Documenting a root cause analysis investigation in aviation maintenance should not mean wrestling with blank Word documents, disconnected spreadsheets, or forms that were never designed for the job. Yet that is exactly what most Part-145 and Part-CAMO organisations still do — and the result is inconsistent investigations, CAPA that cannot be traced to root causes, and findings that fail authority inspection.
The Aviathrust Root Cause Analysis Toolbox was built to solve this problem. It is a free, browser-based digital tool that supports the complete investigation lifecycle — from event recording through structured RCA using the 5 Whys, Ishikawa Fishbone, Boeing MEDA and Boeing REDA, all the way to CAPA formulation and professional report generation.
This guide walks you through every feature of the toolbox so you can start using it immediately in your organisation.
What the Toolbox Does
The Aviathrust RCA Toolbox is a single-file HTML application that runs entirely in your web browser. It requires no installation, no server connection for core functionality, and no account. All investigation data is stored locally in your browser's localStorage and is never transmitted to any server.
The toolbox supports: creating and managing multiple concurrent investigations, 5 Whys analysis with the Management Control Test at each level, Ishikawa (Fishbone) diagrams with the 6M framework and inline 5-Why drill-downs on prioritised causes, the full Boeing MEDA Results Form (Revision N, 10 February 2022) across all 6 sections, the full Boeing REDA Results Form (Revision J, 4 March 2022) across all 6 sections, a CAPA plan with root cause traceability, and a consolidated investigation report with export to JSON, PDF, and Word (.docx).
System requirements: Any modern browser (Chrome, Firefox, Edge, Safari). An internet connection is only needed for the Word export feature — everything else works fully offline. Recommended screen resolution is 1280×800 or higher.
Getting Started — Interface Overview
When you first open the toolbox, you will be presented with a legal disclaimer. Click "I Accept" to proceed — this acceptance is remembered by your browser and will not appear again unless you clear your browser data.
The interface has four main areas. The header bar at the top contains the application title and four action buttons: Light/Dark theme toggle, Load (to import a saved JSON file), Save (to export the current investigation), and Report (to switch to the report view). The sidebar on the left lists all investigations in memory — click any investigation to select it, and use the "+ New Investigation" button at the bottom to create a new one. The tab bar across the top of the main content area gives you access to six functional areas: Info, 5 Whys, Ishikawa, MEDA, REDA, and Report. Finally, the status bar at the bottom confirms auto-save timestamps.
Step 1 — Create an Investigation and Record the Event Details
Click the "+ New Investigation" button in the sidebar. The toolbox generates an investigation with an auto-assigned reference number (e.g., NCR-2026-001), which you can change to match your organisation's numbering convention.
The Info tab opens automatically. Fill in the investigation header: your organisation's NCR reference, the Part-145 or Part-CAMO organisation name, the date of the event and investigation, aircraft type and registration, NCR owner, and the investigation team members.
Three fields deserve particular attention. Finding Source is a dropdown that maps to the five EASA trigger situations — Authority Audit, Internal Audit, MOR, Voluntary Report, or SMS Trend. Classification captures whether this is a Level 1 (major), Level 2 (minor), or Observation. And the Event Description is a free-text narrative of what happened — this text automatically populates the problem statement in the 5 Whys tab and the effect statement in the Ishikawa tab, saving you from re-typing.
At the bottom of the Info tab, quick-access buttons link directly to the 5 Whys, Ishikawa, MEDA, and REDA tabs so you can move straight into the analysis.
Step 2 — Choose Your RCA Method and Conduct the Analysis
The toolbox supports four investigation methods. You may use one or combine several depending on the complexity of the event.
The 5 Whys — For Linear Cause Chains
The 5 Whys tab provides a structured, linear cause-chain analysis. The problem statement auto-populates from your event description — you can refine it to be more specific.
Click "+ Add Why" to add each step to the chain. Each step has three fields: the "Why?" question, "Answer + Evidence" for your response, and "Evidence Ref" for the document or interview reference that supports the answer. Steps appear in a vertical timeline with numbered blue circles.
What makes this tool different from a blank form is the Management Control Test (MCT) built into every step. Below each Why, three checkboxes ask: Is the cause identifiable (can you specifically name and describe it)? Is it controllable (within management's ability to change)? Is it preventable (if fixed, will it definitively prevent recurrence)?
