A gurney flap arrangement includes: an airfoil 2 with a trailing edge 6 and an opening 14 in a surface 8 of the airfoil 2; a gurney flap 1 having a first position in which at least a portion of the gurney flap 1 extends through the opening 14 and projects outwardly from the airfoil surface 8, and a second position in which the gurney flap 1 does not project from the airfoil surface 8 or projects outwardly from the airfoil surface 8 to a lesser extent; and a gurney flap actuator 3 for moving the gurney flap 1 between at least the first position and the second position.

A helicopter is described comprising a fuselage elongated along a first axis and extending between a nose and a tail boom; a tailplane with a pair of first aerodynamic surfaces elongated along a second axis; the first and second axis define a first plane; the helicopter comprises a pair of elements transversal to the first aerodynamic surfaces; and a pair of second aerodynamic surfaces generating respective second aerodynamic forces, connected to first elements, and facing and spaced from respective first aerodynamic surfaces; each second aerodynamic surface comprises one first root end connected to the respective said element, a second free end spaced from said tail boom, a first leading edge, a first trailing edge opposite to said first leading edge, a first chord at said first root end and a second chord at said second free end parallel to said first axis; the first and the second chord define a second plane tilted with respect to said first plane.