In a typical piston-engine aircraft, which control primarily regulates air flow and air/fuel mixture by changing manifold pressure?

• A. Throttle controls air/fuel flow (manifold pressure), mixture adjusts fuel for the given air, and the propeller control adjusts RPM and thrust.
• B. Mixture controls air/fuel flow, throttle adjusts fuel, propeller control adjusts RPM.
• C. Throttle adjusts fuel for the given air, mixture adjusts RPM, propeller control changes gear.
• D. Fuel selector valve controls power.

Answer: (A)

Power in a typical piston-engine airplane is mainly controlled by the throttle. Opening the throttle allows more air to flow into the engine, increasing the intake manifold pressure and thus the amount of air available for combustion. With more air present, the engine can burn more fuel to produce more power, so the throttle sets the overall air mass entering the cylinders.

The mixture control then adjusts how much fuel is added for that given amount of air, achieving the proper air-fuel ratio. In other words, the throttle determines the air (manifold pressure) and the mixture control fine-tunes the fuel to match that air, maintaining safe and efficient operation.

The propeller control affects the propeller speed and thrust, not the air entering the engine, and the fuel selector valve is about choosing the fuel source, not regulating air flow or the air-fuel mix.