Definition
The internal surfaces of a constricted passage in an aircraft's induction or carburetor system where airflow accelerates and pressure drops. In the context of induction icing, these are the surfaces on which moisture can condense and freeze, restricting or blocking airflow to the engine.
Plain English
The inside walls of a narrow section in the engine's air intake. Air speeds up as it squeezes through this narrow part, which cools the air and can cause ice to form on those walls.
Context Anchor
Seen in discussions of carburetor ice and induction icing, especially where airflow narrows, speeds up, and cools before entering the engine.
Derivation
Named after Giovanni Battista Venturi, an 18th-century Italian physicist who studied how fluids behave when forced through a constricted tube. A 'venturi' is the narrowed section itself; the 'walls' are simply its inner surfaces. Knowing the name comes from the physicist (not a technical Latin root) helps pilots recognise the term wherever a narrowed flow passage appears in aviation.
Why Pilots Care
Ice on these surfaces restricts airflow and changes the fuel-air mixture, causing power loss or engine stoppage.
Analogy
Think of air moving through a pinched section of a hose. The inner sides of that pinched section are like the venturi walls, and anything building up there makes the opening smaller.
Grounding Statement
When air rushes through a narrow throat, it speeds up and cools -- and on those throat walls is exactly where ice likes to form.
Intuition Check
Do not picture building walls. In this context, “walls” means the inside surface of the narrow air passage where ice can stick and grow.
Example Sentence 1
Moisture in the intake air can freeze on the venturi walls, gradually restricting airflow to the engine.
Example Sentence 2
The pilot applied carburetor heat to melt ice that had accumulated on the venturi walls.