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After touchdown and after the helicopter has come to a complete stop, lower the collective pitch to the fulldown position. Do not try to stop the forward ground run with aft cyclic, as the main rotor blades can strike the tail boom. Rather, by lowering the collective slightly during the ground run, more weight is placed on the undercarriage, slowing the helicopter. COMMON ERRORS 1. Failing to use sufficient antitorque pedal when power is reduced. 2. Lowering the nose too abruptly when power is reduced, thus placing the helicopter in a dive. 3. Failing to maintain proper rotor r.p.m. during the descent. 4. Application of up-collective pitch at an excessive altitude resulting in a hard landing, loss of heading control, and possible damage to the tail rotor and to the main rotor blade stops. 5. Failing to level the helicopter. POWER RECOVERY FROM PRACTICE AUTOROTATION A power recovery is used to terminate practice autorotations at a point prior to actual touchdown. After the power recovery, a landing can be made or a go-around initiated. TECHNIQUE At approximately 8 to 15 feet above the ground, depending upon the helicopter being used, begin to level the helicopter with forward cyclic control. Avoid excessive nose high, tail low attitude below 10 feet. Just prior to achieving level attitude, with the nose still slightly up, coordinate upward collective pitch control with an increase in the throttle to join the needles at operating r.p.m. The throttle and collective pitch must be coordinated properly. If the throttle is increased too fast or too much, an engine overspeed can occur; if throttle is increased too slowly or too little in proportion to the increase in collective pitch, a loss of rotor r.p.m. results. Use sufficient collective pitch to stop the descent and coordinate proper antitorque pedal pressure to maintain heading. When a landing is to be made following the power recovery, bring the helicopter to a hover at normal hovering altitude and then descend to a landing. If a go-around is to be made, the cyclic control should be moved forward to resume forward flight. In transitioning from a practice autorotation to a go-around, exercise care to avoid an altitude-airspeed combination that would place the helicopter in an unsafe area of its height-velocity diagram. COMMON ERRORS 1. Initiating recovery too late, requiring a rapid application of controls, resulting in overcontrolling. 2. Failing to obtain and maintain a level attitude near the surface. 3. Failing to coordinate throttle and collective pitch properly, resulting in either an engine overspeed or a loss of r.p.m. 4. Failing to coordinate proper antitorque pedal with the increase in power AUTOROTATIONS WITH TURNS A turn, or a series of turns, can be made during an autorotation in order to land into the wind or avoid obstacles. The turn is usually made early so that the remainder of the autorotation is the same as a straight in autorotation. The most common types are 90° and 180° autorotations. The technique below describes a 180° autorotation. TECHNIQUE Establish the aircraft on downwind at recommended airspeed at 700 feet AGL, parallel to the touchdown area. In a no wind or headwind condition, establish the ground track approximately 200 feet away from the touchdown point. If a strong crosswind exists, it will be necessary to move your downwind leg closer or farther out. When abeam the intended touchdown point, reduce collective, and then split the needles. Apply proper antitorque pedal and cyclic to maintain proper attitude. Cross check attitude, trim, rotor r.p.m., and airspeed. After the descent and airspeed is established, roll into a 180° turn. For training, you should initially roll into a bank of a least 30°, but no more than 40°. Check your airspeed and rotor r.p.m. Throughout the turn, it is important to maintain the proper airspeed and keep the aircraft in trim. Changes in the aircraft’s attitude and the angle of bank cause a corresponding change in rotor r.p.m. Adjust the collective, as necessary, in the turn to maintain rotor r.p.m. in the green arc. At the 90° point, check the progress of your turn by glancing toward your landing area. Plan the second 90 degrees of turn to roll out on the centerline. If you are too close, decrease the bank angle; if too far out, increase the bank angle. Keep the helicopter in trim with antitorque pedals. The turn should be completed and the helicopter www.aero.cn 航空翻译 www.aviation.cn 本文链接地址：ROTORCRAFT FLYING HANDBOOK2
