USA (1943)
Fighter Aircraft – 3,738 Built

 

Initially developed to provide an export alternative to the P-40 for France and the UK, North American’s P-51 would prove to be a superb aircraft that would rank among the most decisive weapons of the Second World War. With its streamlined airframe and highly efficient cooling system, the aircraft would reach new heights when equipped with the far more advanced Packard Merlin engine. Though its early years would prove troublesome, it would solve long standing issues regarding the lack of long range bomber escorts, and achieve a level of performance beyond its Axis contemporaries.

Interwar Fighter Developments

The Merlin powered P-51’s share the distinction of being among the most successful fighter aircraft ever developed, but also having one of the convoluted development paths of any mass production fighter. While the aircraft would make its first flights in 1943, it had its roots in the late interwar period where many of the technologies it incorporated were first established.

The general environment of interwar fighter development for the US Army Air Corps was one of high theoretical advancement, but comparatively slow practical development. While major milestones were made in regards airframe and powerplant design, there was considerably less urgency to develop and mass produce fighters for use by the Air Corps. This was mostly a result of an isolationist foreign policy, which limited availible resources, and to a lesser degree, a desire within the Air Corps to focus on bomber procurement. While the development of new fighters was limited, the Air Corps had great freedom in procuring aircraft for testing purposes. While funding was still limited, they were allowed to procure up to 14 examples of an aircraft through their budget before they would need to petition Congress for additional funding. While a large build up of the Air Corps during this period was a financial and political impossibility, it would prove sufficient for exploring aircraft design and development. This environment would exist into the late 1930’s as the political situations in both Europe and Asia destabilized, and subsequently, the order was given to continue the development of the XP-38, XP-39, and XP-40 into new fighters for use with the Air Corps (Ethell 9).

While these aircraft were being prepared for service, vital new developments were being made in regards to airframe design. At the National Advisory Committee for Aeronautics (NACA) offices at Langley field, efforts had been made to produce airfoils which could achieve laminar flow. In short, this effect is characterized by minimal disruptions to the airflow of the surfaces of the wings and adjoining fuselage. In the context of fighter aircraft, this allowed for a much lower drag coefficient, which would permit better acceleration and would lessen the instability encountered at higher Mach numbers. They would achieve this by June of 1938 when an airfoil displayed laminar flow characteristics in wind tunnel tests (Ethell 10).

Europe Ablaze

The escalation to and the outbreak of hostilities in Europe would completely dispense with the interwar malaise and saw the US begin a massive arms build up. The most notable shift in policy was President Franklin Delano Roosevelt’s call for 50,000 aircraft in January of 1940. The resulting surge of orders would end up leaving most US aircraft manufacturers at capacity, and though they would satisfy domestic demand, the fulfillment of export orders was not a priority. This represented a serious issue facing the Allies in Europe. At the outbreak of the war, the French and British air forces were still largely in the process of expanding and modernizing. While they both possessed examples of modern fighter aircraft, such as the Dewoitine D.520 and Supermarine Spitfire Mk.I’s respectively, they also employed a large number of outdated aircraft in comparison to the better equipped German Luftwaffe. The expedient solution to this problem seemed to be to purchase aircraft abroad, and the US was by far the best source.

To this end British and French interests were served by the British Purchasing Commission. While they had decided on the ideal candidate being the Curtis-Wright P-40, they found the at-capacity firm unwilling to compromise its contracts to the US Army. They were soon negotiating with other firms for P-40’s which would be manufactured under license, and by 1940 had placed as many orders as they could. It was clear to all parties involved that any of the larger firms that were involved in US rearmament would be unable to deliver any sizable number of aircraft to the Allies. In January of 1940, Oliver Echols, in charge of Air Corps procurement, would suggest to the Purchasing Commission to approach a manufacturer that lacked any major contracts involved with US rearmament (Ethell 10).

This suggestion would see the British Purchasing commission returning to older offers from firms that they had turned down the previous year. The most important of these would be North American Aviation. North American had earlier proposed to build P-40’s under license for the Allies, though the offer was given little consideration (Ethell 10). They were likely turned down over their relative inexperience in the field of fighter aircraft, having previously built advanced trainers, like the AT-6 Texan, and the crude NA-50 and NA-68 export fighters. In spite of this, and finding few options among other US aircraft manufacturers, the British Purchasing commission would once again approach North American. This time however, North American was given the option to either produce license-built P-40’s, or instead to design a new aircraft with the aid of research data acquired from Curtiss-Wright on the XP-46 fighter prototype. NAA’s small, but enthusiastic team would choose the latter, and prepared to design a new fighter built around the Alison V-1710 engine.

Enter North American

By the standard’s of most US industries of the time, North American Aircraft was a fledgling company, though one with great promise. It was originally formed as a holding company in 1929 to purchase stock in other aviation concerns, and was later incorporated under General Motors’ General Aviation branch. As a holding company, North American would gather a considerable amount of resources in these early years, of particular note was the firm’s acquisition of Fokker. In 1934, as a result of new regulations on air mail carriers, General Motors was required to divest itself of North American, which then became an independent firm. Thereafter, North American incorporated its parent company, General Aviation, and continued under the direction of its president James H. ‘Dutch’ Kindelberger (O’Leary 9). He would subsequently take the company west in 1936 where they would open a new facility at Mines Field, California. Prior to the war they would develop the O-47 reconnaissance and observation aircraft, which had begun under General Aviation, and the AT-6 advanced trainer, which was among the most successful designs of its type. They would also produce a set of unsuccessful export fighters which were altogether unimpressive. With this in mind it’s understandable North American was initially passed over, they were in fact, inexperienced in fighter development and their only real foray into that field was a disappointment. However, when the British Purchasing commission returned to the company in 1940, they found the firm more than ready to meet their needs. Their contract was worked out for 400 planes at a price no higher than $40,000 dollars a unit, and spare parts in the amount of 20% of the value of the aircraft.

The first step in developing the new fighter was purchasing the most recent data on fighter design from Curtiss-Wright’s XP-40 and XP-46 prototypes, and acquiring the new breakthrough aerofoil designs recently developed under NACA (Ethell 10, 11). This information was made available to the design team headed by Edgar Schmued, a German born aeronautical engineer who had previously been a GM field service manager for their Brazil branch. The work soon began on a new fighter under the designation NA-50B, later changed to NA-73, under a common and straightforward design strategy. Schmued would work to build a plane that would excel by incorporating all of the most recent developments in fighter design to produce an aircraft that was both cutting edge, yet conventional (Douglas 252). The Curtiss-Wright prototypes were a starting point that was quickly surpassed, with engineer and aerodynamicist Ed Horkey considering the prototypes too dated for use on the new project, and the data was discarded (Forsyth 13). This came as somewhat of a blow considering they were forced to pay about $50,000 for the test data. The same cannot be said for the data acquired from NACA.

Horkey would come across NACA’s research through a confidential release for American industrial use, and was convinced that it would make an excellent addition to the new fighter’s design. NAA would send a representative to collect the data from NACA at Langley Field, and they would go on to receive minor technical support. While the design did not possess true laminar flow characteristics, it did drastically reduce drag and improve the performance of the aircraft (Ethell 11). Further streamlining was achieved through the mounting of a low drag, centerline radiator which incorporated the work of British scientist, Dr. F.W. Meredith. This divergent-convergent duct was capable of using the heat ejected by the radiator to actually produce thrust and offset some of the speed loss incurred by drag incurred by the radiator’s air scoop (Douglas 252).

 

Great care was taken to build the prototype in good time. The NA-73X, would make use of a number of components from North American’s AT-6 trainer, including its landing gear, hydraulics, and electrical systems. Remarkably, the construction of the prototype was completed on the 102nd day of the project, but it would have to wait another 20 days for its Allison V-1710-39/F3R engine (Marshall & Ford 94). The supply of Allison engines at the time was constrained, and resulted in the project having to delay its deliveries to the British. Despite this, the fast pace of the program, and the fall of France would see the British order another 320 aircraft before the prototype even flew. With the program approaching testing, the British were awaiting the results and readying their own test pilots to become acquainted with the new plane. The prototype was first flown by American test pilot Vance Breese on the 20th of October, 1940. It would go on to make several more test flights before having to be repaired after an accident with test pilot Paul Balfour. The accident was a result of pilot error, who failed to switch over from an empty fuel tank, and as such the incident did not reflect poorly on the design itself (Marshall & Ford 151). As the sleek new fighter was taking shape, the British Purchasing Commission would notify NAA that the aircraft’s RAF designation was to be the ‘Mustang’ in a communique sent in December 1940 (O’Leary 24).

Among the last modifications to the NA-73 regarded its armament, fuel capacity, and reinforcement of its wings. Several proposals for its armament were considered, but for the British Mustang they installed a pair of .50 caliber guns in the nose cowling with another two .30 caliber guns in each wing. With these last additions made, the British soon received several of the new aircraft, which now bore the more familiar title of Mustang. The first, AG345, would be put through tests to find any issues from the transition from the NA-73. Several issues arose over the stiffness in the ailerons, power surges in dives, and overheating. These were subsequently addressed, though more drastic changes were needed in the case of the engine, which required installing a new carburetor scoop, and altering the scoop for the radiator (Marshall & Ford 165). The culmination of these new changes would result in the finalized Mustang Mk.I, and a second development prototype, NA-83.

While the aircraft’s development was proceeding at a rapid pace for the British, the USAAC would show very little initial interest in the Mustang. The aircraft the USAAC had dubbed the XP-51 was largely overshadowed by other developments and comparatively little effort was made to conduct exhaustive tests on the XP-51 prototypes at Wright Field to correct their faults. Their interest in the aircraft would be piqued only after the U.S. entrance into the second World War.

Mustang Mk. I

In British service the Mustang would take a different developmental path than what was proceeding in the United States. While the British were receiving their Mustang fighter aircraft, the US had been forced to develop the aircraft into a dive bomber, the A-36, as funds for fighter development had been expended for 1942. In the case of the RAF, the Mustang Mk. I went into service as soon as was practicable and saw their first squadrons, numbers 161 and 613, receive supplies of the new aircraft in April of 1942. They would first be employed as reconnaissance aircraft before later taking on more dangerous work during Operation Jubilee in which they undertook offensive recon sorties over the raid area in Dieppe, France. Beyond this they would be subsequently used to fly nuisance raids and fighter sweeps across the low countries. Its long range, high speed, and effective armament were used to great effect over these areas as they harassed rail and road communications, while also remaining quite capable against enemy fighters wherever they were encountered (Ethell 24, 25). Even by this early mark, the once uncertain contract they signed with North American had already paid off.

It was during this period that the aircraft’s faults and strengths would make themselves evident. The nose mounted guns were troublesome and complicated maintenance; they were often removed from operational planes and were eliminated from the succeeding models of the aircraft. The radiator still presented teething issues, as under certain conditions the oil could freeze over and would fail to circulate, and eventually cause the radiator to boil over. Visibility too would become an issue, as the canopy frame of the cockpit severely restricted the pilot’s view. However despite its faults, the plane was fast, possessing good acceleration and a high top speed that made it capable of outrunning all fighters in the theater at sea level (Ethell 24).

While the radiator issues would be addressed and a new bubble canopy was developed, another, more serious drawback of the design would require far more resources to address. The Allison engines that the early Mustangs were equipped with were considerably lacking when it came to high altitude performance due to their single stage, single speed superchargers. While the aircraft received good marks for its low altitude performance from pilots in the RAF, above the 15,000ft the Allison V-1710 suffered considerable power loss. Though this was by no means surprising, it represented an area where performance could be significantly improved. At higher altitudes the aircraft was outpaced by both contemporary models of the Fw 190 and Bf 109. At low altitudes, it was made somewhat redundant by the RAF’s new Hawker Typhoon, which both flew faster at low altitudes and was better armed. It wasn’t long until the idea arose to fit the Mustang with an engine possessing better high altitude performance, a combination that might well produce an exceptional fighter that was as capable at high altitude as it was down low (Douglas 253).

