Numeric simulation of a glider winch launch
Santel, Christoph Georg
Aachen : Publikationsserver der RWTH Aachen University (2008, 2010)
The simulation presented in this thesis illustrates some of the basic mechanisms governing the winch launch as it is practiced at many gliding sites worldwide. Whereas several comprehensive cybernetic models have been coupled in this simulation, areas still in need of improvement within each model have been pointed out for future enhancements. Results could be improved by including an aerodynamic ground effect model and properly modeling the ground to carry the glider and cable. Friction of the ground against the glider and cable should also be modeled in the future. More detailed aerodynamic data on the behavior of the glider in stalled ight needs to be implemented to strengthen the expressiveness of the performed safety analyses. It should also be attempted to gain data of actual winch types and depict a more modern driveline setup regarding a torque converter and other similar equipment and regard the effects of density altitude on engine performance. The numeric diculties having limited the minimum cable segment length need to be analyzed and solved to improve cable resolution. In the future, the virtual winch operator and pilot behavior need to be compared to actual human behavior. Enhancements of the control laws might regard aspects of fuzzy logic or adaptive control. Also, the enhancement of the simulation to include humans in the loop is thought to be possible. While the general operationability of winch launches has been proven in practice for several decades, it is also supported by the presented results. It has also been shown that the current methods of winch launching have found an acceptable compromise between performance and safety as no highly critical situations have been found in the reference launch. The existing regulations on tailwind operations are supported by the presented data and gusts seem to have little effect on the weak link force, considering the given wing loading. The destabilizing effect of a quick opening of the winch throttle on the glider's phugoid mode is shown, as well as the possibility of optimizing the tow hook location. Increases in release altitude are gained through changes in the cable type, tow distance and the maximum winch force. While studying the inuence of different physical forces on the cable, by varying the cable models, aerodynamic cable drag is identied as another major influence on release altitude, and is analyzed further by varying the drag coefficient. At last, the dynamics of an aggressively own launch is looked at and the results are in unison with the focus of current training curricula.