Airspeed

How Is Airspeed Defined?

Airspeed is the speed of an airplane as compared to the speed of the air and is measured using an airspeed indicator. There are four kinds of airspeed: 1. indicated airspeed, which is the airspeed according to the airspeed indicator without accounting for errors, instrument, or position, 2. calibrated airspeed, which is the indicated airspeed, but adjusted for position, instrument, and installation errors, 3. equivalent airspeed, which is the calibrated airspeed, but adjusted for the effects of compressibility, and 4. true airspeed, which is the equivalent airspeed, but adjusted to account for the density of the air, and that is also the actual speed of the aircraft.