Supplemental Type Certificate

A supplemental type certificate (STC) is issued by the aviation Authority approving a product (aircraft, engine, or propeller) modification.
When a person develops the design of a change to a type‐certificated aircraft, aircraft engine or propeller, that design must be approved before it can be used. A Supplemental Type Certificate is one method of obtaining approval.
The STC defines the product design change, states how the modification affects the existing type design, and lists serial number effectivity. It also identifies the certification basis listing specific regulatory compliance for the design change. Information contained in the certification basis is helpful for those applicants proposing subsequent product modifications and evaluating certification basis compatibility with other STC modifications.