Sensitivity of Propeller Whirl Flutter With Respect to Blade Parameters

Abstract

New methods for propeller whirl flutter prediction emerge, enabling aeroelastic engineers to include more modeling parameters and more sophisticated methods into their analysis. However, the sensitivity of propeller whirl flutter with respect to modeling parameters like airfoil characteristics, blade sweep and stiffness is not clear. This makes it hard to decide, on which blade parameters to focus when choosing a modeling tool or a validation procedure. This paper aims to provide a comprehensive overview of the sensitivity of whirl flutter with respect to the above-mentioned blade parameters, identifying those with the highest impact on stability. For this purpose, the Transfer-Matrix method is used to assess the whirl flutter stability of the simplified pylon model and a generic turboprop aircraft, using a rigid and a flexible set of parametric propeller blades. The results show that blade sweep and an increase in stiffness are strongly destabilizing for whirl flutter. Regarding the blade aerodynamics, the lift characteristics (steady lift offset and lift curve slope) and their radial distribution are the most important aerodynamic parameters, followed by drag and last the airfoil moment characteristics.