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THE 456th FIGHTER INTERCEPTOR SQUADRON |
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THE PROTECTORS OF S. A. C. |
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THE P-51 "MUSTANG" |
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P-51 vs. FW-190
There are a handful of combat aircraft that are known to every who can tell one such machine from another, and among this elite is one of the most famous aircraft in history: the North American P-51 Mustang. The Mustang had roots in two countries, the US and Britain. It was designed by Americans to a British specification, only reaching its full potential when fitted with a British engine. The P-51 was a "Cadillac" that proved its worth against the Axis, and in postwar years continued to serve in the close-support role with the air forces of many countries.
This document provides a history and description of the P-51 Mustang and the F-82 Twin Mustang.
The Allison "Mustangs"
* The Mustang began life powered by the American Allison engine. While the Allison would not prove the best match to the aircraft, a large number of Allison-powered Mustangs were built and gave good service.
NA-73
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A-36A Invader
North American Aircraft (NAA) was founded in 1934, with 75 employees under President James H. "Dutch" Kindelberger, previously of Douglas Aircraft. NAA was an outgrowth of North American, an aviation-oriented holding and investment organization that had been established in 1928. The NAA offshoot was created with General Motors backing, and built a plant in Inglewood, a suburb of Los Angeles, California. NAA's first major aircraft designs were a series of trainers that culminated in the popular AT-6 Texan.
By 1937, the governments of Britain and France were becoming increasingly alarmed by German rearmament, and were not only ramping up their own production of aircraft, but looking to American sources as well. In 1938, the British placed a large order for North American trainers, resulting in substantial business for the company.
By 1939, the British and French were at war with the Nazis and were scrambling to get their hands on combat aircraft. The only fighters the Americans had available in 1939 and 1940 that seemed to be of any use were the Curtiss P-40 Warhawk and Bell P-39 Airacobra, and neither of them were a match for the Luftwaffe's Messerschmitt Bf-109. The British still purchased a large number of P-40s, which proved serviceable if not spectacular, and a small quantity of P-39s, which the British rejected after evaluation.
Since Curtiss was heavily committed building the P-40 for the United States Army Air Corps (USAAC) and had little production capacity to spare, a delegation sent by the British government proposed that North American produce P-40s under license from Curtiss for the Royal Air Force (RAF). NAA responded with a proposal, submitted to the British delegation in January 1940, that the company instead build an entirely new machine of their own design for the British, based on the Allison V-1710 water-cooled 12-cylinder inline vee engine used in the P-40, but with better range and performance.
Obviously a proprietary design would mean more profits for North American, but there was more than greed as a motive. The P-40 design had roots going back to 1933, and North American engineers were hardly being egotistical to suggest they could build something with better performance, as well as easier to manufacture, using the latest technology. The British delegation was favorable to the idea.
NAA mailed the British delegation in New York drawings of a design concept for the new aircraft in early May 1940, and on 29 May the British awarded a contract to North American for the "NA-73X" fighter, where "NA" of course stood for "North American". The contract specified initial prototype delivery in January 1941, and completion by September 1941. NAA gave the production price of their new aircraft as $50,000 USD in 1941 dollars. After discussions, NAA and the British delegation agreed to an informal schedule for delivery of the first prototype within 120 days. This apparently was not a rigid deadline, since the formal contract gave NAA breathing room, but in any case the NAA design team threw itself into the task with a vengeance.
The chief designer for the NA-73X was a native-born German named Edgar Schmued, who had left Germany for Brazil in 1925, and then emigrated to the US in 1930. He worked closely with aerodynamics specialist Edward Horkey. The team was under the overall direction of NAA Chief Engineer Ray Rice.
Since NAA had never built a fighter, at the request of the British NAA Vice-President Leland Atwood consulted with Curtiss and obtained information on an advanced Curtiss fighter under development, designated the "XP-46". There were similarities between the design of the NA-73X and XP-46 that would eventually lead Curtiss engineers to accuse NAA of plagiarism, but NAA had presented their concept to the British before blueprints were obtained from Curtiss, and XP-46 work significantly lagged NA-73X development in any case.
Some NAA advocates would later claim that the XP-46 provided NAA with little more than a bad example, but the matter is academic as the XP-46 program was abandoned in 1941, after two prototypes were built. The NA-73X and its descendants also had a general layout similar to that of the Messerschmitt Bf-109, which would lead to false rumors that the design of the NAA aircraft was derived from the German fighter.
Although NAA appears to have paid little attention to the XP-46, the NA-73X design team clearly made use of information provided by the US National Advisory Committee for Aeronautics (NACA) on the "laminar" wing. Contemporary wing design featured a wing cross-section with maximum thickness about a fifth of the way across the wing from the leading edge, with most of the curvature, or "camber", on the top of the wing. The laminar flow wing, in contrast, was thickest halfway across the wing from the leading edge, and had almost as much camber on top as on the bottom. This scheme reduced turbulent flow across the wing, cutting down drag and increasing speed and range. The penalty was slightly inferior low-speed performance. The NA-73X's wing featured large flaps to reduce take-off and landing run.
Everything was done to make the NA-73X as aerodynamically clean as possible. The radiator and oil cooler were unconventionally placed on the bottom of the fuselage behind the cockpit, with an airflow exit flap towards the tailwheel. This arrangement provided aerodynamic benefits, at the cost of some additional pipe and duct work.
The resulting aircraft was smooth and attractive. A carburetor intake tube above the prop spinner was one of the few discordant elements. In the NA-73X and a few following aircraft, the entrance to this tube was positioned well back from the prop spinner, but NAA engineers were to find out the hard way that the entrance needed to be moved up to just behind the propeller. The propeller itself was a three-bladed variable pitch type, provided by Curtiss.
NAA engineers did everything they could to combine smooth contours with simplicity of form and underlying structure, with an eye towards ease of manufacture. The cowling, though close-fitting, was easy to remove, and the engine could be conveniently inspected and removed.
Construction was almost entirely of metal, mostly aluminum and aluminum alloy, except for fabric-covered rudders and elevators. The fuselage was in three sections that could be pulled apart by undoing bolts. Each wing was organized as an inner and outer section. The fuselage and wing sections were designed to be assembled as functional units, and then mated together at final assembly, substantially simplifying manufacture.
Provision was made for mounting two 12.7 millimeter (0.50 caliber) Browning machine guns in the nose, positioned under the engine in a staggered fashion to allow accommodation of the ammunition boxes, and firing through the propeller arc using a synchronizing mechanism. Primary armament, however, was to be one 12.7 millimeter and two 7.62 millimeter (0.30 caliber) Browning machine guns mounted in the center of each wing. The wing was so thin that the guns could not be positioned upright, and had to be placed so that they almost rested on their sides. This arrangement would lead to difficulties in practice. The machine guns were also offset vertically, with the two outer guns firing out the leading edge of the wing and the middle gun firing just below the leading edge. The design also allowed a bomb or other store to be carried on a single pylon under each wing.
The cockpit was relatively roomy, and well laid out by the standards of the time, with a "razorback" canopy configuration. The pilot's seat had eight millimeter thick armor behind it, and the front of the canopy was armor glass. The canopy had a hinged panel on the left and a hinged top for entrance and exit. While panel could not be opened in flight, it could be jettisoned in an emergency.
The new aircraft had a sizeable fuel capacity for a fighter, a total of 681 liters (180 US gallons), almost twice the capacity of a Spitfire. There was one fuel tank in each wing, nested between the two wing spars against the wing root.
The main landing gear were simple and robust. They were hinged in the wing to swing down from the wing roots, giving the NA-73X a wide track of 3.66 meters (12 feet) that made it easy to handle on the ground. The tailwheel was steerable and retractable, sealed off in flight by two tiny doors. Aerodynamic controls were hydraulic, while armament controls were electric.
The unarmed NA-73X was rolled out of the factory on 9 September 1940, 102 days after the contract was signed. The design team, which had been working all day, all week, for that time, collectively collapsed in exhaustion and took a few days off. They had the time to rest since the prototype didn't have an engine. The engine was to be supplied by the USAAC, and naturally their own Allison-powered aircraft, such as the P-38, P-39, and particularly the P-40, had priority. The engine didn't arrive for about a month, and was installed in haste when it was finally delivered.
First flight of the NA-73X was on 26 October 1940, with NAA test pilot Vance Breese at the controls, and demonstrated the excellence of the design, though minor modifications were incorporated during the test flights. By this time, the British had ordered 320 of the fighters from NAA, and would quickly increase the order to a total of 620.
Unfortunately, the program ran into a serious delay. On 20 November 1940, NAA test pilot Paul Balfour was bringing the NA-73X back in toward the runway after the fifth test flight. He throttled back to lose airspeed, and the engine stalled and went dead. Balfour performed a dead-stick landing in a cultivated field just short of the runway, and the aircraft flipped onto its back in the soft ground. Fortunately the NA-73X didn't catch fire, since Balfour was trapped in the cockpit and had to be dug out. After he got out, he walked off, in bad humor but otherwise unharmed. The aircraft, in contrast, was seriously damaged, and wouldn't fly again until January 1941.
The problem was traced to the position of the entrance of the carburetor tube on the cowling above the engine. At low throttle and with the aircraft at a high angle of attack, airflow through the tube could be cut off, stalling the engine. The tube was extended to just behind the propeller, as mentioned earlier. Other changes from the initial prototype flight configuration included a modified belly scoop scheme, with the inlet moved forward a short distance, and replacement of the original one-piece "blown" windscreen to a framed windscreen.
By the time the prototype was in the air again, the type had acquired a name. In December 1940, the RAF named it the "Mustang", after a popular tune that had been a hit in America and Europe in the 1930s. The name stuck.
The XP-51 "Mustang I"
The second Mustang to be built was the first production aircraft, and was rolled out on 1 May 1941, well behind schedule. The third Mustang, and second production item, was transported by ship to Liverpool, to make its first flight in Britain on 24 October 1941.
It was fitted with British VHF radio, gunsight, and other incidental gear at the Aeroplane & Armament Experimental Establishment at Boscombe Down, and run through an initial evaluation. On 28 January 1942, the aircraft arrived at the Air Fighting Development Unit (AFDU) at RAF Duxford to begin a complete evaluation. Most of the first 20 Mustangs to arrive in England were used for test and evaluation.
RAF test pilots were delighted with the aircraft. In contrast with the Spitfire V, the Mustang was substantially faster (with a maximum speed of 615 KPH / 382 MPH) at low altitude, handled better in many respects, and most significantly had over twice the endurance and range (over 1,600 kilometers / 1,000 miles). There were points of concern, such as the fact that the cockpit layout differed from that of other RAF fighters. The 7.62 millimeter (0.30 caliber) machine guns used by the Mustang used ammunition incompatible with the standard British 7.9 millimeter (0.303 caliber) guns. The most serious concern, however, was the engine.
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The Allison V-1710-39 (also known as -F3R) engine provided 860 kW (1,150 HP), compared with 885 kW (1,185 HP) for the Merlin 45 used in the Spitfire V. The difference in power was slight, but the problem was that the Mustang weighed a third more than the Spitfire V, and so the Mustang was underpowered. However, as mentioned the flight tests showed it still had excellent performance at low altitude. Although the Allison did incorporate a gear-driven supercharger, it was optimized for low-altitude operation. Development of the V-1710 had been guided by the requirements of the USAAC, and their doctrine had not emphasized high-altitude combat. In any case, the Mustang's performance fell off drastically above about 4 kilometers (13,000 feet).
For this reason the new aircraft, designated "Mustang I", was rejected by RAF Fighter Command and assigned to the Army Co-Operation Command to act in the tactical reconnaissance role. The Mustang was to replace the unpopular Curtiss (P-40) Tomahawks, which were often grounded by mechanical problems and which were no match for the Luftwaffe's fighters.
RAF "Mustangs" In Combat
By the end of 1941, the British had received 32 Mustangs, with more on the way. The Mustang Is began to be delivered to RAF front-line squadrons in January 1942, and entered operational service in February. These initial Mustangs were fully armed but had a reconnaissance camera, fitted in the left cockpit rear window, staring downward at an angle. Later, another camera was fitted just forward of the tail-wheel.
The RAF was concerned enough over the Mustang's general resemblance to the Messerschmitt Bf-109 to give it special recognition markings, consisting of yellow bands around the wings.
The RAF found that reconnaissance missions could also be combined with more aggressive actions, and that the Mustang I was up to both jobs. It was an accurate bomber, and could take on a Messerschmitt Bf 109 or Focke-Wulf FW-190 on fair terms at low altitude.
On 10 May 1942, an RAF Mustang I drew its first blood on a reconnaissance mission over the French coast when it shot up an airfield and a supply train. This action was quickly followed by enthusiastic RAF "reconnaissance and destroy" missions, codenamed "Populars", over France. Such missions involved two Mustangs, one to take pictures and one to keep an eye out for enemy fighters.
