scope:

Fault tree analysis (FTA) is used to identify and analyse combinations of events, conditions and factors that cause or can potentially cause or contribute to the occurrence of a defined undesirable outcome, referred to as the "top event". This document describes the (FTA) technique and provides guidance on its application. This includes: - definition and description of commonly used terms and symbols; - purpose, applications and limitations of FTs; - a description of basic concepts and principles; - a description of the steps involved in scoping, constructing and developing the FT; - guidance on performing qualitative and quantitative analysis of the FT, including discussion of requirements and limitations of the associated mathematical models; - identification of basic items that should be included when documenting and reporting the FTA; - methods for performing FTA when some of the commonly used assumptions are not satisfied (e.g., non-coherent FTs, dynamic FTs); - example applications in support of the above; - procedures for calculating dependability measures (unavailability, failure frequency and unreliability) for different types of system, with constant or time dependent probabilities or with non-repaired or repaired items)