Comparison
ECP vs ECR vs ECN in Technical Data
Definitions
Request, Proposal, Notice
An engineering change proposal (ECP) is the defense term. MIL-HDBK-61B, the Department of Defense's configuration management handbook, defines it as “a proposed engineering change to the product and its configuration documentation, by which the change is described, justified, and submitted to a Configuration Approval Authority for approval/disapproval or deferral.” The format is a DD Form 1692, and the contract data item description for the content is DI-SESS-80639.
An engineering change request (ECR) and an engineering change notice (ECN) are common industry terms, built into most product lifecycle management tools. Neither MIL-HDBK-61B nor the abstract of the SAE EIA-649C configuration management standard uses them, so they mean what a given company's change procedure says they mean. The usual pattern is the one in the table: a request opens the question, a change board decides, and a notice (some companies say order) releases the result. The three therefore sit at different points in one flow rather than competing for the same job.
Side by Side
How They Differ
| ECP | ECR | ECN | |
|---|---|---|---|
| Stands for | Engineering change proposal | Engineering change request | Engineering change notice |
| What it does | Describes and justifies a change to approved configuration documentation and submits it to the approval authority. | Asks for a change to be considered. Usually the first, lightweight step. | Tells everyone downstream that a change was approved and what it affects. |
| Where the term lives | U.S. defense acquisition. Defined in MIL-HDBK-61B; the format comes from a DD Form 1692 and a data item description. | Industry practice and PLM tooling. Not defined in the defense documents we read. | Industry practice and PLM tooling. Not defined in the defense documents we read. |
| Who writes it | Usually the contractor, though the Government can ask for one. | Anyone who sees a need: engineering, manufacturing, support, a customer. | The change administrator, after the change board approves. |
| Who decides | The Government for Class I; local Government review of the classification for Class II, unless the contract says otherwise. | A change board inside the company. | Already decided. It records the decision. |
| What the manuals team gets | The scope of the change, its justification, and an implementation plan, plus a notice of revision if one is required. | An early warning, nothing binding. | The released change, the documents it touches, and the effectivity. |
The ECR and ECN columns describe common practice, not a standard. Where a contract uses these words, the contract's own definition governs.
Defense Practice
Class I, Class II, and the Documents Around an ECP
Defense ECPs are classified. MIL-HDBK-61B defines a Class I (major) change as one that affects a physical or functional requirement in approved functional or allocated configuration documentation, or that affects approved documentation along with cost, warranties, or contract milestones. A Class II (minor) change is any ECP that is not Class I. A Class I ECP is approved by the Government's configuration control board and authorized with a contract modification. Unless the contract says otherwise, the local Government representative reviews a Class II change for concurrence in its classification. The handbook sends readers to the DD Form 1692 instruction sheet for the detailed criteria; use those, and your contract, rather than a summary.
Three companion documents come up often.
- Notice of revision (NOR). The handbook calls it an ancillary document to the ECP that conveys the specific change to a specific document. It is delivered under the contract statement of work and CDRL, the same route as other contract data (see what a CDRL is).
- Request for variance (RFV). This is the modern name for what older contracts call a request for deviation or waiver. The handbook footnotes that a variance requested during or after manufacture was formerly called a deviation or waiver, with the same processing rules. A variance departs from the baseline for specific units without revising the baseline; an ECP changes the baseline itself.
- Retrofit instruction. After an approved change, this tells the field how to bring delivered units up to the new configuration. The handbook notes it is sometimes called an alteration instruction, modification work order, technical directive, or time compliance technical order.
Who governs all this? MIL-STD-973, the old military configuration management standard, was cancelled in September 2000, and DoD turned to the industry standard EIA-649, now at revision C (February 2019). MIL-HDBK-61B, dated 7 April 2020, is guidance only and says it should not be cited as a requirement. A program's real requirements are whatever its contract imports. Nothing here is legal advice; read the contract text.
Technical Manuals
How an Approved Change Reaches the Manual
MIL-HDBK-61B lists validation of operation, maintenance, installation, or modification instructions among the ways to verify a change. Our read is that this is where a publications team is pulled in. The handbook does not tell a manual writer what to do; the sequence below is how the pieces usually connect.
- The change is approved. For a defense program that is an ECP approval, and an ECN or equivalent release in industry practice. The approved change carries an identifier, and the handbook says approved Class I and Class II changes released for production are identified by change identifiers.
