Based on the rotor icing tunnel data, and considering the effect of rotor blade ice shedding and local temperature variation on the rotor blade icing, an engineering rotor icing model is advanced. Then a flight dynamics model is built of a single rotor helicopter due to icing. The trim characteristics and stability of a UH-60A helicopter in icing conditions at the hover and in the forward flight are studied in detail. Using the military specification flying qualities of piloted V/STOL aircraft (MIL-F-83300) and the handling qualities requirements for military helicopters (ADS-33E-PRF), the effect of icing on the controllability, attitude quickness, interaxis coupling, and vertical axis control power of the helicopter open-loop system are analyzed in terms of icing time, atmospheric temperature, liquid water content, and median volumetric diameter. Calculation results indicate that the rotor icing model and the iced helicopter dynamics model are feasible and effective, and that they can be used to investigate issues in helicopter dynamics in rotor icing conditions.