## 4 Results and Discussion
### Influence Analysis of the Overall Parameter  
In aircraft design, the way in which the overall parameters of the vertical take-off and landing fixed-wing UAV affect the flight envelope is straightforward. In this work, the flight envelope of the vertical take-off and landing fixed-wing UAV is analyzed from the perspective of overall parameters, and a method for the design of the transitional corridor of the vertical take-off and landing fixed-wing UAV is proposed. The deflection angle-speed envelope of the ducted lift-increasing system based on the stall angle of attack is calculated with the maximum lift coefficient, and the stall angle of attack of the wing is mainly affected by the wing area, the wing lift coefficient, and the wing installation. Therefore, the deflection angle-speed envelope of the ducted lift-increasing system based on the stall angle of attack is affected by these parameters. Figure 13a shows the ducted lift-increasing system's deflection angle-velocity envelope based on the stall angle of attack after the wing area increased by 10%, 20%, and 30%, and Figure 13b shows the deflection angle-speed envelope of the ducted lift-increasing system's variation diagram based on the stall angle of attack after the maximum lift coefficient increased by 10%, 20%, and 30%. It can be seen that changing the wing area and changing the maximum stall lift coefficient can change the position of the deflection angle-speed envelope of the ducted lift-increasing system based on the stall angle of attack. The flight envelope moves to the left when increasing the wing area and increasing the maximum stall lift coefficient, and the flight envelopes expand by 4.6%, 6.9%, and 11.6%.  
Figure 11: Power data corresponding to different pitch angles.  
Figure 10: Flight data at different pitch angles.  
The right boundary of the flight corridor of the vertical take-off and landing fixed-wing UAV is determined by the deflection angle-speed envelope of the power-based ducted lift-increasing system, thus reducing the required power of the flight state or increasing the available power of the flight system. It is possible to change the deflection angle-speed envelope of the ducted lift-increasing system. Figure 14 shows the deflection angle-speed envelope of the ducted lift-increasing system based on power after increasing the available power by 10% and 20%. It can be seen that as the available power increases, the power-based ducted lift-increasing system's deflection angle-speed envelope moves to the right, thus expanding the flight corridor boundary. It is calculated that the flight envelope expands by 21% and 40%. As shown in Figures 13 and 14, the effect of using the improvement in the overall parameters to expand the flight corridor is worse than using available power to expand the flight corridor under the same percentage. That is, the effect of using energy to expand the flight corridor is more significant than using the overall parameters. As the effect of the power parameters increased by 10% and that of the aerodynamic parameters also increased by 10%, it can be observed that increasing  
Figure 12: The influence of different deflection speeds on power. (**a**) Pull-force change curve of lift fan; (**b**) pull-force change curve of ducted lift-increasing system.  
Figure 13: The influence of aerodynamic parameters on the flight corridor. (**a**) Influence curve of wing area; (**b**) influence curve of maximum lift coefficient.  
the power can enlarge the transition corridor by 21%, while increasing the aerodynamic parameters can only expand the transition corridor by 4.6%.