During a 100-hour engine inspection, which of the following is typically not checked before approval for return to service?

During a 100-hour engine inspection, the focus is on ensuring that critical systems of the engine are in proper working condition and safe for operation. One of the aspects typically not checked as part of this routine inspection is alternator and starter operation.

While these components are important for the overall functionality of the aircraft, the 100-hour inspection primarily emphasizes the health and performance of the engine itself—specifically elements more directly tied to engine performance, such as fuel system integrity, oil levels, and engine compression. These checks ensure that the engine is performing optimally and does not have any immediate issues that could affect safety or operational efficiency.

In contrast, the alternator and starter are part of the electrical system and, while they should be operational, their detailed checking may fall under a different maintenance schedule or inspection regularity, such as the annual inspection or specific electrical system checks. Thus, while their operation is important, they do not fall under the critical checks mandated within the context of a 100-hour inspection.