republic p-47 thunderbolttomswarbirds.com/.../republic_p-47_thunderbolt.pdf · 2018. 3. 11. ·...

Republic P-47 Thunderbolt

http://www.aviation-history.com/republic/p47.html[03/10/2018 20:39:16]


Built in greater quantities than any other US fighter, the P-47 was the heaviest single-engineWWII fighter to go into production and the first piston-powered fighter to exceed 500 mph. TheThunderbolt performed 546,000 combat sorties between March of 1943 and August 1945 and isconsidered the real forerunner of today's multirole fighters.

The Republic P-47 was the successor of a line of airplanes derived from the Seversky P-35,the XP-41, P-43 Lancer and XP-44 Rocket. The P-47 design team headed by AlexanderKartveli, Republic Aircraft Corporation's chief engineer, originally presented a design that wasto be powered by a 1,150 hp Allison V-1710-39 engine with an armament of only two 0.50caliber inch machine guns.1 A contract was awarded by the USAAC in November 1939, and foran even lighter XP-47A, but as intelligence was coming back from the war in Europe, it wasbecoming apparent that the performance goals of the XP-47 program were already inadequate.The USAAC issued new requirements which included:

• Airspeed of 400 mph at 25,000 feet.• Armament of six .50 caliber machine guns, preferably eight.• Armor plating to protect the pilot.• Self-sealing fuel tanks.• A minimum of 315 gallons of fuel.

The USAAC notified Kartveli that the XP-47A and the XP-44 Rocket contracts werecanceled since the P-43/XP-44 airframe was too small to meet the new requirements. (The XP-44 Rocket was based on the P-43 Lancer airframe with a radial engine and never made it past the mock-up stage.) Kartveli then quickly prepared a rough sketch of a new XP-47B prototype, but it was a daring concept. He planned to use the new 2,000 hp Pratt & Whitney XR-2800-21, eighteen cylinder radial engine which was the largest and most powerful aircraft engine ever developed in the United States (up to that time).2 The new design would incorporate eight 0.50 caliber machine guns, additional ammunition, increased fuel capacity and armor protection for the pilot. (The final fuel load was slightly under the capacity required, but this was overlooked as the aircraft met performance specifications.) Additionally, the airplane would include an efficient super-charging duct system that would

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offer the least interrupted airflow. Kartveli therefore adopted the unorthodox method ofdesigning this feature first and then building the fuselage around it. Despite the fact that thesupercharger was in the tail and the engine was in the nose, the arrangement worked quitewell—providing a system that was durable and less susceptible to battle damage.

The large P-47 Thunderbolt turbo-supercharger was stowed internally in the rear fuselage, with a large air intake duct mounted underthe engine, together with the engine oil coolers. Exhaust gases were piped back separately to the turbine and expelled through the turbineexhaust duct in the bottom of the fuselage. Ducted air is then fed to the centrifugal impeller and returned via an intercooler to the engine

under pressure. The principle behind a supercharger is that the exhaust gas is directed to a turbine that has a shared axle with acentrifugal impeller. Outside air is directed through the compressor and delivered to the engine intake. This allows the engine to deliver

more power as the airplane gains altitude in the thinner air of the upper atmosphere.

All these features were costly in weight and the airplane would have a take-off weight of11,600 lb. (5,262 kg) which was more than twice the weight of its contemporaries such as theSupermarine Spitfire, the Hawker Hurricane, the Messerschmitt Bf 109, the Curtiss P-40 andMitsubishi A6M Zero. Despite the monstrous size of the P-47, it would turn out to be one ofthe best three USAAF fighters of the war—the other two being the North American P-51Mustang and the Lockheed P-38 Lightning.

A contract was awarded on September 6, 19403 for the new XP-47B prototype and themaiden flight was only eight months later on May 6, 1941.4 The new plane dwarfed its pilotsand all previous fighters, but it still proved to be an outstanding success. It was able to doeverything Kartveli had hoped, and achieved a greater than expected speed of 412 mph (663kph).5 Numerous problems were encountered during development, such as excessive controlloads at high altitude and the canopy could not be opened at altitudes above 30,000 ft.Corrections included: balance panels to reduce rudder loads; blunt nose ailerons; ajettisonable sliding canopy to replace the hinged cockpit door; and all-metal flight controls toreplace the fabric covered controls used on the prototype.6 (It was found during testing thatthe fabric flight controls would balloon out due to changes in atmospheric pressure.) The XP-47B crashed on August 8, 1942, but not before many problems had been solved.7 Despite thecrash, an initial order was placed by the USAAC for 171 P-47Bs and 602 P-47Cs.8

One of the outstanding features of the P-47 was its remarkable acceleration when theaircraft was put into a dive. Any plane that attempted to break off contact by going into adive would soon be overcome by the remarkable speed of the P-47. Once the P-47 caught up

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to its prey, one burst from its eight 0.50 machine guns would obliterate anything it got a beadon.

