This standard is primarily intended to apply to new parts and products, but can also be applied to parts currently in production. The standard shall be applicable to all production processes that influence the variation of KCs, as well as maintenance processes in which KCs are identified. It applies to assemblies and all levels of parts within an assembly, down to the basic materials including castings and forgings, and to organizations that are responsible for producing the design characteristics of the product. It does not apply to lab-scale, pilot, or pre-production processes. However, particular management of some KCs might be required using other methods than those described in the standard, during these phases of a programme, when required by the customer or deemed appropriate by the organization (e. g., Engineering department requirement). The variation control process begins with product definition, typically an engineering drawing or specification which identifies KCs, and leads to a variation management program for those KCs. This process may also be used for producer-identified KCs. Producers and their subcontractors shall be responsible for flow down of the requirements of the applicable revision of this standard to subcontractors, who produce design characteristics, and for ensuring that KCs conform to customer requirements. Purpose This standard is designed to drive the improvement of manufacturing and maintenance processes through adequate planning and effective management of KC variation. The KC focus is intended to improve confidence for part features whose variation has a significant influence on to end-product form, fit, performance, service life, and producibility. NOTE Control of a product or process KC per this standard does not constitute, nor imply, acceptance of the resulting product. If variation management, under this standard, is to be part of an acceptance decision, the requirements must be specified in the applicable product acceptance plan or contract. Convention The following conventions are used in this standard: The words "shall", "will", or "must" indicate mandatory requirements; The word "should" indicates a requirement with some flexibility allowed in compliance methodology; Producers choosing other methods to satisfy a "should" shall be able to show that their approach meets the intent of the requirements of this standard; Words "typical", "example", "for reference", "may", or "e. g." indicate suggestions given for guidance only; "NOTES" are used for additional clarification; Words or phrases with specific meaning pertaining to this document are defined in Clause 3, Terms and Definitions.