The first major step toward this came on April 29, 1942, when Wing Commander Ian Campbell-Orde invited one of Rolls Royce’s test pilots, Ronald W. Harker, to test the new aircraft. Harker was impressed by its performance and he believed that if the aircraft was fitted with the new Merlin 61, it would be able to outpace a similarly equipped Spitfire by a considerable margin (Marshall & Ford 215). The Merlin 61 was the obvious choice for many reasons, chief of which was its two stage, two speed supercharger which stood to offer the plane exceptional high altitude performance. To this end, a Mustang Mk.I was provided to Rolls Royce at Hucknall to undergo the necessary modifications. By the beginning of June 1942, the British had correctly projected that the Mustang’s top speed would be increased to 430mph at an altitude of 25,000ft, which was roughly twice as fast as the Allison powered Mustang at that altitude (Douglas 254). When the test aircraft was complete the results were quite impressive, as during a fly off between a Spitfire Mk. IX and a Mustang, both fitted with Merlin 61’s, the Mustang quickly outpaced the Spitfire.

Across the Atlantic, a parallel development began underway after a study of the Mustang’s combat debut with the RAF. The new United States Army Air Force, no longer constrained by funding, rushed to acquire supplies of the Mustang, and sought to re-engine the fighter to improve its high altitude performance. To this end, two P-51’s were set aside for conversion. By the early half of the Summer of 1942, both British and American Mustang experiments were underway. While the Mustang was previously seen as a side project which was never a wholly American or British effort, it was by then extremely clear that the design had tremendous potential and the development of which was of immense importance to the Allies.

Shoeing the Mustang

Re-engining the Mustang was by no means an easy task, as the Merlin was considerably heavier than the Allison and required a larger cooling system. To achieve this, the radiator was reworked, with the oil cooler moved apart from the radiator matrix to a forward position, and the ducting of the entire scoop assembly being redesigned. Earlier aerodynamic and buffeting issues caused by the radiator intake were also resolved by moving the scoop out of the boundary layer under the fuselage. The resulting set up would also achieve the earlier described Meredith effect, which produced thrust that offset the drag caused by the scoop (Marshal & Ford 97, 219). Additionally, the carburetor’s intake duct was moved beneath the nose which also necessitated lowering the wing to accommodate the lower cowl.

In addition to higher cooling requirements, the new Merlin engine weighed 350lbs more than the Allison and would mount a larger, heavier propeller, which would represent a significant shift in weight. To compensate, 61lbs of ballast was added, the primary fuselage longerons were strengthened, and the wings were strengthened and moved lower and forward. These changes would also help to compensate for the stronger vortex generated by the propeller and the greater forces generated by the improved ailerons (Marshall & Ford 219). The new engine and the subsequent operations would also result in some yaw instability. Adding a fin ahead of the horizontal stabilizer seemed an adequate solution, but it would not be undertaken until far later.

While the testing for most of these modifications was done through a variety of converted air frames, the prototype that brought them all together was the XP-51B, which first flew on October 1, 1942. The importance placed on this aircraft was considerable, as several months prior, a large order for 1200 P-51A’s was placed by the US government on the provision that their production could be switched for P-51B’s, given advanced notice (Marshall & Ford 230).

The XP-51B would prove promising but it was troubled by radiator issues which would remain with the aircraft through January of 1943. These were tracked down to a chemical reaction which was found to be degrading the coolant tubes, and was resolved by a lacquer liner. There were also air flow issues within the radiator, which were solved through moving its aftercooler core to improve airflow through the scoop. The prototype’s last major issue was the tendency for its air scoop to produce loud, and worrying, vibrations at high speed. Resolving the problem once again required them to change the geometry of the scoop (Marshall & Ford 258, 311). This was solved by the aforementioned modification that moved it out of the boundary layer below the wing, and further improved as the depth of the gutter was increased and the inlet size was reduced (Matthews 7).

All of the production models of the Merlin powered P-51’s would fly with engines produced under license by Packard. It was a matter of good fortune that Packard was already engaged in the mass production of their version of the Merlin engine prior to the demand for the engine for the new Mustangs. Packard had built its first V-1650-1’s, a license built Merlin 28, in August of 1941 which were later destined for use in Canadian built Avro Lancasters, DeHavilland Mosquitos, and the updated Curtis Wright P-40F (Marshall & Ford 176). Changing production to suit the needs of the P-51B would however not be easy, and matters were made worse by a general strike at the main plant which, alongside slow development at Wright Field, made for considerable delays. Some of the supply issues would be addressed as the new Mustangs would receive the first priority in terms of supplies, superseding the P-40F and L, and denying its use on the P-38. However, beyond these were the predictable teething troubles, and combined with the less predictable hurdles, they saw widespread deployment of the P-51B delayed considerably. Packard would go on to supply North American with engines, however they would never fully be able to meet the massive demands of both the United States and Great Britain (Marshall & Ford 347).

My Kingdom for a Horse

While development on the Merlin powered P-51’s proceeded, the USAAF had formulated and launched a strategic bombing campaign dedicated to destroying industries vital to the German war effort. The theoretical foundations of this strategy had been set in the interwar era and were initially seen as a means to expand the Army Air Corps into a force with greater autonomy. Many early interwar theorists, such as Maj. Harold George, would describe a vague ‘economic web’ that could be destroyed and force an industrial and morale collapse, but in 1943 these theories were put to the test. The practical details of the campaign were laid out at the Allied conference at Casablanca. There a series of targets was decided upon, but later altered to a plan that favored targeting aircraft and submarine production, in addition to ball bearing plants (Overy 45, 305). However, the main concern for USAAF bombing operations was that thus far, all daylight strategic bombing campaigns had ended in failure after formations of unescorted bombers were shredded by fighters.

Since before the war, it was commonly believed among the Air Corps senior officers that a formation of well armed bombers was capable of defending itself from whatever threats it might face. This assertion would be disproven, as even the small raids against targets in France and the low countries sustained casualties that made consistent raids impossible. In early 1943, the next step of the campaign would be far more ambitious, moving on to targets deeper within Germany itself. The need for a long range escort fighter had already become apparent before this point, and work was underway to produce external fuel tanks for existing fighters, but the offensive would be continued without a fighter aircraft able to accompany raiders for the full duration of their missions.

Throughout the summer and autumn of 1943, the USAAF would launch numerous raids against targets in Western Germany, though the bombers could only be escorted over the low countries by P-47’s and P-38’s. It wasn’t long until these range limitations were understood, and soon after, exploited by the Luftwaffe. Wherever Luftwaffe fighters were untroubled by Allied fighters, they were free to make use of their most effective anti-bomber tactics.

Generalmajor Adolf Galland’s prescribed method of attack for single engine fighters was to make head on, or oblique, attacks from slightly above the bomber formation, carried out by at least a Schwarm, or two pairs of fighters (Marshall & Ford 267). This achieved two things, it increased the closure rate to reduce the likelihood of being hit by defensive gunners, and it was from this position that both the pilot and copilot of the bomber were most vulnerable. In the absence of escort fighters, Luftwaffe pilots would be able to regroup, fly ahead of the formation, climb, and repeat the attack. The lack of escort fighters also meant the Luftwaffe was safe to employ its two engined fighters against bomber formations, which with their heavier armaments, were much better equipped to bring down bombers. Over time their tactics grew even more complex as dedicated aircraft, typically Ju 88’s, were tasked with shadowing bomber formations to pass their altitude, course, and speed to flak and fighter control services.

Prior to the arrival of the P-51’s, the USAAF had two suitable fighters for the purposes of escorting bombers at high altitude, the P-38 and P-47. While they had the high altitude performance, they did not have the range to reach deep into the continent. The issue would be partially resolved through the addition of external fuel tanks, which had been discussed at a conference with the Material Division at Wright Field in March of 1942 (Ethel 51). Work however, was slow and the 108 and 75 gallon drop tanks were not delivered in large numbers until the end of summer, 1943.  These tanks would allow the shorter ranged P-47 to be able to cover bombers over their flight over the low countries, and the P-38, over the Rhineland. It should also be noted that the escort range was considerably lower than the maximum combat range of the aircraft, as the planes flew in a zig-zag pattern overhead so as not to out pace the bombers. Supplies of larger volume fuel tanks which would take the fighters further into German air space would not be available until the spring of the following year. External fuel tank development and procurement had been mismanaged by Army Air Force leadership who were still largely convinced that the bomber’s defensive capabilities were adequate. Had there been a greater supply, and larger volume tanks initially available, the P-47 and P-38 could have escorted bombers over most of Germany. To make matters worse, the P-38, which by then handled the most important leg of the trip, was troubled by a number of technical issues. While the P-38 possessed good high altitude performance, an exceptional climb rate, and a heavy armament, it was handicapped by a cockpit that pilot’s rated the worst of any US fighter in service and had flying characteristics that made it difficult for pilots to aggressively pursue Luftwaffe aircraft (Dean 164). The large, twin engine Lightning also had an unmistakable appearance, such that Luftwaffe pilots would almost always spot and identify the Allied plane before Lightning pilots could do likewise. With this benefit, Luftwaffe pilots were typically the ones who dictated the engagement, and would depart when conditions were unfavorable. On the defense they would have another advantage, both the Fw 190A and the Bf 109G were capable of out maneuvering the P-38 in high speed dives. The P-38 encountered severe compressibility issues at speeds significantly lower than those encountered on the two German fighters (Marshall & Ford 441). Thus, while the P-38 was capable of performing long range escort missions, its pilots would be forced to employ more conservative tactics than those used in the P-47.

By the start Autumn of 1943, USAAF planners were hoping to accelerate their progress on Operation Pointblank. This plan would see bombers raid targets that were vital to the German aviation industry in order to achieve air supremacy over Western Europe before an invasion of the continent. While losses for these raids were still extremely high, it was hoped that dispatching a larger force capable of inflicting serious damage would make it worth it. On August the 17th, the 8th Air Force prepared for its largest raid yet, with 376 B-17’s dispatched to attack the ball bearing works, at Schweinfurt, and a Messerschmitt factory, at Regensburg. Both of these facilities were located deep within Germany and most of the journey would see the B-17’s outside the area where they could be escorted. To compensate for this, the flight over Regensburg would continue over the Alps and into Allied controlled Tunisia. It was hoped that flight over the Alps would prove easy, and in the case of the Schweinfurt force, they believed that the German fighter squadrons would still be on the ground refueling after their first attacks while the bombers made their return. Both would be met with disaster as the Luftwaffe would hit both forces after their escort fighters turned for home, and the Luftwaffe fighters had taken to the air again as the Schweinfurt raiders made the return trip.

Of the 376 bombers to leave England, 60 would be shot down, 176 were damaged, and 30 remained in North Africa where they awaited repairs at the overburdened facilities in Tunisia. Losses in combat and written off airframes amounted to 31% of the dispatched force; in contrast the Germans lost only 28 fighters (Overy 340, 341). Following the disaster, the 8th Air Force would carry out raids only where there was full escort cover and the next deep incursion into German airspace would only be conducted in the spring of the following year. The winter of 1943 would spell uncertainty for the campaign, as it was clear that for all intents and purposes, much of German industry lay beyond striking range. With this limitation threatening to seriously cut back the USAAF’s campaign, they would request that Lockheed, Republic, and North American increase the internal fuel capacity of their fighters, and hoped that a suitable long range escort would materialize.

Leaving the Stable

As a result of the pressure to produce new, long range fighters for the escalating campaign in Europe, the first P-51B’s were produced before the prototype had gone through its testing and modification cycles. The first plane, a P-51B-1, was completed March 31, 1943 and would include several features that would later be found unsound on prototype. As a result, these initial planes would have to be altered accordingly and would have many parts that were non-interchangeable with later models (Marshall & Ford 316). In addition to reworking the air scoop and radiator, they would also have their ailerons modified, both to improve their effectiveness and to remove a steel diaphragm which would interfere with the plane’s magnetic compass. Most importantly, the decision was made that the aircraft would incorporate an additional 85 gallon fuselage fuel tank which would provide the aircraft with phenomenal range.