The first Mustang to be lost in action went down over France in July 1942. The next month, on 19 August 1942, the Mustang achieved its first air-to-air "kill", during the badly bungled British "practice invasion" at the port of Dieppe in France. The pilot of the Mustang was, by another of the small ironies of the story, an American, Hollis H. Hills, who was a volunteer flier with the Royal Canadian Air Force (RCAF). Hills would later join the US Navy and fly the Grumman F6F Hellcat. The Dieppe operation was otherwise an expensive one for the Mustang, however, with nine shot down and two more written off after their return to base.
By this time, the RAF was finding more uses for the Mustang, in the form of "Rhubarbs" and "Rangers". Both involved sending out pairs of Mustangs to attack German targets in occupied France and the Low Countries. In a Rhubarb, the aircraft were assigned to attack designated targets, while in a Ranger they picked targets of opportunity. However, the permissible list of targets was limited, in order to reduce injury to the local populations. The Mustang was also assigned to RAF Coastal Command to support patrol aircraft, as well as intercept low-flying FW-190s making sneak raids on channel ports.
In October 1942, the long-range Mustang became the first RAF single-engine fighter to fly over Germany; restrictions on targeting were relaxed for attacks on German soil. By this time, the initial batch of 320 NA-73 Mustang Is had been delivered by NAA, as well as most of the second batch of 300. 14 RAF squadrons were equipped with Allison Mustangs. The aircraft in the second batch were designated "NA-83", but incorporated only minor modifications and were hard to tell apart from the first batch. Most of the changes were added to allow the aircraft to operate more effectively under tropical and desert conditions.
The Mustang was developed as a collaboration between NAA and the British, with little direct involvement by the USAAC. However, NAA did have to get US government approval to build combat aircraft for a foreign power, and as part of this "Foreign Release Agreement", the company was required to give two NA-73s to the USAAC. NAA received no payment for these two aircraft, but the possibilities of sales to the USAAC made it worthwhile.
The two aircraft, designated "XP-51", were the fourth and tenth machines off the production line. The first XP-51 was flown in late May 1941, but didn't make it to the USAAF (the "Air Corps" having be superseded by the "Air Forces" in June 1941) testing grounds at Wright Field, Ohio, until late August. The second XP-51 didn't get there until mid-December, by which time tests had been largely completed.
Although the evaluation was very positive, the USAAF was slow to take an interest in the Mustang. They were, after all, preoccupied with the development of aircraft built to their own specifications, such as the Lockheed P-38 Lightning. The Mustang was an outsider in their plans.
Making decisions in large bureaucracies is necessarily slow, since there are many people involved. Military organizations have particular quirks in this regard: they tend to move slowly in peacetime, and then are rushed along much too fast when war comes along. A small, dedicated organization like North American found this sluggishness both hard to understand and frustrating.
There are stories that there was a faction in the USAAF that was strongly opposed to the Mustang, and even that one government official demanded a bribe from Dutch Kindelberger to allow the Mustang to be considered. These stories sound suspiciously like exaggerations, and certainly would be difficult to verify. While a conspiracy of sorts might have existed, there is no need to invoke one to explain events. The USAAF's disinterest was perfectly logical under the circumstances, though later the commanding general of the USAAF, Henry H. "Hap" Arnold, was to say that it had been an extraordinary mistake that the Mustang was not put into service with the USAAF immediately.
The P-51 "Mustang" IA
However, even before the USAAF received the two evaluation Mustangs, they had purchased 150 of them, sort of. In March 1941, US President Franklin D. Roosevelt had signed the "Lend-Lease Bill", which was a thinly concealed military assistance program for nations fighting the Axis powers.
The British had run low on cash, and so on 7 July 1941, the USAAC had ordered 150 "NA-91s" for them, which were formally designated P-51. This was before the RAF had even received its first evaluation Mustang. This Lend-Lease batch of aircraft had an unusual weapons fit, with gun armament consisting of four Hispano-Suiza Mark II 20 millimeter cannon, replacing the six wing-mounted machine guns.
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The cannon armament was introduced at the request of the British, who had been plagued during the Battle of Britain with the feeble firepower of Hurricanes and Spitfires armed solely with banks of rifle-caliber 7.9 millimeter (0.303 caliber) machine guns. The Mustang's two nose machine guns were deleted, and the three machine guns in each wing were replaced by two cannon. The Hispano Mark II had been designed as a "motorcannon", fitting over the cylinder banks of an inline vee engine and with the muzzle sticking out the prop spinner. This meant the weapon was very long and its muzzles distinctively protruded well out in front of the wing of the P-51. Despite the hitting power of this heavy armament, no other major model of Mustang would feature it.
Deliveries began in July 1942, with the RAF giving the new version the designation of "Mustang IA". However, the USAAF diverted 57 of these aircraft for its own use. Two of these were set aside for engine experiments that would prove significant and which will be discussed in the next chapter.
The 55 remaining P-51s were fitted with two reconnaissance cameras in the rear fuselage. They were in theory redesignated "F-6As", but in practice continued to be known as P-51s, or sometimes "P-51-1s". The USAAF also referred to early Mustangs under the name "Apache", but this usage was very short-lived, since the British name quickly triumphed for all P-51 variants.
The A-36, P-51A "Mustang"
By this time, the USAAF was warming to the Mustang, but there was a problem: the US military air fleet was expanding so fast there wasn't any money to buy more fighters for the moment. There was money for attack aircraft, though, and after discussions with the Pentagon NAA came up with a Mustang tailored for the attack role.
Dive bombers were sexy at the times, and so NAA offered the USAAF a dive-bomber version of the Mustang, designated "NA-97". On 16 April 1942, the USAAF ordered 500 of these aircraft, formally designated "A-36A Invader", though the type would still be referred to in practice as a Mustang. These were to be the first Mustangs to be specifically ordered for American service. The A-36A first flew on 21 September 1942, with NAA test pilot Ben Chilton at the controls. The A-26 was powered by an uprated Allison V-1710-87 engine, with 990 kW (1,325 HP) at low altitude. The A-36A was stressed for high-speed dives, and included fence-like hydraulically-operated dive brakes on the top and bottom of each wing.
The previous armament fit of two 7.62 millimeter guns and one 12.7 millimeter gun in each wing was changed to two 12.7 millimeter Browning guns per wing. 7.62 millimeter guns were no longer perceived as lethal enough for air combat, and stocking two different calibers of ammunition for an aircraft was a logistical nuisance. Reducing the number of machine guns in each wing from three to two also simplified the cramped and cluttered gun arrangement inside the wing.
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P-51A
The two 12.7 millimeter Brownings in the nose were retained, resulting in a total gun armament of six 12.7 millimeter guns, though apparently the nose guns were often deleted in the field to save weight. There was a stores pylon under each wing for a 225 kilogram (500 pound) bomb, smoke generator, or 284 liter (75 US gallon) drop tanks.
A single A-36A would be passed on to the British in March 1943. This one aircraft was designated in RAF service as the "Mustang I (Dive Bomber)".
The USAAF soon received more money to buy fighters. The ploy of buying them as a dive bomber no longer being needed, the USAAF placed an order for 310 "NA-99" fighters in August 1942. These aircraft, which were designated as "P-51A" by the USAAF, were very similar to the A-36A, but the dive brakes were deleted, as were the nose guns with their heavy synchronization gear. They also featured an Allison V-1710-81 engine with a new supercharger for somewhat better high-altitude performance, and a larger propeller.
NORTH AMERICAN P-51A (MUSTANG II): _____________________ _________________ __________________ spec metric english _____________________ _________________ __________________ wingspan 11.28 meters 37 feet wing area 21.65 sq_meters 233 sq_feet length 9.83 meters 32 feet 3 inches height 3.71 meters 12 feet 2 inches empty weight 3,000 kilograms 6,600 pounds max loaded weight 4,000 kilograms 8,800 pounds maximum speed 628 KPH 390 MPH / 340 KT service ceiling 9,100 meters 30,000 feet range with drop tanks 2,000 KM 1,250 MI / 1,085 NMI _____________________ _________________ ____________________The first P-51A took to the air on 3 February 1943, piloted by Ben Chilton, and initial production deliveries followed the next month. 35 of these aircraft were fitted with two cameras and designated "F-6Bs", while 50 of them were passed on to the British as "Mustang IIs". These were the last Allison Mustangs built.
By this time, the USAAF had realized the potential of the Mustang. America became the chief patron of an aircraft that had been designed for the British, and which had been ignored by the USA for what some felt was far too long a time.
US "Mustangs" In Combat
Although the RAF had been using Mustangs in combat since the spring of 1942, the USAAF didn't get the type into action until March 1943, after the invasion of North Africa. 35 of the "F-6A" P-51s arrived in that month, and were used in the following months for tactical reconnaissance on German positions in Tunisia during the final drive on the Afrika Korps.
In the meantime, A-36As were pouring into North Africa by the hundreds, with a total of over 300 in action by May. On 7 June, the USAAF performed its first combat mission with the Mustang, performing attacks on the Mediterranean island of Pantelleria. The A-36As participated in the invasion of Sicily in July 1943, and then, having been joined by P-51As, moved to that island to support the landings on the Italian mainland at Salerno in September 1943.
The combat record of the A-36A as a dive bomber is a bit obscure. Some sources claim that the aircraft was much too "slick" and fast to be a good dive bomber, and in fact there were a few fatal accidents during stateside training when structural failures occurred during dive attacks. There were also reports that the dive brakes didn't deploy evenly, making the aircraft more difficult to control in a dive. Stories that the dive brakes were often wired shut, however, appear to be untrue. Problems with the dive brakes were quickly corrected in any case, and some USAAF reports indicate that the A-36A was highly accurate as a dive bomber.
The matter is mostly academic, because it is entirely clear that the A-36A, as well as the P-51A, gave fine service as an attack aircraft during the Sicilian and Italian campaigns. The Mustangs worked hard during the Salerno landings, flying off beachhead air strips while under enemy fire. Combat operations unfortunately emphasized the vulnerability of the Mustang's liquid-cooled engine to ground fire, as well as a high rate of "friendly fire" casualties due to its resemblance to the Bf-109. By March 1944, roughly half of the Allison Mustangs operated by the USAAF in Italy would be gone due to various causes, and the rest would be replaced by July 1944.
The Allison Mustangs contributed a great deal to the Allied war effort as close-support aircraft. One pilot, USAAF Lieutenant Michael T. Russo, was skillful and lucky enough at air combat to become the sole Allison Mustang ace of the war.
In the meantime, the A-36A and P-51A were demonstrating similar virtues at the other end of the Eurasian land mass. A USAAF Mustang fighter-bomber bomber group arrived in India by way of Australia in the late summer of 1943, where it performed attack, reconnaissance, and air combat duties in the China-Burma-India (CBI) theatre.
The Allison Mustangs did not do well in the air combat role. They were at a disadvantage against their primary adversary, the agile Nakajima Ki-43 Hayabusa, known to the Allies as the "Oscar". Although the Oscar had significant weaknesses, being under-armed and lacking in armor protection, the Mustangs got the worst of it in their clashes with the Japanese fighter over Burma. These missions were, however, the first use of the Mustang as a long-range escort fighter, with P-51As carrying two 284 liter (75 US gallon) drop tanks and flying round trips from Kurmitola in Bengal to Rangoon in Burma, 725 kilometers (450 miles) away. It was a hint of things to come.
The Mustangs did well at reconnaissance and close support missions. One P-51A outfit, the 1st Air Commando group, was assigned to provide close support for Orde Wingate's British Chindit warriors in Burma, and operated in the field at rough airstrips to keep up with the battle. They sometimes carried 450 kilogram (1,000 pound) bombs, or the three-tube 11.5 centimeter (4.5 inch) M-8 "bazooka"-style rocket launchers.
The 1st Air Commando group was led by Lieutenant Colonel Philip Cochran, a legendary old China hand who was well-known to the American public through the cartoon character "Flip Corkin" in Milton Caniff's TERRY & THE PIRATES comic strip. Although details are sketchy, the Allison Mustangs appear to have operated in the CBI well into 1944, when they were replaced by P-51Bs.
While the USAAF was cutting their teeth on the Allison Mustangs, the RAF continued to use them to good effect for reconnaissance and attack. The RAF Army Co-operation Command was disbanded in June 1943, with the Allison Mustangs merging back into RAF Fighter Command for a time, and then sent to 2nd Tactical Air Force, which was put together to support the invasion of Europe.
Attrition and war-weariness reduced the numbers of Allison Mustangs in England as they were replaced by better types, but on D-Day there were three RAF, two RCAF, and one USAAF squadrons operating them from Britain. Their numbers continued to dwindle, but by the war's end, the RAF was still operating two squadrons of them, and the USAAF was performing tactical reconnaissance with the handful they had left. The RAF finally phased theirs out at the end of 1945, with about 72 of them still on the lists.
The Allison "Mustangs"
A total of about 1,583 Allison-powered Mustangs were built. Even if the aircraft's evolution had stopped there, these Mustangs were useful enough to give distinction to the type. After the war, the USAAF compiled statistics on the A-36A variant and concluded that the A-36As had flown over 23,000 sorties and destroyed 86 enemy aircraft in air combat, despite being a "mudfighter". The other Allison Mustang variants were no doubt put to similarly good use.
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There were a number of experimental modifications of the Allison Mustangs, especially in British service.
