Purpose

• To define interchangeability and the resulting actions required.

Applicability

• All changes to be processed by this CM function.

Policy/Practice

• Interchangeable – Two or more items are considered interchangeable if, in all applications, they are:
  1. Of an acceptable form (appearance) to fulfill all esthetic requirements per the product specifications.
  2. Of a proper fit (physical) to assemble with other mating items per the drawing dimensions and tolerances.
  3. Of a proper function to meet product specifications, including performance, safety and reliability requirements.
• Items meeting these criteria are completely interchangeable one for the other (both ways) with no special adjustments, modifications, or alterations to the item or related items.
• Items that meet some but not all of the above criteria are not completely interchangeable and are therefore considered non-interchangeable.
• Compatible is defined to mean that the old is not interchangeable in the new but the new is interchangeable in the old.
• Whether part numbers or revision levels change is determined by use of the Part Number & Rev Changes Logic Diagram (see Part Number & Revision Level Changes Standard).
• Non-interchangeable changes do not always require scrapping or reworking – disposition of old design parts is a separable decision (see Disposition of Old Design Parts Standard).
• Only those non-interchangeable changes designated to “retrofit” will be installed into returned goods or field units. “Update everything to the latest revision level” is very expensive and will not be done.
• If the product specifications are not clear when processing a change, they should be revised to clarify the interchangeability. If the product specifications are to be revised, it should be in the same change that raised the issue. If the cognizant engineer chooses not to revise the specification to clarify the issue, that change must be considered interchangeable.

Procedure

• None required.

Primary Responsibility

• The CM manager is responsible for keeping this standard current.

Authorization