Type Certificate Data Sheets, Airworthiness Limitations, and Instructions for Continued Airworthiness
The documents and what each governs
The type certificate data sheet is the FAA's summary of the approved design: eligible models and serial numbers, engine and propeller combinations, airspeed limitations, maximum weights, center of gravity range and datum, control surface travels, required equipment, and required placards. The approved flight manual or placards carry operating limitations. The instructions for continued airworthiness (ICA) - maintenance manual, overhaul manuals, structural repair manual, and the airworthiness limitations section - carry the maintenance program.
The airworthiness limitations section
Section 43.16 requires every person performing maintenance to use the mandatory replacement times, inspection intervals, and related procedures in the airworthiness limitations section. That section is FAA-approved; its content is enforceable exactly as an AD would be, and changes to it require FAA approval. An owner, operator, or inspector may not extend an airworthiness limitation, substitute a different interval, or continue in service past a life limit.
Traps
Operating limitations in the flight manual are enforced through operating rules; airworthiness limitations are enforced through maintenance rules. Both are FAA-approved, but the airworthiness limitations section is the one that overrides a convenient shop schedule. ICA applicability follows the installed design - including STC instructions, which must be obtained and followed after an alteration. If an STC changes an airworthiness limitation, that change must be FAA-approved through the STC process.
Rule of thumb
Sort every requirement by its source. If it appears in the airworthiness limitations section or a TCDS limitation, treat it as an AD. If it appears in a maintenance manual's recommended practices or a service bulletin, it is guidance unless another rule or program adopts it.