Definition
Calibrated airspeed (CAS) is the indicated airspeed of an aircraft corrected for instrument error and for position (installation) error of the static pressure source. It is the airspeed the pitot-static system would read if those built-in errors were removed. Calibrated airspeed equals true airspeed in standard atmosphere at sea level.
Plain English
It is the airspeed shown on the cockpit gauge after fixing the small built-in errors caused by the instrument itself and by where the pressure sensor sits on the airframe. Think of it as a cleaned-up version of indicated airspeed.
Context Anchor
Seen in aircraft manuals, performance charts, airspeed calibration tables, and discussions comparing the speed shown in the cockpit with the corrected value.
Derivation
Calibrated comes from the Latin calibrare, meaning to determine the correct measurement of an instrument. So calibrated airspeed is literally the airspeed reading after the instrument has been adjusted to remove its known errors.
Why Pilots Care
Pilots rely on calibrated airspeed for accurate stall speeds, takeoff and landing distances, and climb performance data.
Analogy
It is like a bathroom scale that reads two pounds high. If the scale shows 152 pounds, the corrected value is 150 pounds; calibrated airspeed is the corrected version of the airspeed reading.
Intuition Check
Calibrated does not mean the airplane has been changed or tuned. It means the displayed airspeed has been corrected for known measuring errors.
Example Sentence 1
The handbook lists the flaps-up stall speed as 52 knots calibrated airspeed, so the pilot referred to the correction table to find the matching indicated airspeed for the gauge.
Example Sentence 2
After the pitot-static system check, the airspeed indicator now reads calibrated airspeed correctly.