| Bragg, M.B., "Aerodynamics of Supercooled-Large-Droplet Ice Accretions and the Effect on Aircraft Control", Proceedings of the FAA International Conference on Aircraft Inflight Icing, Springfield, VA, Report No. DOT/FAA/AR-96/81,II, Vol. 2, Aug. 1996, pp. 387-400. |
| The effect of large-droplet ice accretion on aircraft 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 an 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. The fundamental aerodynamic cause of this lateral control problem is the same as that experienced when elevator control is lost due to horizontal tail stall. |