FAA Powerplant Written Practice Test

What is the general threshold for ground boosted engine manifold pressure?

1. 15" Hg

2. 30" Hg

3. 40" Hg

4. 25" Hg

The correct answer is: 30" Hg

The general threshold for ground boosted engine manifold pressure refers to the maximum pressure levels that are typically acceptable for an aircraft engine operating at ground level. In many piston engines that are turbocharged or supercharged, a manifold pressure of around 30 inches of mercury (inHg) indicates the engine is operating at boost levels that are used to gain extra power while on the ground. This pressure level is significant as it represents a critical balance between providing the necessary power for takeoff and ensuring that the engine operates within safe limits. Manifold pressure above this threshold can lead to excessive stress on the engine components, potentially resulting in damage if sustained. Understanding this target for manifold pressure is essential for pilots and maintenance personnel alike, as it helps them monitor engine performance and make informed decisions during operations. The figure of 30 inHg is commonly recognized across different aircraft and provides a benchmark for performance expectations at ground level.