Root Cause AnalysisRCA

Root Cause Analysis is a structured method to find the underlying cause of a problem rather than its symptoms. Common methods are Five Whys (iterative questioning to push past the first answer), the Fishbone or Ishikawa diagram (cause categories such as people, process, equipment, materials, environment), Fault Tree Analysis, and the Apollo method. The output of an RCA is a cause chain, not a list of symptoms, and the chain is only useful if the corrective action it produces breaks the chain.

The discipline that makes an RCA honest is that it stops at a system cause, not a person cause. An RCA that ends at human error has stopped one step too early — human error is a symptom of a system that let the error happen and that did not catch it. The regulator expectation, and the ISO 9001 and 45001 expectation, is that an RCA traces from the incident back through the failed controls to the management-system gap that owned them. The test of a finished RCA is whether the CAPA it generates prevents the same incident on a different crew. See Five Whys, fishbone, and CAPA.