What is the primary function of an airspeed indicator?

The primary function of an airspeed indicator is to display the aircraft's speed relative to the surrounding air. This measurement is crucial for a pilot because flying at the appropriate airspeed ensures that the aircraft operates efficiently, remains stable, and adheres to various aerodynamic principles.

Understanding airspeed is essential for safe flight operations. It helps pilots determine takeoff and landing speeds, assess performance in different flight conditions, and interpret stall speeds, which are critical for maintaining control of the aircraft.

Unlike monitoring fuel levels, altitude changes, or wind conditions, the airspeed indicator focuses specifically on the relationship between the aircraft and the air through which it is traveling. This data is vital for various phases of flight, including climbing, cruising, and descending, thus underscoring why its primary role is as described.