Plain English Meaning

A small fitting in an air line shaped to limit how fast air can flow through it. Once the air reaches the speed of sound at the narrow point, no more air can squeeze through, so the system is protected from runaway airflow if something downstream breaks.

Full Definition

A flow-limiting device installed in a pneumatic line that uses a precisely sized throat to choke airflow at the speed of sound, holding the downstream flow rate constant regardless of further drops in downstream pressure. It protects pneumatic system components by capping the maximum mass flow that can pass through the line, even if a downstream line ruptures.

Context Anchor

Seen in aircraft maintenance descriptions of systems that need air or flow, such as pressure-measuring or pneumatic system lines.