Aerospace Supplier 8D — AS9100 Compliant Corrective Action Guide

Aerospace 8D Overview

Aerospace suppliers face some of the most stringent quality requirements in manufacturing. AS9100 (the aerospace extension of ISO 9001) and AS13100 (AESQ Supplier Quality Requirements) mandate structured problem-solving with specific aerospace-only requirements beyond IATF 16949.

This guide maps the standard 8D methodology to aerospace-specific requirements including First Article Inspection (AS9102), escape factor analysis, and airworthiness authority notification.

AS9100 Clause Mapping to 8D

Aerospace-Specific Requirements Beyond Automotive

1. First Article Inspection (AS9102)

After any corrective action that changes the manufacturing process, a delta FAI (or full FAI) must be performed per AS9102. The FAI verifies that the corrected process produces conforming parts. This goes beyond automotive PPAP — aerospace FAI requires 100% dimensional verification of all characteristics on the drawing.

2. Escape Factor Analysis

Aerospace 8Ds must include an escape factor analysis: not just what caused the defect (root cause), but how the defect escaped detection at every inspection point between creation and customer delivery. This typically identifies 2-4 inspection gaps that need closure.

3. Airworthiness Authority Notification

If the nonconformity affects an article with an 8130-3 or EASA Form 1 airworthiness certificate, the relevant civil aviation authority (FAA, EASA) must be notified within 72 hours via the Continued Airworthiness notification system. This has no equivalent in automotive.

4. Sub-Tier Flow Down

Aerospace primes require corrective actions to be flowed down to sub-tier suppliers. If your supplier caused the defect, your 8D must include their 8D response. If their supplier caused it, that must cascade. This creates a 3-tier investigation chain.

5. Extended Verification Period

Aerospace corrective actions typically require 90-180 days of verification data (vs. 30 days in automotive). 30 consecutive conforming parts minimum, with statistical capability demonstration (Cpk ≥ 1.33 for key characteristics).

5-Why Example: Aerospace Fastener Failure

**Problem**: Titanium Hi-Lok fastener fractured during installation on wing spar assembly. Torque-to-yield reached before clamp-up. 2 fasteners out of 200 in Lot #T-2026-001.

1. Why fracture? → Fastener body fractured at thread root — overload failure, not fatigue

2. Why overload? → Installation torque reached yield before achieving required clamp load

3. Why premature yield? → Fastener thread minor diameter measured 0.1875 inch (spec 0.1900 ±0.0015) — undersize by 0.0025 inch reducing cross-sectional area by 3%

4. Why undersize thread? → Thread rolling die worn beyond tolerance — die replaced at 50,000 cycle count (spec: inspect at 40,000)

5. Why die not inspected at 40,000? → Production scheduler overrode PM trigger to meet delivery commitment — die inspection deferred to next scheduled PM window

**TRC**: Fastener thread undersize from worn rolling die causing reduced tensile area

**MRC**: PM override process allowed production schedule pressure to defer critical quality inspection

**Escape Factor**: Incoming inspection performed thread major diameter check but not minor diameter. Thread minor diameter was not on the receiving inspection plan

FAA/EASA Notification Determination

This fastener was installed on a primary structure component (wing spar). An 8130-3 tag was issued. Since the nonconformity could affect structural integrity:

FAA Continued Airworthiness notification within 72 hours: **REQUIRED**

Affected aircraft serial numbers: 6 aircraft identified by lot traceability

Airworthiness directive potential: Engineering evaluation determined existing design margin absorbed the 3% area reduction — no unsafe condition. No AD issued.

D3 Containment

Quarantine all 198 remaining fasteners from Lot #T-2026-001 in warehouse, production, and at OEM receiving

100% thread minor diameter inspection on all fasteners in stock

Replace rolling die immediately

Notify customer quality and FAA within 72 hours

Boeing/Airbus specific: file quality escape in supplier portal

D5 Permanent Corrective Action

1. **Thread Rolling PM**: Reduce die inspection interval from 40,000 to 30,000 cycles. Die replacement mandatory at 45,000 cycles regardless of inspection result

2. **PM Override Prevention**: Production schedule cannot override PM triggers without Quality Director sign-off — enforced via MES system lock

3. **Incoming Inspection**: Add thread minor diameter (go/no-go gauge + optical comparator) to receiving inspection plan for all threaded fasteners

4. **SPC**: Implement X-bar R chart for thread minor diameter with ±0.001 inch control limits

D7 Prevention

Update PFMEA: increase Occurrence rating for thread die wear from 3 to 5

Deploy PM override lock to all 14 CNC thread rolling machines in the facility

Audit all 200+ receiving inspection plans for completeness against drawing requirements

Share lessons learned with 3 other aerospace fastener production sites in the company

Supplier quality: require sub-tier die suppliers to provide die wear rate data with each shipment

Key Takeaways

1. Aerospace 8Ds require both internal root cause AND supplier root cause (sub-tier flow down)

2. FAA notification timeline is absolute — 72 hours is a hard deadline

3. Escape factor analysis often finds inspection plan gaps — thread minor diameter is commonly missed

4. FAI delta after corrective action is mandatory for aerospace, not optional

5. PM override control is a management root cause that appears in ~40% of aerospace 8Ds

6. Production pressure overriding quality is the #1 MRC in aerospace manufacturing — fix the system, not the operator