How do I install the Fta Fmea skill?

Run npx skillmds@latest add ashfordeou/fta-fmea in your terminal (requires Node.js), paste this page's agent-chat prompt into Claude, Cursor, or any MCP-connected agent, or download the SKILL.md file and copy it into your agent's skills directory.

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Is Fta Fmea free to use?

Yes. Installing skills from SkillMD is free. This skill is licensed under Apache-2.

Who published Fta Fmea?

ashfordeOU (@ashfordeou) published this skill. Their other Agent Skills are listed on their SkillMD profile.

Fta Fmea by ashfordeou — Agent Skill

Name: Fta Fmea
Author: ashfordeOU

Fta Fmea

Use when scoping or executing FTA (fault tree analysis) and FMEA (failure modes and effects analysis) per ARP4761A: compute minimal cut sets from AND/OR gate structures, check cut-set probability sanity against the top event probability, select the analysis set for an assurance level (FTA/FMEA always, CCA at levels A and B), and map FMEA failure-condition severity to development assurance levels. Pairs with ARP4754A development assurance; all logic is deterministic, offline stdlib. Trigger: fault tree, FTA, FMEA, FMECA, cut set, minimal cut set, failure modes, common cause, severity, probability.

ashfordeOU Updated Sep 17, 2026

File contents

ARP4761A FTA/FMEA (systems-engineering-safety/arp4761a/fta-fmea)

Use when the task is fault tree analysis or FMEA/FMECA work per ARP4761A: deriving minimal cut sets, sanity-checking cut-set probabilities, scoping the analysis set by assurance level, and mapping failure-condition severity.

Domain quick reference

FTA models a top event as a tree of AND/OR gates over basic events; a minimal cut set is a smallest set of basic events whose joint occurrence forces the top event.
OR gates union their children's cut sets; AND gates take the cartesian product, so each combination becomes one cut set.
Cut-set probability is the product of its basic-event probabilities; a cut set more likely than the top event signals a modeling or probability error.
FMEA catalogues failure modes and effects; severity classes map to development assurance levels: A = Catastrophic, B = Hazardous, C = Major, D = Minor, E = No safety effect.
The analysis set scales with level: FTA and FMEA at every safety-significant level, CCA (ZSA/PRA/CMA) added at levels A and B.

Workflow

Confirm the certification basis and the approved safety plan.
Build the fault tree structure (gate nodes with op AND/OR and children; leaves are basic events).
Derive minimal cut sets and check cut-set probability sanity against the top event probability.
Scope the analysis set per assurance level (FTA/FMEA, plus CCA at A/B).
Run FMEA and map failure-condition severities to levels.

Pitfalls

AND gates unioned instead of multiplied (missing combinations).
Cut-set probabilities above the top event probability left unexplained (model or probability error).
CCA dropped at levels A/B where common-cause analysis is expected.
Severity mapped without the FHA-to-PSSA-to-SSA chain.

Behavior contract (gate 3)

The logic is exercised by the gate 3 contract test: scripts/test_fta_fmea.py against scripts/fta_fmea_logic.py (stdlib unittest, offline). Run: python3 scripts/test_fta_fmea.py

Compliance

Standards referenced, not reproduced: ARP4761A / ARP4754A text is proprietary (SAE); summary-only per standards-map.yaml and brief 06.
Revision note: ARP4754B (2023) supersedes ARP4754A; this skill keys to ARP4754A as the certification-baseline revision (FAA AC 20-174 cites A); see standards-map.yaml arp4754a.revision_decision.
compliance: STANDARDS-REF, gated: false.

---name: fta-fmeadescription: Use when scoping or executing FTA (fault tree analysis) and FMEA (failure modes and effects analysis) per ARP4761A: compute minimal cut sets from AND/OR gate structures, check cut-set probability sanity against the top event probability, select the analysis set for an assurance level (FTA/FMEA always, CCA at levels A and B), and map FMEA failure-condition severity to development assurance levels. Pairs with ARP4754A development assurance; all logic is deterministic, offline stdlib. Trigger: fault tree, FTA, FMEA, FMECA, cut set, minimal cut set, failure modes, common cause, severity, probability.license: Apache-2.0---# ARP4761A FTA/FMEA (systems-engineering-safety/arp4761a/fta-fmea)Use when the task is fault tree analysis or FMEA/FMECA work perARP4761A: deriving minimal cut sets, sanity-checking cut-setprobabilities, scoping the analysis set by assurance level, andmapping failure-condition severity.## Domain quick reference- FTA models a top event as a tree of AND/OR gates over basic events; a minimal cut set is a smallest set of basic events whose joint occurrence forces the top event.- OR gates union their children's cut sets; AND gates take the cartesian product, so each combination becomes one cut set.- Cut-set probability is the product of its basic-event probabilities; a cut set more likely than the top event signals a modeling or probability error.- FMEA catalogues failure modes and effects; severity classes map to development assurance levels: A = Catastrophic, B = Hazardous, C = Major, D = Minor, E = No safety effect.- The analysis set scales with level: FTA and FMEA at every safety-significant level, CCA (ZSA/PRA/CMA) added at levels A and B.## Workflow1. Confirm the certification basis and the approved safety plan.2. Build the fault tree structure (gate nodes with op AND/OR and children; leaves are basic events).3. Derive minimal cut sets and check cut-set probability sanity against the top event probability.4. Scope the analysis set per assurance level (FTA/FMEA, plus CCA at A/B).5. Run FMEA and map failure-condition severities to levels.## Pitfalls- AND gates unioned instead of multiplied (missing combinations).- Cut-set probabilities above the top event probability left unexplained (model or probability error).- CCA dropped at levels A/B where common-cause analysis is expected.- Severity mapped without the FHA-to-PSSA-to-SSA chain.## Behavior contract (gate 3)The logic is exercised by the gate 3 contract test:scripts/test_fta_fmea.py against scripts/fta_fmea_logic.py (stdlibunittest, offline). Run:python3 scripts/test_fta_fmea.py## Compliance- Standards referenced, not reproduced: ARP4761A / ARP4754A text is proprietary (SAE); summary-only per standards-map.yaml and brief 06.- Revision note: ARP4754B (2023) supersedes ARP4754A; this skill keys to ARP4754A as the certification-baseline revision (FAA AC 20-174 cites A); see standards-map.yaml arp4754a.revision_decision.- compliance: STANDARDS-REF, gated: false.

Frequently asked questions