Exploring Fault Tree Analysis: Introduction to FTA

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Donia Chauch

Chief Technology Officer

Fault Tree Analysis (FTA) is a powerful analytical tool used to explore and understand various events and their interconnections within a system that can lead to an undesired event (UE).

This structured approach allows for a thorough investigation of the system to anticipate and prevent potential failures, errors, and other unexpected occurrences. Let’s delve deeper into the various facets of FTA and examine its primary purpose, functionalities, and significance in system evaluation and decision making.

Primary Purpose of FTA

This robust approach, using a structured methodology and logic gates, offers insightful system perspectives, showcasing all possible problem causes. By translating graphical models into mathematical ones, FTA computes failure probabilities, continually updating alongside design development. Two main applications of FTA exist: proactive FTA, used during system development to preclude future issues, and reactive FTA, employed post-incident to examine and understand what occurred. Both applications use identical techniques, with reactive FTA integrating mishap evidence.

As a safety analysis tool, FTA provides a detailed illustration of event interrelationships within a system, assisting in determining the significance and probability of fault events. This aids in making informed decisions related to risk acceptability and necessary preventive measures. By focusing only on system elements contributing to the undesired event, FTA ensures efficient and effective analysis, advocating its application as early in the design process as possible for cost-effectiveness. The results of FTA can be used for various purposes, including verifying design compliance, identifying design deficiencies, establishing preventive measures, and modifying safety requirements. Ultimately, FTA stands as a comprehensive tool for examining and understanding systems to prevent and address undesired events systematically and effectively.

Functionalities of FTA

FTA stands out by providing a holistic evaluation of intricate systems and their interrelationships. This analysis is not merely theoretical; it delivers a detailed graphical model, representing various events and their links visually. This visual representation is translated into a probability model, enabling the calculation of the likelihood of different events and their impact on the overall system.

1. Evaluation of Complex Systems:

  • Safety Analysis: FTA effectively evaluates the potential for hazardous and catastrophic events within a system, assisting in the implementation of preventive measures to enhance safety.
  • Reliability Analysis: By analyzing system unavailability, FTA helps in improving the reliability of systems, ensuring consistent and efficient performance.
  • Performance Analysis: FTA evaluates unintended functions within a system, aiding in optimizing its performance and eliminating or mitigating unexpected issues.

2. Graphical and Probability Model:

  • The graphical model provides a visual representation, allowing for a more straightforward, understandable analysis.
  • The probability model offers quantitative insights, facilitating precise risk assessment and decision making.


FTA for System Evaluation

FTA is indispensable for assessing various aspects of a system:

  • Safety Evaluation: FTA plays a crucial role in identifying potential hazards and catastrophic events, aiding in the development of robust safety protocols to prevent such occurrences.
  • Reliability Evaluation: It is instrumental in analyzing and enhancing the reliability of a system by identifying and addressing factors leading to system unavailability.
  • Performance Evaluation: By detecting and assessing unintended functions, FTA contributes to enhancing the overall performance of a system.


FTA for Decision Making: 

FTA is not limited to system analysis; it plays a vital role in informed decision-making processes:

Root Cause Analysis:

  • FTA helps in identifying the root causes of problems, offering insights into potential solutions and improvements.

Risk Assessment:

  • By analyzing various events and their probabilities, FTA facilitates comprehensive risk assessment, enabling the development of effective risk management strategies.

Design Assessment:

  • FTA aids in assessing and enhancing the design of a system, ensuring it is robust, reliable, and efficient.

Understanding and Application

For non-complex systems, basic knowledge of FTA is sufficient, but a deeper understanding is crucial for more complex systems. It is easy to learn and apply, with the level of difficulty in its application depending on system complexity and the analyst’s skill. Even though it’s more challenging than techniques like Preliminary Hazard Analysis (PHA), it doesn’t require extensive mathematical knowledge, making it accessible and practical.

Reputation and Criticism

FTA holds a favourable reputation among system safety analysts across various industries. It’s a significant tool for providing necessary probability calculations for verifying numerical requirements, with many commercial computer programs available to assist analysts. Despite some criticism for not always providing extremely precise probabilities, FTA offers comparable results to other tools like Markov Analysis (MA), with simpler modelling. It’s primarily used as a root cause analysis tool, while also offering a probability risk assessment.


In conclusion, Fault Tree Analysis emerges as an invaluable tool for the comprehensive evaluation of systems and effective decision-making. Its ability to identify, analyze, and provide solutions for potential events leading to undesired outcomes makes it a crucial asset in enhancing the safety, reliability, and performance of systems across various domains.

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