What is calibrated airspeed (CAS)?

Calibrated airspeed (CAS) is defined as indicated airspeed that has been adjusted to correct for any errors in the instrument readings. These errors can arise from a variety of factors, including instrument inaccuracies, position errors (caused by airflow around the aircraft), and installation errors. CAS is important because it provides a more accurate representation of the aircraft’s performance and handling characteristics than indicated airspeed alone. To determine CAS, the pilot refers to a correction chart provided in the aircraft's flight manual, which lists how much to adjust the indicated airspeed based on the aircraft's configuration and operating conditions.

This understanding of CAS is crucial for safe flight operations and effective navigation, especially at lower altitudes where the effects of these errors are more pronounced. It's particularly useful in the context of performance calculations, such as determining stall speeds or safe speeds for maneuvering.

The other definitions mentioned do not accurately describe calibrated airspeed. True airspeed relates to the actual speed of the aircraft through the air, corrected for altitude and temperature, while ground speed is the speed of the aircraft in relation to the ground, adjusted for wind effects. Equivalent airspeed pertains to compressibility effects at higher speeds, which is different and specific to supersonic conditions. Hence, understanding