North American P-51 Mustang

The P-51 Mustang was an iconic American fighter of World War II and became a critical weapon in the air for Allies due to its performance and range.

North American P-51D Specifications

General

• Length: 32 ft. 3 in.
• Wingspan: 37 ft.
• Height: 13 ft. 8 in.
• Wing Area: 235 sq. ft.
• Empty Weight: 7,635 lbs.
• Loaded Weight: 9,200 lbs.
• Maximum Takeoff Weight: 12,100 lbs.
• Crew: 1

Performance

• Maximum Speed: 437 mph
• Range: 1,650 miles (w/ external tanks)
• Rate of Climb: 3,200 ft./min.
• Service Ceiling: 41,900 ft.
• Power Plant: 1 × Packard V-1650-7 liquid-cooled supercharged V-12, 1,490 hp

Armament

• 6 × 0.50 in. machine guns
• Up to 2,000 lb of bombs (2 hardpoints)
• 10 x 5" unguided rockets

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Development of the P-51 Mustang

With the outbreak of World War II in 1939, the British government established a purchasing commission in the United States to acquire aircraft to supplement the Royal Air Force. Overseen by Sir Henry Self, who was charged with directing RAF aircraft production as well as research and development, this commission initially sought to acquire large numbers of the Curtiss P-40 Warhawk for use in Europe. While not an ideal aircraft, it the P-40 was the only American fighter then in production that came close to the performance standards required for combat over Europe. Contacting Curtiss, the commission's plan soon proved unworkable as the Curtiss-Wright plant was unable to take new orders. As a result, Self approached North American Aviation as the company was already supplying the RAF with trainers and was attempting to sell the British their new B-25 Mitchell bomber.

Meeting with North American president James "Dutch" Kindelberger, Self asked if the company could produce the P-40 under contract. Kindelberger replied that rather than transition North American's assembly lines to the P-40, he could have a superior fighter designed and ready to fly in a shorter span of time. In response to this offer, Sir Wilfrid Freeman, the head of the British Ministry of Aircraft Production placed an order for 320 aircraft in March 1940. As part of the contract, the RAF specified a minimum armament of four .303 machine guns, a maximum unit price of $40,000, and for the first production aircraft to be available by January 1941.

Design

With this order in hand, North American designers Raymond Rice and Edgar Schmued began the NA-73X project to create a fighter around the P-40's Allison V-1710 engine. Due to Britain's wartime needs, the project progressed rapidly and a prototype was ready for testing only 117 days after the order was placed. This aircraft featured a new arrangement for its engine cooling system which saw it placed aft of the cockpit with the radiator mounted in the belly. Testing soon found that this placement allowed the NA-73X to take advantage of the Meredith effect in which heated air exiting the radiator could be used to boost the aircraft's speed. Constructed entirely of aluminum to reduce weight, the new aircraft's fuselage utilized a semi-monocoque design. 

First flying on October 26, 1940, the P-51 utilized a laminar flow wing design which provided low drag at high speeds and was the product of collaborative research between North American and the National Advisory Committee for Aeronautics. While the prototype proved substantially faster than the P-40, there was a substantial drop in performance when operating over 15,000 feet. While adding a supercharger to the engine would have solved this issue, the aircraft's design made it impractical. Despite this, the British were eager to have the aircraft which was initially provided with eight machine guns (4 x .30 cal., 4 x .50 cal.).

The US Army Air Corps approved Britain's original contract for 320 aircraft on the condition that they received two for testing. The first production aircraft flew May 1, 1941, and the new fighter was adopted under the name Mustang Mk I by the British and dubbed the XP-51 by the USAAC. Arriving in Britain in October 1941, the Mustang first saw service with No. 26 Squadron before making its combat debut on May 10, 1942. Possessing outstanding range and low-level performance, the RAF primarily assigned the aircraft to Army Cooperation Command which utilized the Mustang for ground support and tactical reconnaissance. In this role, the Mustang made its first long-range reconnaissance mission over Germany on July 27, 1942. The aircraft also provided ground support during the disastrous Dieppe Raid that August. The initial order was soon followed by the second contract for 300 planes which differed only in armament carried.

The Americans Embrace the Mustang

During 1942, Kindelberger pressed the newly re-designated US Army Air Forces for a fighter contract to continue production of the aircraft. Lacking funds for fighters in early 1942, Major General Oliver P. Echols was able to issue a contract for 500 of a version of the P-51 which had been designed for a ground attack role. Designated the A-36A Apache/Invader these aircraft began arriving that September. Finally, on June 23, a contract for 310 P-51A fighters was issued to North American. While the Apache name was initially retained, it was soon dropped in favor of Mustang.

Refining the Aircraft

In April 1942, the RAF asked Rolls-Royce to work on addressing the aircraft's high altitude woes. Engineers quickly realized that many of the issues could be resolved by swapping the Allison with one of their Merlin 61 engines equipped with a two speed, two-stage supercharger. Testing in Britain and America, where the engine was built under contract as the Packard V-1650-3, proved highly successful. Immediately put into mass production as the P-51B/C (British Mk III), the aircraft began reaching the front lines in late 1943.

Though the improved Mustang received rave reviews from pilots, many complained about a lack of rearward visibility due to the aircraft's "razorback" profile. While the British have experimented with field modifications using "Malcolm hoods" similar to those on the Supermarine Spitfire, North American sought a permanent solution to the problem. The result was the definitive version of the Mustang, the P-51D, which featured a completely transparent bubble hood and six .50 cal. machine guns. The most widely produced variant, 7,956 P-51Ds were built. A final type, the P-51H arrived too late to see service.

Operational History

Arriving in Europe, the P-51 proved key to maintaining the Combined Bomber Offensive against Germany. Prior to its arrival daylight bombing raids routinely sustained heavy losses as current Allied fighters, such as the Spitfire and Republic P-47 Thunderbolt, lacked the range to provide an escort. With the superb range of the P-51B and subsequent variants, the USAAF was able to provide its bombers with protection for the duration of raids. As a result, the US 8th and 9th Air Forces began exchanging their P-47s and Lockheed P-38 Lightnings for Mustangs.

In addition to escort duties, the P-51 was a gifted air superiority fighter, routinely besting Luftwaffe fighters, while also serving admirably in a ground strike role. The fighter's high speed and performance made it one of the few aircraft capable of pursuing V-1 flying bombs and defeating the Messerschmitt Me 262 jet fighter. While best known for its service in Europe, some Mustang units saw service in the Pacific and the Far East. During World War II, the P-51 was credited with downing 4,950 German aircraft, the most of any Allied fighter.

Following the war, the P-51 was retained as the USAAF's standard piston-engine fighter. Re-designated the F-51 in 1948, the aircraft was soon eclipsed in the fighter role by newer jets. With the outbreak of the Korean War in 1950, the F-51 returned to active service in a ground attack role. It performed admirably as a strike aircraft for the duration of the conflict. Passing out of frontline service, the F-51 was retained by reserve units until 1957. Though it had departed American service, the P-51 was utilized by numerous air forces around the world with the last being retired by the Dominican Air Force in 1984.

Sources

• Ace Pilots: P-51 Mustang
• Boeing: P-51 Mustang
• Fighter Plans: P-51 Mustang
• Angelucci, Enzo, Rand McNally Encyclopedia of Military Aircraft: 1914-1980. The Military Press: New York, 1983. pp. 233-234.