Chance Vought Coursair F4U-1A, -1C, F4U-4, -4C

In February 1938, the US Navy Bureau of Aeronautics published a requests for proposals (RFP) for both a twin-engine and a single-engine fighter. In April 1938, Vought proposed its two designs to the US Navy. One, called V-166A by Vought and "Vought A" by the USN, was powered by the R-1830. The other, the V-166B or "Vought B", was designed around the new Pratt & Whitney R-2800 Double Wasp radial engine. This was an 18-cylinder, two-row air-cooled radial. This engine would later also be installed in the competing Grumman F6F Hellcat and in the Republic P-47 Thunderbolt for the USAAF, but the new Vought fighter was the first to use this engine. The R-2800 later acquired a reputation as a powerful and very reliable engine. But it was also very bulky, and aircraft powered by it tended to be big. In May, the Bureau of Aeronautics evaluated the proposals. The "Vought B" was deemed to be the best one, with a merit figure of 86.4 on a scale from 0 to 100. Hence on 11 June, a contract was given for development of the Vought V-166B, the fighter that would become famous as the F4U Corsair.

Vought's Chief designer Rex B. Beisel opted for a fuselage of circular cross-section, of a diameter matching that of the R-2800. The oil cooler and supercharger air intakes would be installed in the wing leading edges. He also avoided the hump-backed upper fuselage of the Grumman F4F and F6F, that was designed to give the pilot a better forward visibility over the engine. Hence, the forward fuselage was of cylindrical shape. Construction was all-metal, and streamlining was improved further by using a new spot-welding technique that gave a very smooth finish.

A very large propeller was required to convert the power of the R-2800 into forward thrust. A huge three-bladed propeller with a diameter of 13 ft. 4 in. was chosen. Sufficient propeller clearance could have been achieved by designing a long and stalky landing gear, or by making the fuselage deeper again, thus moving the wing downwards relative to the engine. Instead, the Vought team adopted an inverted gull wing: the wing started with strong anhedral, i.e. a downwards slope toward the wingtips, and then curved upwards to strong dihedral. The landing gear was installed at the lowest point of the bend. Such a construction was not uncommon, though usually associated with fixed landing gear, such as on the German Junkers Ju 87 "Stuka" dive bomber. Inevitably, the weight of such a construction is higher than that of a straight wing. But apart from keeping the landing gear short and simple, it offered the advantage that the joint between wing and fuselage was made at the ideal angle. In that way a wing root fairing could be avoided. The entire construction contributed to the purposeful ugliness of the design, but it was efficient.

For storage aboard carriers, the wing folded upward outboard of the main landing gear legs. The wheels folded backwards, turning through 90 degrees while retracting, so that they were stored flat within the wing. The entire trailing edge inboard of the ailerons was provided with flaps. The outer wing panels were covered with fabric aft of the wing spar. The pilot sat in a large cockpit over the wing trailing edge. The view straight forward over the engine cowling was poor, even more so than common in single-seat fighters of the day. The view too the sides was reasonable, although the cockpit canopy was heavily framed. No concessions were made to the rearward view, the aft of the cockpit being faired into a gently sloping fuselage decking. The tailplanes and fins had rounded tips, and the control surfaces were fabric covered. Armament consisted of one .50 in. gun in each wing, and a .50 in. and a .30 in.in the engine cowl decking. There was also room for 20 small anti-aircraft bombs, stored in the wings.

For the production F4U, the US Navy required some changes, which were logical in itself but had unfortunate side effects. More armor was carried for the pilot and oil tank, which added 68kg to the weight. The armament was changed to six .50 machine guns, three in each wing. The wing bomb bays were deleted. This increase in firepower was needed, but the wing guns displaced the leading edge fuel tanks. To restore an adequate fuel capacity, an additional fuel tank had to be installed in the fuselage. Because it had to be near the center of gravity, there was no other option than moving the cockpit to the rear. The 897 liter self-sealing fuel tank pushed the cockpit 3 feet closer to the tail. The forward view over the engine cowling, already poor in the prototype, was now decidedly bad. This was especially a problem during take-off and landing, because the F4U, like most fighters of its generation, was a tail-dragger. On the other hand, rearward vision was improved a bit by making cutouts in the rear fuselage decking. Vision to the sides and downwards was excellent.

The ailerons were enlarged, the cockpit canopy was made jettisonable, an IFF transponder was fitted, and the tailwheel design changed. The engine of production aircraft was the R-2800-8, rated for 2000hp at an rpm of 2700 for take-off. It had a mechanical two-stage, two-speed supercharger. When all changes were incorporated, the gross weight had increased considerably. The XF4U-1 had weighed 9,337 lbs., but the F4U-1 12,668 lbs. From the 759th aircraft onwards, the framed canopy of the F4U-1 was quickly replaced by a much neater plexiglass "bulb" with small frames. The raising of the seat by 7 in. slightly improved the view over the nose, and the new type also offered some rearward vision. Later this modification was associated with a change of designation to F4U-1A, which was not used at the time. An important change, from the 1550th aircraft, was the installation of the -8W engine with water injection, which allowed higher emergency power to be used at low altitude.

The F4U-1C had four 20mm cannon instead of the six .50s. These guns were the British Hispano Mk.II cannon, known in the USA as the Hispano M2. These weapons protruded far from the leading edge. Production of this version remained limited to 200. They entered combat in April 1945.

The first F4U-4 was delivered to the US Navy on 31 October 1944. The F4U-4 was powered by a C-series Double Wasp engine. The installed model was the R-2800-18W, later replaced by the R-2800-42W. It had a war emergency power of 2760hp. A four-bladed propeller replaced the three-bladed one of the F4U-1. A chin scoop was added to the underside of the engine cowling. During the F4U-4 production, the cockpit was redesigned again. It now incorporated a flat, bullet-proof windscreen, a revised canopy, an armored seat, and an improved instrument panel. Production included 2050 F4U-4s with six .50 guns or the F4U-4C with four 20 mm cannon. The F4U-4 arrived late in WWII, and served only during the last four months of the conflict.

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