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)Maintainability analysis. The definition of maintainabilitydesign procedures and evaluation of achievement ofmaintainability design goals through use of prediction,verification, demonstration and assessment techniquesto insure that system or equipment design characteristicsmeet operational objectives with a minimum expenditureof maintenance and support effort.Maintainability data. Data (other than administrativedata) resulting from performance of maintainabilitytasks in direct support of an equipment or systemacquisition program.Maintainability demonstration tests. Tests, usually at theequipment or subsystem level, for the major items thatwill comprise the integrated system to demonstrateconformance with specified quantitative maintainabilityrequirements.Maintainability constraints. A group of factors—environmental,human, hardware—which establishes limits tothe performance of maintenance on an item.Maintainability program. The planning, development,and implementation of those organized sets of tasksdirectly related to the specification, prediction, verificationand assessment of the design characteristics of anitem with the goal of meeting operational objectiveswith a minimum expenditure of maintenance and supporteffort.Maintainability requirement. A comprehensive statementof required maintenance characteristics, expressed inqualitative and quantitative terms, to be satisfied by thedesign of an item.Maintenance. All actions necessary for retaining an itemin, or restoring it to, a serviceable condition. Maintenanceincludes servicing, repair, modification, overhaul,inspection, and condition determination.Maintenance ability. A figure of merit for a crew of ausing organization defined as the ratio of maintenanceman-hours established on a specific item by a trainedand expert maintenance crew to the maintenance manhourfigure established by the crew of the using organizationon the same item and under similar maintenanceconditions.Maintenance analysis. The process of identifying requiredmaintenance functions through analysis of a fixed orassumed design and determining the most effectivemeans of accomplishing these functions.Maintenance category. Division of maintenance of materiel,based on difficulty and requisite technical skill, inwhich jobs are allocated to organizations in accordancewith the availability of personnel, tools, supplies, andtime within the organization.Maintenance concept. A description of the general schemefor maintenance and support of an item in the operationalenvironment.Maintenance element. A discrete portion of a maintenancetask which can be described or measured.Maintenance engineering. The application of techniques,engineering skills. and effort during the life cycle ofmateriel to insure the planning and implementation ofan effective maintenance program.Maintenance error. An error on the part of maintenancepersonnel in performing maintenance on an item whichresults in subsequent failure or malfunction, or an errorin published maintenance procedures which results insubsequent failure or malfunction. (Note: Items removedbecause of maintenance errors are consideredUnscheduled Removals. )Maintenance functions. Actions that must be accomplishedfor a system or system element to return a failedsystem element to readiness (corrective maintenancefunctions) or to insure continuing normal system readiness(preventive maintenance functions).Maintenance level. One of several organizational entitiesto which materiel maintenance functions may beassigned. The maintenance levels are unit, intermediate,and depot.Maintenance man-hours. The number of active maintenanceman-hours—total number of maintenance personnelrequired multiplied by number of hours workedto perform a maintenance operation.Maintenance plan. A part of the plan for logistic support.The maintenance plan contains conditions of materieluse, reliability and maintainability requirements, themaintenance concept, a definition of the using andsupport organizations, maintenance test and physicalteardown information, and a maintenance allocationchart.Maintenance procedures. Established methods for periodicchecking and servicing items to prevent failure orto effect a repair.Maintenance proficiency. The ability of maintenance personnelto apply job skills in the maintenance of an item.Maintenance resources. Facilities; ground support equipment;test, measurement, and diagnostic equipment(TMDE); manpower; repair parts; consumables; andfunds available to maintain and support an item in itsoperational environment.Manpower and personnel integration (MANPRINT). Aprogram whose purpose is to impose human factors,manpower, personnel, training, system safety, andhealth hazard considerations across the entire materielacquisition process.G-6
Downloaded from http://www.everyspec.com on 2011-10-29T14:56:01.Maintenance task. Any action or actions required to precludethe occurrence of a malfunction or to restore anequipment to satisfactory operating condition.Malfuction. A general term used to denote the failure ofa product to give satisfactory performance. It need notconstitute a failure if readjustment of operator controlscan restore an acceptable operating condition.Maximum time to repair (Mmax ct). The maximum timerequired to complete a specified percentage of all maintenanceactions.Mean. A quantity representing the average of two ormore other quantities arrived at by adding the quantitiestogether and dividing by their number. Also called“arithmetic mean”. The “geometric mean” of two quantitiesis the square root of the product of the quantities.Mean maintenance time. The mean time required tocomplete a maintenance action, i.e., total maintenancedowntime divided by the total maintenance actions.Mean time between downtime events (MTBDE). A measureof the system reliability parameter related to availabilityand readiness. The total number of system lifeunits, divided by the total number of events in which thesystem becomes unavailable to initiate its mission(s),during a stated period of time.Mean time between failures (MTBF). The totat functioninglife of a population of an item divided by the totalnumber of failures within the population during themeasurement interval. The definition holds for time,cycles, miles, events, or other measures of life units.Mean-time-to-correct-failure. The expected value of thetime required to restore an equipment or system to acondition of satisfactory operation, measured from themoment it is judged unsatisfactory for normal use.Mean task time. A representative task time equal to thesummation of task times required to perform a specifictask a number of different times divided by the numberof times performed.Mean-time-to-repair (MTTR). The statistical mean of thedistribution of times-to-repair. The summation ofactive repair times during a given period of time dividedby the total number of malfunctions during the sametime interval.Mean-time-to-restore-system (MTTRS). A measure ofthe system maintainability parameter related to availabilityand readiness. The total corrective maintenancetime, divided by the total number of downing events,during a stated period of time. (Excludes time for offsystemmaintenance and repair of detached components.)DOD-HDBK-791(AM)Median corrective maintenance time The downtimewithin which 50% of all corrective maintenanceactions can be completed under the specified maintenanceconditions. (Also called Equiment Repair Time(ERT).)Median preventive maintenance time The equipmentdowntime required to perform 50% of all scheduledpreventive maintenance actions on the equipmentunder the specified conditions.Military standard. A document that establishes engineeringand technical requirements for items, equipments,processes, procedures, practices, and methods thathave been adopted as standard.Military specification. A document intended primarilyfor use in procurement, which clearly and accuratelydescribes the essential technical requirements for items,materials, or services, including the procedures bywhich it will be determined that the requirements havebeen met. Specifications for items and materials mayalso contain preservation-packaging, packing, andmarking requirements.Minimum acceptable value (MA V). A minimum valueconsistent with system operation and support concepts.Mission reliability. The probability that, under statedconditions, a system or equipment will operate in themode for which it was designed, i.e., with no malfunctions,for the duration of a mission, given that it wasoperating in this mode at the beginning of the mission.Mission time. The period of time in which an item mustperform a specified mission.Model. Any device, technique, or process with which thespecific relationships of a set of quantifiable systemparameters may be investigated.Modification. A major or minor change in the design ofan item of materiel, performed to correct a deficiency,to facilitate production, or to improve operationaleffectiveness.Modularization. The design of equipment such that itsfunctional grouping, arrangement and size and partsand/or assemblies improve both the ability to test andease of maintenance.Module. A part, subassembly, assembly, or componentdesigned to be handled as a single unit to facilitatesupply and installation, operations, and/ or maintenance.NNational inventory control point (NICP). An organizationalsegment, within the overall supply system of acommodity command, to which has been assignedG-7
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