Inflight characterization of aircraft icing

This thesis advances the development of the Ice Management System (IMS), which has been previously proposed as an additional layer of safety against aircraft icing accidents, by presenting and validating a conceptual design for the icing characterization function of the IMS. This icing characterization function seeks to provide a near real-time estimate of the degradation of the aircraft flight dynamics due to icing. The icing characterization is extracted from various information sources comprising Hinfinity parameter identification of the flight dynamics, steady-state characterization of the aircraft trim, aerodynamic hinge moment sensing, and an estimate of the flight-dynamics excitation. Two aspects of the icing characterization are novel: (i) real-time Hinfinity parameter identification of the flight dynamics, and (ii) preprocessing and assimilation of the various measurements that individually provide partial information on the icing degradation into a single comprehensive icing characterization, the so-called sensor fusion function. These two aspects of the icing characterization are validated by applying them in computer simulation to a rich set of flight scenarios. Moreover, the Hinfinity parameter identification is applied successfully to flight-test data generated by the NASA Twin Otter icing research aircraft, and validated against an existing flight-dynamics identification technique. Finally, consideration of an independent icing degradation estimate from atmospheric and photographic measurements demonstrates that the H infinity parameter estimate provides an indication of icing degradation for a natural-icing flight test.