As an integral part of Strapdown Inertial Navigation Systems, ring laser gyroscopes (RLG) are exposed to joint loading conditions where thermal, static and dynamic loads occur simultaneously. The effects of different loading conditions on overall RLG performance should be addressed in parallel for an optimum design. A crucial aspect in this process is the development of the path length controller (PLC), consisting of a mirror, a composite piezo electric bending actuator and other motion transfer elements. This study presents an analogy between the external loading (static, dynamic, thermal, and vibration) on PLC and the RLG signal stability, which has been studied only partially in the open literature. 5 different PLC designs are analyzed through finite element method and the results are validated experimentally using the composite piezo electric bending actuator by mode-scanning and PZT feedback tests. Obtained results illustrate the axial and the radial displacement (also named mirror tilt) capacity of different PLC designs. Disruptive effects of radial displacement of the PLC mirrors on RLG signal stability are observed. The study is concluded with the classification of different PLC designs for distinctive loading conditions, which is believed to be valuable for the aerospace industry.