Built a deterministic 5-stage compliance resolution engine that takes an aircraft's make, model, serial, and installed components and returns the precise set of currently effective ADs. Stages run manufacturer match, model hierarchy traversal, serial range intersection with exclusions, supersession DAG, and equipment condition evaluation, with no LLM calls at resolution time because compliance results have to be reproducible. Added a model_ad_cache table that pre-computes stages 1-2 per product model, so adding a new aircraft only has to run stages 3-5 against cached candidates. Wired it into the refresh endpoint and the aircraft compliance pipeline task behind a use_engine flag, with the old manufacturer-only matcher still reachable as a fallback.