Engine Placement Effects on the Flutter of a Medium-Range Box-Wing Aircraft

This study investigated the effects of powered engines on the stability boundaries of a box-wing configuration. The governing equations were obtained using Hamilton's principle. The equivalent effects of engine's mass and thrust were simulated using a concentrated mass which was subjected to a follower force. The structural dynamics of the box wing were modeled using two cantilever beams which were attached to each other through two longitudinal and torsional springs at their tips. The aerodynamic loads applied on the wings were calculated using Wagner's unsteady aerodynamic model. The time-dependent and the parameter-dependent integral parts were eliminated using the multistep semianalytical method. To validate the developed aeroelastic model, the flutter speed and frequency of conventional wings and box wings were obtained, and very good agreement was observed. The analysis showed that the stability of the wing can be affected when the effects of engines are considered. Furthermore, the engine placement and thrust effects on the box-wing flutter speed and frequency were considered.