Which instrument can be used to check a manifold pressure gauge for accurate indications?

The sensitive altimeter is the correct instrument to use for checking a manifold pressure gauge for accurate indications. This is because both the manifold pressure gauge and the sensitive altimeter are influenced by atmospheric pressure. When the altimeter is set correctly, an accurate reading of the atmospheric pressure can be obtained, which can then be used to verify the manifold pressure gauge's indication.

The sensitive altimeter works by measuring the static pressure and showing the altitude of the aircraft based on that pressure. Since the manifold pressure gauge reflects the pressure of the intake manifold (in a piston engine) and is typically calibrated to indicate pressure relative to sea level, comparing its readings against a known reference (such as the altimeter's reading) allows for checks on accuracy. Variations in atmospheric conditions, such as temperature and pressure at a given altitude, are also accounted for using the sensitive altimeter.

Other instruments like the vertical speed indicator, artificial horizon, or airspeed indicator do not provide relevant pressure readings that can be tied back to the accuracy of the manifold pressure gauge. The vertical speed indicator measures the rate of ascent or descent, the artificial horizon indicates the aircraft's orientation relative to the earth, and the airspeed indicator shows the current speed of the aircraft. These instruments serve different