The Human Factors and Analysis Classification System is designed to help define and
understand the concept of human error as it pertains to aviation accidents. The HFACS divides
human error into two main categories: violations and errors.
Define Human Error
The HFACS uses a “Swiss cheese” model when defining human error. The model is
comprised of four levels each creating more “holes” or opportunities for errors. The
classification process produces two main types of errors. Mistakes caused by a pilot or
crewmember not obeying the laws or guidelines put in place for safety purposes are called
violations. Errors, however, occur when a pilot or member of the crew make a mistake due to
lack of observation or other human deficiencies (Shappell, and Wiegmann, 2000).
Methods Used to Classify Human Error
Violations occur when a pilot or crewmember refuses to follow orders or
recommendations that were designed to keep the aircraft and its passenger’s safe during their
travels. Intentionally disregarding specific issues that could possibly lead to an aviation accident
can eventually turn into a criminal case, if passengers are harmed or property is destroyed.
Errors are mistakes that are made unintentionally without malice or forethought.
Misreading an instrument or gauge, misjudging distance due to limited visibility can be
classified as errors. Mistakes that are made as the result of human shortcomings are also
How HFACS Can Be Both Proactive and Reactive
The Swiss Cheese model used by HFACS works proactively by researching past
historical events in aviation history in an attempt to find possible trends. By identifying trends
and behaviors measures can be developed to prevent them from reoccurring. In reactive mode,
the HFACS helps to determine the cause of an accident. The information discovered during the
investigation will continue to create safety standards to prevent future accidents (“The HFACS,”
By using the HFACS, the aviation industry can define and monitor human error and its
effect on flights, as well as the possibility of accidents and crashes.
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