F4U Corsair

Early in the Pacific War, US Navy and Marine Corps fighter pilots found themselves outclassed by the agile and well-armed Japanese A6M Zero, but even then work was underway to provide them with better aircraft. One of those better aircraft was the Vought "F4U Corsair", a rugged, powerful, and somewhat unforgiving aircraft that featured a distinctive inverted gull wing. The Corsair proved more than a match for the Zero, and it would also prove to be an excellent fighter-bomber, serving in this role in the Korean War and in the French colonial wars in Indochina and Algeria.

Such a large engine needed a big propeller to soak up the power, and so the design featured a 4.06 meter (13 foot 4 inch) three-blade variable-pitch constant-speed propeller designed by Hamilton Standard, yet another UAC division. The big propeller posed a problem for the design team. It dictated long landing gear so that the prop arc would clear the ground on takeoffs and landings, but long landing gear tended to be too weak to tolerate hard carrier landings. The designers came up with the notion of a low-mounted "inverted gull wing" or "cranked wing", in which the wings bent down from the root and then back up to the tip, with the main landing gear at the lowest point of the wing. The wing arrangement also improved the pilot's field of view, and the right-angle connection between the wing and the fuselage improved aerodynamics.

Vought engineers completed a full-scale mockup of the XF4U-1 in early 1939 for wind tunnel tests and Navy inspection. The initial flight of the prototype XF4U-1 was on 29 May 1940, with Vought chief test pilot Lyman A. Bullard JR at the controls. The aircraft suffered from excessive vibration and Bullard was in an agitated mood when he got back to the ground. The prototype was badly damaged in July, when storms prevented test pilot Boone T. Guyton from reaching the Vought airfield at Stratford, Connecticut. He was running low on fuel and couldn't raise any other airfield on his radio, so he tried to put the machine down on a golf course at Norwich, Connecticut. He touched down properly, but the grass was slick with rain and he plowed into trees, flipping the aircraft over and around. One wing was torn off, the fuselage was bashed up, but Guyton was little more than shaken and bruised, thanks to the toughness of the design.

The prototype was rebuilt in a few months, and demonstrated the design's performance on 1 October 1940, clocking 650 KPH (404 MPH). However, the promise of the type was balanced by continuing difficulties, including a nasty tendency of the Double Wasp engine to catch on fire; a tendency of the engine to conk out at high altitude; and some clear handling problems, such as bad spin recovery. Some things were fixed, others were inherent in the design -- when Boone Guyton was later asked by Navy pilots about spinning the F4U, his answer was minimal: "Don't."

The problems clearly meant delays in getting the type into production. To compound the delays, reports coming back from the war in Europe indicated that an armament of two 7.62 millimeter and two 12.7 millimeter machine guns was too light, and so when the US Navy asked for production proposals in November 1940, heavier armament was specified. The twin 7.62 millimeter Brownings in the nose were eliminated and two 12.7 millimeter Brownings were fitted in each wing. The wing guns were staggered to avoid mechanical interference between their ammunition feeds. The armament change required considerable design adjustments that piled up more delays.

There was another troublesome consequence: putting all the guns in the wings meant eliminating wing fuel tankage, and so the forward fuselage was stretched by 45 centimeters (18 inches) to include a new self-sealing tank in the center of the fuselage. The fuel tank also meant moving the cockpit back by about 91 centimeters (3 feet), which made it hard for a pilot to see over the nose when taxiing, taking off, or landing. There would never be any way around the long nose, one pilot later recollecting that he used to tell himself after he lined up for the approach: "God, I hope there's nobody on that runway!"

* Formal naval acceptance trials for the XF4U-1 began in February 1941, and the initial Navy production order for 584 "F4U-1s" was placed on 30 June 1941. The type was given the name "Corsair", which had been the name of several prewar Vought aircraft. The first production F4U-1 performed its initial flight on 24 June 1942, once again with Boone Guyton at the controls.

The type quickly underwent a few more improvements, with the number of 12.7 millimeter Brownings in each wing increased to three, for a total of six; the addition of 70 kilograms (155 pounds) of armor around the cockpit and the oil tank, plus an armor glass windscreen and self-sealing fuel tanks; fit of shorter flaps and wider ailerons; and installation of an uprated R-2800-8 Double Wasp engine with a two-stage supercharger and 1,490 kW (2,000 HP) takeoff power to handle the aircraft's increased weight.

