ISO 14224

A closed-loop process for systematically reporting failures, analyzing their root causes, implementing corrective actions, and verifying that those actions effectively prevent recurrence. FRACAS captures failure data, triggers investigation based on severity, tracks corrective action implementation, and feeds lessons learned back into the design, maintenance, and operating procedures.

The average time between consecutive failures of a repairable system or component, calculated as the total operating time divided by the number of failures during that period. MTBF is the primary reliability metric for repairable systems and represents the expected time of continuous operation between failure events. Higher MTBF indicates better reliability.

The average number of failures per unit of time for a population of items, typically expressed as failures per hour, per year, or per million hours. Failure rate (lambda) is the reciprocal of MTBF for constant-failure-rate systems. It is a statistical average measure, distinct from the instantaneous hazard rate, and is most accurate when the failure rate is approximately constant (beta near 1).

The specific manner in which a component, subsystem, or system fails to perform its intended function or performs it in an unintended way. A failure mode describes the observable manifestation of a failure — what goes wrong — rather than why it goes wrong (failure cause) or what happens as a result (failure effect). Each functional failure may have multiple failure modes.

A documented occurrence of equipment failure, degradation, or near-miss that is recorded in a reliability database for analysis. Reliability events capture the equipment affected, the failure mode, the failure cause, the failure effect, the detection method, the operating conditions at the time of failure, and the corrective action taken. They form the raw data for reliability analysis, trending, and FRACAS.