# Computational Investigation of a Novel Box-Wing Aircraft Concept
## 4 Aero-Structural Characterization of BWA/SL Aircraft
### Main Characteristics of BWA/SL Aircraft  
As can be seen in Figure 11, the BWA/SL aircraft is designed as a triplane comprising backward and forward swept wings. Although they are yet to be optimized from an aerodynamic standpoint, these wings are characterized by peculiar characteristics. The first two wings are swept backward and have an identical span that matches that of CRM, whereas the (foldable) third wing is forward swept and exhibits a 33% higher span (see Table 4). Each of these three wings is also characterized by a rather small mean aerodynamic chord (between 45% and 60% than that of CRM wing) and area (between 63% and 70% than that of CRM wing), which ultimately translate into a high aspect ratio (between 1.6 and 2.6 times that of CRM wing). On the other hand, thanks to its three-wing configuration, the aircraft offers an overall lifting area that is large (almost twice that of CRM one). The objective behind this design is to end up with a very large, long-range aircraft capable of producing massive amounts of lift against an acceptable drag.  
Regarding its other characteristics, the aircraft is meant to carry 600+ passengers with 6-abreast seating on the main deck and two-by-three seating on the upper deck. The aircraft height is nearly 24.4 m, which is within the maximum gate box size (Group VI or Code Letter F). The V-tail fins are forward swept, to reduce their impact on the pair of at wings. Notably, the roots of these tail fins could help shielding part of the noise emitted by the turbofan engines, to be mounted in a rear fuselage nacelle configuration [50]. Further, a rear mounted electric fan is envisioned to be used so as to ingest the fuselage boundary layer, thereby reducing its drag. The long fuselage is lifted at four points, as it is connected to the root of the parasol middle wing with two pylon-like structural bodies (fins). These junctions are smooth and bent, so as to even out the stress and to dampen the vibrations. Additionally, the fuselage is connected to the low-mounted front wing close to its nose region, which is characterized by an ovoid shape: the wider lower portion shall allow more payload in case of a single-pilot cockpit scenario. Finally, the wide fuselage bel  
\begin{table}
\begin{tabular}{c c c c c} \hline \hline  & **1 st Wing** & **2 nd Wing** & **3 rd Wing** & **Total/Reference** \\ \hline Area (S) & 243.8 m\({}^{2}\) & 247 m\({}^{2}\) & 270.6 m\({}^{2}\) & S\({}_{\text{ref}}\) = 761.4 m\({}^{2}\) \\ MAC & 4.21 m & 4.05 m & 3.12 m & \(c_{\text{ref}}\) = 3.79 m \\ Span (\(b\)) & 60 m & 60 m & 80 m & \({}_{\text{ref}}\) = 60 \\ Aspect ratio (AR) & 14.7 & 14.5 & 23.6 & N/A \\ Taper ratio (\(\lambda\)) & 0.802 & 0.764 & 0.761 & N/A \\ Sweep (\(\Lambda\)) & 34\({}^{\circ}\) & 31\({}^{\circ}\) & \(-\)30\({}^{\circ}\) & N/A \\ Dihedral (\(\Gamma\)) & 2.56\({}^{\circ}\) & 2.62\({}^{\circ}\) & \(-\)1.22\({}^{\circ}\) & N/A \\ \hline \hline \end{tabular}
\end{table}
Table 4: BWA/SL aircraft: Main characteristics of the planform.  
Figure 11: Box-Wing Aircraft/SmartLiner (BWA/SL) concept. **(Left)**: Early drawing of the BWA/SL with powerplant and one wing folded. **(Right)**: CAD model of the clean (unpowered) configuration.  
space for very large fuel tanks, while making the cargo compartment uninterrupted (i.e., not affected by the undercarriage).