<p>The P-51 Mustang, arguably the greatest American fighter of all time and among the greatest from any nation, was not requested by the US Army. It began as the company NA-73X (civil registry NX 19998), designed and assembled with remarkable haste in the mid-1940s by a company, North American Aviation of Los Angeles, that had never before made a fighter. North American, established in 1934 and presided over by J. H. 'Dutch' Kindelberger, was contacted by the British Purchasing Commission in 1940 as a potential new supplier of the Curtiss P-40. Company designers Raymond Rice and Edgar Schmued, the latter a veteran of service with Messerschmitt and Fokker, wanted instead to create a new fighter powered by the 1,150-hp (857.6-kW) Allison V-1710-39 inline engine used in the P-40. The coolant section for the powerplant would be located behind and below the pilot, a configuration tried on the prototype P-40 but not on subsequent production machines, and tried again on the Curtiss XP-46. The designers' decision turned out to be half right, since a later engine change would be needed to assure the Mustang's greatness. The British agreed on the proviso that the NA-73 fighter be completed within 120 days. Kindelberger's fighter team actually conceived, designed and constructed the prototype in 102 days and had to wait three weeks longer for Allison to deliver an engine. Test pilot Vance Breese took the unpainted, unmarked NA-73X aloft on its maiden flight on 26 October 1940.
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<p>On 29 May 1940, the UK ordered 320 of the yet-unflown NA-73 fighters under an arrangement which called for two examples to be given to the USAAF without cost as the XP-51. Much, much later, USAAF chief of staff General H. H. 'Hap' Arnold would acknowledge that it had been an extraordinary error not to have entered the fighter into American squadron service immediately. The first production RAF Mustang Mk I (AG345) flew within a year of the prototype and the second (AG346) was first to arrive in the United Kingdom, in November 1941. Although the two XP-51s (41-38/39) were soon flying in US markings, American planners preoccupied with the Lightning and Thunderbolt paid not nearly enough attention to the new design—although, in fact, more than has been generally suggested.
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<hi style=hdr1>Major Improvements</hi>
<p>The Mustang was a low-wing single-seater, a sleek, all-metal, stressed-skin fighter not unlike the Messerschmitt Bf 109 but much larger and considerably more advanced. It was one of the first fighters to employ a laminar-flow wing which had its maximum thickness well aft and resulted in greatly reduced drag. It differed from nearly all fighters of its time in having square-cut tips to both wing and tail surfaces. The liquid-cooled engine with the radiator far back under the rear fuselage, as noted, further reduced drag. The big fighter reached 382 mph (615 km/h), a speed not then possible even for the smaller, sleeker Spitfire which carried half as much fuel.
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<p>The RAF Mustang Mk I flew its first combat mission on 27 July 1942 and, three weeks later, flew close support for the Dieppe landings. Despite the fighter's superb potential, the limitations of its Allison engine relegated the RAF's 620 Mustang Mk I and Mk IAs to ground-attack and reconnaissance duties. Meanwhile, still moving with undue caution, the USAAF ordered 150 P-51s armed with four 20-mm wing cannon; 310 P-51As were then ordered, with 1,200-hp (895-kW) V-1710-81 engine, four wing 0.5-in (12.7-mm) machine guns and underwing racks for two 500-lb (227-kg) bombs or two 150-US gal (568-liter) drop tanks.
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<p>In England, the dramatic step which would assure the Mustang's place in history occurred when Rolls-Royce proposed installing the Merlin engine in this excellent airframe. Thought was given to locating the engine behind the cockpit in the manner of the Bell P-39 Airacobra, but a more conventional layout was decided upon. Four RAF Mustangs (AL963, AL975, AM203 and AM208) were equipped with Merlins and four-bladed propellers and performed so well, exceeding 400 mph (644 km/h), that North American began plans for P-51 variants powered by the 1,520-hp (1,134-kW) licence-built Merlin 61, the Packard V-1650-3.
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<p>The USAAF ordered 500 Allison-powered A-36 aircraft, identical to the P-51A but for dive brakes which overstressed the airframe and had to be wired inoperative. The A-36A was never really wanted for the attack role but was used as a device to keep production going while the merits of the basic design were still being argued. To confuse things further, the A-36A was known initially as the Apache and later as the Invader until the Mustang name stuck. The airplanes were moderately successful in Sicily and southern Italy, and claimed their share of Luftwaffe victims in air-to-air combat despite the 'attack' appellation.
