ADS-79D-HDBK Downloaded from https://www.everyspec.com K.3 DEFINITIONS Accuracy: A measure of how close predicted failure times are to the actual (observed) failure times. Age: A measure of exposure to stress computed from the moment an item or component enters service when new or re-enters service after a task designed to restore its initial capability, and can be measured in terms of calendar time, running time, distance traveled, duty cycles or units of output or throughput. (SAE JA1012) Applicable Task: A task that is capable of preventing or mitigating the consequences of failure based on the technical characteristics of that failure. (SAE JA1011) Appropriate Task:
A task that is both technically feasible and worth doing (applicable and effective). (SAE JA1012) Commercial Off The Shelf (COTS): This term defines equipment hardware and software that is not qualified to aircraft standards. An example of COTS equipment hardware and software is a personal computer (PC) and its operational software. (AC 29-2C) Complexity: A measure of effectiveness defined as the ratio between computational time and expected time to failure . Conditional Probability of Failure: The probability that a failure will occur in a specific period provided that the item concerned has survived to the beginning of that period. (SAE JA1012) Confidence:
The probability that the true reliability is at least as high as what is stated, equal to one minus the probability of a false negative. The target confidence is 90%. (ADS-79C) Criticality: This term describes the severity of the end result of an item or process failure/malfunction. Criticality is determined by an assessment that considers the safety effect that an item or process can have on the aircraft. (ADS79D Appendix L Section 5.1) Damage Fraction: An estimate of fatigue damage due to identified usage and/or fatigue loading where a damage fraction of 1.0 is typically associated with a probability of fatigue crack initiation. Desired Performance:
The level of performance desired by the owner or user of a physical asset or system. (SAE JA1012) Economic Consequences: A classification assigned to failure modes, or multiple failures in the case of hidden failure modes, that do not adversely affect safety, the environment, or operations, but increase cost either from repair or from lost or degraded operations. (SAE JA1011) 185