FAA Federal Aviation Regulations (FARS, 14 CFR)

(a) If the Administrator finds that a product for which an STC was issued under this subpart does not meet the applicable airworthiness requirements, or that an unsafe feature or characteristic caused by a defect in design or manufacture exists, the DAS, upon notification by the Administrator, shall investigate the matter and report to the Administrator the results of the investigation and the action, if any, taken or proposed.

(b) If corrective action by the user of the product is necessary for safety because of any noncompliance or defect specified in paragraph (a) of this section, the DAS shall submit the information necessary for the issue of an Airworthiness Directive under Part 39.