Symbols, Abbreviations and Terminology
General Airspeed Terminology and Symbols 一般空速術(shù)語和符號
KCAS Knots Calibrated Airspeed is the indicated airspeed corrected for position and instrument error. Calibrated airspeed is equal to true airspeed in standard atmosphere at sea level.
KIAS Knots Indicated Airspeed is the speed shown on the airspeed indicator. The IAS values published in this handbook assume no instrument error.
KTAS Knots True Airspeed is the airspeed expressed in knots relative to undisturbed air which is KCAS corrected for altitude and temperature.
VG Best Glide Speed is the speed at which the greatest flight distance is attained per unit of altitude lost with power off.
VO Operating Maneuvering Speed is the maximum speed at which application of full control movement will not overstress the airplane.
VFE Maximum Flap Extended Speed is the highest speed permissible with wing flaps in a prescribed extended position.
VNO Maximum Structural Cruising Speed is the speed that should not be exceeded except in smooth air, and then only with caution.
VNE Never Exceed Speed is the speed that may not be exceeded at any time.
VPD Maximum Demonstrated Parachute Deployment Speed is the maximum speed at which parachute deployment has been demonstrated.
VS Stalling Speed is minimum steady flight speed at which the aircraft is controllable.
VS 50% Stalling Speed is minimum steady flight speed at which the aircraft is controllable with 50% flaps.

VSO Stalling Speed is the minimum steady flight speed at which the aircraft is controllable in the landing configuration (100% flaps) at the most unfavorable weight and balance.
VX Best Angle of Climb Speed is the speed at which the airplane will obtain the highest altitude in a given horizontal distance. The best angle-of-climb speed normally increases slightly with altitude.