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P-47 Thunderbolt: Aviation Darwinism

Chapter Seven:

As 1944 dawned over the European Theater of Operations, major changes were about to be made in the leadership and tactics of the American Air Forces. General Tooey Spaatz would serve under Eisenhower commanding the USSAFE. On January 6, Gen. Jimmy Doolittle formally relieved Ira Eaker as commander of the 8th Air Force. Doolittle allowed Gen. William Kepner to turn the 8ths escort fighters loose to hunt down and destroy the Luftwaffe wherever they could be found. This is worth noting, because no other order did more to eliminate the Luftwaffe as a viable threat than this. The introduction of "phased-escort" tactics did much to reduce the work load on the still too few long legged escorts such as the P-38 Lightnings and the P-51 Mustangs. Flight routing of the fighter escorts was planned to maximize endurance and allowed the shorter ranging P-47s to fly deeper into enemy territory. Such routing also permitted the long range escorts to remain longer over the target area. More importantly, phased-escort allowed fighter groups to be relieved, which in turn allowed them to head down to the deck and attack Luftwaffe airfields. It was not uncommon for large groups of Mustangs to attack anything and everything in sight from the heart of Germany all the way back to the coast of France. Suddenly, no German airfield was safe from ambush. No Luftwaffe pilot could feel safe in the air or even on the ground. No railroad or autobahn was safe from swift and unexpected assault from the sky.

Beginning in hours of darkness on February 19-20, the 8th and 9th Air Forces along with the RAF began operation Argument. Also known as Big Week, this Allied air assault began with a heavy raid by the RAF on Leipzig. Before the fires were even brought under control, heavy bombers of the 8th pounded Leipzig again, along with Gotha and Brunswick. In theory, these attacks were aimed at Germany's war production plants and factories. In reality, these missions were primarily designed to draw the Luftwaffe into combat with the goal of grinding down their pilot manpower. Argument was successful in inflicting severe losses to the Luftwaffe's trained pilot corps. Ironically, actual German fighter production was increasing. Nonetheless, planes without pilots are still quite useless.

The pressure was kept up through March into April. Luftwaffe pilot losses were becoming critical. All the while, the emphasis was beginning to shift towards the destruction of German transportation assets in preparation for the expected invasion of France. The 9th Air Force was pounding coastal defenses from Calais to Cherbourg. Bridges and marshalling yards were being hammered on a daily basis by medium bombers. With each day it was becoming more difficult to move equipment from point to point in France. Simply driving down a roadway presented a high risk of being strafed by roaming Allied fighters.

Things were growing more desperate for the Luftwaffe in France. Allied bombers and fighters were also concentrating on putting every German aerodrome within range of Caen out of action. The Luftwaffe was forced to disburse aircraft away from airfields, even positioning fighters to use highways as runways. Things were rapidly becoming untenable for the German Air Force. By mid May of 1944, the Luftwaffe had ceased to be a factor over France. The Allies now had complete and unchallenged air superiority over the whole of western Europe, with total air supremacy over France.

Top 9th Air Force ace Glenn Eagleston
Many of the 9th Air Force pilots became celebrated aces despite being generally assigned to tactical ground attack missions. Maj. Glenn Eagleston of the 354th Fighter Group ran up the highest score in the 9th. With no less than 18.5 confirmed victories, it is reasonable to speculate how high his total may have been had he flown with the 8th Air Force instead. Here Eagleston taxis in from a mission with the aid of a ground crewman giving taxi directions. It not possible to see over the Thunderbolts long nose while on the ground. Without a taxi director on the wing, the fighter would have to be taxied by zig-zagging from side to side while peering out of the front quarters of the canopy. This is a P-47D-30-RE. The photo was taken in December of 1944. Note that the invasion stripes applied in June have not yet been removed.

Adding to the already cascading woes of the German war machine was the effort being mounted to destroy Germany's ability to produce aviation and motor vehicle fuel. Refineries and storage facilities were getting worked over by the heavy bombers of the 8th and 15th Air Forces. One sure-fire method of keeping the Luftwaffe on the ground everywhere was to eliminate its sources of fuel. At long last, fuel had become a high priority target for the Allied bombers.

Along with the medium bombers of the 9th Air Force, the P-47, P-51 and P-38 were now being used with great effect in the role of tactical fighter-bomber. Of the three fighter types, the P-47 would prove to be the most widely used in this role and the big Thunderbolt would rival the RAF's Hawker Typhoon for the title of best air to ground fighter in the ETO. Many (including this writer) have since concluded that the Thunderbolt was superior to the Typhoon due to the greater resistance of its radial engine to battle damage. The big R-2800 did not have a liquid cooling system that could easily be punctured by enemy ground fire as did the Typhoon. Moreover, the Hawker fighter was powered by the infamously unreliable Napier Sabre H-24 engine. The Pratt & Whitney engine was by contrast, utterly dependable.