In December of 1942, the British modified a Mustang I to carry eight 27.2 kilogram ("60-pounder") rockets, but the launch rails added enough drag to cut the top speed of the aircraft by 110 KPH (70 MPH). The British tried again in the spring of 1943 with improved launch rails, but with no better effect. The Americans would qualify the A-36A and P-51A for use with the M-8 bazooka-tube launcher, as mentioned, though this caused performance problems as well.
The British performed particularly interesting experiments, beginning in mid-1943, with a Mustang I fitted with a modified wing and tested with various underwing stores, the most spectacular being two Vickers 40 millimeter "S" guns, one under each wing. The two 12.7 millimeter guns in the nose were retained in this configuration, but the wing armament was reduced to a single 7.62 millimeter gun in each wing.
This particular weapons fit was apparently not judged worth pursuing further, since no other Mustang ever featured it. The same could be said of one Mustang I that the British fitted with swiveling landing gear to improve takeoff and landings in crosswinds, and of two P-51As that the USAAF sent to the Aleutians and tested with ski landing gear.
Relatively few Allison Mustangs have survived to the present day. The well-known Chino "Planes of Fame" museum operated a P-51A in air races, and two A-36As were said to have flown the Reno races as well.
One particularly prominent example of the types that has survived is the initial XP-51 obtained by the USAAC for testing in the summer of 1941. This aircraft was scheduled for scrapping after the war, but was rescued for the Smithsonian's National Air & Space Museum. In the 1970s it was restored and flew again, and is now in the hands of the Experimental Aircraft Association in Oshkosh, Wisconsin.
The Merlin "Mustangs"
The Allison-powered Mustangs were good aircraft, and would have an honorable place in the books even if the design had gone no further. However, mated with the British Rolls-Royce Merlin engine, the Mustang became a great aircraft.
The Merlin Experiments
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P-51D
The poor high-altitude performance of Allison Mustang was a concern from the start, but nobody was sure what to do about it. The Allison was about all that was available to NAA for the first production batches of the Mustang. NAA engineers considered moving to a turbo-supercharged version of the Allison, which was used successfully on the Lockheed P-38 Lightning twin-engine fighter, but decided against it.
The American engine manufacturer Packard had come to an agreement with Rolls-Royce in October 1942 to build the Rolls-Royce "Merlin XX" engine, which was used in the Supermarine Spitfire V. The name "Merlin", by the way, was not in honor of the magician, but was the English name for a species of hawk. Like the Allison, the Merlin was a 12-cylinder liquid-cooled inline vee engine, but had a better power-to-weight ratio.
By 1942, Packard was producing Merlin XX engines in quantity as the Packard V-1650-1, but supplies were limited, and there were valid doubts that the Merlin XX was that big of an improvement over the Allison. It didn't offer much more power and only had a two-speed supercharger.
However, Rolls-Royce had been continuously improving the Merlin, so much so that the company began to regard further work on the engine as yielding diminishing returns, with the future lying in the more formidable next-generation "Griffon" engine. Despite that, in mid-1941 the RAF issued a requirement for a high-altitude bomber, the "Wellington VI", and so Rolls-Royce began work on a Merlin variant optimized for high-altitude operation.
Rolls-Royce engineers rejected a turbo supercharger as too big and bulky, and experimented with a two-stage supercharger scheme, with the two superchargers mounted on a common shaft and driven off the engine crankshaft. The compressed inlet air was heated to such a degree that the engine required an intermediate intercooler system to cool it off.
The Wellington VI was never built in large quantity or saw wide service, but the new Merlin engine showed obvious promise for the Spitfire, and was developed for that aircraft as the "Merlin 61". A new Spitfire variant, the "Spitfire Mark VIII", was designed for the two-stage engine. However, the RAF was confronted with rising numbers of Luftwaffe Focke-Wulf FW-190s that outclassed the current Spitfire V, and needed a better Spitfire in a hurry. As an interim measure, Supermarine quickly modified the Spitfire V to accept the Merlin 61, resulting in the "Spitfire IX". The Spitfire IX would prove so successful that it would be produced in greater numbers than the Spitfire VIII.
In April 1942, Rolls-Royce test pilot Ronald Harker visited the RAF Air Fighting Development Unit field at Duxford, and was invited to try out a Mustang. He flew the aircraft for a half-hour and was extremely impressed with it, until he ran into its poor high-altitude performance. He realized that a two-stage Merlin engine was exactly what was needed, and consulted with the Rolls-Royce chief engineer to see what the British engine would do for the American fighter. Studies for a Mustang with a Merlin engine suggested a top speed of 710 KPH (440 MPH) at an altitude of 7.8 kilometers (26,000 feet), well in excess of the capabilities of an Allison Mustang, and possibly even superior than the Spitfire IX in some respects.
Harker pressed his case through the air establishment, and within days Rolls-Royce's facility at Hucknall began conversion of three Mustangs to two-stage Merlin power, with two more conversions put in the queue later. These aircraft were fitted with the Merlin 65 engine subvariant and a four-bladed propeller. The Merlin 65 was optimized for better performance at lower altitude, though unlike the Allison its performance did not drastically fall off at high altitude.
The Merlin conversion was very promising, but the director of the Hucknall establishment, Ray Dorey, had an even more ambitious idea. He wanted to mate the Mustang to a Griffon engine, mounted behind the pilot as was the Allison in the Bell P-39 Airacobra. Rolls-Royce engineers believed this aircraft would be capable of a top speed of 800 KPH (500 MPH), but it never progressed beyond the mock-up stage.
Back in California, while these events were taking place in England, NAA engineers were working along a similar path. They had known about the two-stage Merlin engine since late 1941, and had been considering how to use it with the Mustang.
Packard had negotiated with Rolls-Royce to build a licensed version of a two-stage Merlins, and was moving into production of the Packard V-1650-3, equivalent to the Merlin 68 sub-variant. The first V-1650-3 engines were to roll off Packard production lines in mid-December 1942, with production ramping up to full volume in the following months. If NAA engineers wanted to use Merlin power, the engines would be available when they were needed.
NAA didn't start work on the concept in earnest until late July 1942, when they received the two cannon-armed NA-91s reserved for experimental purposes by the USAAF, mentioned in the previous chapter, and Merlin 65 engines sent from England. This step-up in activity appears to have been partly the work of Lieutenant Colonel Tommy Hitchcock, the US Assistant Military Attache at the American embassy in London. He had flown the Mustang, knew about the Rolls-Royce effort at Hucknall, and was enthusiastically promoting the idea through American channels. NAA engineers threw themselves into the project with the same energy that they had shown in rolling out the initial NA-73X. The new variant was given the company designation of "NA-101" and military designation of "XP-78". By the summer of 1942, work on the Merlin Mustang was in full swing on both sides of the Atlantic.
The two groups were aware of each other's activities, and the spirit was competitive but friendly. The Rolls-Royce group had a head start and got into the air first with their "Mustang X", as the conversions were known, with the initial aircraft flying on 13 October 1942. The next day, Packard officials sent a letter to Rolls-Royce congratulating them on "beaten us to it on the flight of the [Merlin] Mustang. Hope performance is up to expectations."
The Rolls-Royce conversions were experimental improvisations. The conversions featured a deep chin scoop underneath the prop spinner that was faintly reminiscent of late-model P-40s, and gave them a unique appearance among the Mustang family. The first Mustang X was originally fitted with a standard Rotol (Rolls-Bristol) four-bladed propeller, as used by the Spitfire IX. This was later upgraded to a custom-built propeller, though it proved to have little influence on performance.
The performance was very satisfactory. The Merlin 65 could provide more horsepower at altitude than the Allison V-1710 did at takeoff, and the initial Mustang X conversion achieved 700 KPH (433 MPH) at an altitude of 6.7 kilometers (22,000 feet). The aircraft could reach an altitude of 6.1 kilometers (20,000 feet) in 6.3 minutes, about two-thirds the time required by an Allison Mustang. Greater power and torque resulted in a degree of lateral instability in the Mustang X. Various fixes for this problem were considered during the evaluation, including a bigger tailfin, but the problem would get worse before it got better.
The second Mustang X flew on 13 November 1942, and the third flew a month later. Rolls-Royce kept NAA informed of the results of the tests while NAA refined their own conversion, which had been redesignated "XP-51B" in the meantime. The first XP-51B flew on 30 November 1942. As with the Mustang X, performance of the XP-51B demonstrated that faith in the Merlin conversion was justified. NAA test pilot Bob Chilton achieved a level speed of 710 KPH (441 MPH) at an altitude of 9 kilometers (29,800 feet), and the XP-51B could climb almost twice as fast as an Allison Mustang.
This first XP-51B was roughly an "80% conversion", but the second, which flew soon afterward, was closer to a production design. The Merlin 65 had a similar physical "envelope" to the Allison V-1710, but weighed about 136 kilograms (300 pounds) more, and required fitting the intercooler someplace in the fuselage.
The Merlin Xs had the intercooler under the nose, but this was cluttered, and after a six-week bout of headaches NAA engineers managed to accommodate it in the radiator system under the cockpit. They also managed to obtain a small amount of thrust out of the radiator exhaust. In any case, the modification resulted in the belly airscoop hanging a bit lower than in the Allison Mustang.
This was a slight visible change, as was the slightly fatter nose. More noticeable was the switch of the carburetor intake from above to below the prop spinner, giving the new Mustang version sleeker looks than its predecessor. The new design also featured a four-bladed Hamilton Standard propeller with a span of 3.4 meters (11 feet 2 inches), replacing the 3-bladed propeller used on the Allison Mustangs.
Back in Britain, the two final Mustang Xs would be flown in early 1943 and evaluated by the USAAF, but by that time they were of no critical importance. Even before the first Merlin Mustangs flew, back in August 1942, the USAAF had ordered 400 P-51Bs, gambling that they would prove everything that was hoped for them. Rolls-Royce wanted to convert 500 RAF Allison Mustangs to Merlin power, but the resources were simply not available. The Americans were not under such constraints, and so in early 1943 the RAF ordered 1,000 P-51Bs with the designation of "Mustang III".
P-51B, P-51C "Mustang III"
Moving from test to production of the P-51B was a massive job, involving a big expansion of NAA's Inglewood plant. Another huge plant that NAA had recently established in Forth Worth, Texas, to manufacture trainers was scaled up to build even more Merlin Mustangs. Fort Worth aircraft were to be designated "P-51Cs", though they were essentially identical to P-51Bs.
Following comments about the P-51B apply to the P-51C, unless otherwise noted. Note that in some documents, Mustang designations may have a "-NA" suffix, indicating that the aircraft was built in Inglewood, or a "-NT" suffix, indicating that it was built in Forth Worth.
The first production P-51B flew on 5 May 1943, with the first production P-51C flying on 5 August 1943. Production P-51Bs were reinforced and could handle a 450 kilogram (1,000 pound) bomb on each wing rack, or equivalent stores such as drop tanks or triple-tube M-8 rocket launchers. There were minor aerodynamic improvements relative to the XP-51B prototypes as well.
Gun armament on most production P-51Bs was four 12.7 millimeter (0.50 caliber) Browning machine guns, with two guns in each wing. The ammunition box for each inboard gun had a capacity of 350 rounds of ammunition, while the box for each outboard gun had a capacity of 280 rounds. The Merlin redesign had crowded out the two nose guns fitted in some versions of the Allison Mustang, and the Mustang would never carry them again.
Initial production of the P-51B used the Packard V-1650-3 engine, with 1,045 kW (1,400 HP) for take-off, while later production was uprated to the V-1650-7 engine, with 1,080 kW (1,450 HP) for take-off. These Merlins used carburetors instead of fuel injection, and of course had a two-stage supercharger. The supercharger operated at two speeds and engaged automatically at high altitude. The engine was limited from redlining with a safety wire, but in an emergency a pilot could push the throttle past the stop, breaking the wire. The engine could be redlined for five minutes without damage.
NORTH AMERICAN P-51B (MUSTANG III): _____________________ _________________ ___________________ spec metric english _____________________ _________________ ___________________ wingspan 11.28 meters 37 feet wing area 21.65 sq_meters 233 sq_feet length 9.83 meters 32 feet 3 inches height 4.16 meters 13 feet 8 inches empty weight 3,380 kilograms 7,450 pounds max loaded weight 5,080 kilograms 11,200 pounds maximum speed 708 KPH 440 MPH / 380 KT service ceiling 12,770 meters 41,900 feet range with drop tanks 2,575 KM 1,600 MI / 1,390 NMI _____________________ _________________ ____________________P-51Bs finally reached squadron service in October 1943, when the USAAF 354th Fighter Group in England was equipped with the type. This assignment was something of a "snafu", however, since the 354th was part of the Ninth Air Force, which was focused on ground attack. Apparently someone in the Pentagon failed to get the word that the Merlin Mustangs were a different breed from the ground-attack Allison Mustangs.
The USAAF Eighth Air Force had begun daylight raids into Germany in early 1943, but by the fall of that year had been forced by murderous combat losses to give up such missions until long-range escort fighters became available. The Eighth desperately needed the new Mustangs, and so the 354th was immediately ordered to operate in support of Eighth Air Force long-range bomber missions, even though the group remained in the Ninth's chain of command.
