What does IAS stand for in airspeed terminology?

• A. Indicated Altitude Scale
• B. Indicated Airspeed
• C. International Air Service
• D. Integrated Airspeed

Answer: (C)

In airspeed terminology, the main idea is what the aircraft’s speed indicator is actually showing. IAS stands for Indicated Airspeed—the speed read directly from the airspeed indicator. This reading comes from the dynamic pressure detected by the pitot-static system and is not corrected for instrument or position errors. That’s why pilots use IAS for maneuvering and stall considerations, because speeds like stall and maneuvering speeds are specified in terms of IAS.

To place IAS in context with other terms: calibrated airspeed (CAS) is IAS after correcting for instrument and position errors; true airspeed (TAS) is CAS corrected for air density and temperature, representing actual speed through the air; equivalent airspeed (EAS) is CAS corrected for compressibility effects at higher speeds. The other phrases you saw aren’t standard airspeed terms.