What does a Supplemental Type Certificate (STC) authorize in aviation?

• A. Approval to modify an aircraft to operate on automotive gasoline.
• B. Approval to repaint the aircraft.
• C. Approval to operate internationally.
• D. Approval for a minor maintenance task.

Answer: (A)

An STC is FAA approval for a major modification to an aircraft that changes its airworthiness basis. It authorizes installing or altering equipment or systems in a way that goes beyond routine maintenance or cosmetic work.

For example, making an aircraft able to operate on automotive gasoline involves changes to the fuel system and related components. That kind of significant modification requires an STC because it affects how the aircraft performs and remains airworthy.

Cosmetic repainting doesn’t change how the aircraft operates, so it doesn’t require an STC. Operating internationally is a regulatory status matter, not a modification approval. Minor maintenance tasks are covered by routine procedures and don’t involve an STC.

So, the option describing approval to modify an aircraft to operate on automotive gasoline reflects the purpose of an STC.