63rd FS of the 56th FG
Here we see a portion of the 63rd Fighter Squadron (56th FG) flying in formation. In this group of P-47s we can see several different sub-models. These include several P-47D-25-RE and at least one P-47D-28-RE. The single "razor back" in the trailing section is probably a P-47D-23-RA. This photo was likely taken in July of 1944.

With the invasion of France (Operation Overlord) on June 6, 1944, the primary mission of Allied Air Forces was now focused on supporting the Allied army forces in Normandy. The Luftwaffe was all but eliminated from the equation. Only two German fighters had been able to reach the beaches on D-Day. 26 other German fighters and bombers were destroyed attempting to reach the landing area. None even got within sight of the beaches.

The Thunderbolt had already displayed its ability to use its eight .50 caliber machine guns very effectively against ground targets. Now, it would be employed as a fighter-bomber, delivering up to 2,000 lbs of bombs and rockets with great efficiency and accuracy against a wide range of German targets.

P-47D belly landing
This Thunderbolt suffered disabling engine damage from ground fire in April of 1945. The pilot elected to execute a wheels up landing in a soft field. Damage to the fighter is minimal and it would be repaired and back in service in very short order. Certainly, such a spectacular landing will draw a crowd of onlookers. In this case American GIs swarm around the Thunderbolt to get a close look at what they had seen pounding the Germans all across western Europe.

Most missions were flown with a specific target designated. However, increasingly, the P-47s were being used to attack targets of opportunity. No German vehicle dared move in daylight without the great risk that roving groups of P-47s would spot the movement and swoop down with devastating results. The complete lack of Luftwaffe support contributed to falling morale among German troops. They knew with certainty that if they heard or saw any aircraft, it belonged to the enemy. The breakout of the American 1st and 3rd Armies into the interior of France was partially a result of overwhelming air attacks by the American 8th and 9th Air Forces. Many thousands of sorties were flown by P-47s in support of Operation Cobra, which sprung Gen. Patton's 3rd Army loose to envelope the major portion of German forces in France by closing their escape route between Argentan and Falaise.

The war in Italy was somewhat different than that in France. Italy is largely a mountainous country, and the progress of ground forces was very much slowed by expert use of this terrain by the Germans. P-47s served with great distinction in Italy. Flying with the 12th and 15th Air Forces, the Jugs performed every type of mission imaginable. Eventually, just as in the ETO, all 15th Air Force P-47s were transferred to the 12th Tactical Air Force, being replaced by P-51s. As in the ETO, P-47s still flew escort for medium bombers. However, their primary mission had become that of tactical fighter-bomber. One of the lesser known units serving in the war in Italy was the Brazilian squadron operating P-47s flying with the USAAF's 350th FG. The P-47 performed with the same outstanding effectiveness in the MTO as they did with the 8th and 9th Air Forces in the ETO.

A Brazilian operated P-47D
This P-47D-30-RE served with Forca Aerea Brasileira in Italy. This Brazilian unit was attached to the 350th FG of the 12th Air Force. Note the dorsal fillet at the base of the rudder leading edge. This partially restored the flat plate side area of the bubble canopy P-47s. A larger and more effective fillet would be installed on the long range P-47N.

The principal model of the Thunderbolt in use at the time was the P-47D. These included several different sub-models of the D. It should be mentioned that there were no less than 21 individual sub-models of the P-47D alone. These included the P-47D-25-RE that began arriving in the ETO in May of 1944. The -25 was considerably different in appearance as compared to the previously manufactured models. The fuselage had been cut down behind the cockpit and a new bubble type of canopy replaced the old framed glass that had remained essentially unchanged since the YP-43. The new canopy presented the pilots with an unparalleled view outside of the aircraft. It did, however, actually cause an increase in drag, which reduced the maximum speed of the fighter by about 6 mph. On the positive side, the new Thunderbolt arrived with 100 gallons greater internal fuel capacity. This brought the total internal fuel load to 370 gallons. Finally, the P-47 had the range to fly as far as Berlin. Ironically, this new P-47 arrived when most Thunderbolts were about to be transferred to the 9th Air Force and used as tactical fighter-bombers. In point of fact, by 1945 every 8th Air Force Fighter Group was flying the P-51 Mustang with one notable exception. The 56th were allowed to keep their much loved Thunderbolts.

