Aeroelastic stability assessment of a V-tail with integrated propulsion units

Abstract

This paper deals with the aeroelastic stability assessment of the empennage section of the hybrid-electric motor glider FVA 30. Because of its integrated propulsion units at the tips it is prone to a special kind of aeroelastic instability called whirl flutter. This instability involves the whirl modes of the propellers. Parameter studies regarding the most important structural parameters are carried out to evaluate the design space and identify critical flutter modes. The models are also checked for empennage flutter and ground resonance. Due to the early design phase this is done by numerical studies with simplified models using the DLR in-house flutter process, PySTAB, and strip theory propeller aerodynamics. The investigations show the possibility of a V-tail-flutter due to insufficient mass balance of the combined elevator/rudder control surface. In contrast, the empennage structure shows large margins regarding whirl flutter of the tailplane structure itself. The pylon and engine mount are assumed to be rigid though due to lacking design data. Ground resonance of the elastic propeller blades is prohibited by the dynamics due to blade twist.