Titanium UTTAS Main Rotor Blade

Abstract

A description of the design philosophy leading to the development of a high performance rotor blade for the Army UTTAS helicopter is presented. The Army mission requirements of 550 fpm rate‐of‐climb at 4000 ft, 95° conditions and a 1.75 g maneuver at 150 knots translate into Figure of Merit and aeroelastic achievements beyond those of existing rotors. The roles played by high blade twist, advanced airfoils, and swept tips in providing a rotor system having an unprecedented Figure of Merit of 0.75 is discussed. The technology needed to successfully use a high twist blade and yet achieve forward flight and maneuvering requirements is embodied in the titanium spar, composite cover blade. It is shown that titanium with a bending strain allowable 2 times that of aluminum and a torsional stiffness 2.5 times that of fiberglass best meets the weight, stiffness and life design requirements. The composite cover provides the durability needed for the Army mission while the high specific strength of titanium exceeds the standards of safety set by Sikorsky aluminum blades.