What is the purpose of the airspeed indicator in an aircraft?

The purpose of the airspeed indicator in an aircraft is to indicate the aircraft's speed. This instrument measures the difference between the dynamic pressure of the air flowing around the aircraft and the atmospheric pressure, providing the pilot with crucial information about how fast the aircraft is moving through the air.

Understanding airspeed is vital for a variety of reasons: it helps ensure safe flying speeds, aids in stall prevention, and is essential for performance calculations during takeoff and landing. Optionally, airspeed is also important for determining the correct handling of the aircraft and maintaining control during different phases of flight.

The other options address functions unrelated to speed. Altitude changes are measured by the altimeter, heading changes are indicated by the heading indicator or compass, and vertical speed is monitored using the vertical speed indicator. Each of these instruments serves a specific purpose that is distinct from that of the airspeed indicator.