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. Taxi Once a student has learned the basic skills required to hover the helicopter, those skills translate into the practical application of taxiing the helicopter. In order to accomplish this task the student should understand the terms used and the limitations placed on each action and the basic information and safety involved in selecting hover altitudes and speeds derived from the H/V chart. Hover Taxi The term hover taxi is used to describe a helicopter movement conducted above the surface and in ground effect at airspeeds less than approximately 20 knots. [Figure 10-10] The actual height may vary, and some helicopters may hover taxi above 25 feet above ground level (AGL) to reduce ground effect turbulence or provide clearance for cargo slingloads. Air Taxi The term air taxi describes helicopter movement conducted above the surface, but normally not above 100 feet AGL. [Figure 10-11] The helicopter may proceed either via hover taxi or flight at speeds more than 20 knots. The pilot is solely responsible for selecting a safe airspeed/altitude for the operation being conducted. Surface/Ground Taxi Taxi, surface taxi, or ground taxi is the movement of an aircraft under its own power actually in physical contact with the surface of an airport. It also describes the surface movement of helicopters equipped with wheels. [Figure 10-12] Figure 10-12. Surface taxi. Ground taxi can form the basis for a running takeoff used by older, underpowered helicopters. Ground taxi creates less downwash, since less thrust is required to slide the skids than to support the entire weight of the helicopter. Wheeled taxi is very efficient. Water or ski taxi is between those two extremes in terms of power required. Surface taxi includes ground contact taxiing with wheels, floats, skis, or skids. Ground contact requires less power than hover taxiing and produces less rotor wash, depending on the surface friction. If skis are stuck to the surface, it may take some power to break them loose. Surface taxi also provides an alternative method of taking off in white or brownout conditions by blowing the obstructing material behind the helicopter as some airspeed is reached and certainly by translational lift speed. Caution should be observed to prevent the landing gear from being stuck to the surface or striking something on the takeoff surface, leading to dynamic rollover. Surface taxi is not a common or preferred maneuver, but it has been used in certain situations, generally in much older, underpowered helicopters. Instructional Points For hover taxi, air taxi, and taxi, have the student review the Aeronautical Information Manual (AIM), paragraphs 4-and 7-5-13c. Prior to air taxi demonstration and practice, the instructor should review the H/V chart and have the student assist in planning or developing a safe air taxi profile of airspeeds versus altitudes. Since the AIM gives 100' AGL as the upper limit, the instructor should find 100'AGL on the chart and determine minimum and maximum airspeeds for the maneuver, remembering the helicopter requires power to decelerate and come to hover without translational lift and thrust. Discuss with the student the H/V chart to determine the safest flight profile that should be used during any taxi operation. The advantages of ground or surface taxi for skid-equipped helicopters should be discussed so the student will understand some criteria for deciding on their own when ground taxi is safer and the recommended maneuver for that occasion. Discuss with the student the H/V chart to determine the safest flight profile that should be used during any taxi operation. Ground Reference Maneuvers Ground reference maneuvers are training exercises that can be used to develop coordination, division of attention, and situational awareness. The maneuvers themselves are not evaluated during the practical test, but the skills developed by accomplishing them are evaluated during the conduct of other tasks. By performing ground reference maneuvers, a student develops a better understanding of the effects of wind drift and how to compensate for winds from different directions during flight. Rectangular Course The rectangular course helps the student develop recognition of drift toward or away from a line parallel to the intended ground track. [Figure 10-13] It is important that he or she understand the effects of the wind and how to compensate for it. The rectangular course also simulates an airport traffic pattern, as well as many of the maneuvers a helicopter is tasked with performing, such as tracking an event for photographic purposes, aerial surveys, and observation duties. This is an opportunity to point out to the student what each segment of a traffic pattern represents (upwind, crosswind, downwind, base, and final leg). For this maneuver, pick a square or rectangular field, or an area bounded on four sides by section lines or roads, where the sides are approximately a mile in length. The area selected should be well away from other air traffic. Fly the maneuver between 500' and 800' feet AGL, which is the altitude normally required for an airport traffic pattern to avoid the flow of fixed wing traffic. If the student finds it difficult to maintain a proper ground track at that higher altitude, adjust the altitude for better ground reference until the student feels more comfortable and is able to grasp the concept better. The helicopter should be flown parallel to and at a uniform distance from the field boundaries, not above the boundaries. Demonstrate that by flying directly above the edges of the field, there are no usable reference points to start and complete the turns. In addition, the closer the track of the helicopter is to the field boundaries, the steeper the bank necessary at the turning points. The student should understand that when trying to fly a straight line and maintain a specific heading, the helicopter should always be kept in trim with the antitorque pedals and the pilot should crab into the wind (with the cyclic) to stay on the proper ground track. The concept of “crabbing” can be difficult for the student to understand when first learning how to fly a traffic pattern. The instructor should show the student what happens when you try to fly a straight line with a crosswind, and point out how far off course the wind can take you. Keeping the helicopter in trim and keeping the helicopter straight are done with two different flight controls, and the instructor should ensure the student understands the effects of crabbing to allow for wind drift. Since the helicopter is not headed exactly parallel to the rectangle course, turns at the corners of the rectangle may be more or less than 90 degrees with a shallower or steeper bank angle to hold the correct distance from the rectangle. The rectangular course requires the student to adjust for winds from each quadrant. Also ensure that the cyclic trim (if installed) is properly trimmed in order to decrease the pressures on the pilot. |
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