A P-47D-30-RE
This P-47D-30-RE warms up on a snow covered taxiway prior to taking off on a ground attack mission during the Battle of the Bulge. Based only a short distance from the front lines, these fighters would frequently fly as many as four combat missions a day. Especially during the unexpected German attack through the lightly defended Ardennes forest. This fighter of the 356th Fighter Squadron will soon drop its 500 lb. bombs on luckless Wehrmacht troops trapped in a pocket of their own making. Note the quad .50 caliber machine gun anti-aircraft mount in the foreground. These airfields were close enough to the front as to expect Luftwaffe raiders at almost any time. Fortunately, the decimated Luftwaffe could rarely break through the Allied fighters. Nonetheless, forward airfields such as this were ready and alert for just that possibility.

Many of the Fighter Groups flying the P-47 in June of '44 were still flying some of the older "razor back" models with the framed canopy. These included the ultimate "razor back", the P-47D-23-RA. This Evansville built fighter was equipped with the latest Curtiss Electric paddle blade propeller. Of all the D models, this one was the fastest and best climbing.

As the war in the ETO progressed, the P-47 would pound the German army without let-up or mercy. Soon after the invasion began, 9th Air Force Fighter Groups were transferred from Britain to newly captured or prepared forward airfields not far from the front lines. This greatly shortened the response time required between receiving a call for air support and actually being able to deliver the support. In many instances, the Thunderbolts were based barely 5 minutes flying time from the battle area. By December of 1944, all tactical aircraft were based in France or Belgium.

A P-47D-27-RE based in France
This P-47D-27-RE of the 404th FG sits awaiting a mission. It has been fully armed with three 500 lb. bombs and four 5 inch rockets. Basing fighter-bombers close to the front greatly shortened reaction time and tremendously enhanced ground attack coordination.

With the coming of June '44, something besides the invasion of France was on the minds of the people of Britain. On night of June 12-13 the Germans launched the first of over 6,700 V-1 flying bombs. This was the first of Hitler's Vengeance Weapons. They created near panic in Britain. While not exceptionally effective weapons in a strategic sense, they were effective at pulling RAF resources away from prosecuting the war to defending the airspace over Britain. Moreover, the V-1 (and later V-2 ballistic missile) did more to hurt British home front morale than did the air Blitz of 1940-41. The British government turned to the United States for assistance.

Eventually, Republic was informed of the British request for a high speed interceptor specifically to chase down and destroy the V-1. Remarkably, Republic already had a solution in hand. This would take the form of the the incredibly fast P-47M-1-RE. Let's go back more than a year and see how Republic came to have this speedster in their vest pocket when the British inspired inquiry arrived.

A pair of 56th FG P-47Ms taking off
These P-47M-1-RE fighters belong to the 56th Fighter Group. These are fitted with wing pylons for external stores. P-47Ms were originally produced without pylons, which were deemed unnecessary for chasing V-1 flying bombs. Once free of that duty, pylons were quickly added. The nearest fighter is that belonging to Lt. Col. Pete Dade.

The XP-47M was, essentially, developed collaterally with the XP-47J. The J was fitted with a high output version of the P&W R-2800. Specifically, the R-2800-57. This engine made 2,800 hp @ 2,800 rpm at 35,000 feet. This is in War Emergency Power. The aircraft actually attained 507 mph at an altitude of 34,300 feet. 2,800 hp is 133% of rated power. At military power (100%), the XP-47J could sustain 470 mph. 435 mph was attained at 81% of it's rated power (1,700 hp). All performance figures were obtained at 34,300 feet. The J model was an especially good climbing fighter too. It had a climb rate at sea level of 4,900 fpm. At 20,000 feet, it was still rocketing up at 4,400 fpm, and got there in 4 minutes, 15 seconds. Time to 30,000 feet was only 6 minutes, 45 seconds. Now that's an interceptor! Yet it had a usable range of 1,075 miles. Rather impressive performance. Nor was this a stripped down hotrod. It was fully armed and carried ballast in the wings equal to 267 rds per gun. The aircraft was flown to a height of 46,500 feet and was capable of a bit more.

The XP-47J after rollout
Chief test pilot Lowery Brabham warms up the XP-47J prior to an early flight in November of 1943. Note the exceptionally tight cowling installation and spinner. This layout worked well, but was not adopted for production P-47s due to increased cost and complexity. However, a similar cowling was incorporated into the XP-72 little more than a year later.

Originally designed to defeat the FW-190 series fighters, the XP-47J certainly would have exceeded this requirement. In point of fact, with its critical Mach of .83, it had the potential to chase down Me-262's by utilizing a shallow dive, taking advantage of its superior service ceiling.

Despite this incredible performance, the XP-47J was really nothing more than a technology demonstrator. Meanwhile, the R-2800 C series was installed in another, more ordinary Thunderbolt P-47C. The purpose was to trade a little performance for simplicity of manufacture. The idea being that a minimum of changes were required to the current aircraft for the C series engine.

