直升機(jī)教員手冊 Helicopter Instructor’s Handbook
時間：2014-11-10 08:35來源：FAA 作者：直升機(jī)翻譯 點(diǎn)擊：次
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To view this page ensure that Adobe Flash Player version 9.0.124 or greater is installed. After leveling off at an altitude between 25 and 40 feet, depending on the manufacturer’s recommendations, accelerate to the desired entry speed, which is approximately 45 knots for most training helicopters. The altitude chosen should be high enough to avoid danger to the tail rotor during the flare, but low enough to stay out of the crosshatched or shaded areas of the height/velocity diagram throughout the maneuver. In addition, this altitude should be low enough that the helicopter can be brought to hover during the recovery. Initiate the deceleration by applying aft cyclic to reduce forward speed and simultaneously lowering the collective, as necessary, to counteract any climbing tendency. Emphasize to the student that the timing must be exact. If too little down collective is applied for the amount of aft cyclic applied, a climb results. If too much down collective is applied, a descent results. A rapid application of aft cyclic requires an equally rapid application of down collective. As collective pitch is lowered, apply proper antitorque pedal pressure to maintain heading and adjust the throttle to maintain rpm. 2 34 1 Figure 11-3.Rapid deceleration or quick stop. As the speed dissipates, transition to a hover by lowering the nose and allowing the helicopter to descend to a normal hovering altitude in level flight and at zero groundspeed. During the recovery, increase collective pitch as necessary to stop the helicopter at normal hovering altitude, adjust the throttle to maintain rpm, and apply proper antitorque pedal pressure to maintain heading. Ensuring the student understands at all times where the tail rotor is relative to the ground is the key to success for this maneuver. As a teaching point prior to take off and, if the helicopter rpm allows (or consult maintenance), have the student sit in the helicopter and pull the tail boom down until the tail stinger or guard almost touches the surface. The student then gains the visual picture of the most nose-high attitude in which the helicopter needs to be in most situations. Common Student Difficulties Coordination Because the quick stop demands a high degree of coordination, the student may encounter difficulties during the initial attempts. All flight controls are used: the cyclic to establish the pitch attitude for the desired rate of deceleration, collective to control altitude, throttle to maintain rpm (if applicable), and antitorque pedals to control heading. Initial quick stops should be practiced with a gentle deceleration rate to reduce the amount of control required. As the student gains proficiency, steepness of the initial flare can be increased until full down collective is required to prevent an excessive gain in altitude. Recovery During the recovery, the helicopter should settle gently toward the hovering altitude. However, some students fail to recognize the need for recovery action and allow the helicopter to settle too rapidly as airspeed diminishes. Late application of collective requires an abrupt input to stop the rate of descent. As translational lift is lost and collective is increased, forward cyclic should be applied to return to a level attitude. In addition, as translational thrust is lost, even more antitorque pedal must be applied and more power produced to provide the antitorque. If stopping downwind, LTE could occur. Steep Approach to a Hover Steep approaches are practiced to simulate approaches to confined areas where obstacles make a normal approach impossible. Steeper approach angles are normally used to maintain obstacle clearance along the flightpath. After completing a high reconnaissance, the pilot begins the final leg approach at an altitude and angle (approximately 15°) that permits a continuous stabilized approach to the upper portion of the landing area to keep the tail rotor out of contact with other objects. This continuous approach allows the pilot to establish and maintain that angle throughout the approach. The pilot should be cautious of rapid rates of descent and should continually check the closure rate. Using this technique allows much more time to complete the low reconnaissance, thereby allowing more time and altitude to conduct a go-around if needed. It could terminate either in a stabilized hover about a designated spot or in a landing. [Figure 11-4] 1 2 15° Descent 3 4 Figure 11-4.Steep approach to a hover. Instructional Points On final approach, head the helicopter into the wind or approach path and align it with the intended touchdown point at the recommended approach airspeed. Begin the approach by intercepting an approach angle of approximately 15°, lowering the collective sufficiently to start the helicopter descending along the approach path, and decelerating. Any approach angle of greater than 15° increases the likelihood of encountering settling with power; therefore, make certain the pilot understands the purpose of a steep-approach angle is to ensure tail rotor clearance, and does not enter at an excessive angle. Use the proper antitorque pedal for trim. Since this angle is steeper than a normal approach angle, reduce the collective more than that required for normal approach and control the rate of descent. Continue to decelerate with slight aft cyclic, and smoothly lower the collective to maintain the approach angle. Remind the student to visualize the approach angle as an imaginary line from the landing gear to three feet above the landing point and attempt to maintain that angle throughout the maneuver. [Figure 11-5] Aft cyclic is required to decelerate sooner than on a normal approach, and the rate of closure becomes apparent at higher altitude. 1 2 3 4 3 foot hover into the wind Figure 11-5. Approach to a three foot hover over landing spot. Maintain the approach angle and rate of descent with the collective, rate of closure with the cyclic, and trim with antitorque pedals. Initially, use a crab above 50 feet and above the obstacles to compensate for wind. Use a slip below 50 feet for any crosswind that might be present. |
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