GB645187A - Improvements in or relating to fins for craft operating in fluids - Google Patents

Abstract

645,187. Controlling aircraft. GARBELL, M. A. July 24, 1947, No. 19884. Convention date, July 16, 1946. [Class 4] An aircraft comprises at least one pair of fins arranged at opposite sides of the longitudinal axis of the aircraft, said fins being of such a fluid-foil section to produce a sharp profile-drag increase when subjected to an angle of attack below that of zero lift and a normal low profile drag when subjected to an angle of attack above zero lift, said fins being positioned about said axis so that in the normal motion of the aircraft the fins operate at their angle of no lift, whereby any deviation of one of the fins and the aircraft from the angle of attack of no lift, toward a negative angle of attack creates a sharp profile drag increase which tends to return that fin and the aircraft to the angle of attack of no fin lift. The fins 7, 8 are of cambered aerofoil section and are inwardly inclined at their leading edges to produce static or " weathercock " stability of the aircraft. If the aircraft is yawed relative to the direction of normal airflow one fin will generate maximum lift and minimum drag while the other fin will operate under reverse conditions with the result that the longitudinal axis of the aircraft will be swung back into line with the direction of airflow. An annular cambered aerofoil may be used to ensure stability in more than one plane and a method of determining the optimum size of fin or aerofoil section to ensure the maximum stability to drag ratio is described.