What routine action is necessary for monitoring the health of the APU?

Monitoring the health of the Auxiliary Power Unit (APU) is critical for ensuring its reliability and efficiency, particularly in the C-130J. Conducting performance checks, which include pressure and temperature readings, is essential because these metrics provide direct insight into the operating conditions of the APU. By regularly measuring these parameters, maintenance personnel can identify any irregularities or deviations from normal operating ranges that could signal potential problems.

For instance, if temperature readings are higher than expected, this might indicate overheating or insufficient cooling, while pressure readings can reveal issues related to fuel or oil systems. Early detection of these issues allows for timely corrective actions, thereby preventing more significant failures and ensuring that the APU operates effectively when needed.

Other options like updating the operational manual, performing fuel efficiency tests, or inspecting for corrosion contribute to overall maintenance practices but do not directly assist in real-time monitoring of the APU's performance and health status. Therefore, focusing on performance checks is the most effective routine action for maintaining APU reliability.