The control of an aeroplane is effected through the medium of three distinct sets of control surfaces known as the elevators, ailerons, and rudder, these surfaces being so disposed with reference to the centre of gravity of the machine as to be capable of producing rotation about three mutually perpendicular axes passing through this point, and called the lateral, longitudinal, and normal axes respectively. Thus, the elevators cause a rotation about the lateral axis of the machine, the resulting motion being known as pitching, the ailerons a rotation about the longitudinal axis, producing rolling, and the rudder rotation about the normal axis, producing yawing.