Abstract: A flexible spoiler is arranged on the suction side of a wing and spoiler is made of a narrow flexible fold tape covering a tunnel which is sealed against the outer airstream and extends inside the wing from the root to the tip thereof. When the fold tape is deployed from a conform position it forms a trip producing stall. Deploying and conforming are achieved by varying the tunnel pressure. The pressure is essentially generated and varied by the tunnel aircolumn under centrifugal acceleration and throttled by an inlet throttle near the wing root and an outlet throttle near the wing tip. Opening the inner throttle increases the tunnel pressure to deploy the fold tape in the case of maximum speed and/or shaft torque of the wind-turbine.