Weight and Balance

Effects of Weight change that takes place. As fuel is used, an aircraft becomes Any item aboard an aircraft that increases the total weight is lighter and performance is improved. undesirable for performance. Manufacturers attempt to make an aircraft as light as possible without sacrificing strength Changes of fixed equipment have a major effect upon the or safety. weight of an aircraft. The installation of extra radios or instruments, as well as repairs or modifications, may also The pilot should always be aware of the consequences of affect the weight of an aircraft. overloading. An overloaded aircraft may not be able to leave the ground, or if it does become airborne, it may exhibit Balance, Stability, and Center of Gravity unexpected and unusually poor flight characteristics. If not Balance refers to the location of the CG of an aircraft, and is properly loaded, the initial indication of poor performance important to stability and safety in flight. The CG is a point usually takes place during takeoff. 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 The primary concern in balancing an aircraft is the fore deficiencies of an overloaded aircraft are: and aft location of the CG along the longitudinal axis. The • Higher takeoff speed CG is not necessarily a fixed point; its location depends on the distribution of weight in the aircraft. As variable load • Longer takeoff run items are shifted or expended, there is a resultant shift in • Reduced rate and angle of climb CG location. The distance between the forward and back limits for the position of the center for gravity or CG range • Lower maximum altitude is certified for an aircraft by the manufacturer. The pilot • Shorter range should realize that if the CG is displaced too far forward • Reduced cruising speed on the longitudinal axis, a nose-heavy condition will result. Conversely, if the CG is displaced too far aft on the • Reduced maneuverability longitudinal axis, a tail heavy condition results. It is possible • Higher stalling speed that the pilot could not control the aircraft if the CG location • Higher approach and landing speed produced an unstable condition. [Figure 10-1] • Longer landing roll Location of the CG with reference to the lateral axis is also • Excessive weight on the nose wheel or tail wheel 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. Empty Full 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 Lateral unbalance will cause wing heaviness. 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 Excess baggage or airframe ice forms at low altitude, it is usually too late to reduce an aircraft’s weight to keep it in the air. Weight Changes 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 Longitudinal unbalance will cause weigh more than one passenger. If a pilot lowers airplane either nose or tail heaviness. weight by reducing fuel, the resulting decrease in the range of the airplane must be taken into consideration during flight Figure 10-1. Lateral and longitudinal unbalance. planning. During flight, fuel burn is normally the only weight 10-2