Fault Tree Analysis
What is Fault Tree Analysis?
Fault tree analysis (FTA) is a systematic risk analysis technique used to identify and visualize potential failures within a system, focusing on their root causes and the events that could lead to undesired outcomes, such as system malfunctions or safety hazards. FTAs are widely used in high-risk industries—such as aerospace, healthcare, and engineering—to enhance safety, improve reliability, and inform decisions.
The Basic Idea
Imagine that your car headlights fail to turn on automatically when it gets dark. To properly fix the issue and be on your way, you must first identify the cause of failure. There are two common reasons: either the electrical system or the physical bulbs are failing. To determine what is causing either the electrical system or bulbs to fail, you can conduct a fault tree analysis.
The purpose of a fault tree analysis is to systematically and logically break down a problem into its possible causes, helping to identify the root cause and prevent similar failures in the future. In a fault tree analysis, the fault is described as the top-level or top event. Next, intermediate events are identified—in this case, electrical system failure or auto part failure. Since either of these intermediate events would lead to the top event, they are represented through an “OR” logic gate, which shows that either event is sufficient to lead to the top-level event. Next, you would map out the basic events that could lead to these two intermediate events, such as a faulty sensor or bulb.1
Conducting an FTA has helped you to outline the logical relationships between events, providing you with a visual diagram to find the root cause of the problem. Now that you’ve identified the basic events, you can further investigate the source of the failure by testing the sensors or examining the light bulbs for physical damage.
Fault tree analyses allow us to understand the relationships between events in a complex system and tackle problems methodically, exploring each event to ultimately determine the root cause of the issue.2 FTAs are primarily used in industries with complex systems—such as the automotive and aviation industries, energy and power generation, or manufacturing—where safety, reliability, and risk management are critical.
“The fundamental concept of a Fault Tree Analysis is the translation of the failure behavior of a physical system into a visual diagram and logic model... A very simple set of rules and symbols provides the mechanism for analyzing very complex systems, and complex relationships between hardware, software, and humans.”
— Clifton Ericson II, an expert in system and software safety and reliability and author of multiple books on fault tree analysis.4
About the Author
Emilie Rose Jones
Emilie currently works in Marketing & Communications for a non-profit organization based in Toronto, Ontario. She completed her Masters of English Literature at UBC in 2021, where she focused on Indigenous and Canadian Literature. Emilie has a passion for writing and behavioural psychology and is always looking for opportunities to make knowledge more accessible.
