the aircraft must be reconfigured or placarded to prevent the  pilot from loading the aircraft improperly. It is sometimes  possible to install a fixed ballast in order for the aircraft to  operate again within the normal CG range. The  FAA-certifi cated mechanic or repairman conducting an  annual or condition inspection must ensure the weight and  balance data in the aircraft records is current and accurate. It  is the responsibility of the PIC to use the most current weight  and balance data when operating the aircraft. and control. If the CG is too far aft, it is too near the center  of lift; the airplane is unstable and difficult to recover from  a stall.  [Figure 1-2]  If the unstable airplane should enter a  spin, the spin could become flat making recovery difficult or impossible. If the CG is too far forward, the downward  tail load needs to be increased to maintain level flight. This  increased tail load has the same effect as carrying additional  weight; the aircraft must fly at a higher angle of attack and  drag increases. Balance control refers to the location of the CG of an aircraft.  This is of primary importance to aircraft stability, which is a  factor in flight safety. The CG is the point at which the total  weight of the aircraft is assumed to be concentrated, and the  CG must be located within specific limits for safe flight. Both  lateral and longitudinal balance are important, but the prime  concern is longitudinal balance; that is, the location of the  CG along the longitudinal or lengthwise axis. An airplane is designed to have stability that allows it to be  trimmed to maintain straight-and-level flight with hands off  the controls. Longitudinal stability is maintained by ensuring  the CG is slightly ahead of the center of lift. This produces a  fixed nose-down force independent of the airspeed. This is  balanced by a variable nose-up force, which is produced by a  downward aerodynamic force on the horizontal tail surfaces  A more serious problem caused by the CG being too far  forward is the lack of sufficient elevator authority. At low  takeoff speeds, the elevator might not produce enough  nose-up force to rotate; on landing there may not be enough  elevator force to flare the airplane.  [Figure 1-3]  Both takeoff  and landing runs are lengthened if the CG is too far forward. The basic aircraft design is such that lateral symmetry assumed to exist. For each item of weight added to the left  of the center line of the aircraft (also known as line zero or BL-0), there is generally an equal weight at a  corresponding location on the right. that varies directly with the airspeed.  [Figure 1-1] If a rising air current should cause the nose to pitch up, the  airplane slows and the downward force on the tail decreases.  The weight concentrated at the CG pulls the nose back down.  If the nose should drop in flight, the airspeed increases and  the increased downward tail load brings the nose back up  to level flight As long as the CG is maintained within the allowable limits  for its weight, the airplane has adequate longitudinal stability  The lateral balance can be upset by uneven fuel loading  or burnoff. The position of the lateral CG is not normally  computed for an airplane, but the pilot must be aware 1-4 Figure 1-3.  IftheCG is toofar forward, thereis notenoughelevator  nose-up force to flare the airplane for landing. Figure 1-1.  Longitudinal forces acting on an airplane in flight. Figure 1-2.  If the CG is too far aft at the low stall airspeed, there  might not be enough elevator nose-down authority to get the nose  down for recovery. Stability and Balance Control Lift Insufficient elevator Nose-down force CG too far aft CG Lift Variable Nose-up force dependent upon airspeed Fixed Nose-down force independent of airspeed CG Lift Insufficient elevator Nose-up force CG too far forward CG