With this new aircraft, the USAAF would finally possess what they had been searching for. With the addition of the new internal fuel tank, the aircraft would be capable of deep incursions into German airspace, and it would deliver on what was promised back in the spring of 1942. They were excellent fighters, especially at high altitude. The early P-51B’s would use the Packard V-1650-3 engine, a license production of the British Merlin 61, which produced 1410 hp at 29,300 ft and 1630 hp at 16,400ft at War Emergency Power (P-51 operation manual 31). This engine would later be replaced with the Packard V-1650-7 in later models of the aircraft, which was geared for better performance at medium altitude. These engines, combined with the low drag fuselage and laminar designed wings would provide the aircraft with a superb climb rate, a high top speed at altitude, and exceptional high speed maneuverability.

While the aircraft had taken a largely completed form with the P-51B-5 and P-51C-1, it would be continuously modified in the field and on the production line, throughout its service with the air force. The most notable of these changes were the additions of a fuselage tank, booster motors for its ammunition belts, a vertical fin extension, and field retrofits for a perspex canopy dubbed the Malcom Hood. However, only the 85 gallon fuel tank would be a universal addition.

The fuselage tank would enable the P-51B’s to reach much of central Europe from England, but it was not present in the first deliveries of the aircraft, as was the case with the 59 P-51B’s active in England at the end of November 1943. The installation kits were first sent out in September of 1943, and the tank was later incorporated into the production run with the first long range P-51B being accepted by the Army in December of the same year (Marshall & Ford 393, 407).

The next addition to the aircraft was intended to solve a major issue with the plane’s machine guns, which were found to be prone to jamming when the pilot pulled turns of over 1g. This issue was a result of the canted position of the guns in the wings which put stress on the ammunition belts. The ideal solution was to reposition the guns, but seeing as that would necessitate a considerable redesign, engineers would instead work in a stop gap measure in the form of boost motors for the ammunition belts. These were issued as kits like the fuel tank, though unlike those for the fuselage fuel tank, they were issued in more limited numbers and the issue persisted well into 1944 (Ethell 64).

The Mustang had long had a tendency to yaw in the opposite direction of a roll, which affected its handling since its earliest models, and this was made significantly worse when fuel was carried in the fuselage tank. Despite the problem being an evident and considerable inconvenience, its solution wouldn’t materialize until much later. Eventually, it was decided to fit the aircraft with a fin extending from its vertical stabilizer, along with adding reverse rudder boost tabs. However, these kits arrived very late, having begun production in April of 1944, and later incorporated into the design of late P-51C’s and the subsequent P-51D (Marshall & Ford 306).

Many long standing issues revolved around the ‘birdcage’ canopy of P-51 since the aircraft’s inception, and as was the case with the engine, an improvement was found in British service. With the RAF, many Mustangs received a new frameless bubble canopy. This canopy vastly improved visibility, especially to the rear of the aircraft, which was virtually non-existent from within the birdcage, and it could be drawn back on landing and take-off. Dubbed ‘Malcom Hoods’ after their manufacturer, a plexiglas works named Robert Malcom Ltd. they were subsequently sought after by the USAAF for use with their P-51’s in Europe.

Breaking the Stalemate

The new P-51B’s would make their first major debut with the 8th Air Force in early 1944, though the introduction was not as smooth as had been hoped. Squadrons reported a number of issues with the new aircraft, which included high altitude fuel transfer failures with external tanks, glycol reserve tanks that leaked and froze, radiator corrosion and coolant leaks, radios and spark plugs failing, and excessive oil loss (Marshall & Ford 425). However the USAAF hadn’t the time to immediately resolve these teething issues, and with these problems passed along to the manufacturer and Air Force maintenance services, the P-51’s would soon play a key role in the escalating bomber offensive.

Through the winter of 1943, both the day and night bombing campaigns were facing withering losses which spelled serious trouble for maintaining the pace of operations over Europe. With less than one thousand bombers stationed in England, the USAAF would lose 200 in September alone (Douglas 326). In the face of these losses, the Combined Bomber Offensive was failing to carry out the Pointblank directive, which aimed to cripple the Luftwaffe before an invasion of Europe was conducted. During this period the Luftwaffe had actually built up the strength of its fighter force and had reorganized and improved its defenses into a centralized command structure. To make matters worse, the head of RAF’s Bomber Command, Arthur Harris, would ignore orders to attack German industries involved in aircraft production. Instead, he would order Bomber Command to continue to carry out an ineffective area bombing campaign of Germany’s cities believing it would bring an end to the war without the need for an invasion (Overy 343, 344). It was under these bleak circumstances that the US’s Eighth and Fifteenth Airforces were tasked to cripple the Luftwaffe and establish air superiority over much of Europe before the invasion, now only a few months away. However, they would soon see a change in leadership and the delivery of new equipment that would put them on the path to controlling the skies over Europe.

In December of 1943, the USAAF established a joint strategic air command to consolidate their bomber forces over both the European and Mediterranean theaters, and drive them towards a unified objective. With Gen. Spaatz in command of all strategic bomber forces, and Maj. Gen. James Doolittle in command of the Eighth Airforce in England, the USAAF would now have clear strategic direction, and more aggressive leadership. Doolittle would take a pivotal role in revising the existing strategy into one which proved instrumental in undermining, and dismantling the Luftwaffe in the coming weeks. Crucially, he recognized the inadequacy in trying to undermine the Luftwaffe’s fighter strength solely through targeting the production of new aircraft. To hold to this existing, overly conservative strategy was hopeless, and the invasion of France was scheduled for five months after he took office. Targeting the factories alone wasn’t enough, and thus Doolittle would give the order for returning escort fighters to perform fighter sweeps and seek out enemy planes in the air and on the ground (Overy 361). Among the first and most important moves was to create a more effective relay system for the fighters, further increasing the time they could spend over enemy territory.

By the start of 1944, Maj. Gen. Kepner, 8th Air Force, would also play a major role in implementing this new strategy, as he officially untethered the Eighth’s fighters from the bombers and allowed them to seek out the enemy at their discretion. The P-51 would play a pivotal role, as its excellent high altitude performance and range meant it was able to take up the last position of the fighter relay, and was more than a match for whatever it found. Beyond the existing penetration, target, and withdrawal relay positions, the P-51 was also able to take up a fourth mission. These units would perform sweeps 50 to 70 miles ahead of the bomber formation and attack German fighters as they were climbing, assembling, or transiting towards the bomber formation. Their efforts were greatly aided by British signals intelligence services that provided the assembly points for the Luftwaffe’s fighter groups (Marshall & Ford 425, 425; Overy 362).

This change in tactics would have immediate and profound impacts as they began to be widely implemented in February and March of 1944. The first major achievement of the new strategy were the widespread losses inflicted on the twin engined fighter forces, which had earlier proven themselves as potent anti-bomber weapons. Against the new long range fighters, they were almost defenseless, and were withdrawn in March (Overy 366). Similar effects were felt throughout the Luftwaffe’s fighter forces, which thanks to the new P-51’s, were left without any safe haven. Whenever the bombers were over Germany, their escort fighters could make their appearance. While the new strategy often meant that the bomber formations were often less protected, this was counterbalanced in that it placed the German fighters on a defensive footing. The days of Luftwaffe fighters leisurely climbing alongside a formation before diving at it head on were over, now whenever they reached a formation they were forced to conduct hit and run attacks, or face off against the escorts.

Luftwaffe attrition escalated as airfields that were once ignored were now periodically harassed by fighters that attacked transiting and grounded aircraft. Doolittle did all he could to promote these attacks, and would allow for the destruction of aircraft on the ground to count towards a pilot’s ace status (Marshall & Ford 423). These attacks would prove costly to the USAAF, but well worth it as Luftwaffe operational losses for all aircraft increased sharply and it robbed them of the ability to train new pilots in secure airspace. This shift in strategy and subsequent success would prove instrumental to the USAAF in the following months, as their responsibilities were soon to broaden when the Allies landed in France.

While the Eight and Fifteenth air forces were still occupied with the task of destroying the Luftwaffe in the air and on the ground, they would soon be given additional missions. The most unexpected of which came in the form of Operation Crossbow, which called upon the Eighth Air Force to disrupt Germany’s use of the new V-1 bomb from coastal bases. Then came the task long awaited, which called upon the Eighth to begin the preparations for Operation Overlord. To meet these new objectives, the Pointblank raids were accelerated, culminating in ‘Big Week’ in February of 1944.

Between the 19th and the 26th, the Eighth and Fifteenth air forces would fly roughly 6,200 sorties against 18 aircraft assembly plants and two ball bearings plants, at a loss of 247 bombers and 28 fighters. Undoubtedly steep, but sustainable in comparison to the Luftwaffe which lost roughly one third of its single engine fighters (Overy 369). The success of the raids themselves was difficult to judge, as fighter production still increased, though at a significantly reduced rate which saw a shortfall of roughly 38.5 percent (Overy 370). During these operations the P-51 would provide the USAAF deep penetration cover and perform strafing attacks against German airfields. However, there weren’t enough long range escorts for full coverage until the summer of 1944. The situation was further complicated when all P-51B’s were grounded between the 10th through the 15th of March in order to address structural issues with the aircraft’s engine mounts, wings, and tail. These were subsequently resolved by replacing the retaining bolts for the engine, reinforcing the tail empennage and ammunition doors, and installing landing gear locks to prevent their uncontrolled release at high speed (Marshall & Ford 442, 446). These issues would however not present a long term obstacle during the early months of 1944 as the tempo of operations and list of targets grew in the following months.

With the major push against the German aviation industry mostly over, the USAAF would soon set its sights on two major targets, rail communications across much of Northwestern Europe, and Germany’s oil industries. The first was an immediate necessity for the success of Operation Overlord, crippling German strategic mobility was essential for an invasion which would require considerable time after the first landings to build up a force on the continent. The formalities were worked out in March when the Transportation Plan was decided upon. It would fortunately have the support of RAF Bomber Command, as Harris’s evident failure to end the war on his terms would see him temporarily divert his force into supporting the preparations for the invasion of France. The subsequent offensive against fuel production would start far less formally. Spaatz was convinced of its necessity, but due to the months it would need to take effect, he was at first unable to convince his superiors to divert resources to it. However, in a matter of weeks, he was able to argue for its necessity under the Pointblank Directive and was then allowed to conduct attacks against Germany’s synthetic fuel industry whenever resources permitted (Overy 371).

With these new policies in place, the Luftwaffe would be thoroughly disrupted as a result of Spaatz’s strategy, and Doolittle and Kepner’s tactics. The USAAF would end up inflicting punishing losses on the Luftwaffe in the air, disrupting the manufacturing of new aircraft, and eventually causing chronic fuel shortages that severely limited their ability to conduct large scale operations of any kind. In this, the P-51 would prove essential with its exceptional high altitude performance, and its endurance that could take it anywhere over Germany.

In many ways, the bombing of factories alone was a largely ineffective means of inflicting serious damage to the German war economy, as many industries proved to be exceedingly resilient. Fighter production proved a particularly difficult target, as apart from the later targeted aero engine industry, production and final assembly plants could be dispersed and were largely safe from raiders. When fighter production was further streamlined and resources were diverted to support it, Germany would end up vastly expanding fighter production during the period in which those industries were the most frequently raided (Zeitlin 59). This was, however, was achieved only by reducing the rate of modifications and improvements, and transferring resources away from the production of bombers. In comparison, the later targeting of fuel production and rail transportation proved key, as the inability to reliably move material by rail combined with chronic fuel shortages proved a fatal military and economic obstacle. As a result, establishing air supremacy over Western Europe before Operation Overlord was as much an achievement of long range fighter operations as it was of the bombers. The Luftwaffe could sustain itself when aircraft deliveries did not meet expectations, but it quickly found itself struggling when it lost scores of pilots and found itself hard pressed to train new ones once they had lost control of the skies over Germany.

