# Effects of Aft-Body Extension Design on the Fundamental Characteristics of HWB Civil Aircraft
## 5 Conclusions  
To study the influence of the HWB aft-body extension design on the performances of aircraft, this article calculated the MTOW, basic takeoff and landing performance, and control authority of four HWB configurations. The following conclusions can be obtained after a comparison and analysis of the calculation results:  
1. The correlation between the degree of aft-body extension and MTOW of aircraft is changed over the whole range of lift-to-drag ratio. When it comes to the range around the design's lift-to-drag ratio, there is a slight reduction in MTOW with the increase in extension of aft-body fuselage. Therefore, without considering the influence of secondary power consumption, etc., aft-body extension has a positive impact on the operation economy of the aircraft. 2. In terms of general trend, aft-body extension design can moderately improve the takeoff performance of HWB aircraft, but aft-body extension design alone cannot enable HWB aircraft to reach the level of the takeoff performance of the same seat-class  
Figure 14: The control authority of the four configurations at different Mach number. TAW civil aircraft. Obviously, additional measures are needed to improve the takeoff performance of HWB aircraft, such as vectoring thrust systems. 3. The landing angle of attack can be significantly reduced through aft-body extension design. Moreover, the HWB's Spiral mode during landing has been significantly improved due to the decrease in the landing angle of attack, which is reflected in the fact that the configuration with the aft-body extension achieves convergence of the Spiral mode compared to the divergence of Spiral mode of the short fuselage configuration. 4. The aft-body extension design has improved the flight control authority of the HWB aircraft at both high and low speeds, and this improvement effect is more obvious at low speed. The marginal effect should also be noted: the improvement on the flight control authority will be significantly reduced when the aft-body is extended to a certain length. [PERSON] performed the main work of this article, including the conception of this study, calculations, and manuscript writing; [PERSON] and [PERSON] contributed significantly to the analysis of computations and the revision of this article. All authors have read and agreed to the published version of the manuscript. This research received no external funding. The authors declare no conflict of interest. * [PERSON] and [PERSON] (2019) [PERSON]; [PERSON] Assessment on critical technologies for conceptual design of blended-wing-body civil aircraft. _Chin. J. Aeronaut._**2019**, _32_, 1797-1827. [CrossRef]
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