The Mustang was among the best and best-known fighters used by the US Army Air Forces during World War II. Possessing excellent range and maneuverability, the P-51 operated primarily as a long-range escort fighter and also as a ground attack fighter-bomber. The Mustang served in nearly every combat zone during WWII, and later fought in the Korean War.
The P-51 Mustang, designed in 1940 after Great Britain requested that North American build P-40 Warhawks for the Royal Air Force, was at first ignored by US officials. The RAF agents initially approached the dominant US aircraft supplier, the Curtiss-Wright Corporation, with a request to place an order for more than 300 of their best fighters — the P-40 Warhawk — which was also the main fighter in U.S. Army Air Corps service. Curtiss-Wright turned the order down due to lack of factory capacity. The desperate British then turned to a small California company, North American Aviation, which specialized in building training aircraft. The British asked North American to consider a licensed production deal with Curtiss to build the Warhawk in their factory. The company’s president, “Dutch” Kindelberge knew that the P-40 Warhawk was a relatively old design that was tough and heavily armed, but slow and lacking the maneuverability and combat performance to go against the German Luftwaffe in air-to-air combat.
After some discussion, the young company president and his small design staff made an astonishing counter-proposal to the British. They offered to design and deliver a new airplane, using the latest in aviation technology. North American's better fighter, which flew as the NA-73X in October 1940. Production of the aircraft -- named Mustang I by the British -- began the following year.
North American’s designers decided to use two cutting-edge technologies that had never been included in a production fighter aircraft before. The first was the laminar-flow wing, the product of massive investments in the 1920s and 1930s by the US National Advisory Committee on Aeronautics (NACA), the forerunner of the National Aeronautics and Space Administration. This design “smoothed” the otherwise turbulent airflow across the wing surfaces, reduced drag, and increased aircraft speed and efficiency. The second was an untried cooling radiator design called the Meredith effect duct - a divergent - convergent duct with a radiator at its widest part. The theory was that the engine’s waste heat would accelerate the flow of air through the duct, producing a ramjet effect to reduce engine cooling drag at high speeds.
In the summer of 1941, the USAAF received two Mustang Is under the designation XP-51. Although flight tests of the new fighter showed promise, the USAAF did not immediately order the Mustang. After the personal intervention of Gen. Hap Arnold, however, the USAAF retained 55 Mustangs from a British order. These early Mustangs were restricted to reconnaissance and ground attack due to the limited performance of the Allison V-1710 engines. This engine had a simple, one-stage supercharger rated for low-altitude flight, since American doctrine at the time called for fighters to operate in direct support of ground troops at low level. Most of these became F-6A photo-reconnaissance aircraft, which equipped the first USAAF Mustang units, the 154th and 111th Observation Squadrons in North Africa in the spring of 1943.
In March 1942 the USAAF accepted the first production P-51A fighters. Although excellent at lower levels, the P-51A's Allison engines severely limited performance at high altitude. The USAAF employed P-51As in the China-Burma-India theater, where most combat took place at low altitude. In April 1942 the USAAF ordered an attack version equipped with dive brakes and bomb racks, the A-36 Apache. A-36s entered combat in June 1943 and served in North Africa, Italy and India.
The American tactic of low-altitude fighter combat proved to be flawed — aerial dogfights were high-altitude affairs in the European theater. The Allison engine was not up to the task because its supercharger lost power at high altitude. The British, however, had developed the Rolls Royce Merlin, with a superlative high-altitude supercharger. This innovative two-speed, two-stage supercharger allowed the Merlin to operate at high power to altitudes above 40,000 feet.
In the fall of 1942, Mustangs in the United States and Great Britain were experimentally fitted with British Merlin engines. One in the United States flew a remarkable 441 mph at 29,800 feet -- about 100 mph faster than the P-51A at that altitude. Mass production of the Merlin-powered P-51B and P-51C soon followed (nearly identical, North American produced the "B" in Inglewood, Calif., and the "C" in Dallas, Texas).
