Delta FAI Workflow on a Multi-Revision Drawing: A Practical Guide

A supplier had been doing delta FAIs for two years on a high-volume aerospace bracket. Every revision triggered a delta. The configuration record on Form 1 had become so confused that the customer rejected the latest submission because they could not tell which serial numbers applied to which revision. The supplier had to rebuild the entire revision history from production records, supplier correspondence, and shop floor documentation. Three weeks of work just to clarify what was already in production.

Delta FAI is the workflow for revising an existing FAI when the drawing changes. AS9102 Rev C allows delta FAI in most cases where only some characteristics have changed. But the practical workflow — managing balloon number stability, configuration tracking, parallel revisions in production, and customer-specific delta acceptance criteria — is where shops trip up. The mechanics of which-row-changed are simple. The lifecycle management around delta FAI is where the time goes.

This guide covers the practical delta FAI workflow on multi-revision drawings: how to maintain configuration, what changes trigger delta vs full FAI, balloon number stability across revisions, and the documentation that keeps multi-rev production traceable. The fundamentals are covered in AS9102 FAI Drawing Revision Changes (Delta FAI) and How to Balloon a Drawing with Multiple Customer Revisions; this guide adds the multi-revision lifecycle workflow.

Delta FAI Workflow On Multi-Revision Drawing: When Delta Applies (vs Full FAI)

Per AS9102 Rev C, delta FAI applies when:

• Drawing revision changes some but not all characteristics

• Process changes affect some characteristics

• New supplier on existing part where only specific characteristics need re-verification

• Part not produced for 24+ months and is being restarted (partial delta)

Full FAI is required when:

• Most or all characteristics changed in the revision

• Material change affecting most properties

• Customer specifically requires full FAI for the revision

• Multiple process changes that affect the entire production sequence

The threshold between "delta acceptable" and "full required" is somewhat negotiable with the customer. Some customers prefer full FAI for any revision; others accept delta for revisions that change <20% of characteristics.

The Configuration Record

The most important field on Form 1 for multi-revision work is the configuration record. It must specify:

1. Drawing revision in effect for this FAI

2. Engineering Change Notice (ECN) governing the revision

3. Effectivity statement: which serial numbers this FAI applies to

4. Reference to previous FAI if this is a delta

5. Description of changes if this is a delta

A clean configuration record makes the customer's reviewer's job easy. A confused one creates rejection. Customer auditors look at configuration records first because they reveal whether the supplier has organizational control over the production lot.

Balloon Number Stability

The cardinal rule: unchanged characteristics keep their balloon numbers across revisions. This rule is documented in detail in How to Balloon a Drawing with Multiple Customer Revisions and the numbering rules in AS9102 Form 3 Characteristic Numbering Rules.

Why this matters: if balloon 23 in Rev A is "Ø.250 hole on Sheet 2," it must still be balloon 23 in Rev B. If you renumber, the customer's reviewer cannot trace this characteristic across revisions. Renumbering breaks the lifecycle traceability that delta FAI is supposed to provide.

The lifecycle management:

• New characteristic in Rev B: append at end with next sequential number (Rev A had 95 characteristics; new characteristic in Rev B is balloon 96)

• Spec changed in Rev B: keep balloon number, update the Form 3 row with the new spec

• Deleted in Rev B: mark Form 3 row as obsolete with revision reference; do not reuse the balloon number

The Multi-Revision Production Scenario

Many suppliers find themselves running multiple revisions in production simultaneously:

• Customer A is buying serial numbers 1-100 (Rev A)

• Customer A is buying serial numbers 101-200 (Rev B)

• Customer B is buying their own version of the same drawing (Rev A' with different customer-specific notes)

Each must be tracked separately for FAI purposes:

The Master Tracking Matrix

A spreadsheet or database that captures:

Drawing Number	Revision	Customer	Production Start	Production End	FAI Reference	Status
ABC-12345	A	Customer A	Jan 2025	Mar 2025	FAI-001	Complete
ABC-12345	B	Customer A	Apr 2025	Aug 2025	FAI-002-delta	Complete
ABC-12345	C	Customer A	Sep 2025	ongoing	FAI-003-delta	Active
ABC-12345	A'	Customer B	Feb 2025	ongoing	FAI-001b	Active

