An Engineering Masterpiece: F4U CORSAIR

In the opening months of 1938, the U.S. Navy Bureau of Aeronautics made a request for a fighter aircraft (destined for carrier operations) that could achieve the highest cruise speed that design and engineering could provide, and – at the other end of the speed envelope – a low enough stalling speed to allow for carrier operations (actually specified as needing to be less than 70 miles per hour), and achieve a range of over 1,000 miles. A company by the name of ‘Vought’ was selected for the job and got the contract. They did an outstanding job producing an aircraft that in later years would go up against (and hold it’s own) such aircraft as the MiG-15! 

Started by Chance 

‘Vought’ was established in 1917 by Chance M. Vought (a former chief engineer of the Wright Company) and a gentleman by the name of Birdseye Lewis. Following multiple changes of ownership and transition through the time that followed it actually ended up being part of Northrop Grumman some 80 years later! Like most manufacturers of aircraft in the dawn of aviation, Vought made history with his developments in aeronautics. In 1922 his aircraft, the ‘Vought VE-7 trainer’ made the first takeoff from the deck of America’s first aircraft carrier, the USS Langley. And it was his knowledge of carrier deck landings that would be needed as they designed their prototype XF4U-1 Corsair. 

For a fighter (or any aircraft for that matter) to land safely on an aircraft carrier (and for it to remain in sufficient condition to make another flight after!) the landing gear needed to be very strong. So, a short, stout leg was on the drawing board from early on. But to give the aircraft sufficient power they needed a big engine. And I mean a BIG engine; the Pratt-Whitney R-1830 Wasp (which through development became the R-2800 Double Wasp). However, it wasn’t the bulk size of the engine that was the issue. It was the 13 ft propeller (13ft 4 inches to be exact)! To achieve prop clearance, it needed to be sufficiently high enough off the ground but also needed those short legs I mentioned.

Being an aircraft designer wasn’t easy! But solve the issue they did, and the solution became one of the most distinctive features of the aircraft; the inverted gull-wing. This ‘bent wing’ design allowed the huge prop to clear the deck and provided adequate space to accommodate a nice short (relative) landing gear. 

Another feature of the gull wing was its ability to fold for storage. Space on an aircraft carrier was (and still is) very limited. So, making use of the aircraft hydraulic system, each wing could be folded up vertically allowing more aircraft to be parked on deck. But the engineers and design team didn’t stop there, to seek out speeds at the higher end of the envelope, they designed the wheels to swivel 90 degrees so they could retract and fit flush inside the wing. The tailwheel and arrestor hook also retracted flush into the airframe. And to keep the aircraft surfaces as aerodynamically clean as possible, they used large section panels that were attached to the frame using spot welding, this eliminated the use of rivets common to so many other types and helped produce a beautiful clean surface. Indeed, the aircraft had nothing non-essential protruding into the airflow. And this all counted in the performance department; during testing dive speeds approaching 550 mph were achieved making it one of the fastest prop driven aircraft in the sky!

Power of the Wasp 

The beast of an engine finally selected was the Pratt-Whitney R-2800 ‘Double Wasp’ radial engine, this whopping great powerplant had a two-stage supercharger and in the year of 1940 was the most powerful aircraft engine in the world! It’s 18 cylinders, each produced over 100 hp each! In fact, there were so many cylinders they couldn’t fit them wrapped once around the engine, they had to wrap them round twice (hence the ‘Double’ Wasp). The 46 litre air-cooled radial engine could produce 2,760 hp at its war emergency power rating (a five minute limit for extended power…). And as already noted above, the only way to convert that kind of horsepower into sufficient thrust was with a huge Hamilton Standard Hydromatic propeller. This boasted a double-acting governor and used oil pressure on both sides of the propeller piston allowing for a greater blade angle range. And with its 3 enormous blades spinning, it measured 13 feet 4 inches across the prop diameter.

Jet combat performance 

The first flight of the prototype XF4U-1 was made on 29 May 1940, and only a few months after a later example clocked a cruise speed of 405 miles per hour becoming the first production aircraft to exceed 400 mph. The US Navy seemed quite pleased with the results and during the summer of 1941 they placed an order for just under 600 aircraft. Over the next 11 years that figure grew to reach a production number of over 12,500 aircraft! And with all good models, testing and development continued, indeed Charles Lindbergh flew the aircraft as a civilian technical advisor and advancements in design were found, as was an upward trend of the air speed indicator; the aircraft proceeded to reliably clock a top speed of 446 mph! aka Jet Speed! But, at that kind of speed, some issues were evident; the fabric covered control surfaces began to deform, increasing drag which progressively slowed the aircraft down by a few miles per hour. That was fixed however by replacing the fabric surfaces with metal surfaces (duralumin) which alleviated the problem. It was on these examples that during full-power dive tests from 45,000 ft, those speeds of up to 550 mph were reached (45,000 ft... that's higher than the service ceiling of a Boeing 747!). 

Carrier landings were initially a challenge in the Corsair, that very long nose (14 ft in front of the pilot) caused difficulty seeing the touchdown point and in keeping signalling marshaller in sight, and the aircraft stall characteristics in the landing configuration were most unforgiving. During testing with the British, test pilots evaluated this and adopted a new approach (literally), which significantly improved matters for carrier landings; instead of the normal circuit pattern of downwind, crosswind, final approach, the pilot was recommended, once established downwind, to make a slow continuous curved approach, whilst this delayed the aircraft being lined up with the runway deck until almost landing on it, it did allow the pilot to keep the signals marshaller in view (not to mention the back of the ship!) 

The Corsair is undoubtedly a stunning looking aircraft, but it was so much more from a design and engineering point of view. It was a masterpiece! Fast, powerful, and versatile, and if you’re lucky enough to see one up close you can’t help but stand and stare in wonder and its size and presence. A truly impressive aircraft. 

Vought F4U Corsair

Wingspan: 12.5 m
Length: 9.99 m
Height: 4.58 m
MGW: 6,350 kg
Powerplant: 2,325 hp
VNE: 446 mph (IAS)
Cruise speed: 215 mph (IAS)
Service ceiling: 41,500 ft

More info:  www.TASCVintage.com