Airworthiness directives, and the ones that change what an airplane is worth
An AD is a mandatory fix issued when the FAA finds an unsafe condition in a type. Most are minor. A few are the difference between a good deal and a very expensive mistake.
An airworthiness directive is a legally enforceable order from the FAA addressing an unsafe condition found in a particular aircraft, engine, propeller or component. Compliance is not optional. An aircraft with an overdue AD is not airworthy, which means it may not legally be flown, which means it is worth substantially less than the same aircraft with a clean compliance record.
For a buyer, ADs are one of the few places where paperwork translates directly into money.
One-time versus recurring
A one-time AD is done once and signed off forever. Inspect this bracket, replace that fitting, done.
A recurring AD comes back at an interval — every hundred hours, every annual, every so many cycles. These are the ones that matter for ownership cost, because they are a permanent line item attached to the type for as long as you own it. A recurring inspection that needs a specialist shop and a day of labour every hundred hours is a real and ongoing expense that never appears in a broker’s cost estimate.
Service bulletins are not the same thing
Manufacturers issue service bulletins and service letters recommending work. Under Part 91, these are generally not mandatory unless an AD adopts them or they are tied to a required inspection programme. Commercial operators live under different rules.
That does not make them ignorable. A bulletin is the manufacturer telling you something has gone wrong on other examples of your airplane. Skipping the recommended fix is a choice you may have to explain to an insurer, a mechanic or a buyer later.
How to check compliance before you buy
- Ask for the AD compliance record — a signed list, not a verbal assurance that “it’s all done”
- Cross-check it against the logbooks; entries should match the list
- Look specifically for recurring items and note when each is next due
- Ask the mechanic doing the pre-buy to review AD status as part of the inspection
- Search the FAA’s AD database yourself by make and model — it is public and free
A seller who cannot produce a compliance record is not necessarily hiding anything — plenty of owners keep sloppy paperwork — but reconstructing it is work, and it is work that should come off the price rather than out of your weekend.
When an AD ends a deal
Occasionally an AD appears that is expensive enough to change the economics of an entire type — a mandatory inspection of a structure that requires significant disassembly, or a replacement part that is scarce. When that happens, values for that type move, sometimes sharply.
If you are considering a type where a large AD is live or rumoured, the type club will be talking about nothing else. That is exactly why joining before you buy is the cheapest research available.
The walk-away case is an AD that cannot be economically complied with — where the fix costs a meaningful fraction of what the airplane is worth, or the part simply is not available. That is not a negotiation. That is a different airplane.