Which instrument can be used to verify the manifold pressure gauge by referencing altitude information?

Which instrument can be used to verify the manifold pressure gauge by referencing altitude information?

• A. Airspeed indicator
• B. Attitude indicator
• C. Altimeter
• D. VSI

Answer: (C)

The main idea here is that the manifold pressure gauge is a measure of the pressure inside the engine’s intake, which is tied to the ambient atmospheric pressure that changes with altitude. To verify it, you need a reference for what the ambient pressure should be at your current altitude. The altimeter directly measures ambient static pressure (through the pitot-static system) and, knowing your altitude, provides the reference you need to compare against the manifold pressure reading. If the manifold pressure matches the expected ambient pressure at that altitude (accounting for throttle and ISA conditions), the gauge is functioning properly. The other instruments do not provide a reliable ambient-pressure reference for this check.

The main idea here is that the manifold pressure gauge is a measure of the pressure inside the engine’s intake, which is tied to the ambient atmospheric pressure that changes with altitude. To verify it, you need a reference for what the ambient pressure should be at your current altitude. The altimeter directly measures ambient static pressure (through the pitot-static system) and, knowing your altitude, provides the reference you need to compare against the manifold pressure reading. If the manifold pressure matches the expected ambient pressure at that altitude (accounting for throttle and ISA conditions), the gauge is functioning properly. The other instruments do not provide a reliable ambient-pressure reference for this check.