NASA Procedures and Guidelines
This Document is Obsolete and Is No Longer Used. Check the NODIS Library to access the current version: http://nodis3.gsfc.nasa.gov
NPR 8621.1 Eff. Date: June 02, 2000 Cancellation Date: February 11, 2004	NASA Procedures and Guidelines for Mishap Reporting, Investigating, and Recordkeeping
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The purpose of events and causal factors diagramming is to reconstruct the event and develop root cause(s) associated with it. This is one of the most useful analytical tools available to the mishap investigator because it serves to organize thinking in a sequential manner, provide a visualization of the mishap flow, and provide a story line for the narrative description of the mishap.

1.2 Method

Event and causal factor charting utilizes a block diagram to depict cause and effect. This technique is most effective for solving complicated problems because it provides a means to organize the data, provides a concise summary of what is known and unknown about the event, and results in a detailed sequence of facts and activities. The first block on the chart is the primary effect. For each effect, there is a cause that becomes the effect in the next block to the right. In a block below each cause (effect) are two reasons that indicate it to be true. If only one reason is known or is not firm, then all possible causes should be evaluated as potential causes. When this process gets to the point where a cause(s) can be corrected to prevent reoccurrence, then the root cause(s) or causes have been found. A detailed sequence of facts and activities is developed and the apparent event causal factors are identified and categorized into human performance or equipment performance problems.

1.3 Thoroughness

As with other techniques, results are directly proportional to the extent that the person or board has defined the formal requirement for the analysis. Since the technique may be time consuming, its thoroughness is also related to the man-hours expended during the analysis itself. The event causal factors charting analysis does not produce quantitative results unless other quantitative techniques such as fault tree or event trees are integrated into the overall effort.

1.4 Comments

The event and causal factors charting analysis technique may require one or more trained personnel from several different disciplines and with varying experience. Care must be taken not to limit analysis to merely addressing the symptoms of a problem. The symptoms are sometimes causes in themselves; however, they are often only indications that other factors must be pursued to find the underlying causes. One effective general approach is to employ a board of experts headed by an experienced, independent leader to systematically track causes and effects to successively more generic levels until a root cause(s) that meets the three necessary criteria is identified. The board may include experts in system operation and testing, maintenance and repair techniques, materials, and failure analysis. No matter what technique is used, direct involvement by applicable line managers and supervisors in this process is essential to consistently achieve the desired long-range improvements.

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