On May 6, 1941, Lowry Brabham piloted the first XP-47B flight. Largest single-engine fighter then built, it was the first with a four-bladed Curtiss propeller, and had pilot armor, leakproof tanks, and a low cockpit entered from the port side by a door. The XP-47B did achieve 412 mph at 25,800 feet, where l,960 hp was available from the XR-2800-17. Eight .50-caliber guns in the wings were the strongest armament of any single-seater ordered into production. Combining the greatest horsepower with the heaviest firepower, more Thunderbolts would be built than any other American fighter.
When the first of 169 P-47Bs was accepted on December 21, 1941, it had the cockpit door, as did the second, but a sliding canopy was used on the remaining production aircraft. Four more were accepted in March 1942, but failure of the tail section during a fatal dive of the 5th P-47B on March 26, and also on the 6th example on May 1, delayed further acceptances. Deliveries resumed May 26 after the fabric-covered elevators were replaced with metal-covered control surfaces.
These Republic Thunderbolts were broken in by the 56th Fighter Group, that unit being nearest to the Farmingdale, New York, factory. Tests and operational training went slowly, accompanied by the loss of 13 pilots and 41 aircraft. Completion of P-47B production in September enabled the formation of the 348th and 355th Groups shortly thereafter.
The first P-47C was delivered September 14, 1942, with a new radio and vertical mast. After 57 P-47Cs, the
P-47C-1 introduced an extended engine mount that added ten inches to the length. Later block numbers were used to denote mechanical changes in the C and parallel D models. By February 1943, 602 P-47C, C-1, -2, and -5 models had been delivered from Farmingdale.
The Air Force chose the P-47 as its main fighter and expanded production with new contracts adding 850 P-47Ds to Farmingdale’s schedule on October 14, 1941, 1,050 P-47Ds ordered January 31, 1942, from a new Republic facility in Evansville, Indiana, as well as 354
P-47Gs to be built by Curtiss in Buffalo along with the P-40. Evansville and Buffalo flew the first P-47D and P-47G in September 1942. The first four P-47Ds and first 20
P-47Gs at Curtiss were similar to the concurrent P-47C, while 110 more P-47D-RA followed the P-47C-5 pattern.
Additional cowl flaps and mechanical refinements distinguished the P-47D-l-RE of February 1943, as well as the P-47D-2-RA and P-47G-1-CU models, whose suffixes denoted the Republic Farmingdale, Evansville, and the Curtiss plants, respectively. The eight wing guns had 267 to 425 rounds each and 135 pounds of armor protected the pilot. Curtiss completed its contract in March 1944, with the P-47Gs used only for training, but production that month from Republic reached 641 Thunderbolts.
Early Thunderbolts used the R-2800-21 and C-1 turbosupercharger with an automatic regulator (lacking in P-43s),
but water injection kits for emergency power boost were added, beginning with P-47D-3-RA and P-47D-5-RE. This increased output from 2,000 to 2,300 hp and top speed from 411 to 428 mph at 25,500 feet at design weight.
The 200-gallon flush ferry tank provisions on the P-47C series were replaced by shackles for a 75 or 110-gallon belly drop tank, or a 1,000-pound bomb on the P-47D-4-RA and P-47D-5-RE. The P-47D-10-RE series had R-2800-63 engines that raised the critical altitude to 29,000 feet, where top speed was 440 mph in light condition. By that time, however, Thunderbolts had to operate with all the fuel they could carry, so they could protect American bombers deep into enemy airspace. Drop tanks under the wings were added to the P-47D-15-RA and P-47D-16-RE.
Pratt & Whitney R-2800-59 power plants were standardized on the P-47D-21 and all later D models. Larger, 13'2" Hamilton propellers were introduced on the P-47D-22-RE while the P-47D-23-RA got 13-foot Curtiss propellers. These were the first Thunderbolts delivered in natural metal finish, without camouflage. Armament included eight .50-caliber guns with 2,136 rounds, and under wing racks for two 1,000-pound bombs or 165-gallon tanks.
Thunderbolts enter Combat
First priority for Thunderbolts was given the Eighth Air Force, whose bombers had the most important role in the air offensive against Germany and badly needed strong fighter support. When P-47C-2 and C-5s began arriving in Britain late in 1942 they were issued to three fighter groups: the veteran 4th, who reluctantly gave up their Spitfires; the 56th, fresh from flying P-47Bs in America; and the 78th, whose previous experience had been with P-38s.
Engine and radio problems caused delays, but on April 15, 1943, the first Thunderbolt kill was made by a 4th Group leader. As compared to the enemy Fw 190, the Thunderbolts were faster over 15,000 feet, had a higher ceiling and massive firepower, but their weaknesses were slow climb at low levels, and too wide a turn radius. Combat experience soon taught the American pilots the tactics to maximize their plane’s advantages. Another Thunderbolt virtue was its sturdy construction.
The greatest problem was that of increasing the radius of action needed to support the bombers. The 200-gallon flush ferry tank provided for early C and D models was unsuitable for combat, and sufficient 75-gallon drop tanks were not available. The British were able to produce a 108-gallon tank of paper composition: one under the belly extended the P-47D’s combat radius to 350 miles, and was first used on a July 28, 1943, mission. Two under the wings allowed a 445-mile radius, or two 165-gallon tanks could be attached for ferry flights.
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