直升机教员手册 Helicopter Instructor’s Handbook
时间：2014-11-10 08:35来源：FAA 作者：直升机翻译 点击：次
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To view this page ensure that Adobe Flash Player version 9.0.124 or greater is installed. Note the total weight of the helicopter is well below the maximum allowable gross weight; however, point F falls outside the aft allowable CG limit. As standard practice, compute the weight and balance with zero fuel to verify that a helicopter remains within the acceptable limits as fuel is used. It is imperative that weight and CG be within allowable limits for all phases of the flight or successive flights. Weight and CG change as loading configurations change; therefore, more than one weight and balance calculation needs to be accomplished. Initial calculations are based upon a fully loaded aircraft for the first takeoff; subsequent calculations address loading configuration changes, such as passenger drop off, fuel consumption and refueling. Addressing calculations for all projected loading configurations ensures that weight and CG remain within limits during all phases of the flight. Discuss with the student some options he or she could use in order to fix the out-of-CG condition. Sample Problem 3 Calculate moments for each station. ITEM WEIGHT (LB) MOMENT Basic empty 1,102 10.8 Pilot and front passenger* 340 28.3 Fuel* 211 22.9 Baggage 0 0 180 170 Total 1,653 162.0 Basic Empty Weight Pilot and Front Passenger Fuel Baggage Total Weight (lb) 1,102 340 211 1,650 Moment (lb-in/1,000) 110.8 28.3 22.9 162.0 *Use chart in Figure 7-8. 1.Record the basic empty weight and moment. 2.Record the weights of the pilot, passengers, fuel, and baggage on a weight and balance worksheet. 3.Determine the total weight of the helicopter. 4.Determine if the helicopter weight is within limits. (load limit on bottom of chart in Figure 7-9) Load Moment 1/1,000 (lb-in) 160 150 140 130 120 110 100 5. Determine the moments for a pilot and passenger (340 1,100 1,200 1,300 1,400 1,500 1,600 1,700 lb) and fuel (211 lb). [Figure 7-8] Load Weight (lb) to intersect the moment scale and read the fuel moment (22.9 thousand lb-in). 7. Do the same for the pilot/passenger moment. Draw a line from a weight of 340 lb up to the line labeled “Pilot & passenger—station 83.2.” Go left and read the pilot/passenger moment (28.3 thousand lb-in). 8. After recording the basic empty weight and moment of the helicopter and the weight and moment for each item, total and record all weights and moments. 9. Plot the calculated takeoff weight and moment on the sample moment envelope graph. Based on a weight of 1,653 lb and a moment/1,000 of 162 lb-in, the helicopter is within the prescribed CG limits. NOTE: Reduction factors are often used to reduce the size of large numbers to manageable levels. In Figure 7-8, the scale on the loading graph gives moments in thousands of pound-inches. In most cases, when using this type of chart, a pilot need not be concerned with reduction factors because the CG/moment envelope chart normally uses the same reduction factor. [Figure 7-9] Combination Method Figure 7-8. Moments for fuel, pilot, and passenger. The combination method usually uses the computation method to determine the moments and CG. Then, these 6. Using Figure 7-8, start at the bottom scale labeled figures are plotted on a graph to determine if they intersect load weight. Draw a line from 211 lb up to the line within the acceptable envelope. labeled “Fuel—station 108.5.” Draw a line to the left The example in Figure illustrates that with a total weight of 2,399 pounds and a total moment of 225,022 lb-in, the CG is 93.8. Plotting this CG against the weight indicates that the helicopter is loaded within the longitudinal limits (Point A). Calculating Lateral CG Some helicopter manufacturers require that pilots also determine the lateral CG limits. Lateral balance of an airplane is usually of little concern and is not normally calculated. But some helicopters, especially those equipped for hoist operations, are sensitive to the lateral position of the CG, and the Pilot’s Operating Handbook (POH) includes both longitudinal and lateral CG envelopes, as well as information on the maximum permissible host load. These calculations are similar to longitudinal calculations. However, since the lateral CG datum line is almost always defined as the center of the helicopter, a pilot is likely to encounter negative CGs and moments in the calculations. Negative values are located on the left side while positive stations are located on the right. When completing the steps below to calculate lateral CG, refer to Figure 7-11. 1. When computing moment for the pilot, 170 lb is multiplied by the arm of 12.2 inches, resulting in a moment of 2,074 lb-in. As with any weight placed right of the aircraft centerline, the moment is expressed as a positive value. Weight (pounds) Lateral Arm (inches) Moment (lb-in) Basic Empty Weight 1,400 0 0 Pilot 170 12.2 2,074 Fwd Passenger 250 .10.4 .2,600 Right Fwd Baggage 11.5 0 Left Fwd Baggage .11.5 0 Right Aft Passenger 12.2 0 Left Aft Passenger 185 .12.2 .2,257 Right Aft Baggage 50 12.2 610 Left Aft Baggage 50 .12.2 .610 Totals with Zero Fuel 2,105 .2,783 Main Fuel Tank Aux Fuel Tank Totals with Fuel CG 184 110 2,399 .13.5 13 .2,484 1,430 .3,837 .1.6.1.6 Figure 7-11. Computed lateral CG. 2. The forward passenger sits left of the aircraft centerline. To compute this moment, multiply 250 lb by –10.4 inches. The result is a moment of –2,600 lb-in. 3. Once the aircraft is completely loaded, the weights and moments are totaled and the CG is computed. Since more weight is located left of the aircraft centerline, the resulting total moment is –3,837 lb-in. To calculate CG, divide –3,837 lb-in by the total weight of 2,399 lb. The result is –1.6 inches, or a CG that is 1.6 inches left of the aircraft centerline. |
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