A unique fighter – Fleet Air Arm Corsair IV, ‘KD431’
Some aircraft are transformational and they take a giant technological leap into the future. Sometimes for whatever reason – be it political, technical – this doesn’t work out, as with the BAC TSR2. At other times, after a few stutter-steps, a world-beater emerges.
This is what happened with the new US Navy fighter, the Vought F4U, designed by Rex B. Beisel. From its first flight, on the 29th May, 1940, it started to raise eyebrows. Powered by the experimental Pratt & Whitney XR2800-4, 18 cylinder Double Wasp engine, putting out 1,800 hp, the prototype XF4U-1 became the first U.S. single-engined fighter to break the 400 mph barrier (405 mph, 1st October, 1940). At the time this was world class speed for any fighter, let alone a naval one, with its in-built weight penalty (due to being stressed for deck landings) and extra equipment, and the U.S. Navy was eager to get the newly-named Corsair onto their Fleet Carriers.
However, there were problems, which became more and more obvious as flight testing continued. The Corsair wing was unusual in that it was ‘cranked’, with a short section close to the fuselage being angled sharply downwards (anhedral), before assuming a dihedral, or upwards angle to give a ‘reverse gull wing’. This gave large advantages, in that the 90° angle the wing made with the aircraft’s fuselage reduced drag considerably, and the sharp angle which made the ‘kink’ allowed a shorter, stronger undercarriage leg, which would be required as the Hamilton Standard propeller which would absorb the Double Wasp’s awesome power was no less than 13 feet 6 inches in diameter.
It was this short undercarriage which caused such problems that the US Navy actually decided to let the Marines have the Corsairs and use them from land bases, initially. This was because the Corsair often bounced – badly – on hitting a carrier’s deck. Unfortunately, this meant that the arrestor hook bounced over the taut arrestor wires, and the aircraft skidded onwards into the ‘deck park’ of aircraft, spotted near the carrier’s bow, with disastrous results.
The other problem was one of aerodynamics. the long nose of the F4U demanded a curving, banked course when in the final phases of approach to the carrier deck. This sometimes caused the starboard wing to stall abruptly, and the aircraft would spin into the sea from a low level. Alternatively, if an attempt was made to suddenly apply full throttle to recover, the massive torque from the Double Wasp would flip the Corsair inverted with usually fatal results. However, a saviour was on the horizon in the form of the Royal Navy’s Fleet Air Arm.
At the start of WW2, the frontline fighters of the FAA include such anachronisms as the Gloster Gladiator biplane. This was due, in part, to the Royal Air Force having maintained control of the FAA until 29th May, 1939. Stopgap fighters such as the Fairey Fulmar and Sea Hurricane (see diary) were issued, but modern American fighters were needed – and fast. The Grumman Wildcat (initially named the Martlet) and Hellcat (RN name, Gannet) were acquired, but the Royal Navy were very willing to accept the Corsair. To fit their carrier hangars – which had lower headroom, due to the substantial armored decks the British ships had – a total of 16 inches was removed from the F4U’s wing. This had the effect of increasing the Corsair’s roll rate, and let it fit inside the RN’s hangars. The dreaded deck bounce was cured by a stroke of RN engineering brilliance. A variable rate bleed valve was fitted to the oleo leg of the undercarriage, which tamed the bounce (I worked with a former FAA Engineering Officer who served on the unit that devised this cure!) The stall characteristics were altered for the better by the installation of a small stall strip on the starboard wing leading edge.
The FAA’s Corsair squadrons were the first into action on 3rd April 1944, with Nos 1834 & 1836 Squadrons from the fleet carrier HMS Victorious providing ‘top cover’ to a strike by Fairey Barracudas on the German battleship ‘Tirpitz’ in Norwegian waters. Other squadrons were transferred to the British Pacific Fleet, where they joined US Navy Corsair units and Marine Squadrons in pounding the Japanese islands in the final phases of that enormous campaign.
Huge quantities of Corsairs flowed across the Atlantic, usually as deck cargo or on escort/ferry carriers, under terms of the Lend-Lease Act (Public Law 77–11, enacted March 11, 1941). Chance had to enlist the aid of other manufacturers, namely the Goodyear Aircraft Company (as their FG-1) and the Brewster Aeronautical Corporation (as their F3A-1). Brewster production was a disaster in quality terms, and the Navy forced the company to abandon their contract, but the Goodyear aircraft came to the Royal Navy in quantity.
Here we can see an example of a late production, Goodyear-built Corsair IV, in the Fleet Air Arm Museum, at Yeovilton. This is a unique Corsair, as I will show. One of the 2,012 Corsairs taken on charge by the RN, it had been built in July/August, 1944 by Goodyear as an FG-1D (equivalent to the F4U-1D) and delivered to the receiving depot at Renfrew in Scotland. Time was spent at a couple of Maintenance Units (one at Aldergrove, Northern Ireland) before delivery, as ‘KD431’ to its first squadron, No. 1835 at Eglinton, Northern Ireland – C.O., Lieutenant Commander (Air), T J A King-Joyce, RN – with the intent that this unit form part of the 17th Carrier Air Group, British Pacific Fleet. However, ‘KD431’ was passed on to No. 768 Squadron, FAA, where she was used on HMS Premier (ex-USS Estero, a Bouge Class escort carrier) in the Clyde estuary on Deck Landing Training Carrier duties. Next stop, post-war, was a transfer to HMS Peewit (a shore establishment in Angus, Scotland) which was a Deck Landing Control Officer Training School. ‘KD431’ made her last deck landing at sea on the 7th December 1945.
On the 3rd July, 1946, being surplus to requirements the Corsair was transferred to Cranfield College of Aeronautics, Cranfield, England, where it was used for technical training until 1963, when it was donated to the Fleet Air Arm Museum. When delivered it was repainted in a highly durable, but anachronistic polyurethane finish, and was put on display.
In 2000, David Morris, the Curator of the museum made a bold decision. The paint was to be carefully removed in a process akin to an art restoration, layer by layer, to see if the ‘new-built’ aircraft could be uncovered, as well as the wartime finish. The process, which was meticulously documented, and published (‘Corsair KD431 — The Timecapsule Fighter’, 2006) was a staggering undertaking. The original Goodyear test pilot was traced, as was the last FAA pilot, Peter Lovegrove. Original paper labels inside the fuselage, with handwritten notes, were discovered.
The aircraft, as you now see it, was finally ‘rolled out’ in August, 2005. It bears the squadron code ‘E2-M’ and is quite likely the most original WW2 naval fighter in existence, as almost all traces of its post-war paint and modifications have been removed. As such, it represents a unique window on the history of technology of the period.