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The Chance Vought F4U-5N Corsair Guillows Kit #1004

Entering the design competition for a new carrier based monoplane fighter, the Chance Vought Company contracted with the U.S. Navy for a single prototype aircraft in June 1938. Chance Vought engineers set out to design the smallest possible airframe around the most powerful engine then available.

However, problems plagued the project early. The selection of a fourteen foot diameter four-blade propeller meant that the forward fuselage had to be kept well clear of the ground and carrier deck. This, in turn, required a tall fragile undercarriage -- a quality highly unsuitable for rough carrier landings. The solution was the inverted gull wing configuration, destined to become the trademark of the Corsair.

The main landing gear was repositioned at the elbow of the wing, making the gear more compact and robust as required for carrier operations. Designated F4U, the new airplane made its maiden flight on 29 May 1940 and later exceeded the 400-mph mark, the first American fighter to accomplish that feat.

With the cockpit located so far aft, pilots flying the Corsair on board carriers had difficulty with visibility when the plane was nose high, resulting in numerous take-off and landing mishaps.

This quickly prompted restriction of the aircraft exclusively to shore-based squadrons. Eventually, training improved and Corsair squadrons returned to the carrier decks later in the war.

The F4U saw extensive action throughout the Pacific Theater, flown by American Navy and Marine pilots as well as the air arms of Britain and New Zealand. Many of the highest scoring Allied aces in the Pacific flew the Corsair, including Ira Kepford and the legendary Greg "Pappy" Boyington, the top Marine ace of the War.

The end of the Pacific War did not bring about the end of F4U combat operations. The F4U-4 and -5, more advanced models of the Corsair, saw heavy action during the Korean War.

For the most part, the former served in the ground-attack role hauling bombs, napalm and air-to-ground rockets against Communist forces while the -5 variant was modified into a night fighter. Later, Corsairs saw action with the French in Indo-China and the Mid-East, and in numerous Latin American conflicts of the 1950's and '60s.

The Corsair was one of the best carrier based aircraft of the War. During the mid 1930's the US Navy planned for an improved carrier force, first improving on the 'Yorktown' class that later was designated 'Essex' class. 32 of these ships were ordered, 29 completed. The Essex class was considerably larger than it's predecessors, which enabled the US Navy to look at advanced aircraft types as well. The Vought-Sikorsky Division of the United Aircraft Corporation set off for an advanced fighter type that would be at least one generation ahead of the types that were scheduled to enter service in the near future, being for example the Brewster F2A and the Grumman F4F. In 1943 Vought and Sikorsky were split into the Chance Vought Division and the the Sikorsky Aircraft Division. The first was to concentrate on fixed-wing aircraft, the second to concentrate on rotary-wing aircraft (helicopters). When after the War an anti-trust law forced the UAC to split up into various companies, Chance Vought Aircraft Inc was born.

In 1936 Vought started a new design for a carrierborne fighter based on the most powerful engine available at that moment, the Pratt & Whitney R-2800 Double Wasp twin-row radial that was still under development. The design project was designated V-166A. This engine already delivered some 1,850 hp (1.379 kW) and it was expected that it would deliver more than 2,000 hp (1.491 kW) before tests and initial design would be completed. This high output rate demanded a large propeller in order to make use of the engine power, some calculations showed that the diameter would need to be 13 ft 4 inch (4,06 m) for a three-blade unit. To this the needed clearance of 1 ft 6 inch (0,46 m) would be added, which resulted in a landing gear of about 6 ft (1,83 m) long, totally unacceptable for a carrierborne fighter. Firstly the gear would be too vulnerable to damage due to the rougher landings than on land, and secondly the long gear would give the fighter a very high nose-attitude, blocking forward visibility which was very important on an aircraftcarrier. These problems led to the V-166B design which featured the famous inverted gull wings of all subsequent versions. The gear was subsequently attached to the lowest part of the wing, the angle between the inboard and the outboard wing panels. Still there was enough ground clearance for the propeller, and the nose height was minimized given the circumstances. The comparatively short main landing gear legs retracted to the rear and turned through 90° as they retracted so that each wheel lay flat in the undersurface of the wing. Another advantage of the inverted gull wing, which was located in the low-set position, was that it ensured a 90° junction between the inner wing panels and the fuselage for minimum wetted area and thus the smallest possible drag figure. This was a consideration of signal importance in a fighter that was being optimized for the highest possible performance, and other drag-reducing features were the adoption of a semi-retractable tailwheel that was combined with the ‘stinger’ type of arrester hook that was provided for carrierborne landings, a basically all-metal structure that used spot-welded rather than riveted skinning for great smoothness, and the location of the oil coolers in the wing-root inlets that provided air for the engine’s supercharger. Hot air from the coolers was dumped into the freestream air through adjustable doors in the lower surfaces of the wings. Another feature adopted at the design stage for the first time in a US Navy fighter was a wing-folding mechanism so that the outer wing panels could be hinged upward and inward to reduce carrierborne stowage problems.

