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. As a teaching point, the instructor can locate a nearby visual approach slope indicator (VASI) and help the student look up the information on the VASI to determine the correct angle for running or roll-on landings. Most VASI glide slopes are set in the 3° range, so that would be a good sight picture for the beginning student when learning the approach angle. Common Student Difficulties Approach Angle The desired approach angle for a running landing is recommended to be approximately 2°–5°, somewhat shallower than a normal approach. The student may have difficulty visualizing and maintaining this approach angle and achieving the correct attitude, airspeed, and rate of descent on touchdown. Also, remember that sight pictures for students vary, as do aircraft design. It is possible the student has had previous instruction in another airframe or even a fixed wing aircraft. Attitude Control In order to achieve the desired airspeed at the proper altitude above the touchdown point, correct pitch attitude is vital throughout the approach and touchdown in a running landing. Initially, the helicopter must have a slightly decelerating attitude (nose up slightly); in the middle of the approach, more of a gliding neutral stabilized attitude may be required. Finally, as power must be increased to replace lift lost due to loss of ETL, the cyclic must be adjusted to obtain the landing attitude necessary to the landing gear to touchdown. As a teaching point, the instructor should have the student fly a restricted power go-around so the student gains the experience of the slow response under those conditions. Collective Control Collective should not be fully lowered until the helicopter has stopped. Students tend to lower the collective immediately after landing, as in a normal landing from a hover. Rapidly lowering the collective while the helicopter is still sliding results in a deceleration rate that can impose undue stress on the landing gear support, rotor mast, transmission, or supporting structure. Touchdown Common problems on touchdown include improper use of the collective and cyclic controls. Just prior to touchdown, there is a tendency to apply aft cyclic to cushion the landing. This causes the tail of the skids to touch first, followed by a forward pitching moment. A student may attempt to correct this action with more aft. In extreme cases, this can cause the main rotor blades to contact the tail boom. The correct technique is to level the helicopter, use collective to cushion the touchdown, and then apply a small amount of forward cyclic if needed after touchdown. Collective should be held to maintain a low rate of deceleration. These general procedures are for landings to a smooth hard surface. Procedures vary for other types of surfaces, which means that the amount of collective applied varies depending on the surface. The instructor should never hesitate to increase power and collective and terminate the maneuver if any parameter is being exceeded. Slope Operations Slope Landings While landing on a gentle slope is similar to landing in a crosswind, landing on a slope approaching the maximum capability of the helicopter requires smooth, yet positive, control. [Figure 11-7] Prior to flight, revisit the basics with the student prior to performing maximum angle slopes. Putting the right skid or wheel upslope allows greater lateral control due to translating tendency (counterclockwise rotating rotor systems). Conversely, a left skid/wheel upslope restricts the amount of lateral cyclic available. Depending on winds, discuss with the student that it is easier to land on the slope where the uphill side is to the right and the wind is coming from the downslope side. The student should also understand it is preferable to land the helicopter uphill from people so they can approach the helicopter from the downhill side. Approaching from the downhill side provides greater main rotor clearance between the rotor system and the downward sloping ground. Slope limitations vary from manufacturer to manufacturer. It is important to emphasize that personal, physical, or mechanical limits may be reached before manufacturer’s limits. Personal limits are reached when the pilot simply feels uncomfortable with continuing the approach. A pilot does not need to reach any of the other limits to get to this point. If it does not feel right to the student, abort the maneuver and try again. In the case of physical limits, it is possible the student will find the cyclic restricted by either a leg or a kneeboard. Perhaps in situations where dual controls are installed the pilot may make cyclic contact with the passenger’s leg or his/her own leg or kneeboard. In that case, abort the maneuver and find another location and/or reposition objects within the flight control area. The surface of the slope can also be a limiting factor. If the surface is gravel, skid landing gear may not rest on the slope without sliding. If the surface is damp grass, it may be too slick for the helicopter to stay on the slope. An icy slope may only be suitable for offloading or loading but not for a complete shutdown. A thorough visual assessment of the surface should always be done when possible before attempting to land on a slope. Mechanical limiting may occur if the aircraft rigging limit is preventing continuation of the maneuver. Mechanical resistance against the cyclic is felt. In this case, abort the maneuver, analyze the contributing factors, and reposition to another location, selecting a shallower slope. If, at any point during the slope landing the student feels uncomfortable, abort the landing and reposition to a location where the limiting factors can be eliminated. The limits of the helicopter’s capability are discernible before the helicopter is committed to landing, as long as the student proceeds slowly and remains alert for sliding or for the cyclic control approaching the lateral travel limits. Proper technique on a slope landing eliminates the risk of dynamic rollover or sliding downslope. |
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