MTD

MTD (Maintenance Task Distribution) （メンテナンスタスク分配）

MTD was a required input variable in earlier versions of VMetric. The sum of the maintenance task distributions for operating sites, intermediate sites and the depot, plus the condemnation rate, was required to be one.  MTD is not an appropriate concept in a more flexible model such as XL where the number of support sites between an operating site and the procurement source may vary. MTD has been replaced by Not Reparable This Station (NRTS) in TEMPO, because NRTS, the fraction of demand not reparable this station, depends only on the site itself. There is no stipulation as to the sum of NRTS rates.

The relationship between NRTS and MTD is shown in the following equations:

NRTSs   = 1 - MTDs

NRTSi = 1 - MTDi / (1-MTDs)

NRTSd   = 1 - MTDd / (1-MTDs-MTDi)

where we have used the subscript s for operating site, i for intermediate or next level support site, and d for depot or next higher level support site.

For example, if the MTD values for MTDs, MTDi, and MTDd were .40, .30, and .15, respectively, NRTS would be calculated as follows:

NRTSs   = 1 - .40 = .60

NRTSi = 1 - .30 / (1-.60) = .5

NRTSd   = 1 - .15 / (1-.40 - .30) = .5

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