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<p>Some P-51s were converted for the photo-reconnaissance role as F-6As. Finally, a Merlin-powered variant, the XP-51B, took to the air on 30 November 1942 with Bob Chilton at the controls. The US Army had ordered 2,200 P-51Bs before that maiden flight. A bit more cantankerous than earlier Mustangs, reliable but not as easy to fly, the P-51B retained a flush pattern framed canopy, as did the P-51C, armed with six 0.5-in (12.7-mm) guns. Most Mustangs were to come from North American's Inglewood, California, facility but the P-51C, reflecting wartime expansion of the aircraft industry, was produced at the firm's Dallas, Texas, plant.
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<hi style=hdr1>England to Berlin</hi>
<p>The P-51D variant first ordered in 1943 introduced the bubble canopy and a dorsal fin to correct stability problems. In later P-51Ds, an 85-US gal (322-liter) fuel cell was added behind the pilot's seat, bringing total fuel capacity to the point where the P-51D could range all the way from England to Berlin, as it did by March 1944 with Lieutenant Colonel Donald L. Blakeslee's 4th Fighter Group. The long-range fighters weaving above massed formations of B-17 and B-24 bombers greatly complicated the Third Reich's air defense burden and, once drop tanks were discarded, could fight on equal or better terms with anything belonging to the Luftwaffe. By 1944, early P-51Bs were operating in Burma, and later machines would range against the Japanese homeland from le Shima and Iwo Jima, but it was in Europe where the type excelled. First Lieutenant Urban L. Drew of the 361st Fighter Group illustrated this by shooting down two Messerschmitt Me 262 jet fighters.
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<p>Following F-6B and F-6C variants of flush-canopy Mustangs, good results were obtained with the bubble-canopy F-6D tactical reconnaissance craft, 136 of which were converted from P-51D standard at Dallas with hatches for oblique and vertical cameras in the rear fuselage and additional radio (including DF) gear. Although the earlier Malcolm hood which improved visibility on the Mustang Mk II and Mk III was also employed by the USAAF, the bubble canopy became the accepted feature and a few so-equipped P-51Ds operated in British service as the Mustang Mk IV. One hundred P-51D airframes were assembled in Australia by Commonwealth, and 226 more were manufactured there. Ten USAAF machines were converted to two-seat trainers as the TP-51D.
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<hi style=hdr1>Minimizing Weight</hi>
<p>The P-51E designation was not used. Three XP-51F airframes (4343332/43334) came from Inglewood as the first lightweight Mustang, with the V-1650-7 Merlin but with major internal redesign which lowered maximum take-off weight to 9,060 lb (4,110 kg) and introduced new wing and landing-gear features. One of these (FR409) reached the RAF as the Mustang Mk V. Two further lightweight Mustang test ships, designated XP-51G (43-43335/43336), were powered by the 1,500-hp (1,119-kW) Rolls-Royce Merlin 145 with an unusual Rotol five-bladed propeller. The XP-51G grossed a mere 8,765 lb (3,975 kg) and reached a top speed of 468 mph (753 km/h) in level flight. One (FR410) was flown by the RAF. These efforts to lower the Mustang's weight culminated in the taller-tailed production P-51H, 555 of which were built. The P-51H had a shorter bubble canopy, a four-bladed Aeroproducts propeller, and an increase in overall length to 33 ft 4 in (10.16 m). One (KN987) was evaluated in the UK. The P-51H did get into combat in World War II, a few flying missions from the Philippines before VJ-Day.
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<p>Two experimental XP-51Js (44-76027/76028) were similar to the lightweight XP-51F but for the 1,500-hp (1,119-kW) Allison V-1710119. The P-51K was the Dallas-built production equivalent of Inglewood's P-51D, differing only in having an Aeroprop propeller, and 1,500 were delivered during the war years,163 performing the reconnaissance role as the F-6K. The P-51L was a production machine cancelled at the war's end and the sole P-51M (45-11743) was another lightweight variant powered by a 1,400-hp (1,044-kW) V-1650-9A.
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<p>The P-51 was essential to wartime victory. About 40 USAAF fighter groups and 31 RAF squadrons operated the type. The P-51 was also among the most widely used of postwar fighters. The P-51D fought in Israel's war for independence and in China on both sides, an example being on display today in a Beijing museum. The Korean War of 1950-53 brought the type back into combat in US markings, Mustangs serving the USAF and Air National Guard to the end of the 1950s. Hundreds of flyable examples remain in the world today. The first USAAF machine, XP-51 41-38, was prudently saved for the US Air Force Museum at Dayton, Ohio.
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<p>"Getting a fully-loaded Mustang off the ground on a long-range mission was one bear of a job," says former First Lieutenant David Jones of the USAAF 4th Fighter Group. The P-51D loaded with maximum fuel, including drop tanks, tipped the scales at 11,600 lb (5,262 kg) and "could scarcely be handled until you'd burned an initial amount of that fuel away," says Jones.