The US Navy ordered one XF4U-1 prototype in Februari 1938 while it demanded some remarkable additional features: one was the XR-2800-4 radial engine rated at 1,850 hp (1.379 kW) for take-off and 1,460 hp (1.089 kW) at 21,500 ft (6.555 m), while the other comprised the combination of 1 × 0.3 in (7,62 mm) and 1 × 0.5 in (12,7 mm) synchronized machine gun in the upper side of the forward fuselage (originally 2 × 0.3 inch/7,62 mm guns with 500 rounds per gun), 2 × 0.5 inch (12,7 mm) unsynchronized machine guns in the wings with 200 rounds per gun and provision for later replacement by a pair of 23 mm Madsen cannon, and 20 × 8.8 lb (4 kg) light bombs in two small bays in the wings. These bombs were contact-fused weapons that were to be released above bomber formations with the aid of a sighting panel let into the underside of the lower fuselage. When in Februari 1939 wind tunnel tests proved the concept with the mock-up, real production of the first prototype started. This was an aircraft with a comparatively low canopy characterized by a heavily framed section that was designed to slide rearward so that the pilot could enter and leave the cockpit, and its empty and maximum take-off weights were 7,505 and 9,357 lb (3.404 and 4.244 kg) respectively with a maximum fuel load of 229.8 Imp gal (276 US gal, 1.045 liters) carried in integral tanks along the wing leading edges. It was basically of all-metal construction, though the control surfaces and the wing aft of the main spar were fabric covered. The whole airframe was particularly strong, especially the forward and central fuselage sections that had to withstand the power of the engine and the aerodynamic loads transmitted from the wings. The prototype first flew in May 1940, and from the beginning of the flight test program the XF4U-1 showed excellent performance. In October 1940 it became the first fighter of American design to attain a level speed in excess of 403 mph (649 km/h). Other performance figures were an initial climb rate of 2,660 ft (811 m) per minute and a service ceiling of 35,200 ft (10.730 m). The XF4U-1 was not without it's drawbacks, and it turned out to be a somewhat temperamental aircraft. During testing it made a forced landing twice, the second time it was damaged extensively. Because of the advanced nature of the fighter every effort was given to try and solve the problems and large number of handling dificulties that were revealed during testflights. Therefor it was December 1942 before the first prototype was finally delivered, while in the meantime already some 100 production aircraft were delivered to the US Navy simultaneously as well. The design team had sought to solve all complaints of the pilots, which included slow aileron response, poor low-speed handling, inadequate forward fields of vision during take-off and landing, a tendency to drop a wing just before landing as a result of torque stall, a tendency to bounce on landing, and lack of directional control after landing.

During the time of test flying, the US Navy recognised the fact that they had falsely believed the USA would not be drawn in another large scale war. As such they needed an advanced aircraft to be able to fight the seemingly unbeatable Nazi-forces. At the same time they capitalized on the experience that was gained the hard way by the British and French forces. Therefor the first production aircraft differed considerably from the XF4U-1. Production aircraft were able to sustain a high-speed dive by removing the fabric on the wings and replacing it with sheet metal. Span and length were each increased slightly, and the armament was revised. The two fuselage-mounted guns and their heavy synchronization system were removed, and the wing-mounted armament was first increased to four and then 6 × 0.5 inch (12,7 mm) fixed forward-firing machine guns with the considerably enlarged ammunition capacity of 400 rounds per gun for the inboard four weapons and 375 rounds per gun for the outboard two weapons. At the same time the two outer-wing bomblet bays were removed. The revision of the wing-mounted armament meant the elimination the integral leading-edge tanks pioneered in the prototype, and to redress the resulting shortfall in fuel capacity the original small center-section tank was replaced by a large 197 Imp gal (237 US gal, 897 liter) self-sealing tank inserted into the fuselage. This tank had to be located as close to the center of gravity as possible, so the cockpit was moved some 3 ft 0 inch (0,91 m) farther to the rear despite the fact that this relocation further worsened the already inadequate forward fields of vision suffered by the pilot during take-off and landing. The Corsair could carry a centerline drop tank of 146 Imp gal (175 US gal, 662 liter) capacity, but the size of the internal fuel capacity provided by the fuselage tank was still considered inadequate, and two 52 Imp gal (62 US gal; 235 liter) unprotected leading-edge tanks were therefore added outboard of the gun bays in a process that raised the maximum take-off weight with internal fuel to 12,694 lb (5.758 kg) in concert with the addition of IFF (Identification Friend or Foe) gear, a bulletproof windscreen, a jettisonable canopy, and 155 lb (70.3 kg) of armor round the cockpit and oil tankage. These changes increased wing loading by just over 33% from the XF4U-1’s figure of 29.8 lb/sq ft (145,5 kg/m²) to 40.4 lb/sq ft (197,2 kg/m²) and further eroded maneuverability despite the adoption of longer-span ailerons for improved roll response. The negative effect of weight on performance was countered by the adoption of the R-2800-8(B) radial engine rated at 2,000 hp (1.491 kW), and this was installed in a cowling with mechanically rather than hydraulically operated cooling gills in a fuselage lengthened by 1 ft 5 inch (0,43 m) to 33 ft 4 inch (10,16 m) from the XF4U-1’s figure of 31 ft 11 inch (9,73 m), and the pilot’s fields of vision were improved to the rear at least by the adoption of a cutaway headrest and additional transparent panels.

The first F4U-1 made its initial flight in June 1942 and was delivered in the following month just one day after the first example of the Grumman F6F Hellcat with the same engine type, but the US Navy deemed the F4U-1 too tricky for carrierborne operation and initially allocated the type to land-based operation by the US Marine Corps. The initial Corsair unit was VMF-122 created in September 1942. This squadron was declared combat-ready in December of the same year and was shipped to Guadalcanal in the Solomon Islands, where the Corsair flew its first operational mission in mid-February 1943.

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Houston, Texas
E-mail: bparker@parkerinfo.com

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