# Estimation of Stability Parameters for Wide Body Aircraft Using Computational Techniques
## 1 Introduction
In the present research, stability parameters for wide-body aircraft have been estimated using computational techniques. The comparison of statistical software (DATCOM) with a computational technique (XFLR) for a wide-body Boeing 747-200 is also presented. Although these software programs have been tested and evaluated multiple times, a one-to-one comparison for a Boeing 747-200 is the first of its kind. Results obtained from US DATCOM and XFLR software were compared for any differences and the they were also validated with analytical correlations presented in the literature. The material covered in the different sections is as follows. In the second section, a brief overview of the US DATCOM algorithm, its applications, and its working principle to determine the stability and control coefficients have been discussed. Aerodynamic coefficients of a wide-body airplane have been estimated at given flight conditions. The variations of lift, drag, and moment coefficients have been obtained at various angle of attack. Moreover, longitudinal and lateral aerodynamic coefficients have also be acquired at different angles of attack and control surface deflections. In the third section, the XFLR algorithm to determine the stability and control analyses of an aircraft has been elaborated. The various applications and limitations of XFLR in aircraft design and analysis have also been discussed. In order to estimate the aerodynamic coefficients of Boeing 747-200 aircraft, the elements of the design process, including direct foil analysis, and wing and body design and analysis have been elaborated. The results of lift, drag, and moment coefficients have been acquired at different angles of attack and they have been plotted. Moreover, to check the stability conditions, eigenvalues for longitudinal stability (short period and Phugoid) and lateral stability (spiral, roll, and Dutch roll) modes have also been evaluated. In the fourth section, results obtained from both the commercial packages are presented in terms of dimensionless aerodynamic coefficients. Results obtained at low-cruise-flight conditions have been compared with the analytical results available in the literature. The comparative analysis shows that results obtained from computational techniques are quite close to each other and to the analytical results. The comparison of longitudinal and lateral coefficients obtained from both pieces of software with the results available in the literature is summarized in Appendix A. In the fifth section, analysis and discussion of the results obtained from both pieces of software have been given. Aerodynamic coefficients having a great influence on the accuracy of the results for the validation of the codes are also presented. Moreover, a graphical representation of aerodynamic coefficients at different angles of attack have also been added. In the sixth section, the conclusions have been drawn based on a comparison of results and computational analysis. The analysis provides meaningful results for the estimation of longitudinal stability and control derivatives from the knowledge of aircraft geometrical parameters and given flight conditions. In order to improve the source code by exploring some advanced features, a few recommendations have also been added in that section.