直升机飞行训练手册 HELICOPTER FLIGHT TRAINING MANUAL(31)

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To commence this manoeuvre, look first in the direction that you intend to turn, ensuring that  the area is clear of obstacles that could pose a hazard to the helicopter. While doing this, try to imagine that the cockpit of your helicopter is sitting astride the circumference of a circle with the tail of the helicopter at the centre of that circle. Unlike a turn around the mast, where in still wind the turn can be completed with pedal alone, you must now co-ordinate both the pedals and the cyclic to move the helicopter around the imaginary circle. Use the pedals to keep the tail over the centre while maintaining a slow walking pace laterally with the cyclic. Collective is used to maintain the normal hover height. Be aware that in any wind conditions the cyclic must be displaced into the wind.
TURNS AROUND THE NOSE
(Fig 16-3) This variation on the hovering-turn, you will also find extremely useful in the operational sense. To practice the manoeuvre, identify a spot on the ground close to nose of the helicopter; 10 to 15 feet will suffice. Avoid selecting a spot close in, as you will find, as in basic hovering, that it will be difficult to accurately control your height. Look in the direction you intend to move the helicopter to ensure the entire area is free of obstacles. The manoeuvre itself is similar to the turn around the tail, except the tail now sits astride the circumference of the imaginary circle.
Use the pedals to keep the nose pointed at the selected spot while effecting lateral movement with the cyclic. Maintain the correct hover height with the collective. Keep the movement slow and smooth as rushing turning manoeuvres will result in overcontrolling and you may exceed manufacturer’s limitations.

 
Figure 16-3: Turn around the nose
 
EXERCISE 17 - STEEP TURNS
Steep turns are a means of turning the helicopter in a relatively small area. The practice of these manoeuvres is excellent in developing the coordination of all three flight controls and the power control. It is important that you acquire the ability to execute them accurately and smoothly. Your instructor will demonstrate them in different operational flying situations. 
Up to a limited angle of bank a steep turn may be executed without increasing power. However, in order to maintain a constant altitude, the airspeed must be sacrificed as a result of the increased aft cyclic pressure required to maintain that altitude. Remember that the greater is the angle of bank, the greater the amount of lift is required to maintain a constant altitude, therefore, additional lift is provided by an increase of power.
A steep turn is entered like any other turn but, as the angle of bank is increased beyond approximately 30°, you must increase collective in order to maintain height and airspeed.  It requires simultaneous co-ordination of all three controls. Because of the rapid change  of direction, the lookout for other aircraft before doing a steep turn is even more important than for other turns.
To enter a steep turn, first look out, then apply lateral cyclic in the direction of the desired turn and:
1. as the bank increases, move the cyclic aft to maintain the correct fuselage attitude relative to the horizon. (By so doing you have increased the aft tilt of the disc which, unless compensated for, will cause the airspeed to decrease);
2. to maintain the set airspeed, increase collective as necessary as the bank angle increases beyond 30°;
3. once the desired bank angle has been achieved, keep it constant with lateral cyclic.
4. maintain balanced flight (ball centred) throughout the manoeuvre with tail rotor pedals; and
5. maintain a good lookout.
To recover from a steep turn, proceed exactly as you would for any other turn, except that,  as you roll off the bank, the collective should be reduced simultaneously with the return to straight and level flight. You must also relax cyclic backpressure to ensure that the helicopter does not climb as you roll out of the turn. Remember that these movements should be coordinated and smooth.
　
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