14 CFR §145.217

1. (a)A certificated repair station may contract a maintenance function pertaining to an article to an outside source provided—
   1. (1)The FAA approves the maintenance function to be contracted to the outside source; and
   2. (2)The repair station maintains and makes available to its responsible Flight Standards office, in a format acceptable to the FAA, the following information:
      1. (i)The maintenance functions contracted to each outside facility; and
      2. (ii)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.
2. (b)A certificated repair station may contract a maintenance function pertaining to an article to a noncertificated person provided—
   1. (1)The noncertificated person follows a quality control system equivalent to the system followed by the certificated repair station;
   2. (2)The certificated repair station remains directly in charge of the work performed by the noncertificated person; and
   3. (3)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.
3. (c)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.