Camera tracking and qualitative airflow assessment of a two-turn erect spin

Abstract

Abstract Motion and airflow during a two-turn erect spin of an aerobatic light aeroplane have been analysed. An alternative method, based upon camera tracking, has been used to capture the spin motion. A CAD model of the Slingsby Firefly was created using laser scanning. Formation flights with a helicopter have been flown and high-quality video and still imagery obtained. Camera tracking has produced data and unique illustrations of the spinning Slingsby. To further investigate the aerodynamic flow of a spinning aeroplane, full-scale, flow visualisation flights have been flown using wool tufts on wing, fuselage and empennage. Tufts indicate that a large vortex forms on the outside wing. The spanwise motion of this vortex has been studied and related to the spin motion. Furthermore, tufts on the horizontal tail indicate the presence of a leading edge vortex with the flow mainly in a spanwise outwards direction. The effects observed are clearly three dimensional and time dependent. Finally, it is discussed how this new knowledge does not correspond with the spin theories of the past.