The short answer
A Type Certificate Data Sheet (TCDS) is the FAA document that records the certified design data for an aircraft, engine, or propeller type: approved models, engine and propeller options, operating limitations, and required placards. It defines what the product's approved configuration is.
How the TCDS gets used
Mechanics and inspectors reference the TCDS to confirm an aircraft matches its certified configuration — correct engine model, propeller, control-surface travels, placards, and serial-number applicability. It's the baseline against which alterations (via STC or field approval) are measured.
TCDSs are public documents searchable on the FAA's website by make, model, or certificate number, and they're often the fastest authoritative answer to "what engine is this airframe certified with?"
Related terms and reading
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