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Fault Tree Analysis (FTA)

Problem solvingRoot cause

Reference model

How a fault tree is builtA sequence of 6 steps, read from the first to the last: 1, Define the top event; 2, Identify immediate causes; 3, Link causes with gates; 4, Break down to basic events; 5, Test the root causes; 6, Act on the root causes.Define the top eventState the specific failure youwant to explain, in one clearsentence.1Identify immediatecausesAsk what must happen for thetop event to occur and listthose events.2Link causes with gatesShow whether causes combinewith AND (all needed) or OR(any one is enough).3Break down to basiceventsKeep splitting intermediateevents until you reach causesthat cannot be split…4Test the root causesCheck each basic event againstdata and rank which pathwaysmatter most.5Act on the root causesChoose actions that remove orcontrol the key basic events.6

A fault tree diagram illustrates how various failures can lead to a top-level failure.

About this model

A visual method for analyzing the causes of system failures through a tree-like diagram that breaks down events into their contributing factors.

Originator not stated.

How to read it

  • Start from the top event and work downwards to identify causes.
  • Each branch represents a different pathway leading to the failure.
  • Intermediate events are broken down further until basic events are reached.

What this does

Identifies the root causes of a specific failure or problem by mapping out the pathways of events that lead to that failure.

When to use it

Use it when you need to understand the underlying causes of a failure or issue in a systematic way.

Not when: Do not use it when the problem is too vague or when there is insufficient data to identify potential causes.

What happens next

Consider using a Cause and Effect Diagram to further explore identified causes.

Golden thread

Builds on ←

  • Problem Statement
  • Data Collection

Feeds into →

  • Corrective Action Plan

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Drafted with AI and reviewed by Eccellere on 04/11/2026. Guidance, not advice: apply your own judgement.