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. [Figure 7-5] The lateral CG is determined in the same way as the longitudinal CG, except the distances between the scales and butt line zero (BL 0) are used as the arms. Arms to the right of BL 0 are positive and those to the left are negative. The BL 0 (sometimes referred to as the buttock) is a line through the symmetrical center of an aircraft from nose to tail. It serves as the datum for measuring the arms used to find the lateral CG. Lateral moments that cause the aircraft to rotate clockwise are positive (+), and those that cause it to rotate counterclockwise are negative (–). Arm (Station) The horizontal distance from the datum to any component of the helicopter or to any object located on the helicopter is called the “arm” or “station.” Moment If the weight of an object is multiplied by its arm, the result is known as its moment. Think of a moment as a force that results from an object’s weight acting at a distance. Moment is also referred to as the tendency of an object to rotate or pivot about a point. The farther an object is from a pivotal point, the greater its force. Weight and Balance Methods Discuss with the student the two different methods of obtaining the weight and balance of the helicopter: computational and loading chart. Computational Method The first method is the computational method, which uses simple mathematics to solve weight and balance problems. 1. Ascertain the total weight and total moment of the helicopter and ensure it does not exceed the maximum allowable weight under existing or forecast conditions. In this case, the total weight of the helicopter is under the maximum gross weight of 3,200 pounds. Tip: The empty weight CG can be considered the arm of the empty helicopter. Use care in recording the weight of each passenger and baggage. Recording each weight in its proper location is extremely important for the accurate calculation of a CG. 2. Now, divide the total moment by the total weight. This gives the CG of the loaded helicopter. The bottom of the chart in Figure lists the CG range for this particular helicopter. Take the CG figure and compare it to the allowable limits of 106.0 inches to 114.2 inches. The CG’s location of 109.9 inches is within the acceptable range. NOTE: If the CG falls outside the acceptable limits, adjust the loading of the helicopter. Weight Arm Moment (pounds) (inches) (lb-in) Basic Empty Weight 1,700 116.5 198,050 Oil 12 179.0 2,148 Pilot 190 65.0 12,350 Forward Passenger 170 65.0 11,050 Passengers Aft 510 104 53,040 Baggage 40 148 5,920 Fuel 553 120 66,360 Total 3,175 348,918 CG (loaded) 109.9109.9 Max Gross Weight = 3,200 lb CG Range = 106.0–114.2 inches If adjustments need to be made to the loading, refer the student to the Aircraft Weight and Balance Handbook, FAA-H-8083-1. Loading Chart Method The second method is the loading chart method. Three sample problems are given for this method. Take time to ensure the student fully understands the weight and balance concept and computations. Figure is an example of a loading chart. To use this chart, a pilot must: 1. Subtotal the empty weight, pilot, and passengers. This is the weight at which to enter the chart on the left. 2. The next step is to follow the upsloping lines for baggage and then for fuel to arrive at a final weight and CG. NOTE: Any value on or inside the envelope is within the range. Sample Problem 1 The student may not understand how or why the numbers are entered on the chart. (Explain the numbers to the student. Most manufacturers provide samples with their charts; figuring the charts out is a matter of inputting your own numbers.) The loading chart used in sample problems 1 and 2 is designed to calculate the loaded CG graphically and show whether it is within limits, all on a single chart. Determine if the gross weight and CG are within allowable limits under the following loading conditions for a helicopter based on the loading chart in Figure 7-7. To use the loading chart for the helicopter in this example, add up the items in a certain order. The maximum allowable gross weight is 1,600 pounds. NOTE: In Figure 7-7, the helicopter weights are located on the left side of the chart and the CG limits are located on the top of the chart. ITEM WEIGHT (LB) Basic empty weight 1,040 Pilot 135 Passenger 200 Subtotal 1,375 (point A) 1. Follow the green arrows in Figure 7-7. Enter the graph on the left side at 1,375 lb., the subtotal of the empty weight plus the pilot and passenger weights. Move right to Point A. Baggage compartment load 25 lb Subtotal 1,400 lb (Point B) 2. Move up and to the right, parallel to the baggage compartment loading lines to 1,400 lb (Point B). Fuel load (30 gallons) 180 lb Total weight 1,580 lb (Point C) 3. Continue up and to the right, this time parallel to the fuel loading lines, to the total weight of 1,580 lb (Point C). Point C is within allowable weight and CG limits. Sample Problem 2 Assume that the pilot in sample problem 1 discharges the passenger after using only 20 lb of fuel. ITEM WEIGHT (LB) Basic empty weight 1,040 Pilot 135 Subtotal 1,175 (Point D) 1. Follow the purple arrows in Figure 7-7, starting at 1,175 lb on the left side of the graph, then to Point D. Baggage compartment load 25 lb Subtotal 1,200 lb (Point E) 2. Continue to Point E. Fuel load 160 lb Total weight 1,360 lb (Point F) 3. Continue to Point F. |
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