A used-component quote almost always carries one line near the bottom: AD/SB status available on request. On ageing fleets that line gets read as a formality. It is the opposite. The airworthiness directive and service bulletin dossier is where the legal standard and the commercial standard for a used part diverge most sharply — and the cost of the divergence lands on the operator who installs the part, not on the seller who shipped it.

The short version: an airworthiness directive becomes enforceable against you the moment the part is on your aircraft, a service bulletin usually is not enforceable at all, and for a loose component nothing in the rules obliges the seller to hand you either record. Whatever you receive, you receive because you wrote it into the purchase order before you paid.

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What an airworthiness directive attaches to

US airworthiness directives are not guidance. Under 14 CFR 39.3, they are “legally enforceable rules that apply to the following products: aircraft, aircraft engines, propellers, and appliances.” The word that matters to a parts buyer is appliances. An AD can therefore apply to a component in its own right and not only to the aircraft it is fitted to, which means the obligation follows the hardware rather than the tail number it happened to be hanging on last year.

Who carries that obligation is equally explicit. 14 CFR 39.7 states that “anyone who operates a product that does not meet the requirements of an applicable airworthiness directive is in violation of this section,” and 14 CFR 39.9 makes the violation repeat every time the aircraft is operated or the product is used. 14 CFR 39.11 describes what an AD can demand: inspections you must carry out, conditions and limitations you must comply with, and actions you must take to resolve an unsafe condition.

Read those three together and the commercial picture is plain. Under 39.7 the violation attaches to operating the product, so the seller of a non-compliant appliance is not the party in breach. The operator is, from the first flight, and again on every flight after it. A discount that reflects an unknown AD position is not a discount — it is a deferred maintenance bill with a regulatory exposure attached.

Airworthiness directive status: the four fields a record has to carry

Operators often ask what an airworthiness directive status sheet is supposed to look like. The US record-keeping rule answers that precisely. 14 CFR 91.417(a)(2)(v) requires records of “the current status of applicable airworthiness directives (AD) and safety directives including, for each, the method of compliance, the AD or safety directive number and revision date. If the AD or safety directive involves recurring action, the time and date when the next action is required.”

That is four fields per directive, the last of them whenever the directive recurs. A status sheet that leaves any of them blank is not yet a status sheet:

Field	What it answers	Common gap on used stock
AD number	Which directive is being addressed	Listed by subject line only, no number
Revision date	Which version of the directive was worked	Blank, or an older revision than the one now in force
Method of compliance	How the condition was resolved — inspection, modification, replacement	“C/W” with no reference to what was actually done
Next action due	When a recurring AD comes round again	Omitted entirely on recurring directives

The revision date is the field buyers skip and reviewers catch. A compliance entry against a superseded revision is not evidence of compliance with the directive in force today; it is evidence that somebody complied with an earlier version of it. On a component that has sat in a store for three years, that distinction is the whole inspection.

Service bulletins are mandatory only when an AD makes them mandatory

The second half of the dossier works on a completely different basis, and this is where sellers and buyers most often talk past each other.

FAA Advisory Circular 20-176A sets out the relationship. The actions an AD requires “can either be written directly into the regulatory portion (‘body’) of the AD, or another document such as an SB can be IBR’d” — incorporated by reference. Where that happens, the AC is unambiguous: “Compliance with an SB, or a portion of an SB, that is IBR’d in an AD is mandatory.”

But an AD can also simply point at a bulletin. In that case the same AC says: “An AD might also refer to an SB as an additional source of information about the subject of the AD. These SBs are not submitted for IBR approval; therefore, reference to these SBs does not constitute a regulatory requirement.”

Status of the bulletin	Regulatory weight	What to ask the seller
IBR’d into an AD	Mandatory — it is the AD	Compliance evidence, same four fields as any AD
Referenced by an AD for information	Not a regulatory requirement	Whether it was embodied, and at which revision
Manufacturer SB with no AD behind it	Not mandatory under the AD system	Embodied or not — it still moves the resale value

None of that makes bulletin history optional to collect. FAA AC 20-62E specifies, among the documentation to obtain with a used part, both “Airworthiness Directives (AD) status” at paragraph 10.b(1) and “Compliance or noncompliance with Service Bulletins (SB)” at 10.b(2). Note the wording of the second one: noncompliance is an acceptable answer. What is not acceptable is silence, because silence forces your maintenance organisation to assume the worst and price the assumption.

For a loose component, nothing transfers automatically

Here is the asymmetry that catches buyers who assume the aircraft rules carry over. 14 CFR 91.417(b)(2) requires that the records in (a)(2) — including the AD status — “shall be retained and transferred with the aircraft at the time the aircraft is sold.” That obligation is written about an aircraft. It is not a general rule for a component sold on its own out of a store.

It fits with the way AC 20-62E paragraph 10.b is written: guidance on what a buyer should obtain, rather than a duty placed on the seller. The regulatory system hands you the standard and leaves the enforcement of it to your contract. If the AD and SB status is not a stated condition of acceptance in the purchase order, you have no mechanism to reject the part when the dossier turns out to be two lines on a delivery note.

The same logic underlies the trap we covered in back-to-birth records for engine modules: the regulator asks for current status shown with confidence, while the market asks for a continuous trail, and the buyer who does not know which standard is being quoted pays for the wrong one.

The acceptance checklist to put in the purchase order

Treat this as contract language, not as a wish list. Each line maps to a source above.

Clause	Why it is there
Airworthiness directive status listed by component part number and model, not by the donor aircraft alone	ADs attach to appliances under 39.3; the donor tail number is not the applicability test
For each AD: number, revision date, method of compliance, next action due	The four fields of 91.417(a)(2)(v)
Confirmation that each cited revision is the revision currently in force	Compliance against a superseded revision is not current compliance
Bulletins split into IBR’d and referenced	Only the IBR’d ones are mandatory per AC 20-176A 1-8(a)
A positive statement of SB compliance or noncompliance	AC 20-62E 10.b(2) accepts either; it does not accept silence
Dossier delivered before payment release, not with the shipment	Nothing transfers a loose part’s records automatically

The last clause is the one that changes outcomes. A dossier that arrives in the box with the part arrives after the leverage is gone. On an escrow-backed transaction the documentation review sits before release, which is the point in the sequence where a missing revision date is still a negotiation rather than a write-off.

Why this bites hardest on ageing fleets

Older types accumulate directives, and the components that serve them have usually passed through several operators in several jurisdictions. Each transfer is a chance for the AD trail to thin out — not through fraud, but through ordinary attrition: a shop that closed, a CAMO that changed hands, a status sheet exported from a system nobody still runs.

Operators running these fleets in Africa, South Asia and Southeast Asia feel it twice over. The first time is at installation, when the maintenance organisation refuses the part. The second is at disposal, when the same thin dossier that you accepted cheaply reappears as a discount you have to grant. The documentation discipline that protects the first transaction is the same discipline that preserves the value of the second, which is the argument we made about traceability to a certificated source and about release-document checks for operators without a CAMO.

Practical rule for the desk: a used component is not cheaper because its AD and SB history is thin. It is cheaper because someone has priced in the work of reconstructing it, and that work is going to be yours.

When you issue the next requirement, put the documentation clause in the request itself rather than in the follow-up email. Submit the RFQ with your acceptance conditions stated, or work the verified parts catalogue where sellers are identified before the conversation starts. New requirements also go out on our live Telegram feed.