Balanced rudder Balanced rudders are used by both ships and aircraft . Both may indicate a portion of the rudder surface ahead of the hinge , placed to lower the control loads needed to turn the rudder . For aircraft the method can also be applied to elevators and ailerons ; all three aircraft control surfaces may also be mass balanced , chiefly to avoid aerodynamic flutter . Ships . A balanced rudder is a rudder in which the axis of rotation of the rudder is behind its front edge . This means that when the rudder is turned , the pressure of water caused by the ships movement though the water acts upon the forward part to exert a force which increases the angle of deflection , so counteracting the pressure acting on the after part , which acts to reduce the angle of deflection . A degree of semi - balance is normal to avoid rudder instability i . e . the area in front of the pivot is less than that behind . This allows the rudder to be moved with less effort than is necessary with an unbalanced rudder . The balanced rudder was invented by Isambard Kingdom Brunel and first used on the SS Great Britain , launched in 1843 . Aircraft . Control of aircraft is complicated by their motion in three dimensions , yaw , pitch and roll , rather than one but there is a similar need to reduce loads , tackled in the same way as on a ship with some part of the surface extending forward of its hinge . This is referred to as aerodynamical balance . In addition , because aircraft control surfaces are mounted on flexible structures like wings , they are prone to oscillate ( " flutter " ) , a dangerous effect which can be cured by bringing the centre of gravity ( c . g . ) of the control surface to the hinge line . This is called mass balancing Aerodynamic balancing . The principle is used on rudders , elevators and ailerons , with methods refined over the years . Two illustrations of aircraft rudders , published by " Flight " Magazine in 1920 , illustrate early forms , both with circular leading and trailing edges . Both are mounted so that the area of the balancing surface ahead of the hinge is less than that of the rudder behind . Various layouts have been tried over the years , generally with smaller balance / rudder areas . Most fall into one of two categories : horn balanced , with small extensions of the control surfaces ahead of the hinge lines at their tips , or inset balanced with extension ( s ) of the control surface into cut - outs in their supporting fixed surface . Frise aileron s use a variant of the latter balance , with the nose of the up - going surface projecting below the wing , but not vice versa , to provide both balancing and asymmetric drag . Irving balance d ailerons have no projections but harness the aileron deflection induced change of pressure above and below the wing , sensed via the hinge gap , to assist the motion . Mass balancing . Flutter occurs when the control surface is displaced from its intended deflection . Because the ailerons are on the long , narrow wings which can twist under load , they are the surface most prone to oscillate . If the c . g . is behind the hinge , the surface can move like a pendulum and undergo forced simple harmonic motion with increasing amplitude . Adding balancing weights which make the centre of gravity and hinge line coincident solves the problem . These weights may be in the nose of the surface , or lighter masses attached further ahead of the hinge externally . References . Bibliography . Oscar Parkes " British Battleships " ISBN 0 - 85052 - 604 - 3