Originally Posted by
carlwag
At a given altitude and a given mach number, the indicated airspeed will be the same, no matter what the outside air temperature. I remember on the 727, at FL 350, mach .80 equals 272 knots. Always. At different altitudes, the indicated airspeed will be different. At different mach numbers, indicated airspeed will be different. When the temperature changes, and you stay at the same mach number, your true airspeed changes, but not your indicated. Good luck understanding all of that.
Are you sure this is correct? Mach is the ratio of the speed of an object through a medium / speed of sound. The speed of sound is variable with temperature. Thus, at different temperatures, the IAS will be different.
Since I've never paid attention to the IAS speeds for each individual MACH number, I really don't know. Perhaps the temperature is / was almost always the same when you noticed this?