Design and development
In April 1940 the British government established a purchasing commission in the United States, headed by Sir Henry Self. Self was given overall responsibility for Royal Air Force (RAF) production and research and development, and also served with Sir Wilfrid Freeman, the "Air Member for Development and Production". Self also sat on the British Air Council Sub-committee on Supply (or "Supply Committee") and one of his tasks was to organize the manufacturing and supply of American fighter aircraft for the RAF. At the time, the choice was very limited, as no U.S. aircraft then in production or flying met European standards, with only the Curtiss P-40 Tomahawk coming close. The Curtiss-Wright plant was running at capacity, so P-40s were in short supply.
North American Aviation (NAA) was already supplying its Harvard trainer to the RAF, but was otherwise underutilized. NAA President "Dutch" Kindelberger approached Self to sell a new medium bomber, the B-25 Mitchell. Instead, Self asked if NAA could manufacture the Tomahawk under license from Curtiss. Kindelberger said NAA could have a better aircraft with the same engine in the air sooner than establishing a production line for the P-40. The Commission stipulated armament of four .303 in (7.7 mm) machine guns, the Allison V-1710 liquid-cooled engine, a unit cost of no more than $40,000, and delivery of the first production aircraft by January 1941. In March 1940, 320 aircraft were ordered by Sir Wilfred Freeman who had become the executive head of Ministry of Aircraft Production (MAP), and the contract was promulgated on 24 April.
The NA-73X, which was designed by a team led by lead engineer Edgar Schmued, followed the best conventional practice of the era, but included several new features. One was a wing designed using laminar flow airfoils which were developed co-operatively by North American Aviation and the National Advisory Committee for Aeronautics (NACA). These airfoils generated very low drag at high speeds. During the development of the NA-73X, a wind tunnel test of two wings, one using NACA 5-digit airfoils and the other using the new NAA/NACA 45–100 airfoils, was performed in 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.
The other feature was a new radiator design that exploited the "Meredith Effect", in which heated air exited the radiator as a slight amount of jet thrust. Because NAA lacked a suitable wind tunnel to test this feature, it used the GALCIT 10 ft (3.0 m) wind tunnel at Caltech. This led to some controversy over whether the Mustang's cooling system aerodynamics were developed by NAA's engineer Edgar Schmued or by Curtiss, although NAA had purchased the complete set of P-40 and XP-46 wind tunnel data and flight test reports for US$56,000. The NA-73X was also one of the first aircraft to have a fuselage lofted mathematically using conic sections; this resulted in the aircraft's fuselage having smooth, low drag surfaces. To aid production, the airframe was divided into five main sections—forward, center, rear fuselage and two wing halves — all of which were fitted with wiring and piping before being joined.
The prototype NA-73X was rolled out in September 1940, just 102 days after the order had been placed; it first flew on 26 October 1940, 149 days into the contract, an uncommonly short gestation period even during the war. With test pilot Vance Breese at the controls the prototype handled well and accommodated an impressive fuel load. The aircraft's two-section, semi-monocoque fuselage was constructed entirely of aluminum to save weight. It was armed with four .30 in (7.62 mm) M1919 Browning machine guns, two in the wings and two mounted under the engine and firing through the propeller arc using gun synchronizing gear.
While the United States Army Air Corps (USAAC) could block any sales it considered detrimental to the interests of the US, the NA-73 was considered to be a special case because it had been designed at the behest of the British. In September 1940 a further 300 NA-73s were ordered by MAP. To ensure uninterrupted delivery Colonel Oliver P. Echols arranged with the Anglo-French Purchasing Commission to deliver the aircraft, and NAA gave two examples (41-038 and 41-039) to the USAAC for evaluation.
U.S. operational service
Pre-war doctrine was based on the idea "the bomber will always get through". Despite RAF and Luftwaffe experience, the USAAC still believed in 1942 that tightly packed formations of bombers would have so much firepower that they could fend off fighters on their own. Fighter escort was low-priority, and when an escort fighter was planned in 1941, not considering what the nascent NA-73 design could be developed into – at a time when a heavy fighter with twin engines was considered to be most appropriate, like the Americans' own fast-flying Lockheed P-38 Lightning for existing types in the USAAF inventory – it would be a heavily up-armed "gunship" conversion of a strategic bomber that would get a chance to prove itself in action. Additionally, a high-speed fighter with the range of a bomber was thought to be an engineering impossibility.