By the end of 1943, Merlin powered P-51Bs entered combat with the 354th Fighter Group in England. Eighth Air Force Mustangs provided long range escort to B-17s and B-24s and scored heavily over German interceptors. In December 1943 the first P-51B/C Mustangs entered combat in Europe with the 354th Fighter Group "Pioneers." By the time of the first US heavy bomber strike against Berlin in March 1944, the USAAF fielded about 175 P-51B/C Mustangs. Along with P-38 Lightnings, these P-51s provided sorely needed long-range, high-altitude escort for the US bombing campaign against Germany.
The P-51D - the most numerous variant with nearly 8,000 being built - incorporated several improvements, and it became. The most obvious change was a new "bubble-top" canopy that greatly improved the pilot's vision. The P-51D also received the new K-14 gunsight, an increase from four to six .50-cal machine guns, and a simplified ammunition feed system that considerably reduced gun jams.
The P-51 Mustang was one of the outstanding fighters in World War II. Popular history gives the majority of the credit to the addition of drop tanks to this aircraft which extended its range and allowed it to be used as an escort fighter for bomber operations in World War II. The Merlin engine and the incorporation of innovative, laminar flow wings and aerodynamic “smoothing,” along with a delivery oriented production system made the aircraft an outstanding escort fighter — the addition of the drop tanks just made it better.
The P-51D arrived in quantity in Europe in spring 1944, becoming the USAAF's primary long range escort fighter. The versatile Mustang also served as a fighter-bomber and reconnaissance aircraft. Few Luftwaffe aircraft could match the P-51D and the Mustang scored heavily over German interceptors. Providing high altitude escort to B-17s and B-24s during World War II, by the end of the war, the P-51s destroyed over 4,950 enemy aircraft in the air, more than any other Army Air Force fighter in Europe.
Mustangs served in nearly every active combat zone, including the Pacific where they escorted B-29s from Iwo Jima to Japan. P-51Ds arrived in the Pacific and CBI theaters by the end of 1944. In the spring of 1945, Iwo Jima-based P-51Ds started flying long-range B-29 escort and low-level fighter-bomber missions against ground targets in Japan.
North American eventually developed a considerably lightened Mustang, the P-51H. With a remarkable top speed of 487 mph, it was 50 mph faster than the P-51D. Although production began before the war ended, the P-51H did not reach frontline units in time to see combat. Between 1941 and 1945, the Army Air Force ordered 14,855 Mustangs (including A-36A dive bomber and F-6 photo-reconnaissance versions), of which 7,956 were P-51Ds with the "bubble" canopy and heavier armament. With the last of 555 P-51Hs completed in 1946, the production run of the Mustang ended with over 15,000 of all types built [including those built for the RAF].
Mustangs continued in service with the newly-formed US Air Force and many other nations after the war, though more advanced jet fighters relegated them to secondary status. Many of the USAF's Mustangs (redesignated the F-51) were surplused or transferred to the Reserve and the Air National Guard (ANG).
The F-51 (a redesigned P-51) achieved status as the first USAF fighter to participate in the Korean War. At the start of the Korean War the Mustang once again proved its usefulness, used primarily for close support of ground forces. After the initial invasion, USAF units were forced to fly from bases in Japan, and F-51Ds could hit targets in Korea that short-ranged F-80 jet fighters could not. Mustangs continued flying with USAF, South Korean Air Force (ROKAF), South African Air Force (SAAF) and Royal Australian Air Force (RAAF) fighter-bomber units on close support and interdiction missions in Korea until they were largely replaced by F-86F jet fighter-bombers in 1953.
F-51s flew in the Reserve and ANG until they were finally phased out in 1957.
The Mustang measured 32 feet three inches long, 13 feet eight inches high, and weighed 11,600 pounds. Equipped with six 50-caliber machine guns, the $54,000 P/F-51D attained a maximum speed of 379 MPH, a range of 826 nautical miles, and a top ceiling 41,900 feet.
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