Position error is caused by

• A. Altimeter setting not corrected
• B. Misalignment of the Pitot tube with the relative wind and position of the static vents
• C. Frictioning and binding of the instrument
• D. Cabin pressure fluctuations

Answer: (B)

Position error in the pitot-static system comes from how the pressure ports are placed and oriented in the airflow. The Pitot tube is meant to sample stagnation (dynamic) pressure from air moving straight into the tube, so it must face the relative wind. If it is misaligned with the flow, or if the static pressure ports are located where the air around the aircraft is disturbed by the fuselage, wings, or other surfaces, the pressures sensed won’t match the true ambient and dynamic pressures. This combination—the tube’s angle to the wind and the position of the static vents in disturbed airflow—causes position error, which leads to incorrect airspeed, altitude, and vertical speed readings.

The other issues describe different kinds of errors: not correcting the altimeter setting affects altitude readings overall, not the measurement geometry; friction or binding is a mechanical fault inside the instrument; cabin pressure fluctuations pertain to pressurization effects, not the port placement or orientation.