Supplemental Type Certificate

A Supplemental Type Certificate (STC) is an approval issued by an aviation authority (FAA, EASA, ANAC, etc.) for a modification to an aircraft, engine, or propeller that changes the original type design. STCs allow modifications and improvements to be made to aircraft after their initial certification without requiring a new type certificate.

Common modifications requiring STCs include:

• Avionics upgrades (new GPS, glass cockpit retrofit)
• Engine conversions (e.g., piston to turbine)
• Structural modifications (cargo door installation, fuel tank additions)
• Performance enhancements (winglets, STOL kits)
• Interior reconfigurations
• Wi-Fi and connectivity installations

The STC holder (typically the modification designer or installer) must demonstrate through testing and analysis that the modification meets all applicable airworthiness standards and does not adversely affect the aircraft's safety or performance. STCs can be transferred, licensed, or sold, and they have significant commercial value — particularly popular avionics or performance STCs for widely-used aircraft types.