System Safety for the 21st Century, 2nd Edition

CHAPTER 17Project Evaluation Tree

Project evaluation tree (PET) analysis is a formerly used technique. It is an adaptation of a program originally developed for the U.S. Air Force’s Tactical Air Command (TAC) in 1988. The TAC’s ground safety community had been involved with management oversight and risk tree (MORT)—based training for several years. A continuing point of concern was the complexity of the MORT chart’s 1,500 different events and multiple transfers. Even though the value of the MORT chart as an accident investigation tool was evident, it seemed like overkill for use on many of the types of mishaps investigated by ground safety personnel. Thus, a tool was desired that would use a MORT‐type approach but would be quicker and simpler to learn and use, could be tailored for use by single investigators (as opposed to boards of investigation), and would be written in Air Force terms.

The program developed was the Combat‐Oriented Mishap Prevention Analysis System (COMPAS). It used two analytical charts. One, the COMPAS A chart, was basically a big positive tree showing the overall organization of a typical TAC wing, broken down organizationally and then broken down into the people, procedures, and facilities and hardware for that particular part of the organization.

The COMPAS B chart was an analytical tree that contained evaluation criteria to be applied to the personnel, procedures, and/or facilities and hardware identified or selected for evaluation on the A chart. ...