In a

system A system is a group of Interaction, interacting or interrelated elements that act according to a set of rules to form a unified whole. A system, surrounded and influenced by its environment (systems), environment, is described by its boundaries, ...

the mean time between outages (MTBO) is the mean

time Time is the continued sequence of existence and events that occurs in an apparently irreversible succession from the past, through the present, into the future. It is a component quantity of various measurements used to sequence events, to ...

between equipment failures that result in loss of system continuity or unacceptable

degradation Degradation may refer to: Science * Degradation (geology), lowering of a fluvial surface by erosion * Degradation (telecommunications), of an electronic signal * Biodegradation of organic substances by living organisms * Environmental degradation ...

. The MTBO is calculated by the equation,

MTBO = \frac

where MTBF is the nonredundant

mean time between failures Mean time between failures (MTBF) is the predicted elapsed time between inherent failures of a mechanical or electronic system during normal system operation. MTBF can be calculated as the arithmetic mean (average) time between failures of a system ...

and FFAS is the fraction of failures for which the failed equipment is automatically bypassed.

References

{{tech-stub Reliability engineering