In the last lew years of the seventies

the fault tree of the noncoherent system was applied in the reliability analysis of complex systems. The most difficult thing in such analysis is how to simplify the fault tree. This paper presents a simpler method called search method to simplify the fault tree. In the paper some convenient techniques based on the application of the basic rules of logic algebra are used to reduce the search work. The search method can fully meet the needs of engineering calculation.As an example

the L-P fault tree has been simplified by this method and twenty prime implicants have been obtained. However

the term

minimum cut set

is still used instead of the term

prime implicant

because the search method is not a strict mathematical method and the term

minimum cut set is more familiar to most engineers.