Definition
A duct or passage whose internal cross-sectional area decreases in the direction of airflow. As the air moves through this narrowing passage at subsonic speeds, its velocity increases while its static pressure decreases.
Plain English
A pipe or channel that gets narrower as the air flows through it, which makes the air speed up and its pressure drop.
Context Anchor
Seen in aircraft maintenance and systems discussions where air is being shaped or controlled, such as engine air passages, cooling air paths, and cabin airflow ducts.
Derivation
From Latin convergere, meaning 'to incline together' (con- 'together' + vergere 'to bend or turn'). The walls of the duct angle inward toward each other, narrowing the path. Knowing this makes the shape of the duct easier to picture from the name alone.
Why Pilots Care
Affects engine thrust, efficiency, and smooth operation by controlling how air speeds up inside the engine.
Analogy
Think of putting your thumb partly over the end of a garden hose. The water has less room to pass, so it shoots out faster. A converging duct does the same thing to air.
Intuition Check
Converging does not mean two separate ducts are joining together here. It means one duct is getting narrower in the direction the air is moving.
Example Sentence 1
The carburetor uses a converging duct to accelerate intake air, which lowers the pressure and helps draw fuel into the airstream.
Example Sentence 2
In the turbine engine, the converging duct increased air velocity before it reached the compressor.