Abstract
The reliability of complex systems is analyzed based on several systematic steps using many safety engineering methods. The most common technique for safety system analysis and reliability, vulnerability and criticality estimation is the fault tree analysis method. There exist numerous conventional and fuzzy extended approaches to construct such a tree. One of the steps of the fuzzy fault tree analysis method (FFTA) is the conversion of crisp failure possibility (CFP) into failure probability (FP). This paper points out the drawbacks of one of the formulas for conversion of CFP into FP, and discusses ways to improve the formula for the FFTA. The proposed approach opens a corridor for the researchers to re-think the previous studies, and is susceptible to improve the future applications for safety and reliability engineering.