Weight Estimation Of Wings In Preliminary Aircraft Design

Wing weight estimation is one of the most important issues in aircraft preliminary design, as wing weight has a great effection on the flight performance, aerodynamic configuration, strength and deformation of the structure, the life of fatigue, etc. During aircraft preliminary design, wing weight prediction techniques fall in to three distinct categories, 1) Empirical, 2) Semi-Analytical, and 3) Analytical. For being applied to large transporters, two rapid methods have been developed: one is semi-analytical based on beam theory analysis; the other is analytical based on finite element method and structural optimization.1) A method of estimating the load-bearing wing weight of civil transport aircraft based on fundamental structural principle has been developed. Firstly, the wing planform is designed in CATIA environment. Secondly, the Gridgen's scripting language and MATLAB programming are employed to generate the input files for the panel method program (PAN AIR) rapidly, a MATLAB code is programmed to fit the spanload of the wing from the result of aerodynamic analysis. Then a computer program BWME(based Beam theory Wing Mass Estimation)is developed using VC++ language to apply to the eight existing transports for acquisition of the connection between wing total weight and load-carrying weight. A validation of A320-200 is given to prove the method's correction and accuration.2) A method of estimating the wing structural weight of large military transport aircraft based on finite element method and structural optimization has been developed. Based on the wing-fuselage-nacelle parametric CAD model, which is automatically created by use of CATIA application programming interface (API) through Visual Basic (VB) language, aerodynamic analysis model is automatically generated by Gridgen's scripting language and MATLAB programming. The panel method program (PAN AIR) is used for the aerodynamic analysis. A MATLAB function is programmed to fit the pressure distribution on the wing surface from the result of aerodynamic analysis. A wing structural finite element model is automatically created by using CATIA software API and PATRAN's scripting language. The size of wing structure component is optimized to obtain the least structure weight. The quantitative relations among wing planform parameters and structural weights, the locations of wing-mounted nacelle and structural weights were found out using the design of experiment (DOE) under iSIGHT environment.Through the application of CAD parametric associatic modeling codes and high accurate CFD methods, two rapid and precise means of assessing the wing weight are proved feasible and valid. The study indicates that the two methods presented in this paper can provide effective way to predict wing weight in aircraft preliminary design, reduce the cycle of design and improve design quality in aircraft preliminary design.