P-51Bs began flying fighter sweeps over Europe in early December 1943, and were escorting bombers on raids by the middle of the month. On 13 December, Lieutenant Glenn Eagleston drew first blood with the P-51B, damaging a Messerschmitt Me-110 during a raid on Kiel. Eagleston would eventually become the top ace of the Ninth Air Force, claiming a total of 10.5 victories.
On 16 December, Lieutenant Charles Gumm claimed the P-51B's first actual kill, knocking a Me-110 out of the sky over Bremen. The days of the Luftwaffe savaging unescorted bomber formations were drawing to a close. That same month, the RAF formally received its first Mustang III, flying with RAF Number 65 Squadron, and would quickly equip other RAF squadrons with the new aircraft. RAF Mustang IIIs would be in principle dedicated to ground attack, but they participated in escort duties while the USAAF built up strength in the new fighter.
On 11 January 1944, Major James H. Howard of the 354th was on an escort mission over Germany in his P-51B, named "Ding Hao". Howard was a mild-mannered but highly experienced pilot who had scored 6.5 victories against the Japanese with the American Volunteer Group in China.
Howard had become separated from his flight when he saw a group of German fighters attacking a formation of B-17s. Although he was alone, Howard apparently regarded this as a "target-rich environment" instead of a threat, and dived into the fight without hesitation. He quickly shot down three German fighters, and then for the following half hour engaged in duels with the remaining Luftwaffe pilots. By the time the fight was over all his guns had jammed but one. With these kills, he became the first Mustang ace, and was awarded the Congressional Medal of Honor.
By early 1944, other USAAF fighter groups were forming up in England. Two Ninth AF fighter groups, the 357th and 363rd, were equipped with the type, though the 357th FG was traded to the Eighth AF in exchange for the 358th FG, which flew the Republic P-47 Thunderbolt. This exchange was apparently mutually satisfactory, since the Eighth AF needed P-51Bs for long-range fighter escorts, while the Ninth AF could make good use of the big, tough, and more heavily armed P-47 for ground attack.
Eighth AF fighter groups were also receiving new P-51Bs directly, beginning with the elite 4th FG. The 4th was the oldest and most experienced fighter group in the Eighth AF, having been formed out of three RAF "Eagle" squadrons, composed of American pilots in British service. The commander of 4th FG, Colonel Donald J.M. Blakeslee, had been leading 354th FG P-51Bs since their arrival. On his return to his own group, he promised his superiors that his pilots would be operational with the new fighter within 24 hours. They were all flying with the type by the next day, 25 February 1944.
The new Mustang quickly began to appear on other fronts. In February 1944, P-51Bs began flowing into USAAF 14th Air Force units in Burma, and in April, P-51Bs and Mustang IIIs began to arrive at USAAF and RAF squadrons in Italy.
As P-51Bs flew into combat, the deficiencies of the type were identified and gradually dealt with. There were engine problems, of course. The Merlin 61-series engines were pushing limits and had been pressed into combat as quickly as possible, as had the Mustang itself. Even when the engine worked fine, it took some getting used to for pilots who had flown Allison Mustangs, since the Merlin ran louder and rougher than the Allison, and in particular produced an unnerving THUMP! when the supercharger cut in or out. Working out the bugs and learning the right ways to fly with and maintain the engine took time.
One significant problem was the tendency of the 12.7 millimeter guns to jam. As in earlier Mustangs, the wing machine guns in the P-51B were canted onto their sides, and the sharp angle at which the ammunition fed into the guns could lead to jamming under high-gee maneuvers. This problem would require rethinking the armament scheme.
A particularly alarming problem, to say the least, was the occasional tendency of the wings to fall off during a high-speed dive. Ironically, Tommy Hitchcock, who had done much to promote the Merlin Mustang, was killed over England in a P-51B in this way in April 1944. These structural failures proved to be due to the tendency of wing ammunition doors or the main landing gear to open under high-gee conditions, producing excessive forces on the wing. These problems were eventually resolved.
One long-standing annoyance was the canopy scheme, which gave a poor view to the rear; prevented the pilot from getting a clear view ahead over the long nose in takeoff; could not be opened in normal flight; and was difficult to get out of in an emergency. The RAF came up with their own solution by replacing the three NAA canopy panels with a one-piece bubble "hood", similar to that used on the Spitfire, that slid back to the rear. The new canopy design was implemented by the British firm of R. Malcolm Limited, and consisted of one-piece blown Perspex bubble that could be easily refitted to the Mustang by field maintenance personnel. The "Malcolm hood" was refitted to most RAF Mustang IIIs, and was apparently fitted to some USAAF P-51Bs and even some of the old Allison Mustangs.
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Another problem was that, even with drop tanks, the Mustang still didn't have enough range to escort Eighth AF bombers all the way to Berlin and back. The USAAF had been testing a potential long-range fighter, the Fisher XP-75, that had proven unsatisfactory, and needed something immediately that could do the job. USAAF Colonel Mark Bradley, who had been in charge of testing the XP-75, told NAA's Dutch Kindelberger that there was some empty space in the rear fuselage of the Mustang, and that another fuel tank should to be put there.
NAA engineers devised a 322 liter (85 US gallon) tank that fit between the pilot's seat and the radio. This gave the Mustang the necessary range, solving one problem, if at the expense of creating another. The new fuel tank was added without concern for its effect on the Mustang's center of gravity. With a full fuel load, getting the fighter off the runway was downright dangerous, and the aircraft was only marginally controllable for the first hour or so that it took to drain the tank.
That had to do, there was a war on and something was needed right away, so the third tank was fitted to late-production P-51Bs. The British also made their own contribution to the range problem in the form of a new drop tank that accommodated 409 liters (108 US gallons) and which was made of plastic-impregnated paper. This sounds a little crazy, particularly since the fuel would rot the tank if left in it for more than eight hours. However, the paper drop tanks were perfectly effective, and were lighter and cheaper than metal drop tanks. Dropping them over German territory also did not provide the enemy with aluminum they could scavenge for their own war effort. Production rates of the paper drop tanks eventually reached 24,000 a month.
A 416 liter (110 US gallon) drop tank was also built, plus a 568 liter (150 US gallon) ferry tank. Information on these tanks is sketchy, but the ferry tank looked like a tub whose upper rim fit up against the wing, and so it appears it could not be dropped in flight.
The problems with misidentification with the Messerschmitt Bf-109 continued. White stripes were painted on the nose, wings, and tail, but with only limited effectiveness. On 10 February 1944, for example, Glenn Eagleston was shot up by a P-47 over Germany and only barely managed to make it back to England to bail out.
Before the year was out, the problem would be reduced by the simple measure of delivering Mustangs to England in natural metal finish. The USAAF wanted to take on the Luftwaffe, not hide from them, and eliminating the paint actually reduced aircraft weight and slightly improved performance. RAF Mustangs would continue to be painted in camouflage until near the end of the war.
While the bugs were worked out of the P-51B and its range extended, the USAAF and RAF built up new squadrons with the aircraft and put them to use. Using the new third fuel tank and drop tanks, on 6 March 1944, P-51Bs escorted Eighth AF B-17 Flying Fortresses all the way to Berlin for the first time.
This is a somewhat simple-minded description of the action that gives the impression that the Mustangs joined the bomber formations after takeoff from England and stayed with them through the entire raid. In fact, for escort missions, a number of fighter formations were sent to staged rendezvous points to join the bombers at specific intervals, with shorter-range aircraft like P-47s providing escort cover at relatively short ranges and the long-range P-51Bs handling the most remote legs of the mission.
On the 6 March Berlin raid, the P-51Bs got into a massed dogfight that a Fortress pilot called "one of the damnedest dogfights of the war. It was off to the right of us as we headed east and several thousand feet higher -- about one and a half miles away. It looked like a giant swarm of bees -- P-51s, Me-109s, FW-190s." This mission was not a complete success, as B-17 losses were heavy, but the USAAF would be back and would learn. Early on, bomber crews sometimes accused the fighter jocks of wanting to dogfight for the glory instead of protecting the bombers, and it took time for the bombers and fighters to learn to work in better coordination.
The logistics of long-range escort missions were difficult in any case. Getting a Mustang with drop tanks and a full fuselage tank off the runway was fearsome, particularly since the fighter groups didn't have the luxury of waiting for one aircraft to clear the runway before sending another out. The result was sometimes a hideous fireball on the runway, followed by an even more disastrous pile-up that incinerated men and machines.
Once airborne, P-51B pilots had to perform a tricky exercise in fuel management before they entered combat. Initially, USAAF procedure was to drain the fuselage tank before switching to the drop tanks, but this led to Mustang pilots discarding full drop tanks when they were forced to combat prematurely. The USAAF then reversed the procedure, instructing pilots to drain the drop tanks first. This was not entirely satisfactory either, since the Mustang was very hard to fly with a loaded fuselage tank, and ultimately to get out of this dilemma the USAAF was forced to limit the amount of fuel pumped into the fuselage tank to 246 liters (65 US gallons).
Despite these problems, the P-51B was proving extremely effective in air combat. One of the early stars was Don S. Gentile (pronounced "Jentilly") of the 4th FG's 336 Fighter Squadron. Flying his P-51B, "Shangri-La", Gentile was able to claim a total of 16 victories in March and early April 1944, all but one of them against Luftwaffe single-engine fighters. On 11 April 1944, Gentile was awarded the Distinguished Service Cross by General Dwight D. Eisenhower for his actions. Two days later, Gentile flew his Mustang into the ground while buzzing his home base. Gentile walked away unharmed, but "Shangri-La" was a total loss.
The RAF continued to use their new Mustang IIIs in the close-support role. Racks for eight 27.2 kilogram (60 pound) rockets were evaluated again, and while they once more imposed a performance penalty, the Merlin Mustang's higher performance made this more tolerable. Such rocket-firing Mustang IIIs were used in Italy.
By late spring 1944, NAA was moving P-51 production to the next variant, the improved P-51D, which would become the most heavily produced and best known of all the Mustangs. It was still the P-51B that actually led the USAAF challenge the Luftwaffe on its home ground. The P-51B was the most numerous Mustang in service well after D-Day, and by VE day was still fighting in large numbers. Some pilots who flew the P-51B regarded it as the best of the Mustangs.
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A total of 3,738 P-51Bs and P-51Cs were built. The RAF received 910 of them under Lend-Lease as Mustang IIIs. 91 of the USAAF total were fitted as reconnaissance aircraft, with two cameras installed, one ahead of the tailwheel and the other staring out the left side of the aircraft. This variant was designated "F-6C". The F-6C retained the four machine guns of the standard P-51B and often engaged in air combat. One USAAF F-6 pilot, Captain Clyde East, would become an ace, with 15 confirmed kills.
Some war-weary P-51Bs were converted by ground crews into two-seaters, for use as trainers or "hacks". These conversions could be extremely clean, with a second "razorback" canopy inserted into the rear fuselage immediately behind the first.
P-51D, P-51K "Mustang IV"
NAA was quick to recognize the deficiencies of the P-51B and come up with a new version to fix most of them.
Although the RAF remedied the poor rear view of the razorback Mustang with the excellent Malcolm hood, NAA decided on a different approach, though it was derived from British work as well. Colonel Mark Bradley had visited England in early 1943, and had seen the "bubble" canopies that the British had developed for the Spitfire and Typhoon.
The bubble canopies gave a pilot unobstructed all-round vision. Bradley returned to the US and pushed to get bubble canopies fitted onto American fighters. Republic quickly put one on a P-47, and Bradley flew the modified Thunderbolt to California to show it to NAA's Dutch Kindelberger. NAA very quickly came up with a plan to cut back the rear fuselage of the Mustang and mount a large bubble canopy over the cockpit. The canopy would slide open back over the rear fuselage. Two P-51Bs were pulled from the assembly line as proof-of-concept demonstrators, and the first bubble-top "XP-51D" (company designation "NA-106") took to the air on 17 November 1943.
The four-gun armament of the P-51B was also unsatisfactory, not merely because of its light firepower but because of the previously-mentioned tendency to jam due to the guns' installation at an angle. NAA engineers took a good look at the problem, and came up with a much better solution for the P-51D.
The new armament fit provided three 12.7 millimeter machine guns in each wing and allowed them to stand upright. The two outer machine guns were mounted side by side. The ammunition boxes for these two weapons were stacked in the wing outboard of the weapons, with the box for the outer gun on the bottom and the box for the middle gun on the top. The ammunition feed for the middle gun arched over the outer gun. Each of these boxes could store 270 rounds of ammunition.
The inner machine gun was set back of the two other guns, and was fed from an ammunition box stowed directly behind the boxes for the outboard guns. This box could store 400 rounds of ammunition. The middle gun could be removed so that the ammunition store from the outer gun could be increased to 400 rounds. This new armament fit helped greatly reduce jamming. Eventually, production P-51Ds would also be fitted with an ammunition belt power feed system that reduced the incidence of jamming still further.