The aircraft that resulted was designated the XP-47M. Not "officially sanctioned", the XP-47M was an "in-house" development program. The "M" was painted in chromate yellow to distinguish it from the run of the mill C and D models. Likely, this overly bright paint scheme was selected to indicate it's test status in order to prevent over-zealous P-47 and F6F pilots from making mock attacks, as was the standard rule of the day over wartime Long Island.

Right out of the starting gate, the XP-47M the horse to beat in terms of speed. The XP-47M proved to be nearly as fast as the XP-47J. 488 mph was obtained on at least one flight. The official maximum speed is 470 mph. However, over-boosting the engine could tweak another 15 to 20 mph out of the big fighter. Some may find this next tidbit hard to swallow, however, the test documents still exist.

During durability testing of the C series R-2800 by Republic, it was decided to find out at what manifold pressure and carburetor temperature caused detonation. The technicians at Republic ran the engine at extreme boost pressures that produced 3,600 hp! But wait, it gets even more amazing. They ran it at 3,600 hp for 250 hours, without any failure! This was with common 100 octane avgas. No special fuels were used. Granted, the engines were largely used up, but survived without a single component failure. Try this with Rolls Royce Merlin or Allison V-1710 and see what happens.

As mid June of 1944 arrived, so did the first of Germany's Vengeance weapons. Flying at speeds right around 400 mph., the V-1 was not easy to intercept prior to flying over populated areas, where knocking it down could have a worse effect than leaving it alone. Many of the RAF's latest fighters were thrown into intercepting the "Buzz Bombs", preferably over the English Channel. Tempests, late Mark Spitfires and even the jet powered (but not especially fast) Meteors were put to work intercepting the deadly "Doodle Bugs".

Upon the USAAF being informed of the XP-47M, three YP-47M development aircraft were immediately ordered. These were built using P-47D-27-RE fighters straight off the production line. Having already logged hundreds of flights with the XP-47M, beginning in mid 1943, Republic had a big leg up in terms of development time. Actual production P-47M fighters used the P-47D-30-RE as the basic airframe.

The production P-47M fighters did not reach operational status until after many of the V-1 launch sites were over-run by Allied ground forces. Deployed to 3 squadrons of the 56th Fighter Group, the new fighter likely did not chase very many flying bombs. Inasmuch as most aviation historians claim that the P-47M was designed specifically to intercept the V-1, it will come as a surprise to them to learn that the prototype existed more than a year before the first V-1 was launched at Britain. Moreover, the P-47D, deployed in large numbers, was certainly fast enough to overtake the V-1. It was only coincidence that the XP-47M and the R-2800 C series engines were available when the V-1's began falling on London.

The new M models also suffered a fair amount of teething troubles. The C series engines suffered from high altitude ignition leaks and burned pistons. The 56th kept many of their older D models until the new M had its bugs corrected. Nonetheless, once sorted out, the P-47M was the fastest propeller driven fighter to see combat service in any Air Force in the ETO. Capable of speeds up to 475 mph, the M was a true "hotrod".

As the German army was pushed closer to the border of their homeland, newer sub-models of the P-47D found their way into service. The P-47D-27-RE arrived with an up-rated engine of 2,430 hp. and Hamilton-Standard propeller. The P-47D-28-RA was essentially the same aircraft, but used a Curtiss Electric prop. Some of the next to last sub-model, the P-47D-30-RE, incorporated a new dorsal fillet at the base of the rudder assembly. Virtually all of the final D model, the P-47D-40-RA had the fillet installed. The loss of side area due to the cutting down of the fuselage (to accommodate the bubble canopy), reduced the linear stability of the bubble topped Jugs. This could lead to a loss of control if rudder deflection was too great at low speeds. The fillet partially corrected this rudder force over-balance condition. It would not be fully eliminated until the final production model of the Thunderbolt. The P-47D-40-RA was the first P-47 to have the new K-14 gunsight installed at the factory. It was also the first Thunderbolt to carry the new tail warning radar equipment.

As the war in the Europe came to end in early May of 1945, the mighty P-47 Thunderbolt was to shoot down its last aerial adversary on May 4th. The victim was one of the speedy Me 262 jet fighters. By May 6th, only armed recon missions were being flown in the ETO. Two days later, the war with Germany was officially at an end.

While peace had come to Europe, war was still raging on the other side of the world. It was in the far reaches of the Pacific that the latest, and possibly greatest model of the P-47 would hurl itself at the Japanese. Too late to impact the war in Europe, the P-47N would set a new standard for single engine long range performance.

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