Strongest signal first:
- The part number stamped on your part, named in the directive. Punctuation is ignored, so a dash cannot cause a miss.
- The FAA’s own manufacturer and model fields for the directive.
- The manufacturer, spelled either way. A plate reading “HARTZELL PIQUA, OHIO” still meets a directive written against “Hartzell”. A spelling the FAA never uses can be confirmed as the right company, and after that every part carrying that plate matches.
- The prose. Where a directive states no applicability that can be compared, its full text is searched for your part’s series.
The airframe is checked as soon as the aircraft is added, and each part is checked as it is recorded. Directives plainly written against another manufacturer’s aircraft are set aside with the reason stated. They are listed, not removed.
The matching is recomputed when something it depends on changes: a part recorded or edited, the nightly sync bringing new directives, a manufacturer name confirmed.