According to the characteristics of the compound coaxial helicopter, general aerodynamic forces and moments of rotors, wing, fuselage, horizontal stabilizer (contains the elevator) , vertical stabilizers (contains the rudder) and auxiliary propeller are modeled. A control strategy and its corresponding trimming algorithm are studied for the compound coaxial helicopter under various steady-state flight conditions. The conditions include the hover and low speed flight in helicopter mode, high speed flight in airplane mode, especially the conversion mode from helicopter to airplane with the linear transition method . Together with the control strategy, the trimming method is investigated to obtain the trimming values. A small-scale compound coaxial helicopter is taken as an example to demonstrate the effectiveness of the method. The result shows that the trimming values, the lift distribution of rotors and the wing under the whole steady-state flight conditions are reasonable.
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