What is the term for the airspeed equivalent to CAS at sea level in standard atmosphere?

The correct answer is equivalent airspeed (EAS). Equivalent airspeed is defined as the calibrated airspeed (CAS) adjusted for factors such as air density. At sea level in standard atmospheric conditions, the equivalent airspeed is numerically equal to calibrated airspeed for aircraft, as the density of air does not deviate from the standard configuration.

In practical terms, EAS represents the airspeed that an aircraft would require to maintain a certain aerodynamic performance level in a standard atmospheric condition, allowing for performance predictions under normal operating conditions.

This term is crucial for pilots, as it ensures that their performance calculations are based on the effective aerodynamics of the aircraft under standard conditions, thus providing critical information for operations like takeoff and landing.

True airspeed accounts for changes in altitude and temperature and represents the actual speed of the aircraft through the air. Ground speed, on the other hand, is the speed of the aircraft over the ground, influenced by winds. Indicated airspeed refers simply to the speed shown on the aircraft's pitot-static system, without any adjustments for temperature or altitude.