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This Document is Obsolete and Is No Longer Used.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 Method

The methodology uses universal event building blocks, organized into sequentially timed events matrices with links showing causal relationships among events to describe the processes required to produce outcomes of interest. Events are formulated in a rigorous "actor + action" format, stating who or what (people or objects) must do what to produce the next event. In mishap investigations, transformation of mishap data into events building blocks and their display in the STEP worksheets disciplines data gathering, organization, and analysis to produce a verifiable description of a mishap process. "Programmer" concepts guide witness interviewing and identification of human factors problems. Gaps in the events flows are hypothesized systematically using logic trees (Back STEP or Fault Tree Analysis (FTA)). Causal links show why the process continued to its outcome.

1.2 Thoroughness

Properly performed, this methodical STEP process identifies conceptual, design, operational, procedural, systemic, code standards or regulatory deficiencies, and other problems. STEP includes applicable quality control procedures utilizing poison word lists, event pairing, and necessary and sufficient logic testing of each event and link on the matrix. The STEP methodology is a generally applicable methodology for the definition and systematic analysis of simple or complex systems or processes to satisfy system safety requirements. Its major strength is its ability to focus group analysis tasks and energies on substantive risks. Analysis findings drive the scope of the analysis as it progresses. STEP is open-ended, with the theoretical capacity to analyze an unlimited number of actions (behaviors) by people, equipment, and materials and show their causal interactions during normal, accidental, or postulated occurrences. Behaviors of materials of construction, equipment and components, and hazardous materials have been related to actions by operators, supervisors, responders, and exposed personnel to understand potential risks, breakdowns, failures, mishaps, or releases in transportation, chemical, electronic, environmental, manufacturing, commercial building, and petroleum drilling and refinery risk analyses. Safety effectiveness of all control options can be analyzed by tracking their effects on the worksheets. New flow charting computer programs facilitate worksheet development.

STEP work products display the depth and thoroughness of the analysis. STEP quality control procedures for work products provide rigorous tests of their contents, consistency, and validity. STEP procedures demand and help achieve an understanding of the system and its operation in sufficient detail to develop a trustworthy process description and explanation suitable for proactive or retrospective risk management. STEP disciplines process descriptions and quickly exposes uncertainties and misunderstandings. As evidence of their ability to facilitate thoroughness, STEP worksheets typically are revised 3-5 times before analysis participants agree that the worksheets faithfully describe the system operation.

1.3 Comments

Analysts must understand fundamental STEP process description concepts and procedures. Ability to transform data into events, visualization abilities, and mastery of sequential, deductive, and inductive logic are essential. Skill building occurs whenever the methodology is applied to a problem encountered in anticipated normal or abnormal occurrences. Availability of persons with mastery of the system design, inputs, operation, control, servicing, and outputs may also be required.

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