P-51 Mustang

The North American P-51 Mustang was a successful long range fighter aircraft which entered service in the middle years of World War II. The definitive version of the single-seat fighter was powered by a single two-stage supercharged V-12 Merlin engine and armed with six .50 caliber (12.7 mm) M2 machine guns.

P-51H

The original NA-73 had been built to the USAAF acceleration standard of 7.33 g (72 m/s²), which made it stronger but considerably heavier than if it had been designed for the British standard of 5.33 g (52 m/s²). Both the USAAF and the RAF were interested in lightening the plane to be more in line with the Spitfire, which was expected to boost its performance significantly.

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This would result in what was basically an entirely new plane, and it gained a new name, the NA-105. Several prototypes were built with different engines from the P-51F (same engine as the D), G (Merlin 145M) and J (Allison V-1710-119) models. However none of these would go into production.

Related Topics:
Merlin - Allison V-1710

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Instead the final production version would be the P-51H, using the new V-1650-9 engine, a version of the Merlin that included automatic supercharger controls and water injection for bursts of up to 2,000 hp (1,500 kW). With the new airframe several hundred pounds lighter, the extra power, and a better streamlined radiator, the P-51H was among the fastest propeller fighters ever: able to reach 487 mph (784 km/h) at 25,000 ft (7,600 m).

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It was planned that the H model would become the standard fighter for the USAAF for the invasion of Japan, replacing all other models. Production was just ramping up with 555 delivered when the war ended. Additional orders already on the books were cancelled.

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