I posted this back in June to go along with a TDIAH article about the F-82 Twin Mustang. Now that I have the amazing P-51D to P-51H morph created by @WBizarre, I thought it would be a fun time to repost.
P-51D top, P-51H bottom. The D model was the definitive variant, while the H model was perhaps the best. | Photo: US Air Force
With most military aircraft, there is a significant amount of development and evolution that takes place over the life of a wartime fighter. Those changes can either be entirely internal, and not affect the outward appearance of the aircraft, or they can be external, with modifications to the overall shape of the aircraft, even though the general layout remains the same. And of course, it could also be a combination of the two. The North American P-51 Mustang was one of the best piston-engined fighters to emerge from WWII. And it underwent a host of tweaks and changes that made what many consider the best fighter even better.
North American NA-73X, the prototype P-51 | Photo: US Air Force
Though the Mustang is most closely associated with American forces, it was the British who, facing a shortage of fighters, first approached North American Aviation and asked them to build the Curtiss P-40 Warhawk for the RAF. NAA President James “Dutch” Kindelberger replied by saying that his team could design and build a better fighter in the same amount of time it would take to tool up for the Warhawk. Led by chief designer Edgar Schmued, North American rolled out the prototype P-51 Mustang in just 102 days. Powered by the remarkable Packard Merlin V-12 engine, the Mustang was arguably one of the greatest piston-powered fighters to come out of WWII and, some might say, the best ever.
The tenth production P-51B was modified and served as the prototype for the P-51D. Note the teardrop canopy with armored windscreen, and angled wing root. The production D model would receive the extended vertical stabilizer, or fin fillet. | Photo: US Government
The Mustang underwent many changes as it matured throughout the war. But the most notable structural changes came with the P-51D variant, which eliminated the dangerous blind spot behind the pilot by replacing the original canopy with a plexiglass teardrop canopy. The loss of the dorsal ridge behind the co*ckpit induced yaw instability in a dive, so the vertical stabilizer was extended, though this change was not included in the initial D models. Other outward changes that came with the Mustang D included wing root fillets to accommodate redesigned landing gear which gave the Mustang its characteristic angled leading edge. The P-51D became the definitive variant and served in the highest numbers.
A California Air National Guard P-51H in flight | Photo: US Air Force
Even though the Mustang D proved to be an exceptional fighter with remarkable range and maneuverability, there was still room for improvement. Beginning with the XP-51F and G, North American made the aircraft several hundred pounds lighter while extending the fuselage. The vertical stabilizer was made taller to improve yaw performance, while the ventral air intake was reshaped and lengthened. The result was a slightly taller, more slab-sided fuselage. A new Packard V-1650-9 Merlin with water injection, paired with new automatic supercharger boost control, provided up to 2,270 hp at full tilt, and a new, uncuffed propeller with rounded tips got the most power from the engine (this prop also appeared on later D production models). With less weight and more power, the H was now capable of speeds up to 472 mph, about 30 mph faster than the D.
P-51D, top, compared to P-51H | Photos: Bill Larkins
See how the P-51 morphed into the P-51H, with the thickening of the fuselage, larger slab sides, and taller tail. The H model was also about 12 inches longer. | Morph: @WBizarre
The P-51H, along with the improved Republic P-47N Thunderbolt, were planned as the main fighter force for the anticipated invasion of Japan. And while some H model Mustangs did make it to fighting units, none saw action in WWII. With the end of the war, most of the 555 that were built served stateside in Air National Guard units, while the abundant and battle-tested D model fought in Korea. North American also used the H model, or two of them, with some structural modifications, to create the F-82 Twin Mustang.
The F-82 Twin Mustang was created by joining two P-51H Mustangs | Photo: US Air Force
P-51D Mustangs of the California Air National Guard | Photo: US Air Force
P-51H Mustangs of the Maryland Air National Guard | Photo: US Air Force
Author’s musings: Though performance was improved in the H model, I can’t help but think that the Mustang lost something in the looks department. Of course, looks don’t win dogfights, but there was a balance to the lines and shape of the classic Mustang D. Somehow, at least to me, the H seems a bit more ungainly, though its performance says otherwise. Maybe it’s also the taller tail, or the extended ventral intake. But somehow, the proportions just seem...off. However, if you like the taller tail with the classic fuselage profile, there’s always the Cavalier Mustang.
