An engineering change order (ECO) is a formal document used in manufacturing and product development to propose, approve, and implement a change to a product’s design, components, or processes. It serves as the official authorization that a change should be made, creating a controlled, documented path from identifying a problem to verifying the fix. Whether a company needs to swap out a part because of a supply chain disruption, fix a quality issue, or comply with new regulations, the ECO is the mechanism that keeps everyone aligned on what’s changing, why, and when.
How an ECO Fits Into Change Management
An ECO doesn’t exist in isolation. It’s one stage in a broader change management process that typically involves three related documents, each serving a different purpose.
The engineering change request (ECR) comes first. This is where someone formally describes a proposed change and makes the case for it. The ECR lays out the risks, benefits, and technical feasibility of the change. Think of it as the pitch: here’s what’s wrong, here’s how we could fix it, and here’s why it’s worth doing.
If the ECR is approved, the engineering change order (ECO) is created. This is the actionable document. It contains the detailed design changes, the affected parts and drawings, cost implications, and the approvals needed to move forward. The ECO is the green light.
After the change is implemented, an engineering change notice (ECN) communicates the completed change to everyone who needs to know: manufacturing teams, suppliers, quality assurance, procurement. It’s the formal announcement that the product or process has been updated.
Not every organization uses all three documents. Some combine the ECR and ECO into a single step, especially for smaller changes. But the underlying logic is always the same: request, authorize, notify.
What Triggers an ECO
ECOs get created for a wide range of reasons. The most common include:
- Design errors or quality issues: A part doesn’t perform as expected in testing or in the field, and the design needs to be corrected.
- Supply chain disruptions: A component becomes unavailable or a supplier goes out of business, requiring a substitute part.
- Regulatory changes: New safety standards or environmental regulations demand modifications to materials or design.
- Cost reduction: Engineering finds a cheaper material or simpler manufacturing process that achieves the same result.
- Customer feedback: Users report problems or request features that require changes to the existing design.
In practice, most ECOs arise from problems discovered after initial design is complete, sometimes well into production. The formal process exists precisely because making changes at that stage is risky, touching parts, drawings, tooling, supplier contracts, and assembly instructions all at once.
What an ECO Typically Contains
A well-structured ECO captures everything someone would need to understand the change and carry it out. While formats vary by industry, the core information is consistent:
- Unique identifier: A tracking number assigned to the change order so it can be referenced throughout the organization.
- Affected parts and drawings: Specific part numbers, drawing numbers, and revision levels that the change applies to.
- Description of the change: A clear explanation of what is being modified and how the new design differs from the current one.
- Reason for the change: The justification, whether it’s a design correction, regulatory requirement, cost improvement, or something else.
- Impact assessment: How the change affects related assemblies, manufacturing processes, existing inventory, and spare parts. This often includes a disposition for existing stock: use as-is, rework, scrap, or replace.
- Approval signatures: Sign-offs from the relevant stakeholders, which might include the project engineer, materials engineer, quality team, cost accounting, and management.
In highly regulated industries like aerospace and medical devices, the documentation requirements expand significantly. An Air Force engineering order form, for example, includes fields for corrosion control review, system safety sign-off, critical safety item designation, and distribution statements. Medical device manufacturers tie their ECOs directly to regulatory compliance records. The principle is the same everywhere, but the level of rigor scales with the consequences of getting it wrong.
The Approval and Implementation Process
The ECO process follows a predictable sequence, though the speed and complexity vary based on the scope of the change.
It starts when the problem is clearly identified and reproduced, and a candidate solution has been proposed. Engineers then develop a detailed design to resolve the issue. That solution gets simulated or tested for effectiveness, then reviewed by the project manager (often with input from other engineering departments) and by accounting, which evaluates the cost implications. If approval isn’t granted, an alternative design has to be developed, and the cycle repeats.
Once implementation is authorized, the purchasing department coordinates with suppliers to incorporate the change into the next batch of parts. When those updated parts arrive, the new design is evaluated in context. Sometimes, the changed part proves ineffective, particularly if the broader system design has evolved during the time it took to process the ECO. In that case, a new ECO has to be generated, starting another cycle.
These iteration loops are one reason ECOs can take weeks or even months to close. Each loop means additional design work, simulation, review, and supplier coordination. Organizations that process high volumes of ECOs often find that congestion itself becomes a bottleneck, as change review boards get overloaded and approvals stack up in a queue.
Manual Tracking vs. PLM Software
Smaller companies sometimes manage ECOs with spreadsheets, email chains, and paper forms. This works when change volume is low, but it breaks down quickly as products grow more complex or teams become distributed. Manual handovers between departments cause delays, version control becomes unreliable, and it’s easy to lose track of which changes have been approved versus which are still pending.
Product lifecycle management (PLM) software addresses these problems by automating the entire workflow. A PLM system routes tasks to the right people automatically, tracks approval status in real time, and maintains a complete audit trail of every change. When an ECO is resolved, updated information can be published automatically to downstream systems like manufacturing execution or enterprise resource planning platforms, so everyone works from the same current data.
PLM tools also support different levels of process rigor within the same system. A minor drawing correction might follow a “fast track” path with a single administrator approval, while a major design change goes through a full change review board. This flexibility helps teams avoid applying heavyweight processes to lightweight changes, which is one of the most common sources of frustration in change management.
Why ECOs Matter Beyond Engineering
It’s tempting to think of ECOs as purely an engineering concern, but they ripple across the entire business. A part change affects procurement contracts, warehouse inventory, assembly line tooling, service manuals, and spare parts catalogs. Without a controlled process, a well-intentioned design improvement can create mismatched parts on the shop floor, obsolete inventory that no one knew to flag, or field service technicians working from outdated instructions.
The cost of an uncontrolled change also escalates dramatically depending on when it happens. A change caught during early design might cost almost nothing. The same change discovered after production tooling is complete, parts are in stock, and products are in customers’ hands can cost orders of magnitude more. The ECO process exists to make sure changes are deliberate, visible, and coordinated across every function they touch.