Abstract: A wind turbine generator blade includes a movable front portion, extending from the faster-moving blade tip in a span-wise direction along the blade, and mounted on a pivot axis permitting the front portion to be displaced to a "high drag" position in which it has a high negative angle of incidence which will in turn give rise to a high negative angle of attack to the relative airflow and hence an increased drag tending to slow down an overspeeding blade, but will also give rise to an increased lift which assists in slowing down the overspeeding blade. It has been found that a truncated aerofoil section such as that used for the front blade portion has a relatively high stalling angle, allowing its use in conditions such that the angle of attack may approach 30.degree. without stalling of the front blade portion, but in the presence of a considerably increased total drag on the blade.

Abstract: A wind turbine operated electrical generator system, said system comprising a wind turbine of the axial flow type, the blades of the turbine including tip portions pivoted with respect to the remainder of the blade, a generator driven by the wind turbine and designed to operate within a given rotational speed range, said speed range being below the speed at which the wind turbine can develop its maximum power, a pin and socket connection on the outer end of at least some of said blades, and preferably each blade, for connecting the tip thereto and a cam track on the pin or socket, with a follower on the socket or pin, respectively, the cam track being shaped to cause the tip to pivot under centrifugal movement of the tip, so that a change in the torque produced by the pivoting at all times maintains the speed substantially within said given range, resilient means being provided to restore the position of the or each tip against centrifugal action.

Abstract: A wind turbine for a wind turbine electrical generator set in which movable nose portions are located at or adjacent the leading edge of the blade and at or adjacent the tip of the blade but is dispaceable purely longitudinally of the blade, i.e. radially outwardly of the blade, from the normal retracted position, in which the portion contributes to the lift of the aerofoil section, to an advanced position in which drag is produced, to prevent unwanted increase in the speed of the rotation of the rotor.