The Development of the P-51D/K

While the P-51C received minor improvements, the real overhaul was saved for the P-51D, the variant of the Mustang which was soon to become the most loved fighter of the war, perhaps of all time. The majority of the variants were "D" models were built at Inglewood, while a much smaller number of "K" models were built at Dallas, fitted for no apparent reason with a cuffless propeller that caused a noticable decline in the "K" model's performance.

The Merlin was retained in the "D" model because of its outstanding performance and reliability. As evidence of the reliability of the Merlin, when the Japanese Air Force captured a Mustang, they ran the Merlin and were astonished to see that it did not leak oil, which all of their fighters did in great profusion.

The first improvement was to redesign the cockpit and rear half of the fuselage. Instead of the ubiquitous birdcage cockpit, North American installed a bubble canopy. The Mustang pilot now had an unimpeded 360º view, improving his rearward and downward visibility greatly, which in turn, improved the Mustang’s ability to dogfight. The bubble canopy had slightly higher drag than the previous models, but since the Mustang was appreciably faster than its German-built stablemates, it was a sensible exchange of speed for better visibility.

The Mustang then received a redesign of its guns. The Mustang’s machine guns had a tendency to jam, especially in a tight turn. The P-51Ds new guns were more reliable and more powerful. The Mustang also received slightly better armor to its radiator, which was one of the P-51’s few vulnerable spots.

The "D" model Mustang began arriving with units in the summer of 1944. The Mustang "D" was so superior to its Axis adversaries that it equipped all but one of the fighter groups in Europe, which retained Thunderbolts to use in close air support of ground forces. Mustang groups were based in Iwo Jima shortly after Marines captured the island. From there, the long range of the Mustang allowed them to escort the B-29 "Superfortresses" which were bombing mainland Japan from bases in the Marshall Islands. P-51Ds were given to the Chinese Air Force, the Free French, and the British. At war’s end in 1945, it was the Mustang which was providing total air superiority over the entire globe.

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