Eighth Air Force bomber operations 1942–1943
The 8th Air Force started operations from Britain in August 1942. At first, because of the limited scale of operations, there was no conclusive evidence American doctrine was failing. In the 26 operations flown to the end of 1942, the loss rate had been under 2%. This rate was better than the RAF's night efforts, and similar to the losses one would expect due to mechanical failure.
In January 1943, at the Casablanca Conference, the Allies formulated the Combined Bomber Offensive (CBO) plan for "round-the-clock" bombing – USAAF daytime operations complementing the RAF nighttime raids on industrial centers. In June 1943, the Combined Chiefs of Staff issued the Pointblank Directive to destroy the Luftwaffe's capacity before the planned invasion of Europe, putting the CBO into full implementation. Following this, the 8th Air Force's heavy bombers conducted a series of deep-penetration raids into Germany, beyond the range of escort fighters.
German daytime fighter efforts were, at that time, focused on the Eastern Front and several other distant locations. Initial efforts by the 8th met limited and unorganized resistance, but with every mission the Luftwaffe moved more aircraft to the west and quickly improved their battle direction. The Schweinfurt–Regensburg mission in August lost 60 B-17s of a force of 376, the 14 October attack lost 77 of a force of 291—26% of the attacking force. Losses were so severe that long-range missions were called off.
For the US, the very concept of self-defending bombers was called into question. But instead of abandoning daylight raids and turning to night bombing, as the RAF suggested, they chose other paths; at first it was believed that a bomber with more guns (the Boeing YB-40) would be able to escort the bomber formations, but, when the concept proved to be unsuccessful, thoughts then turned to the Lockheed P-38 Lightning. In early 1943 the USAAF also decided that the Republic P-47 Thunderbolt and P-51B be considered for the role of a smaller escort fighter and, in July a report stated that the P-51B was "the most promising plane" with an endurance of four hours 45 minutes with the standard internal fuel of 184 gallons plus 150 gallons carried externally. In August a P-51B was fitted with an extra internal 85 gallon tank and, although there were problems with longitudinal stability and some compromises in performance with the tank full, it was decided that because the fuel from the fuselage tank would be used during the initial stages of a mission, the fuel tank would be fitted in all Mustangs destined for VIII Fighter Command.
The P-51 Mustang was a solution to the clear need for an effective bomber escort. The Mustang was at least as simple as other aircraft of its era. It used a common, reliable engine and had internal space for a huge fuel load. With external fuel tanks, it could accompany the bombers all the way to Germany and back.
However, the Allison engine in the P-51A had a single stage supercharger that caused power to drop off rapidly after 15,000 ft. This made it completely unsuitable for combat at the altitudes USAAF bombers planned to fly. Following the RAF's initial disappointing experience with the Mustang 1 (P-51A) Ronald Harker from Rolls Royce suggested fitting a Merlin 61, as fitted to the Spitfire Mk IX. The Merlin 61 had a two speed two stage intercooled supercharger, designed by Stanley Hooker of Rolls Royce and this gave an increase in horsepower from the Allison's 1,200 to 1,620 (or 1,720 in War Emergency Power) an increase of top speed from 390 mph to 440 mph as well as raising the service ceiling to almost 42,000 ft.
Initial flights were completed October 1942 and a similar conversion then took place in the US leading to production of the P-51B beginning at North American's Inglewood California plant in June 1943 and P-51s started to become available to the 8th and 9th Air Forces in the winter of 1943–1944.
When the Pointblank offensive resumed in early 1944, matters had changed dramatically. The defense was initially layered, using the shorter range P-38s and P-47s to escort the bombers during the initial stages of the raid and then handing over to the P-51 when they turned for home. This provided continuous coverage during the entire raid. The Mustang was so clearly superior to earlier US designs that the Eighth Air Force began to steadily switch its fighter groups to the Mustang, first exchanging arriving P-47 groups for those of the 9th Air Force using P-51s, then gradually converting its Thunderbolt and Lightning groups. By the end of 1944, 14 of its 15 groups flew the Mustang.
