The scope of the paper is to assess the potential of using circulation control at the vertical tail plane in order to increase the maximum rudder side force. Therefore, a numerical study on the rudder design is carried out, consisting of a 2D sensitivity study, an estimation of the 3D forces and moments via lifting line method, and a verification by 3D Reynolds-averaged Navier-Stokes (RANS) simulations. Compared to the baseline rudder, the lifting line method yields a 138% increase of the rudder yawing moment due to the use of circulation control. 3D RANS simulations verify the lifting line results. The deviation between yawing moments from the RANS computations and the lifting line method is less than 11%
