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P-47 Thunderbolt: Aviation Darwinism

Chapter Eight:

As North American Aviation's superb P-51 Mustang began arriving in the ETO, it became obvious that its combination of high performance and range would soon make it the dominant USAAF fighter. There was no other fighter available that could truly compare. The P-38 had adequate range and combat performance, however, it was suffering from a host of serious technical bugs that would greatly erode confidence in the big twin engine fighter. The P-47 still reigned supreme at high altitude. Unfortunately, the P-47D models in service in late 1943 lacked the range to penetrate very far beyond the western border of Germany. It was within this context that the command of the VIII Air Force made the decision that the Mustang would be the primary long-range escort fighter. The P-38 and P-47 would be reassigned to the IX Air Force where they would be used with great effect in the role of tactical fighter-bomber. Other factors weighed in the P-51's favor. Its initial cost was considerably less than the Thunderbolt and nearly half that of the P-38. The logistical advantages were noteworthy as well. A twin engine fighter certainly requires additional manhours to keep the aircraft combat ready. Two engines also use considerably more fuel for flight over a given distance. The Mustang's Packard V-12 was more fuel efficient than the large and powerful Pratt & Whitney of the P-47. It seemed that the Mustang would remain at the top of the USAAF heap.


Thunderbolt, Lightning and Mustang
The Big Three of American fighters. Flying over Saipan in the tightest of formations are the fighters that devestated the Luftwaffe and the Air Forces of Imperial Japan. Within a few months the long ranging P-47N would join the P-38 and P-51 to wreak destruction on the Japanese over their home islands.


The adoption of the P-51D by the VIII Air Force and the transfer of most P-47s to the air to ground role was seen with foreboding by Republic. Combined with the Air Material Command's obsession with the Fisher (GM) XP-75 long range escort fighter, the sudden preeminence of the P-51 meant that there would be little reason for the USAAF to continue to purchase the Thunderbolt. The Mustang was a proven commodity, whereas the XP-75 would prove to be little more than a total failure. Nonetheless, the Air Material Command believed the hype coming out of Fisher and the War Production Board was persuaded by General Motors to order 2,500 of the P-75A (including 5 prototypes). These were never built once the USAAF realized that the XP-75 was totally unsuited in the role for which it was designed. Despite the wasted millions in much needed R&D dollars and the tragic misuse of skilled labor and factory space, the basic requirement still remained. The future need for adequate escorts for the B-29s expected to bomb mainland Japan would be the impetus for virtually all future fighter procurements. The latest models of the Thunderbolt, while possessing adequate range capabilities for the ETO, were not going to cut the mustard in the vast Pacific where a fighter would need a true combat radius of at least 1,000 miles. The latest P-47D-40-RA could not quite make that distance, engage in combat and have anything resembling a fuel reserve for the return trip.

Fortunately, Republic had been paying attention to developments with the P-51 and were hard at work on a long range Thunderbolt as early as November of 1943. The same P-47C-5-RE that had been used as development mule for the Pratt & Whitney R-2800 C series was fitted with 27 inch long extension inserts in each wing. This was done largely to test the handling of the aircraft. No provision was made to carry any additional fuel in the wings. These tests revealed that the roll rate had suffered and the wings were clipped at the tips and a squared off cap was fitted.


The unofficial XP-47M test mule
This is the only existing photo of the "unofficial" XP-47M test mule. After being used as a testbed for the Pratt & Whitney R-2800 C series engine, it was fitted with 27 inch long wing extensions (at the wing root), and used to test the flight characteristics of the modified wing. When the request for a long range Thunderbolt came along, this fighter was wheeled out, dusted off and presented to the Air Material Command. The photo shows the fighter prior to receiving the modified wing.

In May of 1944, an Expenditure Order was issued and $101,000 was allocated to Republic to develop a “wet” wing to be installed on one of the three YP-47M prototypes. Within 30 days Republic was able to present a test report based upon their earlier testing, along with a full set of drawings as a proposal to the Air Material Command. The new drawings illustrated the new wing design. The inserts were now just 18 inches in length, and contained an integral fuel tank for 100 gallons of fuel. In the contract, the #3 YP-47M was specified as the test aircraft (S/N 42-27387). Twenty hours of flight time were expected after the new wing had been installed. In July, the fighter was officially designated as the XP-47N and the unofficial test mule was re-designated as a P-47C-5-RE once again. The final disposition of the test mule is unknown. It did, however, retain its new wings and the more powerful C series engine for as long as the aircraft appeared on the company inventory.

