True Airspeed (TAS) - the speed of the airplane in relation to the airmass in which it is flying.

   Indicated Airspeed (IAS) - the speed of the airplane as observed on the airspeed indicator. It is the airspeed without correction for indicator, position (or installation), or compressibility errors.

   Calibrated Airspeed (CAS) - the airspeed indicator reading corrected for position (or installation), and instrument errors. (CAS is equal to TAS at sea level in standard atmosphere.) The color coding for various design speeds marked on airspeed indicators may be IAS or CAS.

   Equivalent Airspeed (EAS) - the airspeed indicator reading corrected for position (or installation), or instrument error, and for adiabatic compressible flow for the particular altitude. (EAS is equal to CAS at sea level in standard atmosphere.)

   Vs0 - the calibrated power off stalling speed or the minimum steady flight speed at which the airplane is controllable in the landing configuration.

   Vs1 - the calibrated power off stalling speed or the minimum steady flight speed at which the airplane is controllable in a specified configuration.

   Vy - the calibrated airspeed at which the airplane will obtain the maximum increase in altitude per unit of time. This best rate of climb speed normally decreases slightly with altitude.

   Vx - the calibrated airspeed at which the airplane will obtain the highest altitude in a given horizontal distance. This best angle of climb speed normally increases slightly with altitude.

   Vle - the maximum calibrated airspeed at which the airplane can be safely flown with the landing gear extended. This is a problem involving stability and controllability.