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. Entry Guide the student through the entry or first stage of autorotation and explain that this phase is entered after loss of engine power. The loss of engine power and rotor rpm are more pronounced when the helicopter is at high gross weight, high forward speed, or in high density altitude conditions. Any of these conditions demand increased power (high collective position) and a more abrupt reaction to loss of that power. In most helicopters, it takes only seconds for rpm decay to bring rpm to a minimum safe range, requiring a quick collective response from the pilot. The entry into autorotation must be immediate and smooth by lowering the collective, adjusting the pedals for the loss of torque, and adjusting the airspeed for the proper glide angle. The instructor should never initiate an autorotation, or simulated forced landing, unless there is suitable landing within glide distance in the event of a powerplant or drive line failure. Discuss with the student the airflow and force vectors for a blade in this configuration. Remind the student that lift and drag vectors are large and the total aerodynamic force (TAF) is inclined well to the rear of the axis of rotation. An engine failure in this mode causes rapid rotor rpm decay. Inform the student that to prevent this, a pilot must lower the collective quickly. Explain to the student that as the helicopter begins to descend, the airflow begins to flow upward and under the rotor system. Steady-State Descent Airflow is now upward through the rotor disk because of the descent. Once equilibrium is established, rate of descent and rotor rpm are stabilized, and the helicopter is descending at a constant angle. Angle of descent is normally 17° to 20°, depending on airspeed, density altitude, wind, and type of helicopter. The instructor should guide the student through any RFM procedures or charted values for minimum rates of descent versus maximum glide distance if provided for that helicopter. During this phase of the autorotation, the aircraft is maneuvered to reach a safe landing area by adjusting airspeed and making turns as appropriate while maintaining rotor rpm at the proper range for the type of helicopter. Checklist items are also completed as time permits and a Mayday call made. Explain to the student how the loss of engine power during the autorotation requires the pilot to use the pedal controls to keep the helicopter in trim throughout the descent until the deceleration and touchdown point is reached, otherwise the increased drag would greatly increase the rate of descent. Also explain how the fuselage tends to weathervane into the wind due to the vertical fin. Deceleration Explain to the student that to make an autorotative landing, the pilot reduces airspeed and rate of descent just before touchdown. Both actions can be partially accomplished by applying aft cyclic, which changes the attitude of the rotor disk in relation to the relative wind. During this maneuver, the goal of the pilot shifts from maintaining an airspeed to attaining a minimum ground speed for touchdown while decreasing the rate of descent. Ensure the student understands that this attitude change: . Inclines the lift vector of the rotor system to the rear, slowing forward speed. . Increased airflow results in increasing rpm, which must be controlled with the collective. . The lifting force of the rotor system is increased and rate of descent is reduced. . During this stage of the autorotation, the lack of torque is noticeable and the aircraft fuselage may rotate counterclockwise with application of the collective due to frictional drag in the transmission, drive train, associated pumps, and generators (depending on type of helicopter). Pedal application will be required to maintain a heading aligned with the touchdown area. Any crosswind also causes the nose to weathervane into the wind due to lift produced by the vertical fin. Touchdown During this final phase of the autorotation with the airspeed at a minimum as required for the conditions of the landing area, the cyclic stick is moved forward to place the aircraft in a landing attitude while applying collective pitch to cushion the landing. The height at which this phase is entered depends on the size of the helicopter and the length of the tailboom. The landing attitude varies between helicopter designs from touching the aft portion of the landing gear first as in an airplane, to a level attitude with all surfaces touching down at once. Each manufacturer has a preferred landing attitude that must be used to. Heading control must be maintained with the pedals to preclude the aircraft from rolling over once ground contact is made. The instructor must ensure several conditions are met to allow the helicopter to arrive at this point: 1. The rate of descent, rotor rpm, and airspeed are all within established parameters, as well as landing area alignment and positioning. If any of these conditions are not within limits, re-engage the engine and make a power recovery or go-around. 2. The landing gear is and stays aligned with the ground track of the helicopter. 3. The decelerating flare did not result in an increase in altitude (ballooning) or was not begun at too high of an altitude. 4. The student cannot be allowed to increase the collective too soon, and the student must be prompted to use available collective to cushion the landing soon enough. 5. The collective must be used to cushion the touchdown, but the student should not be allowed to hold the helicopter off the surface. 6. The student must not be allowed to retain an excessive decelerating attitude at too low an altitude allowing a tailboom or tail rotor strike. The student must be taught how to begin the flare and then decrease the nose high attitude to a landing attitude. 7. The student cannot be allowed to move the cyclic aft after touchdown. This generally allows the rotor blades to dip aft over the tailboom and when occurring at the same time as the actual touchdown, results in a tailboom strike. |
