Identification of the static and dynamic numerical model of a jet aircraft wing from experimental tests

Aircraft users are often lacking in design data required to certify the most invasive modifications. This is the case of military aircraft users, when dealing with new stores integration, or civil users when implementing any kind of new mission system. Common challenges are related to structural dynamics effects of modifications, which might significantly alter the aircraft behavior within the authorized flight envelope. Thus, before passing to flight test, even if detailed aircraft data are unavailable, an updated dynamic model for the structure under test shall be created. The purpose of this paper is to propose a reverse engineering based structural dynamic model updating method as applied on a 3rd generation tactical aircraft wing. The wing geometry was reverse engineered by laser scanning, allowing a precise reconstruction of the external wing surface while the internal structural elements characteristics were determined by direct measurement and maintenance documentation. Wing bending and torsional stiffnesses were experimentally determined on ground, comparing wing laser scanned point clouds under multiple load conditions. Despite the wing extreme stiffness, typical for the aircraft class, accurate measurements were collected in a totally non-invasive way. Ground Vibration Tests (GVTs) results collected during past experiments were employed to extract wing modal data. Following geometry reconstruction and experimental data gathering, a FEM model of the wing was created. Manual updating of the FEM model was conducted based on static deflection test data first as obtained with an innovative and precise method. Then, experimental modal data were used to define non-structural mass distribution. Further model updating was carried out with the Predictor-Corrector (P-C) algorithm. The resulting FEM model presents an excellent correlation with gathered experimental data, demonstrating the proposed reverse engineering method is effective and suitable whenever limited data is available on the aircraft structures under test.