What is a Venturi tube used for in aircraft instrumentation?

• A. Vertical axis
• B. Vertical card compass
• C. Venturi tube
• D. Very-high frequency

Answer: (C)

A Venturi tube demonstrates how a constricted passage converts velocity into a measurable pressure difference. As air is forced through the narrow throat, its speed increases and the static pressure drops according to Bernoulli’s principle. By sensing the pressure just before the throat and at the throat, you obtain a differential pressure that relates to the air’s flow rate or speed. In aircraft instrumentation, that pressure difference is used to infer airspeed or flow in sensors that rely on this principle. The other options describe unrelated items—orientation, a compass type, and a radio frequency band—so they don’t fit as instruments for measuring airflow.