TABLE OF CONTENTS When an investigator or investigation team begins an analysis, the analyst uses a causal factor chart or fault tree to organize and analyze the data. A CF chart is simply a sequence diagram that allows investigators to graphically depict the mishap from beginning to end. The CF charting technique was originally developed by Ludwig Benner and his colleagues at the U.S. National Transportation Safety Board for use as an analytical tool in accident investigations. The tool is designed to help investigators chronologically describe the events leading up to an unwanted occurrence and the conditions surrounding these events.
Fault trees are a structured process for postulating ways the system could fail. The tree is developed only in enough detail to understand how the system failed.
Benner (1975) suggests that an accident involves a sequence of events (i.e., happenings) that occur during the course of good-intentioned work activity but that culminate in unintentional personnel injury or damage to a system. Experience has shown that incidents develop from clearly defined sequences of events that involve performance errors, changes, oversights, and omissions. The event investigator needs to identify and document not only these negative events, but also the relevant conditions and nonhazardous events related to the incident sequence. CF charts and fault trees are excellent vehicles for accomplishing this purpose.
The principles of CF charting are quite basic. Figure 3-1 presents a sample CF chart, and Table 3-1 provides definitions of the CF chart elements. Notice that...
