It is important to understand the difference between intentional misconduct or wilful negligence versus unintentional error.

This guide is for the investigation of unintentional error.

This short video, produced by the Australian Transport Safety Bureau, explains why we need to investigate the human factors elements of an accident or incident.

Most occurrences involve human error at some point. Even highly trained and qualified people make errors. Errors are part of being human. This is why the aviation system, which is complex and dynamic, needs to be ‘error-tolerant’. This means the system must use technology, processes and procedures designed to trap errors before they progress too far. Safety investigation has played a significant role in ensuring that aviation has evolved into the very safe industry we’re now part of.

Whether aviation is your career or your hobby, everyone expects to come home safely. But sometimes things don’t go as planned and when that happens it’s usually because of unintentional error.  An error might be made by a pilot, a controller, or an engineer. But it might also be an error, made by someone less directly connected to the flight such as management, that sits, waiting for the right set of circumstances to combine to create an incident or accident. When something doesn’t go right, it’s a safety investigator’s role to understand what didn’t go right and why. 

When reacting to an occurrence, investigators need to avoid the tendency to focus only on the ‘sharp end’ where a pilot, air traffic controller, or engineer has made an error, without considering the ‘blunt end’. The blunt end is the organisational context, aircraft and equipment, and environmental influences surrounding the person, at the time, that may have created the circumstances for error. 

Have a look at the following diagram. It’s a simplified version of James Reason’s Swiss Cheese Model of accident causation. Each layer provides defences that can prevent an accident. But if there are holes in these layers of defence, and those holes line up one day, we have all the ingredients for an accident. 

James Reason's Swiss Cheese model

Swiss cheese model

A safety investigator’s job is to understand what the circumstances were that led to the error(s). They’ll need to investigate all these layers of defence to work out where those holes were. Effective safety recommendations or actions can only be implemented if all the holes are identified. If an investigator focuses only on the sharp end, they can easily miss meaningful, system-wide opportunities for safety improvement.


Perspective-taking for investigators

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