- The source data changes. The drawings, models, and parts data move first. A technical data package is the authoritative description of the item (see what a TDP is), and a manual is written from it. Where the definition is a model, a change to the model reaches the manual as a source change (see model-based definition).
- The manual follows, in one of three ways. If the change touches procedures, parts, or figures in a way that fits the next scheduled update, it goes into a revision. If it cannot wait, it goes out as an interim change, the way temporary revisions work in aviation manuals. If the change is a modification to fielded units, a retrofit instruction carries the how-to (an Air Force time compliance technical order or an Army modification work order, for example), and the manuals are updated to describe the modified configuration.
- Effectivity says who is affected. A change is rarely fleet-wide on day one. Units that have the change and units that do not both exist, sometimes for years, and the manual has to serve both.
In commercial aviation the same chain starts with the manufacturer's design change and usually reaches operators as a service bulletin; see service bulletin currency and airworthiness directives vs service bulletins. The ECP is the defense acquisition front end of that pattern.
S1000D
Recording the Change in Structured Data
In an S1000D library, effectivity and change history are handled by two different mechanisms. Effectivity is applicability: content declares which units it applies to, using the product attributes, the conditions (typically whether a modification is embodied), and the product instances recorded in the cross-reference tables. Our applicability guide works through an example of a step that changes after a modification. The history of the change is separate: data modules carry change marking, and the front matter can list what changed (see our piece on revision control).
So one approved change usually becomes several small data module updates, each with its own applicability, rather than a new manual. That is the structural reason S1000D libraries absorb engineering change more cheaply than documents do. The standard itself is covered on the S1000D page.
FAQ
Questions We Hear
What is the difference between an ECP and an ECN?
An ECP proposes a change and asks for approval; an ECN announces a change that has been approved. ECP is the defense acquisition term: MIL-HDBK-61B defines it as a proposed engineering change, described, justified, and submitted to a configuration approval authority for approval, disapproval, or deferral. ECN is a common industry term for the notice that follows a decision. Neither the handbook nor the EIA-649C abstract defines ECN, so read how your own contract or change procedure uses it.
What is the difference between an ECR and an ECN?
An ECR asks for a change; an ECN reports that one was approved. In common industry practice the request opens the process, a change board decides, and the notice (or order, in companies that use that word) releases the change to production, purchasing, support, and publications. The names and the exact steps vary by company, and the defense configuration management guidance we read uses neither term.
What is a Class I versus a Class II ECP?
MIL-HDBK-61B defines a Class I (major) ECP as a change to approved configuration documentation that affects a physical or functional requirement in approved functional or allocated configuration documentation, or that affects approved documentation and cost, warranties, or contract milestones. A Class II (minor) ECP is any ECP that is not Class I. A Class I change is approved by the Government and authorized with a contract modification; a Class II change is typically reviewed by the local Government representative for concurrence in the classification, unless the contract says otherwise. The detailed criteria are in the DD Form 1692 instructions, so check them and your contract.
Is there a military standard for ECPs?
Not a current one. MIL-STD-973, the military configuration management standard, was cancelled in September 2000 and DoD moved to the industry standard EIA-649; the current revision is EIA-649C (February 2019). MIL-HDBK-61B (7 April 2020) gives guidance but says it is for guidance only and cannot be cited as a requirement. In practice a contract calls for ECPs through its statement of work and a CDRL, usually citing the ECP data item description (DI-SESS-80639) and the DD Form 1692.
How does an approved ECP change a technical manual?
It does not change the manual by itself. The approved change updates the configuration documentation and the product; the manual then has to follow. For fielded equipment the change usually reaches users through a retrofit instruction (MIL-HDBK-61B notes these are sometimes called a modification work order, technical directive, or time compliance technical order), and the manuals are revised or supplemented to match, with effectivity showing which units carry the change. Whether the manual change is a revision, a change package, or a bulletin is set by the manual's own change process and the contract.
What is a notice of revision?
A notice of revision (NOR) is the companion to an ECP. MIL-HDBK-61B calls it an ancillary document that conveys the specific change to a specific document, required when the specific changes to the affected documents must be spelled out. It is delivered under the contract statement of work and CDRL, and the ECP data item description says a NOR requirement should be imposed contractually alongside it.
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Manuals That Follow the Change
An approved engineering change is only finished when the manual matches the product. We build technical publications so the change reaches the page and the effectivity is right.