What does an airspeed indicator measure?

An airspeed indicator measures the speed of the aircraft relative to the surrounding air, which is commonly referred to as indicated airspeed (IAS). This measurement is crucial for pilots because it reflects the aircraft's performance and handling characteristics in the current atmospheric conditions. For instance, the aircraft's lift depends on the airspeed, making it essential for safe operation during different phases of flight, such as takeoff and landing.

In contrast to ground speed, which is the speed of the aircraft relative to the ground and is influenced by wind conditions, indicated airspeed provides a more relevant measure for aerodynamic performance. Altitude, which is often confused with airspeed, is measured by a different instrument called an altimeter, and fuel consumption rate has no relevance to airspeed but is monitored through fuel flow measurement systems. Understanding and utilizing the correct measurements provided by an airspeed indicator is fundamental for effective flight operations.