Private Pilot Private Exam

The operating principle of float-type carburetors is based on the difference in...

1. Altitude and pressure

2. Air pressure at the venturi throat and the air inlet

3. Fuel density and temperature

4. Oxygen levels and humidity

The correct answer is: Air pressure at the venturi throat and the air inlet

The operating principle of float-type carburetors relies on the differences in air pressure, specifically at the venturi throat and the air inlet. In a float-type carburetor, as air flows through the venturi, the design creates a reduction in pressure at the throat due to the acceleration of the air through the narrower section. This low-pressure area draws fuel from the float chamber into the airstream. The fundamental operation is that as the engine demands more power, more air flows, resulting in a decrease in pressure at the venturi throat, which pulls in more fuel to maintain the correct air-fuel ratio for combustion. This interaction between inlet air pressure and the venturi effect allows the carburetor to adjust the fuel flow based on the engine’s requirements effectively, ensuring optimal performance. While altitude and pressure can impact engine performance in general, they do not specifically describe the operating principle of float-type carburetors. Similarly, factors like fuel density and temperature, or oxygen levels and humidity, play roles in engine operation and combustion efficiency but are not directly related to the carburetor's operation mechanism. The critical aspect of how a float-type carburetor functions is centered around the airflow dynamics and pressure differentials as fuel is metered into