The US Navy received its first production F4U-1 on 31 July 1942, with carrier trials beginning on the USS SANGAMON on 25 September 1942. Getting the machine into service proved difficult. The framed "birdcage" style canopy provided inadequate visibility for deck taxiing, a serious concern given the kind of damage the oversize prop could do to anybody or anything that got in its way. Even more seriously, the machine had a nasty tendency to "bounce" on touchdown, which could cause it to miss the arresting hook and slam into the crash barrier, or even go out of control. The long "hose nose" visibility problem has already been mentioned, and there was the inevitable issue of the enormous torque of the Double Wasp: if a pilot was waved off a carrier landing, he would throttle up and bank off to the left for another pass, and the Corsair had a nasty tendency to flip over on its back if revved up incautiously. Yet another peculiarity was that, due to propwash effects, the left wing would stall before the right on the landing approach, which tended to make the aircraft roll to the left as well.

Production was going ahead anyway, with Vought building 178 Corsairs by the end of 1942. The company was working with the Marine Corps, which saw the potential of the type and by nature was less intimidated than the Navy by the aircraft's unpleasant features, to work out the bugs in parallel with production. Although the Navy would come to accept the F4U, the Corsair would always be more of a Marine than a Navy fighter. The type was declared "ready for combat" at the end of 1942, though it was originally only qualified to operate from land bases until carrier qualification issues were worked out.

A dozen F4U-1s arrived at Henderson Field on Guadalcanal in the Solomon Islands on 12 February 1943. The US Navy didn't get into combat with the type until September 1943, and in fact the British Royal Navy's Fleet Air Arm (FAA) would qualify the type for carrier operations first.

The F4U-1 was of basically conventional monocoque construction, made mostly of metal, although the ailerons had wood frames and plywood skinning, while the rudder, elevators, and outer wings had metal frames and fabric skinning. The flaps were all metal. The tailfin was slightly offset from the centerline to help compensate for engine torque. There were trim tabs on the ailerons and the rudder.

The Corsair was exceptionally strong and featured substantial armor protection. The main landing gear was fitted into the inner wing section, just inside the "bend" where the wing fold was, and rotated 90 degrees to lie flat inside the wing. The tailwheel was semi-retractable. There was a stinger-type arresting hook just behind the tailwheel.

There were inlets in the leading edge of the wings near the wingroot for the supercharger and oil cooler system. Although the original internal wing fuel tanks had been removed, the design team figured out how cram a small tank into each outer wing. The wings hydraulically folded straight up toward the aircraft centerline. The three Browning machine guns in each wing were just outboard of the wing fold. The two inner guns had an ammunition capacity of 400 rounds per gun each, while the outer gun had 375 rounds per gun, with the pilot aiming the guns with a reflector-type gunsight. The F4U-1 could carry a centerline external fuel tank with a capacity of 662 liters (175 US gallons).

The F4U-1, as mentioned, originally had a framed, backwards sliding canopy, with "cutouts" behind it like those used on the Curtiss P-40 Warhawk, to improve rearward visibility. Electronics included a multichannel radio and the new "identification friend or foe (IFF)" set, developed by the British. The cockpit was roomy by the standards of the time. A typical early color scheme was two-tone light and medium blue on top, with light gray on the bottom.

Some F4U-1s were modified in the field for the photo-reconnaissance role and designated "F4U-1P". They were fitted with a vertically mounted K-21 camera in the belly, between the trailing edge of the wing and the tailwheel. The number of conversions is unclear.

* As mentioned, the Corsair's initial deficiencies were being worked out on a concurrent basis. The tendency to "bounce" on landings, due to the excessive stiffness of the shock absorber elements in the main landing gear struts, was greatly reduced after Vought engineers tweaked the stiffness to get the right value. The 689th production F4U-1 featured a number of significant changes. The most noticeable was that the cockpit was raised 18 centimeters (7 inches) to improve the pilot's forward view, and a clear-view bulged canopy, along the lines of the "Malcolm Hood" used on later model Spitfires, replaced the original "birdcage" framed canopy to provide better all-round field of view.

Other changes included a raised tailwheel leg, with a pneumatic instead of solid tire, to improve the pilot's forward view on the ground; and an almost unnoticeable 15 centimeter (6 inch) fixed "stall strip" that was fitted to the leading edge of the right wing outboard of the guns to ensure that both wings stalled at the same time on landing approach. The 1,550th production F4U-1 introduced an R-2800-8W engine with water-methanol injection for boost power of 1,664 kW (2,230 HP).

   VOUGHT F4U-1A CORSAIR:
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   spec                    metric              english
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   wingspan                12.49 meters        41 feet
   wing area               29.17 sq_meters     314 sq_feet   
   length                  10.16 meters        33 feet 4 inches
   height                  4.9 meters          16 feet 1 inch

   empty weight            4,074 kilograms     8,892 pounds
   MTO weight              6,350 kilograms     14,000 pounds

   max speed at altitude   671 KPH             417 MPH / 363 KT
   service ceiling         11,250 meters       36,900 feet
   range                   1,633 kilometers    1,015 MI / 883 NMI
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