In the end it must also be said that the civilian costs of the raids were steep, and while the Eight and Fifteenth Airforces were not involved in a campaign directed against the civilian populace, as was the case with Bomber Command and the USAAF elsewhere, the technical limitations of the time meant that bombs frequently fell on civilian areas. Even under ideal circumstances, the dimensions of a bomber formation were larger than their targets and it was physically impossible to strike factories, railyards, and refineries without causing significant damage to the surrounding area. The realities of the campaign would also prove worse than predicted. Targets were frequently obscured by bad weather and smoke generators, and formations typically took heavy anti-aircraft fire on the approach. As a result, bombs were often released by the best estimate from the bomb sight or at the direction of a ground mapping radar system (Overy 347). Even outside of Germany, the civilian costs of these operations were heavy as the Allied air forces carried out the transportation plan. In France alone, between March and June of 1944, French officials placed the figure of civilians killed by Allied bombing at 25,266 (Overy 574).

The 4th Fighter Group ‘Debden Eagles’

When the US entered the Second World War, few American airmen had any combat experience, with the notable exceptions being volunteer airmen in service with foreign armies. The Debden Eagles were one such group, having volunteered to serve with the RAF and entered service in late 1940 and 1941. While they were among the few Americans fighting against Nazi Germany at the time, they had garnered a somewhat unfortunate reputation as glory-seekers and primadonnas thanks to their unique position (Bucholtz 6). Their tendency of excessive overclaiming of victories during this period would prove particularly irritating to their superiors. With the US entry into the war, the Eagle squadrons, and their Supermarine Spitfires, were subsequently integrated into the USAAF.

The RAF’s 70th, 121, and 133 Eagle Squadrons would become the 334th, 335th, and 336th Squadrons of the 4th Fighter Group on the 12th of September 1942. These units flew Spitfire Mk IX’s and within the month were supporting the nascent bomber offensive which was targeting installations in France. The start of this effort went poorly, when only one aircraft out of a twelve plane flight returned, the rest having been lost to enemy fighters, harsh weather conditions, or having run out of fuel in the short range fighter. Thankfully for the Group, this would be their worst day of the war. Despite this setback, the unit saw its first major mission carried out on the 20th of October in the Calais area escorting B-17’s carrying out a high altitude raid. This would be the first major bomber operation carried out under escort and was met with success. Their Spitfires would prove a very capable fighter aircraft, but their short range rendered them unable to conduct escort missions far beyond the English Channel. In any case, this wouldn’t prove much of an issue, as for the rest of the year as they would mostly conduct fighter sweeps across the low countries and provide convoy cover (Bucholtz 9). However, with the changing of the year, the 4th would exchange their venerable Spitfires for new P-47’s.

The 4th FG flew their Spitfires in combat for the last time on April 1st, 1943, after which they completed the full transition to P-47C’s. This change was not viewed favorably, as most of the unit’s pilots disliked the considerably heavier Thunderbolt (Marshall & Ford 340). The changeover had little initial impact on operations, and the squadron was largely involved in the same missions as before. However, the group would later accompany bombers on deeper raids into Europe thanks to newly issued external fuel tanks for their P-47’s. They would use these new 200 gallon fuel tanks on an escort mission into Ghent on July 25th and soon after their first foray into Germany airspace over Westhoff-Emmerich. It should be noted that these fuel tanks were a rare piece of equipment at the time and the 4th only had them thanks to the efforts of Lt. Col. Cass Hough of the 8th Fighter Command’s technical section. They were, unfortunately, as troublesome as they were vital, often failing to transfer fuel above 20,000, and were later withdrawn as British made paper 108 gallon tanks became more available (Marshall & Ford 411).

Despite their complaints, the 4th FG’s veteran pilots would master their new planes and had put them to good use. In a battle defending a formation of B-17’s over the city of Utrecht, the 4th FG was credited for the destruction of nine enemy aircraft at the cost of one of their own, with the pilot having bailed out over the occupied Netherlands (Bucholtz 16). With their P-47s, the 4th would take up an important supporting role in the escalating bombing offensive, one which saw their longer ranged P-47s making more flights into the German frontier. This tempo and the 4th’s change in command under the more aggressive Lt. Col. Don Blakeslee would see the unit become among the most successful in the entire USAAF.

Lt. Col. Blakeslee was made C.O. of the 4th with the turn of the year, and in addition to bringing new, more aggressive tactics to the table, he would work to ensure his unit was re-equipped with the new P-51. Blakelsee would meet personally with General William Kepner and argue that his squadron would be the best candidate for refamiliarization with the new plane as their experience with the similarly-engined Spitfire would make for an easier transition. Kepner was convinced, and subsequently put the 4th FG at the top of the list for P-51’s. The schedule for the transition was harsh as they continued to fly combat missions in their P-47’s while also familiarizing themselves with the new aircraft. The process was time consuming and they would not make their operational debut with their new planes until February 28, 1944 (Marshall & Ford 432). These Mustangs would nearly double the combat range of the unit, and the pilots favored them over their older P-47’s, but they experienced a variety of harsh teething issues and mechanical failures.

While the conversion was taking place, the 4th would be committed to Doolittle’s more aggressive strategy against the Luftwaffe, with the aim to achieve aerial supremacy over Western Europe before the invasion of France. As such their independent actions increased, and on January 31, 1944, they would join the 355th FG in bombing the Luftwaffe’s airfield at Gilze-Rijen (Marshall & Ford 425). In many ways this mission bore some similarity to the fighter sweeps they had conducted since they had flown with the RAF, but it would mark a first in that direct assaults on Luftwaffe airfields would then become more commonplace. Among the last major actions the unit would perform with its P-47s was its support of ‘Big Week’.

Their first combat mission in the new planes was fairly uneventful, on February 28, when flying as escorts for a formation of bombers attacking a V-1 launch site they encountered no enemy aircraft but strafed a Ju 88 on their way home. They would claim their first aerial kills two days later during a bomber withdrawal support mission near Frankfurt where they claimed two enemy fighters (Bucholtz 38). The following day the unit would help achieve a major milestone, the first fighter escort operation to Berlin and back. The operation would prove anything but easy, as deteriorating weather conditions saw most of the aircraft involved turn back. However, elements of the 3rd Bomb Division would press on, supported by the 4th, 55th, 354, and 363rd FG’s. The 4th would engage a formation of roughly 60 Fw 190’s and Bf 110’s northeast of Wittenberg in the day’s first encounter with the enemy. They claimed five victories but suffered one loss from enemy fire, and another as a result of a radio failure which made navigation across a storm in the English channel impossible. The pilot was later forced to ditch his aircraft in France after a failed attempt to reach neutral Spain (Marshall & Ford 439, Bucholtz 39).

Perhaps the most exciting encounter that day was experienced by Capt. Don Gentile and Lt. John Godfrey, both aces in the 4th. The two pilots were unable to join the rest of their flight as a result of extremely poor weather, but proceeded with their mission regardless. En route the weather would clear, and reveal a flight of roughly 50 Do 217 night fighters, pressed into service as daylight bomber destroyers, and dozens of Fw 190’s which were preparing to attack a nearby formation of USAAF bombers. The pair would decide to attack, in order to disrupt the enemy formation and prevent them from engaging the nearby bombers from an advantageous position. Gentile and Godfrey dove on the night fighters, damaging one and sending the group diving in an effort to escape. The engagement turned into utter chaos as the single-engined fighters joined in. In the confusion, the pair of aces would claim one enemy aircraft in a series of defensive fights that eventually saw them make their escape through the clouds. Flying on instruments and practically lost, they made their way back to England by their intuition, landing at RAF Hurn (Bucholtz 40).

The unit would return to Berlin on March 6 in support of a massive 8th Air Force operation. Favorable weather conditions would allow the 8th to dispatch a force of 730 bombers against a series of targets in and around the German capital, where they would meet the Luftwaffe in the largest air battle of the war up to that point. The 4th, led by Col. Blakeslee, would be tasked with escorting the bombers, which would prove a difficult undertaking, with the sheer number of opponents forcing the group to disperse into individual flights and sections to expand their coverage. The unit would be credited for the destruction of 15 enemy aircraft of the 45 claimed by P-51’s that day, in exchange for five losses. In comparison, P-47 units were credited with 37 kills for 5 losses, and P-38 units brought down three units at the cost of three of their own. It should also be noted the P-38’s comprised the minority of the fighters, while there were roughly twice as many P-47’s as there were P-51s. The USAAF would claim a total of 83 ‘confirmed’ enemy aircraft with the Luftwaffe having recorded the loss of 75 fighters (Marshall & Ford 439; Bucholtz 43, 45). The majority of these kills were twin engine and night fighters pressed into daylight service. This engagement, while not representing a distinct turning point, did demonstrate a noticeable shift in the war over Germany. Of the 672 bombers that proceeded with the mission, 69 failed to return, and 6 were written off. These were certainly heavy losses, but were a fraction of the nightmare that the Allies were facing in the summer and autumn of the previous year. Beyond that, Luftwaffe losses were mounting both in the sky and on the ground, and the use of its heavier, twin engined bomber destroyers had become untenable in the face of agile new opponents.

D-Day

Over the coming weeks the 4th would continue to support the bombing campaign, but in June of 1944 they would participate in something far more decisive. The group would be among the many fighter units providing top cover for the invasion of Normandy. Throughout D-Day, each of the unit’s three squadrons would operate independently and continuously until nightfall. The day began with the 334th and 335th squadrons undertaking an offensive patrol under the command of the unit’s C.O., Col. Blakeslee, between 03:20 and 09:45 over Rouen, France. The patrol found no enemy fighters and sought out targets of opportunity, in their case a pair of locomotives that they strafed with their machine guns. Their only loss was 1st. Lt. Fraser, who had lost contact with the rest of the squadron and was subsequently downed by German fighters and taken prisoner. The 336th would sortie at 06:42 to provide cover for warships shelling the landing areas, which proved uneventful (Bucholtz 84).

At 11:20, the 334th would sortie again to Rouen with one section carrying bombs. They would attack a troop train to poor effect, though an encounter with a flight of 10 Fw-190 near their airfield at Evreux proved more successful. In the ensuing battle the 334th was credited with the destruction of four enemy fighters, with the only damaged P-51 making it back home. While this confrontation was happening, the 335th had attacked the marshaling yards at Fleury. The 336th would fly for the last time that day at 13:35 conducting a fighter bomber sweep near Evraux. They would find no targets and would lose an aircraft to ground fire, with 1st Lt. Freiderick being taken as a PoW. The last mission of the day would see the 334th and 335th conduct attacks against a radar station and a road convoy near Rouen. While successful in their mission, they incurred heavy losses when elements of the unit were attacked by around 15 fighters belonging to JG 2 and JG 26 as the US fighters attacked infantry positions.

The day would prove exhausting, with pilots flying up to three missions from dawn to dusk. Between flights most of the 4th’s pilot’s would rest, usually either having coffee or trying to get some sleep in before their next mission. The different squadrons would also find themselves having vastly different experiences, with the 336th having spent most of the day covering the invasion force which the Luftwaffe hadn’t the strength to attack, and taking part in a fighter bomber sweep that found no worthwhile targets and saw one aircraft lost to flak. In comparison, the 334th and 335th spent the entire day conducting offensive sweeps which claimed a number of targets, but also saw them sustain higher casualties than any of the other US fighter squadrons over Normandy that day with ten fighters lost (Bucholtz 82, 83).

Shuttle Mission to VE-Day

Following the success of the landings, and subsequent breakout in Normandy, many of the USAAF fighter units would take on tactical missions in support of the armies in Western Europe, in addition to the ongoing strategic air campaign. However, some P-51 units were selected to participate in an escort mission in which the bombers would land at prepared airfields in the Soviet Union instead of returning to their home bases. A 45 aircraft detachment of fighters from the 4th would depart for the Soviet Union on June 20th. The mission would see them join a force of 1,000 bombers as they attacked targets in the Rhineland, and then on to Piryatin, Ukraine some seven hours away. 45 Mustangs of the 4th would make the trip, encountering some 25 enemy fighters over Siedlice, downing two, but losing one of their own. All but one of the remaining planes landed at their intended destination, with one 2nd Lt. Hofer being forced to land at Kiev after running low on fuel after pursuing enemy fighters (Bucholtz 88). However, unbeknownst to the assembled American aircraft, the formation had been trailed by a Ju 88. Soon after, a well coordinated attack by the Luftwaffe using its He 177 heavy bombers saw many of the US bombers hit, though their P-51’s were unscathed.

