Definition
A type of carburetor that delivers fuel under pressure to a discharge nozzle in the throat of the carburetor, using calibrated air pressure differences across the venturi and impact tubes to meter fuel flow in proportion to airflow into the engine. Unlike a float-type carburetor, fuel is supplied to the metering system under positive pump pressure rather than drawn out by suction, eliminating the float chamber and making the unit largely insensitive to flight attitude, turbulence, and icing of the discharge area.
Plain English
A carburetor that pushes fuel into the engine's airflow under pump pressure instead of letting engine suction pull it out of an open float bowl. Because there is no float bowl sloshing around, it works reliably in climbs, dives, and rough air.
Context Anchor
Seen in aircraft engine fuel-system descriptions, maintenance manuals, and discussions of carburetor types used on reciprocating engines.
Derivation
Pressure refers to fuel being delivered under positive pump pressure rather than by engine suction. Injection here means the fuel is forced into the airstream at a discharge nozzle, distinguishing it from float-type carburetors where fuel is drawn into the venturi by low pressure alone.
Why Pilots Care
Maintains consistent fuel metering during maneuvers, inverted flight, or high-altitude operations where float-type carburetors can fail.
Grounding Statement
In this system, the fuel is actively pushed into the incoming air instead of simply being lifted out of a bowl by airflow.
Intuition Check
Do not confuse a pressure-injection carburetor with direct fuel injection. The fuel is still mixed with the incoming air at the carburetor area, not sprayed directly into each cylinder.
Example Sentence 1
The radial engine on the trainer used a pressure-injection carburetor, so the instructor was not worried about fuel starvation during the spin demonstration.
Example Sentence 2
During aerobatic training the pressure-injection carburetor prevented fuel starvation when the aircraft rolled inverted.