Description

Although indicated airspeed (IAS) and true airspeed (TAS) are the speeds most commonly used in aviation, references to calibrated airspeed (CAS) and equivalent airspeed (EAS) are quite often encountered.

Remembering the relationship between the various speeds and understanding the conversion from one to another can be facilitated by use of the acronym "ICE T" in which the letters represent Indicated, Calibrated, Equivalent and True. The relationships between the speeds are as follows: