Vought F4U Corsair
The Vought F4U Corsair was a carrier-capable fighter aircraft that
saw service primarily in World War II and the Korean War. Demand for the
aircraft soon overwhelmed Vought's manufacturing capability, resulting in
production by Goodyear and Brewster: Goodyear-built Corsairs were designated FG
and Brewster-built aircraft F3A. From the first prototype delivery to
the U.S. Navy in 1940, to final delivery in 1953 to the French, 12,571 F4U
Corsairs were manufactured by Vought, in 16 separate models, in the longest
production run of any piston-engined fighter in U.S. history (1942–1953).
The Corsair served in the U.S. Navy, U.S. Marines, Fleet Air Arm and the Royal
New Zealand Air Force, as well as the French Navy Aeronavale
and other, smaller, air forces until the 1960s. It quickly became the most
capable carrier-based fighter-bomber of World War II. Some Japanese pilots
regarded it as the most formidable American fighter of World War II, and the U.S. Navy counted an 11:1 kill ratio
with the F4U Corsair. 
Development
In February 1938, the U.S. Navy
Bureau of Aeronautics published two requests for proposal for twin-engined and single-engined
fighters. For the single-engined fighter the Navy requested the maximum
obtainable speed, and a stalling speed not higher than 70 miles per hour
(110 km/h). A range of 1,000 miles (1,600 km) was specified. The
fighter had to carry four guns, or three with increased ammunition. Provision
had to be made for anti-aircraft bombs to be carried in the wing. These small
bombs would, according to thinking in the 1930s, be dropped on enemy aircraft
formations.
In June 1938, the U.S. Navy signed a
contract for a prototype, the XF4U-1, BuNo 1443. The Corsair was designed by Rex Beisel and the Vought
design team. After mock-up inspection in February 1939, construction of the
XF4U-1 powered by an XR-2800-4 prototype of the Pratt & Whitney Double Wasp twin-row,
18-cylinder radial engine,
rated at 1,805 hp (1,346 kW) went ahead quickly. When the prototype
was built it had the biggest and most powerful engine, largest propeller and
probably the largest wing on any fighter in history. The first flight of the
XF4U-1 was made on 29 May 1940, with Lyman A. Bullard, Jr. at the controls. The
maiden flight proceeded normally until a hurried landing was made when the
elevator trim tabs failed because of flutter.
On 1 October, the XF4U-1 became the
first single-engine U.S. fighter to fly faster than 400 mph
(640 km/h) by setting an average ground speed of 405 miles per hour
(652 km/h) during a flight from Stratford to Hartford. The XF4U-1 also had an excellent rate of
climb but testing revealed that some requirements would have to be rewritten.
In full-power dive tests, speeds of up to 550 miles per hour (890 km/h)
were achieved but not without damage to the control surfaces and access panels
and in one case, an engine failure. The spin recovery standards also had to be
relaxed as recovery from the required two-turn spin proved impossible without
resorting to an anti-spin chute. The problems clearly meant delays in getting
the type into production.
Reports coming back from the war in
Europe indicated that an armament of two .30 in (7.62 mm) (mounted in
engine cowling) and two .50 in (12.7 mm) machine guns (one in each
outer wing panel) was insufficient, so when the U.S. Navy asked for production proposals in
November 1940, heavier armament was specified. The Navy entered into a letter
of intent on 3 March 1941, received Vought's production proposal on 2 April and
awarded Vought a contract for 584 F4U-1 fighters on 30 June of the same year.
It was a remarkable achievement for Vought; compared to land-based
counterparts, carrier aircraft
are "overbuilt" and heavier, to withstand the extreme stress of deck
landings.
Design
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
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) 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.
Operational history
United States Navy and Marine Corps
The
performance of the Corsair was impressive. The F4U-1 was considerably faster
than the F6F Hellcat and only 13 mph (21 km/h) slower than the P-47
Thunderbolt, all three were powered by the R-2800. But while the P-47 achieved
its highest speed at 30,020 feet (9,150 m) with the help of an intercooled
turbosupercharger, the
F4U-1 reached its maximum speed at 19,900 ft (6,100 m), and used a
mechanically supercharged engine.
