The vortex generator arrangement comprises a surface section forming a flow surface interacting with a flow surrounding the aircraft in operation. The surface section comprises an opening. The vortex generator arrangement further comprises a vortex generator movable between a retracted position and an extended position. In the extended position the vortex generator extends through the opening into the flow and in the retracted position the vortex generator does not extend through the opening into the flow. Furthermore, the vortex generator arrangement comprises a retainer for holding the vortex generator in the retracted position, a biasing structure for biasing the vortex generator towards the extended position and a release for releasing the vortex generator from the retainer such that the vortex generator can be moved towards the extended position. The disclosure herein further relates to a flow control system comprising a vertical tail plane for an aircraft and a control unit, an aircraft comprising a flow control system and a method of controlling the flow on a rudder surface of an aircraft.
The vertical tail plane of an aircraft and the vertical rudder mounted to the vertical tail plane mainly provide directional stability and yawing moment for rotating the aircraft about its vertical or yawing axis. The maximum yawing moment that can be generated by the rudder depends on the size of the vertical rudder and the degree by which the rudder can be deflected about a rudder axis. Simply speaking, more yawing moment can be generated with a larger rudder or a rudder that can be deflected by a greater angle. As the rudder can only be deflected by a limited angle to avoid a stall of the flow at the rudder, the maximum yawing moment is largely determined by the overall dimensions of the rudder.
As the maximum yawing moment is never required under regular operating conditions, most of the yawing moment that could be generated by the vertical rudder remains unused under regular operating conditions. In other words, most of the vertical tail only generates drag under regular operating conditions and is not required for controlling the aircraft. As drag increases, the fuel consumption increases, which reduces the maximum range of the aircraft, so therefore any unnecessary drag should be avoided.