To illustrate the rapidity of the increase in airspeed of the P-47 in a high speed dive, anevent occurred during testing on November 13, 1942 by Lieutenant Harold Comstock andRoger Dyar of the 63rd Fighter Group who were performing a test level run at 30,000 feet atover 400 mph. After the first run, they put their P-47Cs into a dive to go to the next level fortesting and during the dive, the airplane's speed increased very rapidly. Within seconds theirairspeed indicated the equivalent of 725 mph.9 As velocity increased, they experiencedextreme buffeting as they were approaching the realm of compressibility. Fortunately, theywere able to recover, unlike others who experienced the same phenomena, and began diverecovery at too low an altitude to experience what is euphemistically called "uncontrolledflight into terrain."

At this altitude, this airspeed would put them beyond the speed of sound, but this wouldonly be indicated airspeed since the terminal velocity of the P-47 is 600 mph,10 and theairspeed indicator was a straight pitot-static system with no air data computer for altitude andtemperature correction. Also one would have to wonder how this airspeed was calculatedsince the early P-47 airspeed indicators only went up to 500 mph. To clarify this, the airspeedindicated was the equivalent of 725 mph, so the indicated airspeed would be calculated byengineering on the ground. Since this phenomena was not unique only to the P-47, latermodel airspeed indicators showed airspeeds up to 700 mph.

The conventional three-bladed propeller could not efficiently utilize the power of the newengine, and a four-bladed propeller was adopted. Although this propeller was an admirablesolution to the power gearing of the engine, the problem remained of providing sufficientground clearance for its 12-foot (3.66 m) diameter. If a conventional undercarriage were tobe employed, its suspension would have been too far outboard to permit the wing installationof the guns and ammunition requested by the USAAF. Therefore, Kartveli had to design atelescopic landing gear which was nine inches shorter retracted, than when extended.Numerous other problems were to be faced in absorbing the loads and stresses which wouldbe imposed when a battery of eight 0.50 caliber guns, (a phenomenal heavy armament forthat time) were fired simultaneously, and in providing the necessary tankage for thequantities of fuel stipulated to make the machine the first true single-engined strategicfighter.

The P-47D-15-RE Thunderbolt on top, was the first version to have underwing pylons to usedroppable fuel tanks. Below is a P-47D-1 with white bands on the nose and tail to distinguish

it from the Focke-Wulf Fw 190A.

The P-47B entered USAAF service in November 1942, becoming officially operationalwith the Eighth Air Force stationed in the UK on April 8, 1943. However, the P-47B's rangewas not adequate for escort duties and its maneuverability at low and medium altitude waspoor. Since it was almost twice as heavy as its opponents, it exhibited a poor rate of climb,but had other advantages that more than compensated where it was lacking. In spite of itsearly shortcomings, the P-47 at least showed promise as a measure of real protection forAllied bombers which had previously suffered very heavy losses.

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In January 1943, when the USAAF's 56th Fighter Group arrived in the United Kingdomwith its massive Republic P-47 Thunderbolts, RAF Spitfire fighter pilots banteringlysuggested that their American colleagues would be able to take evasive action, when attackedby undoing their harnesses and dodging about the fuselages of their huge mounts. Althoughthe Thunderbolt was certainly big, making it the largest and heaviest WWII single enginedsingle-seat fighter ever built, its sheer size was not to prove detrimental to the Thunderbolt'ssubsequent operational career.

The first tasks of the Thunderbolt were high-altitude escort duties and fighter sweeps inwhich the new aircraft acquitted itself well, despite the inexperience of its pilots. It was soondiscovered that the heavy Thunderbolt could out-dive any Luftwaffe fighter, or for thatmatter, any Allied fighter. This provided a decisive method of breaking off combat whennecessary, but at low and medium altitudes it could not match the rate of climb ormaneuverability of German fighters. It's one main shortcoming was that of insufficient rangeto permit deep penetration into Germany, but means were already being sought to add to theP-47B's 305 US gallons of internal fuel.

