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Threat and Error Management (TEM): A Critical Aviation Safety DisciplinePosted 3/5/2015

The widely employed discipline of Threat and Error Management (TEM) got its start in 1994, having evolved from an observation form designed by the University of Texas Human Factors group and Delta Airlines. Observation forms, as many ought to recall, were used by Line Operations Safety Audit (LOSA) observers, who rode in plane cockpits to monitor crewmembers’ flight performance. The forms were originally designed to evaluate Crew Resource Management (CRM) behaviors, but soon expanded to include error and the management of error. The researchers eventually went even further, however, to include the concept of threat and error management in observation forms.

TEM Explained

Following is a scenario to help explain the TEM concept:

An aircraft was level at FL240, and the crew was distracted due to a call from air traffic control (ATC). The crew didn’t begin their descent at the planned top-of-descent point. After recognizing their situation, the crewmembers increased their descent rate in an attempt to join profile and meet crossing restriction altitude of 15000 at ABC. (ABC, for the uninitiated, is a waypoint or “fix” along the flight route.) Instead, the crew crossed ABC at 15400—400 feet above the crossing altitude.

So, the threat can be singled out as the distraction that drew the crew away from their focus. The error, then, was over-flying the top-of-descent, and the undesired aircraft state was crossing the fix 400 feet high. Importantly:

+ Identifying threats enables the crew to anticipate and prepare for them. Anticipated threats are much less likely to result in error.

+ Identifying/recognizing errors allows the crew to correct (or repair) the error. The sooner an error is identified, the sooner that error can be repaired; thereby avoiding an undesired aircraft state (i.e., altitude deviation).

CRM and TEM work hand-in-hand. Good CRM skills help to identify and manage threats and errors.

A TEM-based Line Operations Safety Assessment

In 1996, the University of Texas and Continental Airlines conducted the first full TEM-based Line Operations Safety Assessment (LOSA). Among many other benefits, the data from the LOSA identified the most frequent threats—and also identified the threats that were commonly mismanaged, which led to errors. The LOSA data also identified the most common, as well as the most problematic, errors.

I highly recommend reading an excellent paper written about that groundbreaking LOSA, by Ashleigh Merrit, Ph.D. and James Klinect, Ph.D. It’s entitled:

Defensive Flying for Pilots: An Introduction to Threat and Error Management

The paper describes the origin and development of TEM, and the authors share some of the results of the LOSA observations, which, today, have become an important safety tool for all operators. It’s good to remember that, although one operation is never identical to another, many of the threats and errors are recurrent, and common to most operators.