Based on ICH Q9, Quality Risk Management, the Fault Tree Analysis (FTA) tool is an approach that assumes failure of the functionality of a product or process. This tool evaluates system or sub-system failures one at a time or combine multiple causes of failure by identifying causal chains. It is used for investigations and deviations to understand how multiple factors affect a given issue, and to establish the pathway to the root cause of the failure and resolve the issue. The output of FTA includes a visual representation of failure modes as below example.

Reference

1. ICH Q9: Quality Risk Management