The flight controls primarily affect the pitch-and-roll axis. Since there is no vertical tail plane, minimal or no ability exists to directly control yaw. However, unlike the airplane, the center of gravity experienced by the wing remains constant. Since the weight of the airframe acts through the single point (wing attach point), the range over which the weight may act is fixed at the pendulum arm or length. Even though the weight decreases as fuel is consumed, the weight remains focused at the wing attach point. Most importantly, because the range is fixed, the need to establish a calculated range is not required. The powered parachute also belongs to the pendulumstyle aircraft. Its airframe center of gravity is fixed at the pendulum attach point. It is more limited in controllability than the WSC aircraft because it lacks an aerodynamic pitch control. Pitch (and lift) control is primarily a function of the power control. Increased power results in increased lift; cruise power amounts to level flight; decreased power causes a descent. Due to this characteristic, the aircraft is basically a one-air speed aircraft. Once again, because the center of gravity is fixed at the attach point to the wing, there can be no center of gravity range. Roll control on a powered parachute is achieved by changing the shape of the wing. The change is achieved by varying the length of steering lines attached to the outboard trailing edges of the wing. The trailing edge of the parachute is pulled down slightly on one side or the other to create increased drag along that side. This change in drag creates roll and yaw, permitting the aircraft to be steered. The balloon is controlled by the pilot only in the vertical dimension; this is in contrast to all other aircraft. He or she achieves this control through the use of lift and weight. Wind provides all other movement. The center of gravity of the gondola remains constant beneath the balloon envelope. As in WSC and powered-parachute aircraft, there is no center of gravity limitation. Aircraft can perform safely and achieve their designed efficiency only when they are operated and maintained in the way their designers intended. This safety and efficiency is determined to a large degree by holding the aircraft’s weight and balance parameters within the limits specified for its design. The remainder of this handbook describes the way in which this is done.