直升機教員手冊 Helicopter Instructor’s Handbook
時間：2014-11-10 08:35來源：FAA 作者：直升機翻譯 點擊：次
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To view this page ensure that Adobe Flash Player version 9.0.124 or greater is installed. Visually clear the area all around and above. Start the helicopter moving by smoothly and slowly easing the cyclic forward. As the helicopter starts to move forward, increase the collective as necessary to prevent the helicopter from sinking and adjust the throttle to maintain rpm. The sink is caused by diverting lift into forward thrust. Discuss with the student the aerodynamic effects of the rotor system during hovering flight and during normal takeoff. The increase in power requires an increase in the proper antitorque pedal to maintain heading. Emphasis should be placed on aligning landing gear precisely with the direction of travel to avoid dynamic rollover should the student allow the helicopter to touch the surface during takeoff. Select ground reference points to maintain a straight takeoff path throughout the takeoff. Ensure the student chooses several ground reference points during the maneuver to maintain a ground track. As the forward portion of the rotor system gains undisturbed air, the lift on the forward portion of the rotor tends to lift the front of the disk and stops the acceleration. A little forward cyclic to maintain the accelerating attitude is necessary to continue the takeoff. As the aft portion of the rotor system gains undisturbed air, the nose tends to tilt forward, causing an excessively fast acceleration. At about the same time, translational lift becomes apparent and some forward cyclic motion is required to gain sufficient airspeed to avoid the H/V chart shaded areas, while continuing a safe climb avoiding the shaded areas. As airspeed increases, the streamlining of the fuselage reduces engine torque effect, requiring a gradual reduction of antitorque pedal pressure. Just as translational lift occurs, translational thrust follows. This gives two effects that must be countered by adjusting the pedals as the climb begins. As the helicopter continues to climb and accelerate to best rate of climb, apply aft cyclic pressure to raise the nose smoothly to the normal attitude. Ensure that the student understands that he or she must make constant corrections during all phases of flight (this is to compensate for actions and reactions). Crosswind Considerations During Takeoffs When the takeoff is made during crosswind conditions, the helicopter is flown in a slip during early stages of the maneuver. In this case, the cyclic is held into the wind a sufficient amount to maintain the desired ground track for the takeoff. The heading is maintained with the use of the antitorque pedals. In other words, the rotor is tilted into the wind so the sideward movement of the helicopter is just enough to counteract the crosswind effect. To prevent the nose from turning in the direction of the rotor tilt, it is necessary to increase the antitorque pedal pressure on the side opposite the rotor tilt. After approximately 50 feet of altitude is gained, crab the helicopter into the wind as necessary to maintain coordinated flight over the desired ground track. The stronger the crosswind, the more the helicopter has to be turned into the wind. Common Student Difficulties Attitude Control As in most other maneuvers, smooth, positive attitude control is the key to success in the takeoff. If the student is properly briefed and understands the changing forces during takeoff, it is possible to anticipate and correct deviations promptly. At about five knots, ground effect diminishes and a helicopter begins to sink. Depending on available power and instructor technique, power should be added to prevent this sink. Any power change requires an antitorque pedal adjustment, which in turn requires a cyclic adjustment to accommodate the increased translating tendency. If the student does not make these adjustments, the ground track will not be straight. Shortly after forward movement is initiated, translational lift is encountered and the nose pitches. This requires forward cyclic to keep the helicopter accelerating. Heading Control Pedal control requirements also change during the transition into a climb. From the hover, additional power is added in helicopters with counterclockwise main rotor blade rotation, the left pedal requirement increases. As speed increases, directional stability increases, so the need for left pedal decreases. The tail rotor achieves translational thrust due to clean airflow and begins making more antitorque thrust than is required, especially if the helicopter has an effective vertical fin that also helps with the antitorque task. These actions require a decrease in antitorque pedal to maintain heading. A throttle change may be necessary since the power demand from the tail rotor decreases. A governor hides this control change. Crosswind Corrections If the takeoff is made in a crosswind condition, the student may not be aware of the corrections required during the climb unless briefed in advance. In the hover and during the initial portion of the climb, cyclic must be applied toward the wind, and downwind, pedal applied to keep the helicopter heading straight along the ground track. As speed and altitude are gained, the cyclic is used to establish a crab. As the helicopter is placed into a crab, the antitorque pedal pressure must be decreased from the slip into coordinated or “trimmed” flight. Failure to correct for the crosswind results in a downwind drift from the specified ground track. After the helicopter has transitioned through effective translational lift (ETL), the student should begin to crab the helicopter (trim), improving the climb performance. Once the desired or required climb airspeed is attained, the cyclic should be adjusted to maintain the stabilized airspeed attitude. Recommend using slip to align the fuselage with the ground track below approximately 50 feet, and trim the helicopter above 50 feet. Traffic The student may concentrate so completely on achieving the stated objectives that conflicting traffic and obstructions, such as towers and powerlines, go unnoticed. Instructing students to look well ahead of the helicopter and to scan for traffic not only helps their awareness of other traffic, but also helps improve attitude control. |