The Luftwaffe's twin-engine heavy fighters brought up to deal with the bombers proved to be easy prey for the Mustangs and had to be quickly withdrawn from combat. The Focke-Wulf Fw 190A, already suffering from poor high-altitude performance, was no match for the Mustang at the B-17's altitude, and when laden with heavy bomber-hunting weapons as a replacement for the more vulnerable twin-engined Zerstörer heavy fighters, it suffered badly. The Messerschmitt Bf 109G was on a more even footing at high altitudes, but this lightweight platform was even more greatly affected by increases in armament. The Mustang's much lighter armament, tuned for anti-fighter combat, allowed them to overcome both with relative ease.
The Luftwaffe initially adapted to the U.S. fighters by modifying their tactics. Instead of approaching in small groups in ad-hoc formations, they instead formed up en masse in front of the bomber's line of approach, and then attacked by making a single pass through the formation. Flying in close formation with the bombers, the P-51s had little time to react before the attackers were already running out of range.
Fighting the Luftwaffe
Major General James Doolittle, the new commander of the 8th Air Force as 1944 started, told the fighters in the late winter of 1944 to stop flying in formation with the bombers and instead attack the Luftwaffe wherever it could be found, achieving a breakthrough in American fighter tactics. The Mustang groups were sent in well before the bombers in a "fighter sweep" as a form of air supremacy action, intercepting German fighters, be they the usual single-engined Bf 109Gs or Fw 190As, or the twin-engined Zerstörer heavy fighters like the Bf 110Gs, wherever they were found to be forming up. As a result, the Luftwaffe lost 17% of its fighter pilots in just over a week, and the Allies were able to establish air superiority. As Doolittle later noted, "Adolf Galland said that the day we took our fighters off the bombers and put them against the German fighters, that is, went from defensive to offensive, Germany lost the air war."
The Luftwaffe's answer, especially to their Zerstörer twin-engined bomber destroyer units' evisceration by the USAAF, was the Gefechtsverband (battle formation). It consisted of a Sturmgruppe of heavily armed and armored Fw 190 As escorted by two Begleitgruppen of light fighters, often Bf 109Gs, whose task was to keep the Mustangs away from the Sturmböcke Fw 190As attacking the bombers. This scheme was excellent in theory but difficult to apply in practice as the large German formation took a long time to assemble and was difficult to maneuver. It was often intercepted by the escorting P-51s using the newer "fighter sweep" tactics out ahead of the heavy bomber formations, breaking up the Gefechtsverband formations before reaching the bombers; when the Sturmgruppe was able to work as intended, the effects were devastating. With their engines and cockpits heavily armored, the Fw 190As attacked from astern and gun camera films show that these attacks were often pressed to within 100 yds (90 m).
While not always able to avoid contact with the escorts, the threat of mass attacks and later the "company front" (eight abreast) assaults by armored Sturmgruppe Fw 190s brought an urgency to attacking the Luftwaffe wherever it could be found, either in the air or on the ground. Beginning in late February 1944, 8th Air Force fighter units began systematic strafing attacks on German airfields with increasing frequency and intensity throughout the spring with the objective of gaining air supremacy over the Normandy battlefield. In general these were conducted by units returning from escort missions but, beginning in March, many groups also were assigned airfield attacks instead of bomber support. The P-51, particularly with the advent of the K-14 Gyro gunsight and the development of "Clobber Colleges" for the training of fighter pilots in fall 1944, was a decisive element in Allied countermeasures against the Jagdverbände.
The numerical superiority of the USAAF fighters, superb flying characteristics of the P-51, and pilot proficiency helped cripple the Luftwaffe's fighter force. As a result, the fighter threat to US, and later British, bombers was greatly diminished by July 1944. The RAF, long proponents of night bombing for protection, were able to re-open daylight bombing in 1944 as a result of the crippling of the Luftwaffe fighter arm. Reichsmarschall Hermann Göring, commander of the German Luftwaffe during the war, was quoted as saying, "When I saw Mustangs over Berlin, I knew the jig was up."
On 15 April 1944, VIII FC began Operation Jackpot, attacks on Luftwaffe fighter airfields. As the efficacy of these missions increased, the number of fighters at the German airbases fell to the point where they were no longer worthwhile targets. On 21 May, targets were expanded to include railways, locomotives and rolling stock used by the Germans to transport materiel and troops, in missions dubbed "Chattanooga". The P-51 excelled at this mission, although losses were much higher on strafing missions than in air-to-air combat, partially because, like other fighters using liquid-cooled engines, the Mustang's coolant system could be punctured by small arms, unlike the air-cooled Double Wasp radials of its Republic P-47 Thunderbolt stablemates based in England, regularly tasked with ground strafing missions.
