An Improved Process for the Generation of Drag Polars for use in Conceptual/Preliminary Design

One of the most essential contributors in the aircraft sizing and synthesis process is the creation and utilization of accurate drag polars. An improved general procedure to generate drag polars for conceptual and preliminary design purposes in the form of Response Surface Equations is outlined and discussed in this paper. This approach facilitates and supports aerospace system design studies as well as Multi-disciplinary Analysis and Optimization. The analytically created Response Surface Equations replace the empirical aerodynamic relations or historical data found in sizing and synthesis codes, such as the Flight Optimization System (FLOPS). These equations are commonly incorporated into system level studies when a configuration falls beyond the conventional realm. The approach described here is a statistics-based methodology, which combines the use of Design of Experiments and Response Surface Method (RSM). Computational aerodynamic codes based on linearized potential flow and boundary layer theory are employed to generate the needed parametric relationships. The process is facilitated through the use of an automated computational architecture that is capable of handling massive exchanges of data and information. The aforementioned process is demonstrated through an implementation of the procedure for a High Speed Civil Transport concept. The accuracy of these Response Surface Equations is finally tested to demonstrate the fidelity and accuracy of their predictive capability.