| Bragg, M.B., "Aircraft Aerodynamic Effects Due To Large Droplet Ice Accretions", Paper No. 96-0932, AIAA 34th Aerospace Sciences Meeting, Reno, NV, January 15-18, 1996. |
| The effect of large-droplet ice accretion on aircraft control and in particular, lateral control is examined. Supercooled large droplet icing conditions can result in the formation of a ridge of ice aft of the upper surface boot. By comparing this ice shape to data acquired with a spanwise protuberance on a different airfoil, it is clear that a ridge of ice aft of the boot can lead to large losses in lift, increases in drag and changes in the pitching moment. This effect is most likely due to the formation of a large separation bubble aft of the ice accretion which grows with angle of attack and eventually fails to reattach, leading to premature airfoil stall. The bubble alters the pressure distribution about the airfoil resulting in a more trailing edge up (negative) hinge moment on the aileron and the resulting change in aileron stick force. This can lead to aileron hinge moment reversal and aileron snatch. In aileron snatch the hinge moments are altered to the extent that the aileron is pulled up by the low pressure over the upper surface of the aileron with sufficient force to induce a rapid roll if a large stick force is not immediately exerted to oppose it. There is evidence in the literature which shows that similar lateral control problems are possible with other types of ice accretions and airfoil types. |