Hi Widewing,
>In point of fact, the P-51D was placarded at 300 mph IAS (539 mph) at 35,000 feet. That's Mach .81 and that ain't slow.
Well, my copy of AAF Manual 51-127-5 gives the redline speed at 35000 ft as 290 mph IAS and 500 mph TAS, which equals Mach 0.75, the value given in the manual as being just below the compressibility threshold. (Contradicting Curtis a second time.)
Of course, the P-51D could go beyond redline speed, but the Me 109 could go to Mach 0.79, too.
(290 mph IAS at 35000 ft convert into 520 mph TAS, but if you account for the compressibility error of the airspeed indicator you'll end up at a lower corrected value actually. Apparently, this wasn't usually taught to WW2 pilots, which gave rise to many exaggerated dive speed stories on both sides.)
Regards,
Henning (HoHun)