What is the difference between indicated airspeed and true airspeed?

• A. Indicated airspeed is the reading from the airspeed indicator based on dynamic pressure; true airspeed is indicated airspeed corrected for altitude and temperature.
• B. Indicated airspeed and true airspeed are the same at sea level with standard temperature.
• C. True airspeed is the reading from the pitot tube, while indicated is derived from the altimeter.
• D. Indicated airspeed accounts for air density, while true airspeed does not.

Answer: (A)

Indicated airspeed is what the airspeed indicator shows, based on dynamic pressure from the pitot tube. True airspeed is the actual speed through the air, obtained by correcting that indicated speed for altitude and temperature (air density).

As you climb and the air gets thinner, the same dynamic pressure corresponds to a higher actual speed, so TAS is greater than IAS. At sea level in standard atmosphere, they happen to be equal, but the general idea is that TAS accounts for density changes with altitude.

The other statements mix up what measures what: the pitot tube measures dynamic pressure (not TAS directly), the altimeter reads altitude (not TAS), and indicated airspeed is not a density-corrected value.