P-51 Mustang In WWII - America's Most Capable Wartime Fighter

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North American P-51 Mustang D

Why It Was The Most Famous Plane Of The World War II

During World War II, few weapons of war stood out like fighter planes – on both sides. The development of fighter planes between World War I and World War II will go down in history as one of the greatest ages in the advancement of technology in military aircraft history.

In the air war in Europe, in 1940 the British and Germans both mounted bomber raid over their respective capitals. Both sides possessed outstanding fighter interceptors – the British Spitfire and the German Messerschmitt Bf 109. After suffering substantial loses to the fighters in daylight bombing raids, both sides switched to night raids to avoid the deadly fighters. In 1942 the U.S. joined the fray by introducing their Boeing B-17 Flying Fortress and the B-24 Liberator four-engine heavy bombers. Already committed to the air war in North Africa, the U.S. would not participate in Europe in a meaningful way until 1943. Confident in the design and firepower of their bombers, the U.S. was certain their bombers would not need a fighter escort, and, at this time no Allied fighter had the range anyway.

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Boeing B-17 Fly Fortress

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Consolidated B-24 Liberator

It wouldn’t take long for the U.S. to see the reality of the truth. Mission after mission, the U.S. suffered terrible loses as German 109’s and 190’s waited until U. S. fighters reached their fuel limit and were forced to turn back. One mission best exemplifies this dilemma. The U.S. targeted German fighter, industrial production, and oil refinery production. The “The Point-Blank Directive” was the designated mission to attack the cities of Schweinfurt, Regensburg, and Wiener Neustadt in Austria. The B-17 1st and 4th heavy bombardment groups would attack German targets while the Ninth Air Force B-24’s based in Libya would attack targets in Austria.

The plan was to split the German defense, these raids were supposed to occur simultaneously, after the raid the Regensburg force would land at airfields in North Africa. Unfortunately, fog delayed the Schweinfurt force’s takeoff, but the Regensburg force left on time. As a result of the delay, enemy fighters hit the first force, landed, rearmed, refueled, and then engaged the delayed second force. Without escort for much of the mission, the bombers faced wave after wave of Luftwaffe fighters alone. To their credit, the raid caused heavy damage at both factories, however, 60 of the 376 bombers—about 1 in 6 of those dispatched—were shot down and more than 600 Airmen were killed, missing, or captured. That was not the total cost. On the flight back to England the Regensburg force attacked a target in France and suffered more loses. In total, 118 WW2 planes were lost. Pilots would later name the raid “Black Thursday” for the disastrous results. The same results would occur on the second mission on October 14.

After more disastrous daylight loses, the 8th Air Force was forced to halt massive raids deep into Germany. It was now clear that a reliable fighter escort was needed to facilitate the Normandy landings planned for mid-1944. Fast forward to early 1944, The Mighty 8th Air Force introduced several significant changes. Legendary General Jimmy Doolittle took command of the 8th Air Force. When bomber pilots gathered for the briefing for a mission to attack Berlin there was a new optimism in the air. The pilots were aware that this time the results would be different because the 8th Air Force now had the fighter they needed to accompany the bombers all the way to their targets, and back. The P-51 Mustang.

The renewed campaign for air supremacy began in March 1944 when the Americans made their first major daytime bombing raids on Berlin. On March 6, 1944, over 800 US bombers, escorted by over 900 fighters, attacked Berlin. It didn’t take long for the 8th Air Force to realize the importance of the Mustang, by the end of 1944, 14 of the 15 fighter squadrons of the U.S. Eighth Air Force were composed of Mustangs.

The Birth Of The P-51 Mustang

The P-51 is widely regarded as the finest all-around piston-engine fighter of World War II to be produced in significant numbers. The P-51’s journey to greatness began when the British turned to America for assistance in obtaining fighter aircraft production in WW2. The British were interested in the Curtiss P-40 Warhawk, the front-line U.S. fighter at the time. The Curtiss factory in Buffalo, NY was working at the peak capacity and was now licensing other manufactures to build P-40’s.

Already impressed with North American Aviation, which had supplied the British with training aircraft, the NA-64 Yale, and AT-6 Texan, eager for the business North American offered a different option. In addition, North American produced the outstanding Mitchell B-25 medium bomber that would come to fame when Colonel Jimmy Doolittle led a raid of B-25’s that were the first U.S. aircraft to attack the Japanese Home Islands in 1942. North American leader, James “Dutch” Kindleberger artfully suggested that his company could build a fighter of their own design, that could fly higher, faster, and longer than the P-40. The British agreed and North American delivered in a little over 100 days, something unheard of at the time. After completing the prototype, North American agreed to produce 320 NA-73’s.

