The F4U-1 in World War II
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Development
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Advancements in aircraft design proceeded at an explosive pace during the 1930s, and no sooner did the US Navy adopt the Grumman F4F Wildcat and Brewster F2A Buffalo for development and testing, than they were already looking for a new and better fighter aircraft to take their place, issuing requirements in February 1938 for an aircraft featuring even higher performance. Vought engineers, led by Rex Beisel, began work on plans for a fighter design mounting what was at the time the largest and most powerful radial engine available: The massive 18-cylinder, 2000hp Pratt and Whitney R-2800 Double Wasp, with a displacement of a whopping 2804 cubic inches (46L). The engine would be fit into the smallest and lightest airframe that could fit it, resulting in a sleek and (for a radial engine) streamlined fuselage that fit tightly around the big engine and possessed as small frontal cross-section as possible.
To take full advantage of the power produced, the engine would turn one of the largest propellers used on any fighter plane, in the form of a 13'4" Hamilton Standard three-bladed propeller.
However, it became clear early in development that to provide sufficient ground clearance for the massive 6' propeller blades the aircraft's landing gear would need to be of such great length as to make them unsuitable for the shock and stress of carrier operations. This was the result of the Corsair's low-profile, cylindrical fuselage, which lacked the deep belly of the taller F6F and P-47 fighters. Additionally, to accommodate folding wings for carrier storage the landing gear were designed to retract aftwards, which would require a wing of much greater chord than was practical.
Vought's adopted solution, also used in the German Stuka dive-bomber, would make the Corsair one of the most recognizable aircraft ever produced. The inner portion of the wings were angled downward below the fuselage then extended out again with a slight dihedral in a configuration known as the "inverted gull" wing. The landing gear were placed at the "knuckle" of the wing (the lowest point). This allowed sufficient clearance between the ground and propeller, without extending the landing gear to an impractical length. Additionally, the angle at which the wings met the fuselage would later prove ideal for reducing drag, and would contribute to the airframe's exceptional top speed. However, the wing structure was much more complex than a straight wing of comparable size and rigidity, and would make the Corsair more difficult and expensive to produce.
The F4U also incorporated numerous advances in aeronautical design, particularly over contemporary naval aircraft. She was the first naval fighter to utilize landing gear that completely retracted into the wings and fuselage. Air coolers utilized low-drag vents and slots rather than scoops. Newly-developed techniques in spot-welding and flush rivets were also used, resulting in an aircraft that as aerodynamically cleaner than its predecessors. She was also the last American-produced fighter aircraft to utilize fabric covering for airfoils and control surfaces.
The initial XF4U-1 prototype was ordered on June 11, 1938, and the first flight was performed on May 29, 1940, with Vought chief test pilot Lyman A. Bullard, Jr. at the controls. The XF4U-1, again flown by Bullard, reached a speed of 404mph to become the first fighter aircraft in history to exceed 400mph in level flight while flying under a full combat loadout. However test flights also revealed a number of problems in the design. The inverted gull wing caused disruption in elevator authority while the aircraft was on the ground. This left the pilot with limited control during takeoffs while the tail wheel was down, though this would automatically be corrected as soon as the aircraft built up sufficient airspeed to lift the tail. Additionally, in early full-power dive tests the aircraft suffered damage to control surfaces and access panels at speeds over 550mph, although the aircraft's structure otherwise remained intact.
The most troubling issue, perhaps, was the one that would plague the Corsair for the entirety of her service life and would lead to the aircraft's most famous nickname. The design was found to possess a dangerous accelerated stall that could very rapidly develop into a spin. Recovery of a developed spin of more than two revolutions was almost impossible without the use of an anti-spin chute, forcing alterations in departure recovery requirements. Another area where the Corsair would initially prove to be disappointing was in suitability for carrier service. The main landing gear oleo struts had a strong bounce and were prone to collapse. Additionally, the fighter's suspect low-speed stability and vicious stall behavior led the Navy to declare her unfit for carrier service. The F4U showed a strong tendency to snap over if power was applied too rapidly at low speeds, due to the massive amount of torque put out by the engine. The frequency of accidents among inexperienced pilots quickly led to the Corsairs infamous nickname, "Ensign Eliminator."
