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Downloaded from http://www.everyspec.com on 2011-10-29T14:56:01.DOD-HDBK-791(AM)assume the following data for this example:The probability P NORSof not operational ready, supply, isgiven by (Ref. 7)By referring to a Normal Probability Table withZn = 0.55. the probability that demand exceeds supply is29%.Now. assume that both the supply and demand double,and for the sake of simplicity, also assume that the standarderrors double. Then Zn, becomesBy use of Eq. 3-5 and the given data. the (P NORS), areFrom the data it is obvious that the use of standardengines improves operational readiness.Example 3-4:In the small arms commodity area, much of the NATOweaponry has been standardized at 7.62 mm (for personnel,combat vehicles, and aircraft). This type of standardizationincreases the availability of small arms ammunition.Since the number of small arms rounds expended isextremely large, a normal distribution can be assumedand used to evaluate the benefits of a standard ammunitionsize. Assume that the supply of 7.62-mm ammunitionaveraged 100,000 rounds per day with a 30,000-roundstandard error and demand averaged 80,000 rounds perday with a 20,000-round standard error. A standard normaltest statistic Z ncan be determined by (Ref. 10)and the probability that demand exceeds supply isreduced to 22%. This illustrates how a large inventory ofcommon items will reduce the probability supply willexceed demand.3-6 SOURCES OF INFORMATIONThe reluctance exhibited by the designer to use existingparts and standard items is not the result of indifference tothe program; rather, it can be attributed to ignoranceabout the sources of information. Consequently, variousinformation sources that support standardization andinterchangeability are discussed, i.e..I. DoD Instruction 4120.19, Department of DefenseParts Control Program2. A R 700-60. Department of Defense Parts ControlProgram3. MIL-STD-965. Parts Control Program4. MIL-STD-143, Standards and specifications,Order of Precedence for the Selection of5. Department of Defense Index of Specificationsand Standards (DODISS)6. Qualified Products List7. Army Master Data File8. Identification List9. National Stock Number10. Test, Measurement, and Diagnastic Equipment(TMDE).Each of these information sources is discussed in theparagraphs that follow.3-6
Downloaded from http://www.everyspec.com on 2011-10-29T14:56:01.DOD-HDBK-791(AM)3-6.1 DoD INSTRUCTION NO. 4120.19,DEPARTMENT OF DEFENSE PARTSCONTROL PROGRAMThis instruction assigns “responsibility for implementingthe DOD Parts Control Program as an integral part ofthe acquisition process for the support of systems, subsystems,and equipment by the DOD” (Ref. 2).The objective of this instruction is to “conserve resourcesand to reduce life cycle cost by reducing thevarieties of component parts; promoting the applicationof established or multiuse items of known performanceduring the design, development, production or modificationof equipments and weapon systems; and applyingtechniques to assist system or equipment acquisitionmanagers and their contractors in the identification andselection of established or multi use parts to enhance interorintradepartmental system commonality, interchangeability,reliability, maintainability, standardizatition, andinteroperability” (Ref. 2)3-6.2 AR 700-60, DEPARTMENT OFDEFENSE PARTS CONTROLPROGRAMThis Army regulation provides for the implementationof DoD Instruction No. 4120.19 and sets forth the Armypolicy and establishes responsibilities for Army participationin the mandatory DoD Parts Control Program(PCP) and for the use of advisory support services ofMilitary Parts Control Advisory Groups (MPCAGs)(Ref. 1l).The function of the MPCAGs is “to provide ArmyElements and their assigned contractors engineeringadvice and recommendations for assigned Federal SupplyClasses (FSC) on the selection and use of parts during thedesign, development, production, and modification ofsystems, subsystems, and equipment. Decision authorityfor the selection and use of parts rests with the Armyelements responsible for the acquisition and support ofthe system, subsystem, or equipment” (Ref. 11).3-6.3 MIL-STD-965, PARTS CONTROLPROGRAMSince this is the first time the term “MilitaryStandard” has been introduced, it may be expedient todefine the term to distinguish it from “Military Specification”.A military standard is a document that establishesengineering and technical requirements for items, equipments,processes, procedures, practices, and methods thathave been adopted as standard. Standards may alsoestablish requirements for selection, application anddesign criteria for materiel (Ref. 12). In contrast, a militaryspecification for the same item describes it in termsof the requirement for procurement.MIL-STD-965 (Ref. 13) establishes guidelines andrequirements for the implementation of a parts controlprogram, and it is applicable to both new designs ormodifications. The standard emphasizes that the contractormust develop a proposed Program Parts SelectionList (PPSL) in which the number of different part types isminimized and the use of standard parts is maximized.When standard parts cannot be selected, nonstandardparts are to be selected from documents in accordancewith the order of precedence of MIL-STD-143 (Ref. 14).An example of the selection process is shown in Fig. 3-2.MIL-STD-965 (Ref. 13) describes the function of the1. Parts Control Board (PCB), a formal organizationestablished by the contract to assist the prime contractorin controlling the selection and documentation ofparts used in equipment, systems, or subsystems.2. Military Parts Control Advisory Group (MPCAG),a DoD organization that provides advice to the militarydepartments and military contractors on the selection ofFigure 3-2. Example for Selection of Parts for Program Parts Selection List (PPSL) (Ref. 13)3-7
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