Influence of blade elasticity on the whirl flutter stability of a propeller-driven aircraft

Abstract

Whirl flutter stability is an important certification criterion for propeller-driven aircraft. Recent studies, e.g., with the Transfer-Matrix (TM-) method, have shown a significant stabilization of propeller whirl flutter due to blade elasticity. However, the results have been shown only for simplified dynamic models and the TM-method has not been used on full-aircraft level yet. The work related to this paper provides additions to the TM-method in order to make it useful for practical applications on full-aircraft level, as well as additional insights into the effect of blade elasticity on the whirl flutter behavior of a generic turboprop aircraft model. For the theoretical part, transformations for the propeller transfer matrices are introduced to ensure compatibility in the mass model, unit and coordinate system between the propeller and aircraft model. Furthermore, the transfer matrices are interpolated in airspeed to reduce computational time. As a use case, a generic turboprop aircraft model is introduced and frequency-domain whirl flutter results with rigid and elastic blades as well as varying thrust setting are presented. Results show that the stabilizing influence of blade elasticity observed on simpler models also applies to the full-aircraft model and is stronger than, e.g., the influence of thrust.