CAS stands for which term?

• A. Indicated airspeed
• B. True airspeed
• C. Calibrated airspeed
• D. Equivalent airspeed

Answer: (C)

Calibrated airspeed is the speed shown by the airspeed indicator after correcting for instrument and installation (position) errors. The indicator reads the pressure it senses, which is affected by how the system is installed and by instrument tolerances. Applying these corrections yields CAS, a more accurate measure of speed through the air than the raw indication.

From there, other speeds are related but serve different purposes. Indicated airspeed is the uncorrected reading. True airspeed accounts for air density changes with altitude and temperature to reflect actual velocity through the air. Equivalent airspeed adjusts for compressibility effects so the speed is expressed as the same dynamic pressure at sea level ISA density would produce.