rivet gun
IAS corrected for Pressure = Calibrated
Calibrated corrected for Compressibility = Equivalent
EAS corrected for Density = TAS
it is conceivable in your example that the effects of P and C
could cancel one another out on a particular aircraft on a particular day, leaving the IAS constant and the Mach number constant. This would have more to do with the compressibility effect of the aircraft being flown than the atmospheric factors.
The relationship above is universal, not aircraft dependent.
Cheers
