IEC 61025 · ISO 26262 · ARP4761

Fault tree analysis that meets the standards you're audited against.

A professional-grade FTA workspace for safety engineers, reliability teams, and compliance-driven industries — org-scoped, audit-logged, and standards-native, without five-figure desktop licences or their limitations.

Sign up free → Talk to us about Enterprise
Free Community tier · no credit card · your workspace is private to your organisation.
Simple fault tree diagram TOP EVENT System failure AND BE-01 Sensor fail BE-02 Relay stuck
The tool

A real engineering workspace, in a browser tab.

Every gate type, every export format, every analysis method engineers actually need for audit-grade fault tree work — without installing a thing.

The FTA Studio editor with the aviation loss-of-hydraulic-power fault tree laid out on the canvas, the project navigator on the left and the analysis panel on the right showing Q(top) = 2.898e-3, importance measures and 16 minimal cut sets.
Monte Carlo panel after 100,000 runs: simulated Q(top) 2.960e-3 against an analytic 2.898e-3, a 95% confidence interval and a convergence trace settling onto the analytic value.
MONTE CARLO CONVERGENCE
Analysis panel: Q(top), the exact inclusion–exclusion method, Birnbaum, Fussell-Vesely, RAW and RRW importance measures per basic event, and the 16 minimal cut sets listed in order.
MINIMAL CUT SETS
The Export menu: diagram export, full HTML report, print to PDF, cut-set / node-inventory / FMEA CSVs, IEC 61025 JSON, and server-signed verifiable IEC 61025 JSON.
IEC 61025 EXPORT
Capabilities

Everything you need for IEC 61025 analysis.

From deterministic minimal cut sets to uncertainty-aware Monte Carlo — the full analytical stack, not a stripped-down subset.

Analysis engine

MOCUS minimal cut sets

Deterministic minimal cut set generation with no simulation variance. Handles AND, OR, Voting, Inhibit and PAND gates under IEC 61025 semantics, with exact truth-table analysis of non-coherent XOR, NAND, NOR and NOT logic. See how FTA Studio computes →

Importance measures

Birnbaum, Fussell-Vesely, RAW, RRW

Quantify which basic events drive top-event probability. All four standard measures computed per event, sortable, exportable.

Uncertainty

Monte Carlo simulation

xoshiro128** PRNG, chunked async execution that won't freeze your tab, live convergence plots, and sensitivity analysis on every basic event.

Interchange

IEC 61025-compliant exports

SVG, PDF, RTF, PNG, JPEG, and portable JSON for round-tripping between tools. Exact geometry constants, not pixel estimates.

Multi-page

Transfer gates across diagram pages

Handle trees that don't fit on one sheet without losing coordinates. Per-page position isolation means subtree layouts survive every render cycle.

Probability models

Exponential, Weibull, constant, λ×FH

Pick the probability model that matches your data, per basic event. Use constant failure rates, exponential with mission time, Weibull with shape/scale, or λ×flight-hours.

Examples

Start from a working template.

Eight industry-grade fault trees with calibrated probability data. Open one in a click — free to start.

Aviation · ARP4761 DAL-A

Total Loss of Aircraft Hydraulic Power

Triple-redundant systems A/B + RAT backup. 13 nodes · 25,000 hr mission.

Open in Studio → Automotive · ISO 26262 ASIL-B

AEB System Fails to Activate

Sensors, ADAS processing, actuation, and redundant power paths. 16 nodes.

Open in Studio → Rail · EN 50126 SIL 4

Signal Passed at Danger (SPAD)

Signalling failure, ATP failure, and driver-error pathway. 15 nodes.

Open in Studio →
See all 8 templates →
Written against
IEC 61025:2006 IEC 61508 ISO 26262 ARP4761 EN 50126 MIL-STD-882E
Positioning

Between heavyweight and toy.

Legacy desktop suites cost a fortune and lock you into Windows. Open-source tools stop short of the analysis rigour regulators expect. FTA Studio sits precisely in the gap.

Legacy desktop

ReliaSoft, Isograph, Siemens

The incumbents.

  • Five-figure annual licences
  • Windows desktop only
  • Heavyweight install and IT overhead
  • Vendor lock-in on file formats
The middle path

FTA Studio

Professional tool, modern delivery.

  • Free Community tier, forever
  • Runs in any modern browser
  • IEC 61025 JSON interchange
  • $99 / seat / year Professional
Open source

Scram, OpenFTA, others

The free alternatives.

  • Limited analysis coverage
  • Sparse importance-measure support
  • Thin documentation
  • DIY compliance story
Security by architecture

Your trees stay yours — isolated, audited, and verifiable.

For CUI-sensitive work and any organisation that treats reliability data as confidential IP — every project and tree lives in your organisation's isolated workspace, reachable only by the members you invite. Even FTA Studio's platform operators cannot read your tree contents.

Read the full privacy policy →
  • Org-scoped isolation — every project, tree and event library is partitioned to your organisation.
  • Operators can't read your content — the platform-admin surface is metadata-only, and every admin action is audit-logged.
  • Full audit trail — every version save and workflow action is recorded with actor and timestamp.
  • Signed, independently-verifiable IEC exports (Enterprise), plus a self-hosted option for air-gapped environments.
FAQ

Questions, answered.

The quick version. For anything else, email support@ftastudio.app.

Is Community really free?
Yes. Full IEC 61025 analysis, MOCUS minimal cut sets, importance measures, every export format, and multi-page diagrams. Forever. No trial, no expiry.
What do the paid tiers add?
The full analysis suite — FMEA, ETA, Monte Carlo, analytics and the approval workflow — is free in Community, within its 3-project / 10-tree / 3-member limits. Professional ($99/seat/year) lifts those limits and adds server-side high-iteration Monte Carlo; Enterprise adds signed, verifiable IEC exports, self-hosting and priority support. See the pricing page for the full comparison.
Who can access my fault trees?
Your trees live in your organisation's isolated workspace, visible only to the members you invite. FTA Studio's platform operators cannot read your tree contents — the admin surface is metadata-only. Every read and change is audit-logged, and Enterprise exports can be cryptographically signed for independent verification.
Does this comply with IEC 61025?
FTA Studio implements IEC 61025:2006 symbols and geometry exactly, with JSON interchange. Compliance of your analysis is your responsibility; the tool gives you the vocabulary to produce compliant outputs.
Which browsers are supported?
Current Chrome, Edge, Firefox, and Safari. No Internet Explorer. Not recommended on mobile browsers — the UI needs a real screen for production work.
Do I need an internet connection?
Yes — FTA Studio is a cloud workspace, so it needs a connection. For air-gapped or on-premise requirements, Enterprise offers a self-hosted deployment.
Can I self-host?
Enterprise customers in regulated environments: yes — talk to us. Air-gapped deployment with customer-held keys is on the roadmap.
How do I get support?
Email support@ftastudio.app. Enterprise customers get priority response.
I used FTA Studio Classic — how do I move my trees across?
Open ftastudio.app/export-my-data in the browser where you used Classic to download your projects as a file, then sign in at app.ftastudio.app and choose Import from Classic on your dashboard. Nothing is lost — the download stays on your computer, so you can bring trees over whenever you're ready.

Start in 10 seconds. Or talk to us first.

Community is free. Enterprise is a conversation.

Sign up free → Talk to us about Enterprise
$0 Community · $99/seat/year Professional · Enterprise custom · No credit card