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Introduction to Threat & Error Mgmt

by Darren Smith, CFII/MEI
General Aviation Human Factors, May, 2007

Let’s talk about Threat & Error Management (TEM) in depth. TEM is a conceptual model to help you understand the relationship between safety, human performance, and flight operations.

The focus is on Human Performance and System Performance. Human Performance is important because pilots under stress or task saturated (high threat level) do not perform at their best. We know this from the Yerkes-Dodson curve (see graphic below to the right). At a given level of stress, you’ll get a level of performance. There’s a breaking point, however, where further increasing stress affects human performance.

Threat & Error Management is an important conceptual framework because:

it can be used to describe cause & effect relationships,
it can be used to analyze failures of the system (accidents),
it can be used to alter and improve pilot training,
it can be used to predict human performance,
it can be used as an audit tool in flight operations, and
it can be used as a reporting tool when errors have occurred.

The three components of TEM are: threats, errors, and undesired aircraft states. In it’s simplest form, it describes a relationship where “A” leads to “B” which leads to “C”.

Think of the TEM model (depicted to the right) as a funnel. Whatever we allow to be poured into the top will get to the bottom if we don’t do something to resist the flow. If you avoid the threat, it usually doesn't occur. In other words, the threat doesn't even get into the funnel. Your avoidance activities will go a long way to minimizing a threat but if it does occur, it means easier threat management.

This means we can spend our time resisting threats or we can spend our time resisting the errors. Because of the cause & effect relationship between threat & error, we can consider that resisting threats is managing the future while resisting error is managing the past. In our flight operations, we always have a choice: proactive or reactive. Proactive increases our margin of safety while reactive consumes our margin of safety.

Some threats can be anticipated. Weather briefings, security briefings, quality of VHF / HF communications with ATC, cockpit workload. Preparing for the most conservative outcome is a way of managing and anticipating threats.

Some threats can’t be anticipated. Missing radio calls, unforecast weather, last minute runway changes, traffic flow restrictions, and other such gotchas. There are some real challenges in today’s aviation system and these complexities increase your workload as a pilot. Your deployment of TEM Countermeasures will increase your margin of safety regardless of whether the threat was anticipated or unanticipated.

The key thing to remember is that the threats are there and you aren’t likely to avoid them. Threats are unavoidable components of our complex operating environment. Managing these threats, or resisting threats is a way to mitigate the consequence. Fail to manage the threat, error is the result. When you’re managing and responding to errors, you’ll completely forget about new incoming threats. This nasty scenario sets you up for an undesired aircraft state because as threats stack up, more errors occur and there is a higher chance one of those errors is going to slip by you. Mismanaged threats lead to flight crew errors.

There are always exceptions to the rules. There are times when threats can lead directly to undesired aircraft states without the flight crew ever making an error. There are also occasions when flight crews can make errors when no threats are known to exist. Both scenarios could present flight crews with no conceivable way to manage the undesired aircraft state or the threat. Building predictability between flight crew members (pilot monitoring) and TEM Countermeasures offer a robust toolkit for mitigating these potentials.

In the next article, I’ll define Errors and provide examples & case study information to help you identify and manage Errors.

NEXT: Error Management>>

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Introduction to Threat & Error Mgmt

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