When climbing with constant calibrated airspeed, how are Mach number and true airspeed affected?

When an aircraft climbs at a constant calibrated airspeed, both the Mach number and true airspeed typically increase due to the changes in atmospheric conditions with altitude.

As the aircraft ascends, the density of the air decreases, causing the true airspeed (TAS) to rise to maintain a constant calibrated airspeed (CAS). CAS is based on the dynamic pressure of the air, which is influenced by air density. As the altitude increases, the same calibrated airspeed translates into a higher true airspeed because the air is less dense.

Furthermore, the Mach number, which is the ratio of the true airspeed to the speed of sound, also increases because the speed of sound decreases with altitude due to lower temperatures. Consequently, even if true airspeed is rising, it is doing so at a rate that can improve the Mach number significantly during a climb.

Therefore, when climbing with a constant calibrated airspeed, both the Mach number and true airspeed are affected positively, leading them to increase as the aircraft climbs.