What is indicated airspeed (IAS)?

Indicated airspeed (IAS) is defined as the speed that is read directly from the airspeed indicator without any corrections applied for errors that may occur in the system. This reading reflects the dynamic pressure exerted on the aircraft by the air as it moves through it, giving pilots an immediate sense of how fast the aircraft is moving in the air.

IAS is crucial for pilots because it is directly related to the aircraft's aerodynamic performance, including stall speed, climb rate, and approach speed, all of which are critical for safe flight operations. It's important to understand that while IAS provides valuable information, it does not account for variations like altitude, air density, or instrument errors that might affect the actual performance.

In contrast to IAS, true airspeed (TAS) is adjusted for these factors and gives an accurate measure of the aircraft's speed through the air, while groundspeed is the speed relative to the earth's surface, influenced by wind. Therefore, the nature of IAS as the uncorrected measurement is essential for maintaining awareness and control of an aircraft's performance during flight.