عنوان مقاله [English]
Following the development of the aerospace industry, the concept of reliability has attracted much attention in the field of mechanical engineering. However, limited failure data and statistical analyses of helicopter component reliability exist in technical literature. For filling this gap, a nonparametric analysis is conducted on the performance of the 338 blades of Iranian helicopter 205, which was in service between 1974 and 2012. These blades have 41 different failure modes. In this paper, using statistical analysis, the reliability of the helicopter blade 205, which has multiple failure modes, is obtained. The Kaplan-Meier estimator is used for calculating the nonparametric reliability functions. Confidence intervals for the nonparametric reliability results are derived, and parametric fit, with 3-parameter Weibull distribution, using maximum likelihood estimation (MLE) and a graphical approach, is conducted. In addition, the blade is assumed to be subjected to different modes of failure, and the cumulative mode-specific functions are derived for each failure mode using a Nelson-Aalen estimator. An important result from parametric analysis is that blade reliability has a 3-parameter Weibull distribution, and, so, the blades exhibit an increasing failure rate. Finally, considering the mode-specific hazard functions, failure mode 1, i.e., excessive vibration, is observed to be a major contributor to blade failure.