Dihedral effect of a flexible wing

The dihedral effect of a flexible wing is considered as a critical aeroelastic problem because of the importance of dihedral in determining lateral-directional dynamic stability and the large changes in dihedral that result from symmetrical wing bending during longitudinal maneuvers that approach limit load factor. Some recently declassified experimental data of the rolling moment caused by sideslip measured at low speed on an aeroelastic model of the Douglas XA3D-1 airplane are presented. A review of some early simplified methods of analysis is made, and the correlation of one of the methods with the experimental results is shown. Finally, the problem of estimating wing dihedral effect is reformulated in terms of structural and aerodynamic influence coefficients in order to utilize recent advances in lifting surface theory. The experimental data and other examples cited indicate that the aeroelastic change in dihedral effect at limit load factor can equal the value measured on rigid models.