Helicopter blade loads control via multiple trailing-edge flaps

An active loads control strategy is proposed for the blade loads' reduction. The concept involves straightening the blade by introducing multiple trailing-edge flaps with 1/rev control inputs for a fourbladed articulated rotor system. An aeroelastic model, which includes the quasi-steady blade aerodynamics with a linear inflow model and the classical incompressible theory for trailing-edge flaps, is used to explore the feasibility of blade loads control. An optimal control algorithm is derived for the defined objective function (including blade loads, vibratory hub loads and control efforts) to control both blade loads and vibration. Analytical studies are carried out for a steady-state forward flight condition. It is demonstrated that maximum flapping bending moment is reduced by up to 33%, and pitch-link loads' peak is reduced by up to 40%. For the rotor with cambered airfoils, pitch-link loads' peak can be reduced further by 81%. It is anticipated that a proposed control method could provide a solution of problems associated with the blade loads of heavy lift class helicopters or the pitch-link loads of the rotor with high cambered airfoils.