Materiel Reliability is a measure of the probability that the system will perform without failure over a specific interval. Reliability must be sufficient to support the warfighting capability needed. Materiel Reliability is generally expressed in terms of a mean time between failure(s) (MTBF), and once operational can be measured by dividing actual operating hours by the number of failures experienced during a specific interval.
Reliability may initially be expressed as a desired failurefree interval, which can be converted to MTBF for use as a KSA. (e.g. 95% probability of completing a 12 hour mission, free from missiondegrading failure; 90% probability of completing 5 sorties without failure, etc.) Specific criteria for defining operating hours and failure criteria must be provided together with the Key System Attribute (KSA). Singleshot systems and systems for which other units of measure are appropriate must provide supporting analysis and rationale.
