Geometric Analysis of Airfoil Thickness Ratio Distribution in Fixed-Pitch Propeller Blades

Abstract

This study investigates the geometric characteristics of airfoil sections in three fixed-pitch propellers used in general aviation training aircraft. The analysis focuses on the distribution of chord length, maximum thickness, and thickness ratio along the blade span. Measurements were conducted at ten radial stations, from 10% of the blade length to the blade tip, using precision measuring tools. Statistical analysis, including normality, homogeneity, and comparative tests, revealed no significant differences among the three propeller types in terms of these geometric parameters, allowing the use of averaged values for further interpretation. The results show consistent geometric trends across all propellers, with chord length and maximum thickness decreasing from root to tip, while the thickness ratio follows a similar pattern. The region around 70% of the blade span was identified as the most aerodynamically efficient, with an average thickness ratio of approximately 0.11. Additionally, differences between aluminum and wooden propellers were observed, with wooden propellers generally exhibiting higher thickness ratios due to material constraints, although these differences were not statistically significant. The study also highlights the aerodynamic implications of thickness ratio variation. Higher thickness ratios tend to increase lift and drag while reducing lift-to-drag ratio and stall performance, whereas thinner airfoils provide better aerodynamic efficiency and contribute more effectively to thrust generation. Overall, the findings emphasize the importance of balancing structural and aerodynamic considerations in propeller blade design and provide a useful reference for future research on airfoil geometry, including the role of maximum thickness location.