The P-51’s were subsequently dispersed and flew a variety of missions in the following weeks which brought them over Central Europe and the Mediterranean. They soon flew an escort mission against an oil refinery in Drohobycz, Poland on the 26th. The return leg of the mission took them to Lucera, Italy where they would support the bombing operations of the 15th Air Force. The largest of these missions would take them over Budapest to perform a fighter sweep ahead of the strike force. There they encountered 80 German and 18 Hungarian Bf 109G’s and a massive dogfight ensued. In the battle the 4th would claim eight Axis fighters at the cost of four of their own. This included 2nd Lt. Hofer who had died during a strafing attack against an airfield. (Bucholtz 89). The unit would be led back to England on the 3rd of July.

Beyond Operation Frantic the 4th settled back into the ‘usual’ operations they’d had since most of the group had left for the Soviet Union. They continued to fly deep penetration and escort missions over Germany, though by the end of the summer, Luftwaffe activity in the air had been considerably reduced. The savage war of attrition over Germany had been decisively won by the USAAF, as the Luftwaffe began to feel ever more crippling shortages of experienced pilots and fuel. Ironically, the Luftwaffe’s supplies of fighter aircraft were secure, though transporting them to airfields would prove ever more troublesome through the remainder of the war. While they had the aircraft, a subsequent USAAF campaign against rail communications across Germany would make overland transportation difficult, and ever more frequent fighter sweeps made transiting by air a very dangerous prospect.

For the remainder of the war the 4th FG remained committed to supporting the strategic bombing campaign, especially as it pertained to offensive fighter sweeps and attacks against Luftwaffe airfields. Their last victory of the war was a probable destruction of an Me 262 that was damaged over the Prague/Ruzyne airfield, with the group credited for 1,058.5 total victories against enemy aircraft, both in the air and on the ground (Bucholtz 120). They would end the war among the most successful Fighter Groups in the USAAF, having come a long way from the overly boastful volunteers that had flown against the Luftwaffe before any other Americans.

The 99th Fighter Squadron ‘The Tuskegee Airmen’

As black aviators, the men of the Tuskegee-trained squadrons would face unique challenges, having to face prejudice from their own countrymen who sought to deny them the opportunity to fight. They were initially excluded from many of the pre-war programs that turned out many of the pilots who later joined the ranks of the USAAF and US Navy. Many who ran these programs espoused the belief that they were incapable of the judgment needed for leadership, and that they had lacked ‘the proper reflexes to make a first class fighter pilot’ in the words of General Edwin J. House (Moye 102).

Their chance came with the Civilian Pilot training program in 1939, having been excluded from the program the previous year. The program was extended to a series of predominantly black colleges and universities, with the most critical being the Tuskegee Institute in Alabama. The university would build a fledgling airfield that eventually grew into an Army Air Corps training base, which proved controversial even among hopeful applicants, as in their eyes they were clearly still segregated from the rest of the Army. While the controversies flowed in the small Alabama town, the Air Corps moved to create the first black pursuit squadron, the 99th.

The first cadets of the 99th would graduate March 7, 1942 under the command of Capt. Benjamin O. Davis. The squadron would subsequently fly within the US before its transfer to the Mediterranean in late March 1943, equipped with new P-40L’s (Moye 99). They occupied a former Luftwaffe airfield in Morocco and were to be attached to the 33rd Fighter Group after they had gotten some experience in theater. In May, the squadron would be deemed ready for service and would move to a field in Tunisia. They would see success there, but the leader of their fighter group, Col. William Moymer was immediately hostile to their presence. He failed to return the salutes of the 99th’s officers and he placed the squadron on patrol duties over secure air space. He would then openly criticize them for being ‘unaggressive’ for failing to claim victories over territory where they were unlikely to encounter enemy aircraft (Bucholtz 18, 19; Moye 101). In spite of this, the unit pushed on and would aid in the preparations for the invasion of Sicily.

The 99th’s first combat missions were fighter sweeps against enemy positions in Southern Italy, their first target being a German airfield on the island of Pantelleria on June 2, 1943. The airbase would be the site of many more attacks, including the unit’s first encounter with enemy fighters. On June 9th, six P-40’s from the 99th Squadron accompanied A-20’s to the airfield, encountering four enemy fighters. In the ensuing fight they successfully drove off the enemy aircraft, and damaged one, taking no losses of their own. A further effort was made to intercept a flight of Ju 88’s at high altitude but were unable to, as their P-40’s had their oxygen systems removed to save weight for the low altitude mission (Bucholtz 21). The pilots of the 99th were particularly enthused that in their first encounter with the enemy, they had managed to complete their mission and all returned home safely.

The squadron would be redeployed days later, partially a result of Moymer who sought to see the squadron reduced to coastal patrol duties. Instead, the 99th was transferred to the 79th Fighter Group, who’s commander, Col. Earl E. Bates, did his best to integrate the unit into the group. While they remained formally segregated, they enjoyed a far more open and professional environment than what they endured with the 33rd (Moye 103). Their first mission with the unit was on July 2 and saw them escort a flight of 16 B-25’s to their target, a German airfield in Castelvetrano, Italy. It would prove less than ideal when the B-25’s failed to line up with their target on the initial approach and had to repeat the attack, giving Axis fighters stationed nearby the time they needed to scramble. Two of the 99th’s pilots were lost in the first pass from the German fighters, but the remaining members soon regained control of the situation. In the ensuing confrontation with enemy Fw 190’s, Bf 109’s, and a Macchi 202, the 99th would claim one confirmed destruction, one probable, and two damaged aircraft. Though perhaps most importantly, none of the B-25’s they were escorting came to harm (Bucholtz 21, 22).

The coming weeks saw them mostly fly ground attack missions in support of the ongoing invasion of Italy, and met very few enemy aircraft for the remainder of the year. It was during this time that they also discovered that the Tuskegee training center wasn’t large enough to supply a sufficient number pilots to the squadron, while also supporting the construction of three additional squadrons. Their pilots resultantly flew an abnormally high number of missions due to being short handed (Bucholtz 25). This period also saw them defeat a great deal of the unfair criticism leveled against them and had largely cemented a favorable reputation within the Army Air Force. Among the most notable victories on that front was an article in Time, which had previously published an article based on Moymer’s alleged grievances with the squadron. Maj. Roberts of the 99th would be quoted “people assumed we were not producing because we were negroes…but now that we have produced, things have changed.” The 99th had also succeeded in convincing most of the 79th FG of their worth, and had garnered a great deal of respect as they moved into 1944. Many white pilots of the 79th disobeyed an order from the commander of the Air Force commander in the MTO, and held a desegregated dinner party to celebrate the anniversary of the 99th’s combat debut (Moye 104, 105).

Forming the 332nd Fighter Group

While 99th gained valuable experience over the Mediterranean, they began to rotate pilots out to train the next pursuit squadrons to form a segregated fighter group. These squadrons were the 100th, 301st, and 302nd, all of which would be formed at Selfridge Field, Michigan. Selfridge would prove a particularly dreadful post for these men, as it was here that they would face intense discrimination both by the local populace and base staff, while being a stone’s throw from the racial powder keg of Detroit. However, this would not remain their home for long, and they would soon depart for their operational assignments by the end of the year. They would join the 99th in the Mediterranean Theater of Operations in January of 1944, being equipped with a set of used P-39s. These aircraft would prove troublesome in service due to their age and condition, and as such numerous accidental losses followed, so by the early summer of 1944, Col. Davis had managed the acquisition of new P-47Ds. However, the unit would soon transition again to the newer P-51 soon after the 99th joined the rest of the fighter group in July, something the group’s veterans would resent as they felt they had been segregated again after finding acceptance within the 79th FG.

The group would fully transition to Mustangs by July of 1944, and would be reassigned to the 15th Air Force where they would support long range bombing operations. Their first mission in their new planes was on July 4th, where they took 40 aircraft to to escort two bomber wings, but they would encounter only a pair of Bf 109’s that made no attempt to attack the allied aircraft . Beyond this, their pace of escort missions rose and they would take part in supporting raids against Axis positions in Northern Italy and Southern France. Soon after, they would provide support for the amphibious invasion of Southern France. On August 12, All four of the 332nd’s squadrons were given specific targets, with the 99th striking radar stations in Montpelier and Sete, the 302nd attacking radar stations in Narbonne and Leucate, the 100th attacked the radar stations near Marseilles and Cape Couronne, and the 301st attacked four targets around Toulon. At the loss of three pilots, one captured and two killed, all of the targeted radar stations sustained considerable damage .

The remainder of the war saw the 332nd fly a considerable number of escort missions, including an earlier attack against the Ploesti oil fields in Romania on July 13th, 1944. It was during that mission that they had begun to cement their status as one of the most reliable escort units in the USAAF, after they dispersed a flight of eight German fighters that had attacked bombers of the 55th Bomb Wing. Their C.O., Col. Davis maintained an unwavering directive to his unit, on escort missions they were never to abandon their bombers. This didn’t sit well with some but it was accepted, in part because many felt that a failure to protect the bombers would come down harder on them than the other squadrons (Bucholtz 51, 105; Moye 102). As such, their record for defending bombers was exemplary, having lost only 27 bombers to enemy fighters from June of 1944 to April 1945. It should also be noted that 14 of these losses occurred during a single day when a failure in mission planning resulted in the bombers and their escorts failing to meet at the proper time. As the target that day was the Luftwaffe air base at Memmingen, Germany, losses were correspondingly high (Bucholtz 53, Haulman 2). This places the remaining 13 bomber losses among the other 178 escort missions they performed over ten months. This policy would however, result in the squadron having the lowest aircraft kill to loss ratio of any other P-51 squadron in the theater, however, they would still consistently outscore all of the veteran P-38 squadrons in the Mediterranean (Marshal & Ford 477).

Among their most impressive escort missions was in support of a bombing raid against the Daimler-Benz tank assembly plant in Berlin, on March 24, 1945. From the 332nd’s base in Ramitelli Italy, this was a 1600 mile round trip, the longest mission ever conducted by the 15th Air Force. 59 Mustangs of the 332nd would leave their base at 11:45 under the command of Col. Davis, though he would soon return after experiencing engine trouble and left the squadron in the command of Capt. Edwin Thomas. They would encounter some two dozen enemy fighters outside of the German capital, including a number of Me 262s. The jets would initially prove difficult to catch, and the aircraft, belonging to JG 7, would at first disengage from the bombers whenever the escorts drew close. However, several of the jets would later press their attack on the formation. In the ensuing battle 1st Lt. Earl R. Lane, Flt. Officer Joseph Chineworth, and 1st Lt. Roscoe Brown would each be credited with a confirmed kill on three downed Me 262s. On their return flight they engaged several targets of opportunity, including two trains. The success of this mission earned the unit one of their three Distinguished Unit Citations, and the personal thanks of Gen. Lawrence of the 5th Bomb Wing (Bucholtz 108, 109).

Beyond their role as escorts for the 15th Airforce’s bombers, the 332nd would be engaged in a number of fighter bomber missions across the Meditteranean and Central Europe. These missions were conducted whenever time permitted between bombing raids and would see the squadron engage a number of targets. These would include airfields and various transportation targets varying from trains to river barges. A raid on August 30, 1944 would mark the unit’s most successful day when the 332nd attacked poorly camouflaged aircraft at Grosswardein airfield, Romania. In the ensuing strafing attack, they would be credited with the destruction of 83 aircraft with a further 31 damaged, ranging from 30 Ju 88’s, to a pair of super heavy Me 323 transport aircraft (Bucholtz 66). They would mount similar attacks against Axis airfields from Romania to Hungary.

