Equivalent airspeed is the airspeed equivalent to which speed measurement at sea level standard atmosphere?

• A. Indicated airspeed
• B. Calibrated airspeed
• C. True airspeed
• D. Mach number

Answer: (B)

Equivalent airspeed compares the actual dynamic pressure you’re experiencing to the pressure that would be produced at sea-level standard density. In short, it’s the speed at sea-level standard atmosphere that would generate the same dynamic pressure as your aircraft is currently experiencing. To express that same pressure as a speed in standard conditions, the reference used is calibrated airspeed, because CAS is IAS corrected for instrument and installation errors and thus aligns with the actual dynamic pressure under standard conditions. Indicated airspeed is uncorrected, so it doesn’t map precisely to the standard-density dynamic pressure. True airspeed is the actual speed through the air at altitude, not the sea-level standard reference, and Mach is a ratio to the speed of sound. So calibrated airspeed is the best match.