What is the primary function of the airspeed indicator?

The primary function of the airspeed indicator is to compare the ram air pressure from the pitot tube with the static air pressure from the static source. This comparison allows the airspeed indicator to provide the pilot with an accurate reading of the airplane's airspeed.

As the aircraft moves through the air, the pitot tube captures dynamic air pressure (ram air), which increases with speed. Simultaneously, the static port measures the ambient static pressure surrounding the aircraft. The difference between these pressures is what the airspeed indicator translates into a speed reading on the dial.

Understanding this function is vital for pilots, as accurate airspeed readings are crucial for various aspects of flight, including safe takeoff and landing speeds and overall aircraft performance. Knowing the correct airspeed helps in maintaining control and ensuring adherence to operational limitations.