At the time of the Thunderbolt's European debut, radial-engined single-seat fighters were ararity, the only other such fighter operational in Europe being the Focke-Wulf Fw 190A. Toprevent confusion between the two fighters of the opposing sides, the engine cowlings of theThunderbolts were painted white and white bands were painted around the vertical andhorizontal tail surfaces—an appropriate comment on recognition standards appertaining atthat time, as it would seem impossible to mistake the sleek and beautifully-contouredGerman fighter for the portly Thunderbolt. However, mistakes in aircraft recognition werecommon while making split-second decisions in the frantic pace of combat.

By mid-1943, improved P-47Cs were becoming available with external fuel tanks toincrease range and a longer fuselage to improve maneuverability. The P-47D was the majorproduction version of which 12,602 were produced. Early P-47Ds looked very much similarto the P-47C, but there were 21 variants of this model. 354 P-47Gs were built by Curtiss inBuffalo and 130 P-47Ms were built with a 2,500 hp engine giving a maximum speed of 473mph (761 km/h). The P-47M version was used for anti V1 Flying Bomb duties.

The final model, the P-47N, had extended wings and an additional 100 US gallons of fuel.It was developed too late to see much action in Europe and was primarily used in the Pacifictheater. The fastest model was the XP-47J, which did not go into production. On August 4,1944, this plane reached a level speed of 504 mph. Production plans were shelved in favor ofanother P-47 development, the Republic XP-72.

P-47s flew more than 546,000 combat sorties between March 1943 and August 1945,destroying 11,874 enemy aircraft, some 9,000 locomotives and about 6,000 armored vehiclesand tanks. Only 0.7 per cent of the fighters of this type dispatched against the enemy were

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lost in combat. As a testament to the survivability of the P-47, it should be noted that the topten aces who flew the P-47 returned home safely. Before the war was over, a total of 15,579Thunderbolts were built, about two-thirds of which reached operational squadrons overseas.

The final version, the P-47N, was built primarily for use against the Japanese in the Pacifictheater. Shown is a XP-47N fitted with a bubble canopy.

One Pilot's Initial Reaction To The P-47 Introduction

One day in January 1943, General Hunter, the Commander of the 8th Fighter Command,came to visit us at Debden. He said he had a surprise for us. We were soon to re-equip withthe very latest American fighter, the P-47 Thunderbolt. As he spoke we heard an unusualengine noise outside and one of the new fighters landed and taxied up beside one of ourSpitfires. We went outside to look it over. It was huge—the wing tip of the P-47 came higherthan the cockpit of the Spitfire. When we strapped into a Spitfire we felt snug and part of theaircraft—the Thunderbolt cockpit, on the other hand, was so large that we felt if we slippedoff the goddamned seat we would break a leg! We were horrified at the thought of going towar in such a machine: we had enough trouble with the Focke-Wulf 190's in our nimbleSpitfire Vs—now this lumbering seven-ton monster seemed infinitely worse, a true airinferiority fighter. Initial mock dog-fights between Thunderbolts and Spitfires seemed toconfirm these feelings—we lost four Thunderbolt pilots in rapid succession, spinning in fromlow level, while trying to match Spitfires in turns. In the end our headquarters issued an orderbanning mock dog fighting in Thunderbolts below 8,000 feet.

Gradually, we learned how to fight in the Thunderbolt. At high altitude, she was a hot shipand very fast in the dive; the technique was not to mix it with the enemy, but to pounce onhim from above, make one quick pass and get back up to altitude; if anyone tried to escapefrom a Thunderbolt by diving, we had him cold. Even more important, at last we had afighter with the range to penetrate deeply into enemy territory—where the action was. So,reluctantly, we had to give up our beautiful little Spitfires and convert to the newjuggernauts. The war was moving on and we had to move with it.

The change to the Thunderbolt might have been necessary militarily, but my heartremained with the Spitfire. Even now, thirty years after I flew them on operations, the meresound or sight of a Spitfire brings me a deep feeling of nostalgia and many pleasantmemories. She was such a gentle little airplane, without a trace of viciousness. She was adream to handle in the air. I feel genuinely sorry for the modern fighter pilot who has neverhad the chance to get his hands on a Spitfire—he will never know what real flying was like.

