Which instrument indicates the current speed of an aircraft?

The airspeed indicator is the instrument specifically designed to show the current speed of an aircraft relative to the surrounding air. It measures the dynamic pressure of the air as the aircraft moves through it, providing a direct indication of how fast the aircraft is traveling.

This instrument is crucial for pilots because it helps them maintain appropriate speeds for various phases of flight, such as takeoff, climb, cruise, and landing. Understanding the current airspeed is essential for ensuring safe flight and for maneuvering the aircraft according to its performance limitations.

The altimeter measures altitude above sea level, providing information about vertical position rather than speed. The vertical speed indicator shows the rate of climb or descent, which is also unrelated to the aircraft's forward speed. Lastly, the heading indicator indicates the direction the aircraft is facing, but it does not provide any information regarding the aircraft's speed. Thus, the airspeed indicator is the lone instrument that directly indicates the current speed of an aircraft.