Mechanics of flight in ski jumping: aerodynamic stability in pitch

Abstract

This study examines aerodynamic stability in pitch in ski jumping. Static stability implies automatic return to trimmed flight after a sudden disturbance and dynamic stability involves gradual damping of oscillatory motion. Both have implications for flight control and safety. A 3‐D inertia model of a ski jumper and the Planica K185 jumping hill profile were constructed using computer‐aided design. Inertia, jump performance, and aerodynamic efficiency and stability parameters were computed for variations in V‐style posture using mathematical modeling. Pitching moment at a 01 angle of attack was positive, and the condition dM/dα <0 at equilibrium was satisfied, indicating that the athlete is inherently stable. Enhanced flight posture consists of a ski‐opening angle of 301 and a forward‐leaning angle of 101. This is a high‐lift configuration with a large static margin that triggers a steep dM/dα slope and high oscillatory frequency upon deviations from trimmed attitude. Mechanisms of stability in pitch are proposed, founded upon theoretical aerodynamics.