What is calibrated airspeed corrected for compressibility?

Equivalent airspeed is defined as calibrated airspeed that has been corrected for compressibility effects. As aircraft speeds increase, especially near and above the speed of sound, airflow characteristics change due to compressibility, impacting the accuracy of indicated flight parameters.

Equivalent airspeed accounts for these compressibility corrections, allowing pilots to better understand the aerodynamics encountered at higher speeds. In essence, it standardizes the calibration of airspeed to conditions that facilitate consistent performance predictions, especially critical for high-speed flight.

The other choices each represent different concepts related to airspeed. Calibrated airspeed refers to the airspeed indicated on the aircraft's instruments, corrected for instrument and positioning errors but does not account for compressibility. True airspeed is the actual speed of the aircraft through the air, considering altitude and temperature but also does not address compressibility directly. Indicated airspeed is simply what the aircraft's speed measuring system shows, without any corrections applied. Thus, equivalent airspeed specifically incorporates the necessary adjustments for compressibility, making it the correct answer in this context.