Examination of Proverse Yaw in Bell-Shaped Spanload Aircraft

Recent developments in the bell-shaped spanload have shown the existence of proverse yaw control power via induced thrust at the wingtips. With no need for vertical control surfaces, new types of aircraft designs are possible. Via the use of traditional roll and proverse yaw control power, a lateral directional control space can be created for flying wings where no sweep is required for lateral directional stability and control. These straight tapered flying wings have increased efficiency and performance compared to traditional aircraft. In order to maintain stability and control, straight tapered flying wings require adequate proverse yaw control power. This paper investigated the connection between aircraft geometry and proverse yaw control power while applying the bell spanload. A straight tapered flying wing Biomimetic Aircraft was used for the initial aircraft geometry. By varying taper ratio, wing chord, wing length, twist distribution, and outboard wing control surface (OWCS) size, several relationships between aircraft geometry and proverse yaw control power are determined. Proverse yaw control power is a function of the change in lift over a region of upwash as well as the change in localized downwash. As the OWCS area increases due to larger chord lengths, proverse yaw control power increases. Additionally, increasing the region of upwash via a longer wingspan or twist distribution leads to improved proverse yaw control power. However, increasing the span fraction of the OWCS does not necessarily result in increased proverse yaw control power as it is tied to localized downwash. Varying the lift distribution due to an OWCS deflection can positively affect this downwash decreasing proverse yaw control power. The Biomimetic Aircraft with 10% more span and 10% more twist at the wingtips has 16 times more proverse yaw control power than the original Biomimetic Vehicle. With this increase in proverse yaw control power, straight tapered flying wings are controllable through all necessary flight regimes