Which part of an air strut limits the amount of air extracted from the compressor section?

• A. Expansion joints
• B. Venturi
• C. Valve
• D. Regulator

Answer: (B)

The idea being tested is how a passive flow-restriction device can limit how much air is drawn from a compressor section. A venturi does this through its shape: it narrows to a throat, which speeds up the airflow and lowers the static pressure at that point. With the upstream pressure from the compressor fixed, the amount of air that can be pulled through the constricted section is limited by that throat area and the resulting pressure drop. In an air strut system, this passive restriction acts like a built-in flow limiter, preventing excess air from being extracted.

Expansion joints mainly accommodate movement and don’t regulate flow. A valve can control flow actively, but it’s a controllable element, not a fixed limiter. A regulator sets and maintains a specific pressure, which doesn’t directly cap the volume drawn from the compressor in the same way a venturi does. The venturi provides a simple, passive means to cap the flow, which is why it’s the best answer.