Towards Robust Whirl Flutter Prediction in Propeller Aircraft: A Critical Review of Modeling Parameters

Kurzfassung

Whirl flutter is an important aeroelastic instability, which needs to be considered during the design and certification of propeller transport aircraft. Several studies in the literature have examined the influence of individual modeling parameters on propeller whirl flutter predictions. Given the lack of a comprehensive comparison across these parameters to derive guidelines on which aspects whirl flutter assessment should prioritize, this paper compares the influence of blade elasticity and improved aerodynamic modeling, propeller operating point such as engine power, aerodynamic interaction with a wing, and uncertainty in engine mount stiffness. For comparing the aerodynamic interaction on a full aircraft model, a Doublet-Latticebased workflow for including propeller loads caused by induced velocities from the wing into frequency-domain flutter assessments is suggested. Assessing the sensitivity of the whirl flutter mechanism of a twin-engine generic turboprop to the investigated parameters reveals that blade elasticity and engine mount stiffness are the key parameters causing changes the flutter speed compared to a reference prediction. The other parameters show one order of magnitude smaller influence on the flutter speed, indicating that blade elasticity and engine mount stiffness variations may deserve particular attention within whirl flutter assessment workflows.