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ATPL » Advanced Aerodynamics … » Transonic Speed

48.2 Transonic speed

Transonic speed refers to the range of speeds near and around the speed of sound.

At these speeds, the  airflow around the aircraft can be both subsonic and supersonic, which can cause aerodynamic effects such as shock waves and compressibility effects.

These effects can cause drag, instability, and other issues that must be accounted for in the design and operation of aircraft.


48.2.2 Explain the term ‘speed of sound’.

The speed of sound is how fast sound waves travel through a medium, such as air or water.


48.2.4 Explain the factor determining the local speed of sound (LSS).

The local speed of sound is determined by factors such as:

  • temperature,
  • humidity, and
  • altitude.


48.2.6 Define Mach number and associated computational formulae.

The Mach number is the ratio of the speed of an object moving through a fluid (like air) to the local speed of sound.


48.2.8 Calculate the speed of sound given the appropriate information.


48.2.10 Calculate ‘Mach number’ given the appropriate information.

The formula to calculate Mach number is Mach number = speed of object / speed of sound.


48.2.12 Explain the change of IAS and TAS as a function of altitude at a given Mach number.

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