Buyer's handbook

Understanding airworthiness directives — the legally binding list

Of all the public records on an aircraft, airworthiness directives are the ones with legal teeth — and the ones a database can help with least. Understand why, and you understand the single most important paperwork check of any pre-buy.

What an airworthiness directive is

An airworthiness directive (AD) is a legally enforceable FAA rule. When an unsafe condition is found in a type of aircraft, engine, propeller or component, the FAA issues an AD requiring an inspection, a repair, a replacement, or an operating limitation on every affected aircraft. Complying is not optional: an aircraft with an overdue AD is not airworthiness-legal to fly, full stop.

Crucially, ADs apply by type or by component, not by tail number. If your make and model — or the specific engine or propeller installed — is named in an AD, that AD applies to your aircraft the moment you own it.

One-time versus recurring — the distinction that costs money

Some ADs are satisfied once: do the inspection or the modification, sign it off, and it is closed forever. Others are recurring: they must be re-complied with at set intervals — every so many hours, or every so many calendar months — for the life of the aircraft. Recurring ADs are where buyers get hurt:

A recurring AD that is due soon is a scheduled bill you inherit at closing.
A recurring AD that is overdue is both a grounding item and a warning sign about how the aircraft was maintained.
Terminating action matters: some recurring ADs can be closed permanently by a one-time modification. Knowing whether that was done changes the aircraft's cost of ownership.

Why no database can prove compliance — only logbooks can

This is the point everything else rests on. A database can tell you which ADs apply to a make and model. It cannot tell you whether a specific airframe complied — because compliance is an action a mechanic performed and recorded, and that record lives in the aircraft's logbooks, nowhere else. Anyone selling you a "guaranteed AD-clear" status from public data alone is selling you something the public data cannot contain.

What a good records service does — and what our model buyer's guides and reports do — is build the list of applicable ADs and flag the recurring ones, so you arrive at the pre-buy knowing exactly which numbers to hunt for in the logbooks.

A note on coverage: our AD database starts in the 1990s

Be honest about the tool's limits. We build AD applicability from the Federal Register, whose electronic record we track from the mid-1990s forward. For an older airframe, the full applicable AD list is longer than what any post-1990s slice can show — early ADs, and many engine and propeller ADs, predate that window. Treat our matched list as a strong starting point, not a complete legal register, and build the authoritative list at the FAA's Dynamic Regulatory System.

The authoritative source: drs.faa.gov — free, complete, and laborious to search by hand.

The pre-buy method for ADs

Build the applicable AD list for the airframe, engine and propeller — by make/model and by the parts actually installed.
Flag every recurring AD, and note its interval and next due point.
At the pre-buy, have your mechanic tick each AD off against the logbook entries — number by number, with dates and signatures.
For recurring ADs, confirm whether a terminating modification closed it, or whether it is still live.
Price every gap as real money: an overdue recurring AD is spend you commit to the moment you sign.

Get the matched AD list for one aircraft

A TailGuard report ships the airworthiness directives matched to a specific aircraft's type — open and recurring status called out — next to its serial-verified NTSB history, its Service Difficulty Reports, its ownership timeline and its public record coverage. It tells you which numbers to check; the logbooks prove them.