At which airspeed range are installation and instrument errors in airspeed measurements generally greatest?

• A. Low airspeeds
• B. High airspeeds
• C. Medium airspeeds
• D. All ranges equally

Answer: (A)

The airspeed indicator relies on the difference between ram (pitot) pressure and static pressure to show how fast the airplane is moving. When you’re at low airspeeds, the dynamic pressure is small, so any fixed pressure error or misalignment in the pitot-static system has a larger effect on the indicated speed. Small installation issues—like the pitot tube or static ports being mispositioned, leaking, or blocked—or instrument calibration errors produce a bigger percentage error when the true airspeed is low. At higher speeds, the dynamic pressure is larger, so the same absolute error represents a smaller fraction of the signal, making installation and instrument errors less significant. So installation and instrument errors in airspeed measurements are greatest at low airspeeds.