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. With small helicopters, it is generally unnecessary to determine the lateral CG for normal flight instruction and passenger flights. The cabins are relatively narrow and most optional equipment is located near the centerline. If there is an unusual situation that could affect the lateral CG, such as a heavy pilot and a full load of fuel on one side of the helicopter, its position should be checked against the CG envelope. Certain types of helicopters require a pilot to verify the lateral balance often, such as external hoist operations (hoist located on the side of the helicopter). Helicopter engineers determine the amount of cyclic control that is available. They establish both the longitudinal and lateral CG envelopes. This allows the pilot to load the helicopter and still have sufficient cyclic control for all flight conditions. Operating the helicopter outside these limits is inadvisable and control of the helicopter may not be possible in some conditions. Ballast Ballast is some form of weight placed in a specific location in an aircraft intended to maintain the CG within limits by compensating for unfavorable weight and balance conditions, thereby ensuring correct control margins. Two types are permanent ballast and temporary ballast. 1. Permanent ballast—the removal or addition of equipment to the helicopter has an effect on aircraft weight and balance. It may be necessary to install ballast weights to maintain the CG position within the CG limits. 2. Temporary ballast—such weights that may be necessary to compensate for missing crewmembers or equipment in order to maintain CG position. The amount and location of temporary ballast required to maintain safe flight is determined by the pilot or the airframe and powerplant (A&P) mechanics. Ensure that any ballast is properly secured or strapped down to prevent movement. When ballast moves, it compounds the CG problem instead of relieving it. Weight and Balance Calculations To determine whether a helicopter is properly loaded, ask the following questions: 1. Is the gross weight less than or equal to the maximum allowable gross weight? Answer: Add the weights of the items comprising the useful load to the basic empty weight of the helicopter (pilot, passengers, fuel, oil (if applicable), cargo, and baggage). 2. Is the CG within the allowable CG range, and will it stay within the allowable range throughout the duration of flight including all loading configurations that may be encountered? Answer: Use CG or moment information from loading charts, tables, or graphs in the RFM. Then using one of the methods described below, calculate the loaded moment and/or loaded CG and verify that it falls within the allowable CG range shown in the RFM. NOTE: Discuss with the student which direction the CG shifts as fuel is burned. On some helicopters, the fuel tanks are behind the CG, causing it to shift forward as fuel is used. Under some flight conditions, the balance may shift enough that there is not sufficient cyclic authority to flare for landing. For these helicopters, the loaded CG should be computed for both takeoff and landing weights. Use CG or moment information from loading charts, tables, or graphs in the Rotorcraft Flight Manual (RFM). Calculate the loaded moment and/or loaded CG and verify that it falls within the allowable CG range shown in the RFM. It is important to note that any weight and balance computation is only as accurate as the information provided. Therefore, determine passenger weight and add a few pounds to account for the additional weight of clothing, especially during the winter months. The baggage weight should be weighed on a scale, if practical. If a scale is not available, compute personal loading values according to each individual estimate. Weight Versus Aircraft Performance Overloading an aircraft may cause structural failure or result in reduced engine and airframe life. An increase in gross weight has the following effects on aircraft performance: a. Increases takeoff distance b. Reduces hover performance c. Reduces rate of climb d. Reduces cruising speed e. Reduces maneuverability f. Reduces ceiling g. Reduces range h. Increases landing distances NOTE: Ensure that the student understands the importance of not overloading the helicopter (operating at maximum weights) and also understands how the helicopters weight versus performance is also affected. Accurate performance planning based on current and forecast environmental conditions is critical in determining the helicopter’s actual maximum operational weight for any given set of conditions operating fluids. Reference Datum Figure indicates some of the different locations of the horizontal reference datum. Balance is determined by the location of the CG, which is usually described as a given number of inches from the reference datum. The horizontal reference datum is an imaginary vertical plane or point arbitrarily fixed somewhere along the longitudinal axis of the helicopter from which all horizontal distances are measured for weight and balance purposes. There is no fixed rule for its location; it may be located at the rotor mast, the nose of the Figure 7-4. While the horizontal reference datum can be anywhere the manufacturer chooses, some manufacturers choose the datum line at or ahead of the most forward structural point on the helicopter, in which case all moments are positive. This aids in simplifying calculations. Other manufacturers choose the datum line at some point in the middle of the helicopter, in which case moments produced by weight in front of the datum are negative and moments produced by weight aft of the datum are positive. helicopter, or even at a point in space ahead of the helicopter. The lateral reference datum is usually located at the center of the helicopter. The location of the reference datum is established by the manufacturer and is defined in the RFM. |
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