14 CFR § 65.87

Except as provided in paragraph (b) of this section, a certificated mechanic with a powerplant rating may approve for return to service a powerplant or propeller or any related part or appliance, after that person has performed, supervised, or inspected its maintenance or alteration (excluding major repairs and major alterations). In addition, a certificated mechanic with a powerplant rating may perform the 100-hour inspection required by part 91 of this chapter on a powerplant or propeller, or any part thereof, and approve for return to service.

A certificated mechanic with a powerplant rating can approve for return to service a powerplant or propeller, or any related part or appliance, of an aircraft with a special airworthiness certificate in the light-sport category after performing and inspecting a major repair or major alteration for products that are not produced under an FAA approval, provided the major repair or major alteration was authorized by, and performed in accordance with instructions developed by, the manufacturer or a person acceptable to the FAA.