Definition
Calibrated Airspeed (CAS) is indicated airspeed corrected for instrument error and position error (also called installation error). It represents the airspeed the pitot-static system would read if the sensing equipment and its mounting position introduced no errors. CAS equals true airspeed in standard atmosphere at sea level.
Plain English
It is the airspeed shown on the cockpit gauge after fixing small errors caused by the gauge itself and where the sensors are mounted on the aircraft. It is a more accurate version of what the airspeed indicator shows.
Context Anchor
Seen in aircraft operating handbooks, performance charts, stall speed information, and airspeed correction tables.
Derivation
Calibrated' comes from Latin roots meaning 'to measure precisely against a known standard.' In aviation, it signals that the raw indicated reading has been adjusted to match what the airspeed truly is at the sensor — the indicator has been brought in line with a known correct value.
Why Pilots Care
Accurate performance numbers for takeoff, climb, and landing distances are based on calibrated airspeed, not the raw instrument reading.
Intuition Check
Do not assume CAS is always the same number shown on the airspeed indicator. CAS is the indicated airspeed after applying the aircraft’s correction for known errors.
Example Sentence 1
The POH lists the flaps-up stall speed as 48 knots CAS, so the pilot checked the airspeed correction table to find the matching indicated airspeed.
Example Sentence 2
At cruise altitude the pilot compared the calibrated airspeed to the value needed for best fuel efficiency.