Two issues are discussed in the paper. The first one concerns the FEM modelling of the magnetic field enclosing the permanent magnet – reed switch system. The system works as the motion detection device of the hydraulic servoactuator distributor to improve the helicopter steering reliability and flight safety. The second one describes optimization of the active magnetic bearing (AMB) design with the FEM. The optimization has two goals: weight reduction and bearing load capacity. The bearing is applied to active vibration control of helicopter flexible tail rotor shaft.