New Mixed Method for Unsteady Aerodynamic Force Approximations for Aeroservoelasticity Studies

T HE unsteady aerodynamic forces acting on a business aircraft are calculated in the subsonic regime by use of the doublet lattice method method using NASTRAN software. These forces are further converted into the Laplace domain for aeroservoelasticity studies. In the literature, classical methods [1–3] are used to approximate the unsteady generalized forces from the frequency domain Q k to the Laplace domain Q s . These methods are as follows: least square (LS) [1], matrix Pade [2], and minimum state (MS) [3]. In this paper, we present a new mixed method based on a combination of the most well known methods available in the aeroservoelasticity literature: the LS andMSmethods.We found that ourmethod gives very good resultswith respect to the LSmethod and combines the advantages of the two classical methods LS and MS. Flutter results are presented for a business aircraft with 44 symmetric modes and 50 antisymmetric modes.