Which condition exists when a reciprocating engine has exceeded the maximum manifold pressure allowed by the manufacturer?

• A. Overcontrolling
• B. Overboost
• C. Overpower
• D. P-static

Answer: (B)

When manifold pressure exceeds the maximum allowed by the manufacturer, the engine is in an overboost condition. Manifold pressure is the pressure in the intake system as air is drawn into the cylinders, and pushing that pressure beyond the design limit raises cylinder pressures beyond what the pistons, valves, and other components are built to withstand. Sustained overboost can lead to detonation, piston damage, or other serious engine failures, so boost systems and regulatory limits are set to prevent this. That’s why this situation is described as overboost. The other terms don’t describe this specific condition: overcontrolling isn’t a standard term for engine pressure limits, overpower refers to producing more power in general, and P-static relates to airframe static pressure, not engine manifold pressure.