The topology optimization of helicopter tail booms is essential for improving structural performance and reducing weight. This research focuses on the tail boom of the Aérospatiale SA 315B Lama, known for its robust truss structure. The tail boom, connecting the cabin to the tail rotor, endures significant bending loads due to the main rotor's torque. Although modern tail booms typically have circular or elliptical cross-sections, this study adopts a trapezoidal cross-section for simplicity. The primary goal is to achieve minimum compliance under various loads while minimizing weight, using Altair’s Inspire software for simulations. The design space, modelled as a tapered trapezoidal structure, includes a circular hole at the rear for the tail rotor. Load calculations, based on main rotor torque and counteracting tail rotor thrust, were 19,129.5 N and 109,881.9 N, respectively. Simulations considered multiple load conditions: downward/upward bending, sideways bending, torsion, and tension. Results showed an I-beam structure under bending loads for maximum stiffness, emphasizing a semi-monocoque fuselage for torsional loads. Cross members were less critical than anticipated, except under sideways bending. The optimized design suggested horizontal cross members for sideways loads and a central rod-like structure for tension. Future designs might incorporate angled cross members to better address rotational loads. This study demonstrates the effectiveness of topology optimization in enhancing tail boom design, balancing structural integrity and weight efficiency.