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Specifications:P-47B P-47C P-47D P-47N

Dimensions:Wing span: 40 ft. 9.75 in. (12.44 m.) 40 ft. 9.75 in. (12.44 m.) 40 ft. 9.75 in. (12.44 m.) 42 ft. 7 in. (12.97 m.)

Length: 35 ft. 3.25 in. (10.74 m.) 36 ft. 1.75 in. (11.02 m.) 36 ft. 1.75 in. (11.02 m.) 36 ft. 1. in. (10.99 m.)Height: 12 ft. 8 in. (3.86 m.) 14 ft. 1.75 in. (4.31 m.) 14 ft. 7 in. (4.44 m.) 14 ft. 8 in. (4.47 m.)

Wing Area: 300 sq. ft. (27.87 sq. m.) 300 sq. ft. (27.87 sq. m.) 300 sq. ft. (27.87 sq. m.) 322 sq. ft. (29.91 sq. m.)Weights:

Empty: 9,346 lb. (4,239 kg.) 9,900 lb. (4,491 kg.) 10,000 lb. (4,536 kg.) 11,000 lb. (4,990 kg.)Gross: 12,245 lb. (5,554 kg.) 12,500 lb. (5,670 kg.) 14,500 lb. (6,577 kg.) 16,300 lb. (7,394 kg.)

Max. T/O: 13,360 lb. (6,060 kg.) 14,925 lb. (6,770 kg.) 19,400 lb. (8,800 kg.) 20,700 lb. (9,390 kg.)Performance and Equipment:

Max. Speed: 429 mph (690 km/h) @ 27,800 ft. 8,473 m.433 mph (697 km/h) @

30,000 ft. 9,144 m.428 mph (689 km/h) @

30,000 ft. 9,144 m.467 mph (752 km/h) @

32,500 ft. 9,906 m.Service Ceiling: 42,000 ft. (12,810 m.) 42,000 ft. (12,810 m.) 42,000 ft. (12,810 m.) 43,000 ft. (13,106 m.)

Range: 550 miles (885 km.) 640 miles (1,030 km.) 475 miles (764 km.) 800 miles (1,287 km.)Max. Range: 1,100 miles (1,770 km.) 1,250 miles (2,012 km.) 1,700 miles (2,736 km.) 2,200 miles (3,541 km.)

Powerplant:Pratt & Whitney

2,000 hp, turbo-supercharged R-2800-21.

Pratt & Whitney 2,000 hp, turbo-supercharged

R-2800-21.

Pratt & Whitney 2,000 hp, turbo-supercharged

R-2800-63.

Pratt & Whitney 2,800 hp, water injected

turbo-supercharged R-2800-57/ -73/-77.

Armament: Eight, wing mounted 0.50 in. machine guns.Eight, wing mounted

0.50 in. machine guns. One 500 lb bomb.

Six or eight, wing mounted 0.50 in. machine guns.

2,500 lb bombs or ten 5 in. rockets.

Eight, wing mounted 0.50 in. machine guns.

3,000 lb (1,360 kg) bombs or ten 5 in. rockets.

Endnotes:1. David Mondey. The Concise Guide to American Aircraft of World War II. New York: Smithmark Publishers, 1996. 216. 2. Enzo Angelucci and Peter Bowers. The American Fighter. Sparkford, Nr. Yeovil Somerset, 1987. 390. 3. David Mondey. 216.4. Enzo Angelluci and Peter Bowers. 390.5. William Green. Famous Fighters of the Second World War. New York: Doubleday and Company, Inc., 1967. 84.6. Ibid. 85.7. David Mondey. 217.8. Lloyd S. Jones. US Fighters. Fallbrook, CA: Aero Publishers., 1975. 115.9. Howard Mingos, ed. The Aircraft Year Book for 1943. New York: Aeronautical Chamber of Commerce, 1943. 273. 10. Roger A. Freeman. Thunderbolt. A documentary History of the P-47. Osceola, Wisconsin: Motorbooks International, 1992. 25.

© Larry Dwyer. The Aviation History Online Museum. All rights reserved. Created September 20, 1997. Updated October 7, 2014.

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