1-5 Figure 1-4.  Lateral imbalance causes wing heaviness, which may  be corrected by deflecting the aileron. The additional lift causes  additional drag, and the airplane flies inefficiently. Figure 1-5.  Fuel in the tanks of a swept-wing airplane affects both  lateral and longitudinal balance. As fuel is used from an outboard  tank, the CG shifts forward. the adverse effects that result from a laterally unbalanced  condition.  [Figure 1-4]  This is corrected by using the aileron  trim tab until enough fuel has been used from the tank on  the heavy side to balance the airplane. The deflected trim tab  deflects the aileron to produce additional lift on the heavy  side, but it also produces additional drag, and the airplane  flies inefficientl Helicopters are more often affected by lateral imbalance  than airplanes. If a helicopter is loaded with heavy occupants  and fuel on the same side, it could be out of balance enough  to make it unsafe to fly. It is also possible that if external  loads are carried in such a position that requires large lateral  displacement of the cyclic control to maintain level fl ght, the  fore-and-aft cyclic control effectiveness is limited. airplane requires an established weight and a known CG,  whereas the WSC aircraft only requires the known weight. The fixed-wing airplane has movable controls that alter lift  on various airfoil surfaces to vary pitch, roll, and yaw. In  turn, these changes in lift affect the characteristics of flight parameters. Weight normally decreases in flight due  to fuel consumption, and the airplane CG changes with this  weight reduction. An airplane utilizes its variable fligh controls to compensate and maintain controllability through  the various flight modes and as the CG changes. An airplane  has a CG range or envelope within which it must remain if  the flight controls are to remain effective and the airplane  safely operated. Swept-wing airplanes are more critical due to fuel imbalance  because as the fuel is used from the outboard tanks, the CG  shifts forward. As fuel is used from the inboard tanks, the CG  shifts aft.  [Figure 1-5]  For this reason, fuel-use scheduling  in swept-wing airplanes operation is critical. Some light aircraft utilize different methods of determining  weight and balance from the traditional fixed and rotor-wing  aircraft. These aircraft achieve flight control by methods  different from the fixed-wing airplane or helicopter. Most  notable of these are weight-shift control (WSC) aircraft (also  known as trikes), powered parachutes, and balloons. These  aircraft typically do not specify either an EWCG or a CG  range. They require only a certified or approved maximum  weight. To understand why this is so, a look at how flight control is achieved is helpful. Airplanes and WSC aircraft control flight under the influenc of the same four forces (lift, gravity, thrust, and drag), and  around the same three axes (pitch, yaw, and roll). However,  each aircraft accomplishes this control in a very different  manner. This difference helps explain why the fixed-wing The WSC aircraft has a relatively set platform wing without  a tail. The pilot achieves control by shifting weight. In the  design of this aircraft, the weight of the airframe and payload is attached to thewing atasinglepointin apendulous  arrangement. The pilot, through the  fl ight controls, controls the  arm of this pendulum and thereby controls the aircraft. When  a change in flight parameter is desired, the pilot displaces the  aircraft’s weight by the appropriate distance and direction.  This change momentarily disrupts the equilibrium between the  four forces acting on the aircraft. The wing, due to its inherent  stability, then moves appropriately to reestablish the desired  relationship between these forces; the wing flexes and alter its shape. As the shape is changed, lift is varied at different  points on the wing to achieve the desired flight parameters Weight-Shift Control Aircraft Weight Control for Aircraft Other Than  Fixed and Rotor-wing Empty Full Additional lift and drag Additional weight Inboard fuel:  nose heavy Outboard fuel:  tail heavy