The paper deals with modelling of a Twin Rotor MIMO System – a laboratory model constructed by Feedback Instruments Ltd. The system consists of a two rotors which resembles a simple helicopter. The non-stationary part of the model can rotate around two perpendicular axes to produce azimuth and elevation output of the system. These outputs are affected by speed of the rotors. Significant cross-coupling can be observed and the system behaviour is nonlinear. A model based on first–principle modelling was derived and is parameters were refined by identification based on real-time experiments. Resulting model was designed in MATLAB/Simulink environment and can serve for control design.