Effect of geometry and mass distribution on tumbling characteristics of flying wings

Results from an investigation to determine the low-speed tumbling characteristics of 12 generic fly ing-wing models are summarized. There is some concern that airplanes with fly ing-wing planforms could inadvertently enter an out-of-contro l tumbling motion under certain conditions. The objectives of this investigation were to 1) identify the geometric and mass-related parameters that cause flying wings to be capable of sustained tumbling and 2) analyze some of the driving mechanisms that cause steady tumbling. Free-tumble and free-to-pitch tests were conducted with dynamically scaled, generic flying-wing models. Results indicated that e.g. location, mass distribution, and geometric aspect ratio strongly affected the tumbling characteristics of the models tested and that positive static stability did not necessarily preclude tumbling. The magnitude of dynamic effects were found to be of the same order as static effects for the models undergoing autorotation-in-pitch.