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I’ve seen the acronyms TSO and STC used together. What’s the difference?

April 26, 2017Acronyms I’ve seen STC TSO Used

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I’ve seen the acronyms TSO and STC used together. What’s the difference?

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A. TSO is a Technical Standard Order, and it describes the minimum performance standard for a system or component. An STC is a Supplemental Type Certificate. An STC is a document issued by the Federal Aviation Administration approving a product (aircraft, engine, or propeller) modification. The STC defines the product design change, states how the modification affects the existing type design, and lists serial numbers of the component affected by the change. Safe flight using GPS equipment depends on airworthiness (does it have a TSO?), installation (was it installed per AC 20-138 or AC 20-130a), and signoff (was it done properly per TC/STC or Form 337).