The effects of icing on the longitudinal dynamics of an icing research aircraft

Icing affects the aerodynamic performance of aircraft leading sometimes resulting in catastrophic crashes. The effects of icing have been studied in the past but from more of an aerodynamicist’s viewpoint than a flight controls viewpoint. This paper develops models for aircraft dynamics in the presence of icing that can ultimately lead to a model based method of detecting icing. Flight test data from the NASA Lewis Twin Otter Icing Research Aircraft is analyzed in both case of a nominal un-iced configuration and a horizontal stabilizer experiencing icing due to a failed de-icing boot. Robust global nonlinear models were developed for each flap setting. The global nonlinear and localized linear models were analyzed for the differences between nominal and iced conditions with excellent agreement between model predictions and flight test data.