Risk Assessment: Tools, Techniques, and Their Applications

14.1 History

Knowledge of the history of the need for FTA is useful for understanding the simple, yet powerful potential of the tool. This history begins with the inception of mechanical vehicles. One common problem that plagued vehicles was malfunction and failures caused by “little things.”

Steam engines blew up when pressure relief valves stuck closed. Early autos scattered parts across the countryside as nuts and bolts separated. Airplanes fell to earth because poorly designed fittings tore apart. Always it was the little things that failed and set up potentially deadly chain reactions.

Despite major advances in design and manufacturing techniques, significant numbers of accidents and failures continued to occur. Airplane accidents, attributable to training, accounted for over one third of the losses during the WWII years 1941–1945. Over 14,000 major accidents were recorded in the United States alone.

Often, the airplane accidents were attributed to “pilot error.” However, the majority of crashes should have been linked to a malfunction of little things, such as a failed hydraulic pump, a broken feathering stop, a missing lock nut and so on.

As technology became more exotic, technological advances exceeded the average skill level for operation and maintenance of advanced air vehicles. Because of the complexity of systems, nut and bolt errors became even more frequent. Therefore, an improvement in safety analysis was needed.

This technique had to be capable of handling systems ...