What regular task should be included in APU maintenance routines?

Measuring pressure and temperature levels is an essential task in APU maintenance routines because these parameters are critical for ensuring that the auxiliary power unit is operating within its designed specifications. The APU plays a vital role in providing electrical power and pneumatic pressure for engine starts and environmental control when the main engines are not running.

Regular checks of pressure and temperature levels help identify any abnormalities that may indicate potential issues, such as overheating or pressure loss, which could lead to APU failure if not addressed promptly. Monitoring these levels ensures safety, reliability, and optimal performance of the APU, directly impacting the aircraft's overall operational readiness.

Other tasks such as examining fuel reserves and reviewing historical performance data contribute to the APU's maintenance but are secondary to the immediate operational parameters that pressure and temperature levels provide. Updating pilot training manuals, while important for operational understanding, does not directly relate to the mechanical integrity or functional performance of the APU itself.