Another improvement did much to increase the P-51D's lethality. Once again British engineering made a considerable contribution to the Mustang, this time in the form of the British Ferranti "GGS Mark IID" computing gyro sight, replacing the relatively simple Bell & Howell gunsights used to this time. The Ferranti sight, manufactured under license in the US as the "K-14", allowed the pilot to dial in the target wingspan and target range, and then told the pilot when he had a good shot at the target. The K-14 was regarded as a marvel of technology and greatly increased the pilot's accuracy in deflection shots. Later P-51D production would also feature AN/APS-13 tail warning radar, with rod antennas sprouting from the tailfin, to give warning of attack from the rear.
Traditionally, Mustangs had two pylons for bombs or drop tanks, but late production P-51Ds also had streamlined stubs for 7.62 centimeter (5 inch) "High Velocity Air Rockets (HVAR)". These rocket-firing Mustangs could carry ten HVARs, or six HVARs plus two bombs or two drop tanks.
Initial production P-51Ds used the Packard V-1650-3 engine, but late production would be uprated to the improved V-1650-7 engine. The P-51D used a four-bladed Hamilton Standard propeller, with some variation in propeller design in the course of production.
NORTH AMERICAN P-51D (MUSTANG IV): _____________________ _________________ ____________________ spec metric english _____________________ _________________ ____________________ wingspan 11.28 meters 37 feet wing area 21.65 sq_meters 233 sq_feet length 9.83 meters 32 feet 3 inches height 4.16 meters 13 feet 8 inches empty weight 3,466 kilograms 7,635 pounds max loaded weight 5,493 kilograms 12,100 pounds maximum speed 700 KPH 435 MPH / 380 KT service ceiling 12,770 meters 41,900 feet range with drop tanks 2,655 KM 1,650 MI / 1,435 NMI _____________________ _________________ ____________________Other changes included a wing with slightly greater chord at the root, plus stronger main gear to handle the aircraft's increased weight. One significant change was the addition of the dorsal fin extension to the tailfin, added after initial P-51D production. This compensated for yaw instability problems that had become increasingly troublesome with the introduction of the Merlin engine, the addition of the fuselage fuel tank, and the cut-back of the rear fuselage.
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Early Production P-51D (No DorsalFin)
By May 1944, P-51Ds were flowing from the production line in Inglewood to combat units in England, starting with the 4th FG. NAA's Fort Worth plant was also producing the version in quantity, though that production also included a variant named the "P-51K" whose only significant difference from the P-51D was a slightly smaller Aeroproducts propeller. This change was stipulated by the USAAF, which was concerned about the supply of the Hamilton Standard propeller. The Aeroproducts propeller was also lighter, but apparently was not completely satisfactory and production reverted to the Hamilton Standard propeller. Unless otherwise noted, all following comments about the P-51D also apply to the P-51K.
The P-51D and P-51K were provided to the RAF, which named them the "Mustang IV" and "Mustang IVA" respectively. However, the RAF had no desperate need for the new Mustang and didn't begin to put them into service until September 1944. The USAAF also flew reconnaissance versions of the P-51D and P-51K, named "F-6D" and "F-6K" respectively. The reconnaissance versions featured a camera fit much like that used in the F-6A, with two cameras just ahead of the tailwheel, and retained armament. Some P-51Ds would be converted to the reconnaissance configuration, and were known as "FP-51Ds".
The P-51D still had its problems. In fact, as its increased armament and other changes made it somewhat heavier than the P-51B, it had slightly inferior climb performance to the P-51B and was slightly slower as well, which is likely why some pilots thought the P-51B was the better aircraft.
Like the P-51B, the P-51D was difficult to handle with a full fuselage tank, and it had high stick forces under combat maneuvers. Worst of all, under such maneuvers it gave no warning of stall and could fly abruptly and wildly out of control. It was also difficult to bail out of, since air pressure tended to trap the pilot in his seat, and Mustang pilots had to learn the Luftwaffe trick of turning the aircraft over and falling out. However, the aircraft's virtues were such that these vices were forgivable, though not forgettable.
With a better field of view, greater firepower, and an improved gun sight the P-51D was a match for the Luftwaffe's piston-engine fighters. USAAF pilots were also assisted in air combat by another innovation, the G-suit, which guarded against pilot "blackout" during high-speed turns. The G-suit worked by applying pressure when needed to the pilot's abdomen and legs, preventing blood from pooling in the lower body. The British developed a hydraulic G-suit, known as the "Frank", but the Americans preferred their own, less cumbersome pneumatic G-suit, known as the "Berger". The Berger G-suit was available in quantity by June 1944 and put to good use by Mustang pilots.
With the P-51D, the USAAF achieved the decisive air superiority over the Reich that the P-51B had promised. Pressured by a war on two fronts and harassed from the air, Luftwaffe resistance began to crumble, and the USAAF cruised through the sky against fading opposition. Mustangs escorted the bombers to their targets and then strafed airfields on the way home, coming in at high speed just above the grass and in single line abreast to take the defenders by surprise.
Many USAAF pilots became "aces in a day" in the P-51D. On 12 October 1944, Lieutenant "Chuck" Yeager, at the start of a famous career, shot down five Messerschmitt Bf-109s on a single mission. Similarly, Captain Bill Wisner destroyed six Focke-Wulf FW-190s on an escort mission on 21 November 1944, while Lieutenant Claude Crenshaw shot down five FW-190s during the same escort mission.
On 30 August 1944, Major George Preddy was leading his flight to escort a bomber raid over Berlin when he shot down six Bf-109s. Preddy would become the highest-scoring Mustang ace, with a total of 24 victories. He was killed by "friendly" anti-aircraft fire on Christmas Day, 1944.
The Germans were running out of fuel, aircraft, and experienced pilots. Even the new jet fighters like the Messerschmitt Me-262 did them little good, since Allied fighters like the Mustang seemed to be everywhere all the time. While the Me-262 could outpace the Mustang in high-altitude combat, the Mustang could outturn the jet easily, making it no disastrous threat to an alert pilot, and could outlast the Messerschmitt, which had limited endurance. When a Me-262 came in for a landing, it was often bounced by lurking Mustangs.
On 7 October 1944, USAAF Lieutenant Urban Drew dived on two indistinct German fighters and shot them both down before he realized he had taken on a pair of Me-262s. On 4 November 1944, Walter Nowotny, the fifth-ranking German ace, with 258 kills, was attacked by P-51Ds as he approached the runway, and flew into the ground while taking evasive action. Mustangs destroyed three other Me-262s that day.
In the meantime, the RAF had been using their Mustang IVs to combat a different type of jet aircraft, the German V-1 "flying bomb", or "Doodlebug". After the V-1 attacks began in early summer, the RAF set up patrols of fast aircraft like the Typhoon, Spitfire, and Mustang to intercept them. These fighters would circle near the coast and were directed to a V-1 by a radar ground-control station. Intercepting the Doodlebug bombs could be tricky, since they were small and fast. Mustangs still accounted for hundreds of these weapons before the missile launch sites were overrun by the Allies in the early fall of 1944.
* The P-51Ds saw extensive service outside of Northern Europe as well. The Fifteenth Air Force in Italy featured several fighter groups flying the Mustang, in particular the 332nd FG. This fighter group consisted entirely of black American pilots, known as the "Tuskugee Airmen", or "Red-Tails" for the paint job on their fighters.
Fighter groups of the Fourteenth Air Force in the CBI had been flying P-51Bs but upgraded in part to P-51Ds in 1945. CBI P-51Ds were often field-modified for unusual stores configurations, such as two drop tanks and six 45 kilogram (100 pound) bombs; or four drop tanks; or 45 kilogram bombs and 36 small fragmentation bombs. They were also usually fitted with direction-finding loop antennas ahead of the tailfin for navigation on long missions.
Fifth Air Force Mustangs began to operate out of the Philippines in December 1944. One of the Fifth's pilots, Major William A. Shomo, was flying an F-6D over northern Luzon on 11 January 1945, when he ran into a swarm of Japanese fighters, including the Ki-61 "Tony" and formidable Ki-44 "Tojo". Shomo shot down seven of them, to be awarded the Congressional Medal of Honor for this feat.
The Seventh Air Force began to obtain P-51Ds on Iwo Jima beginning in March 1944, to be used to fly escort for Boeing B-29 Superfortress raids over Japan. The Mustangs flew their first mission over Japan on 1 April 1945. These missions were very difficult, with a round-trip distance of 2,400 kilometers (1,500 miles) over trackless ocean. A B-29 was assigned to each fighter group to provide navigation.
Iwo Jima's airstrips were very dusty and caused engine failures that could be deadly. Tropical storms were also very violent and hazardous. On 1 June 1945, a group of 148 Mustangs left Iwo Jima to rendezvous with B-29s for a raid on Honshu. The fighters ran into a weather front and lost 27 of their number in mid-air collisions and other accidents. 22 pilots died.
P-51D : Summing Up
7,956 P-51Ds and 1,500 P-51Ks were built by North American, more than all other models of Mustangs combined. Of these aircraft, 875 ended up as RAF Mustang IVs and Mustang IVAs.
The USAAF would credit about 5,000 air combat kills to Merlin Mustangs operating in Europe, a little less than half the total claimed, and these aircraft were also credited with destroying over 4,000 enemy aircraft on the ground, a little more than half the total claimed.
As with the P-51B, there were a number of field-modified two-seat conversions. The second seat was installed under the bubble canopy in place of normal radio gear. North American also designed a "formal" two-seat conversion with dual controls, and this variant was known as the "TP-51D". One such two-seater was used by General Dwight D. Eisenhower as a fast observation aircraft to allow him to personally inspect the Normandy beachhead in June 1944. In the 1950s, the Temco company would also convert 15 F-51Ds (as the P-51D was designated by that time) to a two-seat trainer configuration designated the "TF-51D", featuring twin tandem cockpits.
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Of course, given the great numbers and wide use of the P-51D, there were a few oddball variants. One was fitted with an arresting-hook "stinger" and used for carrier trials on the USS SHANGRI-LA in November and December 1944, with Navy Lieutenant Robert Elder at the controls. This aircraft was designated the "ETF-51D". The US Navy was very interested in a long-range carrier-based fighter, but although the trials went well, the capture of Iwo Jima and American air superiority over the Pacific eliminated the need for a naval Mustang.
There was actually a jet-powered version of the P-51D, sort of. After the war a P-51D was modified as a ramjet test platform, with one Marquardt ramjet attached to each wingtip. The piston engine was retained, of course, since a ramjet has to be moving at relatively high speed before it can be started. The ramjet-boosted Mustang flew extensive tests until August 1948, when one of the ramjets flamed out. The test pilot tried to relight it, and ramjet exploded in a fireball. The pilot managed to turn the aircraft over and bail out, leaving the Mustang to fall to earth.
XP-51F, XP-51G, XP-51J, P-51H, P-51L, P-51M
The P-51 was a relatively heavy aircraft even for its size, mostly due to the fact that it had been designed in a hurry and with an emphasis on ease of manufacture. Edgar Schmued had traveled to England to inspect Supermarine's factories and study captured Luftwaffe aircraft, and felt that much could be done to reduce the aircraft's weight.
In early 1943 NAA began a project to develop a "lightweight" Mustang, with the company designation "NA-105". The new Mustang that resulted had few parts in common with earlier versions, featuring an even more streamlined wing, a redesigned cooling system, a longer but more aerodynamically efficient bubble canopy, plus extensive minor changes to cockpit layout, control surfaces, landing gear, and so on.
The troublesome fuselage fuel tank was deleted. In compensation, the integral wing tanks were increased to a capacity of 386 liters (102 US gallons) each. Machine-gun armament was reduced from three to two 12.7 millimeter Browning guns in each wing, with each gun provided with 440 rounds of ammunition. Interestingly, the lightweight design reverted to a three-bladed propeller.
Two lightweights were initially built as "XP-51Fs", followed by a third produced in RAF colors and shipped to Britain as a "Mustang V". Bob Chilton made the first flight in an XP-51F on 14 February 1944. The aircraft was very fast, with a top speed of 750 KPH (466 MPH) at altitude, but its handling left something to be desired.
Two more lightweights were built using the experimental Rolls-Royce Merlin 145M engine, driving a five-bladed Rotol propeller. These two were known as "XP-51Gs", and the first one flew in early August 1944. The five-bladed propeller was apparently unsatisfactory, since it was immediately replaced with an Aeroproducts four-bladed propeller. One of the XP-51Gs achieved a top speed of 796 KPH (495 MPH) some months later, making it the fastest of all the Mustangs. An XP-51G was provided to the RAF for flight tests. It was not produced due to limited availability of the Merlin 145M.
NAA also developed a lightweight Mustang named the "XP-51J" that featured (for comparative studies) an Allison V-1710-119 engine, which had a two-stage supercharger to improve high altitude performance and a water-injection system for boost power. This aircraft had the carburetor intake moved under the fuselage to draw air from the belly airscoop, and as a result the XP-51J had a cleanly streamlined nose, unbroken by any significant openings. It gave the aircraft the look of a custom-built air racer. Two XP-51Js were built, but only one actually flew, in April 1945. Performance did not meet expectations due to engine problems, and so the second aircraft was shipped to Allison, where the engine was scavenged for parts for engineering studies.