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James "Dutch" Kindleberger

The British requirements were that they cost no more than $40,000, use the Allison V-1710 engine, delivery no later than January 1, 1941. Over a three-week period, the North American design team worked from a New York hotel to draw up general arrangement drawings for the project. The next object would be to gain approval of the selling of the aircraft to a foreign government – from the Army Air Corp and U.S. government. Within a month they obtain the necessary approval from the Roosevelt administration. Even though they were designated for foreign sale, the Army Air Corp requested two planes for testing. North American decided to take a two-step process in development. First, utilize the latest technology available, and consider lessons learned in the air war underway in Europe.

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Edgar Scheumd

British Purchasing Commission official Sir Henry Self was concerned that North American had not ever designed a fighter, insisting they obtain the drawings and study the Curtiss XP-46 experimental aircraft and the wind tunnel test results for the P-40, to address their concerns about North American’s inexperience. North American purchased the drawings and data from Curtiss to satisfy the Purchasing Commission. Edgar Schmued was chosen to lead the design team. The cornerstone of North American’s production was its practice of mass production. The team focused on a key component of the aircraft – the wings. They choose a wing designed using laminar flow airfoils, which were developed co-operatively by North American Aviation and the National Advisory Committee for Aeronautics (NACA). Test showed that these airfoils generated low drag at high speeds. NACA five-digit airfoils and NAA/NACA 45–100 airfoils were compared in wind tunnel testing at the University of Washington Kirsten Wind Tunnel. The results of this test showed the superiority of the wing designed with the NAA/NACA 45-100 airfoils.

Another area of focus was the placement of the “cooling arrangement”. After extensive testing it was determined that the “Meredith Effect” – the offset by careful design of the cooling duct such that useful thrust is produced by the expansion of the hot air in the duct. Another aspect North American utilized was “conic sections” - the airframe was divided into five main sections—forward, center, rear fuselage, and two wing halves were fitted with wiring and piping before being joined.

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NA-73 XP-51

By all appearances the XP-73 appeared to be a good concept. However, it was found to have a major flaw that would prevent it from front line use in aerial combat in Europe – the Allison engine. The British knew that aerial combat often occurred at 15,000 feet or higher. Fighters like the Spitfire, Hurricane, Messerschmitt Bf 109 and Focke Wulf Fw 190 had to be at peak performance at higher altitudes. The Allison engine in the Mustang I had a single-stage supercharger – it performed well at below 15,000 feet, but not above. Allison produced the V-1710-45, which featured a variable-speed auxiliary supercharger, and developed 1,150 horsepower at 22,400 feet. NAA studied the possibility of using it but fitting its excessive length in the Mustang would require extensive airframe modifications and cause long production delays.

The P-51 Mustang In Europe

The USAA showed some interest in many of the P-51 Mustang in WW2 performance – sturdy airframe, long distance, and other aspects. However, the Allison engine lacked a supercharger that prohibited it becoming a front-line fighter. Instead, the Americans designated the P-51 to be utilized as a dive-bomber. In 1942 the Army ordered 500 aircraft and designated them the A36A Apache or A36A Invader. The Apache’s performed well with their limits – reconnaissance, ground attack, low-level bombing.

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RAF A-36A Apache

Thanks to incessant testing, a solution to the engine problem for the Mustangs was closer than they could have imagined. The answer was a British engine already in use by the British in the Spitfire, Hurricane, Mosquito, and Lancaster – Merlin engine. During their final evaluation of the Mustang, the British assigned Ronnie Harker to fly the Mustang before the decision would be made to scrap the order. In the process, he measured the engine compartment and discovered it was an exact match for the Rolls Royce Merlin-61 power plant. Wind tunnel tests bore out Harker’s prediction that the Mustang when matched up with the Merlin, would be superior in performance at any altitude over any other fighter then flying. And with external wing tanks could be the answer to Allies prayers. The first hurdle would be the problem of Merlin engine production. Rolls-Royce was already at peak production, so Packard Motor Car Company was licensed to manufacture the fabled Rolls Royce Merlin engine in the U.S. The Merlin-61 had a two-speed, two-stage, intercooled supercharger, designed by Stanley Hooker of Rolls-Royce capable of 1570 horsepower, increasing the speed from 390 to 440 mph. The real key to the P-51’s success would be its fuel capacity - 184 gallons plus 150 gallons carried externally.

