What is a certified change to a type design called?

• A. Repair Design Certificate (RDC)
• B. Supplemental Type Certificate (STC)
• C. Type Design Approval
• D. Endorsement Certificate

Answer: (B)

A certified change to a type design is referred to as a Supplemental Type Certificate (STC). An STC is a formal approval issued by aviation authorities that allows for modifications or changes to an aircraft's original design, which is detailed in its Type Certificate. This might involve alterations such as new equipment installations, structural changes, or modified operational capabilities that are not covered by the initial Type Certificate.

The process for obtaining an STC involves thorough evaluation and compliance confirmation with safety, performance, and regulatory standards, ensuring that the modification does not negatively impact the aircraft's safety or performance. This process addresses new engineering designs or enhancements while maintaining full regulatory compliance.

Other options do not fit the definition of a certified change to a type design. For instance, a Repair Design Certificate (RDC) pertains exclusively to certain repairs that may not comply with the original design, while Type Design Approval generally refers to the initial certification of an aircraft design rather than modifications. An Endorsement Certificate is not a recognized term in this context, further differentiating it from the established process for STCs. Thus, the STC is the correct term for any certified changes made to a type design of an aircraft.