Detailed Guidance on Repair Documentation for Aerospace Maintenance Organizations

In aerospace maintenance and repair, documentation is as critical as the physical work performed. When a deburring operation is part of a major repair to a type-certificated aircraft, engine, propeller, or component, the work must be documented on FAA Form 337 (Major Repair and Alteration). This form serves as the official record that the repair was performed in accordance with approved data and that the article remains airworthy.

For maintenance organizations, understanding when deburring crosses the threshold from routine maintenance to major repair—and therefore requires Form 337 documentation—is essential for regulatory compliance. This detailed guidance explains the requirements, the decision process, and how to properly document deburring-related major repairs.

Important Note: This guide provides general regulatory information. Maintenance organizations should consult with their local Flight Standards District Office (FSDO) or a Designated Engineering Representative (DER) for specific compliance determinations. Longguang is a brush manufacturer, not a regulatory consultant.

1. Overview of FAA Form 337

What Is FAA Form 337?

FAA Form 337, "Major Repair and Alteration," is the official form used to document:

The form is required when performing major repairs or major alterations to FAA-certificated aircraft, engines, propellers, or components.

Why Form 337 Matters

Regulatory Basis

For cross hole deburring aerospace , understanding this regulatory framework is essential for compliance.

2. Major vs. Minor Repairs: The Critical Distinction

Appendix A to Part 43 – Major Repairs

Appendix A defines major repairs as those that:

Minor Repairs

A minor repair is any repair that does not meet the definition of a major repair.

The "Appreciably Affect" Standard

For hydraulic system parts processing , a burr left on a hydraulic component could appreciably affect reliability.

3. When Deburring Is a Major Repair

Deburring, by itself, is not automatically a major repair. However, deburring operations can constitute a major repair under several scenarios.

Scenario 1: Deburring as Part of a Welded Repair

Example: Repairing a cracked engine mount by welding. The deburring of the weld area is part of the major repair and must be documented on Form 337.

Scenario 2: Deburring a Crack or Damaged Area

Example: Stop-drilling a crack in an aircraft skin. The stop-drilled hole must be deburred. Both the drilling and deburring are part of the major repair.

Scenario 3: Deburring a Repaired Surface

Scenario 4: Deburring a Structural Component During Overhaul

Scenario 5: Deburring a Component Not Covered by Type Design

The Decision Tree

Is the deburring part of a repair operation?
│
├── NO (routine cleaning, pre-inspection deburring, finishing of new parts)
│   └── NOT a repair → No Form 337 required
│
└── YES
    │
    └── Is the underlying repair major or minor?
        │
        ├── Minor repair → No Form 337 required (document in maintenance records)
        │
        └── Major repair → Form 337 REQUIRED
            └── Deburring is part of the documented major repair

For cross hole deburring , a repair that requires cross hole deburring is likely a major repair if on a structural component.

4. The "Good Manufacturing Practice" Exception

What Is "Good Manufacturing Practice"?

In aerospace, "good manufacturing practice" (GMP) refers to standard, accepted practices for producing conforming parts. Deburring is generally considered GMP for machined components.

When GMP Does Not Apply to Deburring

For aerospace alloy parts processing , even "minor" deburring must be documented in maintenance records.

5. Deburring That Is NOT a Major Repair

Routine Maintenance Deburring

Documentation for Minor Deburring

Even when Form 337 is not required, deburring operations must be documented in the aircraft's maintenance records (typically logbook entries) .

For metal parts surface treatment , proper documentation of deburring is a regulatory requirement.

6. How to Properly Document Deburring on FAA Form 337

Form 337 Block-by-Block Guidance

Sample Block 6 Narrative (Deburring as Part of Weld Repair)

Block 6 – Description of Work Performed:

Repaired cracked engine mount (P/N 12345) per manufacturer's Structural Repair Manual (SRM) Chapter 51-20-01, Figure 2, Detail C.

1. Removed cracked material by machining.

2. Prepared weld area by grinding and deburred all edges.

3. Welded using TIG process per SRM specification.

4. Deburred weld bead and blended smooth.

5. Inspected for cracks using fluorescent penetrant (FPI) per ASTM E1417.

6. Deburred all surfaces to remove any sharp edges.

7. Finished to original dimensions.

8. Primed and painted per SRM requirements.

All work performed in accordance with approved data referenced in Block 8.

Sample Block 6 Narrative (Deburring Stop-Drilled Crack)

Block 6 – Description of Work Performed:

Repaired fatigue crack at station 123.5 on lower fuselage skin (P/N 67890) per approved data DCN 12345.

1. Stop-drilled crack ends with #40 drill.

2. Deburred stop-drilled holes with cross hole brush per SRM 51-10-01.

3. Installed approved crack stop patch per SRM Figure 4.

4. Sealed with MIL-S-8802 sealant.

5. Deburred all fastener holes and patch edges.

6. Inspected per SRM requirements.

All work performed in accordance with approved data referenced in Block 8.

For cross hole deburring aerospace , the specific deburring method (e.g., cross hole brush) should be documented.

7. Approved Data for Deburring-Related Major Repairs

What Is "Approved Data"?

Approved data is technical information approved by the FAA or an authorized designee for use in performing a major repair or alteration .

When Deburring Is Not Explicitly Covered

Advisory Circular AC 43-210A

AC 43-210A provides guidance on approved data for major repairs and alterations . For deburring, it references:

For hydraulic system parts processing , AC 43-210A is the primary guidance for repair documentation.

8. Documentation Requirements for Outsourced Deburring

When Deburring Is Outsourced

Many maintenance organizations outsource deburring to specialized shops. This does not change the documentation requirements.

Supplier Requirements

Sample Supplier Documentation

For automotive manufacturing brushes , automotive requirements are less stringent, but aerospace requires full traceability.

9. Common Mistakes and Audit Findings

Mistake 1: No Documentation for Deburring That Is Part of Major Repair

Solution: Always include deburring in the Block 6 narrative when deburring is part of a major repair.

Mistake 2: Using Unapproved Deburring Methods on Major Repairs

Solution: Use FOD-safe brushes (cross hole brushes, ceramic fiber brushes) and follow approved data.

Mistake 3: No Traceability of Deburring Tools

Solution: Implement brush logs and tool control (shadow boards).

Mistake 4: Deburring a Part Beyond Allowable Limits

Solution: Follow limits specified in approved data; use controlled parameters.

For FOD prevention , tool control is essential for audit compliance.

10. Best Practices for Deburring Documentation

Pre-Work Documentation

During-Work Documentation

Post-Work Documentation

Documentation Retention

For metal precision machining , documentation retention is critical for audit readiness.

11. Longguang's FOD-Safe Brushes for Repair Operations

Why Longguang Supports Regulatory Compliance

For more information, please visit:

• Cross Hole Brush

• Ceramic Fiber Disc Brush

• Why Choose Longguang

12. Conclusion

FAA Form 337 is required when deburring is part of a major repair—a repair that might appreciably affect the strength, structure, reliability, or operation of an aircraft, engine, propeller, or component.

Key Takeaways for Maintenance Organizations

The Bottom Line

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