What does Indicated Airspeed (IAS) include, in addition to calibrated airspeed (CAS)?

Indicated Airspeed (IAS) is a critical measurement in aviation that represents the speed of the aircraft as shown on the airspeed indicator, which takes into account certain factors in its calculation. In addition to calibrated airspeed (CAS), which corrects for the installation and position error, IAS includes instrument errors—these are discrepancies in the readings provided by the airspeed indicator due to factors like instrument malfunctions or inaccuracies in the instrument design.

These instrument errors can arise from various sources, such as pressure sensing issues or calibration inaccuracies that occur over time, and they ensure that the indicated airspeed closely reflects the actual dynamic pressure the aircraft is exposed to. Understanding that IAS includes these errors is essential for pilots, as they need to be aware of discrepancies that could affect flight performance and safety.

The other options do not apply directly to the definition of IAS. Gradient errors relate to changes in altitude affecting pressure but do not factor into IAS directly. Ground effects pertain to alterations in lift and drag when close to the ground, influencing actual performance but not the airspeed indicated on the instrument. Speed tolerance refers to acceptable variations in speed during flight but does not directly relate to the way IAS is defined. Understanding the role of instrument errors is crucial for interpreting airspeed