Maintenance is essential to aviation safety, yet improper maintenance contributes to a significant proportion of aviation accidents and incidents. This is because a small percentage of maintenance tasks are performed incorrectly or are omitted due to human error. Examples include parts installed incorrectly, missing parts, and the omission of necessary checks. While precise statistics are unavailable, it is likely that the great majority of maintenance errors are inconsequential, however, a small proportion present significant safety threats. In comparison to many other threats to aviation safety, the mistakes of maintenance personnel can be more difficult to detect, and have the potential to remain latent, affecting the safe operation of aircraft for longer periods of time.

While acknowledging that maintenance personnel are responsible for their actions, it must also be recognised that, in many cases, the errors of maintenance technicians are the visible manifestation of problems with roots deep in the organisation. A careful examination of each error, combined with a preparedness to inquire into why the error occurred, can help to identify underlying organisational problems. Effective countermeasures to maintenance error require a systemic approach, not only towards issues at the level of the technician and their work environment, but also to organisational factors such as procedures, task scheduling and training. Some countermeasures to the threat of maintenance error are directed at reducing the probability of error through improvements to training, equipment, the work environment and other conditions. A second, complementary, approach is to acknowledge that despite the best efforts, it is not possible to eliminate all maintenance errors, and countermeasures must be put in place to make systems more resilient to those residual maintenance errors that are not prevented.

Aviation organisations are increasingly introducing safety management systems (SMS) that go beyond legal compliance with rules and regulations, and instead emphasise continual improvement through the identification of hazards and the management of risk. The activities involved in managing the risk of maintenance error can be appropriately included within the SMS approach. Key activities include internal incident reporting and investigation systems, human factors awareness for maintenance personnel, and the continual identification and treatment of uncontrolled risks.

On 20 February 2009, this report was updated to include a list of resources and further reading on page 34.

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Alan Hobbs Ph.D.
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