Who has the authority to approve a propeller for return to service after a 100-hour inspection?

The authority to approve a propeller for return to service after a 100-hour inspection is granted specifically to a mechanic with a powerplant rating. This is because the powerplant rating ensures that the mechanic possesses the specialized knowledge and training required to inspect, maintain, and repair aircraft engines and their associated components, including propellers.

The requirement for a mechanic to hold a powerplant rating underscores the importance of having qualified personnel involved in the maintenance of critical flight components. This ensures that all inspections are conducted in compliance with safety standards and regulatory requirements, which is essential for maintaining airworthiness.

The other choices do not have the same level of authority or qualifications necessary for this specific task. For instance, while any certificated repairman may have certain capabilities, they do not necessarily possess the required expertise in propeller maintenance unless they also hold a powerplant rating. Non-certificated mechanics, even when supervised, lack the legal standing to approve a propeller's return to service. Lastly, while FAA inspectors oversee certification and compliance, they do not perform repairs or inspections as part of their role; their function is more aligned with enforcement and oversight.