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Despite the ability to create a more streamlined and aerodynamic design with inline engines, the U.S. Navy stayed with the radial engine design, asking Pratt & Whitney to develop the largest and most powerful radial aircraft engine at the time.

During the late 1930s, the trend for power plants for fighter aircraft was shifting more and more towards inline engines. Pratt & Whitney was even asked by the U.S. Army Air Corps (USAAC) to concentrate on developing inline liquid cooled engines and abandon the radial all together. However, the U.S. Navy (USN) recognized the advantages of the radial and that development of the design was essential for their uses.

In 1938, the USN issued a design completion for a new shipboard fighter powered by a powerful radial engine. This engine would be so powerful and require such a large propeller that it would strongly influence the design of the new aircraft and create an instantly recognizable aircraft profile, feared by enemies and loved by aviation enthusiasts the world over.

Why the Radial

The USN understood that radials were much simpler to maintain. The design was rugged; it could absorb battle damage and still continue flying. An inline engine was much more susceptible to taking hits in the cooling system that could cause the engine to seize. The cooling systems used with the inline designs also added complexity and required more maintenance. The radial engine was dependable as well.

While not appearing sleek and aerodynamic, the U.S. Navy found the radial engine to be rugged, dependable, and easy to maintain. The R-2800-8 shown here in a Corsair could produce 2,000 horsepower for takeoff.

In Europe, both the Germans and the British had favored the inline designs for the majority of fighter aircraft, but the Japanese stayed with the radial design for most of their fighter aircraft in the Pacific. The German Focke Wulf Fw 190 was also equipped with a radial engine.

The V-166B

With the Navy issuing the design competition in February 1938 demanding a shipboard fighter that could match the best land-based fighters, Vought responded with two designs that were similar. They were known as the V-166A and the V-166B.

The V-166A was to be fitted with the existing Pratt & Whitney R-1830 Twin Wasp engine. The V-166B was to incorporate the new supercharged XR-2800-2, pending successful development of the power plant.

Pratt & Whitney R-2800 radial engine.

The XR-2800-2 Double Wasp was rated at 1,850 horsepower at takeoff, way above anything in the inventory of the USN at the time. In order to harness the available horsepower and put it to good use, Hamilton-Standard produced a huge three-bladed propeller with a diameter of 13 ft 4 in.

The largest propeller ever designed for a fighter aircraft presented challenges to the design team lead by Rex Beisel. Clearance would need to be maintained for takeoffs and landings, moving across the ground on the mainwheels with the nose closer to the ground than it would be when resting on the tailwheel. This would require extremely long main landing gear struts to insure enough clearance. Being a carrier-borne aircraft, long fragile main gear would not hold up well on abrupt landings on carriers.

A propeller from a Vought F4U showing the kill markings of the four squadrons of U.S. Marine Aircraft Group 31, possibly at Yontan Airfield, Okinawa, in 1945. The squadrons are VMF-224, VMF-311, VMF-441 and VMFN-542 night fighting squadron.

Vought’s V-166B featured stub wings that left the fuselage dropping down at an angle with the outer wing panels canting back upwards, giving the aircraft the distinctive inverted gull wing appearance. This allowed the clearance issue for the propeller to be solved by placing the main landing gear at the lowest point in the Vee formed by each wing, allowing a short and rugged landing gear leg.

Flush landing gear stowage was achieved and the outer wing panels folded upwards at the gull wing bend for shipboard storage. The unique wing design allowed the folded wing height to be lower. The outer wing panels would be framed using metal with large areas covered in fabric, rather unusual for American fighters at the time.

Head on view of the design showing the large propeller, short main gear, folding wings, and the cooling intakes in the stub wings.

The inverted gull wing design took advantage of maximum strength because of the angle the wing attached to the fuselage, and it minimized drag. Improved visibility below the aircraft was another benefit of the design. Ditching at sea would also be easier and safer. A new spot welding technique developed by Vought in conjunction with the Navy would give the aircraft a very smooth skin and reduced drag as well.

Open vents in the stub wing leading edge would draw in air for cooling engine oil and air for supercharger cooling equipment. These would be modified on production aircraft, and it would soon be discovered by anyone on the ground in the sights of this aircraft would hear a whistling sound as air rushed through the radiators, with the Japanese naming the aircraft ‘whistling death.’

Close up of the original vent design used on the prototype. These would later be modified on the production models.

The XF4U-1

On Feb. 8, 1939, a full scale mock-up was completed of the V-166B, and Vought was authorized by the Navy to build a single prototype that would be known as the XF4U-1.

The XF4U-1 would be shorter in length than the later production Corsairs at 31 ft 11 in in length. Wingspan was 41 ft, and the empty weight was 7,505 lb with a max takeoff weight of 10,074 lb.

Side view of the XF4U-1.

The aircraft was ready almost 15 months later, and on May 29, 1940, Lyman A. Bullard Jr. made the initial flight. Equipped with an upgraded R-2800-4, the flight lasted 38 minutes, with some problems presenting themselves but nothing serious.

Armament included two .50 caliber machine guns, one in each wing, with 600 rounds available. Two .30 caliber machine guns located in the cowl had 1,500 rounds available. There was also provision for 20 anti-bomber formation bombs.

On the fifth test flight, pilot Boone T. Guyton ran low on fuel and was forced to put the XF4U-1 down on a golf course. In doing so the plane flipped onto its back and crushed the tail section, with the right wing being completely torn from the aircraft. However, the aircraft was repaired and flown again, proving the ruggedness of the design and saving the program.

Colorful image of the XF4U-1. The prototype was painted silver with Chrome Yellow wings (FS 13538) with tri-color propeller tips and flat black lettering. Standard national insignia was placed on all four wing positions.

Early problems included issues with roll control and the port (left) wing stalling before the starboard (right) wing. These issues, and the aircraft’s tendency to bounce on landing, would delay it as being used as a carrier fighter until rectified.

On Oct. 1, 1940, this aircraft became the first American fighter to exceed 400 miles per hour in level flight, prompting General Henry ‘Hap’ Arnold into taking a second look at the powerful R-2800 engine and its possible use in a new USAAC fighter.

Into Production and Into History

On June 30, 1941, Vought was awarded a contract to construct 584 of the first production model Corsair, known as the F4U-1. The type would go on to see several modifications and be produced by three different firms including Brewster and Goodyear joining Vought.

A Vought F4U-1 Corsair fighter in flight 1942. Most were delivered wearing a two-tone scheme of non-specular Blue Gray (FS 35189) and non-specular Light Gray (FS 36440). The red disk was removed from the national insignia on May 20, 1942 to avoid confusion with the Japanese insignia.

The Corsair would find huge success in the Pacific Theater of World War 2 and went on to serve in Korea as well as serving with other nations and in other conflicts. Its legendary performance and distinct inverted gull wing silhouette have been known and respected throughout the aviation community for decades and still is today as one of the most effective and beautiful piston-engine designs ever created.