The first direct statement of the problem of controlling an aeroplane, without the permanent exercise of physical effort by the pilot, appears in this paper. During the state of transition from straight flying to flying in a circle, a pilot exerts a force to pull over the rudder and in the usual case it is necessary to maintain some force in order to make a continuous turn. Professor Bryan proposes the design of an aeroplane such that turning having been started, maintenance of turning is obtained without any effort being necessary to keep the rudder in position. So far as the pilot is concerned the same result would be obtained by balancing the control surfaces, but the effect on the aeroplane is quite different. In the case of balanced controls a lateral force is still exerted by the rudder and so stresses are introduced in the tail structure of the aeroplane ; on the other hand, in an inherently controllable aeroplane, there is no lateral force on the rudder when turning and, therefore, no stresses in the tail.