Manufacture-oriented design of a topology-optimized nose landing gear fork for a small aircraft with retractable landing gear

Retractable landing gears are increasingly used in small and ultralight aircraft to increase range and cruising speeds by reducing aerodynamic drag. However, the available installation space for the landing gear is very limited. To make the best possible use of this space in terms of lightweight design and structural strength, the potential of using topology optimization in conjunction with additive manufacturing is investigated. A service life recalculation of the original nose landing gear fork was conducted after a failure of the conventional fork. The analysis confirmed that the load assumptions in accordance with CS-23 were correctly considered in the original design. However, the bending and welding processes during production introduced additional residual stresses into the system, which likely contributed to the failure. With the help of topology optimization, the fork was redesigned specifically for the loads that occur during operation while ensuring structural integrity with the aim of reducing weight and material usage. The optimized fork was manufactured from aluminium using Laser-Based Powder Bed Fusion of Metals (PBF-LB/M). In addition, another fork was constructed as a milled part based on the topology-optimized design. The limitations and properties of the manufacturing processes were taken into account. The forks were analyzed for static strength using Finite Element Method (FEM) analysis and then manufactured. Compared to the original steel fork, the milled version made from high-strength aluminium EN AW 7075 is approximately 39% lighter, while the 3D-printed fork (AlSi10Mg 3.2382) weighs about 34% less. The two new designs were manufactured and compared with the original fork. This paper evaluates the advantages and disadvantages of the designs in terms of mechanical properties, accuracy, post-processing, surface quality and manufacturing effort.