Given the overwhelming Allied air superiority, the Luftwaffe put its effort into the development of aircraft of such high performance that they could operate with impunity, but which also made bomber attack much more difficult, merely from the flight velocities they achieved. Foremost among these were the Messerschmitt Me 163B point-defense rocket interceptors, which started their operations with JG 400 near the end of July 1944, and the longer-endurance Messerschmitt Me 262A jet fighter, first flying with the Gruppe-strength Kommando Nowotny unit by the end of September 1944. In action, the Me 163 proved to be more dangerous to the Luftwaffe than to the Allies and was never a serious threat. The Me 262A was a serious threat, but attacks on their airfields neutralized them. The pioneering Junkers Jumo 004 axial-flow jet engines of the Me 262As needed careful nursing by their pilots and these aircraft were particularly vulnerable during takeoff and landing. Lt. Chuck Yeager of the 357th Fighter Group was one of the first American pilots to shoot down an Me 262, which he caught during its landing approach. On 7 October 1944, Lt. Urban Drew of the 365th Fighter Group shot down two Me 262s that were taking off, while on the same day Lt. Col. Hubert Zemke, who had transferred to the Mustang equipped 479th Fighter Group, shot down what he thought was a Bf 109, only to have his gun camera film reveal that it may have been an Me 262. On 25 February 1945, Mustangs of the 55th Fighter Group surprised an entire Staffel of Me 262As at takeoff and destroyed six jets.
The Mustang also proved useful against the V-1s launched toward London. P-51B/Cs using 150 octane fuel were fast enough to catch the V-1 and operated in concert with shorter-range aircraft like advanced marks of the Supermarine Spitfire and Hawker Tempest.
By 8 May 1945, the 8th, 9th and 15th Air Force's P-51 groups claimed some 4,950 aircraft shot down (about half of all USAAF claims in the European theater, the most claimed by any Allied fighter in air-to-air combat) and 4,131 destroyed on the ground. Losses were about 2,520 aircraft. The 8th Air Force's 4th Fighter Group was the top-scoring fighter group in Europe, with 1,016 enemy aircraft claimed destroyed. This included 550 claimed in aerial combat and 466 on the ground.
In air combat, the top-scoring P-51 units (both of which exclusively flew Mustangs) were the 357th Fighter Group of the 8th Air Force with 565 air-to-air combat victories and the Ninth Air Force's 354th Fighter Group with 664, which made it one of the top scoring fighter groups. Martin Bowman reports that in the European Theater of Operations, Mustangs flew 213,873 sorties and lost 2,520 aircraft to all causes. The top Mustang ace was the USAAF's George Preddy, whose final tally stood at 26 and a third, 23 of which were scored with the P-51, when he was shot down and killed by friendly fire on Christmas Day 1944 during the Battle of the Bulge.
In China and Pacific Theater
In early 1945, P-51C, D and K variants also joined the Chinese Nationalist Air Force. These Mustangs were provided to the 3rd, 4th and 5th Fighter Groups and used to attack Japanese targets in occupied areas of China. The P-51 became the most capable fighter in China while the Imperial Japanese Army Air Force used the Nakajima Ki-84 Hayate against it.
The P-51 was a relative latecomer to the Pacific Theater. This was due largely to the need for the aircraft in Europe, although the P-38's twin-engine design was considered a safety advantage for long over-water flights. The first P-51s were deployed in the Far East later in 1944, operating in close-support and escort missions, as well as tactical photo reconnaissance. As the war in Europe wound down, the P-51 became more common: eventually, with the capture of Iwo Jima, it was able to be used as a bomber escort during Boeing B-29 Superfortress missions against the Japanese homeland.
The P-51 was often mistaken for the Japanese Kawasaki Ki-61 Hien in both China and Pacific because of its similar appearance.
