TEM (Threat and Error Management)

Threat and Error Management

Threat and Error Management (TEM) provides an important contribution to Aviation Safety.
It is a relatively new safety concept which addresses potential weaknesses in performance within the aviation environment, when threatened to external influences.
TEM has evolved from line orientated safety audits (LOSA) and is employed in most airlines today. The concept covers any factor that threatens the safe conduct of the flight.

There are three basic elements to TEM

  • Threats
  • Errors, and
  • Undesired aircraft states

(Video embedded from YouTube on 29 August 2012-)


Threats are defined as events or errors made by others, that occur beyond the influence of the flight crew, increase operational complexity, and which must be managed to maintain levels of safety.

These threats can be expected, unexpected and latent. In more cases latent threats can be very serious as they lay dormant for some time until something else occurs bringing this into light.

Threats can be categorized as organizational or environmental.
organizational threats include maintenance through to crew scheduling and dispatch error, while environmental threats such as weather, terrain and operational complexities can challenge a flight crew.

Managing threats

The first step in managing threats is to firstly identify the threat. Often mismanaged threats lead to errors which can in turn lead to undesirable aircraft states. Initial training covers looking for things that complicate the operation, eg complex airspace and arrival at an international airport compared with a simple airport. Later as the flight crew member gains experience it will become easier to identify what factors may be considered a threat. Experience in itself may also be a countermeasure although it can sometimes lead to complacency as a flight crew may have seen the situation before. Flight crew vigilance at all times is a key part of threat and error management.


Errors are defined as actions or inaction's by the crew that lead to deviations from organizational or flight crew intentions or expectations.
They can be induced by a threat as previously mentioned, or be spontaneous. More often they tend to be a link in a chain of errors.

There are three primary categories of Error in the TEM model

  1. Aircraft handling errors
  2. Procedural errors
  3. Communication errors

Threat and Error Mitigation

Part of ensuring that an undesired aircraft state does not occur is using pilot countermeasures. These include but are not limited to, checklists, briefings, SOP's and CRM. It is suggested that up to 70% of flight crew activities may be countermeasure related (Robson, 2008).
Whilst most countermeasures can be considered at crew level, some are considered hard resource countermeasures and a involve systemic based approach. These may be items such as stall warnings, ground proximity warning systems (GPWS) and airborne collision avoidance systems (ACAS).

Pilot intervention is key in ensuring an effective threat and error management system works. Rather than the pilot being thought of as the weakest link he could be seen as the strongest link that prevents the succession of events leading to an accident.

1. TEM Model - explains the relationships between safety and human performance in the work environment.
2. Flight Deck Applications - Practical application of TEM
3. Strategies and Countermeasures - the TEM processes used on the flight deck.
4. Crew Resource Management Training - Crew Resource Management Training

1. Robson, D. (2008). Human being pilot : Human factors for aviation professionals (1st ed.). Cheltenham, Australia: Aviation Theory Centre.

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