Carrier
qualification trials on the escort carrier USS Sangamon, on 25
September 1942, caused the U.S. Navy to release the type to the United States
Marine Corps. Early Navy
pilots spoke disparagingly of the F4U as the "hog",
"hosenose" or "bent wing widow-maker". After
all, the U.S. Navy still had the Grumman F6F Hellcat, which did not have the
performance of the F4U but was a far better deck landing aircraft. The Marines
needed a better fighter than the F4F Wildcat. For them it was not as important
that the F4U could be recovered aboard a carrier, as they usually flew from
land bases. Growing pains aside, Marine Corps squadrons readily took to the
radical new fighter.
Despite
the decision to issue the F4U to Marine Corps units, two Navy units, VF-12
(October 1942) and later VF-17 (April 1943) were equipped with the F4U. By
April 1943, VF-12 had successfully completed deck landing qualification.
However, VF-12 soon abandoned its aircraft to the Marines. VF-17 kept its
Corsairs, but was removed from its carrier, USS Bunker Hill, due to
perceived difficulties in supplying parts at sea. In November 1943, while
operating as a shore-based unit in the Solomon Islands, VF-17 reinstalled the
tail hooks so its F4Us could land and refuel while providing top cover over the
task force participating in the carrier raid on Rabaul. The squadron's pilots
landed, refueled, and took off from their former home, Bunker Hill and
the USS Essex on 11 November 1943.
The
U.S. Navy did not get into combat with the type until September 1943 and the Royal
Navy's FAA would qualify the type for carrier operations first. The U.S. Navy
finally accepted the F4U for shipboard operations in April 1944, after the
longer oleo strut was fitted, which finally eliminated the tendency to bounce.
The first Corsair unit to be based effectively on a carrier was the pioneer
USMC squadron, VMF-124, which joined Essex. They were accompanied by VMF-213.
The increasing need for fighter protection against kamikaze attacks
resulted in more Corsair units being moved to carriers.
From
February 1943 onward, the F4U operated from Guadalcanal and ultimately other
bases in the Solomon Islands. A dozen USMC F4U-1s of VMF-124, commanded by Major
William E. Gise, arrived at Henderson Field (code name "Cactus") on
12 February. The first recorded combat engagement was on 14 February 1943, when
Corsairs of VMF-124 under Major Gise assisted P-40s and P-38s in escorting a formation of B-24 Liberators on a raid
against a Japanese aerodrome at Kahili. Japanese fighters contested the
raid and the Americans got the worst of it, with four P-38s, two P-40s, two
Corsairs and two Liberators lost. No more than four Japanese Zeros were
destroyed. A Corsair was responsible for one of the kills, although this was
due to a midair collision. The fiasco was referred to as the "Saint
Valentine's Day Massacre". Although the Corsair's combat debut
was not impressive, the Marines quickly learned how to make better use of the
aircraft and started demonstrating its superiority over Japanese fighters. By
May the Corsair units were getting the upper hand, and VMF-124 had produced the
first Corsair ace, Second Lieutenant Kenneth A. Walsh, who would rack up a
total of 21 kills during the war.
I learned quickly that
altitude was paramount. Whoever had altitude dictated the terms of the battle,
and there was nothing a Zero pilot could do to change that — we had him. The
F4U could out-perform a Zero in every aspect except slow speed manoeuvrability
and slow speed rate of climb. Therefore you avoided getting slow when combating
a Zero. It took time but eventually we developed tactics and deployed them very
effectively... There were times, however, that I tangled with a Zero at slow
speed, one on one. In these instances I considered myself fortunate to survive
a battle. Of my 21 victories, 17 were against Zeros, and I lost five aircraft
in combat. I was shot down three times and I crashed one that ploughed into the
line back at base and wiped out another F4U.
VMF-113
was activated on 1 January 1943 at Marine Corps Air Station El Toro as part of
Marine Base Defense Air Group 41. They were shortly given their full complement
of 24 F4U Corsairs. On 26 March 1944, while escorting 4 B-25 bombers on a raid
over Ponape, they recorded their first enemy kills when they downed eight
Japanese aircraft. In April of that year, VMF-113 was tasked with providing air
support for the landings at Ujelang. Since the assault was unopposed
the squadron quickly returned to striking Japanese targets in the Marshall
Islands for the remainder of 1944.
