Weight and Balance

weight and balance calculation based on that table. In this Item Weight Arm Moment problem, the total weight of 2,799 pounds and moment of Basic empty weight 3,23 0 CG 90.5 292,315.0 2,278/100 are within the limits of the table. Front seat occupants 335 89.0 29,815.0 3rd & 4th seat occupants 350 126.0 44,100.0 Computations With a Negative Arm forward facing Figure 10-10 is a sample of weight and balance computation 5th & 6th seat occupants 200 157.0 31,400.0 Nose baggage 100 10.0 1,000.0 using an aircraft with a negative arm. It is important to Aft baggage 25 183.0 4,575.0 remember that a positive times a negative equals a negative, Zero fuel weight max 4,400 pounds Subtotal 4,240 CG 95.1 403,205.0 and a negative would be subtracted from the total moments. Fuel 822 113.0 92,886.0 Ramp weight max 5,224 pounds Computations With Zero Fuel Weight Subtotal ramp weight 5,062 CG 98.0 496,091.0 Figure 10-11 is a sample of weight and balance computation * Less fuel for start, taxi, and takeoff −24 113.0 −2,712.0 using an aircraft with a zero fuel weight. In this example, Subtotal the total weight of the aircraft less fuel is 4,240 pounds, takeoff weight 5,038 CG 97.9 493,379.0 which is under the zero fuel weight of 4,400 pounds. If the Less fuel to destination −450 113. 0 −50,850.0 Max landing weight 4,940 pounds total weight of the aircraft without fuel had exceeded 4,400 Actual landing weight 4,588 CG 96.5 442,529.0 pounds, passengers or cargo would have needed to be reduced *Fuel for start, taxi, and takeoff is normally 24 pounds. to bring the weight at or below the max zero fuel weight. Figure 10-11. Sample weight and balance using an aircraft with a published zero fuel weight. Shifting, Adding, and Removing Weight A pilot must be able to solve any problems accurately that aircraft have forward and aft baggage compartments, weight involve the shift, addition, or removal of weight. For example, may be shifted from one to the other to change the CG. If the pilot may load the aircraft within the allowable takeoff starting with a known aircraft weight, CG, and total moments, weight limit, then find that the CG limit has been exceeded. calculate the new CG (after the weight shift) by dividing the The most satisfactory solution to this problem is to shift new total moments by the total aircraft weight. baggage, passengers, or both. The pilot should be able to determine the minimum load shift needed to make the aircraft To determine the new total moments, find out how many safe for flight. Pilots should be able to determine if shifting a moments are gained or lost when the weight is shifted. load to a new location will correct an out-of-limit condition. Assume that 100 pounds has been shifted from station 30 to There are some standardized calculations that can help make station 150. This movement increases the total moments of these determinations. the aircraft by 12,000 in-lb. Weight Shifting Moment when When weight is shifted from one location to another, the at station 150 = 100 lb x 150 in = 15,000 in-lb total weight of the aircraft is unchanged. The total moments, however, do change in relation and proportion to the Moment when direction and distance the weight is moved. When weight is at station 30 = 100 lb x 30 in = 3,000 in-lb moved forward, the total moments decrease; when weight is moved aft, total moments increase. The moment change Moment change = [15,000 – 3,000] = 12,000 in-lb is proportional to the amount of weight moved. Since many By adding the moment change to the original moment (or subtracting if the weight has been moved forward instead of Item Weight Arm Moment aft), the new total moments are obtained. Then determine the Licensed empty weight 1,011.9 68.6 69,393.0 new CG by dividing the new moments by the total weight: Oil (6 quarts) 11.0 −31.0 −341.0 Fuel (18 gallons) 108.0 84.0 9,072.0 Fuel, auxiliary (18 gallons) 108.0 84.0 9,072.0 Total moments = Pilot 170.0 81.0 13,770.0 616,000 in-lb + 12,000 in-lb = 628,000 in-lb Passenger 170.0 81.0 13,770.0 Baggage 70.0 105.0 7,350.0 628,000 in-lb CG = = 78.5 in 8,000 lb Total 1,648.9 122,086.0 CG 74.0 The shift has caused the CG to shift to station 78.5. Figure 10-10. Sample weight and balance using a negative. 10-10