MAINTAINABILITY DESIGN TECHNIQUES METRIC - AcqNotes.com

Downloaded from http://www.everyspec.com on 2011-10-29T14:56:01.DOD-HDBK-791(AM)Reaction time. The time required to initiate a mission;measured from the time the command is received.Ready time. The period of time during a mission that theitem is available for operation but is not required.Reassembly. A technician task for replacement of itemsremoved to gain access to facilitate repair and for closingthe equipment for return to service.Rebuild. To restore to a condition comparable to new bydisassembling the item to determine the condition ofeach of its component parts, and reassembling it usingserviceable, rebuilt, or new assemblies, subassemblies,and parts.Redundancy. The existence of more than one means foraccomplishing a given task, where some number ofmeans must fail before there is an overall failure to thesystem. Parallel redundancy applies to systems whereboth means are working at the same time to accomplishthe task and either of the systems is capable of handlingthe job itself in case of failure of the other system. Seriesor standby redundancy applies to a system where thereis an alternate means of accomplishing the task, i.e., thestandby redundancy is switched in by a malfunctionsensing device when the primary system fails.Reliability. The probability that an item will perform itsintended function for a specified interval under statedconditions.Reliability centered maintenance (RCM). A concept thatuses decision logic to evaluate and construct maintenancetasks which are based on the equipment functionsand failure modes.Repair. The process of returning an item to a specifiedcondition including preparation, fault location, itemprocurement, fault correction, adjustment and calibration,and final test.Repairability. The capability of an item to be repaired.Repairable item. An item which can be restored to performall of its required functions by corrective maintenance.Repair rate. A measure of repair capability, i.e., thenumber of repair actions completed per unit of time.Repair time. See active repair time.Replacement schedule. The specified periods when itemsof operating equipment are to be replaced. Replacementmeans removal of items approaching the end oftheir maximum useful life, or the time interval specifiedfor item overhaul or rework, and installation of a serviceableitem in its place.Replacing. Substituting one unit for another unit. Usuallydone to substitute a properly functioning unit for amalfunctioning unit.SSelf test. A test or series of tests, performed by a deviceupon itself, that shows whether or not the device isoperating within designed limits. This includes testprograms on computers and automatic test equipmentthat check out their performance status and readiness.Serviceability. The design, configuration, and installationfeatures that will minimize periodic or preventive maintenancerequirements, including the use of special tools,support equipment, skills, and manpower, and enhancethe ease of performance of such maintenance, includinginspection and servicing.Service life. The period of time during which an item canremain in the operational inventory under specifiedconditions of use and maintenance.Servicing. The performance of any act–-other than preventiveor corrective maintenance—required to keep anitem of equipment in operating condition, such as lubricating,fueling, oiling, cleaning, etc. This does notinclude periodic replacement of parts or any correctivemaintenance tasks.Skill level. Level of proficiency required for performanceof a specific job, and the level of proficiency at which anindividual qualifies in that occupational specialty.Sneak circuit. An unexpected path or logic flow within asystem which, under certain conditions, can initiate anundesired function or can inhibit a desired function.Software. That portion of the support subsystem requiredin addition to personnel and hardware. Softwareincludes technical data, computer programs and tapes,training documents, etc.Special tools. Tools peculiar to a specific end product.Standardization. The use of common items, parts, materials,and practices throughout the life cycle of systemsand equipment.Storage time. Time during which a system or equipment ispresumed to be in operable condition but is being heldfor subsequent use.Support cost. The total cost of ownership, excludingoperating crews and using personnel, of an item duringits operational life including the total impact of requirementsfor skill levels; technical data; test, measurement,and diagnostic equipment (TMDE); spares; repairparts; special tools; maintenance equipment; facilities;levels and location of maintenance facilites; manpower;and training and training equipment.Supportability. A measure of the capability of materiel tobe supported easily and economically.G-9