The 332nd would end their campaign at an airfield in Cattolica, Italy, and was credited for the destruction of 111 aircraft in the air, 150 on the ground, 57 locomotives, 600 rail cars, and had flown 15,533 sorties (Bucholtz 116). It was a common myth that the squadron had never lost a bomber to enemy fighters, this being a rumor circulated by the press near the end of the war. This was not the case, but even with the failure over Memmingen, their bomber losses to fighters were half of the average and they were a considerable morale booster for the bomber crews of the 15th Airforce.

Flight Characteristics and Pilot’s Remarks

 

The P-51B would prove to be an excellent fighter, but one that could present some challenges to those unaware of its quirks. It shared most of its general flight and handling characteristics with its older Allison powered predecessors, though some alterations to the design would make themselves felt, and not always to the plane’s benefit or pilot’s wishes.

Overall, the Merlin Mustang’s would prove to be fast and highly maneuverable, but with more complex flight characteristics than the Allison powered models that came before. Under most flight conditions, the plane was positively stable and possessed controls that were light and responsive. This aspect had been improved from the previous models, as the P-51B would be equipped with improved internally sealed and balanced ailerons which kept control stick forces light. These were rated very well, though pilots would note they were still ‘mushy’ at low speeds. However, as the plane’s top speed increased, it was capable of pulling maneuvers that could prove hazardous to pilots. Above 4g turns where a pilot without a g-suit was partially blacked out, the stick reversal could be harsh, but the worst of its effects were eliminated by a 20lb bobweight that was incorporated into the control system later on (Dean 350, 349).

The plane’s stall characteristics were mixed, but mostly mild. A one g stall in a clean aircraft was characterized by a roll to the right which came on after rudder buffering and aileron snatching, and was easily recovered from. Pilots were generally positive about the stall warning and recovery characteristics. However, its accelerated stall behavior proved to be far less universally understood. Some pilots claimed an easy recovery after ample warning, and others claimed it came on suddenly and viciously. Its low drag wings would contribute partly to this, as with its lack of air flow disturbances, stalls could come on without much warning. In the event of a spin, recovery was achieved by throttling back and pulling up while directing the rudder in the opposite direction of the spin. A spin could be serious trouble as a typical recovery resulted in a loss of about 9,000 ft in altitude (Dean 351, 352; P-51B flight manual 80).

While the plane was certainly very capable in regards to its maneuverability, pilots would have to take great caution when performing maneuvers of any kind when the fuselage tank still contained fuel. When the 85 gallon tank still contained fuel, the plane’s center of gravity shifted considerably and induced severe longitudinal instability. Hard maneuvers with any considerable volume of fuel still in the tank would result in a stick reversal that would require the pilot to brace themselves against the movement of the stick. Failing to do so would result in a loss of control or a further tightening of the turn which could result in a high speed stall or even structural failure (Dean 347, 348). Both RAF and USAAF manuals would ban aerobatics with roughly forty or more gallons of fuel in the tank, and suggested caution once it had been reduced to 25 gallons (Pilot’s Training Manual 68, Pilots Notes 30). In service this issue was one that rarely affected the plane’s effectiveness in combat, as the long range tank was the first to be used on long patrols and escort missions and thus typically contained little or no fuel when contact with enemy aircraft was made.

On early and mid production P-51B’s, pilots would also have to be cautious of high speed snapping brought on by the aforementioned longitudinal instability while they were conducting rolls. Pilots caught unaware were often injured during this violent jolt, and rolls were restricted accordingly. The addition of a fin extension for the vertical stabilizer and reverse rudder boost tabs would largely solve this issue, and the restrictions were lifted on suitably modified aircraft (Dean 350).

Perhaps where the aircraft shined the brightest were its dive characteristics, which were achieved as a result of its low drag wings and fuselage. These granted it excellent acceleration and a higher critical mach number than most of its contemporaries. Due to the changes in air flow across an aircraft’s wings as a plane approaches the sound barrier, most aircraft would experience buffeting, and a loss of control along and total loss of lifting forces. This change in flight characteristics that results in this loss of control is known as compressibility, a phenomenon that occurs when an aircraft exceeds the speed of its critical mach number.

Thanks to its laminar flow airfoil, the P-51 was almost unique in its ability to remain controllable at otherwise unheard of speeds. However, in a high speed dive the P-51 would eventually experience compressibility and a pilot needed to be aware of the changing characteristics of their aircraft. In the P-51 this would first be felt through a ‘nibbling’ at the controls, afterwards by the stick ‘walking’ back and forth, and lastly by the aircraft pitching up and down with motions that grew more violent as the aircraft picked up speed (Pilot’s Training Manual 74, 75). On earlier models that lacked the vertical stabilizer extension, there was also directional instability that occurred at high speed, which required rudder correction or the plane could be sent into a spin. However with the later modifications the plane was nothing less than astounding. In diving tests from 35,000ft, pilots were able to reach mach .83 while retaining control of the aircraft, and despite the violent shaking and buffeting of the aircraft, were able to recover from the dive. In more practical conditions, control characteristics would remain normal until the aircraft was between .72 and .74 mach, after which the plane would experience escalating tuck-under, or a tendency to pull downwards airspeed increased. The maximum permissible dive speed was set at 505 mph IAS below 9000 ft, and 300 mph IAS at 35,000 ft, TAS being 539 mph (Mach .81). The maximum permissible engine RPM in dives was 3300 (Dean 341, 342, 343). Overall, the P-51B proved to be phenomenal in a dive, with only the British Hawker Tempest gaining a slight lead in tests, it being another aircraft equipped with laminar flow airfoils (Ethell 62).

Its take-off procedure was fairly typical of contemporary US fighters and required a strong right rudder deflection during take off to counteract the powerful torque from its engine. Its best climb out speed was between 160 to 170 mph IAS, which was quickly achieved after its flaps and landing gear had been retracted (Dean 341). Landing was somewhat more challenging, as the 140 mph IAS glide slope offered poor forward visibility, and little was improved as the plane came in to land at about 90 mph. It was thus fairly common for combat pilots to make tail up, level landings in order to have a better view of the landing strip before touching down. Its widely spaced gear and wide tire tread otherwise made the landing fairly easy.

While the P-51B’s possessed some truly phenomenal flight characteristics, the same cannot be said for the canopy. In US Navy evaluations the ‘birdcage’ canopy was found to result in poor all-around vision, most notably fore and aft. It was also fairly restrictive and made turning to view behind the aircraft more difficult (Dean 353). The frame itself could also not be opened on take off or landing and thus proved to be of some annoyance to pilots. This would later be solved with the addition of the ‘Malcom Hood’ which provided excellent visibility and was far less confining. The rest of the cockpit was judged to be satisfactory and capable of accommodating pilots of varying stature.

Its armament however, was distinctly lacking and fairly unreliable. It’s armament of four .50 caliber AN/M2’s was considerably lighter than most US fighters of the time and were installed in such a way that the ammunition links were prone to deformation in high-g maneuvers. It was not uncommon for P-51B/C’s to return from their missions with several guns malfunctioning as a result of failures to feed or extract. As a gun platform, its qualities were judged as roughly the same as the P-40, and below those of the P-38 and P-47 (Dean 353).

Comparisons with American Fighter Aircraft: Early to Mid 1944

Entering service alongside the P-47 and P-38, the new P-51’s would compare very well. When it came to the P-47D, equipped with R-2800-63’s, these aircraft were in some ways complementary, and excelled in areas the other did not. Thanks to its powerful turbosupercharger, the P-47 would retain the power needed to outperform the P-51 above 25,000ft, but was significantly slower at lower altitudes. The P-47 was also less vulnerable to ground fire and thus better suited for ground attack missions. The P-51B however, outstripped the P-47D in rate of climb, linear speed, acceleration at altitudes below roughly 30,000ft, and dive performance (Ethell 70; Marshall & Ford 526). Ergonomically speaking, the P-51B was the superior aircraft, as the turbosupercharger controls of the P-47D added to the workload of the pilot.

When it came to escorting bombers, the P-47D and P-51B were the most effective tools at the USAAF’s disposal. Both aircraft performed superbly at and above the altitudes the bombers typically flew at, though the P-51B would prove the more vital as it could travel significantly further. By late spring 1944, external fuel tanks had been introduced that extended the P-47’s escort radius across most of Germany, however, by this time the P-51B was capable of accompanying bombers beyond Poland (Marshal & Ford 516). While the shorter range of this aircraft was often used to excuse the high bomber losses during earlier campaigns, the fact is that had they been supplied with the proper external fuel tanks, they would have been capable of deep incursions into German airspace months before the P-51 entered service.

The older P-38J Lightning would not stack up quite as favorably against the new Mustang. While the P-38J possessed a better climb rate and acceleration, it was out-stripped in linear speed by the P-51B at all altitudes, and possessed a very low critical mach number which meant that virtually any opponent at high altitude could escape by diving away. To make matters worse, a number of technical and operational issues spelled trouble for these aircraft in the colder Northern European climate. These issues, compounded by the extremely poor cockpit and canopy of the P-38, saw Lightning squadrons fall behind Thunderbolt and Mustang squadrons in victory credits (Marshall & Ford 439, 516; Ethell 70).

While the P-38J would receive external fuel tanks that would allow it to travel to Berlin and back, it was held back by a number of factors that severely reduced its combat effectiveness. In the European Theater of Operations, the P-51B would present a clear and general improvement over the P-38s, which saw more success in other theaters with conditions that they were better suited to, namely the Mediterranean and Pacific.

German Fighter Comparison: Early to Mid 1944

Entering service near the end of 1943, the P-51B compared very well to the German Fw 190As and Bf 109Gs in service at that time. The typical Bf 109 encountered through the first half of 1944 was the Bf 109G-6 series, which possessed better firepower than those that preceded it, but was heavier, and initially slower for it. These planes were equipped with either the Daimler-Benz DB 605A, or the high altitude, DB 605AS engines, both of which were later equipped with MW-50 boost systems. In all cases the P-51B possessed the superior linear speed, but in the case of MW-50 equipped aircraft, the Mustang had a slightly lower climb rate at low to medium altitude (Marshall & Ford 526, 523; P-51 flight tests). Without the boost system, which came into widespread use in the summer of 1944, the Bf 109G-6 was considerably slower and had a clear disadvantage in top speed and climb rate at all altitudes. The disparity with the high altitude model was much narrower, though the P-51 still held an edge.

When it came to maneuverability, both aircraft had their own advantages, with the Bf 109 having better low speed handling and the P-51 having the advantage at high speed. The dive performance of the P-51B was far superior even at lower altitudes as the Bf 109 experienced stiffening of the elevator at high speed.

Visibility the Bf 109 was more or less on the same level of the standard ‘birdcage’ P-51B, and this would largely remain the case, as both planes would be re-equipped with improved canopies that offered better visibility. However, the cockpit of the P-51 was considerably more spacious and was further improved by the Malcolm hood. The Bf 109’s greatest strength was that it was equipped with an automatic RPM governor and mixture control that took a great deal of work off the pilot.

In terms of armament, both aircraft were comparable, with an unmodified Bf 109G-6 possessing a pair of 13mm machine guns and either a 20 or 30mm cannon, which fired through the propeller hub. Of the two, the 30mm was far less common.

Overall, the Bf 109G-6 was a somewhat dated fighter, one that had its advantages, but was  generally outclassed by the new Mustang. However, upgrades like water-methanol injection, an improved vertical stabilizer, and a new canopy helped keep the aircraft competitive and staved off obsolescence. The much refined ‘Kurfurst’ series would match P-51 performance in a number of areas, but its introduction was well after the Luftwaffe had lost control of German airspace.

