Mean time to repair (MTTR) is a basic measure of the maintainability of

repairable A repairable component is a component of a finished good that can be designated for repair. Overview Repairable components tend to be more expensive than non-repairable components (consumables). This is because for items that are inexpensive to ...

items. It represents the

average In ordinary language, an average is a single number taken as representative of a list of numbers, usually the sum of the numbers divided by how many numbers are in the list (the arithmetic mean). For example, the average of the numbers 2, 3, 4, 7, ...

time required to repair a failed component or device. Expressed mathematically, it is the total

corrective maintenance Corrective maintenance is a maintenance task performed to identify, isolate, and rectify a fault so that the failed equipment, machine, or system can be restored to an operational condition within the tolerances or limits established for in-servi ...

time for failures divided by the total number of corrective maintenance actions for failures during a given period of time. It generally does not include lead time for parts not readily available or other Administrative or Logistic

Downtime The term downtime is used to refer to periods when a system is unavailable. The unavailability is the proportion of a time-span that a system is unavailable or offline. This is usually a result of the system failing to function because of an un ...

(ALDT). In

fault-tolerant design Fault tolerance is the property that enables a system to continue operating properly in the event of the failure of one or more faults within some of its components. If its operating quality decreases at all, the decrease is proportional to the ...

, MTTR is usually considered to also include the time the fault is latent (the time from when the failure occurs until it is detected). If a latent fault goes undetected until an independent failure occurs, the system may not be able to recover. MTTR is often part of a maintenance contract, where a system whose MTTR is 24 hours is generally more valuable than for one of 7 days if mean time between failures is equal, because its Operational

Availability In reliability engineering, the term availability has the following meanings: * The degree to which a system, subsystem or equipment is in a specified operable and committable state at the start of a mission, when the mission is called for at a ...

is higher. However, in the context of a maintenance contract, it would be important to distinguish whether MTTR is meant to be a measure of the mean time between the point at which the failure is first discovered until the point at which the equipment returns to operation (usually termed "mean time to recovery"), or only a measure of the elapsed time between the point where repairs actually begin until the point at which the equipment returns to operation (usually termed "mean time to repair"). For example, a system with a service contract guaranteeing a mean time to "repair" of 24 hours, but with additional part lead times, administrative delays, and technician transportation delays adding up to a mean of 6 days, would not be any more attractive than another system with a service contract guaranteeing a mean time to "recovery" of 7 days.

References

{{Reliability indices Engineering failures Reliability indices de:Mean Time To Recover fr:MTTR ja:平均修復時間 sv:MTTR

See also

References