Which component is NOT part of the APU electrical system?

• A. Oil pressure switch
• B. Holding relays
• C. Throttle control assembly
• D. Centrifugal switch assembly

Answer: (C)

The throttle control assembly is not considered a component of the APU electrical system because it primarily involves the mechanical regulation of fuel flow to the APU, rather than electronic or electrical control processes. The APU (Auxiliary Power Unit) electrical system typically encompasses components that are directly involved in managing power distribution, monitoring operational parameters, and ensuring safe operation through electrical means.

In contrast, components like the oil pressure switch, holding relays, and centrifugal switch assembly are integral parts of the electrical system. The oil pressure switch monitors oil pressure levels and sends signals to the control system, the holding relays manage the power to various APU components, and the centrifugal switch assembly plays a vital role in starting and stopping the APU by ensuring that it engages or disengages at the appropriate speeds. Understanding the function of these components within the overall operational framework of the APU is crucial for maintaining its efficiency and safety.