Delta FAI explained: when a partial first article inspection is required

The part has been in production for three years without a hiccup. Then your anodising vendor shuts down, you qualify a new one, and your customer's supplier quality engineer emails: "Please submit a delta FAI for the affected characteristics." If you are now wondering whether that means re-measuring all 214 balloons on the drawing — it doesn't. That is exactly what a delta FAI is designed to avoid.

A delta FAI (the standard calls it a partial FAI) re-verifies only the characteristics affected by a change, instead of repeating the complete first article inspection. Done correctly, it turns a 40-hour full FAIR into a half-day task. Done incorrectly, it is one of the most common reasons aerospace customers reject FAI submissions. This guide covers when a delta FAI applies under AS9102 Rev C, how to scope it, and how to document it so it passes review the first time.

What is a delta (partial) FAI?

AS9102 Rev C, published by SAE International, defines a first article inspection as a complete, independent verification of every design characteristic on a new part. But the standard explicitly recognises that once a baseline FAI exists, subsequent changes only need verification of what the change actually affects.

On AS9102 Form 1, field 19, you declare the submission as either a Full FAI or a Partial FAI. For a partial FAI you must also state the reason for the partial submission (e.g., "drawing revision B to C — changed characteristics only") and reference the baseline FAI report number the partial builds on. The baseline FAIR plus the delta FAIR together form the complete accountability record.

The events that trigger a new FAI under AS9102 Rev C

The standard requires a full or partial FAI whenever any of the following occurs. The scope column shows what customers typically accept — always confirm against customer-specific requirements, which can be stricter.

Note the two-year lapse rule: the clock runs from the completion of the last production run, not from the last FAI. Plants that build a part once a year rarely trip it; plants with sporadic spares orders trip it constantly without noticing.

Full FAI vs delta FAI at a glance

How to scope and document a delta FAI

1. Define the change precisely. Pull the engineering change order, process change note, or vendor change record. Write one sentence: "What physically changed about how this part is made?"
2. List the affected characteristics. Walk the ballooned drawing and ask, for each balloon: could this change alter this feature? A new coating vendor affects coating thickness and coated-surface finish callouts — not a hole pattern machined before coating. A new NC program affects every feature that program cuts.
3. Keep balloon numbers identical to the baseline. This is the single most important discipline. If balloon 47 was the ø5.00 ±0.05 mm hole in the baseline FAIR, it must be balloon 47 in the delta. Renumbering destroys traceability and forces reviewers to reject.
4. Complete Form 1. Tick Partial FAI, state the reason, reference the baseline FAI report number and its date.
5. Complete Form 2 only if needed. Required when raw material, a special process (heat treat, plating, NDT), or a functional test changed — with the new certs attached.
6. Complete Form 3 for affected characteristics only. Same columns as always: characteristic number, requirement, results, tooling, and nonconformance number if applicable.
7. Attach objective evidence. CMM reports, material certs, special process certs for the changed items, and the highlighted ballooned drawing.

If you don't yet have a clean baseline ballooned drawing, fix that first — our guide to the first article inspection checklist covers building one properly.

Worked example: coating vendor change on an aerospace bracket

Take a machined 7075-T6 bracket with 214 ballooned characteristics, in production since 2023 with an approved baseline FAIR. The anodising subcontractor changes. A change-impact review flags what the anodise line can influence:

• Balloon 188 — anodic coating thickness per MIL-A-8625 Type II, Class 2 (8–15 µm)
• Balloons 190–193 — surface finish Ra 1.6 on the four coated faces
• Balloon 201 — salt-spray requirement note (336 h per ASTM B117)
• Balloons 12, 15 — two post-anodise dimensions where coating build-up eats into the tolerance

The delta FAIR contains Form 1 (partial, reason: "change of anodising source"), Form 2 rows for the new special-process source with its NADCAP cert, and a Form 3 with 8 rows instead of 214. Elapsed effort: about three hours, most of it waiting on the salt-spray report.

Common delta FAI mistakes

• Treating "partial" as "less rigorous". Reviewers reject deltas with missing actuals or "attribute — accepted" entered against variable dimensions.
• Renumbering balloons after a drawing revision. Add new characteristics at the end of the sequence; never reshuffle existing numbers.
• Missing the production-lapse clock. Spares orders after a 30-month gap need an FAI decision before the parts ship, not after the customer asks.
• No baseline reference on Form 1. A partial FAIR that doesn't cite the full FAIR it amends is unreviewable.
• Ignoring customer overlays. Primes often add rules on top of AS9102 — some require full FAI on any facility move regardless of scope. Check the quality flow-downs on the PO.

If you're weighing aerospace FAI against automotive requalification, the equivalent mechanism on the automotive side is an interim or change-level PPAP submission — see our comparison of AS9102 vs PPAP.

How CadNexa handles delta FAIs

The painful part of a delta FAI is not the measuring — it's reconstructing the baseline. CadNexa keeps the ballooned drawing and its characteristic list as a saved project, so a delta becomes a filter operation: open the baseline project, select the affected balloon numbers, and generate a partial Form 3 that carries the identical numbering. For a new drawing revision, the auto-balloon tool (Smart Detect and Box+Balloon OCR modes) re-detects characteristics on the new sheet in minutes instead of an afternoon of manual bubbling. Reports export in AS9102, PPAP, and ISO formats — the same workflow described in our FAI report template guide.

Delta FAI FAQ

Is a delta FAI officially defined in AS9102?

The standard uses the term "partial FAI"; "delta FAI" is common industry shorthand for the same thing. Form 1 field 19 is where you declare full vs partial, the reason, and the baseline FAIR reference.

Does a two-year gap in production always force a full FAI?

AS9102 Rev C sets a two-year production lapse as a trigger for FAI activity, but whether the customer accepts a partial or demands a full re-run is their call. Ask your customer SQE in writing before you start measuring.

Can I reference the original FAIR instead of repeating unchanged characteristics?

Yes — that is precisely the mechanism. Unchanged characteristics remain covered by the baseline FAIR; the partial FAIR documents only the affected ones and cites the baseline report number on Form 1.

What is the PPAP equivalent of a delta FAI?

In the automotive world, process or design changes trigger a customer notification and, typically, a changed-scope PPAP resubmission at the level the customer specifies — conceptually the same "verify what changed" logic.

For step-by-step tutorials on ballooning and report generation, visit the CadNexa learning centre.