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This Document is Obsolete and Is No Longer Used.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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1.1.1 This document provides NASA management and personnel with top-level guidance for conducting root cause analyses as part of investigations of close calls, anomalies, and failures. There are various methods for determining root causes, both manual and software driven, available within NASA, other Government agencies, and the private sector. Within NASA, the NASA Safety Training Center at Johnson Space Center provides training, reference materials, and resources to develop additional skills in root cause analysis based on the Management Oversight and Risk Tree (MORT) model.

1.1.2 The root cause analysis is a structured process for identifying the basic factors, reasons, and causes for conditions that result in mishaps. Once identified, the conditions can be corrected and future mishaps prevented. Objectivity and uniformity is increased by following the structured MORT root cause process in that the analyst is required to match root causes with a specific set of questions.

1.1.3 There are several definitions for root cause found in NASA documents, other Government agency documents, and the private sector. The MORT-based definition is: "The systemic factor which causes or creates conditions that may be less than adequate or that could result in a mishap and the most basic reason for a problem which, if corrected, will prevent recurrence of that problem and/or the potential occurrence of many related problems."

1.1.4 There is a common thread throughout each of the root cause definitions and that is to identify "why" the mishap occurred; however this is often confused with "what" occurred. A failure of a component, human action, or environmental factor may be what happened, but is not the root cause. Root cause analyses provide a process to identify "all of the WHY" that contribute to a mishap. Typically, an analysis effort will ask the question why at least five times; that is, why did it happen? Having determined that, why did that happen? Now, having determined that, why did that happen (etc.)? The answers to these why questions will help to identify causal factors and both systemic and localized root causes as well as root cause chains.

1.1.5 Clearly, asking the right questions during the data gathering stage will improve any analysis performed. Data gathered for the investigation is critical for the success of any root cause analysis methodology; i.e., the investigation board must ask the right questions and gather sufficient facts to identify both localized and systemic problems. This will help the investigator in identifying the chain of root causes that may reach from management to the bottom work process.

1.1.6 Once all the data has been gathered, the user should look for any trends or patterns that may be present. This can be done by first by adding up how many of the leading root causes are the same, to help identify which root cause needs the most attention. After identifying which root cause needs the most attention, a summary of the root cause findings should be written. The summary should address the most important root cause(s) first and then address the lesser remaining root cause(s). It should be noted that the largest impact on permanently eliminating root cause(s) is to correct the highest level root cause(s).

1.1.7 When considering why a mishap or incident occurred, more than one root cause must be considered. Very seldom will just one root cause create a condition that results in a mishap. In most cases it requires a chain of root causes that reaches from top management to the lowest level of the work process. Correcting the specific root cause generally will only correct the bottom-level condition. Correcting the systemic root causes is more likely to correct all of the root causes in a particular chain that reaches from management to the bottom work processes. The key element to the analysis is to evaluate the leading root cause(s) and determine the dominant root cause that, if corrected, would have the most impact in preventing the condition from recurring.

1.1.8 If the condition is concerned with the top of the root-cause tree, there may be only one or two root causes. However, if the condition is located in the bottom part of the root cause tree, there may be many root causes, spawning from management, implementation, performance of work processes, and personnel which are at the start of the work process.

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