A Rotatable Stabiliser for the Control of Pitch and Yaw in a Radio-controlled Aircraft

Abstract

This research implements a design for the control of a rotatable stabiliser which, it is proposed, might augment, or fully replace, the conventional control mechanisms for pitch and yaw in certain types of aircraft. The anticipated advantages of such a device are around 25% less drag, for a capability which ranges between equivalent and greater than twofold that of a conventional tail. The tail of a popular, radio-controlled, model aircraft is replaced with a rotatable stabiliser and its rotation is effected by way of a continuously-rotating servo, modified with a potentiometer. Two hollow, carbon-fibre shafts (one sleeved within the other so as to allow free rotation) serve as the mechanical link between the servo and the tail. Inserting wiring along the full length of the innermost shaft and incorporating three slip rings into its collar, at the forward, servo end, facilitated an electrical supply to the tail. A mapping betweeen the position of the controls and states of the stabiliser is formulated. Small and continuous adjustments cause the stabiliser to rotate in the opposite direction to the controls (when viewed from aft) and the deflection of the hinged control surface is proportional to the radial displacement of the controls from their centred position. For what would amount to large and contradictory rotations of the device in terms of this protocol (rotations greater than 90$^\circ$), the desired configuration can be more efficiently achieved by regarding the device's original orientation to differ by 180$^\circ$ from what it actually is and by reversing the sign of the deflection. One consequence of this latter mode of control is that a symmetrical aerofoil is indicated. General flight, including static longitudinal and directional stability, was not found to be compromised.