The modifications to the existing YP-47M were considerable. Aside from simply installing the wing inserts and fuel tanks, the flaps were required to be redesigned, and the ailerons had to be modified to fit with the new squared-off wing tips. Due to spacing the wings out from the wing root, the landing gear track increased by more than 3 feet. The overall wing span had increased to just over 42 ft 6 inches. The empty weight of the fighter had gone up by nearly half a ton to 12,950 lbs.


The XP-47N
This wonderful view of the XP-47N shows its new wing planform to great effect. The squared-off wing tips makes P-47N indentification easy. Note that the Prototype fighter does not yet have the dorsal fillet installed.


The XP-47N took to the air for the first time on July 22, 1944. Test comparisons were made with a P-47D-30-RE throughout the early portion of the evaluation period. Much to everyone's surprise, the XP-47N, with its greater wingspan and higher weight actually proved to have better roll performance than the D model. At 250 mph TAS, the N attained a maximum roll rate just over 100 degrees/second. The P-47D-30-RE could manage but 85 degrees/second at the same speed. At higher speeds, the N widened the gap further. In mock combat with a P-47D-25-RE, the new fighter proved to be notably superior in every category of performance. In short, the XP-47 waxed the venerable D model regardless of who was piloting the older fighter. The new wing was part of this newfound dogfighting ability, however, the more powerful C series engine played a role too. The additional horsepower allowed the N to retain its energy better than the older Thunderbolt. Perhaps the greatest performance increase was in maximum speed. Though not as fast as the stunning P-47M, the heavier N was fully 40 mph faster than the P-47D-25-RE and could generate speeds 30 mph greater than its principal rival, the Mustang. Scorching along at 467 mph @ 32,000 ft., the N could not be caught by any fighter in regular service with any air force on earth with the single exception of its M model sibling. This combination of wing and engine had pushed the N model up to the top rank of the superlative prop driven fighters then in existence.


Republic's P-47N test pilots
Republic employed some of the nation's finest test pilots to test the XP and YP-47N prototypes. The pilots pictured here posing with a new N model, standing, from left to right; unknown mechanic, Ken Jernstedt, J. Croft, Frank Simpson, and Parker Dupouy. Kneeling are; Carl Bellinger, Peter Collins, Fillmore Gilmer and another unknown. Jernstedt and Dupouy were both veteran combat pilots with Chennault's famous American Volunteer Group (AVG), also known as the Flying Tigers.


The testing program included determining the maximum range of the fighter. This was done with various combinations of fuel loads and external drop tanks. Ultimately, a test flight was made from Farmingdale to Eglin Field in Florida. The XP-47N took off with two 315 gallon drop tanks hanging from the under-wing hardpoints. Usable fuel in these tanks totaled 600 gallons. Added to the internal fuel load, the N eased off the runway with 1,170 gallons of fuel (usable). At a gross weight of 20,166 lbs., the Thunderbolt headed south in company with a P-47D chase plane. Arriving off the coast, east of Elgin in 3 hours, 44 minutes, the external tanks were dropped. Another P-47D, already waiting at Elgin, took on the N in a mock dogfight that lasted for twenty minutes. The throttle was advanced to military power for 15 minutes of this time, with an additional five minutes in the War Emergency Power (WEP) detent. After these fun and games were concluded the N was turned around and flown back towards Farmingdale. Heavy weather over Long Island caused the plane to divert to Woodbine, New Jersey. Having flown 1,980 miles, total fuel usage was measured at 1,057.5 gallons. There was still more than 112 gallons of usable fuel remaining in the main fuselage tank, enough for another 330 miles @ 1,700 rpm in auto-lean. The XP-47N was now the king of long-range single engine fighters (the all time leader of long range escorts was the P-38L-1-LO, which could claim a combat radius of nearly 1,500 miles under ideal conditions).


P-47N runs up on le Shima, 1945
Lt. Robert Forrest performs his pre-takeoff run-up on the ramp at le Shima. This P-47N-2-RE is loaded with one 75 gallon drop tank and two 165 gallon P-38 drop tanks filled with Napalm. Forrest flew with the 463rd Fighter Squadron of the 507th Fighter Group.


Before the first production P-47N was built, that old bugga-boo of insufficient side plate area needed to be addressed. Lessons learned with the late models of the P-47D indicated that the dorsal fillet applied to those fighters did not provide quite the area required to fully offset the low speed rudder over-balance problem. The engineers at Republic designed a larger dorsal fillet and installed it on the XP-47N. This proved to do the trick, however, it was not an eye-appealing solution. Certainly, the approach taken by North American and Grumman was more attractive as well as functional. Then again, no one ever accused the Thunderbolt of being pretty.


P-47N-25-RE
This P-47N-25-RE would eventually find its way into the Cradle of Aviation Museum's collection. In this undated photo, the fighter appears in postwar livery. The ordnance under the wings is certainly deactivated for display. There even seems to be something akin to ETO invasion stripes on the bottom of the fuselage, just aft of the wing. This photo does illustrate the N model's unique dorsal fillet to good effect.


