How do airspeed indicators function in an aircraft?

• A. By calculating fuel flow
• B. By measuring air pressure differences
• C. By monitoring the engine RPM
• D. By assessing wing load factors

Answer: (B)

Airspeed indicators function by measuring air pressure differences, specifically between dynamic pressure (the pressure of the air impacting the aircraft) and static pressure (the ambient air pressure surrounding the aircraft). The device uses a pitot tube, which is typically located on the aircraft’s fuselage or wing, to measure the dynamic pressure. When air flows into the pitot tube, it creates pressure equivalent to the kinetic energy of the moving air.

This dynamic pressure is then compared to the static pressure measured through static ports on the aircraft. The difference between these two pressure readings is translated into an airspeed reading on the indicator, usually displayed in knots or miles per hour. Because this measurement relies on the principles of physics regarding the behavior of air, it provides pilots with crucial information on the aircraft's speed relative to the surrounding air.

Options suggesting fuel flow, engine RPM, or wing load factors do not relate to how airspeed is specifically measured and interpreted. Fuel flow pertains to engine efficiency and operation, engine RPM reflects the engine's performance, and wing load factors relate to aerodynamic principles affecting lift and stability, but none of these directly measure airspeed in flight.