All but the most simple products contain very large numbers of features. In theory,
every feature of every unit produced could be inspected and judged against the require-
ments. However, this would add considerable cost to the product while, for most features,
adding little or no value to the customer. The producer is faced with the need for estab-
lishing a hierarchy of importance for the various characteristics of the product. Which fea-
tures are so important that they deserve a great deal of attention? Which need only a
moderate amount of attention? Which need only a cursory inspection? The activity of
arriving at this determination is known as classification of characteristics.
In practice, characteristics are usually classified into the categories critical, major, and
minor. The terms can be defined in simple terms as follows:
Critical characteristic—Any feature whose failure can reasonably be expected to pres-
ent a safety hazard either to the user of the productor to anyone depending on the
product functioning properly.
* Major characteristic—Any feature, other than critical, whose failure would likely result
in a reduction of the usability of the product.
* Minor characteristic—Any feature, other than major or critical, whose failure would
likely be noticeable to the user.
* Incidental characteristic—Any feature other than critical, major, or minor.
Of course, it is possible to develop classification schemes that are more detailed.
However, the above definitions suffice for the vast majority of applications. Most often
classifications of critical characteristics are noted on the drawing as well as in the manu-
facturing plan, as well as in such other ways as to give the user ample warning of poten-
tial hazards.
A classification of defects is the enumeration of possible defects of the unit of product
classified according to their seriousness.
The following definitions are:
* Defect—Any nonconformance of the unit of product with specified requirements.
* Defective—A product with one or more defects.
Critical defect—A critical defect is a defect that judgment and experience indicate
would result in hazardous or unsafe conditions for individuals using, maintaining,
or depending upon the product or a defect that judgment and experience indicate
is likely to prevent performance of the tactical function of a major end item such
as a ship, aircraft, tank, missile, or space vehicle.
* Critical defective—A critical defective is a unit of product which contains one or more
critical defects and may also contain major and/or minor defects.
* Major defect—A major defect is a defect, other than critical, that is likely to result in
failure or to reduce materially the usability of the unit of product for its intended
purpose.
* Major defective—A major defective is a unit of product which contains one or more
major defects and may also contain minor defects but contains no critical defects.
* Minor defect—A minor defect is a defect that is not likely to reduce materially the
usability of the unit of product for its intended purpose or is a departure from
established standards having little bearing on the effective use or operation of the
unit.
* Minor defective—A minor defective is a unit of product which contains one or more
minor defects but contains no critical or major defect.