Interestingly, one of the lightweights, an XP-51G, has survived to the present. It is unlikely that it will ever fly, since many of its parts are unique and unavailable.
Although the various NA-105 lightweights were not regarded as entirely practical for field use, the ideas incorporated in them were used to enhance the P-51D design, leading to the final production version of the Mustang, the "P-51H".
This aircraft was powered by an uprated V-1650-9 engine, featuring water-methanol injection for power boost and driving a four-bladed propeller. It had a lengthened fuselage similar to that of the XP-51F, a taller tailfin to deal with lateral stability problems, and a cockpit that was slightly raised to provide a better forward field of view.
The P-51H reverted to six wing guns. The fuselage fuel tank made a comeback as well, though it was sensibly smaller than that of the P-51B and P-51D, with a capacity of 191 liters (5O US gallons).
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The P-51H was one of the fastest piston fighters ever to reach full operational service, with a level speed of 784 KPH (487 MPH). Thousands of P-51Hs were ordered, with the company designation "NA-126", but the end of the war and the rise of the jet fighter reduced the actual quantity produced to 555.
As with earlier versions of the Mustang, the NAA plant in Fort Worth produced the P-51H with a different model number, "P-51M" (or "NA-124"), though only one such aircraft was actually built. A minor variation of the P-51H designated "P-51L" (or "NA-129") was considered, which was to feature an improved V-1650-11 engine with fuel injection, but none were actually built.
NORTH AMERICAN P-51H: _____________________ _________________ ____________________ spec metric english _____________________ _________________ ____________________ wingspan 11.28 meters 37 feet wing area 21.65 sq_meters 233 sq_feet length 10.16 meters 33 feet 4 inches height 3.37 meters 11 feet 1 inch empty weight 3,193 kilograms 7,040 pounds max loaded weight 5,221 kilograms 11,500 pounds maximum speed 785 KPH 485 MPH / 425 KT service ceiling 12,770 meters 41,900 feet range with drop tanks 1,866 KM 1,160 MI / 1,010 NMI _____________________ _________________ ____________________The P-51H saw little or no combat. It was quickly replaced by the Lockheed P-80 Shooting Star in the air superiority role. In the years immediately following WW II, the USAAF standardized on the P-51D for close support, since the P-51H was not regarded as being as robust.
A total of about 15,600 Mustangs of all types were built by North American, not including the aircraft built in Australia by Commonwealth Aircraft Corporation and discussed in the next chapter. Almost two-thirds of these were P-51Ds, and that type survives today as the most common Mustang.
A P-51 cost about $51,000 USD in WW II dollars. Even allowing for inflation of about a factor of ten to the present day, it is an indication of the evolution to greater sophistication and expense of modern fighter aircraft that a half-million dollars wouldn't even buy a light attack aircraft, much less a first line fighter.
Variants Of The P-51
The Twin F-82 "Mustang" / Postwar "Mustangs"
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North American F-82G Twin Mustang
The Mustang was one of the weapons that won World War II for the Allies. Although outdated in the postwar period, it nonetheless continued to provide good service and evolved in some interesting directions, such as the "F-82 Twin Mustang" and the experimental turboprop "PA-48 Enforcer".
The F-82 Twin "Mustang"
The Twin "Mustang"
XP-82 & XP-82A / P-82B / P-82C & P-82D
The long range of the Mustang led to a problem that hadn't been appreciated in earlier fighters: pilot exhaustion on long-range escort missions. Sitting in a relatively tight cockpit for six or seven hours, nursing a powerful aircraft along, and enduring the anxiety and stress of air combat was enough to drain a pilot completely. Sometimes pilots had to be helped out of the cockpit when they returned to base, and the combination of poor English weather and pilot fatigue often led to accidents.
The USAAF was interested in a fighter with even longer range than the P-51D to operate over the wide expanses of the Pacific, particularly as as escort for the long-range Boeing B-29 Superfortress bomber. The need to deal with pilot fatigue and provide longer range meant a twin-engine, two-seat aircraft, but traditionally twin-engine fighters were no match for single-engine fighters.
In November 1943, NAA's Edgar Schmued came up with an interesting proposal to address the problem: link two Mustangs together with a common center wing and horizontal stabilizer. He had actually been tinkering with the idea as far back as 1940. On 7 January 1944, Hap Arnold visited NAA's Inglewood factory and was shown the concept. Arnold was enthusiastic, and gave NAA the go-ahead to proceed for the design, which the company designated "NA-120". In early February 1944, the USAAF ordered four flight prototypes and a static test item of the new design. Two of the flight prototypes were designated "XP-82s" and were to be powered by variants of the Packard V-1650 Merlin, and two were designated "XP-82As", to be powered by variants of the improved Allison V-1710-119 engine with two-stage supercharging.
The first of two XP-82s flew on 16 June 1945, with NAA test pilot Joe Barton at the controls. Barton had actually tried to make the first flight on 25 May, but the machines absolutely refused to get off the runway, and the first actual flight was performed with a half-fuel load. The design engineers were frantic, but it turned out that the engines, which contrarotated, had been installed so that the props swept upward towards the center wing section. This stalled the center wing section. The engines were quickly reversed, and on 26 June the XP-82 took off and flew more or less as it had been designed to, much to everyone's relief. Only one of the XP-82As was actually completed, and was rolled out in the late summer of 1945.
The common center wing section housed all the XP-82's gun armament, consisting of six 12.7 millimeter Browning machine guns with 440 rounds per gun. The center wing section featured a slotted flap running the length of the trailing edge. The wing area of the XP-82 was substantially less than that of two Mustangs, and so the wing had to be strengthened to handle higher wing loading. Longer two-piece ailerons with hydraulic power boosting were fitted to the outer wings to improve roll response.
The XP-82 could be fitted with a total of six stores pylons, two on each outer wing and two on the center wing section, for bombs, HVAR rockets, or drop tanks. Up to 1,800 kilograms (4,000 pounds) of stores could be carried. The center section could also carry a pod for night-fighting radar, machine guns, or reconnaissance cameras. Radar pods would receive further development, as explained below. A gun pod carrying eight 12.7 millimeter Browning guns was developed, but never fielded. A reconnaissance pod was apparently built, but saw little or no use.
The XP-82 was big, 3.1 meters (10 feet 2 inches) longer than a P-51D, and the dorsal fin extension was enlarged to improve yaw stability. There was actually very little parts compatibility between the XP-82 and a single-engine Mustang. The XP-82 had fuel tanks in the outer wings and in each fuselage, giving it a big internal fuel capacity of 2,180 liters (574 US gallons), and corresponding long range. As mentioned, the twin Packard Merlin engines of the XP-82 rotated in opposite directions, in order to compensate for torque, and so the aircraft was fitted with left-handed and right-handed engines, designed "V-1650-23" and "V-1650-25".
Landing gear had to be revised and strengthened to handle the greater weight. The main gear was hinged in the fuselage, and retracted across the fuselage into the common center wing. The fuselage tailwheel was retained, giving the Twin Mustang an unusual "four point" stance on the ground. The cockpits were largely redesigned from the single-seat Mustang. The command pilot flew in the left cockpit, which was fully equipped. The copilot occupied the right cockpit, with more austere controls to allow him to spell the copilot when need be. An interceptor version with one cockpit faired over was considered, but nothing came of the idea.
The XP-82A was generally identical to the XP-82, except for Allison engine fit. As with the XP-82, the engines had to be provided in "left handed" and "right handed" versions, and were produced as the "V-1710-143" and "V-1710-144".
The initial XP-82 prototypes demonstrated impressive performance in early tests. The new aircraft had a top speed of 776 KPH (482 MPH) and a range on internal tanks of 2,237 kilometers (1,390 miles). With four drop tanks installed, the range was 5,550 kilometers (3,445 miles).
The USAAF had enough confidence in North American to order 500 "P-82B Twin Mustangs" in March 1944, well before the XP-82's first flight. These were Packard Merlin powered aircraft, identical to the XP-82 except for improved machine guns. The contract was cut at the end of the war, and only 20 were actually delivered, in late 1945 and early 1946. These aircraft were used for training and evaluation, except for two of them that were diverted for experiments.
On 28 February 1947, a P-82B named BETTY JO, the ninth production item, piloted by Lieutenant Colonel Robert Thacker (Betty Jo was his wife) and Lieutenant John Ard, set a record for unrefueled flight in a piston fighter, flying from Hickam Field in Hawaii to La Guardia Airport in New York in about 14.5 hours. This aircraft had been stripped down, modified with additional internal fuel tanks, and fitted with four oversized 1,150 liter (310 US gallon) drop tanks. The total distance covered was 7,998 kilometers (4,968 miles) and the average speed was 559 KPH (347 MPH). This was faster than the top speed of most combat aircraft at the beginning of WW II.
The two aircraft that had been diverted from production were modified as prototype night fighters, with the designations "XP-82C" and "XP-82D". Both aircraft featured a search radar enclosed in a pod on the center wing section. Since the radar had to be set in front of the propellers to ensure that it had a clear field of view, the pod was very long and mounting it was troublesome. The pod was referred to as a "pickle" or a "dong". The XP-82C carried SCR-720C search radar, which had been used on the Northrop P-61 Black Widow night fighter. The XP-82D carried the less powerful but lighter, and so less difficult to mount, AN/APS-4 radar. Radar operator gear was installed in the right cockpit.
The P-82B and its experimental night-fighter derivatives were the last Merlin Mustangs produced. The last Merlin-powered Twin Mustang would be withdrawn from service in December 1949.
The Twin "Mustang"
F-82E / F-82F, F-82G, & F-82H
While the Merlin-powered Twin Mustangs derived from the XP-82 were only used experimentally or as trainers, the USAAF went ahead to production and operational use of derivatives of the Allison-powered XP-82A.
The USAAF knew that the jet fighter was the way of the future, but early jets didn't have the range for long-range escort missions. In February 1946, the USAF ordered 250 Allison-powered "P-82Es" as interim long-range escort fighters. This was soon changed to 100 P-82Es, plus 150 night-fighter versions of the Twin Mustang, as detailed below. First flight of the P-82E was on 17 February 1947. In 1947, the US Army Air Forces became the US Air Force, and fighters were redesignated with an "F" for "fighter" instead of the archaic "P" for "pursuit". All P-82s became "F-82s" as a result.
Production F-82Es were slow in arriving. The problem was the updated Allison V-1710 engine. The Allison was selected because Packard had to pay Rolls-Royce a $6,000 USD royalty for every V-1650 the company produced. During the war, Rolls Royce had been lenient about license fees, but after the end of the conflict Britain's economy was in the dumps and the royalty fee skyrocketed. There was also the fact that General Motors, which owned Allison, had a 40% share in NAA. GM had not been happy with the Mustang's switch to Merlin power during the war, but Allison production for other aircraft such as the P-38 Lightning was strong and GM had not been in a position to protest. With the war over, aircraft production took a dive and GM wanted to sell more Allisons. There were few other reasons to use the Allison engine, since even the two-stage supercharged Allison V-1710 was inferior in power-to-weight ratio to the Merlin.
The souped-up Allison engine was also temperamental and unreliable, and Allison couldn't deliver product in quantity. NAA had completed the 100 F-82E airframes by April 1948, but wasn't able to deliver them all for another year due to engine shortages. In service, the Allison-powered F-82Es were marginally slower than the Merlin-powered F-82Bs and the reliability problems persisted. The V-1710 became known as the "Allison time bomb" due to engine failures. Spark plug fouling from backfiring was particularly acute, and spark plugs were often swapped after a single flight.
NAA engineers modified some Allison engines with Merlin components and fixed most of the problems, but Allison took a "not invented here" attitude and insisted on applying their own fixes, which never quite worked out. Given the small production run of the Twin Mustang, even the steep license fee Rolls Royce was demanding for the Merlin was a bargain compared to all the troubles the USAF had with the Allisons. Pilots still found the machine pleasant to fly because its performance was so good even when its engines couldn't be run at their top ratings without trouble. They could lose an engine and hardly notice it. The Twin Mustang was also very agile for an aircraft of its size, and was a very stable gun platform. The battery of guns mounted in the center wing section provided highly focused firepower.
The F-82Es were externally indistinguishable from the F-82As except for minor details. One of the giveaways was the engine exhaust stacks. On the Merlin-powered aircraft, there were six exhaust stacks on each side. On the Allison-powered aircraft, there were duplicate exhaust stacks for each cylinder, for a total of 12 exhaust stacks on each side.
The F-82Es were assigned to Strategic Air Command and flew long-range demonstration missions to show off their capabilities, but they were an interim type indeed. Phaseout began in March 1950, less than a year after the last one was delivered, and was completed by July. Mid-air refueling promised to give jet fighters the range they needed to do the Twin Mustang's long-range escort job.
The night-fighter versions of the Twin Mustang achieved a bit more distinction in service. In September 1946, the USAAF had ordered 100 "P-82Fs" with AN/APG-28 radar, an improved version of the AN/APS-4 radar used on the P-82D, and 50 "P-82Gs" with SCR-720C radar. These aircraft were Allison powered. Interesting, the big radar pod imposed little performance penalty.
