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Threat and Error Management (TEM)

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Article Information
Category: Safety Management Safety Management
Content source: ICAO ICAO

Threat and Error Management (TEM)

Note: This article is based on the preliminary edition of Threat and Error Management (TEM) in Air Traffic Control (ICAO).

Introduction to TEM

Threat and Error Management (TEM) is an overarching safety concept regarding aviation operations and human performance. TEM is not a revolutionary concept, but one that has evolved gradually, as a consequence of the constant drive to improve the margins of safety in aviation operations through the practical integration of Human Factors knowledge.

TEM was developed as a product of collective aviation industry experience. Such experience fostered the recognition that past studies and, most importantly, operational consideration of human performance in aviation had largely overlooked the most important factor influencing human performance in dynamic work environments: the interaction between people and the operational context (i.e., organisational, regulatory and environmental factors) within which people discharged their operational duties.

TEM Background

The origin of TEM can be traced down to the origin of Line Operations Safety Audits (LOSA). A partnership between the University of Texas Human Factors Research Project (UT) and Delta Airlines in 1994 has developed a line audit methodology utilising jump-seat observations on scheduled flights. Both parties agreed that in order for the audit to be productive and show realistic and un-obscured results, confidentiality of the findings with no regulatory or organisational jeopardy to the flight crews should be guaranteed.

The initial observation forms of the audit were designed by the University of Texas researchers to evaluate Crew Resource Management (CRM) behaviour on the flight deck. The form was lately enhanced to address error and its management as well as type of error committed. This method enabled the observers to identify the origin of the error, the response to the error, was the error detected and by whom, together with the outcome of the error.

The first full scale TEM-based LOSA was conducted at Continental Airlines in 1996. Together with the original CRM indicators (leadership, communication, and monitoring/cross-checking) the new concept of TEM was used to identify most frequent threats. This method provided a clear picture of the most common errors and threats, both that were well managed and the more problematic and mismanaged.

The recognition of the influence of the operational context in human performance led to the conclusion that the study and consideration of human performance in aviation operations must not be an end in and on itself. With regard to the improvement of margins of safety in aviation operations, the study and consideration of human performance without context addresses only part of the larger issue. TEM therefore aims to provide a principled approach to the broad examination of the dynamic and challenging complexities of the operational context in human performance, for it is the influence of these complexities that generates the consequences that directly affect safety.

TEM framework

The TEM framework is a conceptual model that assists in understanding, from an operational perspective, the inter-relationship between safety and human performance in dynamic and challenging operational contexts.

The TEM framework focuses simultaneously on the operational context and the people discharging operational duties in such a context. The framework is descriptive and diagnostic of both human and system performance. It is descriptive because it captures human and system performance in the normal operational context, resulting in realistic descriptions. It is diagnostic because it allows quantifying the complexities of the operational context in relation to the description of human performance in that context, and vice-versa.

The TEM framework can be used in several ways. As a safety analysis tool, the framework can focus on a single event, as is the case with accident/incident analysis; or it can be used to understand systemic patterns within a large set of events, as is the case with operational audits. The TEM framework can be used to inform about licensing requirements, helping clarify human performance needs, strengths and vulnerabilities, thus allowing the definition of competencies from a broader safety management perspective. Subsequently the TEM framework can be a useful tool in On the-Job Training (OJT). The TEM framework can be used as guidance to inform about training requirements, helping an organisation improve the effectiveness of its training interventions, and consequently of its organisational safeguards. The TEM framework can be used to provide training to quality assurance specialists who are responsible for evaluating facility operations as part of certification.

Originally developed for flight deck operations, the TEM framework can nonetheless be used at different levels and sectors within an organisation, and across different organisations within the aviation industry. It is therefore important, when applying TEM, to keep the user's perspective in the forefront. Depending on "who" is using TEM (i.e. front-line personnel, middle management, senior management, flight operations, maintenance, air traffic control), slight adjustments to related definitions may be required.

The components of the TEM framework

There are three basic components in the TEM framework, from the perspective of their users they have slightly different definitions: threats, errors and undesired (aircraft) states. The framework proposes that threats and errors are part of everyday aviation operations that must be managed by the aviation professionals, since both threats and errors carry the potential to generate undesired states. The undesired states carry the potential for unsafe outcomes thus undesired state management is an essential component of the TEM framework, as important as threat and error management. Undesired state management largely represents the last opportunity to avoid an unsafe outcome and thus maintain safety margins in aviation operations.

  • Threats – generally defined as events or errors that occur beyond the influence of the line personnel, increase operational complexity, and which must be managed to maintain the margins of safety.
  • Errors – generally defined as actions or inactions by the line personnel that lead to deviations from organisational 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.
  • Undesired states – 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.

Note: “Line personnel” in the context above means an air traffic controllers or flight crew members.

Related Articles

For more details about specific TEM characteristics see TEM in Air Traffic Control and TEM in Flight Operations.

Further Reading


  • Threat and Error Management (TEM) in Air Traffic Control, Preliminary Edition 2005;
  • THREAT AND ERROR MANAGEMENT (TEM), Captain Dan Maurino, Coordinator, Flight Safety and Human Factors Programme – ICAO, Canadian Aviation Safety Seminar (CASS), Vancouver, Canada, 18-20 April 2005;


  • Defensive Flying for Pilots: An Introduction to Threat and Error Management, Ashleigh Merritt, Ph.D. & James Klinect, Ph.D., The University of Texas Human Factors Research Project, The LOSA Collaborative December 12, 2006.

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