FaultTreeAnalysen

FaultTreeAnalysen is a structured, deductive safety and reliability analysis used to understand how a system can fail. In German-language contexts the term is commonly used in the plural form to describe the practice of performing fault tree analyses. The method aims to identify combinations of component failures and other events that can lead to a defined undesired top event, such as a loss of function, hazard, or system shutdown.

A fault tree is a graphical model that starts with the top event at the apex and is expanded downward through logic gates, typically AND and OR, into contributing events. Basic events represent primitive failure causes that cannot be decomposed further within the tree, while intermediate events group related failures. The construction continues until a satisfactory level of detail is reached. The resulting structure allows the identification of minimal cut sets, which are the smallest combinations of basic events that can cause the top event.

Qualitative analysis focuses on identifying critical paths and minimal cut sets, while quantitative analysis estimates the probability or frequency of the top event using data on basic-event failure rates and, where needed, data on common-cause or dependent failures. The analysis may assume independence for simplicity, but more advanced models can incorporate dependencies and uncertainty.

FaultTreeAnalysen find wide use in safety-critical industries such as aerospace, nuclear, chemical processing, and automotive engineering, as well as in broader reliability and risk assessments. They are guided by standards such as IEC 61025, which defines the method and its practice. Strengths include clear visualization and systematic tracing of failure paths; limitations involve data quality, potential model complexity, and the need to address dependencies and assumptions explicitly.