In aerospace and other regulated industries, the terms scrap, rework, repair, and concession describe distinct ways of handling nonconforming product. They are not interchangeable, and each has different implications for airworthiness, approvals, documentation, and cost reporting.
Scrap
Scrap is product or material that cannot or will not be used as part of a delivered configuration. Typically:
- It does not meet requirements and cannot be brought back into conformity in a technically and economically justified way, or
- It could be reworked or repaired, but the organization decides not to, based on cost, risk, schedule, or customer requirements.
Key characteristics:
- Removed permanently from the production flow and from any airworthy configuration.
- Physically rendered unusable or clearly segregated, then disposed of following internal and regulatory controls.
- Recorded as nonconformance and as scrap in cost-of-poor-quality metrics.
- Usually does not go through design approval, because it will not fly or enter service.
In brownfield environments, scrap tracking is often fragmented across paper travelers, ERP scrap codes, and local spreadsheets, which can distort actual scrap cost if not aligned.
Rework
Rework means processing a nonconforming item so that it fully meets the original, released design definition and specifications.
Key characteristics:
- The end state is indistinguishable from product that never had a nonconformance when compared to the approved design and specification.
- Uses the same or equivalent processes already approved by design (e.g., re-machining within allowed stock, repeating an approved heat treatment, re-assembling to the same drawing).
- Usually handled through standard nonconformance control, with rework instructions documented, controlled, and traceable (e.g., in an NCR, MRB record, or MES nonconformance workflow).
- Does not require a design deviation, because the final configuration equals the baseline design.
If you must introduce a new process, change a critical dimension tolerance, or alter material properties beyond existing allowances, you have likely moved from rework into repair or design change territory.
Repair
Repair means processing a nonconforming item so that it is acceptable for use, but does not fully conform to the original design definition. Instead, it conforms to an approved repair disposition or repair scheme.
Key characteristics:
- Final condition is safe and acceptable, but not identical to the original design (for example, material is blended out of a noncritical area, or a bushing is installed as a permanent corrective feature).
- Requires formal engineering disposition (e.g., MRB engineering, design authority approval, or use of an approved structural repair manual or standard repair scheme).
- May require stress analysis, fatigue assessment, or other justification, especially in aerospace primary structure or critical systems.
- Often creates a “repaired” configuration that must be traceable on the as-built record, including any limitations, inspections, or life restrictions.
In regulated aerospace, repair dispositions usually need higher-level engineering and, in some cases, regulatory or delegated authority approval. The level of rigor depends on part criticality and applicable regulations or customer contracts.
Concession (Deviation/Waiver)
A concession is formal permission from the design or customer authority to accept, ship, or operate an item that does not meet specified requirements, under defined conditions. In some organizations or standards this may be called a deviation or waiver, and the detailed definitions can differ.
Key characteristics:
- The product remains nonconforming to the original specification on at least one point.
- The nonconformance is acknowledged, risk-assessed, and accepted by the responsible design or customer authority for a limited scope (specific parts, serials, or time period).
- Conditions and restrictions may apply (e.g., inspection intervals, limited life, configuration markings, or operational limits).
- Requires strong traceability, because regulators and customers often review concessions closely during audits and investigations.
Concessions are typically used when the cost, schedule impact, or technical risk of rework/repair is high, but engineering analysis shows the deviation does not compromise fitness for intended use or safety margins.
How they relate and why the distinctions matter
The four dispositions are related but not interchangeable:
- Scrap vs rework/repair: Scrap removes the item from service permanently. Rework and repair return the item to use.
- Rework vs repair: Rework restores full compliance with the original design; repair restores acceptable performance under a modified, approved condition.
- Repair vs concession: Repair changes the hardware or processing. A concession formally accepts a deviation that may remain as-is, with or without physical change.
These distinctions affect:
- Regulatory expectations: Authorities and customers expect documented processes for each disposition, especially repair and concession, and may require specific approvals or delegated signatories.
- Traceability and records: Repaired and conceded items need clear traceability in the as-built record, often across multiple systems (ERP, MES, QMS, PLM). In brownfield stacks, this usually involves workarounds and interfaces rather than a single clean workflow.
- Cost of poor quality (COPQ): Mislabeling rework as repair or repair as scrap distorts data on systemic issues and investment decisions.
- Lifecycle impact: Repairs and concessions can carry inspection or life limits. Losing that link when systems change or are upgraded is a common long-term risk.
Dependencies and plant-to-plant variation
The precise boundaries between rework, repair, and concession can vary based on:
- Contractual definitions with OEMs or primes.
- National or regional regulations and the way your design approval or delegated authority is structured.
- Internal procedures in your QMS, including how MRB authority is defined.
- The maturity and integration level of your MES/ERP/PLM/QMS stack.
When updating processes or systems, it is important not to “simplify” these categories into a single nonconformance bucket. In long-lifecycle aerospace programs, losing these distinctions can create major issues years later during incidents, retrofit campaigns, or design changes.
