Deviation

A deviation is a formally approved departure from a part's specified requirements, agreed upon by the customer or relevant authority, either before production (a planned deviation) or after a nonconformance is identified (a use-as-is or concession deviation). It differs from an unauthorized nonconformance in that it carries explicit approval to proceed despite not meeting the original specification.

Why formal approval, not just fitness for purpose, defines a deviation

A deviation avoids the cost of scrapping or reworking a part that's judged fit for purpose despite a technical nonconformance, but only when it's actually formally approved; using a part out of specification without that approval isn't a deviation, it's an unauthorized nonconformance.

Where deviations are documented

Not on the drawing; a deviation is a documented approval that departs from what the drawing specifies, recorded separately rather than changing the drawing itself.

Common mistakes

Treating an unapproved decision to use an out-of-spec part as a deviation; without formal approval from the customer or relevant authority, it remains an unauthorized nonconformance, regardless of whether the part seems functionally fine.

Is a deviation the same as a nonconformance?

A nonconformance is any departure from requirements; a deviation is specifically a formally approved departure, agreed upon rather than simply discovered.

Can a deviation be requested before production starts?

Yes, a planned deviation can be requested and approved in advance, when a known constraint makes meeting a requirement impractical.

What happens without formal approval for an out-of-spec part?

Using it without approval isn't a deviation; it remains an unauthorized nonconformance, regardless of whether the part is judged functionally acceptable.