,7- mm) guns and ammunition capacity being raised (from 1,440 to 1,720 rounds). The first FM-1 was flown on 31 August 1942, at Linden, New Jersey, a total of 1,151 subsequently being built of which 312 were assigned to Britain as Martlet (later Wildcat) Vs.
The version of the Wildcat built in largest numbers by General Motors, however, was the FM-2, the first version of the fighter produced for the US Navy to standardise on the 1,350-hp R-1820-56 Cyclone engine. The FM-2 was the production version of the XF4F-8, two prototypes of which were built by Grumman with the first flying on 8 November 1942. Distinguished by its short cowling and redesigned, taller tail. FM-2 Wildcats had the oil coolers removed from the under surface of the centre-section to the cowling, which was revised in shape. The removal of the oil coolers permitted the installation of universal racks under the inner wings for bombs or auxiliary fuel tanks, six 0.5-in guns, and (from No. 3,301) six 5-in rockets. This version was called the Wildcat V by the Fleet Air Arm.
A total of 4,777 FM-2 Wildcats was built of which 370 were assigned to Britain as Wildcat VIs.
Excluding prototypes a total of 7,898 F4Fs and FMs were built.
These were used operationally by the US Navy on a wide scale in the Pacific (FM-2 in particular serving as light escort carrier fighters), participating in the battles of the Coral Sea and Midway, and were used extensively in the attack on Guadalcanal. The type remained in first-line service until the end of the war. British Martlets initially replaced Sea Gladiators and, like their US Navy counterparts, remained operational until the end of the war.
Engine: Pratt & Whitney R-1830-66 Twin Wasp, 900-hp.
Wing span: 34 ft.
Armament: two 0.5-in guns & two 100-lb bombs.
Engine: Pratt & Whitney R-1830 Twin Wasp.
Armament: 4 x 0.5-in mg.
Max speed: 333 mph.
Service ceiling: 33,500 ft.
G.36A Martlet I / Wildcat
Engine: Wright R-1820 Cyclone.
Armament: six 7.5-mm mg.
G-36 / F4F-3S
Max speed, 266 mph (428 kph) at 20,300 ft (6 185 m).
Initial climb, 2,460 ft/min (12,5 m/sec).
Max range, 600 mls (965 km).
Empty weight, 5,804 lb (2 633kg).
Loaded weight, 7,506 lb (3405 kg).
Span, 38 ft 0 in (11,59 m).
Length, 39 ft 1 in (11,91 m).
Height, 18 ft 13 in (5,53 m).
Wing area, 260 sq ft (24,15 sq.m).
F4F-4 / Martlet II / Wildcat
Engine: Pratt & Whitney R-1830-36/40 Twin Wasp, 1,200-hp / 895kW
Wing span: 38 ft / 11.58 m
Length: 8.76 m / 28 ft 9 in
Height: 2.81 m / 9 ft 3 in
Wing area: 24.15 sq.m / 259.95 sq ft
Max speed, 293mph (471 km/h) at 13,000 ft (3 965 m).
Cruise speed: 249 km/h / 155 mph
Initial climb, 3,050 ft/min (15,49 m/sec).
Ceiling: 12010 m / 39400 ft
Max range (clean), 890 mls (1432 km).
Empty weight, 5,425 lb (2461 kg).
Normal loaded weight, 7,580 lb (3 438 kg).
Armament: six 0.5-in mg, 2 x 45kg bombs.
Engine: Pratt & Whitney R-1830-86 Twin Wasp, 1,200-hp.
Armament: 4 x 0.5-in mg.
FM-2 Wildcat V
Engine: Wright R-1820-56 Cyclone, 1,350-hp.
Armament: six 0.5-in guns, and (from No. 3,301) six 5-in rockets.
Max speed, 289 mph (465 km/h) at sea level, 319 mph (513 km/h) at 19,600 ft (5 980 m).
Time to 10,000 ft (3 050 m), 4.5 min.
Max range (clean), 780 mls (1255 km).
Empty weight, 5,542 lb (2 516 kg).
Max loaded weight, 8,221 lb (3 732 kg).
Span, 38 ft 0 in (11,59 m).
Length, 28 ft 9 in (8,77 m).
Height, 11 ft 5 in (3,48 m).
Wing area, 260 sq ft (24,15 sq.m).
Grumman F4F-4 Wildcat