Design and development

2008-02-07T05:38:00.000-08:00

The result of the MAP order was the NA-73X project (from March 1940). The design followed the best conventional practice of the era, but included two new features. One was a new NACA-designed laminar flow wing, which was associated with very low drag at high speeds. Another was the use of a new radiator design (one Curtiss had been unable to make work) that used the heated air exiting the radiator as a form of jet thrust in what is referred to as the "Meredith Effect". Because North American lacked a suitable wind tunnel, it used the GALCIT 10-foot wind tunnel at Cal Tech. This led to some controversy over whether the Mustang's cooling system aerodynamics were developed by North American's engineer Edgar Schmued or by Curtiss, although historians and researchers dismiss the allegation of stolen technology; such claims are likely moot in any event, as North American had purchased Curtiss’ complete set of P-40 and XP-46 wind tunnel data and flight test reports for US$56,000.

While the United States Army Air Corps could block any sales it considered detrimental or not in the interest of the United States, the NA-73 represented a special case. In order to ensure deliveries were uninterrupted, an arrangement was eventually reached where the RAF would get its aircraft in exchange for NAA providing two free examples to the USAAC for evaluation.

The prototype NA-73X was rolled out just 117 days after the order was placed, and first flew on 26 October 1940, just 178 days after the order had been placed — an incredibly short gestation period. In general, the prototype handled well and the internal arrangement allowed for an impressive fuel load. It was armed with four .30 caliber Browning (7.62 mm) and two .50 M2 Browning (12.7 mm) machineguns in the wings and two .50 M2s in the chin.

North American P-51 Mustang

2008-01-07T08:09:00.000-08:00

History: One of the most effective, famous and beautiful fighter aircraft of WWII, the P-51 was designed to fulfill a British requirement dated April 1940. Because of the rapidly-mounting clouds of war in Europe, the UK asked North American Aircraft to design and build a new fighter in only 120 days. The NA-73X prototype was produced in record time, but did not fly until 26 October 1940. The first RAF production models, designated Mustang Mk Is, underwent rigorous testing and evaluation, and it was found that the 1,100-hp Allison engine was well suited for low-altitude tactical reconnaissance, but the engine's power decreased dramatically above an altitude of 12,000 feet, making it a poor choice for air-to-air combat or interception roles. Because of this, the RAF left its eight machine guns intact, but also fitted the Mustang with cameras. In this configuration, it served in at least 23 RAF squadrons, beginning in April 1942.

At the same time, the US Army Air Corps ordered a small number for tactical reconnaissance evaluation as the F-6A. After the RAF found the aircraft's performance lacking, they tested a new engine, the 12-cylinder Rolls-Royce Merlin. This gave much-improved performance, and led to the USAAF fitting two airframes with 1,430-hp Packard-built Merlin V-1650 engines. These aircraft were re-designated XP-51B. Practically overnight, the aircraft's potential began to grow.

Since the RAF had had good success with the Mustang in a ground attack role, the USAAF bought 500 aircraft fitted with dive brakes and underwing weapons pylons. These were initially designated the A-36A Apache, but later retained the name Mustang. Almost simultaneously, they ordered 310 P-51As with Allison engines. Some of these were delivered to the UK as Mustang Mk IIs, and some became F-6B reconnaissance aircraft for the USAAF.

The first Merlin-engine versions appeared in 1943 with the P-51B, of which 1,988 were built in Inglewood, California, and the P-51C, of which 1,750 were built in Dallas, Texas. Both new versions had strengthened fuselages and four wing-mounted 12.7-mm machine guns. Many of these new Mustangs were delivered to the UK as Mustang Mk IIIs, and others went to the USAAF as F-6Cs. The Merlin-powered Mustangs were exactly what the Allied bombers in Europe desperately needed, and they became famous for their long range and potent high-altitude escort capability. The most significant variant, the P-51D, featured a 360-degree-view bubble canopy, a modified rear fuselage, and six 12.77-mm machine guns. 7,956 were built, and once again, many went to the UK as Mustang Mk IVs and others became USAAF F-6D reconnaissance aircraft. Next came the P-51K, which was generally similar. A third of these became RAF Mustang IVs also, and over a hundred became F-6Ks. Very late in the war, the P-51H appeared, although only 555 of 2000 were completed before V-J Day caused the cancellation of the order. US production totaled 15,386, but at least 200 more were built by the Commonwealth Aircraft Corporation of Australia with imported parts and designated Mustang Mk 20/21/22/23. None of these saw service before the end of the war. Under the Lend-Lease program, 50 P-51s were supplied to China, and 40 more were supplied to the Netherlands in the Pacific theater.

After the war, the P-51 remained in US service with the Strategic Air Command until 1949, and with the Air National Guard and Reserves into the 1950s. It became one of the first fighters to see combat in the Korean War. The RAF's Fighter Command used them until 1946. In addition, over 50 air forces around the world acquired and used the Mustang for many more years, some as recently as the early 1980s. When the US Air Force realigned their aircraft designations in the 1950s, the Mustang became the F-51.

In the last 40 years, surplus Mustangs have been modified and used extensively as civilian air racers, but the latest trend is for private owners to restore them to almost perfect, historically-accurate condition. As public appreciation for the Mustang has grown, the monetary value of the few remaining examples has skyrocketed. War-surplus P-51s, once auctioned from storage for less than (US) $2000, are now usually valued at three-quarters of a million dollars or more. The restoration of existing airframes has become a small industry in the US, UK and Australia, and the total number of flyable examples, despite one or two accidents each year, is growing. Several Mustangs have been or are currently being restored as two-seat, dual-control TF-51s, a trend which promises to ensure that today's operators are better-trained than any previous generation of Mustang pilots.

Nicknames: Fifty One; 'Stang; Peter-Dash-Flash

Specifications (P-51D):
Engine: One 1,695-hp Packard Merlin V-1650-7 piston V-12 engine
Weight: Empty 7,125 lbs., Max Takeoff 12,100 lbs.
Wing Span: 37ft. 0.5in.
Length: 32ft. 9.5in.
Height: 13ft. 8in.
Performance:
Maximum Speed: 437 mph
Ceiling: 41,900 ft.
Range: 1300 miles
Armament: Six 12.7-mm (0.5 inch) wing-mounted machine guns, plus up to two 1,000-lb bombs or six 127-mm (5 inch) rockets.

Number Built: Approximately 15,018 (including ~200 built in Australia)

Number Still Airworthy: Approximately 150