Eventually, 1,816 P-47Ns were completed before the cancellation of the contract after Japan surrendered. The big fighters were deployed to the Pacific and were beginning to demonstrate their full potential when two atomic bombs put an end to the conflict. After the war, most of the P-47Ns were allocated to Reserve and Air Guard units, where they served faithfully until they were replaced by jets in the mid 1950s.


P-47N-1-RE bore-sighting
Bore sighting the guns on any fighter was meticulous work. To obtain the best result, all the guns were sighted to focus on a specific point. Often, the pilot would specify that point. This P-47N-1-RE served with the 318th Fighter Group operating out of le Shima.


With the outbreak of war in Korea in 1950, the P-51D (now designated the F-51D), was rushed into the fray and did solid work as a fighter-bomber. However, hundreds of P-47s were in service stateside and were never called into service against the North Koreans or later, the communist Chinese. Certainly, there was no doubt that the P-47 was better suited for air to ground close support. It could carry a far greater load of ordnance and was considerably more resistant to ground fire and flak. So, why was the P-47 (F-47) not used? The Thunderbolt's Navy alter-ego, the F4U Corsair, was used to great effect, and like the P-47, was far more rugged than the Mustang with its fragile Prestone cooling system. To this day, no one has adequately addressed this question. When the chips were down and the U.N. forces were pinned in the Pusan perimeter, where were the Thunderbolts?


P-47N-25-RE of the Cradle of Aviation Museum
This the same P-47N-25-RE, S/N 44-89444, shown earlier. Here it has been stripped of its postwar markings and has had the cowling ring and rudder tip painted yellow. It was in this condition that the fighter was transferred to the Cradle of Aviation Museum.


The P-47 would go on to serve in nearly every Air Force in the free world. It left behind a legacy that can hardly be matched by its contemporaries. Sure, the P-51 is virtually worshiped by its masses of fans, but the Mustang could do nothing that the P-47, in its many guises, could not do or had already accomplished. Ultimately, more Thunderbolts were produced than any other American fighter in World War Two. The mighty Thunderbolt broke the back of the Luftwaffe and pounded the Wehrmacht without mercy. It proved to be too much for the Japanese to handle and was giving those same Japanese the identical working-over it had given the Germans. Then, it was suddenly no longer needed after the two atomic blasts that introduced the nuclear age to a world that to this day, lives under the threat of nearly instant mass destruction.


The Cradle of Aviation Museum's P-47N-25-RE being readied for display
In this photo, the Museum's P-47N has been painted in wartime livery and is standing by to be moved to the display hanger. Today, the fighter is polished to a high gloss and is one of the finest examples of the P-47 line to be found anywhere.


Looking back at World War Two, we can see that before the days of stealth technology and smart weapons, real pilots took real airplanes into harms way. They depended upon the rugged reliability of their simple aircraft and their skills as pilots to get the mission accomplished and live another day to fly again. If anyone should desire to see a true definition of durability and versatility in W.W.II airpower, they need not look any further than the remarkable Republic P-47 Thunderbolt.


The P-47 evolution: XP-47B through the P-47N


Afterward:

Special thanks is in order to my kind, generous friend and benefactor, Warren Bodie. Without Warren's wonderful research and terrific photos, this story would not have been possible. I can think of no one who can match Warren's knowledge of aviation and in particular, American WWII aviation. This story is as much a product of Warren's work as it is mine. In every sense of the meaning, Warren is the co-author of this story.

I would also like to offer my sincere thanks to Tom Gwynne and the staff of the Cradle of Aviation Museum. I was provided with generous access to materials and photos. The folks at CAM are deserving of much credit for their dedication to preserving the aviation heritage of this nation and specifically, that of Long Island, the true cradle of American aviation.


Corey C. JordanWarren M. Bodie


Bibliography:

Bodie, Warren M., “Republic's P-47 Thunderbolt: Seversky to Victory.”
Bodie, Warren M., “The Lockheed P-38 Lightning.”
Boyne, Walter, “Clash of Wings: WWII in the Air.”
Dean, Francis, “America's Hundred Thousand: U.S. Production Fighters of WWII.”
Ferguson & Pascalis, “Protect and Avenge: The 49th Fighter Group in WWII.”
Freeman, Roger, “Thunderbolt, A History of the Republic P-47.”
Freeman, Roger, “The Mighty Eighth.”
Hammel, Eric, “Air War Europa.”
Johnson, Robert, “Thunderbolt!”
Scutts, Jerry, “P-47 Thunderbolt Aces of the 8th Air Force.”



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