The P-51B would face several models of the Fw 190A, with the most up to date being the A-8. The P-51B would have considerable linear speed, climb, and high altitude dive advantages over the earlier models. The Fw 190A-8 would have the benefit of a significant boost in power to its BMW 801D-2 engine, first by means of a fuel injection system, and in the summer of 1944, they were judged robust enough to be run at higher manifold pressures and had their supercharger boost regulators overridden. These modifications allowed the engine to produce significantly more power and increased the aircraft’s top speed at all altitudes (Douglass 344). In terms of top speed, this put these two aircraft on closer footing at low altitude, and ahead of the other two American fighters. It was, however, nowhere close to offsetting the general disparities at higher altitudes. The excellent defensive characteristics of the aircraft helped to offset some of its disadvantages against the P-51, as the Fw 190A held the best roll rate in the theater, solid dive characteristics, and good rearward visibility.

In terms of armament it was no contest, as the earlier A-6’s and A-7’s possessed a pair of either 7.92mm or 13mm machineguns respectively, and a pair of 20mm cannons. This was increased to two pairs on the Fw 190A-8. In regards to ergonomics the Fw 190A was excellent, with good visibility, clean instrumentation, and an advanced engine control system which handled RPM, manifold pressure, and mixture through the use of a single, integrated electro-mechanical computer. Its controls too were tight and responsive, if a little heavy at speed, thanks to its push rod control system. However, as was also the case with the Bf 109, its cockpit was comparatively cramped compared to the P-51.

Subsequent models of both these aircraft, the most numerous being the Bf 109G-14 and the Fw 190D-9, would largely eliminate the performance disparity at low altitude. However, at medium to high altitudes, the P-51 would still enjoy a considerable edge in top speed, dive performance, and high speed maneuverability. Only later Bf 109G’s with enlarged superchargers and better high altitude performance were close to closing the gap, with the K-4 series finally achieving high altitude parity near the very end of the war.

The Me 262 presented a much greater threat in the air for obvious reasons. The jet fighter possessed a top speed roughly 100 miles per hour faster than the P-51 and was the only Luftwaffe fighter capable of following it into a dive. It was, however, considerably lacking in acceleration, which presented itself most dangerously on take off and on the landing approach. While the high top speed of the jets meant that they could disengage safely from most confrontations, they were helpless if caught near taking off or landing. Thus the general strategy for defeating these aircraft was to catch them as they were returning to their bases, where Allied fighters would await them. This is not to say this was easy, as their airfields were well defended by some of the best flak units available to the Luftwaffe and they would eventually have their own dedicated fighter cover (Ethell 97, 98). Higher up the jet could prove a deadly opponent as when flown well, it was extremely difficult to catch and an experienced pilot had control over most engagements.

In any case, encounters with the new jet fighters were fairly uncommon as they were constrained by operational restrictions owing to the temperamental nature of the new turbojet engines and the lack of a dedicated trainer for the aircraft until late 1944. They would not be seen flying against the Allies in appreciable numbers until the late autumn of that year.

Building the P-51B & C

The P-51B’s and C’s were built at plants in Inglewood, California, and Dallas, Texas, respectively. The distinction exists due to the differences in manufacturing between these two facilities, but these are functionally the same aircraft. With the exception of the earliest model, the P-51B-1, which had a different aileron design, their components were interchangeable. The main production models were equipped with the Packard V-1650-7 engine. Deliveries of these models began in February of 1944 (Marshall & Ford 253)

Production of this aircraft was complicated greatly by the breakneck pace of its procurement, which saw massive orders placed before its prototype had completed testing. As such, the aircraft that left the factories differed considerably even when they were built mere weeks apart. While all WWII fighters underwent constant modification, the level and rate of changes made to the P-51B and C were extensive and rapid. In addition to minimal changes, like changing the pilot’s seat from a wooden one to a magnesium one, in a matter of weeks the P-51B would receive an additional fuselage fuel tank, an extension to its vertical stabilizer and a rudder anti-balance tab, and an elevator control system which made use of a 20lb bob weight (Dean 329). These features would constitute a considerable challenge to work into the design without compromising the pace of production for an aircraft that USAAF planners wanted in as great quantity in the shortest possible time.

This challenge would highlight both the greatest strengths and weaknesses in US aircraft manufacturing. Most aircraft factories in the US operated by building large batches where the design would be frozen to allow faster construction. Modifying the design meant changes to the production line, which meant slowing down or stopping. US factories operated at batch sizes of up to 1,500, compared to the British Supermarine Spitfire’s production lines which operated at or below 500. The compromise was the modification center, to which “finished” aircraft would be delivered to be fitted out to new modifications. In practice, this system was extremely inefficient and saw quality control drop significantly. It also proved to be a highly inefficient use of labor, and could represent between 25 to 50% of the total labor required to complete an aircraft. Quality control also dropped considerably as the modification center was primed to try and deliver aircraft as quickly as possible (Zeitlin 55, 59). Lastly, the centers saw a great deal of wastage of material, accumulating a much larger proportion of metal scrap from rushed fittings, and ruined parts than the production lines (O’Leary 142). The USAAF would have its Mustangs, but only at a considerable cost and of initial questionable quality.

In the end they were successful in that they delivered the P-51B in great quantities despite the rushed pace of procurement, development, and production. However, it certainly contributed to the severe teething issues experienced by the aircraft that would see it briefly grounded in March of 1944 and would trouble it for weeks later.

In all, 1,988 P-51Bs were built with the first leaving the production lines, at a very low initial rate, in the summer of 1943 with the first deliveries taking place in August, with a further 1,750 P-51C’s being built. Production of both types declined as the P-51D production began in January of 1944, with the last P-51B’s leaving Inglewood in March and P-51C production continuing for several more weeks (Dean 321).

Construction

Wings

The wing group of the P-51 was composed of each wing, bolted together at the centerline. Each wing was of a cantilever stressed skin construction and consisted of a main panel, the wingtip, the flap, and the aileron. The main panel was built up around a main forward spar and a rear spar, to which twenty one pressed ribs were attached. These spars were spliced together roughly around half their length. A self-sealing 90 gallon fuel tank was fitted at the inboard section and a bay for its .50 caliber machine guns and ammunition was found near the center. The ailerons were of a fairly heavy construction, being all metal and supported by two spars and twelve flanged ribs. They were aerodynamically balanced by a diaphragm attached to the forward edge of the aileron and sealed to the rear spar by a fabric strip. These were controlled by means of a cable, as were all of the control surfaces of this aircraft. These were equipped with trim tabs and were adjustable in flight. The flaps were all metal plain flaps that were hinged on three sealed ball bearings and were hydraulically actuated.

The landing gear was hydraulically actuated with a fully retractable tail wheel. The main landing gear were fixed to the wings by a cast magnesium supports and were equipped with multiple disc brakes connected to the hydraulic cylinder by metal tubing. The wheels were 27 inches in diameter and possessed a fairly wide tread, which helped to give the P-51 excellent ground handling.

The wings of the P-51 were designed to achieve laminar flow and used a NAA/NACA 45-100 series airfoil. It would fall short of true laminar flow as even extremely minor surface imperfections resulted in airflow disruptions that made laminar flow impossible. However, these were among the most aerodynamically advanced wings used by any fighter during the Second World War, providing extremely low drag and excellent high altitude dive performance.

Fuselage

The fuselage was composed of two main sections, both of which had a semi-monocoque construction. The main section was formed by four extruded longerons, around which the intermediate frames and stringers were connected. The upper longerons were extruded H-sections which extended from the sheet metal firewall and tapered into a T-section. The lower longerons, consisting of an H-section and U-channel, extended the full length of the main fuselage. This entire unit was made up of eight assemblies which were riveted and bolted together, these being the firewall, turnover, truss, upper deck, left and right side panels, radio shelf, web assembly, and the radiator air scoop.

The main fuselage section also contained the cockpit, the windshield being composed of a center pane of bullet resistant five pane laminated glass, with two Plexiglas windows to either side. The canopy was either a metal framed Plexiglas ‘bird cage’, or a Malcom Hood. The birdcage had panels that opened outward on the top and port side. The hood slid back across the rear of the canopy. Behind the pilot were lucite windows which enclosed the radio space. A relief tube was installed and stored beneath the seat, and proved quite useful considering the long flights that this aircraft commonly made.

The rear section was comparatively simple, composed of two longerons, a shelf, five formers, and three solid bulkheads. The fuselage, as with the rest of the aircraft, was skinned in Alclad. This section was reinforced after structural failures during high speed rolls in early models.

Tail Section

The tail section was affixed to the rear fuselage and consisted of the horizontal stabilizer, elevators, fin, vertical stabilizer, and the rudder. The horizontal stabilizer was a one piece assembly supported by two spars, fixed to the fuselage by four bolts, and through which the vertical stabilizer was attached. The elevators consisted of a front spar with eighteen flanged ribs, and was initially fabric skinned with Alclad leading edges before it was later entirely metal skinned. These were fastened with five sealed ball bearing hinges and each had an adjustable trim tab.

The vertical stabilizer was supported by two spars along with four ribs and a detachable tip. Extensions to the vertical stabilizer by means of a fin were added to P-51B/C’s to correct for longitudinal stability issues with a full fuselage fuel tank, and to correct certain undesirable characteristics when the aircraft was put through a roll. The rudder was fitted at the rear of the stabilizer and was supported by a single spar to which twenty flanged ribs were attached. Much of the rudder was skinned with mercerized cotton, save for the reverse edge. The rudder was fitted with a trim tab and aerodynamically balanced by means of a 16.6 lb lead weight at the tip.

Engine Section

The engine section consisted of the engine mounting and external cowl components and was bolted to the firewall. The cowl consisted of a frame made of Alclad beams to which the cowl panels fastened. This frame acts as a cradle for the engine which is mounted by a bracket through anti-vibration units. The entire section is designed to facilitate easy access to the engine through panels, and the engine mount allows for the rapid removal of the Packard engine.

Engine

The early models of the P-51B used a Packard V-1650-3, with this engine being replaced on the production line in February of 1944 with the Packard V-1650-7. These are largely the same engine, though their superchargers were geared for optimal performance at different altitudes and thus have different maximum outputs. The 1650-3 was designed specifically for high altitude use and gave the P-51B/C a full throttle height of 29,000 feet, the 1650-7 was geared to achieve a higher engine output at a FTH of 21,400 feet (Marshall & Ford 253).

These engines had a bore of 5.40 inches, a stroke of 6 inches, a displacement of 1,649 cubic inches, a compression ratio of 6.0:1, a width of 30 inches, a height of 41.6 inches, length 87.1 inches, a frontal area of 5.9 sq. ft, and a weight of 1690 lbs. They differed in that the -3 supercharger ratios of 6.391:1 and 8.095:1, and those of the -7 were 5.80:1 and 7.35:1 (Wilkinson 125, 127). They were both fitted with a four blade Hamilton-Standard 24D50-65 or -87 hydropneumatic propeller with aluminum blades of a diameter of 11 feet and 2 inches. These blades were either 6547-6, 6547A-6, or 6523A-24 types. The engine exhaust stacks were of a stainless steel construction which had a removable exhaust shroud to keep heat from the spark plugs and to reduce drag.

Both engines used a two stage, two speed supercharger and was equipped with an aftercooler. The supercharger was automatically controlled and governed by the air pressure at the carburetor intake, which was found just below the prop spinner. The controls for the engine were conventional, requiring manual throttle and rpm adjustments.

Radiator and Cooling Systems

The engine was cooled by two separate systems, one dedicated to the engine, and the other cooled the supercharged fuel-air mixture. Both of these systems were connected through the main radiator matrix within the air scoop below the main fuselage, with the coolant flow maintained by an engine driven pump. A smaller radiator for the oil cooler was placed below and ahead of the radiator matrix for the engine and aftercooler. The radiator setup was designed to make use of the Meredith effect, which in practical terms meant that the heated air flow out of the radiator produced thrust which counteracted a large percentage of the drag incurred by the scoop. The outlet for the radiator was automatically controlled. This design was able to reduce net drag upwards of 90% and was one of the most important features which allowed the aircraft to achieve such a high top speed (Marshall & Ford 510).