When all three are ticked, the step turns green, the numbered circle changes to "RC" (Root Cause), and a green border with "ROOT CAUSE confirmed" appears. This is your stopping criterion — not a fixed number of Whys. You might reach root cause at the 3rd Why, or you might need 7.
The Ishikawa Fishbone — For Complex Multi-Factor Events
The Ishikawa tab is built for events where multiple parallel factors contributed to the failure. An interactive SVG fishbone diagram renders automatically at the top of the tab, displaying the effect on the right and six colour-coded bone branches: Man (purple), Machine (amber), Method (blue), Material (teal), Environment (green), and Management (red).
Below the diagram, the six categories appear as cards in a 3-column grid. For each category, type a contributing cause in the input field, press Enter, and it appears both in the card and as a new branch on the fishbone. Add an evidence reference for each cause.
To prioritise a cause, tick its checkbox. The branch changes from dashed to solid with a gold circle, and a 5-Why drill panel appears directly below the cause. This is the combined Ishikawa + 5 Whys method — the most powerful RCA approach for complex aviation events. Map all causes across all six categories first, prioritise the key ones with evidence, then drill deeper on each prioritised cause until you reach a root cause that passes the Management Control Test.
The fishbone diagram updates in real-time as you add, remove, or prioritise causes, and automatically adapts to dark and light themes.
Boeing MEDA — For Maintenance Error Investigation
The MEDA tab provides the complete Boeing MEDA Results Form (Revision N, 10 February 2022) in a fully digital, fillable format. It is organised across six sections with a navigation bar at the top, plus Previous and Next buttons for sequential movement.
- Section I (General Information) captures all administrative data — station, aircraft, engine type, registration, ATA number, shift details, and type of maintenance.
- Section II (Event) covers operations process events and other event types through checkboxes.
- Section III (Maintenance System Failure) provides 9 failure categories with detailed sub-items — from installation failures through FOD and personal injury.
- Section IV (Chronological Summary) captures the event timeline narrative.
- Section V (Contributing Factors Checklist) is the RCA core — 10 categories (A through J) covering Information, Equipment/Tools, Aircraft Design, Job/Task, Knowledge/Skills, Individual Factors, Environment, Organisational, Leadership, and Communication, each with individual factor checkboxes, a description field, and a recommendations field.
- Section VI (Summary of Recommendations) consolidates everything — and the "Collect all recommendations from Contributing Factors" button automatically gathers every recommendation from Section V, organised by category.
Boeing REDA — For Ramp and Ground Handling Events
The REDA tab mirrors the MEDA structure but with ramp-specific content — the full Boeing REDA Results Form (Revision J, 4 March 2022). It covers aircraft damage, equipment damage, operational process events, personal injury, environmental impact, and weight and balance incidents through six sections with the same navigation approach. Section IV provides eleven contributing factor categories, and Section V captures failure prevention strategies with an auto-populate function for recommendations.
Step 3 — Formulate CAPA on the Report Tab
Switch to the Report tab — this consolidates all investigation data into a single view and is the primary output for review, approval, and filing.
The report displays, in order: the investigation header metadata, event description, Ishikawa analysis with the fishbone diagram and cause table (if used), the full 5 Whys chain with MCT results (if used), MEDA investigation summary with separate Root Cause Analysis and CAPA sections (if MEDA was used), REDA investigation summary (if REDA was used), confirmed root cause statements from all methods, the CAPA plan, and the sign-off section.
The CAPA Plan grid at the bottom is where you define your corrective and preventive actions. Click "+ Add CAPA" to add rows. Each row captures: the root cause reference (e.g., RC-A, RC-B), the specific CAPA description, the responsible owner, priority (Critical, High, or Medium), target completion date, and how you will verify the CAPA was effective. Every CAPA should trace directly to a confirmed root cause — this traceability is exactly what authority inspectors look for.
The Sign-Off section captures the investigator, QA reviewer, and accountable manager notification date.
Step 4 — Export Your Investigation
Three export options are available at the top of the Report tab.
Save (.json) downloads the complete investigation data as a portable JSON file. Use this for backup, sharing between computers, or loading into another instance of the toolbox. This is your primary data record — treat it as such.
