Originally posted by -duma-
'The speeds given in the Typhoon's table (of 'limiting indicated airspeeds against height bands') were, after allowing for position error, equivalent to a Mach number of 0.79, which was higher than for any contemporary piston-engined fighter.
The aircraft to be used for the compressibility dive tests was.
The indicated Mach number (IMN) ...
The problem whether the instruments showed true mach number will allways remain. I seriously doubt that the instruments showed correct mach numbers in ww2. It doesnīt surprise me anymore that according to instruments(!) most RAF fighter seem to be superior at high mach numbers, though they were definitly not the best aerodynamic designs. Itīs just a question of instrument accuracy.
But for flight safety accuracy wasnīt necessary, when the pilot reads an instrument the true airspeed isnīt of interest, only what the needle shows and what test pilots found out as a limit with the same instruments.
It would be really interesting to take those old instrument out of a museum and run tests in modern wind tunnels to check their correctness.
niklas