Calibrated Airspeed

Calibrated Airspeed (CAS) is the indicated airspeed corrected for instrument errors inherent in the airspeed indicator and position errors caused by the location of the pitot tube and static ports on the aircraft. CAS is the second step in the hierarchy of airspeed corrections: IAS → CAS → EAS → TAS.

Position error varies with angle of attack, flap configuration, and sideslip angle. Aircraft manufacturers publish correction tables or cards that allow pilots to convert IAS to CAS. In many modern aircraft with air data computers, these corrections are applied automatically.

CAS is particularly important because V-speeds and performance data in the Aircraft Flight Manual are expressed in CAS (or KCAS — knots calibrated airspeed). When a pilot reads a V1 of 148 knots from the performance tables, that value is in CAS, and the pilot must account for any known instrument error.