 Longitudinal Axis— Roll WSC Unique Airfoil and Wing Design  Trim—Normal Stabilized Flight   High Angles of Attack  Vertical Axis— Yaw  Stability and Moments  Turning is initiated by rolling about the longitudinal axis, into  a bank similar to an airplane using aileron and rudder control.  To turn, shift the weight to the side in the direction of the turn,  increasing the weight on that side. This increases the twist on  that side while decreasing the twist on the other side, similar  to actuating the ailerons on an airplane. The increased twist  on the side with the increased weight reduces the AOA on the  tip, reducing the lift on that side and dropping the wing into a  bank. The other wing, away from which the weight has been  shifted, decreases twist. The AOA increases, increasing the  lift on that wing and thereby raising it.  Thus, shifting the weight to one side warps the wing (changes  the twist) to drop one wing and raise the other, rolling the  WSC aircraft about the longitudinal axis.  [Figure 2-24]  More  details on the controls that assist wing warping are covered  in chapter 3, which should be considered with use of the  controls in the takeoff, landing, and flight maneuvers sections  of this handbook.  The WSC wing is designed to fly directly into the relative  wind because it does not provide for direct control of rotation  about the vertical axis. A body that rotates freely turns about its CG. In aerodynamic  terms for a WSC aircraft, the mathematical value of a moment  is the product of the force times the distance from the CG  (moment arm) at which the force is applied. In  Figure 2-25B,  if the wing AOA is raised to the point of  minimum controlled airspeed at which the wing begins to  stall towards the center of the wing (root area), the lift in this  area decreases dramatically. The CLW moves back a distance  “b” creating a moment to lower the nose. Therefore, the  center of lift moves behind the CG at higher angles of attack,  creating a nose-down stabilizing moment. The average lift  coefficient verses AOA is shown for this minimum controlled  airspeed in  Figure 2-26.  The root area is partially stalled and  Adding all the lift from the wing puts the center of lift of  the wing (CLW) directly over the CG for stabilized fl ight.  [Figure 2-25A]  If the pilot wishes to increase the trim speed,  the CG is moved forward. This is done by moving the hang  point forward on the wing. Similarly, to reduce the trim speed,  the hang point/CG is moved rearward on the wing.  In  Figure 2-25A,  during normal unaccelerated flight at trim  speed, the lift at the root (L$_{R}$) times the arm to the root (A$_{R}$)  equals the lift of the tip (L$_{T}$) times the arm to the tip (A$_{T}$).  Additionally, the design of the complete wing is a unique  feature that provides stability without a tail. To understand the  WSC aircraft pitch stability and moments, examine the wing  as two separate components—root chord and tip chord.  As shown in  Figure 2-2,  the WSC airfoil has the high point  significantly farther forward than does the typical airplane  airfoil. This makes the center of lift for the airfoil farther  forward and creates a neutral or positive pitching moment  for the airfoil. Most WSC airfoils have this unique design to  minimize negative moments or pitch down during fl ight.  L$_{R}$ + L$_{T}$ = Total Lift of the Wing (L$_{W}$) The WSC wing is completely different and does not need a  tail because of two specific design differences—a completely  different airfoil design creating a more stable airfoil and  lifting surfaces fore and aft of the CG, similar to the airplane  canard design. Typical airplane wings generally pitch nose down or roll  forward and follow the curvature of the upper airfoil camber  creating a negative pitching moment. One of the reasons  airplanes have tails is to create a downward force at the  rear of the aircraft to maintain stabilized flight, as explained  in greater detail in the Pilot’s Handbook of Aeronautical  Knowledge.  (L$_{R}$  $^{x }$A$_{R}$ ) + (L$_{T}$  $^{x}$ A$_{T}$ ) = 0 W e i g h t s h i f t e d t o r $_{i}$g h t A i r c $_{r}$a f t r o l l s t o r i g h t Creates less twist on L.H.  side with tip increased AOA Normal lift distribution Less lift More lift Creates more twist on R.H.  side with tip reduced AOA Lift distribution with wing warped Figure 2-24. Shifting weight to one side warps the wing by  increasing the twist on the loaded side and decreasing the twist on  the unloaded side.  2-13