Corsair

The F4U incorporated the largest engine available at the time: the 2,000 hp (1,500 kW) 18-cylinder Pratt & Whitney R-2800 Double Wasp radial. To extract as much power as possible, a relatively large Hamilton Standard Hydromatic three-blade propeller of 13 feet 4 inches (4.06 m) was used. To accommodate a folding wing, the designers considered retracting the main landing gear rearward, but for the chord of wing that was chosen, it was difficult to make the landing gear struts long enough to provide sufficient clearance for the large propeller.

Their solution was an inverted gull wing, which considerably shortened the required length of the main gear legs.] The anhedral of the wing’s center-section also permitted the wing and fuselage to meet at the optimum angle for minimizing drag, without using wing root fairings. Offsetting these benefits, the bent wing was heavier and more difficult to construct.

The Corsair’s aerodynamics were an advance over those of contemporary naval fighters. The F4U was the first U.S. Navy aircraft to feature landing gear that retracted into a fully enclosed wheel well. In a similar manner to that of the Curtiss P-40 the landing gear oleo struts rotated through 90° during retraction, with the wheel atop the lower end of the strut; a pair of rectangular doors completely enclosed the wheel wells, leaving a completely streamlined wing. This swiveling, aft-retracting landing gear design was common to the Curtiss P-40 (and its predecessor, the Curtiss P-36), as well as the F4U Corsair and its erstwhile Pacific War rival, the Grumman F6F Hellcat.

The oil coolers were mounted in the center-section of the wings, alongside of the supercharger air intakes, and used openings in the leading edges of the wings, rather than protruding scoops. The large fuselage panels were made of aluminum and were attached to the frames with the newly-developed technique of spot welding, thus mostly eliminating the use of rivets.

While employing this new technology, the Corsair was also the last American-produced fighter aircraft to feature fabric as the skinning for the top and bottom of each outer wing, aft of the main spar and armament bays, and for the ailerons, elevators and rudder. In addition, the elevators were constructed from plywood. Even with its streamlining and high speed abilities, with full flap deployment of 60°, the Corsair could fly slowly enough for carrier landings.

In part because of its advances in technology and a top speed greater than existing Navy aircraft, numerous technical problems had to be solved before the Corsair would enter service. Carrier suitability was a major development issue, prompting changes to the main landing gear, tail wheel and tailhook. Early F4U-1s had difficulty recovering from developed spins, since the inverted gull wing’s shape interfered with elevator authority. It also found that the Corsair’s starboard wing could stall and drop rapidly and without warning during slow carrier landings.

In addition, if the throttle were suddenly advanced (for example, during an aborted landing) the port wing could stall and drop so quickly that the fighter could flip over with the rapid increase in power. These potentially lethal characteristics were later solved through the addition of a small, 6 in (150 mm)-long stall strip to the leading edge of the outer starboard wing, just inboard of the gun ports. This allowed the starboard wing to stall at the same time as the port.[23] An early F4U-1 showing the “birdcage” canopy with rearwards production cockpit location. Compare with the XF4U-1.

Other problems were encountered during early carrier trials. The combination of an aft cockpit and the Corsair’s long nose made landings hazardous for newly-trained pilots. During landing approaches it was found that oil from the hydraulic cowl flaps could spatter onto the windscreen, badly reducing visibility, and the undercarriage oleo struts had bad rebound characteristics on landing, allowing the aircraft to bounce out of control down the carrier deck.

The first problem was solved by locking the top cowl flap down permanently, then replacing it with a fixed panel. The undercarriage bounce took more time to solve but eventually a “bleed valve” incorporated in the legs allowed the hydraulic pressure to be released gradually as the aircraft landed. The Corsair was not considered fit for carrier use until the wing stall problems and the deck bounce could be solved. In the event, because the more docile, and simpler to build F6F Hellcat had begun entering service, Corsair deployment aboard U.S. carriers was to be delayed until late 1944.]

Production F4U-1s featured several major modifications compared with the XF4U-1. A change of armament to six wing mounted .50 in (12.7 mm) M2 Browning machine guns (three in each outer wing panel) and their ammunition (400 rpg for the inner pair, 375 rpg for the outer)[25] meant that the location of the wing fuel tanks had to be changed. In order to keep the fuel tank close to the center of gravity, the only available position was in the forward fuselage, ahead of the cockpit.

Accordingly a 237 gal (897 l) self-sealing fuel tank replaced the fuselage mounted armament, the cockpit had to be moved back by 32 in (810 mm) and the fuselage lengthened. In addition, 150 lb of armor plate was installed, along with an 1.5 in (38 mm) bullet-proof windscreen which was set internally, behind the curved Plexiglas windscreen. The canopy could be jettisoned in an emergency and curved transparent panels, providing the pilot with a limited rear view over his shoulders, were inset into the fuselage, behind the pilot’s headrest. A rectangular Plexiglas panel was inset into the lower center-section to allow the pilot to see directly beneath the aircraft and assist with deck landings.

The engine used was the more powerful R-2800-8 (B series) Double Wasp which produced 2,000 hp (1,491 kW). On the wings the flaps were changed to a NACA slotted type and the ailerons were increased in span to increase the roll rate, with a consequent reduction in flap span. IFF transponder equipment was fitted in the rear fuselage. All in all these changes increased the Corsair’s weight by several hundred pounds.

In September 1942, new issues arose with the Corsair when it underwent carrier qualification trials. Already a difficult aircraft to land, numerous problems were found with its main landing gear, tail wheel and tailhook. As the Navy also had the F6F Hellcat coming into service, the decision was made to release the Corsair to the US Marine Corps until the deck landing problems could be resolved. First arriving in the Southwest Pacific in late 1942, the Corsair appeared in larger numbers over the Solomons in early 1943.

Marine pilots quickly took to the new aircraft as its speed and power gave it a decisive advantage over the Japanese A6M Zero. Made famous by pilots such as Major Gregory “Pappy” Boyington (VMF-214), the F4U soon began to rack up impressive kill numbers against the Japanese. The fighter was largely restricted to the Marines until September 1943, when the Navy began flying it in larger numbers. It was not until April 1944, that the F4U was fully certified for carrier operations. As Allied forces pushed through the Pacific the Corsair joined the Hellcat in protecting US ships from kamikaze attacks.

In addition to service as a fighter, the F4U saw extensive use as a fighter-bomber providing vital ground support to Allied troops. Capable of carrying bombs, rockets, and glide bombs, the Corsair earned the name “Whistling Death” from the Japanese due to sound it made when diving to attack ground targets. By the end of the war, Corsairs were credited with 2,140 Japanese aircraft against losses of 189 F4Us for an impressive kill ratio of 11:1. During the conflict F4Us flew 64,051 sorties of which only 15% were from carriers. The aircraft also saw service with other Allied air arms.

Retained after the war, the Corsair returned to combat in 1950, with the outbreak of fighting in Korea. During the early days of the conflict, the Corsair engaged North Korean Yak-9 fighters, however with the introduction of the jet-powered MiG-15, the F4U was shifted to a purely ground support role.

Used throughout the war, special purpose-built AU-1 Corsairs were constructed for use by the Marines. Retired after the Korean War, the Corsair remained in service with other countries for several years. The last known combat missions flown by the aircraft were during the 1969 El Salvador-Honduras Football War.