Sedlmair, NicolasNicolasSedlmairTheis, JulianJulianTheisThielecke, FrankFrankThielecke2021-12-172021-12-172022Journal of guidance, control, and dynamics 45 (4): 726-739 (2022)http://hdl.handle.net/11420/11329Automatic landing of aircraft is a challenging guidance and control task that requires multiple feedback loops and a precise sequence of actions. Increasing operational flexibility and reducing the dependence on external infrastructure are key challenges for future unmanned aircraft. Usually, an aircraft performs the final approach on a straight line. This paper contributes a complete automatic landing controller capable of using three-dimensional curved approach paths all the way until touchdown. The controller consists of a nonlinear guidance law that steers the aircraft along a predefined spline path, various single-input–single-output control loops for rate and attitude control, and a robust multivariable flare controller. This flare controller ensures a three-point landing, i.e., simultaneous touchdown of all three wheels. Further, practical issues such as bumpless mode transfer and anti-windup compensation are considered. The controller is evaluated in multiple flight test experiments. Both the crabbed approach and the sideslip technique are demonstrated on several different approach paths, such as a steep curve and a helix. These paths are particularly challenging, because the flare maneuver is performed while the aircraft is in a turn. The controller is shown to reliably land the aircraft on an unpaved runway with high precision.en0731-509020224726739American Institute of Aeronautics and Astronautics (AIAA)TechnikJournal Article10.2514/1.G005917Other