ERRORS


Are generally defined as “actions or inactions by the line personnel that lead to deviations from organizational or operational intentions or expectations”. Unmanaged and/or mis-managed errors frequently lead to undesired states. Errors in the operational context thus tend to reduce the margins of safety and increase the probability of an undesirable event.


Errors can be spontaneous (i.e., without direct linkage to specific, obvious threats), linked to threats, or part of an error chain. Examples of errors would include the inability to maintain stabilized approach parameters, executing a wrong automation mode, failing to give a required callout, or misinterpreting an ATC clearance.


Error Management


Capturing how errors are managed is then as important, if not more, than detecting the prevalence of different types of error. Some errors are quickly detected and resolved, thus becoming operationally inconsequential, while others go undetected or are mismanaged. A mismanaged error is defined as an error that is linked to or induces an additional error leading to the error chain or undesired aircraft state.


The Error Chain


James Reason’s Model: The error chain hypothesis suggests that accidents occur when there is a whole system failure. Incidents occur when all individual prevention barriers’ weaknesses align, which allows the trajectory of an accident-path to pass through each of the prevention barriers, resulting in an unwanted incident or accident. There are both latent failures and active failures that contribute to unwanted outcomes. The barriers fall under the categories: organizational influence, supervisory influence, preconditional influence and unsafe acts. The first three barriers are considered latent, while unsafe acts are active failures.


The strategies for error management are the implementation of applicable CRM/TEM skills. These may include:


• Monitor/Cross-Check by maintaining awareness of the aircraft/cabin environment and crewmembers actions


• Workload management by ensuring tasks are properly prioritized and managed


Remember: Identify and Repair UNDESIRED [AIRCRAFT] STATES


Is generally defined as “operational conditions where an unintended situation results in a reduction in margins of safety”. Undesired states that result from ineffective threat and/or error management may lead to compromised situations and reduce margins of safety aviation operations. Often considered the last stage before an incident or accident.


Examples of Undesired Aircraft State


• Lining up for the incorrect runway during approach to landing • Exceeding ATC speed restrictions during an approach • Landing long on a short runway requiring maximum braking


Events such as equipment mal functions or ATC controller errors can also reduce margins of safety in flight operations, but these would be considered threats. Undesired states can be managed effectively, restoring margins of safety, or flight crew response(s) can induce an additional error, incident, or accident.


CRM 2, TEM, Fatigue 8


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