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pull the control bar in to control pitch. This wing attachment is different for each manufacturer, but all designs have this hang point wing attachment so the control bar is always perpendicular to the longitudinal axis of the aircraft. This raising and lowering of the nose is the pitch control system for the WSC aircraft. [Figures 2-7 and  3-19] 

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##  Roll Control System 

Control bar movement from side to side controls the roll about the longitudinal axis. The wing attachment hang point allows the carriage to roll around the wing keel. Thus, it can also be looked at from the carriage point of view, when the control bar is moved side to side, the wing rotates around the wing keel relative to the carriage. [Figures 2-31 and  3-19] 

It would first appear that moving the control bar to one side, thus shifting weight to the opposite side, could alone bank the aircraft. It is true that shifting weight to the right would naturally bank the aircraft to the right and put it into a right hand turn. However, the weight alone is not enough to provide adequate roll control for practical fl ight. 

As weight is moved to one side, the keel is pulled closer to that side’s leading edge. The actual keel movement is limited to only 1 to 2 inches each side of center. However, this limited keel movement is sufficient to warp the wing, changing the twist side to side (as discussed earlier in the aerodynamics section) to roll the aircraft [Figure 2-24]  by changing the lift side to side. Simply, the shifting of weight from side to side pulls the keel toward the leading edge on that side and warps the wing to roll the aircraft. 

Besides the keel shifting relative to the leading edges and crossbar, overall roll control is adjusted by the designers to fit the mission of the wing through sail material/stiffness, leading edge stiffness/flexibility, amount of twist, amount of travel the keel is allowed, airfoil shape, and the planform of the wing. [Figures 3-20 and  3-21] 

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##  Trim Systems 

There are a number of trim systems to relieve the control pressures for pilots to fly at different “hands off” trim speeds. Ground adjustable trim allows the pilot to adjust the trim speed of the wing on the ground and remain at one speed during flight, while flight adjustable trim systems can change the trim speed in fl ight. 

##  Ground Adjustable Trim Systems 

The most common ground adjustable trim system, and typical of most aircraft, is moving the wing attachment hang point forward for faster trim speeds and aft for slower trim speeds. Each manufacturer has different hardware, but the basics of sliding the carriage wing hang point forward and backward on the keel is similar for all. As an example, moving the hang point at the furthest aft position to the furthest forward position could speed the wing up 20 knots. This in turn moves the control bar position back to a new “hands off” trim speed. 

