A twin-rotor electromechanical system whose output variables make angular motions in the vertical and horizontal planes is explored as a control plant. The mathematical model of the mechanical subsystem, which is essentially nonlinear, includes cross-coupling between propellers, dry-friction torques, and unspecified parameters; it is also subject to uncontrolled external perturbations. A mathematical model of the electric subsystem (considered dynamics of dc-drives) is approximated by linear differential equations. Directly measured are output variables, drive armature currents, and control inputs. The block-based approach was used to develop a decomposition procedure for the synthesis of a dynamic feedback that enables output variables to track specified signals with a given accuracy. To suppress unmatched perturbations, everywhere bounded nonlinear S-shaped local couplings are formed that are ensured by discontinuous controls with constant amplitudes; this enables the design constraints on state and control variables to be taken into account at the stage of synthesis. Measurements of angular positions have been used to develop a procedure for the adjustment of a reduced dynamic observer of angular velocities with S-shaped corrective actions, which does not require the model of the plant to be defined or a dynamic model of external perturbations to be introduced. The effectiveness of the approach developed has been confirmed by simulations in the MATLAB-Simulink environment.