AeroElastic Design Code (AEDC) for high aspect ratio wing sizing

The aim of this work is to illustrate the features of an in-house developed piece of software (AEDC) to perform the aeroelastic analyses concerning the different steps of a high aspect ratio wing design. The wing is wholly made of composite material: a common high-strength graphite/epoxy is used for the spars and the facings of the skin panels in a honeycomb core sandwich. The code, written in Fortran language, is constituted of several modules: two modelling modules for the complete aeroelastic model definition and three analysis modules for divergence, flutter and gust analysis according to JAR 25 airworthiness design requirements. By means of a random gust analysis, AEDC determines/updates the external load characteristics (shear, bending and torque moment) acting on the wing and evaluates the equivalent static forces for the finite element model using a matched gust manoeuvre. Once the aerodynamic model of the wing and tail plane is constructed, a first load evaluation is obtained under the hypothesis of trimmed rigid aircraft, according to the Houbolt criteria. Using the results of preliminary wing sizing performed in a multi-level integrated procedure (MLISS), the elasticity of the structure is introduced in the aircraft trimming equations in order to update the previous loads. But if the loads change a new sizing is requested and so on. These iterations between external load updating and structural sizing run until the convergence is reached; the final structure has the minimum weight for the fixed load condition and doesn't exhibit aeroelastic instabilities.