The F-82Fs and F-82Gs, as they would be known in service, also featured marker and radar beacons, plus AN/APS-13 tail warning radar. Before either type was delivered, the USAAF came up with a new requirement for an all-weather fighter for operations in Alaska. Nine F-82Fs were refitted with the SCR-720C radar, essentially turning them into F-82Gs, and both these aircraft and five F-82Gs were fitted with cold-weather gear, including improved heating systems. These were known as "F-82Hs", and were the last Mustangs ever produced by NAA.
NORTH AMERICAN F-82G TWIN MUSTANG: _____________________ _________________ ___________________ spec metric english _____________________ _________________ ___________________ wingspan 15.62 meters 51 feet 3 inches wing area 37.9 sq_meters 408 sq_feet length 12.92 meters 42 feet 5 inches height 4.21 meters 13 feet 10 inches empty weight 7,256 kilograms 15,997 pounds max loaded weight 11,744 kilograms 25,891 pounds maximum speed 740 KPH 460 MPH / 400 KT service ceiling 11,857 meters 38,900 feet combat radius 1,634 KM 1,015 MI / 885 NMI _____________________ _________________ ____________________The night-fighter Twin Mustangs went into service primarily as interim replacements for the P-61 Black Widow until jet night fighters were available. These Twin Mustangs soldiered on a few more years, until the F-82Hs were finally withdrawn in 1953. They were the last prop-driven air-combat fighters in service with the USAF.
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During their short lifetime, the F-82s achieved one major distinction: holding the fort in Korea until reinforcements arrived. Three squadrons of F-82Gs were operating in Japan as part of the 347th Fighter (All Weather) Group, when North Korea invaded South Korea on 25 June 1950. The F-82Gs were the only aircraft available in Japan that had sufficient endurance to fly to the battle area and operate for hours over the evacuation centers at Kimpo and Inchon. On 27 June, Lieutenant William Hudson and his radar operator, Lieutenant Carl Fraser, scored the first air-to-air kill of the Korean War, shooting down an La-11. Lieutenant Charles Moran shot down a Yak-9 a short time later, and Major James Little increased the day's score to three by destroying an La-7.
The North Korean Air Force had no advanced jet aircraft at the time, and the F-82Gs and Lockheed F-80 Shooting Stars quickly cleaned the North Koreans out of the sky. The F-82Gs switched their mission from air combat to night interdiction, using bombs and HVAR rockets to destroy North Korean armor and other targets.
Eventually, the night interdiction mission was taken over by the Douglas B-26 Invader, which was more heavily armed and better suited to the role. The last assignment of the F-82Gs in Korea was to hunt down low-flying PO-2 biplanes that the North Koreans used for night harassment raids, but this was an exercise in frustration as the nimble biplanes were almost impossible to find, much less shoot down. The F-82Gs were finally replaced by Lockheed F-94B Starfires in 1952.
The American Confederate Air Force warbird group actually operated a rare F-82E in air shows in the 1980s, painted black to resemble an F-82G night fighter, but the aircraft was lost in an accident in 1985. There are sketchy reports of other surviving Twin Mustangs, but no reports of existing airworthy examples.
"Mustangs" In Korea
Although the F-82G served an important role in the first few weeks of the Korean conflict, it faded into the background once the US arrived in real force. In contrast, the old P-51D, by then redesignated "F-51D", was a star player through the first year of the war, back in the original Mustang assignment of "mudfighter".
After the end of WW II, piston-engine fighters were rapidly phased out of front-line service in favor of new jet fighters, such as the P-80 Shooting Star. The USAAF retained a few squadrons of P-51Hs, but the older P-51Ds were passed on to the Air National Guard (ANG). As late as 1952, the ANG would still have 68 squadrons flying the Mustang, though the last of them would be gone in 1957.
Most of the remaining Mustangs were either sold to foreign operators or scrapped. In the early summer of 1950, the USAF had three fighter groups operating in Japan that had converted from the F-51D to the F-80, and the old F-51Ds were sitting in storage, waiting to be scrapped. When the war broke out on 25 June, the USAF realized that the F-51Ds were what was needed to help stem the North Korean offensive. The North Koreans, as noted, had no advanced aircraft, and the F-51D had better endurance and warload than the F-80, though some Air Force officers worried with good reason about the Mustang's well-known vulnerability to ground fire. The P-51D could also operate more effectively than jets from primitive airfields. The three fighter groups traded their F-80s back in for their old F-51Ds and were thrown into the battle.
The USAF also grabbed 145 F-51Ds from ANG units and rushed them to Japan on the carrier USS BOXER, which arrived in Tokyo on 23 July 1950. Two squadrons were equipped with the new arrivals, and were quickly flying dozens of sorties a day from rough airstrips behind the front lines in Korea. A squadron each of Mustangs was provided by Australia and South Africa. F-51Ds were also supplied to the South Koreans.
The Mustangs struck at enemy columns with machine guns, bombs, HVARs, and napalm. Since the bombs and rockets were not particularly accurate, napalm was the preferred weapon for attacking formidable North Korean T-34 tanks, since a napalm bomb saturated a wide area with fire. The attacks were made at low level, however, and Mustang attrition was high. The notorious vulnerability of the Mustang's cooling system was a particular problem. Some thought was in fact given to fielding a squadron of Republic F-47N Thunderbolts, which were better close-support aircraft, but the aircraft were simply not available.
By the fall of 1950, the North Koreans were on the run, and the Americans and their allies were pursuing them into North Korea. Mustangs ranged freely with little air opposition. They claimed five kills during this time, their only air combat victories of the war.
In early November, Mustangs began to encounter fast-jet MiG-15s, and it was only due to the skill of the Mustang pilots and the inexperience of the enemy that the F-51Ds were able to survive. By the time cold weather set in, Chinese forces were pouring into North Korea, driving the Americans and their allies south in a fast retreat that stopped at the South Korean border. The front lines stabilized there and a static war of attrition followed.
With the USAF countering the MiG-15 with the North American F-86, the air combat environment became increasingly too dangerous for piston engine fighters like the F-51D. Most units equipped with the Mustang converted to jets, and by the end of the war in July 1953, only one USAF squadron and some South Korean units were operating the Mustang.
A total of 194 F-51Ds were lost in the war. 172 were destroyed by ground fire, 10 were shot down by enemy aircraft, and 12 were lost to unreported causes. This is said to be the highest loss ratio of any aircraft operated by the Americans and their allies in the Korean War.
The "Mustang" In Foreign Service
Ironically, the Chinese also operated F-51Ds themselves in the Korean War, though it appears these aircraft never encountered USAF or allied F-51Ds. These Chinese Mustangs had originally been supplied to Chiang Kai-Shek's Nationalists, but had come into the hands of the Communist Chinese after their victory over the Nationalist forces.
They were only one of the many countries to operate the Mustang during WW II or to obtain surplus P-51s in the post-war years. Of course, the Mustang was flown in World War II by the British RAF and Royal Australian Air Force (RAAF), with Canadian and Polish units operating the type as elements of the RAF.
Britain itself abandoned their Mustangs shortly the end of the war. Under the terms of Lend-Lease, the British were required to pay for them if they kept them, and the RAF had plenty of late-mark Spitfires to meet its needs. In principle they were to have been returned, but in fact they were simply scrapped since the Americans didn't want them back.
Canadian Mustang units had mostly moved on to Spitfires by the end of WW II, but in 1945, the RCAF bought 100 P-51Ds and kept them in service in operational and training roles until the mid-1950s. The Australians, as discussed in the next section, actually built Mustangs of their own, and in fact had more of them than they knew what to do with at one time, though several Australian squadrons were to put the Mustang to good use in Korea.
The New Zealanders ordered 370 Mustangs before the end of WW II, but with the termination of hostilities only 30 were ever delivered to the RNZAF. These would operate into the 1950s.
South Africa had flown the Mustang during WW II, but the squadron provided by that country as part of the United Nations effort in Korea, mentioned earlier, was supplied with F-51Ds by the USAF and operated under general USAF direction. The SAAF unit was Number 2 Squadron, known as the "Flying Cheetahs".
A few Mustangs were captured during WW II by the Germans and pressed into Luftwaffe service as comparative evaluation aircraft. Ten P-51s also made forced landings in Sweden and were interned. The Swedes found the type very much to their liking -- more on this a bit later.
Before the end of WW II, 40 P-51Ds were provided to the Dutch, and after the war operated in the Dutch East Indies, fighting nationalist insurgents. The insurgents won and formed the state of Indonesia in 1949, which inherited two squadrons of the Mustangs, plus other aircraft, from the departing Dutch. The Indonesians would operate the type in internal conflicts into the 1950s.
The P-51Ds delivered to the Chinese Nationalists were also provided before the end of WW II, with some falling into Communist hands as mentioned, and more were provided to the Nationalists in 1949. They were flown well into the 1950s.
Of the ten P-51s that made forced landings in Sweden during WW II, four of them, two P-51Bs and two P-51Ds, were pressed into Swedish service as the "J-26". Before VE day, the Swedes ordered 50 more P-51Ds, eventually increasing their order to 157 aircraft. The first were delivered in April 1945, with the rest of the deliveries over the following three years. 12 were fitted for reconnaissance under the designation "S-26". All were sold in the early 1950s.
The Swiss acquired 100 F-51Ds in 1948, allowing the Swiss Flugwaffe to finally get rid of its antiquated Bf-109s. The Mustangs were a stop-gap as the Flugwaffe re-equipped with the de Havilland Vampire, which replaced the last Swiss Mustang in 1956.
The French Armee de l'Air operated some P-51s and F-6s for a short time after the end of the war, and the Italians operated 48 F-51Ds from 1948 through 1953.
The Israelis obtained two Mustangs in 1948 and used them in their war of independence. The first combat mission in one of these Mustangs was flown by Gideon Lichtman, a USAAF veteran who had flown the type in the Pacific theatre. In 1952, the Israelis bought 25 more F-51Ds from Sweden, and used them for close-support missions during the 1956 Suez war. Once again, the Mustang proved able to wreak destruction on an enemy with its machine guns, rockets, and napalm, but also as before the aircraft proved vulnerable to ground fire, and a third of them were lost in action. They were phased out of service over the next few years.
In Asia, as mentioned the South Koreans operated the type, as did the Philippines, which used them in counterinsurgency operations. The Mustang proved particularly popular in Latin America, and was operated by a number of Latin American nations. The United States wanted to provide friendly Latin American nations with surplus F-47 fighters, but there were plenty of Mustangs available and they were cheap. Mustangs were phased out of service in most Latin American countries through the 1970s.
Australian "Mustangs"
"The Kangaroo"
The only country besides the US to build the P-51 was Australia, but no Australian-built Mustangs saw combat in World War II. Commonwealth Aircraft Corporation (CAC) of Australia obtained a license to build the P-51D in 1944, beginning with the assembly of kits provided by NAA. 80 Mustangs were built from kits and given the designation "CA-17 Mustang XX", with the first CA-17 flying in April 1944.
CAC completed 120 Mustangs of their own as well, including:
40 "CA-18 Mustang 21s", which were duplicates of the P-51D.
14 "CA-18 Mustang 22s", which were fitted with a reconnaissance camera.
66 "CA-18 Mustang 23s", which used Rolls-Royce Merlins instead of Packards.
* CAC also built an advanced piston fighter named the "CA-15", powered by the Rolls-Royce Griffon engine, that clearly had Mustang influence though it could hardly be confused as a variant of the type. It looked something like a mutant Mustang on steroids.
The CA-15 began life in 1942 with studies for a follow-on to the Commonwealth Boomerang, a fighter that the Australians had put together hastily at the beginning of the war, using the North American T-6 Texan trainer as a starting point. The Boomerang was a much better machine than could have possibly been suggested by its humble origins and provided excellent service in the South Pacific theater, but there was no way to make much more of it than it was.
Further studies on a next-generation fighter continued through 1943, though as CAC was working towards Mustang production at the time, the company didn't have many resources to spare and the investigation didn't go anywhere in a hurry. The RAAF finally issued a specification in 1944, calling for a much more capable machine than the Mustang.
Commonwealth originally considered using a turbocharged Pratt & Whitney R-2800 Double Wasp air-cooled double-row radial engine, but there were doubts that the Australians could get their hands on such engines in adequate numbers. CAC then turned to the Rolls-Royce Griffin water-cooled vee inline engine. In 1945, CAC decided to build a prototype of the "CA-15" with a turbosupercharged Griffin 61 engine with 1,520 kW (2,035 HP) at altitude, and obtained two Griffin 61s from Britain on loan. Production was to use the more powerful Griffin 125, then under development,
A general verbal description of the CA-15 matches that of the P-51D almost perfectly. The CA-15 was a low-wing, all-metal fighter with a vee inline engine driving a four-bladed prop; taildragger landing gear, with the main gear pivoting in the wings toward the fuselage and a retractable tailwheel; a cooling scoop under the fuselage; and a bubble canopy. Armament fit was to be three 12.7 millimeter Browning machine guns in each wing, for a total of six guns, though other gun fits were considered; a single stores pylon under each wing for a 450 kilogram (1,000 pound) bomb or a drop tank, for a total of two stores pylons; or five rails under each wing for rocket projectiles, for a total of ten rails.
