What is root cause analysis (RCA)?

Root cause analysis (RCA) is a structured way of finding out why something went wrong, so that you fix the real cause and stop the problem coming back.

Symptom versus root cause

A motor trips on overload. Resetting it fixes the symptom. Finding that the gearbox bearing ran dry because lubricator refills were never on the maintenance checklist finds the root cause. Only the second stops the next trip.

Common RCA methods

• 5 Whys: keep asking "why?" until you reach a cause you can control.
• Fishbone (Ishikawa) diagram: map possible causes in categories such as People, Method, Machine, Material, Measurement and Environment.
• Fault tree and 8D: more formal methods for complex or customer-driven investigations.

Basic steps

1. Describe the problem clearly: what, where, when and the impact.
2. Collect facts and evidence, not opinions.
3. Find the causes with a method such as 5 Whys or a fishbone.
4. Agree actions, each with an owner and a due date.
5. Check later that the problem has not returned.

RapidRCA follows these steps as the ROOTS™ method.

Common mistakes

• Stopping at "human error". Ask what in the procedure, design or system allowed the error.
• Guessing instead of checking. Every Why should be backed by evidence.
• Actions with no owner. An action nobody owns rarely happens.
• No follow-up. If you never check the fix worked, you do not know the problem is solved.