Threat and Error Management Model

Video embedded from YouTube on 16 August 2012

TEM Model


The Threat and Error Management (TEM) model is a conceptual framework. It was developed to help understand, and explain, the interaction between safety and human performance, within an operational context. It does this by mapping the inter-relationship between the parts within the safety system. The model captures aspects of these relationships that explain both human and system performance from a safety perspective. This model is used extensively to support safety management systems (SMS) such as Crew Resource Management (CRM) training and as a diagnostic application in Line Operations Safety Audits.
Although most of the discussion in this document uses aviation examples, the TEM Model explains relationships that are present in any complex organizational domain. (i.e. in medicine or nuclear power generation) (LOSA) and Normal Operations Safety Surveys (NOSS) (Maurino, 2005[1]; Helmreich, 1998[2]; ICAO, 2005[3]).

Historical Overview

“Errare humanum est”, a characteristic of the human species, and one that, as its Latin origin suggests, predates modern aviation. “To err is Human”, defines human fallibility and a dilemma that has confronted the aviation industry since its earliest days. As long as humans remain a functional component in any system there will always be errors, a fact that is of heightened concern within the complex operational environment of modern aviation where errors can have catastrophic results. Human Factors specialists acknowledge that errors do not occur in isolation, (i.e. confined to pilot error) but are generally the result of failures at a systemic level (Reason, 1997[4]).
By developing a better understanding of the processes which lead to the commission of errors and identifying contextual aspects in which they occur the industry has been able to design strategies that manage errors more effectively (Helmreich, 1998[2]).
Developed by the Human Factors Research Project of the University of Texas and Delta Airlines, the Threat and Error Management (TEM) Model provides a framework that recognizes the influence the operational context has in determining human performance (ICAO, 2005[3]).

Explanation of the TEM Model

TEM Model (Adapted by David Rae from TEM Model used in Helmreich & Musson, (2000[5]).

The TEM Model proposes an error management process that is influenced by two factors:

1. Threats - influences that are beyond the direct control of the people performing the work tasks and

2. Threat Management strategies and countermeasures - The actions of those performing operational tasks used to manage safety.

Threats are events or conditions that exist within the operational environment and attack the safety performance of the crew.

The two forms of threat described in the model are:

(a) Latent Threat – Not obvious to the flight crew and generally hidden within the system.

Latent Threat (examples)
Professional Culture - Risk taking culture and macho attitudes i.e. traditional pilot from the early barnstorming days of aviation
Organizational Culture - Safety rules and operating procedures not considered important
National Culture - Do not question the person in authority i.e. the captain is always right, even when he is wrong
Vague Policies - Do not clearly describe what actions are required and when. i.e. previous accidents caused through unclear ground de-icing policies

(b) - Overt Threats – Are present on the day and are either anticipated or unexpected by the crew.

Overt Threat (examples)
Environmental - Anticipated threat (Bad weather or a congested airport i.e the crew can plan how it will be managed)
Environmental - Unanticipated (Mechanical failure i.e. the crew are required to use skill and training to manage the threat)
Team or Crew - Lack of familiarity with SOP's
Organizational - Last minute change to schedule i.e. shortened turn-around time.

(Maurino, 2005[1])

Threat Management strategies and countermeasures intervene between the threats (described above) and the work tasks, they are best described as the safety tools that exist within the system. They represent aspects of human behaviour (i.e. personal strategies and tactics such as vigilence, anticipation and responses) and those intrinsic to the system (i.e. aircraft warning systems or procedures) that collectively support the management of threats. (Helmreich & Musson, 2000[5]).

From an error management perspective (i.e. the pilots actions) the TEM Model has three basic components that are linked to safe flight ; threats, errors and undesired aircraft states. Each of these components require management by the flight crew if they are to maintain safety margins during operations. (i.e. mis-managed threats, induce errors and undesired aircraft states)
Throughout the error management process threats remain capable of attacking the safety of the system. (i.e. An incorrect response by the crew to an error or threat could worsen the situation)(Helmreich, Klinect, & Wilhelm, 1999[6]).

The error management process has three forms of response by the crew:
1. "Trap the error": it is detected and managed before it becomes consequential.
2. "Exacerbate": it is detected but the crew’s action or inaction leads to a negative outcome.
3. "Fail to respond": the crew fails to react to the error either because it is undetected or ignored.
(Helmreich, Klinect, & Wilhelm, 1999[6]).

1. Maurino, D. (2005). THREAT AND ERROR MANAGEMENT (TEM). Canadian Aviation Safety Seminar (CASS)
Vancouver, BC, 18-20 April 2005. Retrieved August 15th from
2. Helmreich, R.L. (1998). Error management as organisational strategy. In Proceedings of the IATA Human Factors Seminar (pp. 1-7). Bangkok, Thailand, April 20-22, 1998. Retrieved August 15th from
3. ICAO. (2005). Threat and Error Management (TEM) in Air Traffic Control. Retrieved August 17th from
4. Reason, J. (1997). Managing the Risks of Organizational Accidents. Aldershot, UK: Ashgate.
5. Helmreich, R.L., & Musson, D.M. (2000). The University of Texas Threat and Error Model. British Medical Journal web site. (UTHFRP Pub 248) Retrieved August 17th from
6. Helmreich, R.L., Klinect, J.R., & Wilhelm, J.A. (1999). The Line Operations Safety Audit (LOSA)
Observer’s Manual, Version 7.0. Austin, TX: University of Texas Aerospace Crew Research Project. (591.doc) Retrieved August 17th from Report 99-04 October 1, 1999 : CASA Threat & Error Management. Retrieved from Youtube on 16 August 2012.

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TEM Flight Deck Application
As a frontline tool for use in complex systems by operators such as Flight Crew or ATC (Air Traffic Control) the TEM Model provides a basis for identifying and managing threats more effectively

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