# Estimation of Stability Parameters for Wide Body Aircraft Using Computational Techniques
## 5 Analysis and Discussion  
This paper reports the procedure for estimating the aerodynamic coefficients of a wide-body aircraft (Boeing 747-200) using computational techniques. The major achievement  
Figure 12: Aircraft analysis using XFLR software (**a**) Variation of lift coefficient (CL) with angle of attack obtained using XFLR. (**b**) Variation of lift coefficient vs. drag coefficient obtained using XFLR. (**c**) Variation of CL/CD with angle of attack. (**d**) Variation of moment coefficient vs. lift coefficient. The trends are similar to that of the Boeing 737 commercial aircraft.  
of this research is the application of commercial packages for conventional aircraft design procedures. The obtained results at low-cruise-flight conditions show the efficacy of the codes. The design, and aerodynamic and stability analysis procedures of conventional aircraft have also been elaborated in this paper. The stability conditions were validated by acquiring basic aerodynamic coefficients. Moreover, variations of various longitudinal and lateral aerodynamic coefficients with angle of attack and control surface deflections have also been estimated successfully. The comparative study reveals that results obtained from both the codes are close to the values in the literature. Some of the parameters having great influence on the accuracy of the results for the validation of the software are given in Table 4. A summary of aerodynamic coefficients obtained from both the codes is as follows.  
* The coefficients of lift (CL) at low-cruise-flight conditions obtained from DATCOM and XFLR were 0.679 and 0.623, respectively. Both values are close to the results available in literature within the absolute error of 0.05.
* The coefficients of drag (CD) at low-cruise-flight conditions obtained from DATCOM and XFLR were 0.0371 and 0.036, respectively. Both values are close to the results available in literature within the absolute error of 0.002.
* The results obtained for lift, drag, and moment coefficient from both pieces of software are quite comparable with the literature.
* Most of the aerodynamic coefficients are within the absolute error of \(\leq\)0.01. The accuracy of the results for longitudinal and lateral aerodynamic coefficients indicate the validation of the codes.
* The comparison of aerodynamic coefficients obtained from both pieces of software at various angles of attack has been plotted in Figure 13.  
\begin{table}
\begin{tabular}{c c c c c c c} \hline \hline
**S No.** & **Parameter** & **Analytical [62]** & **DATCOM** & **XFLR** & **Abs Err DATCOM** & **Abs Err XFLR** \\ \hline
1 & CL & 0.68 & 0.679 & 0.623 & 0.001 & 0.057 \\
2 & CD & 0.0393 & 0.0371 & 0.036 & 0.0022 & 0.003 \\
3 & \(CL\)\(\pi\) & 4.67 & 4.76 & 3.62 & 0.09 & 1.05 \\
4 & \(CD\)\(\pi\) & 0.366 & 0.329 & 0.315 & 0.037 & 0.051 \\
5 & CLM & \(-\)0.0875 & \(-\)0.102 & \(-\)0.042 & 0.0145 & 0.0457 \\
6 & CmM & 0.121 & 0.153 & 0.213 & 0.032 & 0.092 \\
7 & \(Cl\)\(\delta\)\(\pi\) & 0.0129 & 0.0201 & 0.0135 & 0.0072 & 0.0006 \\
8 & \(Cn\)\(\delta\)\(\pi\) & 0.0015 & 0.004 & 0.0026 & 0.0025 & 0.0011 \\
9 & Clp & \(-\)0.323 & \(-\)0.328 & \(-\)0.41 & 0.005 & 0.087 \\
10 & Clr & 0.212 & 0.231 & 0.227 & 0.019 & 0.015 \\ \hline \hline \end{tabular}
\end{table}
Table 4: Comparison of aerodynamic coefficients obtained from DATCOM and XFLR with analytical results.  
Figure 13: Comparison of aerodynamic coefficients (**a**) Variation of lift coefficient (CL) with angle of attack. (**b**) Variation of drag coefficient (CD) with angle of attack (**c**) Variation of moment coefficient (Cm) with angle of attack. The obtained results are having same trends as well as close values. Comparison of results obtained from DATCOM and XFLR software shows accuracy of the source codes.