The hoses for the radiator which extended through roughly two thirds of the aircraft, and the unarmored radiator, which sat at the bottom center of the aircraft, constituted the most vulnerable part of the aircraft’s design. These made the aircraft fairly vulnerable to ground fire, as the high cooling requirements of the Packard Merlin engine meant that a failure of the cooling system wouldn’t take long to put the aircraft out of action.

Fuel System

The initial models of the P-51B possessed only two 92 gallon wing fuel tanks with an 85 gallon fuselage fuel tank being included later through modification kits and was eventually incorporated into the production line. The Mustang was also capable of carrying two external fuel tanks by means of wing mounts. Fuel was drawn only from individual fuel tanks, requiring the pilot to manage up to five individual sources of fuel throughout longer flights (Pilot’s Training Manual 26).

The inclusion of the 85 gallon fuselage tank would introduce new challenges, as the shift in weight caused by a full tank introduced severe longitudinal instability. For this reason this tank was the first to be consumed. The combined tankage was 269 gallons.

Armament and Armor

P-51B’s were equipped with four .50 caliber AN/M2 machine guns. Each inboard gun was supplied with up to 250 rounds, with the outboard weapons having 350 each. These guns were mounted at roughly 45 degree angles within the wing, which caused severe cycling issues when the guns were fired while the aircraft was pulling hard maneuvers. These issues were lessened with the addition of electric boost motors for the ammunition feed, but were not completely solved until the subsequent P-51D model. The guns were electrically heated to prevent them from locking up at high altitudes. These aircraft were typically equipped with the N-3B reflector gunsight, with later aircraft receiving K-14 gyroscopic gunsights.

Wing pylons allowed the aircraft to carry a payload of up to 500 pounds at either side, being either external fuel tanks or bombs. These aircraft could be made to carry rockets by means of field modification kits. Armor plates were placed ahead of the radiator header tank, at the engine fire wall, and behind the pilot.

(Dean 355-376)

Conclusion

It would take a considerable effort to develop the P-51B from its Allison engined predecessors, and even greater hurdles would have to be overcome to produce them in the quantities needed. In the end, both were achieved and the P-51B would enter large-scale operation in the Spring of 1944. In spite of its harsh teething issues, it would become among the most decisive weapons of the Second World War. With its incredible range and medium and high altitude performance, the aircraft would prove instrumental in establishing air superiority over Western Europe prior to Operation Overlord, and contesting the skies over Germany itself.

Its design, while not revolutionary, was thoroughly advanced and represented a considerable leap in aerodynamics and airframe design. The P-51B would however, be only a starting point for the Packard Merlin Mustangs, as further refinements would result in the iconic, and much more widely produced P-51D.

Specifications

P-51B/C ( with Fuselage tank)	Specification
Engine	Packard Merlin V-1650-3, V-1650-7
Engine Output [V-1650-7]	1630 hp [1720 hp]
Maximum Escort Fighter Weight	11,150 lbs (2x108gal external)
Gross Weight	9,681 lbs
Empty weight	6,988 lbs
Maximum Range [External Fuel]	1350 miles [2150 miles]
Combat radius [External Fuel]	375 miles [750 miles]
Maximum speed (V-1650-7)	444 mph (75″ Hg) at 20600ft
Armament	4x .50 cal M2 machine guns, 1200 rounds of ammunition
Crew	Pilot
Length	32′ 2
Height (tail down)	12’8
Wingspan	37.03′
Wing Area	235.75 sq.ft

 

P-51B/C ( with Fuselage tank)	Specification
Engine	Packard Merlin V-1650-3, V-1650-7
Engine Output [V-1650-7]	1630 hp [1720 hp]
Maximum Escort Fighter Weight	5058 kg (2×409 liters external)
Gross Weight	4391 kg
Empty weight	3169 kg
Maximum Range [External Fuel]	2172 km [3460 km]
Combat radius [External Fuel]	603 km [1207 km]
Maximum speed (V-1650-7)	714 km/h (1905mm Hg) at 6279 m
Armament	4x 12.7mm M2 machine guns, 1200 rounds of ammunition
Crew	Pilot
Length	9.80 m
Height (tail down)	3.86 m
Wingspan	11.29 m
Wing Area	21.9 sq.m

(Dean, Performance Tests on P-38J, P-47D and P-51B Airplanes Tested with 44-1 Fuel., Marshall & Ford)

Maximum Level Speed	Speed at 67″ Hg, 3000 RPM	75″ Hg, 3000 RPM	No wing racks, 75″ Hg, 3000 RPM
Sea level	364 mph	380 mph	388 mph
Critical altitude low blower	408 mph at 10400 ft	411 mph at 2300 ft	422 mph at 7400ft
Critical altitude high blower	426 mph at 23900 ft	431 mph at 20600ft	444 mph at 20600ft
Aircraft Specification	Gross weight 9680lbs, P-51B-15	(V-1650-7)

*A note on fuels: The 75″ of manifold pressure figure represents the high end of performance using 150 octane fuels, these were typically only available to P-51 squadrons based in England.

Climb rate	67″, 3000 RPM	75″ Hg, 3000 RPM
Maximum at low blower	3,920 ft/min at 5600 ft	4,380 ft/min 2,300 ft
Maximum at high blower	3,170 ft/min at 19,200 ft	3,700 ft/min at 15,600 ft
Aircraft Specification	Gross weight 9680lbs, P-51B-15

 

Maximum Level Speed	Speed at 1701 mm Hg, 3000 RPM	1905mm Hg, 3000 RPM	No wing racks, 1905mm Hg, 3000 RPM
Sea level	586 km/h	611 km/h	624 km/h
Critical altitude low blower	656 km/h at 3169 m	661 km/h at 701 m	679 km/h at 2255 m
Critical altitude high blower	685 km/h at 7284 m	693 km/h at 6278 m	714 km/h at 6278 m
Aircraft Specification	Gross weight 4390 kg, P-51B-15	(V-1650-7)

 

Climb rate	1701 mm Hg, 3000 RPM	1905 Hg, 3000 RPM
Maximum at low blower	1194  meter/minute at 1707 m	1335 meter/minute 701 m
Maximum at high blower	966 meter/minute at 5852 m	1128 meter/minute at 4755 m
Aircraft Specification	Gross weight 4390 kg, P-51B-15

(Performance Tests on P-38J, P-47D and P-51B Airplanes Tested with 44-1 Fuel.)

P-51 Variants through P-51D

North American	USAAF	RAF	Engine	Armament	No. Built	Additional Notes. First delivery
NA-73X	–	–	Allison	–	1	Prototype. October 1940
NA-73, -83	XP-51	Mustang Mk I	Allison	2x .50 cal MG, 4x .30 cal MG	622	RAF, export. August 1941
NA-91	P-51	Mustang Mk Ia	Allison	4x 20mm cannons	150	‘Plain P-51’. July 1942
NA-97	A-36A	–	Allison	6x .50 cal MG, bombs	500	Dive Bomber. October 1942
NA-99	P-51A	Mustang Mk II	Allison	4x .50 cal MG	310	March 1943
NA-101	XP-51B	–	Packard	4x .50 cal MG	2 (converted)	P-51B prototype
NA-102, -104	P-51B	Mustang Mk III	Packard	4x .50 cal MG	1988	Inglewood production. Summer 1943
NA-101, -103	P-51C	Mustang Mk IIIB	Packard	4x .50 cal MG	1750	Dallas production. August 1943
NA-106 (through -124)	P-51D	Mustang Mk IV	Packard	6x .50 Cal MG	+8000	Bubble canopy. January 1944

(Dean 321)

P-51B & C Variants

P-51B & C Variants	Notes	Serial No.’s
P-51B-1-NA	Earliest production model, steel aileron diaphragms, two point aileron attachment.	43-12093 to 12492.
P-51B-5-NA	Three attachment points per aileron, non-magnetic diaphragm.	43-6313 to 6352, 43-6353 to 6752, 43-6753 to 7112.
P-51B-7-NA	B-1s and 5s which received a new fuselage fuel tank carried this designation. Aircraft often carried prior designation in practice. Converted aircraft.	–
P-51B-10-NA	Production model with fuselage tank.	43-7113 to 7202, 42-106429 to 106538, 42-106541 to 106738.
P-51B-15-NA	Engine changed to Packard V-1650-7 (previous models were converted to this engine via supercharger kits).	42-106739 to 106908, 42-106909 to 106978, 43-24752 to 106738.
P-51C-1-NT	Same as P-51B-5-NA.	42-102979 to 103328
P-51C-2-NT	C-1s which received a new fuselage fuel tank carried this designation. Aircraft often used prior designation in practice. Converted aircraft.	–
P-51C-5-NT	Same as P-51B-15-NA.	42-103329 to 103378, 42-103379 to 103778.
P-51-C-10-NT	Production model with stabilizing fin extension.	42-10818 to 103978, 43-24902 to 25251, 44-10753 to 10782, 44-10818 to 10852, 44-10859 to 11036, 44-11123 to 11152.
P-51C-11-NT	Production model.	44-10783 to 10817, 44-10853 to 10858,44-11037 to 11122.
F-6C	Photoreconnaissance. Converted Aircraft.	–
TP-51C	Dual control trainer. Converted Aircraft.	–

(Marshall & Ford, O’Leary)

Video

Gallery

Illustrations by Ed Jackson

Credits

• Written by Henry H.
• Edited by  Ed Jackson & Henry H.
• Illustrations by Ed Jackson

Sources

Primary:

• Flight Tests On The North American P-51B-15 Airplane, AAF NO. 43-24777, 1944.
• Preliminary Results of Performance Tests on a P-51B Airplane with 44-1 Fuel P-51B-5-NA, V-1650-7 Engine. 1944.
• P-51B-15-NA 43-24777 (Packard Merlin V-1650-7) Performance Tests on P-38J, P-47D and P-51B Airplanes Tested with 44-1 Fuel. (GRADE 104/150). 15 May, 1944.
• Matthews, H. F. Elimination Of Rumble From The Cooling Ducts Of A Single-Engine Pursuit Airplane. NATIONAL ADVISORY COMMITTEE FOR AERONAUTICS. 1943.
• Messerschmitt A.G. Augsburg. (1944). Leistungen Me 109 G-14/U4 mit Db 605 Am u. Asm. 1944.
• Pilot Training Manual for the Mustang. United States Army Air Force, 1943.
• Pilot’s Flight Operating Instructions P-51B-1 Airplane. Evansville, Indiana: United States Army Air Force, 1943.
• Pilot’s Notes for Mustang III Packard Merlin V-1650-3 Engine. Air Council, 1944.
• Wilkinson, Paul. Aircraft Engines of the World. 1944.
• The United States Strategic Bombing Survey: Over-All Report (European War). U.S. Govt. Printing Office, 1945.

Secondary:

• Bucholtz, Chris. 332Nd Fighter Group: Tuskegee Airmen. Oxford: Osprey Publishing, 2007.
• Bucholtz, Chris. 4Th Fighter Group “Debden Eagles”. Oxford: Osprey Publishing, 2008.
• O’Leary, Micheal. Building the P-51 Mustang the Story of Manufacturing North American’s Legendary WWII Fighter in Original Photos. Specialty Pr Pub & Wholesalers, 2011.
• Dean, Francis H. America’s Hundred Thousand: the US Production Fighter Aircraft of World War II. Schiffer Publ., 1997.
• Douglas, Calum E. Secret Horsepower Race: Second World War Fighter Aircraft Engine Development on the Western Front. TEMPEST, 2020.
• Ethell, Jeffrey L. Mustang: A Documentary History of the P-51. London: Jane’s, 1981.
• Haulman, Daniel L. Nine Myths about the Tuskegee Airmen. October 21, 2011.
• Marshall, James William; Ford, Lowell. P-51B Mustang: The Bastard Stepchild that saved the Eighth air force. Bloomsbury Publishing Plc. 2020. (Electronic)
• Moye, J. Todd. Freedom Flyers: The Tuskegee Airmen of World War II. New York, NY: Oxford University Press, 2012.
• Overy, Richard James. The Bombing War: Europe 1939-1945. London: Penguin Books, 2014.