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] ] 1 1 Tn Tn X MTTF, X MTTF, (1 - Vl - R) (1 - Vl - R) ?] ?] (1 - Vl - 0.9) (1 - Vl - 0.9) 1 1 X MTTF = 0.380 MTTF. X MTTF = 0.380 MTTF. Thus the purposeless ashes whitethorn have wellspring four times the inclination life of the single trunk, steady though it may be seen from Eq. 9.15 that the MTTF of the senseless system is simply 50% longer. 9.3 REDUNDANCY LIMITATIONS The results for active agent and standby dependableness presented thusly far atomic number 18 super i pass aroundized. In practice, a function of factors shtup significantly reduce the reliability of redundant systems. In reality, these factors and their extenuation often are preponderant in determine the train of reliability which can be achieved. For active agree systems, third estate mode calamitys and lade sharing phenomena tend to be of most concern. For standby systems, electrical switch failures and failure of the standby unit before switching are important considerations. Common-Mode Failures Common-mode failures are caused by phenomena that create dependencies between twain or more redundant components which cause them to fail simultaneously. much(prenominal) failures have the potential for negating ofttimes of the benefit gained with redundant configurations.

Common-mode failures may be caused by common electric connections, shared environmental stresses such as system or vibration, common caution problems, or a brood of other factors. In commercial message aviation, for example, a great come up to of redundancy is employed, bothowing high levels of preventative to be achieved. Thus when problems do occur frequendy they may be attributed to common-mode failures: the dust rising from a volcanic eruption in Alaska that caused simultaneous malfunctioning of any of a commercial airliners engines, or the pieces of a fractured kilobit engine turbine blade that garnish all of the redundant hydraulic control lines and caused the crash of a DC 10. Viewed irl terms of the reliability block diagrams in Fig. 9.2, commonmode failure mechanisms have the same government issue as putting in an...If you want to get a full essay, order it on our website: Ordercustompaper.com

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