FAA Powerplant Written Practice Test

What would a high reading on the manifold pressure gauge indicate during engine operation?

1. Increased engine speed.

2. High engine load or throttle position.

3. Improper fuel mixture.

4. Decrease in engine RPM.

The correct answer is: High engine load or throttle position.

A high reading on the manifold pressure gauge is indicative of high engine load or throttle position. This gauge measures the pressure within the intake manifold, which correlates directly to the amount of air-fuel mixture entering the engine. When the throttle is opened wide, it allows more air and fuel into the cylinders, resulting in higher manifold pressure. This is typical during situations where the engine is under load, such as climbing or accelerating, where increased power output is required. An increase in manifold pressure is crucial in assessing engine performance, as it usually indicates that the engine is working harder, which is necessary for producing greater power. The relationship between manifold pressure, engine load, and throttle position is fundamental in understanding how engines respond to different operational conditions. Thus, a high manifold pressure reading effectively signals that the engine is experiencing significant load or a nearly fully open throttle.