Balloon Mapping Across Revisions

Each balloon number has a mapping table showing how it appears across revisions:

Balloon #	Description	Rev A	Rev B	Rev C
1	Drawing tolerance standard	ISO 2768-mK	ISO 2768-mK	ISO 2768-mK
...
47	Ø.500 hole, Sheet 2	Active	Obsolete	—
...
95	Last char in Rev A	Active	Active	Active
96	New chamfer Sheet 3 (Rev B)	—	Active	Active
97	New surface treatment (Rev C)	—	—	Active

This becomes the canonical reference for what each balloon means across the production lifecycle. We documented the structure in How to Balloon a Drawing with Multiple Customer Revisions.

The Delta FAI Submission Package

A typical delta FAI submission includes:

1. Form 1 with configuration record showing the revision, ECN, effectivity, and previous FAI reference

2. Form 2 updates only for materials/processes that changed in the revision

3. Form 3 delta showing only the new or modified characteristics. The unchanged characteristics reference the previous FAI by balloon number.

4. Ballooned drawing for the new revision, with new balloons added and modified balloons noted

5. Change description documenting what changed and why a delta is appropriate

The customer reviewer looks at the delta and the previous full FAI together to verify the entire current state.

How Big Can a Delta Be?

The threshold is customer-specific. Common patterns:

• Boeing: typically accepts delta if <30% of characteristics changed

• Airbus: typically accepts delta if <25% of characteristics changed

• Lockheed: stricter, often requires full FAI for revisions affecting Critical features

• Smaller customers: varies widely

Above the threshold, a full FAI is required. The threshold is in the customer's supplier quality manual or in the contract. Confirm with the customer's quality team before submitting if you are near the threshold.

When Process Changes Trigger FAI (Not Just Drawing Changes)

Per AS9102 Rev C, process changes can trigger FAI:

• New machining vendor

• New heat treat vendor

• New plating vendor

• New welder qualification

• New CMM

• Significant operator change on a controlled operation

• New tooling that affects critical dimensions

These process changes may not affect the drawing but still require FAI documentation. The delta FAI in these cases focuses on the affected characteristics: the dimensions or features that the new process produces or measures.

Common Multi-Revision FAI Mistakes

Renumbering balloons across revisions. The cardinal sin. Once you renumber, every previous FAI becomes uninterpretable. The customer rejects the package.

Reusing deleted balloon numbers. Balloon 47 was deleted in Rev B; you reuse 47 for a new characteristic in Rev C. The lifecycle trace is broken.

Missing configuration record. Form 1 without specific revision, ECN, and effectivity. The reviewer cannot tell what this FAI applies to. Rejection.

No tracking matrix. Each FAI is created in isolation without cross-referencing previous revisions. Inevitably leads to renumbering or duplicates over time.

Delta when full is required. Customer required full FAI for the revision; supplier submitted a delta. Mismatch with customer expectations.

Full when delta is acceptable. Customer accepts delta for the revision; supplier submits a full FAI and spends 5x the time. Acceptable but wasteful.

The broader rejection patterns are in Common AS9102 Form 3 Rejection Reasons and First Article Inspection Failure Causes. When rejection happens, the workflow is AS9102 FAI Rejection Response and Corrective Action. And the pre-submission readiness check is in Aerospace FAI Pre-Submission Checklist for Quality Engineers.

The Long-Term Production Discipline

For parts that go through 5-10 revisions over a multi-year production run, the supplier with disciplined multi-revision tracking has lower FAI costs than one without it. The tracking matrix, balloon mapping table, and configuration discipline pay for themselves several times over by preventing rejection and rework.

A typical aerospace bracket might go through 6-8 revisions in its production life. Each delta FAI costs 8-16 hours when the tracking is clean and 40-80 hours when it is not. Over 6 revisions, that is a difference of 200-400 hours per part program.

Mavlon Manages Revisions in a Workspace

Mavlon maintains a workspace per part. When you upload a new revision, the system compares to the previous revision, preserves unchanged balloon numbers, assigns new numbers for new characteristics, marks deletions as obsolete (without reusing numbers), and outputs a delta FAI Form 3 ready for submission. The tracking matrix is built automatically.

Upload a Revision to see delta FAI automation.