A novel Trimmable Horizontal Stabilizer Actuator (THSA) design of an aircraft, developed by the Institute of Aircraft Systems Engineering at Hamburg University of Technology, distinguishes itself from conventional THSA systems by its two-load-path structure that allows for higher reliability and easier maintenance. This article presents a case study of an application of four optimal ℋ_∞ controller synthesis methods (mixed sensitivity, four-block design, loop shaping and mixed-sensitivity II) to the THSA control problem. The designed controllers are then experimentally tested on the THSA test rig and the design techniques are compared with respect to the performance of their controllers and the ease of their implementation.