Adaptive Control of Aircraft in Uncertain Icing Conditions

Ice accretion on aircraft is, at times, unavoidable. The unpredictable effects of ice on aircraft dynamics makes an encounter with a weather pattern where ice accretion is likely a dire situation. The many shapes and areas on the aircraft where ice can form can either have no effect on the control or total loss of control of the aircraft. The objective of this research is to first present the results of a modeling study of the effects of ice on the equations of motion of an airplane. The next objective is to show that an adaptive control scheme can compensate for the unpredictable and detrimental effects ice accretion has on aircraft stability and control. A linearized model of a Cessna 208 Super Cargomaster is presented for situations where the aircraft is in no icing conditions, fully iced, and horizontal tail icing only. The latter two icing conditions are to be the worst case scenarios of such a situation. The iced aircraft models are based on data taken from the effects of ice accretion on a DeHavilland Twin Otter aircraft. Simulations for a classical fixed gain controller as well as an adaptive output tracking scheme are presented for comparison purposes. The classical fixed gain control simulations illustrate the detrimental effects of ice accretion on flight control while the adaptive output tracking controller simulations detail the effectiveness of adaptive control to handle the resultant changes in aircraft dynamics.