What tool is typically used for checking the governor's operation on a constant-speed propeller?

A tachometer is the appropriate tool for checking the governor's operation on a constant-speed propeller. This instrument measures the engine's RPM (revolutions per minute) and allows the technician to observe how the propeller governor responds to changes in engine speed. When the RPM increases or decreases, a well-functioning governor should adjust the blade angle of the propeller to maintain the set RPM, providing insights into the system's performance.

Using a tachometer is crucial because the primary function of a constant-speed propeller is to allow the pilot to set a desired engine speed, which the governor then maintains by adjusting the propeller's blade pitch. If the RPM readings are inconsistent or do not reflect the expected operation of the governor, it may indicate a problem that requires further investigation.

In contrast, a pressure gauge would measure oil or fuel pressure, which is not directly related to the operation of the governor, while an ammeter measures electrical current and a torque wrench is utilized to ensure proper tension on bolts and fasteners. Thus, they do not provide the necessary information regarding the governor's performance in a constant-speed propeller system.