What criteria should drive a scrap decision for aerospace structural parts?

A scrap decision for aerospace structural parts should be driven first by approved technical requirements and objective evidence, not by part value, schedule pressure, or whether the defect “looks minor.” In practice, the core question is simple: can the part still be shown, with traceable records, to conform to drawing, material, process, and customer or program requirements after any permitted rework or repair? If the answer is no, or cannot be demonstrated credibly, scrap is usually the right decision.

What should drive the decision

The decision normally starts with product definition and disposition authority, not shop-floor opinion. For structural parts, the most important criteria are these:

• Type and severity of nonconformance: dimensional out-of-tolerance, wrong material, heat-treat issue, surface damage, blend-out condition, hole quality problem, coating issue, process excursion, or traceability gap do not carry the same risk.
• Location and structural criticality: the same defect may be acceptable in a non-critical area and unacceptable in a high-stress, fatigue-critical, bearing, sealing, or mating feature.
• Engineering allowables and drawing requirements: if approved limits, repair schemes, or rework paths exist, they govern. If they do not, the part is not automatically recoverable.
• Material and process pedigree: unknown or broken traceability, suspect lot control, or missing process records can force scrap even when the geometry appears recoverable.
• Effect of rework or repair: additional machining, blending, sleeving, bushing, cold work, weld repair, or other recovery steps may consume life margin, alter fit, or trigger requalification requirements.
• Inspection evidence quality: the decision depends on reliable measurement, calibrated equipment, valid methods, and a clear understanding of actual versus suspected defect extent.
• Contractual and customer constraints: some programs restrict repair methods, concession use, or repeated rework more tightly than internal practice would suggest.
• Disposition authority: MRB, engineering, quality, and sometimes customer approval are required depending on the condition and the contract. Operators and supervisors should not be making final structural accept/scrap calls informally.

What should not drive it

Cost matters, but it is not the primary criterion. A high-cost part is not more repairable just because it is expensive to replace. Likewise, delivery pressure is not a technical basis for use-as-is, repair, or rework. In regulated aerospace environments, forcing borderline parts through because capacity is tight usually creates a larger problem later in audit trail review, customer escape analysis, or service risk assessment.

When scrap is often the right answer

Scrap is commonly the right outcome when one of these is true:

• The nonconformance violates a requirement with no approved rework or repair path.
• The defect affects a critical feature and engineering cannot justify residual strength, fatigue performance, fit, or function.
• Required traceability is missing or compromised for material, processing, or serialized identity.
• The proposed recovery would push the part outside other limits, including minimum wall, edge distance, coating thickness, residual stress expectations, or dimensional stack-up.
• The process excursion is broad enough that the true impact cannot be bounded credibly.
• The record set needed to support acceptance, concession, or repair cannot be completed with confidence.

Where MRB and engineering matter

For aerospace structural hardware, scrap decisions are usually part of a formal nonconformance process. MRB may coordinate the disposition, but engineering rationale is often decisive where structural performance is affected. The exact split of authority depends on company procedures, delegated authority, customer flowdowns, and part criticality.

This is where many plants get into trouble. They treat scrap as a production loss decision when it is really a controlled disposition decision. If the nonconformance workflow in MES, QMS, and ERP is weak, teams may argue from incomplete data, outdated drawings, or disconnected inspection records. In brownfield environments, that failure mode is common.

Data and system dependencies

A good scrap decision depends on having the right records linked together:

• Current drawing and revision from PLM or document control
• Traveler or routing history from MES or paper traveler records
• Material certs, lot genealogy, and serialized traceability
• Special process records
• Inspection results, including CMM or manual measurement evidence
• Prior rework, prior NCRs, or repeated escapes on the same feature
• Customer-specific disposition restrictions where applicable

If those records are fragmented across MES, ERP, QMS, and shared drives, the practical risk is not just delay. It is an incorrect disposition based on partial evidence. Full system replacement is usually not the answer here. In regulated aerospace environments, replacing core execution and quality systems wholesale often fails because of validation cost, qualification burden, downtime risk, and integration complexity. More often, plants improve the decision process by tightening record linkage, authority rules, and evidence capture across existing systems.

A practical decision frame

A defensible scrap decision for a structural part usually asks these questions in order:

1. What exact requirement was violated?
2. Is the feature structurally or functionally critical in this location?
3. Is there an approved rework or repair path for this condition?
4. Will that recovery path preserve all other requirements and margins?
5. Do we have complete, trustworthy evidence and traceability to support the disposition?
6. Do the required authorities agree and document the rationale?

If any of those answers is unclear, the part should stay in formal nonconformance control until clarified. In many cases, that uncertainty ends in scrap, and that is sometimes the least risky outcome.

Bottom line

The right criteria are technical conformity, structural intent, traceability, and approved disposition authority. Scrap should be decided by whether the part can still be demonstrated to meet requirements after an allowed recovery path, not by replacement cost or urgency. Where evidence is weak, traceability is broken, or structural margin cannot be justified, scrap is usually the defensible decision.