Investigations Concerning the Coupled Wing-Fuselage-Tail Flutter Phenomenon

Abstract

Results of subsonic model tests and analyses of a critical mode of flutter of a wing-fuselage-horizontal tail combination are presented. Increasing wing sweep can lead to lower flutter speeds. Flutter speeds are a minimum for cantilever wing bending to fuselage torsion frequency ratios in the range of 0.3-0.6. Vertical separation or dihedral angle increases the flutter speed and is more important than longitudinal separation. The aerodynamic interference effect of the wing on the tail is important and a detrimental feature for the configuration used. Flutter analyses using doublet lattice and kernel function unsteady aerodynamics methods were conducted to evaluate the accuracy of the prediction methods and to define controlling criteria. Also, experimental flutter model data and theoretical comparisons in the Mach number range of 0.6 to about 1.0 obtained in investigations conducted for the Air Force Flight Dynamics Laboratory are presented. In general, agreement between predicted and test results for subsonic and transonic investigations is good. Finally, aerodynamic prediction methods are applied to the wing-horizontal tail configuration selected by AGARD for comparisons.