The F4U-1D in World War II

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Development

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While the F4U-1A greatly improved the Corsair's capabilities as a fighter, Vought continued the process of updating and improving the design. As the war progressed the fast carrier task forces began to proceed with the "Island Hopping" strategy, and the steadily decreasing quality and quantity of opposition in the air led the needs of the Navy to shift towards destroying the enemy on the ground. Close Air Support had also been of great importance to the Marines throughout the war as they advanced on the tenacious and well-entrenched Japanese army, and these needs would define the next step forward in the evolution of the Corsair.

 

Of the numerous changes implemented in what would be designated the F4U-1D, the most evident was a substantial increase in firepower. The aircraft's ordinance loadout was upgraded by deleting the centerline rack and the addition of pylons to the anhedral portion of the wings for loads of up to one 1000lb bomb each or a 150gal drop tank, and the inclusion of tabs on the wings for eight 5" HVAR rockets (four on each side). The outer pair of machine guns were also increased to 400 rds per gun, compared to 375 in the 1 and 1A, for a total of 2400 rds for the Brownings. Towards the end of the war the centerline bomb rack was re-added and strengthened, allowing the aircraft to carry up to a 2000 lb bomb in this position or another drop tank. The F4U-1D could also carry two of the massive 11.75" "Tiny Tim" rockets on the main pylons. Depending on configuration, the Corsair could carry up to 4000 lbs of bombs in addition to rockets, however such a configuration was too heavy for carrier operations, and was generally only used when the aircraft was operating from land bases.

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This overwhelming firepower made the F4U-1D the Navy and Marine Corps' primary ground attack aircraft from the end of 1944 through the end of the war. Her armament was almost on par with that of the Navy's SB2C Helldiver and TBM Avenger, with the performance to handle enemy fighters. As with earlier models, the 1D's landing gear possessed a dive brake setting, which could be used to control the fighter's airspeed during attack dives. The Corsair's durability also greatly contributed to her success in the attack role.

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The F4U-1D made further improvements in addition to the increased ground-attack capability. Early 1Ds retained the partially-framed canopy of the 1A, however this was quickly replaced with a bubble canopy that eliminated these frames entirely. Most 1Ds retained the metal "hood" above the pilot's head but this was also eventually omitted in later 1Ds. Additional controls on top of the dash were added for the handling of the aircraft's ordinance. Some of the fabric covering on the underside of the wings was replaced by metal plate. The wing-mounted fuel tanks were eliminated entirely. She was slightly heavier than the 1A, and the main pylons on the anhedral of the wing inboard of the landing gear struts were permanently fixed, even when the aircraft was flying clean. As a result the 1D's top speed was reduced, but still exceeded 400 mph at altitude.

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Perhaps the most significant upgrades were to the oleo struts, which in the -1 and 1A were prone to collapse or bounce during the shock of carrier landings. The new struts eliminated these concerns entirely and, combined with landing procedures refined by the British Fleet Air Arm, for the first time the F4U was fully certified for operations from the decks of the big American fleet carriers.

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Unit Deployment

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Marine Corps squadrons in the Pacific began receiving the F4U-1D in late 1944, operating from land bases throughout the South and Central Pacific. Additionally, for the first time Corsairs began to be deployed aboard carriers with US Navy squadrons in numbers, supplementing the Hellcats, Helldivers and Avengers already in service aboard the flat tops. The 1D provided a superb ground attack platform with its heavy ordnance loadout, and still retained its capability to take on enemy aircraft.

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Marine squadrons to use the 1D included VMF-312; the famed Checkerboarders with their distinctive checkered cowls and tails, VMF-251; formerly an observation squadron flying F4F-3P and F4U-1As, VMF-323 Death Rattlers and VMF-224.

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One squadron of note to fly the F4U-1D was VMF-512, a unit undergoing special training with the massive "Tiny Tim" 11.75" rocket (essentially a 500lb naval shell with a rocket engine strapped to it). Their target was the German V-1 launch sites in Europe, intending to use the range of the Tiny Tims to stay clear of German anti-aircraft fire, and take advantage of its high destructive power to obliterate the sites. However General George C. Marshall, upon hearing the plan, would not listen any further once he learned the attack would be carried out by Marines, and is famously attributed with refusing to "allow Jarheads to fly in my war."

 

In addition to its ubiquitous use among the Marines, for the first time the Corsair began to deploy in large numbers among Navy squadrons. The most notable, perhaps, was VF-84 under Roger Hendrick. The squadron flew off USS Bunker Hill. Including Hendrick, much of the core of the squadron was made up of veterans of VF-17, however despite being spiritual successors to the Jolly Rogers, they were denied use of the name by the Navy. F4U-1Ds were also assigned to VBF-85 assigned to USS Shangri-La, VF-10 off USS Enterprise.

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The F4U-1D became the main Corsair variant fielded by the USN and USMC until the end of the war. She saw combat at most major engagements in the final year of combat, including Iwo Jima and Okinawa, and was used to strike ground targets and enemy shipping throughout the Pacific on the final drive towards Japan. Additionally, F4U-1Ds of VMF-224 flew in the last major dogfights of the war for the Marines, when eight Corsairs encountered estimates of up to 80 N1K2-J Shiden-kai of the elite 343rd Kokutai over Kyushu.