As part of an analysis of the value of synthetic (simulated) training in the U.S. Army Aviation School, costs associated with the conduct of flight and synthetic training in the instrument phase of the Army's Officer/Warrant Officer Rotary Wing Aviator Course (helicopter operation) were identified and computed separately for each type of training. It was found that, for the factors considered, the hourly cost of flight training at the time of this study (September 1966) was about six times as great as the corresponding cost of synthetic flight training. The report describes sources for and treatment of data, and the major assumptions made in allocating the costs. (Twenty tables and an organizational chart are included.) (Authors/LY)