A supplemental type certificate is a type certification approval issued for a major modification to an already certified aircraft, engine, or propeller. In aerospace localization it appears in modification documentation, technical specifications, certification binders, and sales material, often abbreviated as STC, where it is used to show that the changed configuration remains compliant with applicable airworthiness standards and is distinct from the original type certificate.
Translators encounter STC in aircraft modification proposals, engineering orders, installation manuals, and regulatory certification packages. It is common in aftermarket avionics upgrades, interior changes, and cargo conversions. Localization must keep the abbreviation STC stable and clearly distinguish it from the original type certificate, because certification references and maintenance records may cite both documents side by side.
A common mistake is translating supplemental type certificate as “additional certificate” or “modification license,” which obscures the type certification basis and may make the approval sound merely administrative. Another is confusing the STC holder with the original equipment manufacturer, leading to incorrect installation authorization and maintenance responsibility statements in localized technical documentation.
EASA and CE certification impose language requirements on maintenance and safety documentation. These terms carry airworthiness and liability implications, so they are rendered against the governing standard rather than translated freely.
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