MAINTAINABILITY DESIGN TECHNIQUES METRIC - AcqNotes.com

Downloaded from http://www.everyspec.com on 2011-10-29T14:56:01.DOD-HDBK-791(AM)GLOSSARYAAccessibility. A design feature that affects the ease ofadmission to an area for the performance of visual andmanipulative maintenance.Active maintenance time. The time during which preventiveand/ or corrective maintenance work is being doneon the item.Availabifity. A measure of the degree to which an item isin operable and committable state at the start of themission, when the mission is called for at an unknown(random) point in time.AvailabiIity (achieved). The percentage of time the systemis operating when considering only operating time andtotal maintenance (scheduled and unscheduled) time.The equation isActive repair time. The time during which one or moretechnicians are working on the item to effect a repair.Active technician time. That time (expressed in manhours)expended by the technician(s) in active performanceof a maintenance task.Adjustment and calibration time. That element of activemaintenance time required to make the adjustmentsand/or calibrations necessary to place the item in aspecified condition.Administrative time. The downtime due to nonavailabilityof test equipment or maintenance facilities and thetime due to nonavailability of maintenance technicianscaused by administrative functions. It is that portion ofnonactive maintenance time that is not included inlogistic time.Alignment. Performing the adjustments that are necessaryto return an item to a specified level of operation.Artificial intelligence (AI). A field aimed at pursuing thepossibility that a computer can be made to behave in amanner that humans recognize as intelligent behaviorin each other.Automatic test equipment (ATE). Equipment designed toconduct automatically the analysis of functional orstatic parameters and to evaluate the degree of theperformance degradation of the unit under test. Thetest equipment is not an integral part of the unit undertest.Automatic testing. The process by which the localizationof faults, possible prediction of failure, or validationthat the equipment is operating satisfactorily is determinedby a device that is programmed to perform aseries of self-sequencing test measurements without thenecessity of human direction after its operations havebeen initiated.whereOTCTCM =TPM =A a=operating time during a given calendartime periodtotal corrective (unscheduled) maintenancedowntime during a givencalendar time periodtotal preventive (scheduled) maintenancedowntime during a given calendartime periodachieved availability.Availability (inherent). The percentage of time the systemis operating when considering only operational timeand unscheduled (corrective) maintenance time. Theequation iswhereOT = operating time during a given calendartime periodTCM = total corrective (unscheduled) maintenancedowntime during a givencalendar time periodA, = inherent availability.Availability (operational). A measure of the degree towhich an item is either operating or is capable of operatingat any random point in time when used in a typicalmaintenance and supply environment. The equation iswhereOT = operating time during a given calendartime periodG-1