Root Cause Analysis for Engineers
A practical guide to RCA methods, mistakes, and how to turn failure events into reliability improvement.
Executive summary
Root Cause Analysis is a structured way to understand why a failure happened and how to prevent recurrence.
The goal is not to blame people.
The goal is to improve the system.
What RCA should answer
A good RCA answers:
- What happened?
- When did it happen?
- What was the impact?
- What conditions existed before the event?
- What direct causes were found?
- What underlying causes allowed it?
- What actions will prevent recurrence?
- Stopping at operator error
- Writing vague actions
- No evidence collection
- No follow-up
- Confusing symptoms with causes
Common RCA methods
5 Whys
Ask why repeatedly until the underlying cause is clearer.
Fishbone diagram
Group possible causes into categories such as machine, method, material, manpower, measurement, and environment.
Fault tree analysis
Map logical paths that could lead to the failure.
Practical RCA workflow
1. Define the problem. 2. Collect evidence. 3. Build the timeline. 4. Identify direct causes. 5. Identify contributing factors. 6. Identify root causes. 7. Define corrective actions. 8. Assign owners and deadlines. 9. Verify effectiveness.
Common mistakes
Summary
RCA is useful only when it leads to better controls, better procedures, better maintenance, or better design.