What is "indicated airspeed" (IAS)?

Indicated airspeed (IAS) is defined as the speed read directly from the airspeed indicator in an aircraft, without any adjustments for variations in air density, temperature, or instrument errors. This measurement is critical for pilots because it reflects the dynamic pressure that the aircraft experiences as it moves through the air. IAS is essential for understanding the aircraft’s performance characteristics and determining appropriate operational limits, such as stall speed and climb rates.

Understanding IAS helps pilots to maintain safe operating speeds, especially during takeoff and landing. It is important to differentiate IAS from other speed measurements, such as true airspeed or ground speed, which involve various corrections and adjustments. This differentiation emphasizes how IAS serves as the primary reference for many operational considerations during flight.