True Airspeed” (TAS) refers to the actual speed of an aircraft through the surrounding air. It is the speed of the aircraft relative to the undisturbed air in which it is flying, and it is measured in knots (nautical miles per hour) or meters per second (m/s).
V = Ve / √(σ)
- V: True Airspeed (TAS). It is the actual speed of the aircraft through the surrounding air, measured relative to the undisturbed air in which it is flying. True Airspeed is usually expressed in knots (nautical miles per hour) or meters per second (m/s).
- Ve: Equivalent Airspeed (EAS). Equivalent Airspeed is the airspeed that would produce the same dynamic pressure (q) as the true airspeed at sea level in the International Standard Atmosphere (ISA). It is a calibrated airspeed corrected for the non-standard atmospheric conditions at the aircraft’s current altitude.
- σ: Air density ratio. It is the ratio of the actual air density (ρ) to the air density at sea level in the International Standard Atmosphere (ρ0). It is defined as σ = ρ / ρ0.