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No fix without the root cause
The five steps
CAPA stands for corrective and preventive action. The point of all five steps is prevention, so the same failure never happens again. Root cause is a requirement because nobody knows how to fix a problem without knowing what actually happened.
Required by law
The process is required by law in some fields. The FDA requires it in pharmaceuticals and medical devices, and the aerospace industry has regulations that require this type of process after a failure.
After Surfside
After the Surfside collapse, the findings led to changes in the condominium rules across Florida. Multiple other states, especially coastal ones, adopted them.
Why does the FDA insist on root causes?
A fix aimed at a symptom leaves the underlying cause in place, so the same defect can come back. In the United States, the FDA's quality system regulation for medical device makers requires procedures for corrective and preventive action. Inspectors review whether a company investigated the cause of problems and checked that its fix worked. Inadequate corrective and preventive action procedures have long been among the most frequently cited problems in FDA device inspections.
How do investigators find a root cause?
One common method is the five whys, developed by Sakichi Toyoda and used at Toyota: ask why a failure occurred, then ask why again of each answer, until the chain reaches a cause that can be fixed. Another is the fishbone diagram, created by Kaoru Ishikawa, which sorts possible causes into branches such as materials, methods, machines, and people. Aviation investigators also use fault trees, first developed at Bell Labs in the early 1960s for the Minuteman missile launch system.
How does aviation act on a known failure?
In the United States, the FAA issues airworthiness directives, which are legally enforceable orders to inspect, repair, or replace parts with a known unsafe condition. The directives apply to specific aircraft models, engines, or components. Operators must comply by a set deadline or the aircraft cannot lawfully fly.
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