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<p>The high risk of take-off on a maximum escort mission to Berlin is dramatized in a key crash scene in Len Deighton's novel 'Goodbye Mickey Mouse'. Jones and Deighton, members of Mustang International, a private group devoted to P-51 history and preservation today, agree that, however beautiful, the aircraft was difficult to get going and suffered from serious lateral stability problems. "The pilot had to be constantly alert to the need for opposite rudder to prevent a skid or sideslip which could throw the P-51 into a spin." A dorsal fin corrected this tendency but reduced maneuverability in combat. "But when you'd pickled off the drop tanks," says Jones, "you were on equal terms with the other guy. The Mustang could maneuver with and outgun even the latest models of the Focke-Wulf Fw 190. With a teardrop-shaped canopy, you had super visibility and could spot the other guy first." Lieutenant Urban Drew, air ace and killer of Messerschmitt Me 262 jets, flew both the P-51D and the later P-47N. Drew says that he greatly preferred the P-51D and wished that more had been available in the Pacific, where he flew after his European successes.
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<hi style=hdr1>Best Armament</hi>
<p>Colonel Hubert A. ('Hub') Zemke, the only man to command P-38, P-47 and P-51 fighter groups in Europe, considered the P-51D the best air-to-air fighter of the three below 25,000 ft (7,620 m) and found its armament adequate, although he preferred the Thunderbolt for its ruggedness, its eight 0.5-in (12.7-mm) guns (compared with six on the P-51D) and its better performance at higher altitude. Captain Henry Lawrence of the all-black 332nd Fighter Group had only the P-39 to compare with the P-51D, and considered the Mustang "as fine a flying machine as men could make, most of the bugs worked out of it by late in the war." On 24 March 1945, escorting bombers to Berlin, Lawrence joined the ranks of pilots who have shot down Me 262 jet fighters.
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<p>Although the lightweight P-51H did see limited combat in the Pacific, contrary to most published reports, the best Japanese fighters were no longer available as competitors by late 1945. Postwar tests showed the P-51H faster and more maneuverable than the Mitsubishi A6M5 Zero in all performance regimes. The P-51H had been relegated to second-line duties by 1950, however, and it was the more popular P-51D which went to war in Korea. The Mustang's 0.5-in (12.7-mm) guns and 5-in (127-mm) high-velocity aircraft rockets (HVAR) were of marginal effectiveness against North Korean T-34 tanks, but in the air P-51Ds cleared the skies with remarkable ease of North Korean Yakovlev fighters. Major Dean Hess, who instructed Republic of Korea Air Force (RoKAF) pilots in the P-51D, said that "the Mustang was remarkably easy for an inexperienced pilot to learn how to fly."
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<p>On 7 November 1950, Captain Howard Tanner of the 36th Fighter-Bomber Squadron at Kimpo AB, Korea, was flying a 'sweep' near the Yalu River when three MiG-15 jet fighters tore into his formation of F-51D Mustangs (as the P-51D had been redesignated on 1 June 1948). A fourth MiG locked onto Tanner and began firing from too far out. Tanner was able to turn inside the MiG, pull lead, and strike the newer, faster jet. Surprised by the American's aggressiveness, the MiGs pulled away, but then re-engaged. Tanner and his wingmen scored further hits on MiGs without themselves sustaining damage, although they could not confirm any certain kills. This was early evidence of the coming Chinese entry into the Korean War, a conflict that was waged by another North American product, the F-86 Sabre.
<item><hi format=bold>Powerplant:</hi> one 1,590-hp (1,186-kW) Packard V-1650-7 Merlin liquid-cooled 12-cylinder Vee piston engine driving a four-bladed Hamilton Standard propeller
<item><hi format=bold>Performance:</hi> maximum speed (clean) 448 mph (721 km/h); initial climb rate 3,475 ft (1,059 m) per minute; operating radius with maximum fuel 1,300 miles (2,092 km)
<item><hi format=bold>Weights:</hi> empty 7,125 lb (3,232 kg); maximum take-off 11,600 lb (5,262 kg)
<item><hi format=bold>Dimensions:</hi> span 37 ft 1 in (11.29 m); length 32 ft 3 in (9.83 m); height 13 ft 8 in (4.17 m); wing area 235 sq ft (21.83 m<su>2</su>)
<item><hi format=bold>Armament:</hi> six 0.5-in (12.7-mm) fixed forward-firing machine guns, plus provision for two 500-lb (227-kg) bombs, eight rockets or other underwing ordnance in place of drop tanks
