Initial Sizing And Optimization Of Civil Jet Conceptual Design

The initial sizing usually is the first step during aircraft conceptual design when the mission specifications are set. The task of the initial sizing is to find the primary parameters of aircraft, including the takeoff wing loading, thrust-to-weight ratio, takeoff weight, wing area, aspect ratio of wing, wing sweep, thickness and taper ratio to match the mission requirements. The purpose of this work is to provide a fast tool for the initial sizing of civil jet conceptual design.The tool consists of three modules: sizing diagram, carpet plot and wing optimization. To create an overall picture of the airplane requirements, a so called sizing diagram is needed. In the sizing diagram, the boundaries of different performance requirements are plotted as functions of the wing loading and thrust-to-weight ratio. Using this sizing diagram, the designer can select acceptable combinations of the wing loading and thrust-to-weight ratio of civil jets to match the specified performance requirements. A carpet plot is a means of displaying data dependent upon two variables in a format that makes interpolation and interpretation much easier than when using normal multiple curve plots. In the carpet plot module, the relation of the aircraft takeoff weight with the wing loading and thrust-to-weight ratio are displayed on the carpet plot, and various requirement boundaries are also plotted on the same plot. By using this carpet plot, a designer can conveniently select the values of the wing loading and the thrust-to-weight ratio to minimize the takeoff weight, while still meeting the performance requirements. The optimization module is used to find the key parameters of wing configuration including the wing area, aspect ratio, sweep, thickness and taper ratio through using optimization algorithms. The optimization formulation for the key parameters of wing configuration is explained in terms of the objective, design variables, and constraints. The objective is to minimize the takeoff weight or the direct operating cost, and design variables includes the wing area, aspect ratio of wing, wing sweep, thickness and taper ratio, and the constraints are mainly related to the performance requirements and the volume for fuel storage.An initial sizing problem of a civil jet conceptual design is used as an example to demonstrate and validate the tool. It is found that the primary parameters of aircraft can be selected conveniently by using this tools, and the initial design, which is quite reasonable compared to the realistic civil jets, is obtained in short time.