Which airspeed is corrected for compression in the pitot tube?

• A. Indicated airspeed
• B. Calibrated airspeed
• C. True airspeed
• D. Equivalent airspeed

Answer: (D)

When you read the airspeed from the pitot tube, the impact pressure you’re measuring is influenced by air compression, especially at higher speeds. To compare speeds in a way that accounts for this compressibility, we express the result as Equivalent Airspeed. EAS is the speed in standard sea‑level air that would produce the same dynamic pressure if the flow were incompressible. In other words, it adjusts the pitot measurement for compressibility so you’re looking at a consistent, incompressible‑flow reference.

Indicated airspeed is the raw indication from the instrument, without corrections for position/installation or compressibility. Calibrated airspeed corrects IAS for position and installation errors but does not specifically account for compressibility effects. True airspeed represents the actual speed through the air mass, corrected for altitude and temperature effects, not the compressibility correction of the pitot reading. So the correction for pitot‑tube compressibility is reflected in Equivalent Airspeed.