Equivalent airspeed (EAS) refers to the airspeed at sea level in the International Standard Atmosphere (ISA) that would result in the same aerodynamic forces as the true airspeed (TAS) at the current altitude, adjusted for variations in air density. The formula to calculate equivalent airspeed is:
Where:
- is the equivalent airspeed (in m/s),
- is the true airspeed of the aircraft (in m/s),
- is the air density at sea level in the International Standard Atmosphere (ISA) (approx. 1.225 kg/m3)
- is the air density at the current altitude (in kg/m3 ).