14 CFR § 145.217

A certificated repair station may contract a maintenance function pertaining to an article to an outside source provided—

The FAA approves the maintenance function to be contracted to the outside source; and

The repair station maintains and makes available to its responsible Flight Standards office, in a format acceptable to the FAA, the following information:

The maintenance functions contracted to each outside facility; and

The name of each outside facility to whom the repair station contracts maintenance functions and the type of certificate and ratings, if any, held by each facility.

A certificated repair station may contract a maintenance function pertaining to an article to a noncertificated person provided—

The noncertificated person follows a quality control system equivalent to the system followed by the certificated repair station;

The certificated repair station remains directly in charge of the work performed by the noncertificated person; and

The certificated repair station verifies, by test and/or inspection, that the work has been performed satisfactorily by the noncertificated person and that the article is airworthy before approving it for return to service.

A certificated repair station may not provide only approval for return to service of a complete type-certificated product following contract maintenance, preventive maintenance, or alterations.