Chief Naval Test Pilot and C.O. Captured Enemy Aircraft Flight Capt. Eric Brown, CBE, DSC, AFC, RN, tested the Mustang at RAE Farnborough in March 1944, and noted, "The Mustang was a good fighter and the best escort due to its incredible range, make no mistake about it. It was also the best American dogfighter. But the laminar flow wing fitted to the Mustang could be a little tricky. It could not by any means out-turn a Spitfire [sic]. No way. It had a good rate-of-roll, better than the Spitfire, so I would say the plusses to the Spitfire and the Mustang just about equate. If I were in a dogfight, I'd prefer to be flying the Spitfire. The problem was I wouldn't like to be in a dogfight near Berlin, because I could never get home to Britain in a Spitfire!"
The U.S Air Forces, Flight Test Engineering, assessed the Mustang B on 24 April 1944 "The rate of climb is good and the high speed in level flight is exceptionally good at all altitudes, from sea level to 40,000 feet. The airplane is very maneuverable with good controllability at indicated speeds to 400 MPH. The stability about all axes is good and the rate of roll is excellent, however, the radius of turn is fairly large for a fighter. The cockpit layout is excellent, but visibility is poor on the ground and only fair in level flight."
Kurt Bühligen, the third-highest scoring German fighter pilot of World War II's Western Front (with 112 confirmed victories, three against Mustangs), later stated, "We would out-turn the P-51 and the other American fighters, with the Bf 109 or the FW 190. Their turn rate was about the same. The P-51 was faster than us but our munitions and cannon were better."
"My final year in high school, I convinced myself that, above all else, I wanted to become an artist, and started a vigorous inquiry into every school of art within a thousand miles of my hometown Pittsburgh," Biederman wrote in his autobiography, published in the November-December 1970 issue of Horseless Carriage Gazette. He attended the American Academy of Art in Chicago. "The only entrance requirement consisted of artistic proof of one's ability, so I prepared a complete catalog featuring an imaginary automobile. Each page portrayed a separate model, each laboriously rendered in profile, all in full and glorious color. When this massive document was finally lashed together, it possessed all the weight and characteristics of a suitcase loaded with bricks. Thus, for better or worse, my artistic career was launched."
Biederman graduated from the Academy in October 1932, and like many of his contemporaries, the rigors of the Depression meant that it took him three years to find a job in his field. "My introduction to the advertising world was a revelation akin to the opening of 1,000 doors," he wrote. "Such mysteries as art direction, layout, production, type, reproduction-all unfolded in rapid succession...I survived this routine for years, but slowly and inevitably had begun the realization that the artist must at some time look to specialization and away from generalization in order that he might achieve recognition, prominence, and even fame. In 1940, I departed the advertising affair for the calmer atmosphere of a studio.
"I turned my full attention and energies to transportation vehicles...on/in the water, air and land," he continued. "Movement in its various forms has dominated my time, my thinking, and my life these past thirty years. In the years that followed, I did become known and my particular specialty recognized, but many detours were necessary, including art directorships, freelance artist, etc. As my exhibits became more numerous and my sells more regular, exposure of my efforts began to enter into commercial channels...calendars, prints, premiums, novelties, magazines, as well as other channels."
As Biederman's expanding body of work was gaining him prominence, he began a relationship with the McCleery-Cumming Corporation in 1956; this calendar company retained the artist to create six paintings for each of their 1958 automobile calendars. He painted for the calendar company for 36 years, and in the first 31 of those years, 186 automobile paintings were printed without interruption. A total of 444 Biederman transportation paintings were published in McCleery-Cumming calendars by 1993. In addition to the calendars, Mr. Biederman's automotive paintings were featured prominently in Playboy magazine, Automobile Quarterly and Horseless Carriage Gazette. He retired at the age of 75, in 1988, and died in 1996.
According to his widow, most of Biederman's paintings were done in tempera on heavyweight 20 x 30-inch illustration board. Calendar art averaged roughly 10 x 15 inches, depending on the subject. A substantial portion of Biederman's body of work remains intact, and most originals are available for purchase at $1,200 apiece.
"It seems to me that despite the untold millions of devotees adherent to this, that and the other...the fundamental 'love affair' lies in and with the internal combustion engine, the good, bad or indifferent that surrounds it," Biederman wrote. "The combination of motor, wheels and body, has known, knows, and will experience moments of greatness, be they in performance, styling, concept, even flights of fancy."