Marco Di Gifico, Vincenzo Vaccaro
DOI Number: N/A
Conference number: IFASD-2017-055
This paper describes the activities carried out by Leonardo Aircraft Division (LAD), in the context of a joined research project (JRP), carried out by Italian/Swedish industries and universities, mainly focused on the study of Limit Cycle Oscillation (LCO). LCO can occur because of the structural and aerodynamic non-linearities, often associated to the transonic range, but not only. Current industrial practice still relies heavily on linear methods, widely used for the prediction and analysis of flutter, and this has led to overly conservative design and envelope restrictions for aircraft. These methods are not adequate for LCO investigations and predictions, owing to the strong influence of non-linearity. As a consequence, during the aeroelastic qualification process, flutter trials have been used rather extensively to cover this deficiency, with significant impact on development risk and cost. For these reasons, it is clear that the inclusion of non-linearity in the mathematical and computational aeroelastic prediction tools is highly desirable. The scope of Italy-Sweden JRP has been that of creating a platform of validated linear and Hi-Fi analytical methods and tools for the investigation of LCO, mainly focusing on fighter external store configurations flying in transonic conditions. In order to reduce the project costs and to contain technical risks, the objectives of the JRP have been confined to the study of pylon-store structural nonlinearity and to the design, manufacture and testing of a flutter WT model in subsonic conditions. Laboratory tests and WT trials have been the source of data for the validation of methods and codes. The level of accuracy achieved by Hi-Fi aeroelastic simulations based on CFD and linear FEMs, in comparison with test results, can be considered very satisfactory and promising for future work opportunities.