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. Hovering Learning to hover can be a frustrating experience for some students as it may take a few flights to learn the maneuver. Instructors should emphasize that the student should relax. Hovering is very difficult at first, but it does work and its importance cannot be overemphasized. Vertical Takeoff to a Hover and Hovering Prior to ascending to a hover, teach the student to always check for unreleased tiedowns or restrictions to the freedom of the landing gear. Pilots should always take off to a hover slowly to avoid dynamic rollover accidents from hung landing gear. A slow takeoff also gives the pilot more time to adjust for the translating tendency, making the takeoff smoother and more controlled. Explain to the student that a vertical takeoff to a hover involves flying the helicopter from the ground vertically to a landing gear height of two to four feet, while maintaining a constant heading. Demonstrate various hovering heights and allow the student to see how a hover at each height appears. [Figure 10-4] Once the desired landing gear height is achieved, the helicopter should remain nearly motionless over a reference point at a constant altitude and on a constant heading. The maneuver requires a high degree of concentration and coordination. Instructional Points Prior to any takeoff or maneuver, have the student ensure the area is clear of other traffic, persons, equipment or obstacles. This can be accomplished by instilling the habit of clearing the helicopter to the left, right, and overhead prior to performing any maneuver. One additional instructional point to make is to teach the student to assess the helicopter control response prior to each flight. Have the student get the helicopter light on the skids/ gear and ensure the helicopter ascends to a hover in a nearly level attitude. Ensure that you have enough cyclic control to continue. Once at a three-foot hover, ensure the helicopter remains nearly level. Point out to the student what a normal hover attitude looks like. If things do not feel or look right, slowly lower the collective and land the helicopter. Attempt RUNWAY 23L RUNWAY23L Figure 10-4.Vertical cues. Note the relative difference vertically between the top and bottom edges of the sign and things behind it, or the vertical distance between the sign and the edge of the runway. to determine why the helicopter is responding in such a way. Adjustment or reduction of load may be necessary. To begin the maneuver, head the helicopter into the wind, if possible. Place the cyclic in the neutral position with the collective in the full down position. Increase the throttle smoothly to obtain and maintain proper revolutions per minute (rpm), then slowly raise the collective. Emphasize a smooth, continuous movement, coordinating the throttle to maintain proper rpm. As the collective is increased, the helicopter becomes light on the landing gear, and torque tends to cause the nose to swing or yaw to the right unless sufficient left antitorque pedal is used to maintain heading. (On helicopters with a clockwise main rotor system, the yaw is to the left and right pedal must be applied.) As the helicopter becomes light on the landing gear, cyclic pitch control adjustments are necessary to maintain a level attitude. Unless the helicopter design compensates, translating tendency requires constant left cyclic in helicopters with counterclockwise rotating main rotor blades. Many helicopters are designed to hover in a left-landing-gear-low attitude to correct for right drift. NOTE: When the term “level attitude” is used during hovering flight, it is in reference to the helicopter remaining stationary without excessive tilt of the fuselage. Each helicopter tends to hover at some attitude that may not be exactly level or parallel with the surface. Translating tendency, winds, and weight and balance all contribute to the fuselage hanging at some off angle to the surface. When the tailrotor is under the plane of the main rotor disk, the fuselage is titled to stop the travel induced by the lateral tail rotor thrust counteracting the rotor torque. When the manufacturer designs the helicopter with an elevated tailrotor, which places the antitorque in the same plane as the main rotor torque, the fuselage tilt is much less in calm wind conditions. If enough wind is blowing from the opposite direction, the helicopter deck or cabin floor may be level or parallel to the surface, as the cross wind pushes on the side of the fuselage. However, if the wind is blowing from the other side, the deck tilt angle is increased because the rotor must develop sufficient thrust to counteract the tail rotor thrust and the crosswind to maintain position over the surface. If the helicopter only has a single, lightweight pilot aboard, the fore and aft deck or cabin floor angle is probably pitched nose-up compared to having two heavy pilots up front with no other loading. Depending on the helicopter, unloading one person can result in a 12 percent change in gross weight and a corresponding change in pitch. Helicopters usually hover in a normal attitude for that helicopter in that wind condition under that load condition. The student should be taught what the normal attitude for hovering is for the particular helicopter that they are flying. When airborne, at a hover, antitorque pedals are used to maintain heading and directional control while application of collective ensures continuous vertical ascent to the normal hovering altitude. When hovering altitude is reached, use the throttle and collective to control altitude, the cyclic to maintain a stationary hover, and the antitorque pedals to maintain heading. Initially, the student will probably overcontrol the helicopter. Excessive movement of any flight control requires a change in the other flight controls. For example, if the helicopter drifts to one side while hovering, a student naturally moves the cyclic in the opposite direction. When this is done, part of the vertical thrust is diverted, resulting in a loss of altitude. To maintain altitude, the student must increase the collective. This increases drag on the blades and tends to slow them. To counteract the drag and maintain rpm, the throttle needs to be increased. Because torque increases, the student must add more pedal pressure to maintain the heading. This can easily lead to overcontrolling the helicopter. However, as the student’s level of proficiency increases, problems associated with overcontrolling decrease. |
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