Figure 25-2: Single Angle
Figure 25-3: Double Angle
Figure 25-4: Vertical approach
Make your approach to a hover over the ground that you have determined as being suitable for a landing. It would not be prudent to come to a hover over obstacles, or to be in a position where such obstacles might make it hazardous to manoeuvre the helicopter.
5. Manoeuvring in the zone. Often you may find that it is necessary to manoeuvre the helicopter inside the confined area, perhaps to move to a more suitable landing spot or to reposition in preparation for departure. Many confined area accidents occur during this manoeuvring and particular attention must be paid to any obstacles that may snag a skid or strike the tail rotor. For this reason, all turns are normally done around the tail, generally to the pilot’s side.
6. The Departure. In preparation for the departure, manoeuvre the helicopter into a position as far as possible from the obstacles on the take-off path to take advantage of all available space. Look out all around as other aircraft may be in the same area.
7. The Aborted Departure. There may be situations where you have to discontinue the take-off and return to a landing within the confined area. This aborted departure is a critical manoeuvre that requires skill and care if it is to be performed safely and effectively.
The earlier in the departure that you make a decision to abort, the easier it will be to recover and return the helicopter to a landing or a hover.
Confined area training begins in relatively large areas that allows for normal approaches and departures, and also allows manoeuvring of the helicopter within the area. Once comfortable in this environment, you will advance to more restricted sites that require steeper approaches, and their size limit your ability to manoeuvre the helicopter. Out of wind approaches are practised, as the shape of the area or the surrounding obstacles often demands them.
NOTE: There is a great need to exercise your common sense in this exercise. The easiest way is normally the best way generally holds true for confined area work.
EXERCISE 26 - VORTEX RING
If the helicopter pilot chooses a flight path, airspeed and a rate of descent that coincides with the aircraft’s downwash, the helicopter could enter a condition known as the Vortex Ring state. The stall condition formed by the rate of descent flow in opposition to the induced flow, combines with the tip vortices present in all regimes of flight to produce a turbulent rotational flow on the blades and an unsteady spanwise shifting of that flow. This condition induces a very rapid rate of descent, vibrations, excessive flapping and a reduction in cyclic authority that could result in an accident. Obviously, this condition is to be avoided and the helicopter pilot should be able to recognize the incipient stage and be able to affect a safe recovery.
Your instructor will review the causes, conditions and symptoms of vortex ring. During a steep approach, at a high gross weight, high-density altitude and in a downwind or light wind condition; the helicopter may enter its own downwash and the development of vortex ring state. This situation would certainly contribute to the onset of vortex ring, but not necessarily cause it. The phenomenon is most likely to occur when all the conditions listed below are present:
中國(guó)航空網(wǎng) www.k6050.com
航空翻譯 www.aviation.cn
本文鏈接地址：直升機(jī)飛行訓(xùn)練手冊(cè) HELICOPTER FLIGHT TRAINING MANUAL(51)
