Threat and Error Management in Air Traffic Control

The Threat and Error Management (TEM) framework recognises that operational activities are a series of on-going threats, errors and undesired states that controllers must manage to maintain adequate safety margins. Threats are external events or errors outside the influence of the controller, but which require attention and management to ensure safety margins are maintained (ICAO, 2008; Maurino, 2005). Threats are everywhere (traffic, adverse weather, airport/airspace infrastructure, equipment, flightcrew, other controllers, etc.) and controllers must devote attention to managing them. The more complex, challenging, and/or distracting the environment is, the greater the controller’s workload.
Controller errors are defined as observed deviations from organisational expectations or controller intentions (ICAO, 2008). Errors can vary from minor deviations, such as not using a checklist, to something more severe, such as not coordinating an altitude change with other controllers. Regardless of cause or severity, the outcome of an error depends on whether the error is detected and managed before it leads to an unsafe outcome. This is why the foundation of TEM lies in understanding error management rather than solely focusing on the cause of the error.

The TEM framework has been widely deployed in aviation:
• ICAO has published a Circular on TEM in ATC.
• TEM was a central focus in the ICAO Human Factors Training Manual (ICAO Document 9683).
• TEM is the foundation of human factors training programs at several international and regional airlines including Air New Zealand, Alaska Airlines, Cathay Pacific, Continental, Delta, Qantas, and Singapore Airlines. Several ATC providers have also developing TEM training for air traffic controllers, such as Euro Control.
• TEM has been adopted as the framework for the classification and analysis of worldwide accidents and incidents by the IATA Classification Working Group.

NOSS Background

In the past, accident and incident investigation reports have been utilised to further the aviation industries understanding of safety. While rich in information, these reports only capture a single event, and are reactive by nature. Normal Operations Safety Survey (NOSS) is a methodology for capturing safety data during normal air traffic control (ATC) operations. The NOSS methodology is based on the TEM framework and is a safety management tool used to monitor safety during normal operations (ICAO, 2008). Monitoring safety in normal operations is an essential activity within the safety management systems of air traffic service (ATS) provider, and NOSS is proposed as a suitable way to do this.
NOSS is modelled on the Line Operation Safety Audit (LOSA) methodology, which was developed by The University of Texas Human Factors Research Project (UTHF) in consultation with several airlines. The LOSA methodology is recognised worldwide and is formally endorsed by ICAO, IATA, IFALPA, and ALPA. Over 30 airlines worldwide, including Air New Zealand, Mount Cook, QANTAS, Cathay Pacific, Singapore Airlines, Malaysian Airlines, Japan Airlines, China Airlines, and Emirates have deployed LOSA to inform their safety management systems.

As a result of the safety benefits that airlines have experienced from LOSA, ICAO formed a formal study group comprised of Air Navigation Service Providers and aviation safety experts from around the globe to develop a means to collect safety data during every-day air traffic operations. As members of the ICAO study group, the University of Texas partnered with several Air Navigation Service Providers – Airways New Zealand, Air Services Australia, and NAV CANADA - to conduct field trials of the NOSS methodology in 2005-2006. Since, its development, full-scale NOSS projects have been conducted in Canada, the United States, Australia, and New Zealand.

NOSS is an observational methodology. NOSS observers are selected from a group of operational controllers, who are then trained in both the TEM framework and the observational methodology. Observers are then assigned different sectors and times, during normal operations,to observe and code the operating environment as well as controller behaviour. Observers code the threats, errors and undesired states that they observe, as well as the controllers’ response, and the outcomes. Additionally, the observer will write a narrative that provides important contextual information. Data collected from all of the observations is collated into one database for analysis, the aim of which is to diagnose strengths and vulnerabilities in the Air Navigation Service Provider’s operations (ICAO, 2008).

NOSS has enabled Air Navigation Service Providers to monitor and diagnose normal operations, and develop proactive safety interventions. NOSS can assist these organisations in determining how close they are operating to the edge of the safety envelope, without breaching that envelope.

1.ICAO. (2008). Threat and Error Management (TEM) in Air Traffic Control.
Retrieved September 03rd from http://legacy.ICAO.int/ANB/safetymanagement/Circ_314-AN_178_INP_EN_EDENPROD_195309_V1[1].pdf
2. Maurino,D. (2005). THREAT AND ERROR MANAGEMENT (TEM).Canadian Aviation Safety Seminar (CASS) Vancouver, BC, 18-20 April 2005. Retrieved September 03rd fromhttp://www.skybrary.aero/bookshelf/books/515.pdf

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