AN EVALUATION OF HELICOPTER AUTOROTATION ASSIST CONCEPTS

Analytical research was conducted by Hughes Helicopters, Inc. and the U.S. Army to qualify and quantify the autorotation assist feasibility of various "passive" and "active" energy subsystems to provide improved helicopter autorotational performance. The results discussed herein capsulize this area of autorotation research to define both the attractive and the unattractive autorotation assist concepts from a compendium of methods and devices ranging from high performance landing gear to the rocket-driven turbine. The initial concept evaluation included first, subjective sensitivity to major helicopter design parameters, and second, concept sizing based on integration with specific cargo, utility, scout, and attack helicopters in the Army inventory, A final screening via flight simulation computer analysis for convincing evidence of the concepts' autorotation assist potential preceded final selection for preliminary design. Three of the most promising concepts for the OH-6 scout type helicopter are analyzed in preliminary design for such parameters as size, weight, response time, flight penalties, height-velocity curve reduction, and fly-away capability. Viable autorotation augmentation concepts which provide an additional source of energy to the system appear feasible for significant reduction of the height-velocity avoid region of single engine helicopters at payload weight penalties of only 3 to 8 percent depending on the helicopter and concept combination.