Effects of Weight  change that takes place. As fuel is used, an aircraft becomes  lighter and performance is improved.  Any item aboard an aircraft that increases the total weight is  undesirable for performance. Manufacturers attempt to make  an aircraft as light as possible without sacrificing strength  or safety.  Changes of fixed equipment have a major effect upon the  weight of an aircraft. The installation of extra radios or  instruments, as well as repairs or modifications, may also  affect the weight of an aircraft.  The pilot should always be aware of the consequences of  overloading. An overloaded aircraft may not be able to leave  the ground, or if it does become airborne, it may exhibit  unexpected and unusually poor flight characteristics. If not  properly loaded, the initial indication of poor performance  usually takes place during takeoff.  Balance refers to the location of the CG of an aircraft, and is  important to stability and safety in flight. The CG is a point  at which the aircraft would balance if it were suspended at  that point.  Excessive weight reduces the flight performance in almost  every respect. For example, the most important performance  deficiencies of an overloaded aircraft are:  The primary concern in balancing an aircraft is the fore  and aft location of the CG along the longitudinal axis. The  CG is not necessarily a fixed point; its location depends on  the distribution of weight in the aircraft. As variable load  items are shifted or expended, there is a resultant shift in  CG location. The distance between the forward and back  limits for the position of the center for gravity or CG range  is certified for an aircraft by the manufacturer. The pilot  should realize that if the CG is displaced too far forward  on the longitudinal axis, a nose-heavy condition will  result. Conversely, if the CG is displaced too far aft on the  longitudinal axis, a tail heavy condition results. It is possible  that the pilot could not control the aircraft if the CG location  produced an unstable condition.  [Figure 10-1]  Location of the CG with reference to the lateral axis is also  important. For each item of weight existing to the left of  The pilot must be knowledgeable about the effect of weight  on the performance of the particular aircraft being flown.  Preflight planning should include a check of performance  charts to determine if the aircraft’s weight may contribute  to hazardous flight operations. Excessive weight in itself  reduces the safety margins available to the pilot and becomes  even more hazardous when other performance-reducing  factors are combined with excess weight. The pilot must  also consider the consequences of an overweight aircraft if  an emergency condition arises. If an engine fails on takeoff  or airframe ice forms at low altitude, it is usually too late to  reduce an aircraft’s weight to keep it in the air.  The operating weight of an aircraft can be changed by  simply altering the fuel load. Gasoline has considerable  weight—6 pounds per gallon. Thirty gallons of fuel may  weigh more than one passenger. If a pilot lowers airplane  weight by reducing fuel, the resulting decrease in the range  of the airplane must be taken into consideration during flight  planning. During flight, fuel burn is normally the only weight  10-2  Figure 10-1.  Lateral and longitudinal unbalance.  Balance, Stability, and Center of Gravity  Weight Changes  •  Higher takeoff speed  •  Longer takeoff run  •  Reduced rate and angle of climb  •  Lower maximum altitude  •  Shorter range  •  Reduced cruising speed  •  Reduced maneuverability  •  Higher stalling speed  •  Higher approach and landing speed  •  Longer landing roll  •  Excessive weight on the nose wheel or tail wheel  Lateral unbalance will cause wing heaviness.  Empty  Full  Excess baggage  Longitudinal unbalance will cause  either nose or tail heaviness. 