Failures

               Failures  - two types, depending on the immediacy of their consequences.                             Active failure is an error or a violation which has an immediate adverse effect. These errors are usually made by the front-line operator. A pilot raising the landing gear lever instead of the flap lever exemplifies this failure type.                                             Latent failure is a result of an action or decision made well before an accident, the consequences of which may remain dormant for a long time. Such failures usually originate at the decision-maker, regulator or line management levels; that is, with people far removed in time and space from the event. A decision to merge two companies without providing training to standardize aircraft maintenance and flight operations procedures illustrates the latent failure type. These failures can also be introduced at any level of the system by the human condition, for example, through poor motivation or fatigue.

 Latent failures, which originate from questionable decisions or incorrect actions, although not harmful if they occur individually, can interact to create “a window of opportunity” for a pilot, air traffic controller or mechanic to commit an active failure which breaches all the defences of the system and results in an accident. In such cases, the front-line operators become the inheritors of a system's defects because they are the ones dealing with a situation in which their actions, technical problems or adverse conditions will reveal the latent failures long embedded in a system. In a well-guarded system, latent and active failures will interact, but they will not often breach the defences. When the defences work, the result is an incident; when they do not, it is an accident  

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