On Stall Behavior in Aerobatic Figures with an Aerobatic Glider

Abstract

In order to optimize stall behavior of aerobatic gliders in aerobatic figures, which include rapid autorotational spins like snap rolls, research on aerodynamics that leads to the necessary stall is needed. Combined trailing and leading-edge stall is found to be the most convenient stall type to be aimed for in an aerobatic glider. Investigations using XFOIL, as well as CFX, a numerical CFD method by ANSYS, wind tunnel experiments and flight tests are carried out to learn more about flow separation at the leading edge. The focus of this work is the laminar separation bubble that forms at the leading edge of the wing. There exist different ideas of predicting its behavior around the maximum lift-coefficient and the resulting type of stall. Ultimately, this paper examines what happens during flow separation at the leading edge of existing aerobatic gliders and the newly designed Mue 13-33 airfoil. It was found, that the laminar separation bubble, which forms at the leading edge at high angles of attack, remains there during and after stall and therefore has no direct influence on the stall process. This stall behavior is not described in existing literature so far.