直升机飞行手册 Helicopter Flying Handbook

时间：2014-11-09 12:30来源：FAA 作者：直升机翻译 点击：次

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6. Failing to level the helicopter or achieve the manufacturers preferred landing attitude.
7. Failure to maintain ground track in the air and keeping the landing gear aligned with the direction of travel during touchdown and ground contact.
8. Failure to minimize or eliminate lateral movement during ground contact.
9. Failure to go around if not within limits and specified criteria for safe autorotation.
Autorotation With Turns
A turn, or a series of turns, can be made during an autorotation in order to land into the wind or avoid obstacles. The turn is usually made early so that the remainder of the autorotation is the same as a straight-in autorotation. Making turns during an autorotation generally uses cyclic control only. Use of antitorque pedals to assist or increase the speed of the turn causes loss of airspeed and downward pitching of the nose. When an autorotation is initiated, sufficient antitorque pedal pressure should be used to maintain the helicopter in trim and prevent yawing. This pressure should not be changed to assist the turn. If the helicopter is flown out of trim in forward flight, the helicopter will be in either a slip or a skid and airframe drag will be greatly increased which in turn increases the rate of descent. Therefore, for the minimum descent vertical speed, the trim ball should remain centered.
Use collective pitch control to manage rotor rpm. If rotor rpm builds too high during an autorotation, raise the collective sufficiently to decrease rpm back to the normal operating range, then reduce the collective to maintain proper rotor rpm. If the collective increase is held too long, the rotor rpm may decay rapidly. The pilot must then lower the collective and begin chasing the rotor rpm. If the rpm begins decreasing, the pilot must again lower the collective. Always keep the rotor rpm within the established range for the helicopter being flown. During a turn, rotor rpm increases due to the increased G loading, which induces a greater airflow through the rotor system. The rpm builds rapidly and can easily exceed the maximum limit if not controlled by use of collective. The tighter the turn is and the heavier the gross weight is, the higher the rpm is.
Cyclic input has a great effect on the rotor rpm. An aft cyclic input loads the rotor, resulting in coning and an increase in rotor rpm. A forward cyclic input unloads the rotor, resulting in a decrease in rotor rpm. Therefore, it is prudent to attain the proper pitch attitude needed to ensure that the desired landing area can be reached as soon as possible, and to make minor adjustments from there.
To initiate an autorotation in other than in a low hover, lower the collective pitch control. This holds true whether performing a practice autorotation or in the event of an in-flight engine failure. This reduces the pitch of the main rotor blades and allows them to continue turning at normal rpm. During practice autorotations, maintain the rpm in the green arc with the throttle while lowering collective. Once the collective is fully lowered, reduce engine rpm by decreasing the throttle. This causes a split of the engine and rotor rpm needles.
Technique
The most common types of autorotation are 90° and 180° autorotations. For a 180° autorotation, establish the aircraft on the downwind at recommended airspeed and 500–700 feet AGL, parallel to the touchdown area. In a no-wind or headwind condition, establish the ground track approximately 200 feet away from the touchdown point. If a strong crosswind exists, it is necessary to move the downwind leg closer or farther out. When abeam the intended touchdown point, smoothly but firmly lower the collective pitch control to the full down position, maintaining rotor rpm in the green arc with collective.
Coordinate the collective movement with proper antitorque pedal for trim, and apply cyclic control to maintain proper attitude. Once the collective is fully lowered, decrease throttle to ensure a clean split/separation of the needles. After splitting the needles, readjust the throttle to keep engine rpm above normal idling speed, but not high enough to cause rejoining of the needles. The manufacturer often recommends the proper rpm for that particular helicopter. Crosscheck attitude, trim, rotor rpm, and airspeed.

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