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North American P-51 C

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North American P-51 D

By mid-1943, Mustangs are pouring out of North American production facilities in Inglewood, CA and Dallas, TX. The Inglewood Mustang is the P-51B and Dallas is P-51C. With its success and availability, the Mustang was now deployed in every theatre of the war. As good as the Mustang was now, another important change would occur. Again, the British would propose another update. British pilots said the P-51B’s canopy doesn’t allow for a pilot to look behind him, in its current “bird-cage” configuration. RAF pilot Robert Malcom suggested replacing the cage canopy with a bubble canopy which allowed the pilot a 360-degree view. The new bubble canopy would now be standard for new P-51’s, along with a change to a four-blade propeller. In addition, the 30 caliber guns would be replaced with 6 Browning 50 caliber guns. This would become the iconic P-51D model.

The first fighter group to receive the new and improved Mustang is the 354th fighter flying out of England. General Doolittle’s first objective of protecting his bombers was now complete. Next would be sweeping the Luftwaffe from European skies. Doolittle released the P-51’s to seek out the Luftwaffe wherever they were. In many cases P-51 pilots would range ahead of the bombers to take on the Luftwaffe. And once the bombers were ushered back to a handoff to P-38 and P-47 escorts the P-51’s would drop down and attack airfields and other targets of opportunity. When the Allies landed in Normandy in June 1944, the Luftwaffe was virtually invisible. With the Allies now in Normandy and Italy, and the Russians rampaging in the East, Germany was doomed. It would take 11 months of hard fighting to bring the war in Europe to an end. The P-51’s claimed some 4,950 aircraft shot down in air-to-air combat along with 4,131 destroyed on the ground.

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P-51 Pilot Capt "Bud" Anderson

The P-51 In The Pacific

At the same time in pacific, the once invincible Japanese forces were suffering the same fate as Germany on an even greater scale. In early 1945, P-51C, D, and K variants also joined the Chinese Nationalist Air Force and took the fight to Japanese, replacing the venerable P-40 Warhawk. The Allies were now striking at the Japanese from three different directions. The British, Australian, and Americans were advancing through Burma and other locations on or near the mainland. General Douglas MacArthur was rapidly advancing towards a triumphant return to the Philippines. Admiral Chester Nimitz was leading the largest naval force the world had ever seen on an island-hopping campaign. Traveling long distances in the European Theatre was difficult, but not nearly as difficult as traveling over the vast Pacific Ocean. The Pacific War was a carrier war where opposing ships very seldom saw each other.

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Ground Crew loading P-51 Machine Guns

By mid-1943 the tide of the air war in the Pacific was beginning to turn as America’s strength began show in a significant way. The Americans now had two outstanding Naval WW2 fighters – The Grumman F6F Hellcat, and F4U Corsair. And the Army Air Corp’s P-38 Lightning was making a difference. Of the three, the P-38 Lightning had the greatest range. With introduction of the Mustangs, its range was superior, but still not effective enough. Test trial were ordered to evaluate the Mustang for carrier operations, even though it wasn’t designed for such operations. A classified test program “Operation Seahorse” was commenced and North American P-51D was modified for carrier operations. After two months of trials, the test P-51 was transferred to the USS Shangri-la for sea-trials. Twenty-five test flights were conducted by pilot Bob Elder. The first landing occurred on November 15, 1943.

In the end, the Mustang air frame construction was not suitable for repeated carrier landings, and events in the war changed dramatically when the U.S seized the Mariana Islands, along with the islands of Iwo Jima and Okinawa. The U.S. now had bases close enough to the Japanese Home Islands that Mustangs could utilize. Just as they had done in the European Theatre, the Mustang was the choice to escort America’s newest bomber, the ground-breaking B-29 Superfortress. On many of the eight-hour plus missions, after escort duty, the Mustangs would drop down and ravage the Japanese countryside. By war’s end the Mustang in WW2 arguably ended the war as the preeminent fighter of WW2.

Conclusion

The debate about the best fighter plane of World War II has raged for decades. It is true that there are numerous fighter planes worthy of the designation. The Spitfire, Focke Wulf Fw 190 and others made their mark suring the war. However, in the end there was only one P-51 Mustang.

Evolution Of World War 2 Fighter Aircraft

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