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    Fault Tree Analysis

    Top-down deductive analysis tracing how faults can combine to cause an undesired event.

    Reviewed by Christian Espinosa, Founder, Blue Goat CyberLast reviewed September 19, 2026

    Definition

    FTA per IEC 61025 uses Boolean logic to model how component-level faults and external events combine to cause a defined top-level hazardous event, supporting both qualitative and quantitative analysis. FTA is a top-down method: it starts from an undesired event, such as overdose delivered, and works down through AND and OR gates to basic causes. It complements bottom-up FMEA by revealing combinations of faults and common-cause failures. In medical devices it is often used for high severity hazards and software-controlled safety functions, and quantitative FTA needs reliable failure rate data.
    What the regulation says
    Fault Tree Analysis (FTA) is recognized by regulatory bodies as a systematic risk analysis technique. For instance, the FDA emphasizes comprehensive risk management per 21 CFR Part 820, Quality System Regulation, which can include FTA. Under the EU MDR (Regulation (EU) 2017/745) Annex I, General Safety and Performance Requirements, manufacturers are required to establish, implement, document, and maintain a risk management system, for which FTA can be a valuable tool.

    What this means in practice

    Often paired with FMEA: FTA reasons backward from a harm; FMEA reasons forward from components. FTA is favored for systems with safety-critical software and rare catastrophic failure modes.

    Examples

    • A medical device manufacturer uses FTA to analyze how a combination of software bugs, sensor malfunctions, and user errors could lead to an incorrect drug dosage delivery by an infusion pump.
    • A team developing an AI-powered diagnostic tool employs FTA to map out how various system component failures and data integrity issues could result in a misdiagnosis, identifying critical control points.
    • A cybersecurity team utilizes FTA to determine the pathways by which a denial-of-service attack could successfully incapacitate a networked hospital imaging system, informing their mitigation strategies.
    Common pitfalls
    • •Failing to clearly define the top-level event can lead to a convoluted and ineffective fault tree.
    • •Overlooking common cause failures or human error in the fault tree can significantly underestimate risk.
    • •Treating FTA as a standalone activity rather than an iterative part of the product lifecycle reduces its effectiveness.
    • •Applying FTA to systems without well-defined failure modes or clear causal relationships can yield misleading results.
    • •Not adequately validating the fault tree against real-world data or expert opinion can compromise its accuracy and credibility.

    Frequently asked questions

    FTA provides a structured, top-down approach to identify root causes of system failures, directly supporting the requirements of ISO 14971:2019 for risk analysis by helping to identify hazards and hazardous situations.

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    Sources

    3 sources

    Sources support the definition or relevant regulatory context, not necessarily every claim on this page. Each is graded against our source-tier hierarchy so you can see what rests on binding law versus commentary.

    Tier 1Binding law and standards· 1Tier 2Regulator guidance and consensus· 1Tier 4Trade press and expert commentary· 1
    Link health: 3 verified· last checked 2026-06-20
    IEC·1MDIC·1FDA·1
    1. 1
      IEC 61025
      Tier 1 Verified
      IECwebstore.iec.ch
    2. 2
      MDIC Case for Quality
      Tier 4 Verified
      MDICmdic.org
    3. 3
      FDA - Quality Systems
      Tier 2 Verified
      FDAfda.gov

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