The two kinds of FAI
A full FAI is a complete, documented verification of every design characteristic of a part: every balloon on the drawing, every material and special process, every functional test. It's the baseline that proves your production process can make the part as designed.
A partial FAI, often called a delta FAI, re-verifies only the characteristics affected by a change since the baseline full FAI. Everything else is covered by the earlier report. A partial FAI isn't a lighter version of a full one. It's a full verification of a smaller, well-justified set of characteristics.
Both apply to detail parts and to assemblies. An assembly FAI covers the characteristics created at assembly and references the FAIs of the detail parts and sub-assemblies that go into it.
When you need a full FAI
The normal case is a new part: the first production run of a part number you haven't made before, or haven't made for this customer before. A full FAI is also the usual answer when so much has changed that a partial FAI would cover most of the part anyway, or when there's no valid baseline FAI to build on, for example because the previous report is missing or was never accepted.
Customers can also simply require a full FAI. If the purchase order or the customer's supplier quality requirements say "full FAI", that's what it is, whatever the standard would allow.
Events that trigger a new FAI
AS9102 lists events after which the organization must perform a full FAI or a partial FAI covering the affected characteristics. Paraphrased, they are:
- A design change affecting fit, form or function, typically a new drawing revision.
- A change in manufacturing source, process, inspection method, location, tooling or materials that could affect fit, form or function.
- A change to the NC program, or translating it to another medium, that could affect fit, form or function.
- A natural or man-made event that may have affected the manufacturing process, such as a fire, flood or major machine crash.
- A lapse in production of two years, or as the customer specifies.
Notice the repeated phrase: could affect fit, form or function. That's the judgement at the heart of every partial FAI decision.
Worked examples
| What changed | Typical answer |
|---|---|
| New part number, first production run | Full FAI. |
| Drawing goes from Rev C to Rev D; one hole diameter tightened | Partial FAI on that hole, plus anything the change could affect (position of that hole, a mating feature). |
| Rev D only corrects a title block typo | Often no new FAI, but document why. Some customers want a partial FAI for every revision regardless. |
| Job moved from one 5-axis machine to a different model | Partial FAI on characteristics made on that machine, and the NC program if it was re-posted. |
| Heat treat moved to a new approved supplier | Partial FAI covering Form 2 for that process, plus characteristics the process can affect (hardness, distortion-sensitive dimensions). |
| Production restarts after two years idle | New FAI. Whether full or partial depends on what's changed in the meantime and on the customer. |
| Production moved to a new building | Often full, because nearly every process is affected. Check with your customer. |
These are typical answers, not rules. Your customer's requirements and your own risk assessment decide each case.
How to document a partial FAI
A partial FAI is judged on its justification. Make it easy for the reviewer:
- Mark it as partial on Form 1 and give the baseline part number and revision of the full FAI it builds on.
- State the reason. "Drawing Rev C to D, ECN 4471: hole 7 diameter tolerance changed" is better than "revision change".
- List the characteristics in scope and why each is included. Include characteristics the change could affect, not just the ones that changed on paper.
- Keep balloon numbers stable across revisions, so the scope is easy to trace back to the baseline FAI.
- Re-verify Form 2 items if the change touched materials, special processes or their sources.
- Keep the baseline FAI on file and retrievable. A partial FAI without its baseline is incomplete.
Common mistakes
- Scoping too narrowly. Re-checking only the changed dimension, not the features it relates to.
- No baseline. Claiming a partial FAI against a full FAI that was never accepted, or can't be found.
- Forgetting process triggers. Drawing changes are obvious. A new machine, a re-posted program, or a new special process supplier are easier to miss.
- Losing track of the two-year clock. Low-volume parts can quietly lapse between orders.
Where software helps
The hard part of a partial FAI is knowing exactly what changed between two drawing revisions. Deburr compares revisions side by side, carries balloons forward with stable numbers, flags characteristics that were added, removed or changed, and fills the partial FAI scope from that comparison for you to review. It starts with a ballooned drawing, which you can try for free with the AI ballooner.
Related: How to balloon a drawing · AS9102 Form 3 explained
From the blog: PPAP vs FAI · First article vs first piece inspection · What an FAI costs