U.S. Army Board for Aviation Accident Research (USABAAR) data are reviewed to define the general trends in rotary wing mishap experience. Factors which have caused aviation accidents are identified and compared to further define the accident prevention problem. The cause factors of materiel failure, malfunction and design deficiency are selected for further examination through a discussion of several examples taken from accident case histories. While component modification has long been employed to correct materiel deficiencies, it is shown that this approach has often fallen short of truly eliminating the problem. The application of the system safety concept in the elimination of materiel related accident cause factors in existing rotary wing aircraft is outlined. The close interrelationship of all assurance sciences is discussed as an essential element of risk management at any point in the life cycle of a system. The adaptability of this approach in military systems to civilian products is shown.