The aeroelastic behaviour and response to turbulence of a class of high performance tailless sailplanes.

The symmetric flutter and response characteristics of a class of tailless .sailplanes-:are investigated combining rigid--body dynamics with elastic modes of deformation. The methods used are based on the normal mode approach through the use of finite element techniques and unsteady aerodynamic theories in two dimensional flow. The flutter speed and. aeroelastic modes are critically examined and the results are compared with those of a tailed sailplane. The flutter speed of the tailless sailplane is found to be low in comparison with those of orthodox layout and a parametric study is undertaken to locate-the reason for this; recommendations are made for improvements. A method is proposed for the analysis of the. short period oscillation characteristics of flexible aircraft allowing for the-effects of unsteady aerodynamics. - It is then applied to the type of tailless sailplane under investigation. The response to gusts and turbulence is evaluated using both statistical and discrete gust methods. Comments are made from the calculated results about the aeroelastic behaviour of tailless sailplanes in general. Computer programs developed for detailed aero-elastic calculations are presented.