Fault Tree Analysis / FMEA
Updated 2026-08-13
INTRODUCTION
English translation pending.
CORE DEFINITION
The combination pairs two reliability methods. Fault tree analysis starts from a defined top event, such as a system failure, and decomposes it downward through the logical conditions that could produce it. Failure mode and effects analysis works upward from components, listing each failure mode, its cause, its effect, and ratings for severity, occurrence, and detection, whose product is the risk priority number. The core claim is that the two directions cover each other's blind spots, since one traces causes of a known failure and the other predicts effects of unknown ones. The qualification is that the ratings are judgments, so arbitrary thresholds misallocate attention.
SCAFFOLDING EFFECT
Reduce cognitive load
- Define the top event: state the failure whose causes you need to trace downward. - Enumerate modes: list each component's failure modes with cause, effect, and ratings. - Score and act: rank the risk priority numbers and specify prevention and detection controls.
Anchor fast decisions
A failure that has already occurred is easiest to explain backward, which is what the fault tree does, while a failure that has not occurred must be anticipated forward from components, which is what the analysis of failure modes does. Running both directions closes the gap left by either alone, since each direction surfaces items the other misses. Ranking by the product of severity, occurrence, and detection concentrates effort where risk is highest. The rankings are expert judgments, so the ordering is only as good as the scoring.
MINIMUM ACTION
In progress 0/1Practice this model in one real situation:
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Source support: Explicit
- en.wikipedia.orghttps://en.wikipedia.org/wiki/Fault_tree_analysisverified
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