Document Type : Regular Article


Yale School of Engineering & Applied Science (SEAS), Yale University, New Haven. CT 06520, USA



This research provides a reliability-based quantitative failure analysis of different architectural designs of the environmental control system (ECS) in commercial aircraft. The scope of analysis includes the two-, three-, and four-wheel ECS architectures. Reliability block diagrams (RBD) are developed and quantified for the three architectures and quantified using recently published components failure rate data. Components contributions to the reliability of each of the modeled ECS architectures are calculated as well as their Birnbaum’s components importance measures. The results of this analysis show that the two-wheel architecture has a mean time between failure (MTBF) of » 21,438 hours, while the three-wheel architecture has an MTBF of » 14,050 hours, and the four-wheel architecture has an MTBF of » 13,634 hours. ECS reliability decreased by » 34.5% through adoption of the three-wheel architecture, and by 36.4% through adoption of the four-wheel architecture, as compared to the simple two-wheel ECS architecture. The calculated Birnbaum’s importance measures show that the most critical component in the two-wheel architecture is the cabin air circulation fan (CACF). For the three-wheel and four-wheel ECS architectures, the most important component is the condenser. The key contributions of this research are: 1) addressing current gap in the state of knowledge about ECS design life prediction and 2) providing insights into ECS reliability-based failure analysis.


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