MAINTAINABILITY DESIGN TECHNIQUES METRIC - AcqNotes.com

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Downloaded from http://www.everyspec.com on 2011-10-29T14:56:01.DOD-HDBK-791(AM)ST =TCM =TPM =TALDT =A o=standby time (not operating, butassumed operable) during a givencalendar time periodtotal corrective (unscheduled) maintenancedowntime during a givencalendar time periodtotal preventive (scheduled) maintenancedowntime during a given calendartime periodtotal administrative and logistic downtimespent waiting for parts, maintenancepersonnel, or transportationduring a given calendar time periodoperational availability.BBest operating capability (BOC). The upper level maintainabilityvalue estimated to be technically feasiblewithin the stated time frame and within reasonable costconstraints.Built-in test (BIT). An integral capability of the missionequipment that provides an on-board, automated testcapability to detect, diagnose, or isolate system failures.The fault detection and, possibly, isolation capabilityare used for periodic or continuous monitoring of theoperating condition of a system, and for observationand diagnosis as a prelude to maintenance. BITE maybe automatically or manually triggered.Built-in test equipment (BITE). Any device which is partof an equipment or system and is used for the expresspurpose of testing the equipment or system. It is anidentifiable unit of the equipment or system. BITE maybe automatically or manually triggered.CCalendar time. The total number of calendar days orhours in a designated period of observation.Calibration. Those measurement services provided bydesignated depot and/or laboratory facility teams, whoby the comparison of two instruments one Of which isa certified standard of known accuracy detect andadjust any discrepancy in the accuracy of the instrumentbeing compared with the certified standard.Cannibalization. The removal of serviceable items from apiece of equipment to repair another.Capability. A measure of the ability of an item to achievemission objectives given that the item performs as specifiedthroughout the mission.Catastrophic failure. A sudden change in the operatingcharacteristics of some part or parameter resulting in acomplete failure of the item, e.g., circuit opens orshorts, structural failure. etc.Chargeable. Within the responsibility of a given organizationalentity (such as Failures, Maintenance time. etc.)Checkout. A man machine task to determine that theequipment is operating satisfactorily and is ready forreturn to service.Checkout time. The time required to check out theequipment after a maintenance action or otherwise toverify that a system or equipment is in satisfactoryoperating condition.Circuit malfunction analysis. The logical, systematicexamination of circuits and their diagrams to identifyand analyze the probability and consequence of potentialmalfunctions for determining related maintenanceor maintainability design requirements.Conceptual phase. The first phase in the material lifecycle. The phase in which the technical, military, andeconomic basis for the program. and concept feasibilityare established through pertinent studies.Configuration control. The systematic evaluation. coordination,approval or disapproval, and implementationof all approved changes in the configuration of a configurationitem after formal establishment of its configurationidentification.Configuration item. An aggregation of hardware software.or any of its discrete portions, which satisfies anend use function and is designated by the Governmentfor configuration management. Configuration itemsmay vary widely in complexity, size, and type, from anaircraft, an electronic or ship system to a test meter orround of ammunition. During development and initialproduction. configuration items are only those specificationitems that are referenced directly in a contract(or an equivalent in-house agreement). During thedeployment phase, any repairable item designated forseparate procurement is a configuration item.Contract data requirements list (CDRL). A listing of alltechnical data and information required to be deliveredto the Government by the contractor.Corrective maintenance. That maintenance performed torestore an item to a satisfactory condition by providingcorrection of a malfunction that has caused degradationof the item below the specified performance.Corrective maintenance time. The time that begins withthe observance of a malfunction of an item and endswhen the item is restored to a satisfactory operatingcondition. It may be subdivided into active maintenancetime and nonactive maintenance time. It does notG-2
Downloaded from http://www.everyspec.com on 2011-10-29T14:56:01.necessarily contribute to equipment or system downtimein cases of alternate modes of operation orredundancy.Criticality. A measure of the impact of the failure mode ofthe item that includes the severity of the effect combinedwith the frequency or probability of occurrence.DDelay time. The component of downtime during whichno maintenance is being accomplished on the itembecause of technician alert and response time, supplydelay, or administrative reasons.Demonstrated. That which has been measured, withinspecified confidence limits, by the use of objective evidencegathered under specified conditions.Dependability. A measure of the degree to which an itemis operable and capable of performing its required functionat any (random) time during a specified missionprofile, given item Availability at the start of the mission.(Item state during a mission includes the combinedeffects of the mission-related system R & Mparameters but excludes nonmission time: see AVAIL-ABILITY.)Depot maintenance. A category of maintenance organizedto support the supply system. It will be productionlineoriented and will be performed by special repairactivities, US Army Materiel Command (AMC) depots,and contractor personnel.Design adequacy. The probability that a system orequipment will successfully accomplish its mission,given that the system is operating within design specifications.Design review. A multipurpose design verification procedureand project management tool used to evaluate thecumulative results of all constituent design verificationcycles at each of several designated major milestones inthe acquisition process in order to provide adequateengineering basis for timely iteration in the total systemengineering cycle.Development model. A model designed to meet performancerequirements of the specification or to establishtechnical requirements for production equipment. Thismodel need not have the required final form or necessarilycontain parts of final design. It may be used todemonstrate the reproducibility of the equipment.Development testing. A series of materiel tests conductedDOD-HDBK-791(AM)by the Army developer—with or without contractorassistance—to assess program technical risks, demonstratethat engineering design is complete and acceptable,determine the extent of the design risks, determinespecification compliance, and assess production requirements.Diagnostics. The functions performed and the techniquesused in determining and isolating the cause of malfunctionsin an operating system or determining its operationalstatus.Direct maintenance man-hours per maintenance action(DMMH/MA). A measure of the maintainabilityparameter related to item demand for maintenancemanpower. The sum of direct maintenance man-hoursat all levels or repair, divided by the total number ofmaintenance actions (preventive and corrective) duringa stated period of time.Direct maintenance resources. The time in man-hoursand material in dollars expended directly on the itembeing maintained during the period of active maintenance.Disassemble. Opening an item and removing a number ofparts of subassemblies to make the item that is to bereplaced accessible for removal. This does not includethe actual removal of the item to be replaced.Discard-at-failure maintenance. Maintenance accomplishedby replacing and discarding a failed assembly,subassembly, module, or piece part. The term normallyis associated with modules.Downtime. That portion of calendar time when the itemcannot perform its intended function.EEase of maintenance. The degree of facility with whichequipment can be retained in, or restored to, operation.It is a function of the rapidity with which maintenanceoperations can be performed to avert malfunctions orcorrect them if they occur. Ease of maintenance isenhanced by any consideration that will reduce the timeand effort necessary to maintain equipment at peakoperating efficiency.Engineering change proposal (ECP). A proposal tochange the design or engineering features of materielundergoing development or production.Environment. The aggregate of all external and internalconditions—such as temperature, humidity, radiation,magnetic and electric fields, shock, and vibration—either natural or man-made or self-induced that influ-G-3
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