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Initially the F4U was armed with two Browning .50cal M2 heavy machine guns in the nose and four Browning .30cal with two in each wing. Additionally, the Corsair was also intended to carry one of the most unusual fighter-mounted weapon systems ever developed. Initial designs called for the aircraft to carry twenty small bombs on the wings. Their purpose was for use not against ground targets, but against enemy bomber formations. The aircraft would fly above the formation and release these small bomblets. However, feedback from observations of combat in Europe during the early stages of the war indicated that the Corsair's armament was sorely under-powered, and changes were quickly made. The anti-air bombs were eliminated, as were the four Browning .30cal. The two .50cal were moved to the wings, and an additional four .50cal were added. The change and redistribution of the aircraft's armament forced another further alteration in the design. Because of the increased armament in the wings, there was no longer space for the large wing-mounted fuel tanks. As a result, the size of the fuselage-mounted tank was greatly enlarged. This required moving the cockpit back an additional three feet, resulting in the F4U's distinctive long nose and but further exacerbating problems with the forward view, especially during landings. The remaining smaller wing tanks would be alternately re-added and removed throughout the development of the aircraft, though would be retained when the aircraft went to production.
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The first production F4U was flown in June, 1942, and 584 F4U-1 Corsairs were ordered several days later.
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Unit Deployment
The F4U-1 was initially declared unfit for duty aboard the fleet's carriers due to the type's numerous teething problems, including gear bounce and collapse, poor forward visibility, and most notoriously, her dangerous spin characteristics. As a result, most F4Us were turned over the the United States Marine Corps. Some were retained by the US Navy, including VF-17, who would later be the first unit to prove that the Corsair could be successfully flown from a carrier deck. The British Royal Navy's Fleet Air Arm and the Royal New Zealand Air Force also operated Corsairs, designated as Corsair Mk.I.
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Most of the initial Corsair variant to see combat were flown by the United States Marine Corps. The aircraft's first combat sortie was flown in from Guadalcanal on February 14, 1943. The action was an overall poor showing for the American forces involved, with two Corsairs and several P-40s, P-38s and B-24s lost to enemy action, however the Marines would soon prove the worth of the "Bent-winged Bird." It quickly became evident that the Corsair was vastly superior to the Zero and Ki-43 fighters used by the Japanese. She was faster at all altitudes, far more rugged and more heavily armed. Rather than attempt to turn with the nimble Japanese fighters, the Marines applied the same tactics that allowed their little Grumman Wildcats to hold their own to the bigger, more powerful Corsair by utilizing high-speed slashing attacks. The Corsair proved exceptionally agile in high speed fights, with a remarkable rate of roll and strong control authority at speeds at which her lighter Japanese opponents would begin experiencing sluggish response.
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Marines who had been flying the older Grumman F4F readily transitioned into the Corsair. Among the first units to receive the Corsair was VMF-124. VMF-214, VMF-215 and VMF-222 would also fly the F4U during the early months of 1943. On May 13, 1943, Kenneth A. Walsh of VMF-124 became the first Corsair ace of the war by shooting down two Japanese aircraft to add to the three he shot down on his previous sortie. Walsh would go on to claim a total of 21 victories before the end of the war, and would be awarded the Medal of Honor.
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As most Corsairs were assigned to Marine Corps squadrons, the F4U-1 primarily served on land bases in the South Pacific. The harsh conditions: rain, mud, punishing sun, highly abrasive coral dust used for runway surfaces, primitive maintenance facilities, and long supply lines led to the ubiquitous battered appearance of many Corsairs in operational areas. Paint faded and was blasted off surfaces by coral dust, and the F4U was notorious for throwing oil from its big engine. Tape on the gun ports and outer fuel tank panels were a common sight. Additionally, Marine ground crew introduced numerous modifications; including deliberately jamming the top cowl flaps closed to prevent oil from being thrown on the canopy in flight. By modifying a Brewster bomb rack the Corsair could be made to carry up to a 1000lb bomb on the centerline, or when available a 150 gallon drop tank to extend the aircraft's already excellent range. The F4U's excellent durability and good firepower made her an excellent ground-attack candidate. Additionally, the aircraft's landing gear design incorporated a dive brake setting, allowing the main landing gear to be extended to slow the aircraft during an attack dive. This capability would be enhanced in later developments of the airframe.
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The tail hooks and wing-folding mechanisms were also frequently removed in the field as they were unnecessary when operating away from the fleet. Some Corsairs also had their wing-mounted fuel tanks removed to save weight, as the tanks were troublesome and prone to leakage. However because of the distances involved during the Pacific war, many pilots preferred the tanks over loss of performance caused by the drop tanks. Other modifications and enhancements were made by Vought themselves, aimed at rectifying many of the Corsair's deficiencies and which were frequently retrofit on aircraft already deployed in the combat zone. Many of these improvements would later be collected under a new designation: the F4U-1A.