A vortex generator assembly for use with a wind turbine rotor blade, the wind turbine rotor blade having a leading edge and an axially spaced trailing edge, said vortex generator assembly comprising: at least one vortex generator coupled to the wind turbine rotor blade, said vortex generator comprising at least one sidewall extending outwardly a radial distance from an outer surface of the wind turbine rotor blade, said vortex generator selectively positionable between a first position and a second position; an actuator coupled to the at least one vortex generator, said actuator configured to position said at least one vortex generator between the first position and the second position; a sensor for sensing an angle of attack of the rotor blade; and a control system operatively coupled to said at least one vortex generator for controlling said actuator to position said vortex generator between said first position and said second position in response to a signal indicative of the angle of attack transmitted from said sensor; characterised in that: the wind turbine rotor blade has a chordwise axis defined between the leading edge and the trailing edge, said at least one vortex generator selectively movable between a first chordwise position and a second chordwise position along the chordwise axis, said first chordwise position nearer to the leading edge than said second chordwise position; and wherein the wind turbine rotor blade has a spanwise axis defined between a root portion and a tip portion, said at least one vortex generator selectively movable between a first spanwise position and a second spanwise position along the spanwise axis, said first spanwise position nearer to the root portion than said second spanwise position. at least one vortex generator coupled to the wind turbine rotor blade, said vortex generator comprising at least one sidewall extending outwardly a radial distance from an outer surface of the wind turbine rotor blade, said vortex generator selectively positionable between a first position and a second position; an actuator coupled to the at least one vortex generator, said actuator configured to position said at least one vortex generator between the first position and the second position; a sensor for sensing an angle of attack of the rotor blade; and a control system operatively coupled to said at least one vortex generator for controlling said actuator to position said vortex generator between said first position and said second position in response to a signal indicative of the angle of attack transmitted from said sensor; characterised in that: the wind turbine rotor blade has a chordwise axis defined between the leading edge and the trailing edge, said at least one vortex generator selectively movable between a first chordwise position and a second chordwise position along the chordwise axis, said first chordwise position nearer to the leading edge than said second chordwise position; and wherein the wind turbine rotor blade has a spanwise axis defined between a root portion and a tip portion, said at least one vortex generator selectively movable between a first spanwise position and a second spanwise position along the spanwise axis, said first spanwise position nearer to the root portion than said second spanwise position. the wind turbine rotor blade has a chordwise axis defined between the leading edge and the trailing edge, said at least one vortex generator selectively movable between a first chordwise position and a second chordwise position along the chordwise axis, said first chordwise position nearer to the leading edge than said second chordwise position; and wherein the wind turbine rotor blade has a spanwise axis defined between a root portion and a tip portion, said at least one vortex generator selectively movable between a first spanwise position and a second spanwise position along the spanwise axis, said first spanwise position nearer to the root portion than said second spanwise position.