An airworthiness directive, or AD, is not a recommendation. It is a legally enforceable order from the FAA requiring an owner to inspect, repair, modify, or in rare cases stop flying a specific aircraft, engine, propeller, or installed part because the FAA has determined it has an unsafe condition. Under 14 CFR 91.403, keeping the aircraft in compliance with every applicable AD is the owner's legal responsibility — not something the FAA tracks or enforces for you automatically.
Where ADs come from
ADs are issued in two ways. An emergency AD takes effect immediately, before public comment, when the FAA judges the unsafe condition urgent enough that waiting would be dangerous. A standard AD goes through the normal Federal Register process — usually a Notice of Proposed Rulemaking followed by a final rule — and gives owners a compliance window. Either way, the authoritative published text lives in two places: the Federal Register and the FAA's own Dynamic Regulatory System.
How to search by make and model
ADs are issued against a specific product — an airframe make/model, an engine model, a propeller model, or an installed appliance — not against an individual tail number. That means the search you want before buying is by make and model, not by N-number: pull up every AD that has ever applied to that airframe and engine combination, then check the logbooks for the sign-offs proving each one was actually complied with. Every model page on this site links directly to a pre-built Federal Register AD search for that exact make and model, so you don't have to guess at spelling or model-code variants.
Why this belongs in your pre-purchase checklist
A logbook that is missing an AD sign-off is not a paperwork technicality. It means the aircraft may be flying out of compliance with a federal safety order right now, and bringing it current can range from a cheap inspection to a component replacement that costs real money. This is a different question from accident history — a clean NTSB record says nothing about open ADs, and a fully AD-compliant aircraft can still have a hidden accident under a prior tail number. Check both.