The most expensive part in a production run is often the first one, because it is the only chance to catch a misunderstanding before it multiplies by a thousand. A first article inspection takes that opportunity seriously: it verifies every characteristic on the drawing, on the first part produced from your actual production tooling, setup, and process. Buyers in aerospace, medical, and defense programs require it for exactly that reason. This guide explains what a first article inspection checks, how AS9102 structures the paperwork, when it becomes necessary, and how a thorough FAI reduces the risk of an entire production order.
What Is a First Article Inspection?
A first article inspection, usually shortened to FAI, is a complete dimensional and functional report on a representative part from the first production run. Every characteristic on the print is measured and recorded against its stated requirement: each diameter, depth, radius, position tolerance, profile call, surface finish spec, and marking requirement. That is what separates an FAI from approving a sample, since a sample might come from prototype machining or a hand-tuned setup. The FAI part must come from production tooling, on the production machine, through the production process, so the report describes what your order will actually receive.
The output is a balloon-style report. Numbered characteristics appear in one column, the requirement and its drawing reference in the next, and the measured result plus the gauge used in the third. Once the buyer’s quality group reviews and approves the package, the supplier has a documented baseline, and production release proceeds against it.
Why the FAI Protects Both Buyer and Supplier
The inspection catches the errors that later sampling misses. A position tolerance read as a simple plus-minus dimension, a datum interpreted differently on the floor than in the CAD model, a hidden edge-break or marking requirement that never reached the traveler. The FAI puts every balloon on paper and forces both sides to agree on what each one means before hundreds of parts are made.
For the supplier, the same document is protection in reverse. Approval of the report means the customer cannot later reject parts on an interpretation the customer itself signed. That shared baseline reduces arguments at receiving inspection and settles disputes about process changes. The interpretation skill an inspector needs is the one GD&T demands, and our GD&T basics for CNC buyers article shows where misreads usually happen.
Inside the AS9102 FAI Forms
In aerospace work, the first article inspection is formalized as AS9102, an SAE standard with a three-form structure referenced by AS9100 quality systems. Form 1 identifies the part and the accountability: revision level, drawing number, and the responsible buyer, design activity, and manufacturer whose signatures make the package official. Form 2 lists every product and process characteristic together with its traceable source, including material specifications and special processes such as heat treat and plating, with their processor approvals.
Form 3 is the dimensional report proper. Characteristics are numbered to match the ballooned print, and each row carries the nominal requirement, the tolerance, the measured value, and the gauge or method used with its calibration status. The three forms cross-reference one another, so every measurement traces to a drawing balloon, every balloon traces to a requirement source, and the revision on Form 1 is the revision actually measured. Even on programs that do not formally demand AS9102, requiring that structure gives a buyer a consistent, reviewable package.
When a New FAI Becomes Mandatory
Aerospace contracts require a first article inspection on new parts, the product-acceptance discipline behind aerospace CNC machining programs. Beyond contractual triggers, the list is practical: a new part number entering production, a design or drawing revision that changes fit or function, a process change such as moving from three-axis to five-axis, a new machine, a new site, a new source, or a production lapse long enough for tooling memory to decay. Each event invalidates the old baseline, and the new-baseline logic connects to how tolerance stacks behave; see our CNC machining tolerances guide.
For non-regulated buyers, a scoped FAI remains cheap insurance on a high-volume order. If a part carries more than a handful of tolerances, or if the program cannot absorb a late surprise, the inspection earns its keep. The cost is one setup’s worth of metrology time, weighed against an entire run built on a shared misunderstanding.
What the Dimensional Report Must Include
A useful FAI report stands alone in an audit. It shows every characteristic with its exact requirement and unit. It records actual measured values, not just pass or fail. It names the gauge used for each reading and that gauge’s calibration status. It identifies the operator and date, and it attaches the ballooned drawing so a reviewer can trace each callout to a measurement without a phone call.
Attributes matter as much as dimensions. Surface finish callouts deserve their own lines with the Ra value and measurement conditions, since roughness is the characteristic most often skipped in a hurried report; our surface roughness Ra guide explains what a defensible reading looks like. Plating thickness verification, marking, and any functional test the print demands belong in the report too. If a characteristic cannot be measured with available tooling, the FAI is where that gap surfaces, not after the run.
If the FAI Fails: What Happens Next
A failed FAI means the system worked, not that it broke. The correct response follows the supplier’s nonconformance process: identify each failed characteristic, determine whether the cause was setup error, tooling, gauge capability, or a genuine misunderstanding of the drawing, then document the correction. A setup error is fixed and the affected part re-measured. An interpretation dispute goes back to the design activity for clarification or a drawing change.
Re-qualification follows the significance of the fix. When the change touched the production process, most buyers require a new or delta FAI covering the affected characteristics, with the original package attached for traceability. A supplier with a mature quality system runs this loop without drama, because nonconformance and corrective action are already its native language; our CNC machining quality control article places that loop in context.
Is a first article inspection the same as approving a sample?
No. A sample approves an example. A first article inspection verifies every characteristic against the controlling drawing, on a part made by the production process, with recorded gauge evidence. The distinction matters because a sample can look right while hiding a process that cannot repeat it, which is precisely the risk the FAI package is built to eliminate.
How long does a first article inspection take?
The schedule is driven by characteristic count, gauge availability, and the metrology queue. A simple bracket with thirty balloons may take a day. A machined housing with two hundred characteristics, geometric tolerances, and finish requirements can take a week or more. A supplier quoting FAI turnaround should be able to explain the metrology plan behind the number, including which features go to the CMM and which need custom fixtures.
Does every new order need a new first article?
Not when nothing relevant has changed. The approved baseline stands until something that could affect conformity moves: a drawing revision, a process or machine change, a new site or source, or a long production lapse. Ordering a fresh full FAI for every purchase order adds cost without adding information, while letting real process changes pass without one quietly abandons the protection the whole exercise exists to provide.
