The aerodynamic effect or action of aircraft components, such as wings, vertical tailplanes or stabilizers, horizontal tailplanes, rudders, control flaps and high lift devices, is based to a significant extent on the flow profile which is established in operation of the aircraft at the surfaces of the respective aircraft component. However, with increasing angle of attack flow separation or stall may occur, in which condition the flow no longer follows the respective surface, but separates and moves away from the surface, and the aircraft component loses at least part of its effect. The separation of the flow occurs primarily if the boundary layer above the surface does not include sufficient energy for maintaining the flow along the surface contour.
Vortex generators, which are also referred to as swirl vanes or turbulence generators, are projections located on surfaces of aircraft components over which flow occurs, which projections are configured and arranged to selectively generate vortices or turbulence in the boundary layer region of the flow and, in this manner, to supply the flow with energy and maintain the flow along the surface. Thereby a flow separation can be prevented or delayed, and it is possible to realize larger angles of attack without flow separation and stall.
Large angles of attack are necessary, amongst others, at low flight velocity or airspeed, so that measures against the occurrence of flow separation or stall have to be taken, for example, in the take-off and landing phase. Furthermore, critically large angles of attack may also result when the aerodynamically active shape of an aircraft component is selectively strongly changed, for example by strong deflection of a control flap of a wing or strong deflection of a rudder of a vertical stabilizer. A strong deflection of the rudder is required, for example, if thrust is decreasing on one side due to malfunction or failure of engines and steering in the opposite direction must be effected by the rudder in order to maintain the course of the aircraft.
Therefore, there is a need for particular measures for preventing flow separation and stall in particular in specific flight or operating situations. However, vortex generators always also cause an increase of drag and flow resistance so that they are associated with disadvantages outside such flight or operating situations. For this reason vortex generators are known which are selectively extendable and retractable or selectively unfoldable and foldable and which are preferably only extended or unfolded if required and are otherwise retracted or folded in in order not to increase the flow resistance.