Definition
A carburetor mounted above the engine's intake manifold so that the fuel-air mixture flows downward through it on its way to the cylinders. Air enters at the top, passes through the venturi where fuel is introduced, and the resulting mixture descends into the engine.
Plain English
A carburetor that sits on top of the engine and lets the air and fuel mixture fall downward into it, helped along by gravity.
Context Anchor
Seen in aircraft engine induction system descriptions, maintenance manuals, and carburetor installation discussions.
Derivation
Downdraft means a downward flow of air. The name simply describes the direction the air-fuel mixture travels through the carburetor — downward — as opposed to an updraft carburetor, where it flows upward.
Why Pilots Care
Reduces the chance of fuel puddling and improves vaporization compared with updraft designs.
Intuition Check
“Downdraft” does not mean a downward-moving air current in the sky here. It means the airflow inside the carburetor moves downward through the unit.
Example Sentence 1
The mechanic removed the air filter from the top of the downdraft carburetor to inspect the throttle plate.
Example Sentence 2
Pilots notice smoother engine operation after a downdraft carburetor is properly tuned.