True airspeed is defined as?

• A. Actual airspeed, determined by applying a correction for pressure altitude and temperature to the CAS
• B. Indicated airspeed
• C. Calibrated airspeed
• D. Ground speed

Answer: (A)

True airspeed is the speed of the airplane relative to the surrounding air. To get TAS from cockpit readings, you start with calibrated airspeed (which already removes instrument and position errors) and apply a density correction for altitude and temperature. This correction accounts for how air density changes with pressure altitude and temperature, since the same dynamic pressure reading corresponds to a different actual speed through the air depending on how thick or thin the air is. In other words, TAS reflects how fast you’re moving through the air mass, not how far you travel over the ground.

Indicated airspeed is just the raw reading from the airspeed indicator. Calibrated airspeed corrects that reading for instrument and position errors but still doesn’t account for air density. Ground speed is TAS adjusted for wind, which is a different concept.