Deviation

Overview

A deviation is a decision, made in advance and on the record, to allow something to differ from what a requirement, rule or process says. It is not a mistake found afterwards; it is a known difference that has been assessed and accepted by someone with the authority to accept it. Deviations are used in platforms, quality systems, safety work and manufacturing.

How it works

A team that needs to depart from a rule raises a deviation request. The request states which rule is affected, what will be done instead, why, for which products, lots or period, and what the risk is. Reviewers check whether the departure is acceptable and whether conditions are needed, such as extra tests or a time limit.

If approved, the deviation is recorded, given an identifier and linked to the products or work it covers. It is checked at later reviews and audits, and closed when it ends or when the rule is changed to make it unnecessary.

On a platform, a derivative that needs to differ from the platform's rules, for example by using a different interface block, raises a deviation. The platform team decides whether to allow it, and whether the difference should become a new option in the platform.

Examples

• A derivative allowed to use a different memory controller from the platform's standard one, with extra integration tests.
• A temporary deviation allowing a production lot to ship with a documented cosmetic difference.
• A safety project deviation from a coding rule, justified and reviewed by the safety manager.
• A deviation closed when the platform adds the requested option.

Why it matters

Rules exist for good reasons, but real projects sometimes need exceptions. Recording them as deviations keeps exceptions visible, limited and owned, rather than hidden. Platform architects, quality engineers, safety managers and programme managers raise and approve them.

In the platform lifecycle, deviations are raised during derivative definition and design, checked at platform conformance reviews, and used to decide what the next platform version should support.

It matters most to: Configuration Management Engineer, Platform Architect, Platform & Derivative Program Manager, Quality Systems Engineer

Common confusions

Not the same as a non-conformance

A non-conformance is a failure to meet a requirement found after the fact. A deviation is permission given before the work, for a known difference.

Not the same as a change

A change alters the rule or the design for everyone from then on. A deviation leaves the rule as it is and allows one stated exception.

Sources

1. NPR 7120.5F Appendix A: Definitions (opens in a new tab), NASA, 2026-11-10
2. Deviation permit (ERA railway terminology collection, after ISO 9000:2015) (opens in a new tab), European Union Agency for Railways, 2026-11-10
3. EIA649C Configuration Management Standard (opens in a new tab), SAE International, 2026-11-10

Related terms

• Configuration management
• Conformance test suite

Where it appears on the Hub

Used on 14 pages of the Hub. In each group, the pages that mention it most come first.