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. Another exercise that develops smoothness and coordination is rolling from a medium bank to the left into a medium bank to the right, then back to the left and continuing the series while maintaining a constant base heading and altitude. Each of these exercises helps develop smoothness, coordination, and an active scan pattern. If a student is having trouble coordinating rpm and manifold pressure, an exercise in throttle/collective coordination can be used. Have the student maintain a constant attitude while disregarding altitude. Now, instruct the student to change the manifold pressure with the collective while holding a constant rpm with the throttle. Then, reverse the procedure by having the student change the rpm with the throttle while maintaining a constant manifold pressure with the collective. This exercise allows the student to concentrate on throttle/ collective coordination without devoting attention to other factors. Approaches An approach is defined as the transition from traffic pattern altitude to either a hover or to the surface. In day-to-day operations, approaches in a helicopter may be dictated more by existing conditions than by formal patterns. For training, however, a formal pattern is used to give the student a basis upon which to build the modified patterns a particular situation may require. Downwind, base, and final approach legs should be flown in accordance with the patterns the instructor outlines. A normal approach uses a descent profile of 8°–12° starting at approximately 300 feet AGL. [Figure 10-3] The rectangular pattern explained on page serves as a good basis for helicopter traffic pattern with the downwind at 500 feet AGL or higher as needed for noise, traffic and aircraft characteristics. Emphasize to the student that aligning with the landing direction may allow the pilot to detect winds sooner and detect obstructions. Flying any path that is less than straight into an area on the approach azimuth decreases the time available for hazard detection and low reconnaissance. Instructional Points For the beginning student, each approach should be started at approximately the same position and at the same airspeed and altitude. This allows a consistent basis for the student and instructor to evaluate each approach. To accomplish this, concentrate on each leg of the traffic pattern so the helicopter arrives at the point the approach is started and at the correct position, speed, and altitude. As the approach angle comes into view, begin the approach by lowering the collective sufficiently to get the helicopter descending down the approach angle. The approach angle should be an imaginary angle from the landing gear to the landing point, and not from the pilot’s eyes to the landing point. With the decrease in the collective, the nose tends to pitch down, requiring aft cyclic to maintain the recommended approach airspeed attitude. Adjust antitorque pedal as necessary to maintain yaw trim. Maintain entry airspeed until the apparent groundspeed and rate of closure appear to be increasing. At this point, slowly began decelerating with slight aft cyclic, and smoothly lower the collective to maintain approach angle. Use the cyclic to maintain an apparent rate of closure equivalent to a brisk walk. Explain to the student that a helicopter pilot should plan an approach to keep the skids/landing gear at a constant angle to a 3-foot hover over the intended landing area. Keeping the landing area in one spot in the windshield or “bubble” does not result in a good approach for a helicopter pilot. It is best for the pilot to visualize and fly the skids/landing gear down the approach angle to the hover point. At approximately 25–40 feet AGL, depending on wind, the helicopter begins to lose effective translational lift. To compensate for this loss, increase the collective to maintain the approach angle, while maintaining the proper rpm. The increase of collective pitch tends to make the nose rise, requiring forward cyclic to maintain the proper rate of closure. On short final, this is also when the airflow in the aft portion of the rotor disk is disturbed, so the increased pitch in the forward portion of the disk is not balanced by the same lift in the aft portion. Depending on the amount of deceleration used, forward cyclic may be needed to maintain the hovering position. As the helicopter approaches the recommended hover altitude, increase the collective sufficiently to maintain the hover. At the same time, apply aft cyclic to stop any forward movement, while controlling the heading with antitorque pedals. Common Student Difficulties Ground Track There can be no basis upon which to build unless the approach path is consistent. Therefore, the student must start the pattern from the same indicated airspeed, altitude, and distance from the landing spot. Thereafter, the student should be encouraged to maintain the correct pattern so each approach does not present a new set of circumstances. During initial training, explain to the student how different wind conditions can affect the helicopter and teach them how to adjust the flight controls so that they are always flying the helicopter rather than letting the helicopter take control of them. As the student gains experience, the instructor should have the student brief the effects of the winds on the expected flight maneuvers and what actions must be taken by the student to counteract those effects. Altitude The same comments concerning ground track are applicable to altitudes on downwind, base, and the turn to final approach. Changing altitude requires modifications in some other parameter, resulting in a different approach pattern. Therefore, turns to each leg of the approach should be made from the same spot and at the same altitude during a single training period. Airspeed Airspeed control is important if the student is to establish and maintain a consistent approach. Thus, it is important for the student to be aware of, and adhere to, recommended approach airspeeds. |
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