Elastic-mode effects on the dynamics of a delta-winged aircraft

An examination is made of some effects of rigid-body elastic-mode coupling on the longitudinal dynamics of a highly-flexible delta-winged aircraft. In particular, the influence of the coupling on the automatic control system´s ability to provide preselected short-period dynamics is investigated. Also, a brief check is made of the sensitivity of the dynamics to small errors in elastic-mode shape. The coupling is shown to be quite severe, precluding the establishment of approximate control element gain values with only a rigid-body dynamic analysis. In addition, very high accuracy is needed in determining elastic-mode shapes, since the strong coupling renders the dynamics objectionably sensitive to small errors in elastic-mode shape data.