Mach Number - Calculation

Calculation

The Mach number at which an aircraft is flying at can be calculated by

${M}=\frac{V}{a}\,$

where:

is Mach number

is velocity of the moving aircraft and

is the speed of sound at the given altitude

Note that the dynamic pressure can be found as:

Assuming air to be an ideal gas, the formula to compute Mach number in a subsonic compressible flow is derived from Bernoulli's equation for M<1:

${M}=\sqrt{\frac{2}{\gamma-1}\left}\,$

where:

is impact pressure (stagnation pressure) and

is static pressure

is the ratio of specific heat of a gas at a constant pressure to heat at a constant volume (1.4 for air).

The formula to compute Mach number in a supersonic compressible flow is derived from the Rayleigh Supersonic Pitot equation:

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