How do you calculate true airspeed (TAS) from indicated airspeed (IAS)?

To calculate true airspeed (TAS) from indicated airspeed (IAS), it is essential to understand the relationship between these two speeds and the corrections that need to be applied based on altitude and temperature.

Indicated airspeed (IAS) is the speed shown on the aircraft’s airspeed indicator and is not adjusted for factors such as altitude and temperature. At higher altitudes, the air density decreases, which affects the performance and readings of airspeed indicators. Additionally, temperature variations from the standard atmosphere can further influence air density and the aircraft's true speed.

To convert IAS to TAS, you need to add both the temperature correction and the altitude correction. The temperature correction accounts for variations in air temperature, while the altitude correction compensates for changes in air pressure at different altitudes, both of which are necessary to derive an accurate measure of TAS.

Therefore, the correct calculation for true airspeed is to take the indicated airspeed and add the combined corrections for altitude and temperature. This process yields the true airspeed, which reflects how fast the aircraft is moving through the actual air mass, which is crucial for flight planning and performance calculations.