How is engine manifold pressure indicated in a piston aircraft?

• A. By the oil pressure gauge
• B. By the manifold pressure gauge, typically in inches of mercury (Hg)
• C. By the fuel pressure gauge
• D. By the temperature gauge

Answer: (B)

Engine manifold pressure in a piston aircraft is indicated by the manifold pressure gauge, which is typically calibrated in inches of mercury (Hg). This gauge measures the pressure within the intake manifold of the engine and provides the pilot with crucial information regarding the engine's performance and operating conditions. Manifold pressure is directly related to the engine's power output; understanding this pressure allows the pilot to optimize engine performance during various phases of flight.

The manifold pressure gauge works by reading the absolute pressure inside the manifold. As the engine operates, changes in throttle settings and the aircraft’s altitude will affect this pressure. For instance, when the throttle is opened, manifold pressure generally increases, providing more air-fuel mixture to the cylinders and resulting in higher power output.

The other instruments mentioned do not measure manifold pressure: the oil pressure gauge reflects the pressure of the engine's lubricating oil, the fuel pressure gauge measures the fuel delivery system pressure, and the temperature gauge indicates the temperature of various engine components. Each of these gauges serves different purposes in monitoring the aircraft's systems but does not provide information on engine manifold pressure.