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According to a WWII pilot the P51 (standard) was the first plane to break the "sound barrier", in attack dive. They just didn't know at the time what was happening.
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I've heard this story before, and according to Chuck Yeager it was even around back in the 1950s. However, I have never heard anything to make me believe it's credible. The reasons are several:
1: As an aircraft approaches the speed of sound, turbulence caused by the buildup of air in front of the airplane causes the airplane to shake. A LOT. This was the primary difficulty encountered by teams attempting to break the Sound Barrier; the planes kept disintegrating. Britain lost their best test-pilot when his tailless
Swallow came apart in a dive at around .93 Mach. The P-51 wasn't engineered to deal with these kinds of stresses, and both Chuck Yeager and Bud Anderson state in Yeager's autobiography that numerous P-51s were mysteriously destroyed as they approached .90 Mach, usually while diving after German fighters.
2: The P-51 lacks the horsepower for this. Its' top speed was less than 500mph, and even a full-power zero-lift dive won't add 250+mph to an airplane's top speed. Even going straight down, reaching any speed greater than terminal velocity (220-ish mph max) is all horsepower. The Merlin was a helluvan engine, but it just didn't have the juice. Even the early jets, which had several hundred horsepower per tonne more power than the Mustang, were subsonic.
3: The P-51's wings are -dead- wrong for supersonic flight. In order to deflect and (somewhat) decompress the pressure wave which builds in front of the airplane at high speeds (see #1) you need either swept wings (like almost everything supersonic) or veeeeeeeeeeery thin, short, straight wings (like the X1/2 or F-104 Starfighter). The thin straight wings only work on long, thin aircraft, and not very well at that. The P-51s wings are thick, straight, and basically the worst-possible configuration for supersonic flight. So much bearing surface with so little aft reinforcement would probably cause the transsonic pressure-wave to rip the wings off before you got near 1.0 Mach, which is pretty much what Yeager, Anderson, and other pilots describe happening. This goes triple for the tail surfaces, which are under even more severe stresses thanks to the turbulence coming off the wings.
As for the OP, neat pics!