Aeroelastic optimization of an advanced geometry helicopter rotor

Sensitivity derivatives of blade loads and stability in forward flight are calculated as an integral part of the basic aeroelastic analysis using a computationally efficient analytical approach, Design variables include nonstructural mass and its placement, blade bending stiffnesses (nap, lag, torsion), and blade geometry (sweep, anhedral and planform taper), Aeroelastic and sensitivity analyses of the rotor based on a finite element method in space and time are linked with automated optimization algorithms to perform optimization of rotor blades. The objective function constitutes minimization of oscillatory hub loads including constraints on frequency placement, autorotational inertia and aeroelastic stability of the blade in forward flight, Optimum design solutions are calculated for a four-bladed, soft-inplane hingeless rotor, Analytical predictions show a 25 to 60 percent reduction in all the 4/rev loads, compared to the starting design, The optimum design is swept back, drooped down and tapered along the blade span, with nonstructural mass distributed behind the elastic axis along the outer 60 percent of the blade.