Print / PDF opens your browser's print dialog. Select "Save as PDF" as the destination. The tool automatically switches to light theme for printing to ensure the fishbone diagram text is readable on white paper, then restores your chosen theme afterwards. For best results, set margins to "None" or "Minimum" and enable "Background graphics" in the print dialog.
Export Word (.docx) generates a professional Microsoft Word document with a cover page, colour-coded Ishikawa cause table, 5 Whys chain with MCT confirmation markers, full MEDA and REDA forms with checkbox symbols (☑/☐), root cause statement blocks, a 6-column CAPA plan table, the sign-off section, and running headers and footers on every page. This is the format most suited for document-controlled distribution and authority submission. Note that this feature requires an internet connection as the document generation library loads from a CDN.
Saving, Loading, and Data Management
The toolbox auto-saves every change to your browser's localStorage. This data persists between sessions — you can close the browser, reopen the tool tomorrow, and your investigations are exactly where you left them.
However, localStorage is a convenience cache, not archival storage. Your data will be lost if you clear your browser data, uninstall or reset your browser, or replace your device. The best practice is to click Save after every investigation session to export a JSON backup file.
To load a saved investigation, click the Load button in the header bar and select a JSON file. The toolbox accepts both single-investigation files and array files containing multiple investigations (such as workshop case bundles used in training). When loading an array, all investigations are imported at once. If a loaded investigation has the same ID as an existing one, the existing version is replaced.
To delete an investigation, click the red Delete button at the bottom of the Info tab. A confirmation dialog appears before permanent removal.
Recommended Investigation Workflow
For the best results, follow this sequence:
Start on the Info tab — enter all header information and write a thorough event description. This description feeds into your 5 Whys problem statement and Ishikawa effect statement automatically.
Choose your RCA method(s) — the 5 Whys for linear cause chains with a clear single thread, the Ishikawa for multi-factor events where parallel causes need mapping, MEDA for maintenance-related errors, and REDA for ramp and ground handling events. You can use multiple methods on the same investigation.
Complete the analysis — ensure every conclusion is backed by evidence. Every Why answer and every Ishikawa cause must reference an interview, a document, or a physical inspection.
Formulate CAPA actions on the Report tab — each tied to a specific confirmed root cause. If your CAPA says "retrain the engineer" without addressing the systemic gap that made the error possible, you have not finished the job.
Complete the Sign-Off section and export — save JSON for records, print PDF for filing, export Word for document-controlled distribution and authority submission.
Common Mistakes to Avoid
- Stopping too early. If your root cause is "the technician made an error," you have not gone deep enough. The Management Control Test is built into the tool for exactly this reason — use it at every level of the 5 Whys.
- No evidence references. A root cause analysis without evidence references is an opinion document, not an investigation. The toolbox provides evidence fields at every step — fill them in.
- Retraining as standalone CAPA. Retraining is almost never an effective corrective action on its own. Fix the system, the procedure, the process. The authority inspector's first question will always be: "What root cause does this action address?"
- Not saving regularly. Browser data can be lost. Export your JSON after every session. This is your primary investigation record.
Troubleshooting
If the tool shows a blank page, JavaScript may be disabled in your browser — enable it in settings. If the disclaimer keeps reappearing, your browser may be blocking localStorage — check privacy settings or try a different browser. If Word export fails, check your internet connection — the document generation library loads from a CDN, though all other features work offline. If data has disappeared, you may have cleared browser data — reload from your saved JSON file using the Load button. If the fishbone text is invisible, toggle the theme (Light/Dark) to force a re-render.
Start Your Next Investigation
The Aviathrust Root Cause Analysis Toolbox is free to use — open it in your browser and begin. No installation, no registration, no data leaving your machine. If you would like to contribute in its development and improvement you can find the source code on github on the following link: https://github.com/gspiteri1984/Root-Cause-Analysis-Tool.git
If you want to build your team's RCA capability alongside the tool, our Audit, Non-Conformity, Root Cause Analysis & CAPA training course teaches the investigation methodology behind every feature of the toolbox — including the 5 Whys, Ishikawa, MEDA, and the combined approach — through six realistic aviation maintenance case studies where participants use the toolbox hands-on during the workshop.