Corsairs
were flown by the famous "Black Sheep" Squadron (VMF-214, led by
Marine Major Gregory "Pappy" Boyington) in an area of the Solomon
Islands called "The Slot". Boyington was credited with 22 kills in
F4Us (of 28 total, including six in an AVG P-40, though his score with the AVG has been disputed). Other
noted Corsair pilots of the period included VMF-124's Kenneth Walsh, James E.
Swett, and Archie Donohue, VMF-215's Robert M. Hanson and Don Aldrich, and VF-17's
Tommy Blackburn, Roger Hedrick, and Ira Kepford. Nightfighter versions equipped
Navy and Marine units afloat and ashore.
At
war's end, Corsairs were ashore on Okinawa, combating the kamikaze, and
also were flying from fleet and escort carriers. VMF-312, VMF-323, VMF-224, and
a handful of others met with success in the Battle of Okinawa.
Corsairs
also served well as fighter bombers in the Central Pacific and the Philippines.
By spring 1944, Marine pilots were beginning to exploit the type's considerable
capabilities in the close-support role during amphibious landings. Charles
Lindbergh flew Corsairs with the Marines as a civilian technical advisor for United
Aircraft Corporation in order to determine how best to increase the Corsair's
payload and range in the attack role and to help evaluate future viability of
single- versus twin-engine fighter design for Vought. Lindbergh managed to get
the F4U into the air with 4,000 pounds (1,800 kg) of bombs, with a 2,000
pounds (910 kg) bomb on the centerline and a 1,000 pounds (450 kg)
bomb under each wing. In the course of such experiments, he performed strikes
on Japanese positions during the battle for the Marshall Islands.
By
the beginning of 1945, the Corsair was a full-blown "mudfighter",
performing strikes with high-explosive bombs, napalm tanks, and HVARs. She
proved surprisingly versatile, able to operate everything from Bat glide bombs (without
sacrificing a load of 2.75 in/70 mm rockets) to 11.75 in
(300 mm) Tiny Tim rockets. The aircraft was a prominent participant in the
fighting for the Palaus, Iwo Jima and Okinawa.
Statistics
compiled at the end of the war indicate that the F4U and FG flew 64,051
operational sorties for the U.S. Marines and U.S. Navy through the conflict
(44% of total fighter sorties), with only 9,581 sorties (15%) flown from
carrier decks. F4U and FG
pilots claimed 2,140 air combat victories against 189 losses to enemy aircraft,
for an overall kill ratio of over 11:1. The aircraft performed well against the
best Japanese opponents with a 12:1 kill ratio against Mitsubishi A6M and 6:1
against the Nakajima Ki-84, Kawanishi N1K-J and Mitsubishi J2M combined during
the last year of the war. The Corsair bore the brunt of fighter-bomber
missions, delivering 15,621 tons (14,171 tonnes) of bombs during the
war (70% of total bombs dropped by fighters during the war).
Corsair
losses in World War II were as follows:
- By combat: 189
- By enemy anti-aircraft artillery: 349
- Accidents during combat missions: 230
- Accidents during non-combat flights: 692
- Destroyed aboard ships or on the ground: 164
One
particularly interesting kill was scored by a Marine Lieutenant R. R. Klingman
of VMF-312 Checkerboards, over Okinawa. Klingman was in pursuit of a Kawasaki
Ki-45 Toryu ("Nick") twin engine fighter at extremely high
altitude when his guns jammed due to the gun lubrication thickening from the
extreme cold. He simply flew up and chopped off the Ki-45's tail with the big
propeller of the Corsair. Despite missing five inches (127 mm) off the end
of his propeller blades, he managed to land safely after this ramming attack.
He was awarded the Navy Cross.
The
Japanese Navy captured two Corsairs from an unknown Allied unit for evaluations
fairly late in the war; one of examples originally marked YoD-150 was remarked
with Yokosuka Ku air testing signs ED-150, but they never flew them.
