Rotor Blade Design For a Fan-Jet-Powered Heavy-Lift Helicopter 690685
The many technical considerations involved in the design of a lightweight, simple, and inherently fail-safe rotor blade for use on a large fanjet-powered Heavy-Lift Helicopter are the basis for this paper. The structural design is oriented toward minimization of dynamic loads response, both as seen by the blade and as transmitted to the airframe and to the rotor controls. Unique to this blade design is the need to perform as a fanjet propulsion duct simultaneously with the other conventional rotor blade functions. Pressurization and thermal effects must thus be considered in the overall technical picture, as well as duct area and hydraulic diameter considerations. The propulsion gases under pressure act to provide inherent damage indication for the primary structure. The low dynamic response and the simple notch-free structure are expected to provide excellent fatigue life. Thermal environment permits use of all major rotor blade structural metals except aluminum alloy. The light blade weight in conjunction with the tip nozzle acts to inherently reduce the coning angle versus blade weight. Cost and maintenance are expected to be competitive with conventional shaft-driven rotor blades of similar size.