Click on Picture to enlarge
However, the CA-15's proportions were entirely distinct from those of the Mustang, and in fact the CA-15 also had a certain resemblance to the Republic XP-72 derivative of the P-47 Thunderbolt. One of the most noticeable oddities was the undersized bubble canopy, which looked like something that would be fitted to an air racer.
Initial flight of the CA-15 was on 4 March 1946, with test pilot Jim Schofield at the controls. Trials showed the machine, which was informally named the "Kangaroo", possessed excellent performance, though its controls were on the heavy side and it unsurprisingly demonstrated strong propeller torque on takeoff. Trying to get up into the cockpit to fly the thing in the first place was a bit of chore as well.
COMMONWEALTH CA-15 "KANGAROO": _____________________ _________________ ____________________ spec metric english _____________________ _________________ ____________________ wingspan 10.97 meters 36 feet wing area 23.5 sq_meters 253 sq_feet length 11.04 meters 36 feet 2 inches height 4.32 meters 14 feet 2 inches empty weight 3,420 kilograms 7,540 pounds max takeoff weight 5,597 kilograms 12,340 pounds max speed at altitude 720 KPH 450 MPH / 390 KT service ceiling 11,900 meters 39,000 feet range, internal fuel 1,850 kilometers 1,150 MI / 1,000 NMI _____________________ _________________ ____________________A mechanical failure led to a wheels-up landing on 10 December 1946. The pilot, Lee Archer, was unhurt, but the aircraft was badly damaged. By this time, jet fighters were clearly the way of the future, and CAC didn't get the CA-15 flying again until the spring of 1948. On 25 May, Archer dropped the Kangaroo into a dive and then leveled out, to set a speed record of 808.2 KPH (502.2 MPH) for the machine.
Performance would have been even better had the Double Wasp or Griffon 125 been fitted, but even at that any leading-edge jet fighter of the time could leave the Kangaroo in the dust. The CA-15 performed limited further test flights until the spring of 1950, when it was finally grounded due to lack of spares and then dismantled. The Griffon engines were returned to Britain.
"Cavalier" Conversions / The Enforcer
Even in the 1960s, there were those who felt the Mustang still had plenty of potential. One of these was David B. Lindsey JR, who established a company named Trans-Florida Aviation, which rebuilt several Mustangs into a two-seat "executive transport" named the "Cavalier". The Cavalier Mustang attracted enough attention to lead Lindsey to rename his company "Cavalier Aircraft Corporation" in 1962, and acquired the Mustang type certificate and tradename from North American.
The Cavalier Mustang was available in a range of versions, including the "750", "1200", "1500", "2000", and "2500". They were all very similar, the main difference between the variants being an increase in fuel capacity up the numbering sequence, with the Cavalier 2000 and 2500 adding fixed wingtip tanks with a capacity of 416.5 liters (110 US gallons) each. Cavalier also appears to have fitted out aircraft as per user request, making most of them custom jobs to a degree.
Click on Picture to enlarge
In 1967, Cavalier developed an updated Mustang for the counter-insurgency (COIN) role. The "Cavalier Mustang II" was a rebuilt P-51D, with a new Packard Merlin V-1650-7 engine; improved avionics; the taller tailfin used on the F-51H; fixed wingtip fuel tanks as per the Cavalier 2000 and 2500; and a reinforced wing to support a total of eight stores pylons, permitting a total stores load of 1.8 tones (4,000 pounds). It also featured a second seat for an observer behind the pilot. Images of Mustang IIs seem to show that they had a canopy with a bulge in the rear to provide headroom for the back-seater, but it is unclear if this was a standard fit.
As with the Cavalier Mustang, the company seems to have manufactured a number of variations on the Mustang II, building them with such features as required by a specific order. It is also not clear if they were all actually referred to as "Mustang IIs", but as the matter is both complicated and not very interesting, all the Cavalier military Mustang conversions are referred to by that name here for simplicity.
That same year, 1967, the USAF ordered a batch of Mustang IIs for delivery to friendly Latin American and Asian nations under the US Military Assistance Program (MAP). The next year, 1968, the US Army ordered two more Mustang IIs as chase aircraft for the YAH-56 Cheyenne helicopter gunship program, and used them in short-lived experiments in close-support applications after the Cheyenne program was cancelled. The USAF ordered a second batch of Mustang IIs for MAP in 1972.
In 1968, Cavalier fitted a Mustang with a Rolls-Royce Dart 510 turboprop with 1,245 ekW (1,670 eHP), calling the modified machine the "Cavalier Turbo Mustang III". Cavalier tried to sell the concept to the Air Force, but the service wasn't interested. Cavalier then sold the Turbo Mustang III to Piper Aircraft and transferred the technology base for the work along with it. The Turbo Mustang III was delivered to Piper in November 1970.
The USAF was interested in a more formidable COIN aircraft for supply to US allies under MAP, and had initiated a program named "Pave Coin" to evaluate such a machine. Piper felt that a turboprop Mustang would fit the requirement, and converted an F-51D and a TF-51D to a configuration with a Lycoming T55-L-9 turboprop engine, with 1,830 kW (2,455 SHP). Piper gave the up-engined machines the name of "Enforcer", and the first flew on 19 April 1971. The USAF evaluated one of them, but had cooled to the program and the evaluation led nowhere. However, Congress was very interested in a relatively low-cost close-support aircraft, and pressured the Air Force to award a contract for two "PA-48 Enforcer" prototypes in September 1981. The two PA-48s were also powered by the Lycoming T55-L-9 turboprop, but they were not only completely new-build machines, they were almost entirely new designs.
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PA-48 Enforcer (Piper)
The PA-48s were clearly members of the Mustang family, but they were also clearly bigger and meaner looking. They were 38 centimeters (15 inches) longer, with a bigger tail and a four-bladed paddle propeller; were fitted with plastic armor and self-sealing tanks; and their wings bristled with a total of ten stores pylons. There was also provision for wingtip fuel tanks. They did not have any built-in armament, the plan being that they would carry underwing gun pods instead, and had an ejection seat.
PIPER PA-48 ENFORCER: _____________________ _________________ __________________ spec metric english _____________________ _________________ __________________ wingspan 12.6 meters 41 feet 4 inches length 10.4 meters 34 feet 2 inches height 4 meters 13 feet 1 inch loaded weight 6,350 kilograms 14,000 pounds max speed at altitude 650 KPH 405 MPH / 350 KT service ceiling 11,465 meters 37,600 feet range 1,480 KM 920 MI / 800 NMI _____________________ _________________ _________________The first PA-48 Enforcer flew on 9 April 1983, followed by the second on 8 July, but the Air Force had no enthusiasm for the type. They were flight tested into August 1984 and disposed of in 1986. One of the two prototypes is at the USAF Museum at Wright Patterson Air Force Base in Ohio, and the other at last notice was at Edwards Air Force Base in California, awaiting restoration.
Civilian "Mustangs" / Variants
At the end of WW II, the USAAF had far more Mustangs on their hands than they knew what to do with, and sold some of them off at unbelievable prices of a few thousand dollars. The Mustang was hardly a useful aircraft for any ordinary civilian purpose, but they were an extremely impressive toys, and were hot contenders for the air race competitions that were revived in the postwar years.
The National Air Races were resurrected in Cleveland, Ohio, in 1946, and were to continue through 1949. These races featured colorfully-painted surplus warbirds, including the P-51 Mustang, P-38 Lightning, P-39 Airacobra, P-63 Kingcobra, and the F-4U Corsair. These and other "unlimited" air races were terminated when a modified P-51C flew into a house, killing the pilot and a mother and child. There would be no unlimited air races again until 1964, and even midget air racing was terminated after an air accident at a race in 1960. Unlimited air racing was revived at Reno in 1964, and continues to this day, with Mustangs as prominent contenders against other piston-engine "brutes" such as Grumman Bearcats and Hawker Sea Furies.
The racers were stripped of armor and other combat gear, and sometimes highly modified as well, with custom features such as tiny canopies. One Mustang was even extensively rebuilt to accommodate a Griffon engine and contra-rotating propellers. The racers had colorful names such as "Miss Foxy Lady", "Specter", "Stiletto", "Galloping Ghost", and the particularly well-known "Red Baron".
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P-51D WARBIRD
While many WW II warplanes are very rare today, since most of them were simply scrapped after the war, the long use of surplus P-51Ds ensured that many survived and eventually found their way into the warbird market. Over 200 P-51Ds are currently flying, and new-build spare parts for P-51Ds are available.
A number of reduced-scale Mustang replicas, powered by air-rated V8 engines and the like, are available to private fliers, generally in kit form, and the general Mustang configuration is often used as a basis for single-seat sport and race aircraft. Such "mini-Mustangs" may not have the status of the real thing, but to those with limited budgets, a small part of a legend is still something to be greatly prized.
The following table lists Mustang variants
and production:
______________________________________________________________________ Allison Mustangs: NA-73X 1 Initial prototype. Mustang I 620 NA-73/83 -- initial production, for RAF service. XP-51 2 Two NA-73s for USAAF evaluation. Mustang IA 93 NA-91 -- Lend-Lease cannon-armed variant for RAF. P-51 57 NA-91s retained by USAAF. F-6A - 55 NA-91s modified for photo-reconnaissance. A-36A 500 NA-97 -- dive-bomber for USAAF (1 to RAF). P-51A 310 NA-99 -- first USAAF fighter variant. F-6B - 35 NA-99s modified for photo-reconnaissance. Mustang II - 50 NA-99s passed on to RAF. ______________________________________________________________________ 1,583 Subtotal Allison Mustangs. ______________________________________________________________________ Merlin Mustangs: Mustang X - 5 Merlin conversions of Allison Mustangs by Rolls. XP-51B - AKA XP-78, 2 Merlin conversions of NA-91s by NAA. P-51B(C) 3,738 NA-101 -- initial Merlin production variant. F-6C - 91 NA-101 reconnaissance conversions for USAAF. Mustang III - 910 NA-101s RAF. P-51D(K) 9,456 NA-106 -- P-51B with bubble canopy, etc. Mustang IV(A) - 875 NA-106s for RAF. F-6D(K) - Reconnaissance version of P-51D(K). TF-51D - 15 two-seat trainer conversions. ETF-51D - P-51 conversion for carrier trials. XP-51F 2 NA-105 -- lightweight P-51. Mustang V 1 NA-105 for RAF. XP-51G 2 NA-105s with 5-bladed Rotol propeller. XP-51J 2 Lightweight with Allison engine. P-51H 555 NA-126 -- final production version. P-51M 1 NA-124 -- Fort Worth version of NA-126. ______________________________________________________________________ 13,757 Subtotal NAA Merlin Mustangs. 15,340 Subtotal NAA Mustang production. ______________________________________________________________________ Commonwealth CA-18 Mustangs: Mustang 21 40 P-51D equivalent. Mustang 22 14 With reconnaissance camera. Mustang 23 66 With Rolls (not Packard) Merlins. ______________________________________________________________________ 120 Subtotal Commonwealth production. 15,460 Subtotal single-engine Mustang production. ______________________________________________________________________ Twin Mustangs: XP-82 2 NA-120 -- Merlin engines. XP-82A 1 NA-120 -- Allison engines. P-82B 20 Merlin engines. XP-82C - P-82B night fighter conversion, SCR-720C radar. XP-82D - P-82B night fighter conversion, AN/APS-4 radar. F-82E 100 Allison-engine day fighter. F-82F 100 F-82E night fighter with AN/APG-28 radar. F-82G 50 F-82E night fighter with SCR-720C radar. F-82H - 9 F-82Fs + 5 P-82Gs wwith cold weather gear. ______________________________________________________________________ 273 Subtotal Twin Mustang production. 15,733 TOTAL MUSTANG PRODUCTION ______________________________________________________________________
Sources for this document include:
P-51 MUSTANG, by Roy Cross, Gerald Scarborough, & Bruce Robertson, Patrick Stevens London, 1973.
P-51 MUSTANG, by Robert Grinsell, a section of the compilation THE GREAT BOOK OF WORLD WAR II AIRPLANES, Bonanza Books, 1984.
FIGHTERS OF WORLD WAR II, by Charles W. Cain & Mike Jerram, Exeter Books, 1979.
F-82 TWIN MUSTANG, by Larry Davis, SQUADRON/SIGNAL MINI IN ACTION SERIES (number 8), 1996.
GREAT AIRCRAFT OF WWII, by Alfred Price & Mike Spick, Chartwell Books, 1997.
"North American P-51 Mustang", by Bill Gunston & Robert F. Dorr, WINGS OF FAME, Volume 1 (1995), 56:115. This document owes much to this article.
"Commonwealth CA-15: The 'Kangaroo' Fighter" by David Donald, WINGS OF FAME, Volume 4 (1996), 118:121.
Some of the comments on the Cavalier Mustangs and the Piper Enforcer program were derived from an online article by aviation enthusiast Joe Baugher.
Courtesy of vectorsite
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